U.S. patent application number 14/494747 was filed with the patent office on 2015-01-08 for gas separation membrane module and method for gas separation.
The applicant listed for this patent is Ube Industries, Ltd.. Invention is credited to Nobuhiko FUKUDA, Yutaka KANETSUKI, Tomohide NAKAMURA, Nozomu TANIHARA.
Application Number | 20150007729 14/494747 |
Document ID | / |
Family ID | 47260684 |
Filed Date | 2015-01-08 |
United States Patent
Application |
20150007729 |
Kind Code |
A1 |
KANETSUKI; Yutaka ; et
al. |
January 8, 2015 |
GAS SEPARATION MEMBRANE MODULE AND METHOD FOR GAS SEPARATION
Abstract
A process for producing nitrogen-rich air by feeding high
temperature air at 150.degree. C. or more to an air separation
membrane module is described. After being placed at 175.degree. C.
for two hours, the air separation module exhibits a shape-retention
ratio of 95% or more in one embodiment. The nitrogen-rich air can
be fed to a fuel tank for an aircraft, for example.
Inventors: |
KANETSUKI; Yutaka; (Ube-shi,
JP) ; FUKUDA; Nobuhiko; (Ube-shi, JP) ;
TANIHARA; Nozomu; (Ube-shi, JP) ; NAKAMURA;
Tomohide; (Ube-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ube Industries, Ltd. |
Ube-shi |
|
JP |
|
|
Family ID: |
47260684 |
Appl. No.: |
14/494747 |
Filed: |
September 24, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13288095 |
Nov 3, 2011 |
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14494747 |
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Current U.S.
Class: |
96/8 |
Current CPC
Class: |
B01D 53/22 20130101;
B01D 53/228 20130101; B01D 2313/02 20130101; B01D 69/02 20130101;
B01D 2325/32 20130101; B01D 2311/13 20130101; B01D 63/02 20130101;
B01D 2053/224 20130101; B01D 2313/04 20130101; B01D 2325/20
20130101; B01D 2313/21 20130101; B01D 2256/10 20130101; B01D
2313/20 20130101; B01D 63/023 20130101; B01D 2319/04 20130101; B01D
71/64 20130101; B01D 2257/104 20130101 |
Class at
Publication: |
96/8 |
International
Class: |
B01D 53/22 20060101
B01D053/22; B01D 63/02 20060101 B01D063/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 4, 2010 |
JP |
2010-247779 |
Nov 4, 2010 |
JP |
2010-247931 |
Dec 9, 2010 |
JP |
2010-274619 |
May 31, 2011 |
JP |
2011-122285 |
Sep 22, 2011 |
JP |
2011-207538 |
Sep 22, 2011 |
JP |
2011-207647 |
Oct 14, 2011 |
JP |
2011-227101 |
Oct 31, 2011 |
JP |
2011-239388 |
Claims
1. (canceled)
2. A separation membrane module used under high-temperature
conditions, comprising: a hollow fiber bundle including a number of
hollow fiber membranes with selective permeability; a cylindrical
vessel housing the hollow fiber bundle; a tube sheet placed at the
end of the hollow fiber bundle, said tube sheet fixes the end of
the bundle to the end of the cylindrical vessel and separates the
inside of the cylindrical vessel from the outside; and an annular
sealing member for sealing between the outer surface of the tube
sheet and the inner surface of the cylindrical vessel; wherein the
tube sheet does not comprise a stepped portion at its periphery on
which the annular sealing member is to be mounted.
3. A separation membrane module used under high-temperature
conditions, comprising: a hollow fiber bundle including a number of
hollow fiber membranes with selective permeability; a cylindrical
vessel housing the hollow fiber bundle; and a tube sheet placed at
the end of the hollow fiber bundle, said tube sheet fixes the end
of the bundle to the end of the cylindrical vessel and separates
the inside of the cylindrical vessel from the outside; wherein (i)
the tube sheet is made of material having a larger thermal
expansion coefficient than that of material for the cylindrical
vessel, and wherein (ii) there is a gap between the outer surface
of the tube sheet and the inner surface of the cylindrical vessel
at normal temperature, whereas the tube sheet can expand by heating
to a predetermined temperature, so that its outer surface adheres
tightly to the inner surface of the cylindrical vessel to provide
sealing effect.
4. A gas separation membrane module, comprising: a hollow fiber
bundle including a number of hollow fiber membranes with selective
permeability; a cylindrical vessel housing the hollow fiber bundle;
a tube sheet placed at the end of the hollow fiber bundle, said
tube sheet fixes the end of the bundle to the end of the
cylindrical vessel and separates the inside of the cylindrical
vessel from the outside; a cap at the end of the cylindrical
vessel; and a tubular member for forming a channel communicating
the inside with the outside of the cylindrical vessel, said tubular
member penetrating both a part of the cylindrical vessel and a part
of the cap along radial direction.
5. The gas separation membrane module of claim 4, comprising a
fixing member to be inserted into a part of the peripheral wall of
the cap, to fix the cap and the cylindrical vessel each other.
6. A gas separation membrane module, comprising: a hollow fiber
bundle including a number of hollow fiber membranes with selective
permeability; a cylindrical vessel housing the hollow fiber bundle;
a tube sheet placed at the end of the hollow fiber bundle, said
tube sheet fixes the end of the bundle to the end of the
cylindrical vessel and separates the inside of the cylindrical
vessel from the outside; a cap at the end of the cylindrical
vessel; and a fixing member to be inserted into a part of the
peripheral wall of the cap, to fix the cap and the cylindrical
vessel each other.
7. A gas separation membrane module, comprising: a hollow fiber
bundle including a number of hollow fiber membranes with selective
permeability; a cylindrical vessel housing the hollow fiber bundle;
a tube sheet placed at the end of the hollow fiber bundle, said
tube sheet fixes the end of the bundle to the end of the
cylindrical vessel and separates the inside of the cylindrical
vessel from the outside; a cap at the end of the cylindrical
vessel; and an annular sealing member for sealing between the outer
surface of the tube sheet and the inner surface of the cylindrical
vessel; wherein the cap is fixed to the cylindrical vessel by (i)
using a thread formed in a part of the inner surface of the cap and
a thread formed in an opposite part of the outer surface of the
cylindrical vessel, or (ii) using a binder for binding a flange of
the cap and a corresponding flange of the cylindrical vessel.
8. The gas separation membrane module of claim 7, wherein the
annular sealing member further seals between the cap and the
cylindrical vessel.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Japanese Patent
Application Nos. 2010-247779, filed Nov. 4, 2010; 2010-247931,
filed Nov. 4, 2010; 2010-274619, filed Dec. 9, 2010, 2011-122285,
filed May 31, 2011; 2011-207538, filed Sep. 22, 2011; 2011-207647,
filed Sep. 22, 2011; 2011-227101, filed Oct. 14, 2011; and
2011-239388, filed Oct. 31, 2011.
TECHNICAL FIELD
[0002] The present invention relates to a gas separation membrane
module and a gas separation method for separating gases using a
number of hollow fiber membranes with selective permeability.
BACKGROUND ART
[0003] A separation membrane module using a separation membrane
with selective permeability for gas separation (for example,
separation of oxygen, nitrogen, hydrogen, water vapor, carbon
dioxide, organic vapor or the like) can be of plate and frame type,
of tubular type, of hollow fiber type or the like. Among these, a
hollow-fiber type gas separation membrane module is industrially
excellent because it is not only advantageous in its largest
membrane area per a unit volume but also superior in pressure
resistance and self-supporting ability, and thus has been
extensively used.
SUMMARY OF INVENTION
[0004] The present inventions will be detailed in sections A to G
below and include a combination of two or more inventions described
in the sections. The background and the problems for the inventions
disclosed in each section will be described in each section.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 shows the measurement results for Example 1 and
Comparative Example 2 in section A.
[0006] FIG. 2 shows the measurement results for Examples 1 and 2 in
section A.
[0007] FIG. 3 schematically shows an example of a gas separation
membrane module.
[0008] FIG. 4 schematically shows a process for manufacturing a
tube sheet of a membrane module for separating a mixture of
gasses.
[0009] FIG. 5 is a cross-sectional view schematically showing a
basic configuration of a separation membrane module of the first
embodiment in section C.
[0010] FIG. 6(a) shows an exemplary structure of a module end and
FIG. 6(b) shows a conventional structure.
[0011] FIG. 7 is a view of another structure near the tube
sheet.
[0012] FIG. 8 shows an exemplary structure of a module end
according to the second embodiment in section C; FIGS. 8(a) and
8(b) show the states at normal temperature and an elevated
temperature, respectively.
[0013] FIG. 9 shows an exemplary structure of a module end
according to the third embodiment in section C.
[0014] FIG. 10 is a view of another exemplary embodiment.
[0015] FIG. 11(a) is a cross-sectional view showing a further
exemplary separation membrane module, and FIG. 11(b) is an enlarged
partial view of FIG. 11(a).
[0016] FIG. 12 is a view showing an exemplary arrangement of the
0-RING.
[0017] FIG. 13 is a cross-sectional view of a gas separation
membrane module according to one embodiment in section D.
[0018] FIG. 14 is a cross-sectional view of the tubular member in
the module in FIG. 13.
[0019] FIG. 15 shows a plan view and a sectional side view of a
capping member in the module in FIG. 13, FIG. 15(A) is a
cross-sectional view taken on line X-X of FIG. 15(B).
[0020] FIG. 16 is a schematic view of a capping member for
illustrating an example in which the number of fixing rods has been
changed.
[0021] FIG. 17 is a cross-sectional view schematically showing a
basic configuration of a gas separation membrane module according
to one embodiment in section E.
[0022] FIG. 18 is an enlarged partial view of FIG. 17.
[0023] FIG. 19 is a cross-sectional view showing an exemplary
casing in the module in FIG. 17.
[0024] FIG. 20 is a cross-sectional view schematically illustrating
a basic configuration of a gas separation membrane module according
to one embodiment in section F.
[0025] FIG. 21(A) is an enlarged partial view of FIG. 20 and FIG.
21(B) is an enlarged view further showing a part of the figure.
[0026] FIG. 22(A) is a cross-sectional view showing a gas
separation membrane module according to another embodiment and FIG.
22(B) is an enlarged partial view.
[0027] FIG. 23 is a cross-sectional view showing a gas separation
membrane module according to a further embodiment.
[0028] FIG. 24 is a cross-sectional view showing a gas separation
membrane module according to another embodiment.
[0029] FIG. 25 is a cross-sectional view schematically showing a
basic configuration of a gas separation membrane module according
to one embodiment in section G.
[0030] FIG. 26 is an enlarged partial view of FIG. 25.
[0031] FIG. 27 is a cross-sectional view taken on line A-A of FIG.
26.
DETAILED DESCRIPTION
[0032] There will be described embodiments of the present
inventions in sections A to G.
Section A: A Process for Producing Nitrogen-Rich Air from High
Temperature Gas
Background Art
[0033] Some aircrafts use an on-board inert-gas generating system
(OBIGGS) as one of methods for protecting against explosion of a
fuel tank. An oxygen concentration of a gas-phase region in a fuel
tank should be lower than a given concentration for avoiding risk
of explosion. Thus, an OBIGGS separates oxygen from the air to
generate nitrogen-rich air containing nitrogen in a higher level,
which is then fed to a fuel tank.
[0034] An OBIGGS generates nitrogen-rich air using, for example, an
air separation membrane module. Since a treated amount of an air
separation membrane generally increases at a higher pressure and a
higher temperature of a feed gas, an extracted gas from an engine,
an ambient air or the like is compressed by, for example, a
compressor and then fed to an air separation membrane module. The
compressed gas is generally heated to 149 to 260.degree. C.
[0035] A conventional air separation membrane module efficiently
operates at a temperature of about 82.degree. C. to about
93.degree. C. It cannot be, therefore, used at a high temperature
as described above due to significant deterioration in separation
performance. Therefore, a compressed gas is generally cooled to the
above temperature range by using a heat exchanger or mixing the gas
with a cool air and then fed to an air separation membrane module
(see Japanese laid-open patent publication No. 2010-142801).
Problems to be Solved by the Invention in Section A
[0036] An objective of the invention in section A is to provide a
process for producing nitrogen-rich air by feeding a compressed air
at 150.degree. C. or higher to an air separation membrane
module.
[0037] The summary of the main invention disclosed in this section
is as follows.
[0038] [1] A process for producing nitrogen-rich air from the air
using an air separation membrane module, comprising feeding the air
at 150.degree. C. or higher to an air separation membrane
module.
Effect of the Invention in Section A
[0039] According to a process of the invention in section A, a
nitrogen-rich air containing a higher concentration of nitrogen can
be produced by feeding the air at a high temperature, for example,
150.degree. C. or higher to an air separation membrane module. The
invention of this section is characterized in the use of an air
separation membrane with a higher oxygen-gas permeation rate and
higher selectivity of oxygen and nitrogen at a high temperature,
which can maintain its performance even after a long period of use
at a high temperature. The invention of this section is suitable
for, for example, an explosion-proof system for a fuel tank in an
aircraft. The use of the invention of this section in the
explosion-proof system allows for weight reduction of, for example,
a heat exchanger for cooling a hot air during feeding the air to an
air separation membrane module. Furthermore, a permeation rate of
an air separation membrane becomes higher as a temperature of a
feed air is higher, and therefore, the process of the invention of
this section, which can treat a high temperature air, can be
efficient with a smaller membrane area. Thus, equipments in an
aircraft can be simplified and be made lighter.
Embodiments in Section A
[0040] The invention disclosed in this section is a process for
producing nitrogen-rich air from the air using an air separation
membrane module, comprising feeding the air at a high temperature
of 150.degree. C. or higher to the air separation membrane module.
Unless otherwise indicated, the term "high temperature" as used
herein means a temperature of 150.degree. C. or higher, preferably
175.degree. C. or higher, more preferably 200.degree. C. or
higher.
[0041] An air separation membrane module can be produced by, for
example, bundling 100 to 1,000,000 hollow fiber membranes with a
proper length, fixing both ends of the hollow fiber bundle by a
tube sheet made of, for example, a thermosetting resin keeping at
least one end of the hollow fiber open, and mounting a resulting
hollow fiber membrane element comprising the hollow fiber bundle
and the tube sheet in a vessel equipped with at least an air inlet,
a permeate gas outlet and a non-permeate gas outlet in such a way
that the space leading to the inside of the hollow fiber membranes
and the space leading to the outside of the hollow fiber membranes
are isolated each other. In such an air separation membrane module,
gas separation is performed by feeding the air to the space leading
to the inside or the outside of the hollow fiber membranes from the
air inlet and flowing in contact with the hollow fiber membranes
while oxygen in the air selectively permeates the membrane so that
a permeate gas (oxygen-rich air) and non-permeate gas
(nitrogen-rich air) are discharged from the permeate gas outlet and
the non-permeate gas outlet, respectively.
[0042] An example of an air separation membrane is, but not limited
to, an asymmetric air separation membrane which has an asymmetric
structure consisting of a very thin dense layer (preferably
thickness: 0.001 to 5 .mu.m) mainly responsible for air separation
performance and a relatively thicker porous layer (preferably
thickness: 10 to 2000 .mu.m) supporting the dense layer. It is
preferably a hollow fiber membrane having an inner diameter of
about 10 to 3000 .mu.m and an outer diameter of about 30 to 7000
.mu.m.
[0043] The air separation membrane preferably has the following
properties at a high temperature.
[0044] An air separation membrane preferably has a high oxygen-gas
permeation rate at a high temperature. For example, it has an
oxygen permeation rate (P'.sub.O2) of 20.times.10.sup.-5
cm.sup.3(STP)/cm.sup.2seccmHg or more, preferably
25.times.10.sup.-5 cm.sup.3(STP)/cm.sup.2seccmHg or more, more
preferably 30.times.10.sup.-5 cm.sup.3(STP)/cm.sup.2seccmHg or more
at 175.degree. C. Furthermore, an air separation membrane
preferably exhibits high separation performance even at a high
temperature; for example, a ratio of an oxygen-gas permeation rate
to a nitrogen-gas permeation rate (P'.sub.O2/P'.sub.N2) as an index
of separation performance of a membrane is for example 1.8 or more,
preferably 2.0 or more, more preferably 2.5 or more at 175.degree.
C. A ratio of permeation rates is generally larger at a lower
temperature. A higher ratio of permeation rates, that is, higher
separation performance leads to a higher recovery ratio of desired
nitrogen-rich air.
[0045] Furthermore, it is preferable that in an air separation
membrane, an oxygen-gas permeation rate or separation performance
of the membrane is not reduced very much even after a long period
of use at a high temperature. For example, after the use at
175.degree. C. for 140 hours, an oxygen permeation rate (P'.sub.O2)
and a ratio of an oxygen-gas permeation rate to a nitrogen-gas
permeation rate (P'.sub.O2/P'.sub.N2) are preferably 75% or more,
more preferably 80% or more, further preferably 90% or more, to
P'.sub.O2 and P'.sub.O2/P'.sub.N2 before use, respectively.
[0046] Furthermore, an air separation membrane preferably retains
its shape even at a high temperature as much as its functions are
not deteriorated. For example, it is preferable that a material
constituting an air separation membrane has a glass-transition
temperature (Tg) of preferably 225.degree. C. or higher (that is,
not less than 225.degree. C.), more preferably 250.degree. C. or
more, further preferably 300.degree. C. or more (including a
material whose glass-transition temperature cannot be determined).
Furthermore, it preferably retains its shape at a high temperature
for a long period; a shape retention ratio is preferably 95% or
more, more preferably 99% or more after being placed at 175.degree.
C. for 2 hours. Here, a shape retention ratio in this section is
calculated by dividing a length of a fiber after heating at
175.degree. C. for 2 hours by an initial length before heating, and
converting the value to percentage.
[0047] Examples of a material having a glass-transition temperature
of higher than 225.degree. C., which is suitable for a separation
membrane, include polyimides, polyether sulfones, polyamides and
polyether ether ketones, particularly preferably, polyimides.
[0048] As a non-limiting material for an asymmetric gas separation
hollow fiber membrane (hereinafter, sometimes simply referred to as
a hollow fiber membrane), an exemplary composition of a polyimide
will be described, which is suitable for an air separation membrane
and has a glass-transition temperature of higher than 225.degree.
C. A polyimide having a composition described below is an aromatic
polyimide having a repeating unit represented by general formula
(1) and has a glass-transition temperature of generally 250.degree.
C. or higher, preferably 300.degree. C. or higher (including a
material whose glass-transition temperature cannot be
determined).
##STR00001##
[0049] In this formula, B is a tetravalent unit derived from a
tetracarboxylic acid component, and A is a divalent unit derived
from a diamine component. The units constituting the aromatic
polyimide will be detailed below.
[0050] Unit B is a tetravalent unit derived from a tetracarboxylic
acid component, which comprises 10 to 70 mol %, preferably 20 to 60
mol % of unit B1 having a diphenylhexafluoropropane structure
represented by general formula (B1) described below, and 90 to 30
mol %, preferably 80 to 40 mol % of unit B2 having a biphenyl
structure represented by general formula (B2) described below, and
it is preferably substantially comprised of unit B1 and unit B2. If
the diphenylhexafluoropropane structure is less than 10 mol % and
the biphenyl structure is more than 90 mol %, gas separation
performance of a polyimide obtained is so deteriorated that a high
performance gas separation membrane cannot be obtained. If the
diphenylhexafluoropropane structure is more than 70 mol % and the
biphenyl structure is less than 30 mol %, mechanical strength of a
polyimide obtained may be deteriorated.
[0051] Unit B can comprise a tetravalent unit based on a phenyl
structure represented by general formula (B3). The tetravalent unit
based on the phenyl structure represented by general formula (B3)
is suitably comprised in 0 to 30 mol %, preferably 10 to 20 mol
%.
[0052] Furthermore, unit B can comprise a tetravalent unit B4
derived from another tetracarboxylic acid other than units B1, B2
and B3.
##STR00002##
[0053] Unit A is a divalent unit derived from a diamine component,
and comprises unit A1 selected from the group consisting of general
formulas (A1a), (A1b) and (A1c) and unit A2 selected from the group
consisting of general formulas (A2a) and (A2b). Furthermore, unit A
can comprise a divalent unit A3 derived from another diamine
component other than units A1 and A2.
[0054] Unit A1a is a divalent unit based on a biphenyl structure
represented by Formula (A1a), and unit A1b and A1c comprise
hexafluorinated structures represented by Formulas (A1b) and (A1c),
respectively, more specifically a unit having a structure
comprising two trifluoromethyl groups.
##STR00003##
[0055] wherein X is chlorine or bromine, and n is 1 to 3.
##STR00004##
[0056] wherein r is 0 or 1, and the phenyl rings can be substituted
by OH group.
##STR00005##
[0057] wherein Y represents O or a single bond.
[0058] When unit A1 comprises the unit represented by Formula
(A1a), it is suitably comprised in 30 to 70 mol %, preferably 30 to
60 mol % in unit A. The benzidines contribute to improvement
permselectivity. If the amount thereof is too much, a resulting
polymer becomes insoluble and it is difficult to form a membrane,
while if the amount is too low, a permselectivity is
disadvantageously reduced.
[0059] When unit A1 contains the units represented by Formulas
(A1b) and/or (A1c), these are comprised in 10 to 50 mol %,
preferably 20 to 40 mol % in unit A.
[0060] Unit A2 is a sulfur-containing heterocyclic structure,
specifically selected from the units represented by general
formulas (A2a) and (A2b).
##STR00006##
[0061] wherein R and R' are hydrogen or an organic group, and n is
0, 1 or 2.
##STR00007##
[0062] wherein R and R are hydrogen or an organic group, and X is
--CH.sub.2-- or --CO--.
[0063] Unit A2 is comprised in 90 to 30 mol %, preferably 90 to 40
mol %, more preferably 90 to 50 mol %, further preferably 80 to 60
mol % in unit A.
[0064] Unit A3 can be comprised in 50 mol % or less, preferably 40
mol % or less, more preferably 20 mol % or less in unit A.
[0065] There will be described a monomer component constituting
each of the above units in an aromatic polyimide.
[0066] The unit having the diphenylhexafluoropropane structure
represented by general formula (B1) can be prepared using a
(hexafluoroisopropylidene)diphthalic acid, its dianhydride or its
ester as a tetracarboxylic acid component. The
(hexafluoroisopropylidene)diphthalic acids can be suitably selected
from 4,4'-(hexafluoroisopropylidene)diphthalic acid,
3,3'-(hexafluoroisopropylidene)diphthalic acid,
3,4'-(hexafluoroisopropylidene)diphthalic acid, their dianhydrides
and their esters, particularly suitably
4,4'-(hexafiuoroisopropylidene)diphthalic acid, its dianhydride and
its ester.
[0067] The unit having the biphenyl structure represented by
general formula (B2) can be prepared by using
biphenyltetracarboxylic acids such as biphenyltetracarboxylic acid,
its dianhydride and its ester as a tetracarboxylic acid component.
The biphenyltetracarboxylic acids can be suitably selected from
3,3',4,4'-biphenyltetracarboxylic acid,
2,3,3',4'-biphenyltetracarboxylic acid,
2,2',3,3'-biphenyltetracarboxylic acid, their dianhydrides and
their esters, particularly suitably
3,3',4,4'-biphenyltetracarboxylic acid, its dianhydride and its
ester.
[0068] The tetravalent unit based on a phenyl structure represented
by general formula (B3) can be formed by using pyromellitic acids
such as pyromellitic acid and its anhydride. The pyromellitic acids
are suitable for improving mechanical properties. If its amount is
excessive, it is difficult to form a hollow fiber membrane because
a polymer solution becomes unstable, for example, it is coagulated
during membrane formation.
[0069] Another tetracarboxylic acid component giving unit B4 is a
tetracarboxylic acid other than those described above, and can be
selected from those which can sometimes further improve performance
without deteriorating the effects of the invention in this section.
Examples can include diphenyl ether tetracarboxylic acids,
benzophenone tetracarboxylic acids, diphenylsulfonetetracarboxylic
acids, naphthalene tetracarboxylic acids, diphenyl
methanetetracarboxylic acids and diphenylpropane tetracarboxylic
acids.
[0070] The divalent unit based on the biphenyl structure
represented by general formula (A1a) can be formed by using
halogenated benzidines represented by general formula (A1a-M) as a
diamine component.
##STR00008##
[0071] wherein X is chlorine or bromine, and n=1 to 3.
[0072] Examples of halogenated benzidines include
dichlorobenzidines (diaminodichlorobiphenyls),
tetrachlorobenzidines (diaminotetrachlorobiphenyls),
hexachlorobenzidines, tetrabromobenzidines, dibromobenzidines and
hexabromobenzidines. An example of dichlorobenzidines can include
3,3'-dichlorobenzidine (DCB) and an example of
tetrachlorobenzidines can include 2,2',5,5'-tetrachlorobenzidine
(TCB).
[0073] The divalent unit represented by general formula (A1b) is
formed by using a hexafluorinated compound represented by general
formula (A1b-M) as a diamine component.
##STR00009##
[0074] wherein r is 0 or 1, and the phenyl rings may be substituted
by OH group.
[0075] A preferable hexafluorinated compound represented by (A1b-M)
is represented by any of general formulas (A1b-M1) to (A1b-M3).
##STR00010##
[0076] The bis[(aminophenoxy)phenyl]hexafluoropropanes represented
by general formula (A1b-M1) can include for example,
2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane or 2,2-bis[4-(3
aminophenoxy)phenyl]hexafluoropropane. The
bis(aminophenyl)hexafluoropropanes represented by general formula
(A1b-M2) can include, for example,
2,2-bis(4-aminophenyl)hexafluoropropane. The hydroxylated
bis(aminophenyl)hexafluoropropanes represented by general formula
(A1b-M3) can include, for example,
2,2-bis(3-amino-4-hydroxy)hexafluoropropane.
[0077] The divalent unit represented by general formula (A1c) can
be prepared by using a hexafluorinated compound represented by
general formula (A1c-M) as a diamine component.
##STR00011##
[0078] wherein Y represents O or a single bond.
[0079] The diamine compounds represented by general formula (A1c-M)
can include, for example,
2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether and
2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl.
[0080] The unit having a structure represented by general formula
(A2a) or (A2b) can be prepared by using an aromatic diamine
represented by general formula (A2a-M) or (A2b-M), respectively, as
a diamine component.
##STR00012##
[0081] wherein R and R' are hydrogen or an organic group, and n is
0, 1 or 2.
##STR00013##
[0082] wherein R and R' are hydrogen or an organic group, and X is
--CH.sub.2-- or --CO--.
[0083] The aromatic diamine represented by general formula (A2a-M)
can include suitably the diaminodibenzothiophenes represented by
general formula (A2a-M1), that is, general formula (A2a-M) in which
n is 0, or the diaminodibenzothiophene=5,5-dioxides represented by
general formula (A2a-M2), that is, general formula (A2a-M) in which
n is 2.
##STR00014##
[0084] wherein R and if are hydrogen or an organic group.
##STR00015##
[0085] wherein R and W is hydrogen or an organic group.
[0086] The diaminodibenzothiophenes (general formula (A2a-M1)) can
include, for example, 3,7-diamino-2,8-dimethyldibenzothiophene,
3,7-diamino-2,6-dimethyldibenzothiophene,
3,7-diamino-4,6-dimethyldibenzothiophene,
2,8-diamino-3,7-dimethyldibenzothiophene,
3,7-diamino-2,8-diethyldibenzothiophene,
3,7-diamino-2,6-diethyldibenzothiophene,
3,7-diamino-4,6-diethyldibenzothiophene,
3,7-diamino-2,8-dipropyldibenzothiophene,
3,7-diamino-2,6-dipropyldibenzothiophene,
3,7-diamino-4,6-dipropyldibenzothiophene,
3,7-diamino-2,8-dimethoxydibenzothiophene,
3,7-diamino-2,6-dimethoxydibenzothiophene, and
3,7-diamino-4,6-dimethoxydibenzothiophene.
[0087] The diaminodibenzothiophene=5,5-dioxides (general formula
(A2a-M2)) can include, for example,
3,7-diamino-2,8-dimethyldibenzothiophene=5,5-dioxide,
3,7-diamino-2,6-dimethyldibenzothiophene=5,5-dioxide,
3,7-diamino-4,6-dimethyldibenzothiophene=5,5-dioxide,
2,8-diamino-3,7-dimethyldibenzothiophene=5,5-dioxide,
3,7-diamino-2,8-diethyldibenzothiophene=5,5-dioxide,
3,7-diamino-2,6-diethyldibenzothiophene=5,5-dioxide,
3,7-diamino-4,6-diethyldibenzothiophene=5,5-dioxide,
3,7-diamino-2,8-dipropyldibenzothiophene=5,5-dioxide,
3,7-diamino-2,6-dipropyldibenzothiophene=5,5-dioxide,
3,7-diamino-4,6-dipropyldibenzothiophene=5,5-dioxide,
3,7-diamino-2,8-dimethoxydibenzothiophene=5,5-dioxide,
3,7-diamino-2,6-dimethoxydibenzothiophene=5,5-dioxide, and
3,7-diamino-4,6-dimethoxydibenzothiophene=5,5-dioxide.
[0088] The diaminothioxanthene-10,10-diones that are given by
selecting --CH.sub.2-- as X in the general formula (A2b-M) can
include, for example, 3,6-diaminothioxanthene-10,10-dione,
2,7-diaminothioxanthene-10,10-dione,
3,6-diamino-2,7-diamethylthioxanthene-10,10-dione,
3,6-diamino-2,8-diethylthioxanthene-10,10-dione,
3,6-diamino-2,8-dipropylthioxanthene-10,10-dione, and
3,6-diamino-2,8-dimethoxythioxanthene-10,10-dione.
[0089] The diaminothioxanthene-9,10,10-triones that are given by
selecting --CO-- as X in the general formula (A2b-M) can include,
for example, 3,6-diamino-thioxanthene-9,10,10-trione and
2,7-diamino-thioxanthene-9,10,10-trione.
[0090] Another diamine component giving unit A3 is a diamine
compound other than those described above, and selected from
compounds which can sometimes further improve performance without
deteriorating the effects of the invention in this section.
[0091] Examples can include: [0092] diaminodiphenyl sulfones such
as 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone,
4,4'-diaminodiphenyl sulfone, 4,4'-diamino-3,3'-dimethyldiphenyl
sulfone; [0093] diaminodiphenyl ethers such as 4,4'-diaminodiphenyl
ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether,
3,3'-dimethyl-4,4'-diaminodiphenyl ether and
3,3'-diethoxy-4,4'-diaminodiphenyl ether; [0094] diaminodiphenyl
methanes such as 4,4'-diaminodiphenyl methane and
3,3'-diaminodiphenyl methane; [0095] 2,2-bis(aminophenyl)propanes
such as 2,2-bis(3-aminophenyl)propane and
2,2-bis(4-aminophenyl)propane; [0096]
2,2-bis(aminophenoxyphenyl)propanes such as
2,2-bis[4-(4-aminophenoxy)phenyl]propane and
2,2-bis[4-(3-aminophenoxy)phenyl]propane; [0097]
diaminobenzophenones such as 4,4'-diaminobenzophenone and
3,3'-diaminobenzophenone; [0098] diaminobenzoic acids such as
3,5-diaminobenzoic acid; [0099] phenylenediamines such as
1,3-phenylenediamine and 1,4-phenylene diamine; [0100]
dichlorodiaminodiphenyl ethers such as
2,2'-dichloro-4,4'-diaminodiphenyl ether; [0101] tolidines such as
ortho-tolidine and meta-tolidine; and [0102]
dihydroxydiaminobiphenyls such as
2,2'-dihydroxy-4,4'-diaminobiphenyl.
[0103] Among these, preferred are diaminodiphenyl sulfones,
diaminodiphenyl ethers, diaminobenzoic acids,
dichlorodiaminodiphenyl ethers and dihydroxydiaminobiphenyls.
[0104] When an aromatic polyimide represented by a repeating unit
of general formula (1) is used for an asymmetric air separation
membrane, for example, it is preferable that the tetracarboxylic
acid component is a combination of
4,4'-(hexafluoroisopropylidene-bis(phthalic anhydride) as a
carboxylic acid giving unit B1, 3,3',4,4'-biphenyl tetracarboxylic
dianhydride as a carboxylic acid giving unit B2 and pyromellitic
dianhydride as a carboxylic acid giving unit B3, and the diamine
component is a combination of 2,2',5,5'-tetrachlorobenzidine as a
diamine giving unit A1 and
3,7-diamino-dimethyldibenzothiophene=5,5-dioxide as a diamine
giving unit A2. 3,7-Diamino-dimethyldibenzothiophene=5,5-dioxide
means a mixture of
3,7-diamino-2,8-dimethyldibenzothiophene=5,5-dioxide as a main
component containing isomers in which a methyl group is attached at
a different position, that
3,7-diamino-2,6-dimethyldibenzothiophene=5,5-dioxide and
3,7-diamino-4,6-dimethyldibenzothiophene=5,5-dioxide.
[0105] The aromatic polyimide solution can be suitably prepared by
a two-step process of combining a tetracarboxylic acid component
and a diamine component in an organic polar solvent in a given
composition ratio, which is then polymerized at a low temperature
of around room temperature to form a polyamide acid, and of then
imidizing the polyamide acid by heating or chemically imidizing by
adding, for example, pyridine, or alternatively, a one-step process
of combining a tetracarboxylic acid component and a diamine
component in an organic polar solvent in a given composition ratio,
which is then polymerized and imidized at a high temperature of
about 100 to 250.degree. C., preferably about 130 to 200.degree. C.
In imidizing by heating, the reaction is suitably conducted while
water or an alcohol generated is removed. An amount used of the
tetracarboxylic acid component and the diamine component to the
organic polar solvent is suitably such that a concentration of the
polyimide in the solvent is about 5 to 50% by weight, preferably 5
to 40% by weight.
[0106] The aromatic polyimide solution prepared after the
polymerization and the imidizing can be directly used in spinning.
Alternatively, for example, the aromatic polyimide solution
obtained is added to a solvent in which the aromatic polyimide is
insoluble, to precipitate and isolate the aromatic polyimide, which
is then dissolved in an organic polar solvent to a given
concentration to prepare an aromatic polyimide solution which can
be used in spinning.
[0107] In the aromatic polyimide solution used in the spinning, a
concentration of the polyimide is preferably 5 to 40% by weight,
further preferably 8 to 25% by weight, and a solution viscosity
(rotational viscosity) is 100 to 15000 poise, preferably 200 to
10000 poise, particularly preferably 300 to 5000 poise at
100.degree. C. If a solution viscosity is less than 100 poise, a
uniform membrane (film) may be formed, but an asymmetric membrane
with a large mechanical strength cannot be obtained. If it is more
than 15000 poise, extrusion from a spinning nozzle becomes
difficult, so that an asymmetric hollow fiber membrane having a
desired shape cannot be obtained.
[0108] There are no particular restrictions to the organic polar
solvent as long as it can suitably dissolve an aromatic polyimide
obtained, and examples of such a solvent include phenols such as
phenol, cresol and xylenol; catechols such as catechol and resorcin
in which a benzene ring directly has two hydroxyl groups; phenolic
solvents including halogenated phenols such as 3-chlorophenol,
4-chlorophenol (equivalent to parachlorophenol described later),
3-bromophenol, 4-bromophenol and 2-chloro-5-hydroxytoluene; or
amide solvent including amides such as N-methyl-2-pyrrolidone,
1,3-dimethyl-2-imidazolidinone, N,N-dimethylformamide, N,
N-diethylformamide, N,N-dimethylacetamide and N,N-diethylacetamide;
or mixtures of these.
[0109] A hollow fiber membrane can be suitably prepared by spinning
in a dry/wet manner (dry-wet spinning) using the above aromatic
polyimide solution. The dry-wet manner is a method where a solvent
in the surface of the polymer solution having a hollow fiber shape
is evaporated to form a thin dense layer (separation layer) and
immersing the polymer solution in a coagulation liquid (a solvent
which is compatible with the solvent in the polymer solution and in
which a polymer is insoluble) to cause phase separation which is
then utilized to form pores, giving a porous layer (supporting
layer) (a phase inversion method), and has been proposed by Loeb et
al. (for example, U.S. Pat. No. 3,133,132).
[0110] A dry-wet spinning manner is a method for forming a hollow
fiber membrane using a spinning nozzle in a dry/wet manner, which
is described in, for example, Japanese laid-open patent publication
Nos. 1986-133106 and 1991-267130.
[0111] The production process generally has the steps of spinning
(spinning-dope extruding), coagulating, washing, drying and
heating.
[0112] First, in the spinning step (spinning-dope extruding step),
a spinning nozzle used for extruding a spinning dope solution can
be any nozzle capable of extruding the spinning dope solution as a
hollow fiber form, suitably a tube-in-orifice type nozzle and the
like. Generally, a temperature range of the aromatic polyimide
solution during extrusion is preferable about 20.degree. C. to
150.degree. C., particularly 30.degree. C. to 120.degree. C. A
suitable temperature range depends on a kind of a solvent for the
dope and its viscosity. Furthermore, spinning is conducted while a
gas or liquid is fed into the inside of the hollow fiber form
extruded from the nozzle.
[0113] In the coagulating step subsequent to the spinning step, the
hollow fiber form discharged from a nozzle is extruded into the air
or an inert gas atmosphere such as nitrogen, and then fed to a
coagulation bath for immersion in a coagulation liquid. Suitably, a
coagulation liquid is substantially unable to dissolve an aromatic
polyimide component while being compatible with a solvent in the
aromatic polyimide solution. Suitable examples include, but not
limited to, water; lower alcohols such as methanol, ethanol and
propyl alcohol; ketones having a lower alkyl group such as acetone,
diethyl ketone and methyl ethyl ketone; and their mixtures. When
the solvent in the aromatic polyimide solution is an amide solvent,
an aqueous solution of the amide solvent is also preferable.
[0114] In the next washing step, if necessary, the hollow fiber is
washed with a washing solvent such as ethanol, and then the
coagulation liquid and/or the washing solvent in the outside and
the inside of the hollow fiber are replaced with a replacing
solvent including an aliphatic hydrocarbon such as isopentane,
n-hexane, isooctane and n-heptane.
[0115] In the subsequent drying step, the hollow fiber including
the replacing solvent is dried at a proper temperature. Then, in
the heating step, the fiber is heated preferably at a temperature
lower than a softening point or second-order transition point of
the aromatic polyimide used, to give an asymmetric gas separation
hollow fiber membrane.
INDUSTRIAL USABILITY
[0116] In accordance with the invention of this section,
nitrogen-rich air containing a higher concentration of nitrogen can
be obtained by feeding the air at a high temperature, for example,
150.degree. C. or more to an air separation membrane module. A
process according to the invention in this section can be used, for
example, for an explosion-proof system in a fuel tank in an
aircraft.
[0117] The inventions according to section A are as follows.
[0118] [1] A process for producing nitrogen-rich air using an air
separation membrane module, comprising feeding the air at
150.degree. C. or higher to the air separation membrane module.
[0119] [2] The process according [1], wherein for the air
separation membrane module,
[0120] at the initiation of the use, an oxygen-gas permeation rate
(P'.sub.O2) at 175.degree. C. is 20.times.10.sup.-5
cm.sup.3(STP)/cm.sup.2seccmHg or more and a ratio of an oxygen-gas
permeation rate to a nitrogen-gas permeation rate
(P'.sub.O2/P'.sub.N2) at 175.degree. C. is 1.8 or more; and
[0121] after the use at 175.degree. C. for 140 hours, P'.sub.O2 and
P'.sub.O2/P'.sub.N2 are retained in levels of 90% or more of
P'.sub.O2 and P'.sub.O2/P'.sub.N2 before the initiation of the use,
respectively.
[0122] [3] The process as described in [1] or [2], wherein an air
separation membrane in the air separation membrane module comprises
a material having no glass-transition temperatures at 225.degree.
C. or lower.
[0123] [4] The process according to any one of [1] to [3], wherein
after being placed at 175.degree. C. for 2 hours, the air
separation membrane exhibits a shape-retention ratio of 95% or
more.
[0124] [5] A method for explosion protection of an aircraft,
comprising producing nitrogen-rich air by the production process
according to any one of [1] to [4], and feeding the nitrogen-rich
air to a fuel tank for an aircraft.
Section B: A Gas Separation Membrane Module Having Adequate Heat
Resistance and Pressure Resistance at a High Temperature and a High
Pressure without being Cracked
Technical Field
[0125] The invention of this section relates to a gas separation
membrane module for mixed-gas separation in which a fiber bundle
consisting of a number of hollow fiber membranes exhibiting
selective permeability is fixed together to a tube sheet
manufactured by curing a particular epoxy composition.
Background Art
[0126] A hollow-fiber type gas separation membrane module has a
fiber bundle consisting of a number of hollow-fiber membranes
exhibiting selective permeability, at least one end of which is
fixed together to a plate (tube sheet) of a cured resin of cast
molding, and the fiber bundle is housed in a casing comprising at
least a mixed gas inlet, a permeate gas outlet and a non-permeate
gas outlet. Besides functioning to fix the fiber bundle together,
the tube sheet has another function to isolate the internal space
of the hollow fiber membrane from its external space, and to retain
gas tightness of the internal space and external space by sealing
between the hollow fibers and between the hollow fibers and the
casing. The hollow-fiber type gas separation membrane module would
fail to perform suitable separation if gas-tightness by the tube
sheet is lost.
[0127] In a gas separation method using a separation membrane,
suitable gas separation can be sometimes achieved by feeding a
mixed gas at a high temperature and a high pressure. In such cases,
a material for a tube sheet is required to exhibit higher heat
resistance and pressure resistance and its glass-transition
temperature or heat deflection temperature must be higher by at
least several dozens of degrees centigrade than an operation
temperature of the gas separation membrane module.
[0128] A thermosetting resin is generally used as a tube sheet
material for achieving higher heat resistance and pressure
resistance, which is heated at a considerably high temperature
during tube sheet formation for completing curing of the
thermosetting resin. If a tube sheet prepared by incomplete curing
is used, the curing reaction proceeds during operating a separation
membrane module at a high temperature and the tube sheet is shrunk,
which causes inadequate sealing between the tube sheet and the
casing. The tube sheet material must be, therefore, heat-resistant
to a considerably high temperature during the tube sheet
formation.
[0129] As a gas separation membrane module which can be used for
separation of a mixed gas at a high temperature and a high
pressure, for example, Japanese laid-open patent publication No.
1987-74434 has described a hollow fiber element produced using a
denatured epoxy resin prepared by reacting a phenol-novolac type
epoxy resin with a liquid polybutadiene having a reactive terminal
functional group.
Problems to be Solved by the Invention in Section B
[0130] However, a conventional tube sheet material is subjected to
much cure shrinkage during a tube sheet formation, which causes
problems such as cracks and breakage of the tube sheet.
Furthermore, when a priority is given to only pressure resistance
and heat resistance, there may be problems such as crack forming
and breakage of the tube sheet under impact during operation
because a flexibility of the tube sheet material is poor. An
objective of the invention of this section is to provide a tube
sheet for a gas separation membrane module retaining adequate heat
resistance and pressure resistance under a high temperature and a
high pressure without being cracked.
[0131] The summary of the main invention disclosed in this section
is as follows.
[0132] [1] A gas separation membrane module comprising
[0133] a fiber bundle consisting of a number of hollow fiber
membranes having gas separation performance;
[0134] a casing having a mixed gas inlet, a permeate gas outlet and
a non-permeate gas outlet, in which the hollow fiber bundle is
placed; and
[0135] a tube sheet fixing at least one end of the hollow fiber
bundle;
[0136] wherein the tube sheet is formed by an epoxy cured material
prepared by curing a casting resin composition containing
[0137] a denatured epoxy resin formed by reacting (a) a phenol
novolac type epoxy compound and (b) a butadiene-acrylonitrile
copolymer having a terminal functional group capable of reacting
with an epoxy group, and
[0138] (c) a hardener.
Advantages of the Invention in Section B
[0139] Since a tube sheet in a gas separation membrane module
according to the invention of this section is produced using a
butadiene-acrylonitrile copolymer having a terminal functional
group capable of reacting with an epoxy group, it is more flexible
than a conventional tube sheet. Furthermore, when it is exposed to
a high-temperature and high-pressure gas during forming a tube
sheet or operating a gas separation membrane module, the tube sheet
is not cracked and its adhesiveness to a hollow fiber or sealing
between the tube sheet and a casing is not deteriorated.
Embodiments in Section B
[0140] An epoxy cured material forming a tube sheet in a hollow
fiber element according to the invention of this section can be
produced by heat curing a casting resin composition containing at
least
[0141] a denatured epoxy resin formed by reacting (a) a phenol
novolac type epoxy compound and (b) a butadiene-acrylonitrile
copolymer having a terminal functional group capable of reacting
with an epoxy group, and
[0142] (c) a hardener.
[0143] This will be detailed below.
Denatured Epoxy Resin
[0144] A denatured epoxy resin can be obtained by reacting a phenol
novolac type epoxy compound (hereinafter, sometimes referred to as
epoxy compound (a)) with a butadiene-acrylonitrile copolymer having
a terminal functional group capable of reacting with an epoxy group
(hereinafter, sometimes referred to as compound (b)).
[0145] A phenol novolac type epoxy compound (a) used in the
invention of this section is a compound represented by general
formula (a):
##STR00016##
[0146] wherein R'' represents alkyl having 1 to 3 carbon atoms or
hydrogen; and n represents an integer of 0 to 500, preferably 0 to
20.
[0147] In Formula (a), R'' is preferably methyl or hydrogen. The
epoxy compound (a) represented by general formula (a) preferably
has a molecular weight of 300 to 2000 and an epoxy equivalent of
150 to 250. Examples of epoxy compound (a) include jER152 and
jER154 from Mitsubishi Chemical Corporation; EPICLON-N740, N-770,
N-775 and the like from DIC Corporation; YDPN-638 and YDCN-700
series from Tohto Kasei Co., Ltd.; and D.E.N.438 from The Dow
Chemical.
[0148] In a butadiene-acrylonitrile copolymer having a terminal
functional group capable of reacting with an epoxy group (compound
(b)) used in the invention of this section, examples of the
functional group capable of reacting with an epoxy group include
carboxyl, amino and hydroxyl groups, particularly preferably
carboxyl group. A resulting tube sheet can be made flexible by
comprising the compound (b).
[0149] The butadiene-acrylonitrile copolymer having a terminal
functional group capable of reacting with an epoxy group is
preferably a carboxyl-terminated butadiene acrylonitrile copolymer
(CTBN) represented by general formula (b).
##STR00017##
[0150] In Formula (b), m represents the total number of repetition
of the butadienemonomer unit and n represents the total number of
repetition of the acrylonitrile monomer unit, and when 2 or more of
the structures represented in [ ] are present, m and n represent
the sum of a repetition number of each unit, respectively, and they
can be present as a block or at random.
[0151] CTBN represented by general formula (b) preferably has a
molecular weight of 2000 to 4000; for example, CTBN preferably
contains 5 to 50% by weight of an acrylonitrile monomer unit.
Examples of commercially available CTBN include
Hypro.TM.CTBN1300.times.8, CTBN1300.times.13 and CTBN1300.times.31
from Emerald Performance Materials.
[0152] A denatured epoxy resin is produced by mixing preferably 5
to 50 parts by weight, more preferably 5 to 20 parts by weight of
compound (b) with 100 parts by weight of epoxy compound (a) and
reacting them. The use of a denatured epoxy resin in which the
contents of these compounds are within the above ranges can avoid
crack formation in a resulting tube sheet at a high temperature and
a high pressure and there is no problem of deformation due to too
lowering of a glass-transition temperature. Other compounds can be
added as long as they do not adversely affect the objectives of the
invention in this section. Although there are no particular
restrictions to the reaction conditions in preparing the denatured
epoxy resin, a reaction temperature is preferably 100 to
200.degree. C. and a reaction time is preferably 2 to 5 hours.
Hardener
[0153] There are no particular restrictions to a hardener used in
the invention of this section as long as it is a thermosetting
agent for an epoxy resin, including amines, phenols and acid
anhydrides, more preferably acid anhydrides. Examples of an acid
anhydride include phthalic anhydride, pyromellitic dianhydride,
methyl-5-norbornene-2,3-dicarboxylic anhydride(methylnadic
anhydride) and benzophenone tetracarboxylic dianhydride,
particularly preferably methyl-5-norbornene-2,3-dicarboxylic
anhydride.
Hardening Accelerator
[0154] A casting resin composition used in the invention of this
section can, if necessary, contain a hardening accelerator, which
can include an imidazole compound. Examples of an imidazole
compound include 2-methylimidazole, 2-ethylimidazole,
2-ethyl-4-methylimidazole, 2-undecylimidazole,
2-heptadecylimidazole, 2-phenylimidazole,
1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole and
1-cyanoethyl-2-ethyl-4-methylimidazole, particularly preferably
2-ethyl-4-methylimidazole.
Epoxy Cured Material
[0155] An epoxy cured material forming the tube sheet in the
invention of this section can be produced by heat-curing a casting
resin composition containing the above denatured epoxy resin, a
hardener and, if necessary, a hardening accelerator (hereinafter,
sometimes referred to as a casting resin composition). A mixing
ratio of the denatured epoxy resin to the hardener and so on in
preparation of the casting resin composition depends on the number
of epoxy functional groups in the denatured epoxy resin and the
number of functional groups in the hardener and can be
appropriately adjusted depending on, for example, a viscosity of
the desired casting resin composition. To 100 parts by weight of
the denatured epoxy resin, preferably 0 to 5 parts by weight, more
preferably 0.1 to 3 parts by weight of the hardening accelerator is
used.
[0156] In a heating step, for example, the casting resin
composition is subjected to the first curing by heating it until
the casting resin composition does not flow, and then the resin
after the first curing is preferably post-cured at a further high
temperature. In post-curing, for avoiding change in physical
properties of the tube sheet material during operating the module,
the casting resin composition is preferably heated at a temperature
equal to or higher than a temperature in the final operation, for
example, preferably 100.degree. C. to 250.degree. C., more
preferably 120.degree. C. or more, for 2 to 10 hours. The first
curing is, for example, but not limited to, preferably less than
100.degree. C., more preferably 50 to 85.degree. C. for 2 to 24
hours. It is preferable that the resin after the first curing is
heated to a post-curing temperature at a temperature-increase rate
of 5.degree. C./min or less because thermal runaway due to reaction
heat rapidly generated in the casting resin composition can be
avoided. A process for forming a tube sheet will be described
later.
Gas Separation Membrane Module
[0157] There will be described a structure of a gas separation
membrane module according to the invention of this section.
[0158] It is known that a gas separation membrane module made up of
hollow fiber membranes is a bore feed type or a shell feed type.
For example, in a bore feed type gas separation membrane module, a
number of hollow fiber membranes B14 (for example, several hundred
to several hundred-thousand) are put together as a hollow fiber
bundle, which is housed in a casing B15 having at least a mixed gas
inlet B11, a permeate gas outlet B12 and a non-permeate gas outlet
B13, and is fixed to the casing B15 with tube sheets B16a and B16b
formation in such a manner that the hollow fiber membranes B14 are
open at the both ends of the hollow fiber bundle, so that a space
where a gas is fed from a mixed gas inlet B11, passes through the
inside of the hollow fiber membrane B14 and is led to a
non-permeate gas outlet B13 (non-permeate side) and a space outside
of the hollow fiber membrane B14 leading to a permeate gas outlet
B12 (permeate side) are isolated each other as shown in FIG. 3(A).
The casing B15 can be made of, for example, a material including
metals such as stainless steel, plastics, fiber-reinforced plastics
and ceramics. In a shell feed type gas separation membrane module,
for example, as shown in FIG. 3(B), a tube sheet is formed at one
end of a hollow fiber bundle in such a manner that a non-permeate
side space where a mixed gas is fed from a mixed gas inlet B11 and
is led to a non-permeate gas outlet B13 is outside of the hollow
fiber membranes B14 while a permeate side space leading to the
permeate gas outlet B12 is inside of the hollow fiber membranes
B14.
[0159] In FIGS. 3(A) and (B), while a mixed gas fed from the mixed
gas inlet B11 in the gas separation membrane module flows in
contact with the hollow fiber membrane B14 in the gas separation
membrane module, a high permeate gas preferentially permeates the
hollow fiber membrane B14 to separate the mixed gas into a gas rich
in a high permeate gas (permeate gas) and a remaining non-permeate
gas poor in a high permeate gas (non-permeate gas). The permeate
gas is discharged from the permeate gas outlet B12 while the
non-permeate gas is discharged from the non-permeate gas outlet
B13. Either or both of the non-permeate gas and the permeate gas
discharged from the gas separation membrane module are recovered,
depending on an application.
[0160] As a hollow fiber used in a gas separation membrane, the use
of a number of hollow fibers with a thin thickness and a small
diameter is preferable because a high membrane area and a higher
separation efficiency can be conducted even in a small device,
which is economically advantageous. For example, the hollow fiber
can have, but not limited to, a film thickness of 10 to 500 .mu.m
and an outer diameter of 50 to 2000 .mu.m. Furthermore, a gas
separation membrane can be homogeneous or heterogeneous like a
composite membrane or an asymmetric membrane, and can be
microporous or nonporous.
[0161] Examples of a gas separation membrane can include those made
of a polymer materials such as polyimides, polyetherimides,
polyamides, polyamideimides, polysulfones, polycarobnates, silicone
resins, cellulose polymers and ceramic materials such as zeolite.
For example, a gas separation membrane made of a polyimide is
preferably an aromatic polyimide hollow fiber separation membrane,
more preferably an aromatic polyimide asymmetric hollow fiber
separation membrane.
[0162] A fiber arrangement of a hollow fiber bundle may include
parallel arrangement, cross arrangement, fabric arrangement and
spiral arrangement. A hollow fiber bundle can have a core tube
substantially in the center or the periphery of a hollow fiber
bundle can be wrapped with a film. Furthermore, the shape of the
hollow fiber bundle can be cylindrical, tabular or prismatic, and
it can be put in the casing in an unchanged shape as described
above, or in a folded U-shape or a spirally coiled shape.
[0163] There will be described a process for producing a gas
separation membrane module according to the invention of this
section.
[0164] First, there will be described a method for putting hollow
fiber membranes together as a hollow fiber bundle.
[0165] The following is an example of a method for putting together
hollow fiber membranes in such a manner that they alternately cross
each other at an angle of 5 to 30.degree. to an axial direction.
One to 100 hollow fiber membranes are arranged on a tube to be a
core (core tube) by a fiber-arranging guide which shuttles at a
certain rate in an axial direction of the core tube, while the core
tube simultaneously rotates at a certain rate. Thus, the hollow
fiber membranes are arranged not in parallel with the axis, but at
an angle corresponding to rotation of the core tube to the axial
direction. Once fiber arrangement reaches one end, the hollow fiber
membranes are fixed there and then the fiber-arranging guide moves
back in the reverse direction. Since the core tube continues to
rotate in the same direction, then the fibers are arranged at an
angle to the axial direction which is just opposite to the above
angle. This process is repeated so that hollow fiber membranes are
alternately arranged on hollow fiber membranes arranged in an
opposite angle to give a hollow fiber bundle.
[0166] There will be described a method for forming a tube sheet in
the invention of this section. A method for forming a tube sheet
can be centrifugal molding or stationary molding, and stationary
molding is preferable because a convenient apparatus can be used
and an productivity can be increased. There will be described an
example of stationary molding.
[0167] For example, a hollow fiber bundle, which a given number of
hollow fiber membranes B24 with a given length is put together by
the above method, is put in a casing B22 without a core tube or
with a core tube remained substantially in the center. Then, it is
placed in a given position in a mold B21 whose end a tube sheet is
to be formed, and subsequently, the hollow fiber bundle and the
cylindrical casing B22 are substantially vertically held in such a
way that the end is down. FIG. 4b schematically shows this
state.
[0168] A given amount of a casting resin composition for forming a
tube sheet B 23 is cast into the mold B21. FIG. 4c schematically
shows the state where the casting resin composition has been
injected. Although there are no particular restrictions to a method
for casting a casting resin composition, casting from the lower
part of the mold using a syringe is preferable because it is easy
to uniformly cast the casting resin composition in the mold B21 and
between the hollow fiber membranes B24. If the casting resin
composition is cast too fast, the casting resin composition cannot
be uniformly cast to the parts to be filled, and therefore, it is
preferably cast over a sufficient period. It is suitable to
appropriately control a temperature of the mold B21 during casting
the casting resin composition into the mold B21. Likewise, it is
suitable to control a temperature of the casting resin
composition.
[0169] The casting resin composition before curing is preferably in
a liquid state at a temperature during resin cast in the light of
moldability.
[0170] There are no particular restrictions to a viscosity of the
casting resin composition, but it is preferable that a viscosity at
a temperature of 70 to 90.degree. C. common in resin cast is
preferably less than 120 poise, particularly preferably less than
20 poise. Here, a viscosity of the resin composition can be
suitably measured using a rotating viscometer.
[0171] If a viscosity of the casting resin composition at a
temperature of 70 to 90.degree. C. is 120 poise or more, there is a
problem that a resin cast in molding a tube sheet takes a long time
and foams generated during resin cast cannot be easily removed, and
also, a space between the hollow fiber membranes are inadequately
filled with the resin, which causes voids.
[0172] After cast of the casting resin composition into the mold
B21, the mold B21 and the hollow fiber bundle are kept at a certain
temperature to conduct the first curing of the casting resin
composition to form a tube sheet B23. In this process, a
temperature is suitably less than 100.degree. C., preferably 50 to
85.degree. C. An excessively high temperature in this stage is not
preferable because curing of the casting resin composition becomes
so severe that strength of a tube sheet finally obtained is
adversely affected.
[0173] After curing of the casting resin composition, it is
preferable to conduct post-curing of the casting resin composition
by heating in the light of improving durability and mechanical
properties. A temperature during the post-curing is preferably
100.degree. C. to 250.degree. C. A temperature of lower than
100.degree. C. during post-curing is not preferable because the
casting resin composition is inadequately cured. Furthermore, an
excessively high temperature during post-curing is not preferable
because curing of the casting resin composition becomes so severe
that a problem about a strength of a tube sheet occurs. In
post-curing of the casting resin composition, the composition can
be heated at different temperatures in multiple steps.
[0174] After post-curing of the casting resin composition, the tube
sheet is cut to open the ends of the hollow fiber membranes, giving
a hollow fiber element in which the ends of the hollow fibers are
kept open and fixed to the tube sheet.
[0175] Here, in case of forming a tube sheet at both ends of the
hollow fiber bundle, after a tube sheet is formed at one end of the
hollow fiber bundle as described above, then a tube sheet is formed
at the other end by a similar procedure. "After a tube sheet is
formed at one end" may be "after the hollow fiber membranes are
made open by cutting the tube sheet". Alternatively, it is also
suitable that one end is placed within the mold, the casting resin
composition is cast and subjected to the first curing and then a
tube sheet is formed at the other end before post-curing, and both
ends can be processed by the procedure after the post-curing at the
same time.
[0176] For a method for separating a mixed gas using a separation
membrane module according to the invention of this section, there
are no particular restrictions to a mixed gas to be separated as
long as it is a mixed gas of two or more components. A gas
separation membrane module according to the invention of this
section can be suitably used for, for example, separation of
nitrogen-rich air and oxygen-rich air from the air, separation of
hydrogen gas from a hydrogen-containing mixed gas and separation of
water vapor from a mixed vapor of water vapor and an organic vapor
(dehydration of an organic vapor).
[0177] The inventions according to section B are as follows.
[0178] [1] A gas separation membrane module comprising a fiber
bundle consisting of a number of hollow fiber membranes having gas
separation performance;
[0179] a casing having a mixed gas inlet, a permeate gas outlet and
a non-permeate gas outlet, within which the hollow fiber bundle is
placed; and
[0180] a tube sheet fixing at least one end of the hollow fiber
bundle;
[0181] wherein the tube sheet is formed by an epoxy cured material
prepared by curing a casting resin composition containing
[0182] a denatured epoxy resin formed by reacting (a) a phenol
novolac type epoxy compound and (b) a butadiene-acrylonitrile
copolymer having a terminal functional group capable of reacting
with an epoxy group, and
[0183] (c) a hardener.
[0184] [2] The gas separation membrane module according to [1],
wherein the casting resin composition further contains a curing
accelerator.
[0185] [3] The gas separation membrane module according to [1] or
[2], wherein the functional group capable of reacting with an epoxy
group is a carboxyl group.
[0186] [4] The gas separation membrane module according to any one
of [1] to [3], wherein the hardener is an acid anhydride.
[0187] [5] The gas separation membrane module according to any one
of [2] to [4], wherein the curing accelerator is an imidazole
compound.
Section C: A Separation Membrane Module and so on Satisfactorily
Operable Even at High Temperature
Technical Field
[0188] The invention disclosed in this section relates to a gas
separation membrane module having a hollow fiber element wherein a
hollow fiber bundle including a number of hollow fiber membranes
with selective permeability is fixed by tube sheet prepared by
curing a particular epoxy resin composition. In particular, the
invention relates to a separation membrane module satisfactorily
operable at high temperature by reducing influence of thermal
expansion of a tube sheet.
Background Art
[0189] The hollow fiber type gas separation membrane module
generally has a hollow fiber element including a fiber bundle
comprising a number of hollow fiber membranes with selective
permeability, and a hollow vessel housing the element. Both ends or
one end of the hollow fiber bundle in the hollow fiber element are
fixed to the end of the vessel by the resin-cured plate (tube
sheet). The vessel has, at least, a feed gas inlet, a permeate gas
outlet and a non-permeate gas outlet.
[0190] In a gas separation membrane, generally, the higher
temperature and pressure of feed gas are, the larger gas permeation
rate is. Therefore when a gas separation module is used, it is
sometimes considered to compress the feed gas before being fed to
the module for example by a compressor. The compressed gas may be
fed at very high temperature of 149.degree. C. to 260.degree.
C.
[0191] When the separation membrane module is used under
high-temperature conditions as described above, thermal expansion
of a tube sheet may cause, for example, stress concentration within
the tube sheet, or cracks in the tube sheet due to the stress
concentration which may cause loss of airtightness in the
separation membrane module. Especially, high-temperature gas
compressed by a compressor or the like is generally cooled before
being fed to the gas separation membrane module. There is room for
improvement in conventional separation membrane modules in terms of
the use at high temperature (e.g. designing components more
effectively by taking the special condition of high temperature
into consideration). Furthermore, whether separation membrane
module is for a high temperature or not, it is required to simplify
a structure of the separation membrane module and to develop
structures which can contribute to downsizing.
[0192] In the light of the above problems, an objective of the
invention in this section is to provide a separation membrane
module which can satisfactorily operate at high temperature, with
the influence of thermal expansion of the tube sheet being
minimized. Another objective is to provide a structure advantageous
to downsizing and weight saving by simplifying the structure of a
separation membrane module.
[0193] The summary of the main invention disclosed in this section
is as follows.
[0194] [1] A separation membrane module using on high-temperature
conditions, comprising;
[0195] a hollow fiber bundle including a number of hollow fiber
membrane with selective permeability,
[0196] a cylindrical vessel housing the hollow fiber bundle,
[0197] a tube sheet placed at the end of the hollow fiber bundle,
which fixes the end of the bundle to the end of the cylindrical
vessel and separates the inside of the cylindrical vessel from the
outside, and
[0198] an annular sealing member for sealing between the outer
surface of the tube sheet and the inner surface of the cylindrical
vessel;
[0199] wherein the tube sheet does not have any step in a portion
around the place to which a sealing member is attached.
[0200] According to such a configuration, since there is no steps
in the tube sheet on the periphery of the place on which the
annular sealing member (detailed below) is mounted, influence of
stress concentration in use under high temperature can be reduced
in comparison with conventional structures in which the tube sheet
has step(s) for O-ring.
[0201] The term, "annular sealing member" as used in this section
means an annular sealing member which seals between the outer
surface of a tube sheet and the inner surface of a cylindrical
vessel, and there are no particular restrictions to its
cross-sectional shape. The annular sealing member can be, for
example, an O-ring (substantially circular cross section), or can
be V- or U-packing having a substantially V- or U-shaped cross
section, respectively. Furthermore, its cross section can be
elliptic, rectangular, polygonal or X-shaped.
[0202] The term, "under the high-temperature conditions" means a
temperature in the range of 80.degree. C. to 300.degree. C.
[0203] The term, "cylindrical vessel" includes not only those with
both ends being open but also those with one end being open.
[0204] A gas separation membrane module can be used for
applications such as separation of oxygen, nitrogen, hydrogen,
water vapor, carbon oxide or an organic vapor.
First Embodiment in Section C
[0205] FIG. 5 schematically shows a basic configuration of a gas
separation membrane module. In the following description, there
will be described several embodiments, which are not independent of
each other and the contents of these embodiments can be combined as
appropriate.
[0206] A gas separation membrane module 1, as shown in FIG. 5, has
a hollow fiber bundle 15 of hollow fiber membranes 14 with
selective permeability and a substantially cylindrical vessel 10
housing the hollow fiber bundle 15. The cylindrical vessel 10 is
made of for example metal and has openings at both ends. The
cylindrical vessel 10 can have a circular, elliptic or polygonal
cross section. The case having a circular cross section (that is,
the vessel 10 is cylindrical) will be described below.
[0207] The hollow fiber membrane 14 can be used conventional
well-known membrane and can be made of any materials as long as it
has gas separation ability. For example, it is suitably made of
polymer material, which is glassy at normal temperature (23.degree.
C.) such as, in particular, polyimide, polysulfone, polyetherimide,
polyphenylene oxide and polycarbonate for their gas separation
ability.
[0208] The hollow fiber bundle 15 can be of about 100 to 1,000,000
hollow fiber membranes. There are no particular restrictions to the
shape of the collected hollow fiber bundle, however a cylindrical
hollow fiber bundle is preferable in the light of easiness in
production and pressure resistance of a vessel. FIG. 5 shows an
embodiment in which hollow fiber membranes are disposed
substantially in parallel, however, these hollow fiber membranes
can be cross-arranged.
[0209] Again referring to FIG. 5, tube sheets 30 are placed at the
end of the hollow fiber bundle 15 in each end of the vessel 10, and
an annular sealing member 17 is disposed on the periphery of each
tube sheet. The annular sealing member 17 can be, for example, an
O-ring (substantially circular cross section), or can be V- or
U-packing having a substantially V- or U-shaped cross section,
respectively. A case of an O-ring will be described below.
[0210] The tube sheet 30 is made of a cured material of epoxy resin
composition (detailed below) in this example, and it is formed
substantially as a disc-shape to be fitted into the end of the
vessel 10. The hollow fiber membranes 14 penetrate this tube sheet
30 in its thickness direction, with the end of each hollow fiber
membrane 14 opened to the outer surface of the tube sheet 30. The
tube sheet has a function of fixing many hollow fiber membranes
together. The tube sheet also has a function of maintaining
airtightness by separating the internal space of the membranes from
the external spaces, and sealing between the hollow fiber membranes
as well as between the hollow fiber membranes and the inner surface
of the vessel in cooperation with the annular sealing member.
[0211] There are no particular restrictions to a cured resin for
the tube sheet 30 as long as it is resistant to a high temperature
and can maintain airtightness of the inside of the hollow fiber
module. The resin is preferably also resistant to water vapor when
being used for dehydrating an organic vapor or moisturizing. In
general, a thermosetting resin such as polyurethane or an epoxy
resin is suitably used. In the light of resistance to a high
temperature and strength, an epoxy resin is particularly suitably
used. For a nitrogen membrane module, the epoxy resin for example
described in Japanese published examined application No. 1990-36287
can be used, whereas for an organic-vapor separation module the
epoxy resin for example described in WO 2009/044711 can be used.
The epoxy resin as disclosed in section B can also be used for the
tube sheet in the module of this section.
[0212] Caps 20 and 21 are attached to the ends of the cylindrical
vessel 10 in the separation membrane module 1 as shown in FIG. 5. A
mixed gas inlet 22A is formed in the cap 20, while a non-permeate
gas outlet 22B is formed in the cap 21. An outlet 12 for a permeate
gas is formed in a part of the peripheral wall of the vessel 10. It
is noted that the invention in this section is mainly characterized
in surrounding structures of the tube sheet 30 as described later,
however there are no particular restrictions to the type of a
separation membrane module as long as it can form such a
structure.
[0213] A structure in the vicinity of the tube sheet will be
described with reference to FIG. 6. FIG. 6(a) shows an exemplary
structure of a module end according to the invention of this
section, while FIG. 6(b) shows another structure.
[0214] An O-ring 18 is mounted between the inner surface of the
cylindrical vessel 10 and the outer surface of the tube sheet 530
to ensure airtightness between these members in the gas separation
membrane module shown in FIG. 6(b). Specifically, there is formed a
step 530s to which the O-ring 18 is fitted in a part of the outer
circumference of the tube sheet 530. When the gas separation
membrane module 101 is used under high temperature, stress
concentration can occurs in the vicinity of the step 530s in the
tube sheet 530, depending on the conditions, which may cause
troubles such as breakage of the tube sheet accompanying loss of
airtightness.
[0215] To deal with this problem, according to the structure of
this embodiment, the tube sheet 30 without a step in the outer
surface is used as shown in FIG. 6(a). In this example, a diameter
of the tube sheet 30 is constant over its full length (for another
aspect, described later with reference to FIG. 7). A step 10s is
formed at the end of the cylindrical vessel 10, so that a groove
for the O-ring 18 can be formed within the step. A cross-sectional
shape of the groove is, for example, a rectangle. The O-ring 18 is
to be fitted into the groove, to ensure airtightness between the
outer surface of the tube sheet and the inner surface of the
cylindrical vessel.
[0216] The O-ring 18 is also firmly contacted to the inner surface
of the cap 20, so that airtightness can be also ensured between the
vessel end and the cap inner surface. According to such a
configuration, the one O-ring 18 contributes to sealing both (i)
between the tube sheet and the cylindrical vessel and (ii) between
the cap and the cylindrical vessel, thus the necessity of
additional O-ring(s) can be eliminated.
[0217] There are no particular restrictions to means for fixing the
cap 20 to the cylindrical vessel 10, however, various well-known
means, for example such as fixing by an adhesive or by fixture can
be employed.
[0218] According to the gas separation membrane module 1 in this
embodiment configured as described above, no step is formed on the
tube sheet 30 in the periphery where the O-ring 18 is to be
mounted. Therefore, it is less influenced by stress concentration
in use under high temperature than conventional structure as shown
in FIG. 6(b). As a result, resistance to high temperature and
reliability of the gas separation membrane module 1 as a whole can
be improved.
[0219] Such advantages can be achieved likewise, in addition to the
structure shown in FIG. 6(a), in the structure shown in FIG. 7.
That is, means for preventing transfer of the tube sheet 30 along
the axial direction is not described in the configuration of FIG.
6(a) to simplify the explanation, however, the configuration of
FIG. 7 contains such means.
[0220] A step 10t is formed at a predetermined distance inside from
the end of the vessel 10 as shown in FIG. 7 in this gas separation
membrane module 1'. In response to this, there is also formed a
step 30't at the end of the tube sheet 30'. The other structural
elements are as described in FIG. 6(a). According to such a
configuration, the end of the tube sheet 30' (right side in this
figure) abuts on the step 10t, to thereby prevent the tube sheet
from moving inward along the axial direction.
[0221] Although the gas separation membrane module in FIG. 5 has
been described with reference to an example, the invention in this
section is, of course, applicable to another configuration. For
example, the invention can be suitably applied to a shell feed type
module and a purge type module where the cylindrical vessel has a
purge gas inlet.
Second Embodiment in Section C
[0222] FIG. 8 shows an exemplary structure of the module end in the
second embodiment; FIGS. 8(a) and 8(b) show the state at normal
temperature and the state in operation, that is, at high
temperature, respectively.
[0223] The gas separation membrane module in FIG. 8 has, like the
above embodiment, a hollow fiber bundle 15 as a collection of a
number of hollow fiber membranes with selective permeability and a
cylindrical vessel 10 housing the hollow fiber bundle. Furthermore,
it has tube sheets 38 at the ends of the hollow fiber bundle 15 and
caps 20 at the ends of the cylindrical vessel 10. For structural
members similar to those in the above embodiment, the same symbols
as used in the figures as described above are used without being
redundantly described.
[0224] As shown in FIG. 8(a), this gas separation membrane module
is designed such that the diameter of the tube sheet 38 is slightly
smaller at normal temperature than the inner diameter of the inner
surface 10a of the cylindrical vessel 10, thus there is a gap
between the outer surface of the tube sheet 38 and the inner
surface 10a of the cylindrical vessel. The tube sheet 38 is made
of, like the above embodiment, a resin material such as an epoxy
resin, which has a larger thermal expansion coefficient than a
material for the cylindrical vessel 10 (for example a metal).
[0225] This gas separation membrane module is intended to be used,
for example, at a temperature in the range of 80.degree. C. to
300.degree. C. As shown in FIG. 8(b), when using this module, the
tube sheet 38 is warmed to a predetermined temperature, as a
result, the diameter of the tube sheet will be expanded due to
thermal expansion, so that its outer surface can be firmly
contacted to the inner surface 10a of the cylindrical vessel. Such
a contact ensures airtightness between these members.
[0226] When using the gas separation membrane module, the module is
adequately warmed to ensure airtightness between the tube sheet 38
and the cylindrical vessel 10 and then a mixed gas is fed.
[0227] According to the above configuration, the tube sheet 38
thermally expands to exert the effect of sealing between the tube
sheet and the cylindrical vessel. Thus, it can eliminate the
necessity for placing other O-ring(s) for sealing between these
members or adhering the outer surface of the tube sheet to the
inner surface of the cylindrical vessel. Furthermore, when the tube
sheet 38 thermally expands, the stress to the cylindrical vessel 10
can be reduced, so troubles such as breakage of the cylindrical
vessel 10 can be advantageously prevented.
[0228] Although the above description assumes that the tube sheet
and the cylindrical vessel are made of epoxy resin and metal,
respectively, the material for the cylindrical vessel is not
limited to metal as long as the material has a thermal expansion
coefficient smaller than the tube sheet. Although being not shown
in FIG. 8, sealing means for sealing between the cap 20 and the
cylindrical vessel 10 can be used. For example, annular sealing
member(s) to be disposed between the inner surface of the cap 20
and the outer surface of the cylindrical vessel 10 or between the
inner surface of the cap 20 and the end face of the cylindrical
vessel 10 can be used.
Third Embodiment in Section C
[0229] FIG. 9 shows an exemplary module end structure of a module
according to third embodiment. It is noted that although the module
in the first and the second embodiments are intended to be used at
high temperature, there are no particular restrictions to an
operating temperature for the gas separation membrane module in
FIG. 9.
[0230] The gas separation membrane module in FIG. 9 has, like the
above two embodiments, a hollow fiber bundle 15 as a collection of
a number of hollow fiber membranes with selective permeability, a
cylindrical vessel 10 housing the hollow fiber bundle, tube sheet
30 at the end of the hollow fiber bundle 15 and a cap 20 at the end
of the cylindrical vessel 10. Furthermore, it has an O-ring 18 for
sealing between the tube sheet and the cylindrical vessel. For
structural members similar to those in the above embodiments, the
same symbols as used in the figures as described above are used
without being redundantly described.
[0231] In the configuration in FIG. 9, an opening 10h is formed in
a part of the peripheral wall of the cylindrical vessel 10, for
discharging permeate gas passing through the hollow fiber membrane
to the outside of the cylindrical vessel. Likewise, in a part of
the peripheral wall of the cap 20, an opening 20h is formed at the
corresponding place. A hollow discharge pipe 41 is mounted such
that it passes through both openings 10h and 20h. In the gas
separation membrane module in FIG. 9, the permeate gas outlet 12 as
in FIG. 5 is not formed, since the discharge pipe 41 can serve as
the permeate gas outlet 12.
[0232] This discharge pipe 41 also can act as means for fixing the
cap 20 to the cylindrical vessel 10. That is, the discharge pipe 41
passes through both openings 10h and 20h, so that transfers in both
the axial and the rotational directions between the cap 20 and the
cylindrical vessel 10 are restricted.
[0233] To connect these members 10 and 20 more firmly, additional
fixing screw(s) 42 can be used as shown FIG. 9. The fixing screw 42
is screwed into a threaded hole formed in the peripheral wall of
the cap 20, and its tip in inserted into a part of the peripheral
wall of the cylindrical vessel 10. A female screw part, into which
the screw 42 is to be engaged, can be formed in the cap 20 or the
cylindrical vessel. A fixing pin can be used instead of the fixing
screw.
[0234] It is noted that there can be an annular sealing member (not
shown) for sealing between the inner surface of the peripheral wall
of the cap 20 and the outer surface of the cylindrical vessel 10.
It can ensure more reliable airtightness between the cap 20 and the
cylindrical vessel 10. However, such member can be omitted, if the
O-ring 18 can satisfactorily seal both between the tube sheet and
the cylindrical vessel and between the cap and the cylindrical
vessel.
[0235] In the configuration described above, the member 41 for
forming the channel for discharging permeate gas also acts as means
for fixing the cap 20 and the cylindrical vessel 10. Thus, the
module structure can be simplified, resulting in weight- and
size-reduction of the module.
[0236] The example shown in FIG. 9 has been described with
reference to the discharge pipe 41 for discharging permeate gas
passing through the hollow fiber membrane to the outside of the
cylindrical vessel. However, another tubular member forming a
channel communicating the inside with the outside of the
cylindrical vessel can be used, instead of the discharge pipe
41.
[0237] Alternatively, the cap 20 can be fixed to the cylindrical
vessel 10 only by fixing member such as the fixing screw 42 or
fixing pin, without using the discharge pipe 41 passing through the
openings 10h and 20h in the vessel and the cap. Such a
configuration is advantageous for size reduction of a module,
compared with the configuration of FIG. 10(b) where flanges are
fixed to each other as described later, since the flanges can be
omitted in the present configuration.
[0238] One or two or more fixing members can be used, and when two
or more members are used, the fixing members are preferably evenly
disposed in a circumferential direction.
Other Embodiments in Section C
[0239] The invention in this section can be, besides the
embodiments described above, as shown in FIGS. 10(a) and (b). Each
gas separation membrane module has, like the above embodiments, a
hollow fiber bundle 15 as a collection of a number of hollow fiber
membranes, a cylindrical vessel 10 housing the bundle, a tube sheet
30 at the end of the hollow fiber bundle 15 and caps (26, 27) at
the end of the cylindrical vessel. Furthermore, it has the O-ring
18 for sealing between the outer surface of the tube sheet and the
inner surface of the cylindrical vessel.
[0240] In the configuration in FIG. 10(a), the cap 26 is to be
fixed to the cylindrical vessel 10 by a screw system. Specifically,
in the configuration, a female screw formed in a part of the inner
surface of the cap 26 is to engage with a male screw formed in a
part of the outer surface of the cylindrical vessel 10. In the
state where the cap 26 is rotated to a predetermined position (see
FIG. 10(a), the O-ring 18 partially abuts on the inner surface of
the cap 26, ensuring airtightness between the cylindrical vessel
end and the cap inner surface. Like the above embodiments, the
O-ring 18 also ensures airtightness between the outer surface of
the tube sheet and the inner surface of the cylindrical vessel.
[0241] In the configuration of FIG. 10(b), a flange 27f is formed
in the cap 27, while a corresponding flange 10f is formed in the
cylindrical vessel 10. By connecting the flanges 27f and 10f with
fixtures 43, the cap 27 can be fixed to the cylindrical vessel 10.
The fixture 43 can be, for example, a bolt-nut system.
Alternatively, threaded hole formed in the flange 10f and bolt can
be used. There are no particular restrictions to positions where
flanges are tightened up by the fixtures 43, but the tightening
positions are preferably located at regular intervals in a
circumferential direction of the flange.
Further Embodiment in Section C
[0242] A gas separation membrane module of the invention in this
section can have a configuration as shown in FIG. 11. FIG. 11(a) is
a cross-sectional view showing an exemplary gas separation membrane
module, and FIG. 11(b) is an enlarged partial view of FIG.
11(a).
[0243] The gas separation membrane module in FIG. 11 has a hollow
fiber bundle 115 as a collection of hollow fiber membranes, a
cylindrical vessel 110 housing the bundle, tube sheets 130A, 130A
at both ends of the hollow fiber bundle 115 and caps 120, 121 at
the end of the cylindrical vessel 110. Furthermore, the module has
the O-ring 118 arranged on the outer surface of each tube sheet
130A.
[0244] The cylindrical vessel 110 of this example has a tubular
member 111 extending along the longitudinal direction of the
module, and end members 112, 112 attached at the each end of the
member 111. In the peripheral wall of the end member 112 in the
left side of the figure (gas inlet side), an outlet 112h for a
permeate gas (as an example) is formed.
[0245] Each end member 112 has a flange 112f. Meanwhile, the caps
120, 121 have flanges 120f, 121f, respectively. By engaging the
flange 112f of the end member with the flange 120f of the cap,
using for example bolt-nut system (not shown in FIG. 11) as
illustrated in FIG. 10, the cap 120 can be fixed to the end member
112 (a similar configuration can be applicable to the cap 121).
[0246] As shown in FIG. 11(b), in this example, the tube sheet 130A
is arranged such that it is firmly contacted to both a part of the
inner surface of the cap 120 and a part of the inner surface of the
cylindrical vessel 110. Each tube sheet 130A has an outer surface
formed as a step like the tube sheet 30' in FIG. 7, the step in the
outer surface of the tube sheet abuts on the step in the inner
surface of the cylindrical vessel, thereby the position of the tube
sheet 130A in an axial direction (lateral direction in the figure)
is secured.
[0247] Inside in the radial direction of the flange 120f of the cap
120, there is formed an annular step 120s. An O-ring 118 is
disposed within an annular groove, which has a rectangular cross
section formed by the step 120s and a part of the flange 112f in
the end member 112. The O-ring 118 contributes to ensure
airtightness not only between the tube sheet 130A and the cap 120
but also between the cap 120 and the end member 112.
[0248] Although a surrounding structure of the O-ring 118 has been
described with reference to the structure of the cap 120, the cap
121 side has a similar structure. Means for fixing a flange is not
limited to a bolt-nut system, but can be for example configuration
where a bolt tip is screwed into a threaded hole formed in either
the flange 112f or 120f.
[0249] According to the configuration as described for FIG. 11,
like the first embodiment, any step is not formed in the vicinity
of the position of the tube sheet 130A where the O-ring 118 is to
be mounted. Thus, it can be less influenced by stress concentration
when being used at high temperature than conventional structure as
shown in FIG. 6(b). As a result, resistance to the high temperature
and reliability can be improved in the gas separation membrane
module as a whole.
[0250] Furthermore, in the configuration in FIG. 11, the
cylindrical vessel 110 includes a tubular member 111 and the end
members 112, 112, and such a configuration is advantageous in that
material for each member can be appropriately selected depending on
the requirement of the members. It is noted that the invention in
this section is not limited to it, but a single cylindrical vessel
can be employed, in which for example the tubular member 111 and
the end member 112 are integrally combined.
[0251] Furthermore, other gas separation membrane module of the
invention in this section can be as shown in FIG. 12. In this
module, principally like the configuration in FIG. 10(b), the cap
127 is connected to the cylindrical vessel 110' in such a manner
that the flange 127f in the cap 127 abuts on the flange 110f in the
cylindrical vessel 110'. The number and the disposition of O-rings
are different from that in FIG. 10(b). The tube sheet 130B is
firmly contacted, like that in FIG. 11, to the parts of the inner
surfaces of the cap 127 and the cylindrical vessel 110'.
[0252] A first O-ring 118 is disposed within an annular groove 127g
formed in the inner surface of the cap 127, ensuring airtightness
between the tube sheet 130B and the cap 127. The annular groove
127g is formed, but not limited to, slightly inside (left side in
the figure) from the end face in the side of the flange 127f in the
inner surface of the cap 127.
[0253] A second O-ring 119 is disposed between the flange 110f and
the flange 127f. In this example, the O-ring 119 is disposed in the
annular groove 110g formed in the flange 110f in the cylindrical
vessel 110. The O-ring 119 is not an essential element, but it can
prevent the gas from leaking through the space between the flanges
110f and 127f.
[0254] Of course, such a configuration of the O-rings 118, 119 is
not limited to the embodiment illustrated in FIG. 12, but it can be
used in combination with the above embodiments as appropriate.
Furthermore, the groove in which the second O-ring 119 is disposed
can be formed in the flange 127f in the cap 127.
[0255] The invention related to section C is as follows.
[0256] [1] A separation membrane module used under high-temperature
conditions, comprising;
[0257] a hollow fiber bundle including a number of hollow fiber
membrane with selective permeability,
[0258] a cylindrical vessel housing the hollow fiber bundle,
[0259] a tube sheet placed at the end of the hollow fiber bundle,
which fixes the end of the bundle to the end of the cylindrical
vessel and separates the inside of the cylindrical vessel from the
outside, and
[0260] an annular sealing member for sealing between the outer
surface of the tube sheet and the inner surface of the cylindrical
vessel;
[0261] wherein there is not a step in the tube sheet on the
periphery of the place on which the annular sealing member is to be
mounted.
[0262] [2] A separation membrane module used under high-temperature
conditions, comprising;
[0263] a hollow fiber bundle including a number of hollow fiber
membrane with selective permeability,
[0264] a cylindrical vessel housing the hollow fiber bundle,
and
[0265] a tube sheet placed at the end of the hollow fiber bundle,
which fixes the end of the bundle to the end of the cylindrical
vessel and separates the inside of the cylindrical vessel from the
outside;
[0266] wherein the tube sheet is made of material having a larger
thermal expansion coefficient than that of material for the
cylindrical vessel, and
[0267] There is a gap between the outer surface of the tube sheet
and the inner surface of the cylindrical vessel at normal
temperature, whereas the tube sheet can expand by heating to a
predetermined temperature, so that its outer surface adheres
tightly to the inner surface of the cylindrical vessel to provide
sealing effect.
[0268] [3] A gas separation membrane module, comprising;
[0269] a hollow fiber bundle including a number of hollow fiber
membrane with selective permeability,
[0270] a cylindrical vessel housing the hollow fiber bundle,
[0271] a tube sheet placed at the end of the hollow fiber bundle,
which fixes the end of the bundle to the end of the cylindrical
vessel and separates the inside of the cylindrical vessel from the
outside, and
[0272] a cap at the end of the cylindrical vessel;
[0273] wherein a tubular member for forming a channel communicating
the inside with the outside of the cylindrical vessel penetrates a
part of the cylindrical vessel and a part of the cap along the
radial direction.
[0274] [4] The gas separation membrane module as described in [3],
comprising a fixing member which is to be inserted into a part of
the peripheral wall of the cap and which acts as means for fixing
the cap and the cylindrical vessel.
[0275] [5] A gas separation membrane module, comprising;
[0276] a hollow fiber bundle including a number of hollow fiber
membrane with selective permeability,
[0277] a cylindrical vessel housing the hollow fiber bundle,
[0278] a tube sheet placed at the end of the hollow fiber bundle,
which fixes the end of the bundle to the end of the cylindrical
vessel and separates the inside of the cylindrical vessel from the
outside, and
[0279] a cap at the end of the cylindrical vessel;
[0280] further comprising a fixing member, which is to be inserted
into a part of the peripheral wall of the cap, for fixing the cap
to the cylindrical vessel.
[0281] [6] A gas separation membrane module, comprising;
[0282] a hollow fiber bundle including a number of hollow fiber
membrane with selective permeability,
[0283] a cylindrical vessel housing the hollow fiber bundle,
[0284] a tube sheet placed at the end of the hollow fiber bundle,
which fixes the end of the bundle to the end of the cylindrical
vessel and separates the inside of the cylindrical vessel from the
outside,
[0285] a cap at the end of the cylindrical vessel, and
[0286] an annular sealing member for sealing between the outer
surface of the tube sheet and the inner surface of the cylindrical
vessel;
[0287] wherein the cap is fixed to the cylindrical vessel, by a
system
[0288] (i) using a thread formed in a part of the inner surface of
the cap and a thread formed in an opposite part of the outer
surface of the cylindrical vessel, or
[0289] (ii) binding a flange of the cap to a corresponding flange
of the cylindrical vessel using a fixture.
[0290] [7] The gas separation membrane module as described in any
of [3] to [6], wherein the annular sealing member further seals
between the cap and the cylindrical vessel.
Section D; Gas Separation Membrane Module Whereby which can be
Reduce a Replacement Cost and is Advantageous in Simplifying its
Structure
Technical Field
[0291] The invention disclosed in this section relates to a gas
separation membrane module for gas separation using a number of
hollow fiber membranes with selective permeability. In particular,
the invention relates to a separation membrane module which can
reduce replacement cost and is advantageous for simplifying its
structure.
Background Art
[0292] A hollow fiber type gas separation membrane module generally
has a hollow fiber element having a fiber bundle including a number
of hollow fiber membranes with selective permeability, and a
cylindrical vessel housing the element. One or both ends of the
hollow fiber bundle in the hollow fiber element is attached to the
end of a vessel by a resin cured plate (tube sheet). Capping
members are attached to the ends of the cylindrical vessel to seal
the inside of the vessel.
[0293] In conventional gas separation membrane module, as described
above, the cylindrical vessel and capping members attached to the
cylindrical vessel as a whole constitute a single case. Thus, when
the separation membrane module is replaced, the whole module must
be change. Therefore, capping members that are no need to be
changed are obliged to be replaced, leading to higher cost for a
replacement part.
[0294] On the other hand, it would be possible to make the hollow
fiber element in the case replaceable, but in such a configuration
for example, it is necessary to provide some structure allowing for
removal of the hollow fiber element, with inside of the case,
therefore module structure become more complex and may be
disadvantageous to weight reduction.
[0295] In view of the problems, an objective of the invention in
this section is to provide a gas separation membrane module which
can reduce a replacement cost, advantageous to simplifying a
structure and allow for easy size- and weight-reduction.
[0296] The summary of the main invention disclosed in this section
is as follows.
[0297] [1] A gas separation membrane module, comprising;
[0298] a cartridge housing a hollow fiber bundle including a number
of hollow fiber membranes in a cylindrical vessel,
[0299] capping members each of which is configured to be attached
to an end of said cartridge,
[0300] a sealing member for sealing between each of said capping
members and said cartridge, and
[0301] a fixture for fixing said capping members to each other,
[0302] wherein said cartridge is replaceably mounted between said
capping members.
[0303] According to such a configuration, there is provided a gas
separation membrane module which can reduce a replacement cost, is
advantageous to simplifying a structure and can be easily size- and
weight-reduced.
Embodiment in Section D
[0304] There will be described one embodiment of the invention in
this section with reference to the drawings. The invention in this
section is not limited to the following embodiment, but can be, if
necessary, modified, including addition or omission of a component
and change of a shape.
[0305] As shown in FIG. 13, a gas separation membrane module 201
(hereinafter, sometimes simply referred to as "separation membrane
module") has a cylindrical cartridge 210 housing a hollow fiber
bundle 215, capping members 220, 221 at both ends of the cartridge
and, for example, a fixing rod 245 for connecting these capping
members 220, 221 to each other.
[0306] The cartridge 210 includes a cylindrical vessel 211 with
open ends, the hollow fiber bundle 215, and tube sheets 230, 231.
The tube sheets 230, 231 hold the ends of the hollow fiber bundle
215 and separate the inside and the outside of the cylindrical
vessel 211.
[0307] The hollow fiber bundle 215 can be made of known structure.
The hollow fiber bundle 215 can be, for example, a collection of
about 100 to 1,000,000 hollow fiber membranes 214. There are no
particular restrictions to a material for the hollow fiber membrane
214 as long as the membrane can separate gases. For example, it is
suitably made of polymer material, which is glassy at normal
temperature (23.degree. C.) such as, in particular, polyimide,
polysulfone, polyetherimide, polyphenylene oxide and polycarbonate
which exhibits higher gas separation ability. There are no
particular restrictions to a shape of the collected hollow fiber
bundle, but in the light of easiness of production and pressure
resistance of a vessel, it can be hollow fiber bundle as a
cylindrical collection. FIG. 13 shows an embodiment in which hollow
fiber membranes 214 are disposed substantially in parallel,
however, these hollow fiber membranes can be cross-arranged.
[0308] The cylindrical vessel 211 can have any shape of cross
section such as circular, elliptic or polygonal. There will be
described a circular shape. The cylindrical vessel 211 can be
formed for example by processing a single metal pipe. In this
embodiment, it is preferable that, for example, fixing mechanism
for fixing the capping members 220, 221 to the cylindrical vessel
211 is not arranged in the cylindrical vessel 211 as a cartridge
(in other words, a structure where capping members are not to be
connected to the cylindrical vessel may be preferable). The
configuration can eliminate the necessity for processing the
cylindrical vessel 211 such as forming a flange, forming a threaded
hole and placing a fixing pin.
[0309] An inner groove 217 is formed near the end in the inside of
the cylindrical vessel 211, as shown in FIG. 14, where the inner
diameter is partially longer. A part of tube sheet 230, 231 is
configured to be fitted into the inner groove 217 as described
later. Another inner groove 218 is formed further inside from the
inner groove 217 by a predetermined distance (in a direction away
from the end). With respect to the inner grooves 217 and 218,
cross-sectional shape of the grooves may be any shape such as
rectangular, substantially rectangular, trapezoidal or
substantially trapezoidal.
[0310] Openings 212 for discharging gas from the vessel are formed
in the part where the inner groove 218 is formed. The number and
the positions of the openings 212 are not particularly limited. For
example, the openings 212 can be formed on the periphery of the
cylindrical vessel 211 at regular intervals. As shown in FIG. 14,
an outer annular groove 219 for elastic ring member R2 described
later is formed on the periphery of the tubular member 211 and
positioned slightly inwardly from the inner groove 218 (in a
direction away from the cylinder end).
[0311] Sealing members 230 and 231 (see FIG. 13) in the cartridge
210 are for example made of an epoxy resin and formed as a
substantially disc-shape to be fit into the end of the vessel 211.
Since the tube sheets 230 and 231 have a similar structure in
principle, there will be described only the tube sheet 230. Each
hollow fiber membrane 214 penetrates the tube sheet 230 along its
thickness direction, and the end of each hollow fiber membrane 214
is open at to the outside of the tube sheet 230. The tube sheet 230
adheres the hollow fiber membranes 214 together, and separates the
inside of the cylindrical vessel 211 from the outside. There are no
particular restrictions to a cured resin forming the tube sheet as
long as it is adequately durable and can ensure airtightness of the
inside of the hollow fiber module. The resin is also preferably
resistant to water vapor when being used for dehydrating or
moisturizing. In general, a thermosetting resin such as
polyurethane and an epoxy resin is suitably used. In the light of
durability and strength, an epoxy resin is particularly suitably
used. For a nitrogen membrane module, the epoxy resin for example
described in Japanese published examined application No. 1990-36287
can be used, whereas for an organic-vapor separation module the
epoxy resin for example described in WO 2009/044711 can be used.
The epoxy resin as disclosed in section B can also be used for the
tube sheet in the module of this section. The tube sheet can be
formed by known method such as centrifugal molding or stationary
molding.
[0312] It is noted that the term "separate" (e.g. separating the
inside of a cylindrical vessel from the outside by a tube sheet) as
used above means that substantial isolation by the tube sheet is
acceptable and the outer circumference of the tube sheet does not
necessarily have to adhere to the inner surface of the cylindrical
vessel.
[0313] As shown in FIG. 13, the part of the tube sheet 230 extrudes
from the end of the cylindrical vessel 211, and a chamfer (tapered
surface) is formed along the periphery of the end of the tube sheet
230. The tube sheet 230 can be formed by for example the following
process. First, for example a mold (not-shown) is attached to the
end of the cylindrical vessel 211, with the hollow fiber bundle 215
being disposed within the cylindrical vessel 211. Then, a resin is
injected into the mold and the cylindrical vessel 211, and then
cured. After the resin is cured, the mold is detached and the end
of the cured resin is cut to form the end face of the tube sheet
230 and to make the ends of the hollow fiber membranes 214 opened.
The chamfer in the tube sheet 230 can be formed by molding or by
secondary processing after resin curing.
[0314] Since the cylindrical vessel 211 has the inner groove 217,
the groove 217 is filled with the resin for the tube sheet 230.
Consequently, the part of the tube sheet 230 can engage with the
inner groove 217, so that the tube sheet 230 can be positioned
relative to the cylindrical vessel 211 in an axial direction.
Generally, during operation of the separation membrane module 201,
the pressure is applied to the tube sheet 230 in such a direction
that the member is pushed into the cylindrical vessel 211.
According to the configuration of this embodiment, the part of tube
sheet 230 engages with the inner groove 217. Therefore, the tube
sheet 230 can be prevented from moving into the cylindrical vessel
211 by pressure during operation.
[0315] Next, there will be described a structure of the capping
members 220, 221 with reference to FIGS. 13 and 15. Since the
capping members 220, 221 basically have a similar structure in this
example only the capping member 220 will be described, and for the
capping member 221 only different parts will be described. There
are no particular restrictions to materials for the capping members
220 and 221, however they can be for example made of metal. It is
noted that the capping members 220, 221 can have different shape
from each other, and the shapes of the capping members 220, 221 can
be appropriately changed depending on the application and
specifications of the separation membrane module.
[0316] As shown in FIGS. 13 and 15, the capping member 220 has a
bottomed cylindrical shape. Specifically, as shown in FIG. 15(A),
it has an end face 220A covering the opening of the cylindrical
vessel 211 and a cylindrical part 220B extending from the edge of
the end face.
[0317] The end face 220A has a gas inlet P1 for introducing mixed
gas. Inner grooves 227a, 227b are formed on the inside of the
cylindrical part 220B. An elastic ring member R1 (detailed below)
is to be fitted into the inner groove 227a as shown in FIG. 13. The
other inner groove 227b is for forming a gas channel P3 surrounding
the cylindrical vessel 211 when the capping member 220 is attached
to the cylindrical vessel 211. The other capping member 221 has a
non-permeate gas outlet P2.
[0318] The gas channel P3 (FIG. 13) communicates with the openings
212 of the cylindrical vessel 211, such that the gas in the vessel
flows into the gas channel P3 through each opening 212. The gas is
discharged to the outside via the outlet 223 formed in the
cylindrical part 220B in the cap. An element (opening)
corresponding to the outlet 223 is not formed in the capping member
221 in the configuration in FIG. 13, however, depending on, for
example, an application of the module, the opening can be formed in
the capping member 221, while in response to that, openings 212 can
be formed in the cylindrical vessel 211.
[0319] Again referring to FIG. 15, the cylindrical part 220B has
through-holes 220h through which fixing rod 245 (FIG. 13, detailed
below) is inserted respectively. Six through-holes 220h are
disposed at regular intervals in a circumferential direction in
this example. According to the configuration such as the
cylindrical part 220B has through-holes 220h through which the
fixing rod 245 is inserted, the following advantages can be
obtained. That is, in this configuration, since the cylindrical
part 220B as the part of the cap 220 holds the fixing rod 245,
there is no need to provide any special structure for holding the
fixing rod with the capping member 220. Therefore, the capping
member 220 and thus the separation membrane module 201 can be
size-reduced, contributing weight-reduction in the module.
[0320] It is noted that the number of the fixing rods 245 is not
limited to 6, but can be 1 to 5 or 7 or more. For example, as shown
in FIG. 16, it can be 3, 4 or 8. The fixing rod 245 can be, for
example, made of, but not limited to, a metal.
[0321] As shown in FIG. 15(B), a flat part 220f is formed on the
part of the cylindrical part 220B where the outlet 223 opens, by
cutting the part of the cylindrical part 220B. Furthermore, in the
bottom of the cylindrical part 220B, for example, a flat part 220g
for preventing the separation membrane module from rolling is
formed.
[0322] An elastic sealing member R1 for sealing between the tube
sheet 230 and the capping member 220 is fitted in the inner groove
227a of the capping member as shown in FIG. 13. The elastic ring
member R1 is configured such that it remains on the inside of the
capping member 220 when the cartridge 210 is detached from the
capping member 220 for replacement. The elastic ring member R1 can
be, for example, an O-ring (substantially circular cross section).
Alternatively, it can be a V- or U-packing with a substantially V-
or U-shaped cross section, respectively. Furthermore, its cross
section can be elliptic, rectangular, polygonal or X-shaped.
[0323] Another elastic ring member R2 is disposed between the
cylindrical vessel 211 and the cylindrical part 220B, such that it
is fitted into the periphery groove 219 of the cylindrical vessel
211, to seal between these members. The elastic ring member R2 can
be also selected from a various types such as an O-ring, a
V-packing and a U-packing as described above.
[0324] As shown in FIGS. 13 and 15, the capping members 220, 221
are connected to each other with six (for example) fixing rods 245
and nuts 246 mounted on both ends. In this embodiment, it is the
fixtures as separate components from the cartridge 210 that connect
the capping members 220, 221. Therefore, there is no need to
provide any structure such as flanges with the cartridge 210
(particularly, the tubular member 211), resulting in simplifying
the structure of the cartridge 210.
[0325] There are no particular restrictions to a fixture for fixing
the capping members 220, 221, but it can be selected from various
types. For example, one end of the fixing rod can be a head with a
larger diameter, while the other end can receive a nut.
Alternatively, the inner circumference of the through-hole 220h of
the inner capping member 220 can be threaded, while in response to
that, the rod end can be also threaded, so that the rod end is to
be screwed into the through-hole 220h. Alternatively, mechanisms
for mechanically binding and fixing capping members can be used;
such as a mechanism for fixing the module by clamping both ends of
the module (capping members 220, 221).
[0326] In addition, such mechanisms are not limited to the ones for
connecting capping members 220, 221 to each other. Instead,
mechanism for securing each capping members 220, 221 to a
predetermined fixing position can be used, in which the cartridge
210 is removably mounted between the capping members 220 and 221.
For example, a particular configuration can be employed, where some
part of an apparatus or facility on which the separation membrane
module is to be mounted is configured to serve as a base member
(not shown), and each of the capping members 220, 221 can be fixed
to the base member.
[0327] In the separation membrane module 201 of this embodiment,
for example, gas separation is conducted as follows. A pressurized
air is introduced into the inside of the vessel through the gas
inlet P1, and the air is fed into the inside of the hollow fiber
membrane 214 via the open end. While the pressurized air flows in
the the hollow fiber membrane 214, an oxygen-rich air selectively
permeates toward the outside of the membrane, and the permeating
oxygen-rich air moves into the space where the hollow fiber bundle
between tube sheets is mounted. The permeate gas is discharged from
openings 212 and 223 as permeate gas outlets. On the other hand,
the non-permeating nitrogen-rich air is discharged, through the
other opening in the hollow fiber membrane 214, from the
non-permeate gas outlet P2 as non-permeate gas outlet.
[0328] According to the gas separation membrane module 201
described above, it has the configuration in which the cartridge
210 housing the hollow fiber bundle 215 is to be mounted between
the capping members 220, 221. Thus, the module can be replaced only
by changing the cartridge without changing the whole module,
therefore cost for the replacement part can be reduced.
[0329] On the other hand, a structure may be adopted in which only
the inner components corresponding to the hollow fiber element 215,
however, it is necessary to design a structure for
mounting/removing the replaceable component within the cylindrical
vessel 211 in this case. In contrast, according to the module 201,
complex structures are not required, since the cylindrical vessel
211 (as a part of the cartridge 210) itself can serve as the case
for the module 201. This is advantageous in weight reduction for
the whole separation membrane module 201, particularly suitably
applicable to a field needing weight reduction of the module such
as aeronautical field.
[0330] Furthermore, according to the above configuration, the
capping members 220, 221 are coupled by fixture (245, 246) as
separate component from the cartridge 210. It is, therefore, not
necessary to provide structure(s) for coupling the capping member
with the cylindrical vessel 211 (for example, a flange). Thus, a
structure of the cartridge 210 can be simplified and a production
cost can be reduced.
[0331] According to the above configuration, the elastic ring
member R1 is set on the inner circumference of the capping member
220, 221 such that the ring member R1 remains in the capping member
side when the cartridge 210 is removed during replacement. Such a
configuration is advantageous to saving production cost for the
cartridge 210 compared with forming the ring member R1 in the side
of the cartridge 210.
[0332] As shown in FIG. 13, in the configuration of this
embodiment, the chamfer (tapered surface) is formed along the
periphery of the end of the tube sheet 230, therefore, the end of
the tube sheet 230 can be smoothly inserted into the elastic ring
member R1.
[0333] The embodiments of this invention in this section have been
described with reference to the drawings, however, there can be
various modifications of the invention in this section in addition
to that illustrated in the drawings. For example, the shape and the
position of a sealing member for sealing between members can be
appropriately changed. In addition to the elastic ring members R1,
R2, additional sealing member can be used.
[0334] Although there has been illustrated a configuration in which
the elastic ring member R2 is fitted into the periphery of the
cylindrical vessel 211 in the above embodiment as shown in FIG. 13,
the invention of this section is not limited to that, but can be a
configuration in which the elastic ring member R2 is disposed in
the inner circumference of the capping member 220, 221 and during
replacement of a cartridge, the elastic ring member R2 is to remain
in the side of the capping member 220, 221. It can eliminate the
necessity of forming the periphery groove 219 in the cylindrical
vessel 211 in the cartridge 210, resulting in further reducing a
production cost for the cartridge 211.
[0335] Although the examples of separation membrane modules
constituting a so-called bore feed type in the above embodiment,
the invention in this section can be applied to the separation
membrane module constituting a shell feed type. In such a case, a
configuration can be employed in which the cartridge suitable to a
shell feed type is replaceably mounted between the capping members
as described above.
[0336] The inventions according to section D are as follows.
[0337] [1] A gas separation membrane module, comprising;
[0338] a cartridge housing a hollow fiber bundle including a number
of hollow fiber membranes in a cylindrical vessel,
[0339] capping members each of which is configured to be attached
to both end of said cartridge,
[0340] a sealing member for sealing between each of said capping
members and said cartridge, and
[0341] a fixture for fixing said capping members to each other,
[0342] wherein said cartridge is replaceably mounted between said
capping members.
[0343] [2] The gas separation membrane module as described in [1],
wherein
[0344] said fixture has at least one fixing rod coupling said
capping members, and
[0345] each capping member has a through-hole into which said
fixing rod is inserted.
[0346] [3] The gas separation membrane module as described in [1]
or [2], wherein
[0347] said capping member is mounted such that it covers the end
of said cylindrical vessel, and
[0348] said sealing member is an elastic ring member configured to
be disposed between the periphery of said cartridge and the inner
circumference of said capping member.
[0349] [4] The gas separation membrane module as described in [3],
wherein said elastic ring member is to be held in the inner
circumference of said capping member, and is configured to remain
in the side of said capping member when said cartridge is removed
from said capping member for replacement.
[0350] [5] The gas separation membrane module as described in any
of [1] to [4], wherein
[0351] said cartridge has a tube sheet holding the end of said
hollow fiber bundle, for separating the inside of said cylindrical
vessel from the outside,
[0352] an inner groove is formed in a region within said
cylindrical vessel and facing said tube sheet, and
[0353] a part of said tube sheet engages with said inner
groove.
Section E: Gas Separation Membrane Module Capable of More
Efficiently Separating Gases
Technical Field
[0354] The invention in this section relates to a gas separation
membrane module for separating gases with a hollow fiber membrane,
in particular a gas separation membrane module which can more
efficiently separate gases in a so-called bore feed type
module.
Background Art
[0355] A hollow fiber type gas separation membrane module generally
has a hollow fiber element including a hollow fiber bundle
comprising a number of hollow fiber membranes with selective
permeability and a hollow casing housing the element. Both ends or
one end of the hollow fiber bundle in the hollow fiber element are
fixed by resin-cured plate (tube sheet). Furthermore, the casing
has a mixed gas inlet, a permeate gas outlet and a non-permeate gas
outlet.
[0356] For the purpose of efficient gas separation, for example,
Japanese published unexamined application No. 2000-262838 discloses
a gas separation membrane as a so-called bore feed type module in
which mixed gas is fed into hollow fiber membranes, wherein a part
of the hollow fiber bundle is covered by a film member, so that the
carrier gas outside of the hollow fiber membranes and the mixed gas
inside of the membranes flow countercurrently.
[0357] According to the above gas separation membrane module in No.
2000-262838, the flow direction of the carrier gas can be regulated
to achieve more efficient gas separation, however, it is important
to improve an efficiency of gas separation even in the bore feed
type modules without using a carrier gas (purge gas). In view of
the above problem, an objective of the invention in this section is
to provide a bore feed type gas separation membrane module which
can more efficiently separate gases.
[0358] The summary of the main invention disclosed in this section
is as follows.
[0359] [1] A gas separation membrane module comprising;
[0360] a hollow fiber bundle as a collection of a number of hollow
fiber membrane with gas separation ability,
[0361] a casing having a mixed gas inlet, a permeate gas outlet and
a non-permeate gas outlet, in which said hollow fiber bundle is
disposed, and
[0362] two tube sheets for fixing both ends of said hollow fiber
bundle,
[0363] in which mixed gas from said mixed gas inlet is fed into
said hollow fiber membrane, while the mixed gas partly permeates
the membrane, to achieve gas separation,
[0364] wherein,
[0365] (i) a structure for feeding purge gas is not provided, said
purge gas is for purging permeate gas from hollow fiber membrane,
and
[0366] (ii) the module further comprising, a gas-impermeable film
member wrapped around the outer surface of said hollow fiber
bundle, in which one end substantially abuts on said tube sheet in
the downstream side along the mixed-gas feeding direction, whereas
the other end is disposed away from the tube sheet in the upstream
side in the mixed-gas feeding direction.
[0367] According to the invention in this section the film member
wrapped around the hollow fiber bundle regulates feeding of a
permeate gas in a direction opposite to a direction of feeding a
mixed gas (detailed later), therefore gas separation can be more
efficiently conducted in the bore feed type module.
Embodiment in Section E
[0368] There will be described one embodiment of the invention in
this section with reference to the drawings. FIG. 17 is a
cross-sectional view schematically showing a basic configuration of
a gas separation membrane module according to this embodiment.
[0369] A gas separation membrane module 601 as shown in FIG. 17 is
of the bore feed type, which has a hollow fiber bundle 615 as a
collection of a number of hollow fiber membranes 614, a casing 610
housing the bundle, and tube sheets 621 and 622 at both ends of the
hollow fiber bundle 615.
[0370] The hollow fiber membrane 614 can be made of any known
structure as long as it has gas separation ability. For example, it
is suitably made of polymer material which is glassy at normal
temperature (23.degree. C.) such as, in particular, polyimide,
polysulfone, polyetherimide, polyphenylene oxide and polycarbonate
for their gas separation ability.
[0371] The hollow fiber bundle 615 can be, for example, a
collection of about 100 to 1,000,000 hollow fiber membranes 614.
There are no particular restrictions to the shape of the collected
hollow fiber bundle 615, but for example, the cylindrical shape is
preferable in the light of easiness in production and pressure
resistance of a vessel. FIG. 17 shows an embodiment in which hollow
fiber membranes 614 are disposed substantially in parallel,
however, these hollow fiber membranes can be cross-arranged.
[0372] There are no particular restrictions to mixed gas to be
subjected to separation by the hollow fiber membrane 614, but it
can be, for example, a mixed gas of a more permeable gas and a less
permeable gas with a ratio of permeation rates to a separation
membrane of 2 or more. The gas separation membrane module 601 of
this embodiment can be use for separating a particular gas
component from a mixed gas in various manners. For example, it can
be used for drying a variety of gases, humidification of a variety
of gases, nitrogen enrichment or oxygen enrichment.
[0373] The tube sheets 621, 622 are formed as a disc-shape in
response to the cross-sectional shape of the casing, and they hold
the end of the hollow fiber bundle 615 with each hollow fiber
membrane 614 opened. The tube sheets 621, 622 can be made of a
thermoplastic resin such as polyethylene and polypropylene or a
thermosetting resin such as an epoxy resin and a urethane resin.
The tube sheets 621, 622 have a function of bundling the hollow
fiber membranes 614 together. It also has a function of sealing
between the hollow fiber membranes 614 as well as between the
hollow fiber bundle 615 and the inner surface of the casing 610. As
shown in FIG. 17, a closed space 618 (as described later, having a
permeate gas outlet 610c) is formed by the casing 610 and two tube
sheets 621 and 622, into which the permeate gas from the hollow
fiber membrane 614 is to be introduced. A mixed gas space 619a is
formed by the casing 610 and the tube sheet 621, while a
non-permeate gas space 619b is formed by the casing 610 and the
tube sheet 622. Other sealing means can be installed for sealing
between the tube sheets 621, 622 and the inner surface of the
casing 610.
[0374] For a nitrogen membrane module, the epoxy resin for example
described in Japanese published examined application No. 1990-36287
can be used for the tube sheet 621, 622, whereas for an
organic-vapor separation module the epoxy resin for example
described in WO 2009/044711 can be used. The epoxy resin as
disclosed in section B can also be used for a tube sheet in the
module of this section
[0375] As shown in FIG. 17, the casing 610 is substantially
cylindrical as a whole. The casing 610 has a mixed gas inlet 610a
in the upstream side (left side in the figure) for introducing
mixed gas into the casing 610, a non-permeate gas outlet 610b in
the downstream side (right side in the figure), and a permeate gas
outlet 610c in its side wall. The number of the permeate gas outlet
610c can be one or two or more. Permeate gas outlets 610c can be
disposed at regular intervals along the side wall of the casing
610. The permeate gas outlet 610c is, in this example, placed at
the position near the upstream tube sheet 621 (specifically, the
position of exposed part A1 in the hollow fiber bundle 615 without
a film member 631 described later).
[0376] The mixed gas introduced from the mixed gas inlet 610a
enters into each hollow fiber membrane 614 via the end face of the
tube sheet 621 and flows downstream in the inside. A part of the
mixed gas permeates the hollow fiber membrane 614 and the permeate
gas is fed into the inside of the closed space 618 and then
discharged from the casing through the permeate gas outlet 610c. On
the other hand, a non-permeate gas not permeating the hollow fiber
membrane as it is flows downstream in the hollow fiber membrane 614
and flows outward from the end face, and then is discharged out of
the casing through the non-permeate gas outlet 610b.
[0377] Although FIG. 17 schematically shows the casing 610, the
casing can have a configuration as shown in FIG. 19. The casing 610
in this example has a cylindrical member 611 with open ends and
caps 612, 613 attached to the ends. The tubular member 611 and the
caps 612, 613 can be, for example, made of a metal, a plastic or a
ceramic. A mixed gas inlet 610a and a non-permeate gas outlet 610b
are formed in the caps 612 and 613, respectively. For example, the
mixed gas inlet 610a and the non-permeate gas outlet 610b can be
formed at the center of the caps 612, 613 (center seen from a front
of the cap), respectively.
[0378] A film member 631 is wrapped around the periphery of the
hollow fiber bundle 615, as shown in FIGS. 17 and 18, in the gas
separation membrane module 601 of this embodiment. The end 631a of
the film member 631 substantially abuts on the tube sheet 622,
while the other end 631b is disposed away from the tube sheet 621
by a predetermined distance. The region of hollow fiber bundle 615,
which is not covered by the film member 631, is indicated by symbol
A1 (exposed part) in FIG. 17. The film member 631 can cover 50% to
95%, preferably 75% to 92% of the outer surface of the hollow fiber
bundle. Alternatively, the film member 631 may cover the whole
surface of the hollow fiber bundle so that each end of the film
member are close to each tube sheet, and one or multiple openings
are formed on the film member 631 in the vicinity of the tube sheet
621.
[0379] The phrase, (an end of a film member) "substantially abut"
means both that (i) the film end completely abuts on the tube
sheet, and that (ii) the film end is close to the tube sheet with a
small gap between the film end and the tube sheet due to
convenience in production for example. When the tube sheet is made
of an epoxy resin or the like and the film end is inserted in the
tube sheet (for example, a case in which the film end is inserted
in the tube sheet material and then the tube sheet is cured), the
tube sheet may be cracked or damaged beginning at the part. Thus it
may be preferable to arrange the film so that the end is not
inserted into the tube sheet.
[0380] The film member 631 can be made of any material as long as
the material is substantially gas-impermeable. The term
"substantially gas-impermeable" means that: the gas permeability of
the film member 631 is low enough to limit gas flow. For example,
it can be a plastic film such as polyimide, polyethylene,
polypropylene, polyamide and polyester. Among these, polyimide is
preferable in the light of heat resistance, solvent resistance and
processability. In addition to a plastic film, a metal foil such as
aluminum and stainless steel can be used. A thickness of the film
can be in the range of several ten .mu.m to several mm. The film
member 631 can be formed by attaching both side edges of the sheet
to form cylindrical shape, or the film member 631 can be of a
seamless tubular member. Side edges of the film can be attached by
for example adhesive material or tape.
[0381] If the module does not has the film member 631, permeate gas
from the hollow fiber membrane 614 flows in a cross-flow direction
as shown by arrow f3 in FIG. 18 (i.e. a direction crossing the
hollow fiber membrane 614). On the other hand, when the film member
631 is wrapped on the hollow fiber bundle 615 as in this
embodiment, diffusion of the permeate gas is prevented and thus the
permeate gas flows along the countercurrent direction f2 to the
direction of mixed gas feeding f1.
[0382] There will be described an exemplary method for using the
separation membrane module of this embodiment constructed as
described above. A method for using the module according to
embodiment is not limited to the following example.
[0383] First, a mixed gas is introduced through the mixed gas inlet
610a into the mixed gas space 619a within the casing 610. The
introduced mixed gas enters each hollow fiber membrane 614 from the
end face of the tube sheet 621, and flows downstream inside of the
membrane. It is preferable that pressure within the hollow fiber
membrane 614 is higher than that of the closed space 618,
specifically, it is suitable that the mixed gas is fed at a
pressure of 0.01 MPaG to 10 MPaG whereas the closed space 618 is
vacuumed. A part of the mixed gas selectively permeates the hollow
fiber membrane 614 during this operation, and is then discharged
into the closed space 618 outside of the hollow fiber membrane 614.
On the other hand, the non-permeable gas flows downstream as it is
within the hollow fiber membranes 614 and then discharged to the
non-permeate gas space 619b outside of the hollow fiber membranes
614 from the end face downstream.
[0384] The permeate gas from the hollow fiber membrane 614 is then
introduced into the closed space 618 in the casing 610. The film
member 631 prevents the permeate gas from diffusing in the region
wrapped with the film member 631, as shown in FIG. 18, thus the
permeate gas flows along the direction of the arrow f2 opposite to
the direction of feeding the mixed gas f1. The permeate gas is then
discharged out of the casing 610 through the permeate gas outlet
610c (see FIG. 17). The non-permeate gas is released from the
downstream end of the hollow fiber membrane 614 and then discharged
outside via the non-permeate gas outlet 610b.
[0385] According to the separation membrane module 601 described
above, the film member 631 can prevent the permeate gas from
diffusing and enables the permeate gas to flow along the direction
opposite to the direction of feeding a mixed gas. Thus, gas
separation efficiency can be improved.
[0386] The inventions according to section E are as follows.
[0387] [1] A gas separation membrane module comprising;
[0388] a hollow fiber bundle as a collection of a number of hollow
fiber membrane with gas separation ability,
[0389] a casing having a mixed gas inlet, a permeate gas outlet and
a non-permeate gas outlet, in which said hollow fiber bundle is
disposed, and
[0390] two tube sheets for fixing both ends of said hollow fiber
bundle,
[0391] in which mixed gas from said mixed gas inlet is fed into
said hollow fiber membrane, while the mixed gas partly permeates
the membrane, to achieve gas separation,
[0392] wherein,
[0393] (i) a structure for feeding purge gas is not provided, said
purge gas is for purging permeate gas from hollow fiber membrane,
and
[0394] (ii) the module further comprising, a gas-impermeable film
member wrapped around the outer surface of said hollow fiber
bundle, in which one end substantially abuts on said tube sheet in
the downstream side along the mixed-gas feeding direction, whereas
the other end is disposed away from the tube sheet in the upstream
side in the mixed-gas feeding direction.
[0395] [2] The gas separation membrane module as described in [1],
wherein said one end of the film member is configured not to be
inserted into said tube sheet.
[0396] [3] The gas separation membrane module as described in [1]
or [2], wherein said permeate gas outlet is formed in a part of
said casing, the part surrounding an exposed area of said hollow
fiber bundle where the bundle is not covered by said film
member.
[0397] [4] The gas separation membrane module as described in any
of [1] to [3], wherein said film member covers 50% to 95% of the
outer surface of said hollow fiber bundle in the region between the
one tube sheet and the other tube sheet.
[0398] [5] The gas separation membrane module as described in any
of [1] to [4], wherein said film member is made of polyimide.
Section F: Gas Separation Membrane Module in which Gas Leakage from
a Gap Between a Film End and a Tube Sheet is Prevented
Technical Field
[0399] The invention in this section relates to a gas separation
membrane module for gas separation using hollow fiber membranes, in
particular, to a bore feed type gas separation membrane module
which can prevent gas leakage from a gap between a film end and a
tube sheet to achieve more efficient gas separation.
Background Art
[0400] A hollow fiber type gas separation membrane module generally
has a hollow fiber element having a hollow fiber bundle including a
number of hollow fiber membranes with selective permeability and a
hollow casing housing the element. Both ends or one end of the
hollow fiber bundle in the hollow fiber element are fixed by a
resin-cured plate (tube sheet). The casing has a mixed gas inlet, a
permeate gas outlet and a non-permeate gas outlet.
[0401] For the purpose of efficient gas separation, for example,
Japanese published unexamined application No. 2000-262838 discloses
a gas separation membrane as a so-called bore feed type module in
which a mixed gas is fed into hollow fiber membranes, wherein a
part of the hollow fiber bundle is covered by a film member and
carrier gas outside of the hollow fiber membranes and the mixed gas
in side of the membranes flow counter currently.
[0402] In the above gas separation membrane module in the reference
document, the flow direction of the carrier gas can be regulated to
achieve more efficient gas separation, however, it is important to
improve an efficiency of gas separation even in a module without
using carrier gas (purge gas). To improve the efficient of gas
separation, it is effective to prevent gas from leaking through the
gap between the film end and the tube sheet (detailed later)
whether purge gas is used or not.
[0403] In view of the above problem, an objective of this section
is to provide a bore type gas separation membrane module capable of
separating gases by preventing gas leakage from a gap between a
film end and a tube sheet.
[0404] The summary of the main invention disclosed in this section
is as follows.
[0405] [1] A gas separation membrane module comprising;
[0406] a hollow fiber bundle as a collection of a number of hollow
fiber membrane with gas separation ability,
[0407] a casing having a mixed gas inlet, a permeate gas outlet and
a non-permeate gas outlet, in which said hollow fiber bundle is
disposed, and
[0408] two tube sheets for fixing both ends of said hollow fiber
bundle,
[0409] a gas-impermeable (including substantially gas-impermeable)
film member wrapped around the outer surface of said hollow fiber
bundle, in which one end substantially abuts on said tube sheet in
the downstream side along the mixed-gas feeding direction, whereas
the other end is disposed away from said tube sheet in the upstream
side in the mixed-gas feeding direction, and
[0410] a sealing structure sealing a gap between said one end of
the film member and said tube sheet.
[0411] According to the invention in this section, there can be
provided a bore type gas separation membrane module capable of
separating gases by preventing gas leakage from a gap between a
film end and a tube sheet.
Embodiments in Section F
[0412] There will be described one embodiment of the invention in
this section with reference to the drawings. FIG. 21 shows the
shape of a casing (detailed later) more specifically as an
example.
[0413] A gas separation membrane module (hereinafter, simply
referred to as "module") 801 shown in FIGS. 20 and 21 has a hollow
fiber bundle 815 as a collection of a number of hollow fiber
membranes 814, a casing 810 housing the bundle, and tube sheets
821, 822 at the ends of the hollow fiber bundle 815. This module
801 is of a so-called bore feed type, where the mixed gas (source
gas) is fed into the hollow fiber membrane 814.
[0414] The hollow fiber membrane 814 can be made of any of known
structure as long as it has gas separation ability. For example, it
is suitably made of polymer material, which is glassy at normal
temperature (23.degree. C.) such as, in particular, polyimide,
polysulfone, polyetherimide, polyphenylene oxide and polycarbonate
for the gas separation ability.
[0415] The hollow fiber bundle 815 can be, for example, a
collection of about 100 to 1,000,000 hollow fiber membranes 814.
There are no particular restrictions to the shape of the collected
hollow fiber bundle 815, however, a cylindrical shape is preferable
in the light of easiness in production and pressure resistance of a
vessel. Although FIG. 20 shows an embodiment in which hollow fiber
membranes 814 are disposed substantially in parallel, these hollow
fiber membranes can be cross-arranged.
[0416] There are no particular restrictions to a mixed gas to be
subjected to separation by the hollow fiber membrane 814, however
it can be, for example, a mixed gas of a more permeable gas and a
less permeable gas with a ratio of permeation rates to a separation
membrane of 2 or more. The gas separation membrane module 801 of
this embodiment can be use for separating a particular gas
component from a mixed gas in various manners. For example, it can
be used for drying a variety of gases, humidification of a variety
of gases, nitrogen enrichment or oxygen enrichment.
[0417] The tube sheets 821, 822 are formed substantially as a
disc-shape in response to the shape of the casing 810, and fix the
end of the hollow fiber bundle 815 with each hollow fiber membrane
814 opened. The tube sheets 821, 822 can be made of a thermoplastic
resin such as polyethylene and polypropylene or a thermosetting
resin such as an epoxy resin and a urethane resin. The tube sheets
821, 822 have a function of bundling the hollow fiber membranes 814
together. It also has a function of sealing between the hollow
fiber membranes 814 as well as between the hollow fiber bundle 815
and the inner surface of the casing 810. As shown in FIG. 20, a
closed space 818 (as described later, having a permeate gas outlet
810c) is formed by the casing 810 and two tube sheets 821 and 822,
the permeate gas from the hollow fiber membrane 814 is to be
introduced into the closed space 818. A mixed gas space 819a is
formed by the casing 810 and the tube sheet 821, whereas a
non-permeate gas space 819b is formed by the casing 810 and the
tube sheet 822. Another sealing means can be used for sealing
between the tube sheets 821, 822 and the inner surface of the
casing 810.
[0418] For a nitrogen membrane module, the epoxy resin for example
described in Japanese published examined application No. 1990-36287
can be used for the tube sheet 821, 822, whereas for an
organic-vapor separation module the epoxy resin for example
described in WO 2009/044711 can be used. The epoxy resin as
disclosed in section B can also be used for a tube sheet in the
module of this section
[0419] The casing 810 is substantially cylindrical as a whole as
shown in FIG. 20. The casing 810 has a mixed gas inlet 810a for
introducing a mixed gas into the casing 810 in the upstream side
(left side in the figure), a non-permeate gas outlet 810b in the
downstream side (right side in the figure) and a permeate gas
outlet 810c in its side wall. The number of the permeate gas outlet
810c can be one or two or more. The permeate gas outlets 810c can
be disposed at regular intervals along the side wall of the casing
810. The permeate gas outlet 810c in this example is formed at the
position near the upstream tube sheet 821 (specifically, the
position of exposed part A1 in the hollow fiber bundle 815 without
a film member 831 described later).
[0420] The mixed gas introduced from the mixed gas inlet 810a is
fed into each hollow fiber membrane 814 from the end face of the
tube sheet 821, and flows downstream in the inside of the membrane.
A part of the mixed gas permeates the hollow fiber membrane 814,
and the permeate gas is fed to the inside of the closed space 818
and then discharged from the casing through the permeate gas outlet
810c. On the other hand, a non-permeate gas not permeating the
hollow fiber membrane as it is flows downstream in the hollow fiber
membrane 814 and flows outward from the end face, and then is
discharged out of the casing through the non-permeate gas outlet
810b.
[0421] The mixed gas inlet 810a and/or the non-permeate gas outlet
810b can be disposed in such a way that their central axes are
aligned with the central axis of the casing 810 (that is, the
central axis of the hollow fiber bundle 815). The casing 810 can
have a cylindrical member 811 and retaining members 813 for hold
the tube sheet at its ends (one is not shown) as in the example in
FIG. 21(A). The tubular member 811 and the retaining member 813 can
be welded to each other. The inner surface of the retaining member
813 in this example has a straight part 813a with a constant
diameter, a large diameter part 813b with a larger diameter than
the straight part 813a, and a tapered part 813c with a gradually
reduced diameter. The tube sheet 822 has as shown in FIG. 21(A) a
hollow-fiber-membrane burying part 822a into which the part of
hollow fiber membrane 814 is placed, and a surrounding part 822b in
which the hollow fiber membrane 814 does not exist.
[0422] A film member 831 is wrapped around the peripheral surface
of the hollow fiber bundle 815 in the gas separation membrane
module 801 of this embodiment as shown in FIGS. 20 and 21. One end
831a of the film member 831 (hereinafter, also referred to as "film
end 831a") is close to the tube sheet 822, whereas the other end
831b is disposed away from the tube sheet 821 by a predetermined
distance. In FIG. 20, the region of hollow fiber bundle 815, which
is not covered by the film member 831, is indicated by symbol A1
(exposed part). The film member 831 can cover 50% to 95%,
preferably 70% to 92% of the outer surface of the hollow fiber
bundle. Alternatively, the member can cover the whole surface of
the hollow fiber bundle so that each end of the film member 831 is
close to each tube sheet, and the film member 831 can has one or
multiple openings in the vicinity of the tube sheet 821.
[0423] The film member 831 can be made of any material as long as
the material is substantially gas-impermeable. The term
"substantially gas-impermeable" means that: the gas permeability of
the film member 631 is low enough to limit gas flow. For example,
it can be a plastic film such as polyimide, polyethylene,
polypropylene, polyamide and polyester. Among these, polyimide is
preferable in the light of heat resistance, solvent resistance and
processability. In addition to a plastic film, a metal foil such as
aluminum and stainless steel can be used. A thickness of the film
can be in the range of several ten .mu.m to several mm.
[0424] The film member 831 can be formed by attaching both side
edges of a film to form the cylindrical shape, or the member 631
can be of a seamless tubular member. The edges of the film can be
attached for example by adhesive material or tape.
[0425] If the tube sheet is epoxy resin and the film end is buried
in the tube sheet (e.g. a case in which the film end is inserted
into the material and then cured), the tube sheet may be cracked or
damaged beginning at the part. To avoid this, the film end is not
buried in the tube sheet in this embodiment. In this configuration,
however, a gap A31 might be formed between the film end 831a and
the tube sheet 822 as shown in FIG. 21 (for illustrative purposes,
the size of the gap A31 is exaggerated).
[0426] A sealing structure 850 for sealing the gap A31 between the
film end 831a and the tube sheet 822 is provided as shown in FIGS.
20 and 21 in this embodiment. The sealing structure 850 in this
example has two cylindrically formed sealing parts 851 and 853 (see
FIG. 21), which are disposed on both surfaces of the film to
sandwich the film 831a and wrap the hollow fiber bundle 815.
[0427] Both sealing parts 851, 853 are made of material into which
liquid resin material such as epoxy resin can permeate, that is,
the material having a predetermined capillary force. The sealing
parts 851, 853 can be made of any material as long as it has such
feature, thus for example a mesh member formed by interweaving
fibers, such as cloth or net can be used. The fiber can be, for
example, a chemical or natural fiber, and a glass fiber or a carbon
fiber can be used.
[0428] As shown in FIG. 21, the first sealing part 851 is disposed
on the outer surface of the film member 831, whereas the second
sealing part 853 is disposed on the inner surface of the film
member 831. Each of the sealing parts 851, 853 is disposed such
that it extends from the film end 831a toward the side of the tube
sheet 822. A part of the extension of each of the sealing parts
851, 853 is buried in the intact part 822b in the tube sheet
822.
[0429] A fixing tape 855 is attached to the sealing part 851 to fix
the part 851 to the film member 831 as shown in FIG. 21(A). The
fixing tape 855 can be applied for example such that it surrounds
the outer circumference of the hollow fiber bundle 815. The fixing
tape 855 can also be wrapped around the fixing tape 855 twice or
more. Instead, the tape 855 can be applied only on a part of the
outer circumference.
[0430] An overlap portion of the sealing parts 851, 853 can be
fixed to each other by a fixture 857 as shown in FIG. 21(B). The
fixture 857 can be a mechanism for mechanically fixing both
members, such as staple(s). In addition, for example, yarn or wire
can be employed.
[0431] The sealing parts 851, 853 work to prevent leakage of a
permeate gas from the gap A31 as described later. To prevent the
leakage more effectively, at least some area of the sealing parts
851 and 853, which is to face the gap A31, can be permeated with
cured resin material. Such a configuration can provide the sealing
parts 851, 853 with improved gas-impermeable property, resulting in
prevention of gas leakage. The configuration can be applied to only
one sealing part 851 or 853.
[0432] The film member 831 and the sealing structure 850 can be
produced for example as follows. The process described below is
only an example and the process sequence and the like do not limit
the present invention in any manner.
[0433] First, the hollow fiber bundle 815 and the casing (for
example, that in FIG. 21) are prepared. The single film member 831
formed in a predetermined size is also prepared. The sealing parts
851, 853 are then put on both side of the film edge such that the
region near the end 831a is sandwiched. The overlap portions of the
sealing parts 851, 853 is fixed by a stapler (one example).
[0434] Next, the film member 831 in the above state is wrapped
around the hollow fiber bundle 815 and then fixed to each other by
a tape (not shown). Then, the hollow fiber bundle 815 is positioned
at a predetermined position in the casing 810, and the tube sheets
821, 822 are formed at the ends of the hollow fiber bundle 815. The
tube sheets 821, 822 can be formed by filling the end of the hollow
fiber bundle 815 with an epoxy material and then curing the
material.
[0435] A specific embodiment will be described with reference to
the example in FIG. 21. The filling of the epoxy material can be
conducted, for example, while the casing 810 for the hollow fiber
bundle 815 is supported in a vertical direction, with a mold (not
shown) attached to the lower end of the casing. During this
process, the surface level of the epoxy material to be applied is
controlled such that the ends of the sealing parts 851, 853 are
buried in the tube sheet 822 as shown in FIG. 21(A), whereas the
end 831a is not buried. Once the ends of the sealing parts 851, 853
are immersed in the epoxy material, the epoxy material infiltrates
into the sealing parts 851, 853 (a region including at least a part
facing the gap A31) by the capillary force.
[0436] Then, the tube sheet material is cured, and the cured tube
sheet 822 is cut at a predetermined position to open the hollow
fiber membrane 814. Subsequently, a conventional assembling (for
example, a process for producing the casing 810) is conducted to
form a module if necessary.
[0437] The film member 831 and the sealing parts 851, 853 can be
disposed in the following order. First, the second sealing part 853
is wrapped on the hollow fiber bundle 815, then the film member 831
is wrapped, and the first sealing part 851 is wrapped.
[0438] There will be described an example of the used of the
separation membrane module of this embodiment having the above
configuration. The method for using a module according to this
embodiment is not limited to the following.
[0439] First, the mixed gas is introduced into the mixed gas space
819a in the casing 810 via the mixed gas inlet 810a. The introduced
mixed gas is fed into each hollow fiber membrane 814 from the end
face of the tube sheet 821 and flows downstream in the inside. It
is preferable that the pressure in the hollow fiber membrane 814 is
higher than a pressure in the closed space 818; for example, it is
suitable to feed a mixed gas at a pressure of 0.01 MPaG to 10 MPaG,
and to vacuum the closed space, for example. During this operation,
a part of the mixed gas selectively permeates the hollow fiber
membrane 814 and is discharged to the closed space 818 outside of
the hollow fiber membrane 814. On the other hand, a non-permeate
gas as it is flows downstream in the hollow fiber membrane 814 and
discharged from the downstream end face to the non-permeate gas
space 819b outside of the hollow fiber membrane 814.
[0440] If the module does not have the film member 831, the
permeate gas from the hollow fiber membrane 814 flows along a
cross-flow direction (that is, a direction crossing the hollow
fiber membrane 814). Alternatively, the gas flows along f4
direction, which includes the opposite direction relative to f2,
that is, in a parallel flow direction, and finally f3 as shown by
an arrow f3 in FIG. 21(B). On the other hand, according to this
embodiment, since the film member 831 is wrapped on the hollow
fiber bundle 815, dissipation of a permeate gas is prevented and
the permeate gas flows in a direction of an arrow f2, that is, a
countercurrent direction to the direction of mixed gas feeding f1,
resulting in an improved efficiency of gas separation. In
particular, this embodiment has the sealing structure 850 for
sealing the gap A31, therefore leakage of the permeate gas through
this gap A31 is prevented. Accordingly, dissipation of the permeate
gas can be reliably prevented and gas separation can be more
efficiently conducted.
[0441] Leakage of the permeate gas can be also prevented by a
structure in which the film end 831a is directly buried in the tube
sheet 822, but it may cause cracks or breakage beginning the area
near the film end 831a in the tube sheet 822. In contrast, since
the sealing parts 851, 853 as a separate member from the film
member 831 are buried in this embodiment, such cracks and breakage
in the tube sheet 822 can be prevented by appropriately selecting a
material for the sealing part.
[0442] As described above, even when the sealing parts 851, 853 are
made of a mesh material the leakage of the permeate gas can be
prevented compared with configuration with no sealing part.
However, according to this embodiment, leakage of a permeate gas
can be more reliably prevented, since a resin material infiltrates
into the sealing parts 851, 853 and cured therein.
Other Embodiments
[0443] Although one embodiment of the invention in this section has
been described, the invention in this section is not limited to the
above embodiment, but various changes can be made.
[0444] For example, the module can have only one of the first and
the second sealing parts 851, 853. Alternatively, the fixing tape
855 for fixing the first sealing part 851 to the film member 831
can be omitted. Furthermore, the fixture 857 for fixing the overlap
of two sealing parts 851, 853 (see FIG. 21(B)) can be omitted.
[0445] FIG. 22 shows another sealing structure; FIG. 22(A) is a
schematic cross-sectional view of the whole module and FIG. 22(B)
is an enlarged partial view of the figure. In this example, filler
891 is illustrated disposed such that it fills a gap A31 between a
film member 831 and a tube sheet 822. The filler 891 can be resin
material such as heat-resisting silicone injected such that it
surrounds the film member 831. Such a filler 891 can also prevent
the permeate gas from leaking from the gap A31, consequently, a
module capable of conducting efficient gas separation can be
obtained. The filler 891 can be formed by processes such as forming
one or multiple holes on the side wall of the casing after forming
the tube sheet 822 in the casing, and then injecting the filler 891
and curing the filler.
[0446] Position for placing the filter 891 is not limited to the
position shown in FIG. 22. For example, the filler 893 can be
disposed at a position away from the gap A31 by a predetermined
distance, between the film member 831 and the casing 810 as shown
in FIG. 23. The filler 893 can be disposed at one position in the
longitudinal direction of the film member 831 as shown in FIG. 23.
Such a filler 893 can be disposed around the periphery of the film
member 831 to thereby block gas flow, and its width can be for
example about 3 mm to 5 mm (for example, 0.5% of the outer surface
of the film) or more.
[0447] Alternatively, filler surrounding the periphery of the film
member 831 can be formed over further wider (longer) region to fill
the gap between the film member 831 and the casing 810; for
example, 10% or more of the outer surface of the film member can be
covered with the filler.
[0448] A gas separation membrane module of the invention in this
section can have a structure for allowing a purge gas to flow as
shown in FIG. 24. This gas separation membrane module has a hollow
fiber bundle 915, a casing 910, two tube sheets 921, 922 for fixing
the ends of the hollow fiber bundle 915, a gas-impermeable film
member 931 wrapped on the outer surface of the hollow fiber bundle
and a sealing structure 950 for sealing a gap between the end of
the film member 931 and the tube sheet 922. This gas separation
membrane module further has a core tube 971 for feeding a purge
gas.
[0449] The casing 910 has a mixed gas inlet 910a in the upstream
side (left side in the figure) and a permeate gas outlet 910c in
the sidewall as in the module in FIG. 20. The structure in the
downstream side from the tube sheet 922 is slightly different from
the module in FIG. 20, that is, a non-permeate gas outlet 910b is
formed in the side wall of the casing 910 and a core tube 971 is
inserted in the center of the casing 910.
[0450] The core tube 971 is a member in which one of the ends is
closed whereas the other is open, and the tube is disposed along a
direction that the opening is downstream (the side of the tube
sheet 922). The core tube 971 extends penetrating the tube sheet
922 and its tip is buried in the tube sheet 921 in the upstream
side. The core tube 971 has hole(s) 971a in a region between two
tube sheets 921, 922.
[0451] The principle for gas separation principle in the module is
basically the same as that shown in FIG. 20. A purge gas is fed
from the opening (purge gas inlet 910d) into the core tube 971, and
the purge gas is discharged into the closed space 918 in the casing
910 via the hole 971a. The purge gas flows along the direction of
f2 (a countercurrent direction to the direction of feeding a mixed
gas) among the hollow fiber membranes 914, and then the purge gas
pushes the permeate gas discharged into the space towards the
permeate gas outlet 910c, which accelerates discharge of the
permeate gas.
[0452] It is also preferable that in such a module utilizing a
purge gas, a sealing structure 950 for sealing a gap between the
film member 931 and the tube sheet 922 is formed. The sealing
structure 950 can be any of various structures described above.
Thus, leakage of the permeate gas and purge gas from the gap can be
prevented, and then the permeate gas and purge gas can smoothly
flow in the f2 direction, as a result, more efficient gas
separation is accomplished.
[0453] The summary of the main invention disclosed in section F is
as follows.
[0454] [1] A gas separation membrane module comprising;
[0455] a hollow fiber bundle as a collection of a number of hollow
fiber membrane with gas separation ability,
[0456] a casing having a mixed gas inlet, a permeate gas outlet and
a non-permeate gas outlet, in which said hollow fiber bundle is
disposed, and
[0457] two tube sheets for fixing both ends of said hollow fiber
bundle,
[0458] a gas-impermeable (including substantially gas-impermeable)
film member wrapped around the outer surface of said hollow fiber
bundle, in which one end substantially abuts on said tube sheet in
the downstream side along the mixed-gas feeding direction, whereas
the other end is disposed away from said tube sheet in the upstream
side in the mixed-gas feeding direction, and
[0459] a sealing structure sealing a gap between said one end of
the film member and said tube sheet.
[0460] [2] The gas separation membrane module as described in [1],
wherein said sealing structure comprises;
[0461] a sealing part wrapped on the inside or the outside in a
radial direction of said film member at said one end of said film
member, the sealing part extending from said end toward said tube
sheet, a part of the extending portion is buried in said tube
sheet.
[0462] [3] The gas separation membrane module as described in [2],
comprising, as said sealing part,
[0463] the first sealing part made of a member, into which liquid
resin material can permeate, which is wrapped on the outside in the
radial direction of said film member, and
[0464] the second sealing part made of a material, into which
liquid resin material can permeate, which is wrapped on the inside
in the radial direction of said film member.
[0465] [4] The gas separation membrane module as described in [2]
or [3], wherein said sealing part is a mesh member.
[0466] [5] The gas separation membrane module as described in [3]
or [4], wherein in at least a region facing said gap of said
sealing parts, a resin material permeates and is cured to seal said
gap.
[0467] [6] The gas separation membrane module as described in [3],
wherein said sealing structure further comprises a fixing tape for
fixing said first sealing part to said film member.
[0468] [7] The gas separation membrane module as described in [3],
wherein said sealing structure further comprises a fixture for
securing an extending portion of said first sealing part extending
from said one end of the film member to an extending portion of
said second sealing part extending from said one end of the film
member.
[0469] [8] The gas separation membrane module as described in [1],
wherein said sealing structure comprises a filler disposed such
that the filler fills said gap between said one end of the film
member and said tube sheet.
[0470] [9] The gas separation membrane module as described in any
of [1] to [8], wherein extending portion of said one end of the
film member is configured to not to be inserted into said tube
sheet.
[0471] [10] The gas separation membrane module as described in any
of [1] to [9], wherein said film member is made of polyimide.
Section G: Gas Separation Membrane Module Ensuring Adequate Sealing
Performance Near a Tube Sheet
Technical Field
[0472] This invention relates to a gas separation membrane module
for gas separation using a hollow fiber membrane, in particular, to
a gas separation membrane module which ensures adequate sealing in
the vicinity of a tube sheet and therefore it can be used at high
temperature satisfactorily, even when a tube sheet material
relatively susceptible to cure shrinkage is used
Background Art
[0473] A hollow fiber type gas separation membrane module generally
has a hollow fiber element including a hollow fiber bundle
comprising a number of hollow fiber membranes with selective
permeability and a hollow casing housing the element. The hollow
fiber bundle is fixed at its one or two ends by a resin cured plate
(tube sheet).
[0474] A gas separation membrane generally has a larger gas
permeation rate at a higher temperature and a higher pressure of a
supplied gas. Therefore, when using the gas separation membrane
module, it may be considered that the source gas is compressed by
for example a compressor before being fed to the module. In some
cases, the compressed gas may be warmed to about 149.degree. C. to
260.degree. C.
[0475] It is necessary to use heat-resistant tube sheet material in
such modules for separating high-temperature mixed gas as described
above. However, such tube sheet material is generally susceptible
to cure shrinkage during its curing, thus there may be a problem
such as inadequate performance of sealing around the tube sheet. In
view of the problem, an objective of the invention in this section
is to provide a separation membrane module and so on which ensures
adequate sealing performance in the vicinity of the tube sheet and
therefore it can be used at high temperature satisfactorily, even
when a tube sheet material relatively susceptible to cure shrinkage
is used and furthermore
[0476] The summary of the main invention disclosed in this section
is as follows.
[0477] A gas separation membrane module according to one embodiment
of the invention in this section comprises;
[0478] a hollow fiber bundle as a collection of a number of hollow
fiber membranes with gas separation ability,
[0479] a casing housing said hollow fiber bundle, and
[0480] a tube sheet for fixing at least one end of said hollow
fiber bundle,
[0481] wherein the outer surface of said tube sheet does not
contact the inner surface of said casing,
[0482] further comprising a sealing member for sealing between the
outer surface of said tube sheet and the inner surface of said
casing.
[0483] A process for manufacturing a gas separation membrane module
according to one embodiment of the invention in this section is a
process for manufacturing a gas separation membrane module,
comprising a hollow fiber bundle as a collection of a number of
hollow fiber membranes with gas separation ability, a casing
housing said hollow fiber bundle, and a tube sheet for fixing at
least one end of said hollow fiber bundle, comprising
[0484] applying a mold release to at least a part which is to be in
contact with said tube sheet in the inner surface of said
casing,
[0485] filling a thermosetting resin in a part of said casing,
[0486] curing said thermosetting resin to form said tube sheet,
and
[0487] forming, after said curing of said thermosetting resin, a
sealing member between the outer surface of said tube sheet and the
inner circumference surface of said casing.
[0488] Definitions of terms used herein are as follows.
[0489] The term, "high-temperature condition" or "high temperature"
means a temperature in the range of, for example, 80.degree. C. to
300.degree. C.
[0490] The term, "cylindrical vessel" is not limited to those in
which both ends are open, but includes those in which only one end
is open.
[0491] According to the invention in this section, there is
provided a gas separation membrane module which ensures adequate
sealing in the vicinity of the tube sheet even when the tube sheet
material relatively susceptible to cure shrinkage is used and
furthermore which can be satisfactorily used at high
temperature.
Embodiments in Section G
[0492] There will be described one embodiment of the invention in
this section with reference to the drawings. FIG. 25 more
specifically shows the shape of a casing (detailed later) as an
example. The configurations described below are merely examples and
a gas separation membrane module of the present invention is not
limited to these configurations.
[0493] A gas separation membrane module (hereinafter, simply
referred to as "module") 1001 shown in FIGS. 25 and 26 has a hollow
fiber bundle 1015 as a collection of a number of hollow fiber
membranes 1014, a casing 1010 housing the bundle and tube sheets
1021, 1022 at the ends of the hollow fiber bundle 1015. This module
1001 is, for example, of a so-called bore feed type where a mixed
gas (source gas) is fed into the hollow fiber membrane 1014.
[0494] The hollow fiber membrane 1014 can be made of any of known
structure as long as it has gas separation ability. For example, it
is suitably made of polymer material, which is glassy at normal
temperature (23.degree. C.) such as, in particular, polyimide,
polysulfone, polyetherimide, polyphenylene oxide and polycarbonate
for the gas separation ability.
[0495] The hollow fiber bundle 1015 can be, for example, a
collection of about 100 to 1,000,000 hollow fiber membranes 1014.
There are no particular restrictions to the shape of the collected
hollow fiber bundle 1015, but for example, a cylindrical shape is
preferable in the light of easiness in production and pressure
resistance of a vessel. FIG. 25 shows an embodiment in which hollow
fiber membranes 1014 are disposed substantially in parallel,
however, these hollow fiber membranes can be cross-arranged.
[0496] There are no particular restrictions to a mixed gas to be
subjected to separation by the hollow fiber membrane 1014, but it
can be, for example, a mixed gas of a more permeable gas and a less
permeable gas with a ratio of permeation rates to a separation
membrane of 2 or more. The gas separation membrane module 1001 of
this embodiment can be use for separating a particular gas
component from a mixed gas in various manners. For example, it can
be used for drying a variety of gases, humidification of a variety
of gases, nitrogen enrichment or oxygen enrichment.
[0497] The tube sheets 1021, 1022 are formed substantially as a
disc-shape (detailed later) in response to the shape of the casing
1010, and fix the end of the hollow fiber bundle 1015, with each
hollow fiber membrane 1014 opened. In this example, the tube sheet
works as a sealer between the hollow fiber membranes. The tube
sheet can be made of a thermoplastic resin such as polyethylene and
polypropylene or a thermosetting resin such as an epoxy resin and
an urethane resin. There will be described a case in which a tube
sheet is made of a thermosetting resin.
[0498] For a nitrogen membrane module, the epoxy resin for example
described in Japanese published examined application No. 1990-36287
can be used for the tube sheet 1021, 1022, whereas for an
organic-vapor separation module the epoxy resin for example
described in WO 2009/044711 can be used The epoxy resin as
disclosed in section B can also be used for a tube sheet in the
module of this section.
[0499] A closed space 1018 (having a permeate gas outlet 1010c as
described below) is formed by the casing 1010 and the two tube
sheets 1021, 1022 as shown in FIG. 25 in this embodiment. The
permeate gas permeating the hollow fiber membrane 1014 is
introduced into this closed space 1018. A mixed gas space 1019a is
formed by the casing 1010 and the tube sheet 1021, whereas a
non-permeate gas space 1019b is formed by the casing 1010 and the
tube sheet 1022.
[0500] As shown in FIG. 25, the casing 1010 is substantially
cylindrical as a whole. The casing 1010 has a mixed gas inlet 1010a
for introducing a mixed gas into the casing 1010 in the upstream
side (left side in the figure), a non-permeate gas outlet 1010b in
the downstream side (right side in the figure) and a permeate gas
outlet 1010c in its side wall. The number of the permeate gas
outlet 1010c can be one or two or more. The permeate gas outlets
1010c can be disposed at regular intervals along the side wall of
the casing 1010.
[0501] The mixed gas introduced from the mixed gas inlet 1010a
enters into each hollow fiber membrane 1014 from the end face of
the tube sheet 1021 and flows downstream in the inside. A part of
the mixed gas permeates the hollow fiber membrane 1014, and the
permeate gas is fed to the inside of the closed space 1018 and then
discharged from the casing through the permeate gas outlet 1010c.
On the other hand, a non-permeate gas not permeating the hollow
fiber membrane as it is flows downstream in the hollow fiber
membrane 1014 and flows outward from the end face, and then is
discharged out of the casing through the non-permeate gas outlet
1010b.
[0502] The mixed gas inlet 1010a and/or the non-permeate gas outlet
1010b can be disposed in such a way that their central axes are
aligned with the central axis of the casing 1010 (that is, the
central axis of the hollow fiber bundle 1015). The casing 1010 can
have a cylindrical member 1011 and cap members 1012 at its ends as
in the example in FIG. 26 (the other is not shown). The cylindrical
member 1011 and the capping member 1012 can be, for example, made
of a metal.
[0503] Specifically, the cylindrical member 1011 is a hollow member
with an inner diameter of d.sub.0, and has thick wall portions
1011a, 1011b near its end. The first thick wall portion 1011a is
formed near the end face of the cylindrical member 1011, and has an
inner diameter shorter than the inner diameter do. The second thick
wall portion 1011b is formed in an inner area in an axial direction
than the first thick wall portion 1011a, and has an inner diameter
shorter than the inner diameter d.sub.0. An inner diameter of a
portion between the thick wall portion 1011a and 1011b is longer
than an inner diameter of both thick wall portions 1011a, 1011b;
for example it can be do.
[0504] Corresponding to the structure of the cylindrical member
1011, the tube sheet 1021 is formed in the following shape. The
tube sheet 1021 includes generally three parts with different
diameters (starting from the outer side, the first part 1021a, the
second part 1021b and the third part 1021c) as shown in FIG. 26.
Among these parts, the middle part 1021b has the largest diameter.
In this example, the boundary between the first part 1021a and the
second part 1021b is a tapered face. The boundary between the
second part 1021b and the third part 1021c is a straight face (the
face extending in a direction orthogonal to the central axis of the
cylindrical member).
[0505] When the separation membrane module 1001 is used, a pressure
of a mixed gas applies a force to the tube sheet 1021 in a
direction that the tube sheet is pushed into the cylindrical member
1011. However, according to the configuration as shown in FIG. 26,
a part of the tube sheet 1021 can abut on the thick wall portion
1011b to restrict movement of the tube sheet 1021, so that the tube
sheet 1021 is not moved into the inside.
[0506] There can be, but not limited to, an R-shape on the corner
1021f between the second part 1021b and the third part 1021c in the
tube sheet. Thus, stress concentration can be relaxed in this part,
so that breakage of the tube sheet and so on can be prevented.
[0507] The example in FIG. 26 shows the state where the tube sheet
1021 is a thermosetting resin and the tube sheet 1021 has a
slightly reduced diameter due to cure shrinkage. In this
configuration, sealing between the tube sheet 1021 and the
cylindrical member 1011 may not be ensured. Therefore, an annular
sealing member 1060 for sealing between these members is provided
with the module in this embodiment.
[0508] An annular step 1021s is formed in the outer circumference
of the first part 1021a of the tube sheet as shown in FIG. 26. An
annular concave groove C1 as a whole is formed by the cooperation
of the step 1021s and the inner surface of the cylindrical member
1011. An annular sealing member 1060 is disposed in the concave
groove C1.
[0509] The sealing member 1060 is an annular component made of
elastics members, which can be fitted into the concave groove C1
(for example, an O-ring). Alternatively, a resin material for
sealing can be injected into the concave groove C1 and cured
therein, to form the sealing member. The O-ring can have a circular
or elliptic cross-sectional shape. Examples of an "annular part
consisting of elastic members" can, in addition to an O-ring,
include a V- or U-packing having a substantially V- or U-shaped
cross section, respectively. Furthermore, its cross section can be
rectangular, polygonal or X-shaped. The sealing member 1060 seals
between the tube sheet 1021 and the casing 1010 as well as between
the tube sheet 1021 and the capping member 1012 in the example
shown in FIG. 26.
[0510] The structure shown in FIG. 26 is merely an example, which
does not limit this invention in any manner. For example, the first
part 1021a and the third part 1021c in the tube sheet can have the
same diameter. Alternatively, a tube sheet having the first part
1021a and the third part 1021c can be used. Furthermore, the
surface between the first part 1021a and the second part 1021b can
be, not tapered face as shown in FIG. 26, but a straight face.
Likewise, the surface between the first part 1021b and the third
part 1021c can be, not a straight face as shown in FIG. 26, but a
tapered face. Furthermore, the sealing member 1060 seals between
the tube sheet 1021 and the casing 1010 and the capping member 1012
in the above embodiment, however, there can be additional sealing
member between the casing 1010 and the capping member 1012 in
addition to the sealing member between the tube sheet 1021 and the
casing 1010
[0511] FIG. 27 is a cross-sectional view taken on A-A line of FIG.
26. Concave portions 1011d, 1011d can be formed at two positions on
the inner surface of the cylindrical member 1011 as shown in the
figure. In this configuration, the material for tube sheet enters
the concave parts 1011d, 1011d and then is cured (detailed below).
Consequently, rotation of the tube sheet 1021 can be prevented.
There are no particular restrictions to the number of the concave
parts 1011d, for example, one, or three or more.
[0512] As an example, the following process can be used for
producing the gas separation membrane module 1001 having the
configuration as described above. Specifically, a production
process according to this embodiment including;
[0513] (a) applying material for releasing mold to at least a part
which is to be in contact with a tube sheet in the inner surface of
a casing,
[0514] (b) injecting thermosetting resin before curing into a part
of the casing,
[0515] (c) curing the injected thermosetting resin to form the tube
sheet, and
[0516] (d) providing an annular sealing member between the outer
circumference surface of the tube sheet and the inner surface of
the casing after the curing of the thermosetting resin.
[0517] By applying the material for releasing mold in step (a), the
tube sheet made of for example epoxy resin can be smoothly released
from the casing (for example, made of a metal) in the curing of
step (c). If it is not used, the tube sheet may not be released in
the resin curing step, cracks may be formed in the tube sheet.
[0518] In step (b), a not-shown mold can be attached to the end of
the cylindrical member 1011 during tube sheet resin is injected. In
this process, the mold can has an annular convex part corresponding
to the step 1021s in the tube sheet (see FIG. 26) to form the step
1021s in the tube sheet.
[0519] In step (d), an annular elastic member such as an O-ring can
be fitted into the concave groove C1 as described above, or
alternatively some resin can be injected into the concave groove C1
and cured to form the sealing member 1060.
[0520] According to the gas separation membrane module 1001 as
described above in this embodiment, the separate sealing member
1060 can ensure sufficient sealing between these members, even if
cure shrinkage of the tube sheet 1021 may cause insufficient
sealing between the outer surface of the tube sheet and the inner
surface of the casing,
[0521] This is particularly advantageous in a gas separation
membrane module used at high temperature. That is, generally,
material resistant to cure shrinkage tends to be elastic, have a
lower glass-transition temperature and be less heat-resistant. On
the other hand, tube sheet material with excellent heat resistance
tends to be susceptible to cure shrinkage. If such heat-resistant
material is used in some structures such as the tube sheet is
configured to adhere to the casing, cracks might be formed in the
tube sheet due to drawing stress generated by the shrinkage of the
tube sheet material. In contrast, according to this embodiment, the
material for mold release is applied to the inside of the casing to
prevent adhesion of the tube sheet material, whereas the sealing
between the tube sheet and the casing is ensured by the annular
sealing member. Therefore, there can be provided a gas separation
membrane module in which crack formation is prevented in a tube
sheet and sealing is adequately ensured.
[0522] Although of the tube sheets 1021, 1022, mainly the tube
sheet 1021(FIG. 26) has been described, both tube sheets 1021, 1022
can have the same similar configuration. Alternatively, only one
tube sheet can has the structure as shown in FIG. 26. Furthermore,
the structures of a tube sheet, an annular sealing member and a
casing as in this embodiment can be applied, besides a bore feed
type module, a shell feed type module and other types of
modules.
[0523] The summary of the main invention disclosed in section G is
as follows.
[0524] [1] A gas separation membrane module according to one
embodiment of the invention in this section comprises;
[0525] a hollow fiber bundle as a collection of a number of hollow
fiber membranes with gas separation ability,
[0526] a casing housing said hollow fiber bundle, and
[0527] a tube sheet for fixing at least one end of said hollow
fiber bundle,
[0528] wherein the outer surface of said tube sheet does not
contact to the inner circumference surface of said casing,
[0529] further comprising a sealing member for sealing between the
outer surface of said tube sheet and the inner surface of said
casing.
[0530] [2] The gas separation membrane module as described in [1],
wherein said tube sheet has a step for forming an annular concave
groove by cooperating with the inner surface of said casing.
[0531] [3] The gas separation membrane module as described in [1]
or [2],
[0532] wherein said casing comprises; a tubular member surrounding
said hollow fiber bundle and a capping member at the end of the
tubular member,
[0533] said tubular member comprises a thick wall portion partially
having shorter inner diameter, the thick wall portion abuts on said
tube sheet to prevent movement of said tube sheet in said tubular
member toward the inside from an axial direction.
[0534] [4] The gas separation membrane module as described in any
of [1] to [3], wherein said sealing member is an annular elastic
member which is fitted into said annular concave groove.
[0535] [5] A process for manufacturing a gas separation membrane
module according to one embodiment of the invention in this section
is a process for manufacturing a gas separation membrane module,
comprising a hollow fiber bundle as a collection of a number of
hollow fiber membranes with gas separation ability, a casing
housing said hollow fiber bundle, and a tube sheet for fixing at
least one end of said hollow fiber bundle, including;
[0536] applying material for releasing mold to at least a part
which is to be in contact with said tube sheet in the inner surface
of said casing,
[0537] filling thermosetting resin in a part of said casing,
[0538] curing said thermosetting resin to form said tube sheet,
and
[0539] forming, after said curing of said thermosetting resin, a
sealing member between the outer surface of said tube sheet and the
inner surface of said casing.
EXAMPLES
Examples Related to Section A
[0540] The invention in section A will be further described with
reference to examples. The invention in section A is, however, not
be limited to the following examples.
Method for Measuring a Glass-Transition Temperature (Tg) of a
Hollow Fiber Membrane
[0541] A glass-transition temperature (TO was measured for a sample
of 2 mg over a temperature range of room temperature to 400.degree.
C. at a rate of 10.degree. C./min under a nitrogen atmosphere using
DSC50 device from Shimadzu Corporation in accordance with JIS K7121
"Method for measuring an extrapolated glass transition onset
temperature".
Method for Measuring a Shape-Retention Ratio of a Hollow Fiber
Membrane
[0542] In measurement of a shape-retention ratio, a hollow fiber
having a length of 200 mm was placed in a hot air oven at
175.degree. C. for 2 hours, and a length before and after heating
were measured. A shape-retention ratio was determined as a
proportion of a length after heating to an original length before
heating.
Method for Measuring a Solution Viscosity
[0543] A solution viscosity of a polyimide solution was measured at
a temperature of 100.degree. C. using a rotating viscometer (rotor
shear rate: 1.75 sec.sup.-1).
Production Example 1
[0544] In a separable flask equipped with a stirrer and a
nitrogen-gas inlet tube, 200 mmol of
4,4'-(hexafluoroisopropylidene)-bis(phthalic anhydride), 225 mmol
of 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 75 mmol of
pyromellitic dianhydride, 250 mmol of
2,2',5,5'-tetrachlorobenzidine and 250 mmol of
3,7-diamino-dimethyldibenzothiophene=5,5-dioxide were placed in
1882 g of 4-chlorophenol as a solvent, and the mixture was
subjected to polymerization and imidization at a reaction
temperature of 190.degree. C. for 20 hours under stirring while
nitrogen gas was flowing in the flask, to prepare an aromatic
polyimide solution with a polyimide concentration of 17% by weight.
This aromatic polyimide solution has a solution viscosity of 1940
poise at 100.degree. C.
[0545] The aromatic polyimide solution thus prepared was filtered
through a 400 mesh woven wire. Using the solution as a dope
solution and a spinning apparatus equipped with a nozzle for
hollow-fiber spinning, the dope solution was discharged from a
circular opening of the nozzle for hollow-fiber spinning (an outer
diameter of the circular opening: 1000 .mu.m, a slit width of the
circular opening: 200 .mu.m, an outer diameter of the core opening:
400 .mu.m) while nitrogen gas was fed from the core opening, to
form a hollow fiber form, which was then carried under a nitrogen
atmosphere, immersed in a coagulation liquid to be solidified, and
taken by a take-up roll to provide a wet hollow fiber membrane.
Then, this hollow fiber membrane was dried and further heated at
250.degree. C. for 30 min to give a hollow fiber membrane 1.
[0546] The hollow fiber membrane 1 thus prepared generally had an
outer diameter of 410 .mu.m and an inner diameter of 280 .mu.m. A
fiber bundle element was formed from the hollow fiber membranes and
further a gas separation membrane module was formed from each fiber
bundle element comprising the hollow fiber membranes.
[0547] Examples 1, 2 used an air separation membrane module 1 which
is produced using the hollow fiber membranes 1 prepared as
described above, and Comparative Examples 1, 2 used an air
separation membrane module 2 which is produced using a hollow fiber
membrane 2 described below or an air separation membrane module 3
which is produced using a hollow fiber membrane 3.
[0548] Table 1 shows data such as properties of each hollow fiber
membrane. A glass-transition temperature and a shape-retention
ratio were determined as described above.
TABLE-US-00001 TABLE 1 Outer Inner diameter of a diameter of a
Glass Shape P'.sub.O2*.sup.2 Hollow Material of hollow fiber hollow
fiber transition retention (.times.10.sup.-5 cm.sup.3 fiber a
hollow fiber membrane membrane temperature ratio (STP)/cm.sup.2
membrane membrane (.mu.m) (.mu.m) (.degree. C.) (%) sec cmHg) 1
Polyimide 410 280 300>*.sup.1 99.5 9 2 Polysulfone 386 200 190
93 4.9 3 Polyetherimide 160 95 223 99 4.5 *.sup.1The hollow fiber
membrane 1 does not have a glass transition temperature at
300.degree. C. or lower and cannot be determined by the method
described above. *.sup.2P'.sub.O2 is an oxygen permeation rate at
40.degree. C.
[0549] Table 2 shows the specification of each air separation
membrane module.
TABLE-US-00002 TABLE 2 Air separation Inner diameter Effective
Number Membrane membrane of a vessel length of fibers area module
(mm) (mm) in a module (m.sup.2) 1 40 249 3500 1.12 2 40 496 3800
2.28 3 40 223 18000 2.02
Example 1 of Section A
[0550] An air at 175.degree. C. and a pressure of 0.2 MPaG was fed
to the air separation membrane module 1, regulating the air-feed
rate such that an oxygen gas concentration in a non-permeate gas,
that is, a nitrogen-rich air, was 12%, and the process continuously
proceeded under these conditions. At predetermined elapsed times
from the beginning of the operation, a flow rate of the
nitrogen-rich air produced was measured. The measurement results
are shown in FIG. 1. From the measurement results, an oxygen
permeation rate (P'.sub.O2) of the air separation membrane and a
ratio of an oxygen-gas permeation rate to a nitrogen-gas permeation
rate (P'.sub.O2/P'.sub.N2) as an index of separation performance
were calculated at 0, 140 and 2069 hours after the beginning of the
operation. The results are shown in Table 3.
[0551] At the beginning of the operation (0 hr), P'.sub.O2 was
35.4.times.10.sup.-5 cm.sup.3 (STP)/cm.sup.2seccmHg and a flow rate
of the nitrogen-rich air produced from the air separation membrane
module 1 was 0.748 Nm.sup.3/h. At 140 hrs after the beginning of
the operation, P'.sub.O2 was 33.4.times.10.sup.-5 cm.sup.3
(STP)/cm.sup.2seccmHg which was lower only by 5.6% from the
beginning of the operation. At 2069 hrs after the beginning of the
operation, P'.sub.O2 was 31.4.times.10.sup.-5
cm.sup.3(STP)/cm.sup.2seccmHg which was lower by 11% from the
beginning of the operation. A flow rate of the nitrogen-rich air
produced from the air separation membrane module 1 after 2069 hrs
from the beginning of the operation was 0.65 Nm.sup.3/h, which was
lower only by 13% compared with the beginning of the operation. The
results indicate that even after operation at 175.degree. C. for
2000 hrs, the air separation membrane module 1 maintained its
ability as a gas separation membrane.
Comparative Example 1 of Section A
[0552] Although measurement as described in Example 1 was attempted
using the air separation membrane module 2, a hollow fiber membrane
was so shrieked at 175.degree. C. that a nitrogen-rich air could
not be obtained. In the air separation membrane module 2 maintained
at 175.degree. C., hollow collapse, fiber breakage and distortion
of a tube sheet were observed.
Comparative Example 2 of Section A
[0553] Operation was conducted and a flow rate of a nitrogen-rich
air at each predetermined time was measured as described in Example
1, except that the air separation membrane module 3 was used. The
measurement results are shown in FIG. 1. P'.sub.O2 at the beginning
of the operation was 19.3.times.10.sup.-5
cm.sup.3(STP)/cm.sup.2seccmHg and a flow rate of a nitrogen-rich
air produced from the air separation membrane module was 0.625
Nm.sup.3/h. At 140 hrs after the beginning of the operation,
P'.sub.O2 of the separation membrane was 11.3.times.10.sup.-5
cm.sup.3(STP)/cm.sup.2seccmHg, which was lower by 41% from the
beginning of the use, and a flow rate of a nitrogen-rich air
produced from the air separation membrane module was 0.419
Nm.sup.3/h, which was lower by 35% from the beginning of the
use.
Example 2 of Section A
[0554] Measurement was conducted as described in Example 1, except
that the air-feed rate was regulated such that an oxygen gas
concentration in a nitrogen-rich air produced was 5%. The
measurement results are shown in FIG. 2. A flow rate of a
nitrogen-rich air at the beginning of the operation was 0.18
Nm.sup.3/h. At 2069 hr after the beginning of the operation, a flow
rate of a nitrogen-rich air was 0.15 Nm.sup.3/h, which was lower
only by 16%. The results indicate that, as in Example 1, the air
separation membrane module 1 maintained its performance as a gas
separation membrane even after 2000 hr at 175.degree. C.
TABLE-US-00003 TABLE 3 <Flow rate of a nitrogen-rich air and
properties of an air separation membrane after predetermined times
at 175.degree. C.> Hollow 0 hr 140 hr 2069 hr fiber Product
P'.sub.O2/ Product P'.sub.O2 Product P'.sub.O2 membrane amount
P'.sub.O2 P'.sub.N2 amount P'.sub.O2 P'.sub.N2 amount P'.sub.O2
P'.sub.N2 1 0.748 35.4 2.6 0.717 33.4 2.6 0.650 31.4 2.5 2 Not
measureable Not measureable Not measureable 3 0.625 19.3 2.7 0.419
11.3 3.0 -- -- -- In this table , the product amount is a flow rate
of a nitrogen-rich air produced (the unit is Nm.sup.3/h). P'.sub.O2
is an oxygen-gas permeation rate (the unit thereof is
.times.10.sup.-5 cm.sup.3 (STP)/cm.sup.2 sec cmHg).
P'.sub.O2/P'.sub.N2 is a ratio of an oxygen-gas permeation rate to
an nitrogen-gas permeation rate.
Example Related to Section B
[0555] The invention in section B will be described with reference
to examples, but the present invention is, however, not be limited
to the examples.
Example 1
Preparation of a Casting Resin Composition
[0556] A mixture of 100 parts by weight of phenol novolac
polyglycidyl ether and 10 parts by weight of a carboxyl terminated
butadiene acrylonitrile copolymer (molecular weight: 3100) was
heated at 150.degree. C. for 3 to 4 hours to prepare a denatured
epoxy resin. Then, 100 parts by weight of the denatured epoxy resin
thus prepared, 80 parts by weight of
methyl-5-norbornene-2,3-dicarboxylic anhydride and 0.3 parts by
weight of 2-ethyl-4-methylimidazole were mixed and stirred to
prepare a casting resin composition.
Evaluation of Moldability of a Tube Sheet
[0557] A fiber bundle as a collection of 12,000 polyimide hollow
fiber membranes (length: 100 cm, outer diameter: 500 .mu.m) was
placed in a mold with .PHI. 100 mm as shown in FIG. 4b. The fiber
bundle was substantially erected in such a way that the tip was
down, and the casting resin composition prepared by the above
procedure was slowly injected into a mold kept at 70.degree. C. The
amount of the casting resin composition was regulated such that a
thickness became about 90 mm. After the injection, the composition
was first-cured at 70.degree. C. for 12 hours, then heated to
142.degree. C. and then post-cured for 4 hours, to mold the tube
sheet. After the curing, the hollow fiber element was removed from
the casing and visually observed, and the tube sheet was cut
substantially into halves and the state of the center was visually
observed.
[0558] As a result, no cracks were observed in the molded tube
sheet.
Example Related to Section E
[0559] There will be described the results of simulation with
respect to a response of a gas separation membrane module with or
without film member wrapping. Table 4 shows module response, in
which "type A (crossflow)" indicates a module without film member
wrapping, "type B (counterflow)" indicates a module with film
member wrapping. Calculation was conducted with the temperature of
t=25.degree. C. and the mixed-gas feed pressure PF=0.7 MPaG. It is
noted that the simulation was conducted for a separation membrane
module for producing a nitrogen-rich air as a product from air fed
as the mixed gas. This nitrogen-rich air passes through the hollow
fiber membrane and recovered as a non-permeate gas discharged from
the downstream end. In the table, a feed pressure and a feed flow
rate indicate a feed pressure and a feed flow rate of the air as a
mixed gas, respectively; a product concentration and a product flow
rate indicate a nitrogen concentration and a flow rate of a
nitrogen-rich air as a product as a non-permeate gas, respectively;
and a recovery rate indicates a proportion of a non-permeate gas as
a product in the mixed gas fed (product rate/feed flow
rate).times.100.
TABLE-US-00004 TABLE 4 Feed Feed Product Product Temp. pressure
flow rate concentration flow rate t PF FF XR FR Recovery Type Flow
Case .degree. C. MPaG Nmm.sup.3/h % N.sub.2 Nm.sup.3/h rate Remarks
A Crossflow 1 25 0.7 131.9 95 62.0 47.0 B Counterflow 2 25 0.7
131.9 96.05 61.5 46.6 FF equal to that in 1 3 25 0.7 144.8 95 73.2
50.6 XR equal to that in 1
[0560] As shown in Table 4, at the same feed flow rate FF (see
cases 1 and 2), the case 2 with film member wrapping can provide
higher product concentration XR. At the same product concentration
XR (see cases 1 and 3), the case 3 with film member wrapping can
provide higher product flow rate and a higher recovery rate. In
other words, these results indicate that wrapping with a film
member is effective in efficient gas separation.
EXPLANATION OF REFERENCES
[0561] 1, 1', 101: separation membrane module [0562] 10, 110, 110':
cylindrical vessel [0563] 10a: inner surface of vessel [0564] 10f:
flange [0565] 10h: opening [0566] 10s: step [0567] 10t: step [0568]
110g: groove [0569] 111: tubular member [0570] 112: end member
[0571] 12, 112h: permeate gas outlet [0572] 112f: flange [0573] 14:
hollow fiber membrane [0574] 15, 115: hollow fiber bundle [0575]
17: annular sealing member [0576] 18, 118, 119: O-ring [0577] 21,
26, 27, 120, 121, 127: cap [0578] 20h: opening [0579] 120f flange
[0580] 120s: step [0581] 22A: mixed gas inlet [0582] 22B:
non-permeate gas outlet [0583] 27f: flange [0584] 127f: flange
[0585] 127g: groove [0586] 30, 30', 38, 130A, 130B, 530: tube sheet
[0587] 30s, 530s: step [0588] 30't: step [0589] 41: discharge pipe
[0590] 42: fixing screw [0591] 43: fixture [0592] 201: gas
separation membrane module [0593] 210: cartridge [0594] 211:
cylindrical vessel [0595] 212: opening [0596] 214: hollow fiber
membrane [0597] 215: hollow fiber bundle [0598] 217, 218: inner
groove [0599] 219: periphery groove [0600] 220, 221: capping member
[0601] 220A: end face [0602] 220B: cylindrical part [0603] 220f:
flat part [0604] 220g: flat part [0605] 220h: through-hole [0606]
223: outlet [0607] 227a, 227b: inner groove [0608] 230, 231: tube
sheet [0609] R1, R2: elastic ring member [0610] 245: fixing rod
[0611] 246: nut [0612] P1: gas inlet [0613] P2: non-permeate gas
outlet [0614] P3: gas channel [0615] 601: gas separation membrane
module [0616] 610: casing [0617] 610a: mixed gas inlet [0618] 610b:
non-permeate gas outlet [0619] 610c: permeate gas outlet [0620]
611: tubular member [0621] 612, 613: cap [0622] 614: hollow fiber
membrane [0623] 615: hollow fiber bundle [0624] 618: closed space
[0625] 619a: mixed gas space [0626] 619b: non-permeate gas space
[0627] 621, 622: tube sheet [0628] 631: film member [0629] 631a,
631b: end [0630] 801: gas separation membrane module [0631] 810,
910: casing [0632] 810a, 910a: mixed gas inlet [0633] 810b, 910b:
non-permeate gas outlet [0634] 810c, 910c: permeate gas outlet
[0635] 910d: purge gas inlet [0636] 811: tubular member [0637] 813:
tube sheet retaining member [0638] 813a: straight part [0639] 813b:
longer diameter part [0640] 813c: tapered part [0641] 814, 914:
hollow fiber membrane [0642] 815, 915: hollow fiber bundle [0643]
818, 918: closed space [0644] 819a: mixed gas space [0645] 819b:
non-permeate gas space [0646] 821, 822, 921, 922: tube sheet [0647]
822a: hollow-fiber-membrane burying part [0648] 822b: tube sheet
intact part [0649] 831: film member [0650] 831a, 831b: end [0651]
850, 950: sealing structure [0652] 851, 853: sealing part [0653]
855: fixing tape [0654] 857: fixture [0655] 891, 893: filler [0656]
971: core tube [0657] 971a: hole [0658] A1: exposed part [0659]
A31: gap [0660] 1001: gas separation membrane module [0661] 1010:
casing [0662] 1010a: mixed gas inlet [0663] 1010b: non-permeate gas
outlet [0664] 1010c: permeate gas outlet [0665] 1011: cylindrical
member [0666] 1011a, 1011b: thick wall portions [0667] 1011d:
concave part [0668] 1012: capping member [0669] 1014: hollow fiber
membrane [0670] 1015: hollow fiber bundle [0671] 1018: closed space
[0672] 1019a: mixed gas space [0673] 1019b: non-permeate gas space
[0674] 1021, 1022: tube sheet [0675] 1021s: step [0676] 1060:
sealing member [0677] C1: annular concave groove [0678] B11: mixed
gas inlet [0679] B12: permeate gas outlet [0680] B13: non-permeate
gas outlet [0681] B14: hollow fiber membrane [0682] B15: casing
[0683] B16a, 16b: tube sheet [0684] B21: mold [0685] B22: casing
[0686] B23: tube sheet [0687] B24: hollow fiber membrane
* * * * *