U.S. patent application number 15/053329 was filed with the patent office on 2016-09-01 for structured packing for gas-liquid mass transfer unit.
This patent application is currently assigned to GTC Technology US LLC. The applicant listed for this patent is GTC Technology US LLC. Invention is credited to Ichiro Minami, Masajiro Sakurai, Yasuo Suzuki.
Application Number | 20160250616 15/053329 |
Document ID | / |
Family ID | 45773316 |
Filed Date | 2016-09-01 |
United States Patent
Application |
20160250616 |
Kind Code |
A1 |
Minami; Ichiro ; et
al. |
September 1, 2016 |
STRUCTURED PACKING FOR GAS-LIQUID MASS TRANSFER UNIT
Abstract
In existing structured packing, performance depends on effective
contacting area. Performance decreases in cases having high surface
tensions such mixtures containing a lot of water. Such mixtures are
difficult to wet the packing surface. The present invention
prevents liquid from intersecting the crease of the corrugation and
from falling into a free space. Further, liquid flowing into the
slot makes frequent liquid and vapor interfacial update resulting
in positive utilization of the wetted area. The most important
point of this invention is taking a large value of 3.5 or more of
P/H (pitch/height of the crimp) and providing the horizontal slot
on the crease, resulting in adding the flow reversal mechanism and
frequent interfacial update.
Inventors: |
Minami; Ichiro; (Tokyo,
JP) ; Sakurai; Masajiro; (Yokosuka, JP) ;
Suzuki; Yasuo; (Chigasaki, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GTC Technology US LLC |
Houston |
TX |
US |
|
|
Assignee: |
GTC Technology US LLC
Houston
TX
|
Family ID: |
45773316 |
Appl. No.: |
15/053329 |
Filed: |
February 25, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13819923 |
Jun 7, 2013 |
9314709 |
|
|
PCT/IB2011/002695 |
Sep 1, 2011 |
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15053329 |
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Current U.S.
Class: |
261/112.2 |
Current CPC
Class: |
B01J 2219/32268
20130101; B01J 2219/32227 20130101; B01J 2219/32272 20130101; B01J
2219/3325 20130101; B01J 2219/32231 20130101; B01F 3/04078
20130101; B01J 19/32 20130101; B01J 2219/32408 20130101; B01D 3/26
20130101; B01J 2219/3221 20130101; B01D 3/32 20130101; B01J
2219/32213 20130101; B01D 3/28 20130101; B01J 2219/32262
20130101 |
International
Class: |
B01J 19/32 20060101
B01J019/32; B01D 3/26 20060101 B01D003/26 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 2, 2010 |
JP |
2010-210050 |
Claims
1. A packing system comprising: a plurality of sheets, each sheet
of the plurality of sheets comprising a first bend and an opposite
parallel second bend, the first bend and the opposite parallel
second bend defining a waved surface; a plurality of slots, each
slot of the plurality of slots disposed across at least one of the
first bend and the opposite parallel second bend; and wherein each
sheet of the plurality of sheets is arranged in a cross-wise
fashion relative to a vertically-adjacent sheet.
2. The packing system of claim 1, comprising a tab associated with
each slot of the plurality of slots, the tab being joined to
opposite edges of the slot and being deflected inwardly with
respect to the first bend and the opposite parallel second
bend.
3. The packing system of claim 2, wherein: the slot comprises a
width greater than or equal to 3mm; and the slot comprises an
actual length more than 50% of an unfolded length.
4. The packing system of claim 2, wherein the first bend and the
opposite parallel second bend are disposed at an angle between
approximately 30 degrees and approximately 60 degrees relative to a
horizontal plane.
5. The packing system of claim 2, wherein a ratio of pitch to
height of the first bend and the opposite parallel second bend is
at least 3.5.
6. The packing system of claim 2, comprising a plurality of first
bends, the plurality of first bends comprising the first bend.
7. The packing system of claim 6, wherein each first bend of the
plurality of first bends is spaced equidistant from a successive
first bend.
8. The packing system of claim 2, comprising a plurality of second
bends, the plurality of first bends comprising the opposite
parallel second bend.
9. The packing system of claim 8, wherein each second bend of the
plurality of second bends is spaced equidistant from a successive
second bend.
10. The packing system of claim 1, wherein the plurality of slots
are of substantially equal length.
Description
[0001] This patent application is a continuation of U.S. patent
application Ser. No. 13/819,923, which entered the national stage
in the United States on Feb. 28, 2013. U.S. patent application Ser.
No. 13/819,923 is national-stage application of PCT/IB2011/002695,
filed Sep. 1, 2011. PCT/IB2011/002695 claims priority to Japanese
Patent Application No. 2010-210050, filed Sep. 2, 2010. U.S. patent
application Ser. No. 13/819,923, PCT/IB2011/002695, and Japanese
Patent Application No. 2010-210050 are each incorporated herein by
reference.
TECHNICAL FIELD
[0002] This invention is concerning the packing for the purpose of
contacting liquid with vapor and promoting mass and heat transfer
between both fluids in the chemical process plant. The packing for
liquid and vapor to effectively contact is installed on the
distillation column, absorption tower, cooling tower and those kind
of devices, and both fluids contact each other on the surface or
the inside of each packing or outside spaces of packing. Though the
packing is used to mainly promote mass and heat transfer between
liquid and vapor in general, the chemical reaction might be
accompanied at the same time in this process. Distillation is used
most frequently among the unit operations to separate a product
component from a feeding mixture in chemical plant. In addition,
this kind of packings that promote mass and heat transfer is the
key internals as well as the tray in the distillation unit.
BACKGROUND OF THE INVENTION
[0003] The packing is divided roughly into two groups (random
packing and structured packing). Since the shape of random packing
is a specific geometrical discrete pieces, it is randomly dumped
and installed in the column. Meanwhile structured packing is
regularly crimped layers of wire or metal or plastic sheets. Those
sheets are composed of waved zonal laminas. Section of structured
packing are stacked into the column. This invention claims the
specific corrugated structured packing made of waved zonal
laminas.
[0004] Liquid is charged to the upper part of such packing layers
in the column and falls by gravity force, on the contrary vapor is
charged from the lower parts of packing layer in the column and
rises by pressure force. In this cycle mass and heat transfer
between both fluids is promoted by counter current contact of both
fluids on the packing layer. Liquid flows down uniformly on the
packing layer as a dispersed phase, though vapor rises on the
packing layer as a continuous phase. If liquid does not disperse
uniformly, transfer efficiency decreases. In addition channeling,
that means maldistribution of liquid flow, reduces transfer
efficiency remarkably since contact of both fluids is extremely
limited.
[0005] Liquid must be charged to the top of packing layer and
dispersed as the liquid droplet in order to flow down uniformly.
High performance liquid distributors are, of course, wanted, but
they can not control the behavior of the liquid within the
layer.
[0006] Performance (including shape) of the packing is the key
factor that influences liquid behavior because liquid descends
along the packing layer and it comes to a conclusion that packing
performance definitely determines transfer efficiency of the unit.
Liquid from distributor flows on the waved surface of each packing
element, and inside & outside space of the element and repeats
the current contact with rising vapor in the packing layer. Main
path of rising gas is the inclining ditched space that is
surrounded with the waved packing element. A considerable part of
the vapor that rises diagonally in ditched space ,intersects the
crease of the elements, then moves to ditched space on the waved
surface side of the adjacent element that intersects the previous
direction. Vapor rises along zigzag path in the packing layer like
this. Other than the above main path, vapor rises through the
opening holes on the packing surface.
[0007] If passing of vapor through the opening hole can induce
turbulence of liquid, mass transfer around near liquid interface
will be enhanced. On that reason many existing structured packing
have an opening holes on the waved surface. The role of the opening
is not only to promote the mass transfer as mentioned, but also for
liquid to easily enter to the back side of waved surface and to
spread widely on the waved surface by detour of opening holes. That
is the reason why the opening on the surface has a great effect on
liquid flow pattern.
Patent Documents
[0008] U.S. Pat. No. 4,710,326
[0009] In description of preferred embodiments, the interior angle
of the fold forming a corrugation is recommended to be less than 90
degrees, and about 60 degrees is suggested. As for the interior
angle of 60 degrees, the value of P/H (later will be defined)
corresponds to 1.15. It seems to be the minimum value of P/H among
disclosed or existing packing. Moreover, the relation between P/H
and the slot is not referred.
Literature Other Than Patent
[0010] 2007 Spring AIChE Meeting `REACHING NEW PERFORMANCE LEVELS
WITH SURFACE ENHANCED RASCHING SUPER--PAK STRUCTURED PACKINGS`
[0011] According to the attached photos, the direction of slot is
diagonal not horizontal. Moreover structural details of other
information such as P/H etc. are uncertain.
Literature Other Than Patent
[0012] HENRY Z. Kister, `DISTILLATION DESIGN`, McGraw-Hill,
Inc.
[0013] It is described that P/H of the structured packing are from
2 to 4. The slot is not described.
Literature Other Than Patent
[0014] Yano akira, `A RECENT TREND OF THE DISTILLATIION APPARATUS
AND THE PACKING FOR THE DISTILLATION COLUMN`, PETROTECH, 1990,
MARCH, 13th vol. No. 13, p 55.
[0015] According to the above chapter, P/H of the existing
structured packing is around 2, and holes of 3.8 mm in diameter are
used on the surface of corrugated sheets.
OUTLINE OF INVENTION
Problem to be Solved
[0016] In the existing structured packing, mass transfer between
liquid and vapor is promoted by wetted surface area, not
re-coalesce of liquid droplet since there are few liquid droplet.
That is, performance of the existing structured packing depends on
effective contacting area. In large surface tension system such as
including a lot of water, it is difficult for surface of packing to
be well wetted and for effective wetted area to be kept. Therefore,
the existing structured packing can not perform well in the large
surface tension. In order to understand the behavior of liquid flow
in the existing structured packing, this inventors executed a
systematic fluid flow experiment concerning the rate of liquid that
moved to the back surface through the opening holes on the waved
surface. As a result the rate to back surface was extremely limited
and the majority of liquids detoured around the opening and
fell.
[0017] Since the waved surface inclines not only in the diagonally
downward direction of the crease but also in the direction of
traversing the waved surface, the part of falling liquid that
detours the opening does not always keep staying on the same
surface and intersects the crease before long.
[0018] Once liquid leaves the inclined surface and falls near the
crease, liquid tends to continue falling near the crease and hardly
return to the inclined waved surface.
[0019] As the result of flow experiment of the existing structured
packing, the rate of bypassing liquid that intersects the crease
and falls nearly straightforward is more than imagined. One reason
is that major part of liquid does not flow into the openings, but
detours the openings and intersects the crease. Such bypassing is
called channeling that directly reduces contacting interfacial area
and efficiency. The experiment showed that performance of the
existing packing would increase if channeling were protected. In
details the existing packing encounters low efficiency against
relatively high liquid load, especially in high pressure service
where liquid relative volumetric load becomes higher compared with
in low pressure condition since vapor volumetric load goes smaller
by pressurization.
[0020] In addition, higher liquid load is apt to choke the opening
holes on the waved surface and has smaller wetted area per liquid
load since wetted area is constant in the existing packing. With
flow experiment using visible apparatus, several kind of packing
and air-water and air-hydrocarbon fluids, this inventors observed
that detouring liquid around the opening holes flows relatively
calm and smooth. If liquid enters the opening holes, mass transfer
is promoted and generation of liquid droplet accelerates this
tendency.
[0021] In the experiment, the diameter of circular opening was
changed for the purpose of the observation of liquid flow pattern
on the several types of corrugated structured packing that is made
of metal sheet 0.1 mm in thickness. The waved angle of gradient was
45 degrees and specific surface area was 250 m2/m3 in this
experiment that made match with the popular existing structured
packing. Generally, when the opening area was small, the tendency
that the opening was covered with the liquid thin film, and the
flowing liquid jumped over this part, was observed. In this case,
the rate of liquid that moved to the back side of waved surface and
bypassed the opening was extremely low. For higher liquid loads
even the circular opening (=hole) of about 4 mm in diameter in the
popular existing packing tends to be covered with the liquid film
as well as the smaller holes. Liquid film phenomenon in this
opening is considered to be one cause of the low performance. When
liquid load was lowered up to the range usually industrially
operated, the opening was not covered with the liquid film. However
in this case extremely low liquid load flows into the opening and
many parts of liquid was observed to fall in such a way to detour
the opening. It was recognized that the opening has the role for
liquid to detour and diffuse horizontally, resulting in increase of
wetted area of packing.
[0022] It was confirmed that the rate of flowing liquid into the
backside of opening is higher as the hole diameter becomes
extremely larger and these rate greatly depends on the opening
area. The rate of falling liquid that intersected the crease did
not always decrease in case when both hole diameter and the rate of
inflowing liquid increased. This is considered because the increase
of the opening area promotes the horizontal diffusion of
liquid.
[0023] Moreover, since liquid load that detoured to the waved
surface on the same table as liquid flow in the downstream
following the lower semicircle opening decreased with an increase
of the opening area, the opening area was not wetted by liquid and
became a dry condition.
[0024] It was clarified also that there was a limit in attempting
the improvement of the waved structured packing by enlarging an
opening area due to such reason. Moreover, the waste amount of the
material increases as the opening space increases, resulting in the
excessive need of material. With an increase of the inflowing
liquid to the opening, liquid not only moves to the backside of the
waved surface, but also are apt to fall to another waved surface
located further below through the space. In such process that flow
pattern changes, the possibility of liquid dispersion increases. If
liquid disperses into liquid droplet, they joined each other and
re-coalesce occurs. Such frequent dispersion and re-coalesce of
liquid droplet makes repeated interfacial update and promotes mass
transfer. Liquid load that flows to the circular opening (about 4mm
in diameter) adopted to the large part of the existing structured
packing, is limited and the problem is how to increase liquid
load.
Means of Solving the Problems
[0025] The existing packing has not been able to perform well in
separating components with large surface tension that is greatly
influenced by the wetness on the surface of the packing. Moreover,
the existing packing has been rarely used for such a unit because
of remarkable low performance in distillation using relatively
higher liquid load as those under high-pressure condition.
Experiment showed the following cause of poor performance in high
liquid load: [0026] (1) The rate of liquid that intersects the
crease of waved surfaces increases. [0027] (2) Liquid tends to
cover the opening. [0028] (3) Effective transfer area per liquid
rate don't increase with liquid load.
[0029] However, it is difficult to increase contacting area in
proportion to an increase of liquid load.
The decrease of contacting area can be compensated by the
dispersion and re-coalesce of liquid droplet. That is, promotion of
mass transfer through frequent interfacial update can make amends
for decreasing relative contacting area.
[0030] Since dispersion and re-coalesce of liquid droplet can be
promoted as flowing rate of liquid in the opening increases,
contrivance of how to positively introduce liquid to the opening is
needed. When the distance of between a peak and an adjacent peaks,
or a trough and an adjacent trough is defined as pitch (P) and the
distance of between a peak and an adjacent trough is defined as
height (H), P/H of the existing packing is the small value of such
as roughly 2.0 to 2.5. Oppositely in the packing of this invention
extremely large value of P/H is used to solve several problem as
mentioned. However, such large P/H has been pointed out to have
defects to decrease transfer efficiency rapidly as liquid load
increases. This inventors observed the relation of P/H (from 2 to
5) and liquid load intersecting the waved surface, overflows the
lower crease and finally falls to a free space.
[0031] When the value of P/H is 3.0 or more, the rate of
free-falling liquid increased more rapidly, compared with in the
range of 2.5 or less. At 3.5 or more and near about 4.0 of P/H
value, the rate of free-falling liquid extremely increased.
[0032] This inventors tried to reverse the direction of the liquid
flow intersecting the crease of the waved surface before the liquid
intersected. If the direction of liquid flow can be reversed,
liquid can be prevented from intersecting the crease and falling to
a free space. If this becomes possible, the structured packing can
be used regardless of the P/H value. This inventors arranged many
openings at the top and bottom of waved sheets along the crease as
a method of reversing the flow direction.
[0033] Major parts of liquid that flows in the opening, can fall to
another lower waved sheets through the opening.
[0034] Since the intersecting direction of another waved surface to
which liquid falls is inverse to the of present direction of waved
sheets, flowing liquid turns over.
[0035] Thus, it becomes possible for liquid to intersect the wave
surface repeatedly. In this invention high load liquid are apt to
intersect the waved surface because the value of P/H is extremely
larger than the existing waved surface. On the other hand, in the
existing packing the rate of flowing liquid diagonally downward on
the waved surface is large since P/H is a comparatively small
value. As mentioned, the value of P/H affects the flow pattern on
such the waved surface. If the rate of liquid falling diagonally on
the waved surface increases, liquid falls rapidly since velocity is
accelerated because of one-sided direction. In addition, since the
liquid flow that slowly intersects the waved surface decreases,
liquid doesn't diffuse enough on the waved surface, and the
contacting area decreases. On the other hand in this invention with
large value of P/H, there is an effect of wetting the waved surface
in the downstream of the opening from horizontal direction because
the liquid flows diagonally from the horizontal direction and is
easy to enter the opening. The most important point of this
invention is for liquid to frequently intersect the crease of the
waved surface with large value of P/H and to have the reversal
mechanism to prevent liquid flow from overflowing the crease of the
waved surface. Liquid volumetric load relatively increases as vapor
density increases under high pressure condition. When liquid load
increases in the existing packing, owing to increase of liquid
height and hydraulic resistance liquid tends to intersect the
crease and fall to a free space and relative contacting interfacial
area per liquid decreases. However in case of this invention liquid
tends to flow into the opening and avoid falling to a free space at
higher load. The mass transfer mechanism of this invention depends
not only on the contacting area (the same as the existing packing),
but also on dispersion and re-coalesce of liquid droplet in the
case when liquid passes the opening. Therefore, in this invention,
interfacial update between liquid and vapor that is promoted by
increasing liquid load to the opening, can compensate the decrease
of relative wetted area. According to the above-mentioned
experiment, the liquid rate flowing in the round opening is
increasing as the area increases. Then, this inventors experimented
on shape in the opening of the square the title line of which is
diagonally straight in place of the circle. In this case liquid
tends to fall along the inclined cut as is the case of the round
opening and increasing tendency of the rate of liquid is confirmed
as the angle of this straight cut is horizontally brought close to
horizontal level.
[0036] Liquid that flows into the horizontal cut hardly goes to one
direction alone different from into the inclined cut or the circle.
Therefore, liquid is apt to extend to both right and left sides of
the cut equally. Such horizontal movement is not accelerated by
gravity, and the velocity that extends to side direction becomes
slow compared with the case of the inclined cut. Liquid accumulates
and liquid head becomes high if the liquid flows continuously into
the part of horizontal cut. The liquid moves to both sides of the
cut to be in the liquid thin film form because gravity works as
leveling action to the liquid volume. The liquid tends to diffuse
horizontally along with the horizontal upper line of the cut. The
liquid thin film will increase the thickness before long, and it
falls to an open mouth space that is surrounded by the lower line
of the cut. The extent of liquid falling from the cut depends on
the balance between working gravity and surface tension. Liquid
falls when the gravity force of increasing liquid load overcomes
surface tension to maintain liquid. This phenomenon becomes
intermittent, not continuous, and therefore liquid becomes droplet
and tends to fall. In the opening with the horizontal upper line,
liquid can easily flow in and diffuse horizontally and pass the
waved surface as droplet. In the round opening used in the existing
packing, the rate of liquid flowing in the opening is limited, and
major parts of liquid tends to detour the opening. The
above-mentioned finding by the flow experiment concluded that upper
line of cut is horizontal or near so in shape different from the
existing packing. Liquid flowing in the opening with the horizontal
upper cut passes the below open mouth space as droplet. While parts
of flowing liquid are adhering to the back side of the opening, the
majority falls to another waved surface below. The fallen liquid
joins other liquids and this assembly forms the liquid thin film on
this waved surface. Through such repetition, dispersion to the
liquid droplet and the re-coalescence to the liquid thin film
frequently happen. The interface between liquid and vapor is
frequently updated by dispersion and re-coalescence in the packing
of this invention. The composition difference (that is driving
force of mass transfer) between liquid and vapor occurs when
interface is updated by new fluids. Frequent dispersion and
re-coalesce of liquid droplet is convenient for promoting mass
transfer and the shape of the opening used in this invention offers
the desirable flow characteristic.
[0037] Moreover, because the inflow of the liquid to the opening
easily falls diagonally from the horizontal direction of the waved
surface, it can wet the waved surface in the downstream of the
opening from horizontal direction. This is a result of enlarging
the value of P/H as already described. In this invention the
downstream of the opening comes not to be dried up because of many
openings installed along the waved surface and of horizontal flow
direction owing to large P/H. As for the cut direction to consist
the slots on the surface, it is most preferable to be the
horizontal. However, performance doesn't always decrease extremely
so long as it is near horizontal. It is not allowed that upper line
of the cut inclines rapidly downward even if it is a little part.
Since a lot of liquid falls from the opening where the cut is
rapidly changed, the diffusion of the liquid to horizontal
direction is intercepted. Shape of the opening described in the
claim is that such a qualitative fact was materialized. Further
details are determined after the distillation experiment with
actual fluid was performed using the actual packing based on the
finding of the flow experiment.
Advantageous Effect of the Invention
[0038] In the existing structured packing, wetted area plays an
chief role in promotion of mass transfer and keeping an enough
wetted area become difficult for large surface tension (hard to be
wetted) system such as with a large amount of water. In this
invention, besides wetted area, mass transfer is accelerated by
frequent interfacial update. Since the dependence of mass transfer
on wetted area is limited in the packing of this invention, it can
be used regardless of the range of surface tension.
[0039] As for the packing of this invention, many regular opening
are arranged with the horizontal slots and tabs on the waved
surface. Liquid in the waved surface is easy to flow in the slots
in this packing, and diffuses to horizontal direction around the
upper line of slot, and tends to fall as droplet in dispersion
phase.
[0040] Different from the existing packing, mass transfer becomes
more effective as falling liquid joins other liquids in new surface
and dispersion and re-coalescence of liquid droplet are repeated
for liquid and vapor interface to be frequently updated. The
existing packing has been hardly used for high liquid load system
under high pressure condition since both wetted area per liquid and
mass transfer efficiency decrease.
[0041] The structured packing of this invention can be applicable
for higher liquid load since the effect of wetted area is
relatively small and mass transfer increases.
[0042] In the existing structured packing, it turned out that high
liquid load intersecting the crease are easy to fall to a free
space and difficult to return to the waved surface. For even not
high liquid load, since liquid is apt to fall diagonally, liquid is
likely to be gathered to the column wall and to continue flowing
near the wall. This means bypassing of the waved sheets and
channeling.
[0043] The structured packing of this invention solves the above
problems and minimizes channeling by not overflowing the crease,
but flowing into horizontal slots.
[0044] Distributor becomes unnecessary or minimum though
re-distributor per each specified height is necessary to avoid
channeling in the existing packing. The packing of this invention
turned out that the separation efficiency improved with an increase
of liquid according to the actual distillation experiment over the
wide range with actual fluids. This shows that frequent dispersion
and re-coalesces of liquid droplet promotes an interfacial update
with an increase of liquid load. Generally in the existing packing
the separation efficiency decreases with an increase of liquid
load.
[0045] In higher liquid load this decrease seems to be caused from
that (1) effective wetted area per liquid decreases and that (2) a
kind of channeling becomes remarkable. Regarding capacity in
liquid-vapor refining unit such as distillation column, the
flooding point is an operational upper limit. In the existing
structured packing, the separation efficiency decreases as liquid
load increases. Therefore, the separation efficiency might fall
under the specified value before flooding is encountered. The
maximum throughput for this case is determined by not the flooding
point, but the allowable lower limit of efficiency. In the packing
of this invention, wide operational range becomes possible since
separation efficiency improves with increase of liquid load to
flooding point.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] [FIG. 1] Explanation concerning drawing of tray tower
[0047] In such a liquid and vapor contacting operation, the working
unit that arranges a lot of trays from top to bottom in cylindrical
column {circle around (1)} is generally called a tray tower.
[0048] In tray tower tray {circle around (2)} holds the descending
liquid from the upper tray and to which ascending vapor from the
lower tray is entered, and on which both liquid and vapor are
contacted.
[0049] [FIG. 2] Explanation concerning drawing of packing tower
[0050] In the packing tower, mass transfer is performed through
contact between the descending liquid and ascending vapor in
packing {circle around (1)} layers installed in cylindrical column.
Since the packing tower has the merit of better performance of mass
and heat transfer and lower pressure loss compared with tray tower,
the packing has come to be used in place of the tray in accordance
with the object.
[0051] [FIG. 3] Structure of the corrugated structured packing
[0052] In large majority of structured packing including the
metallic lamina and the wire net, etc., a lot of round openings are
arranged in the plane of a zonal material beforehand, and formed
and manufactured as the inclined shape of waves {circle around
(1)}, {circle around (2)} in the long direction that bends to an
alternate inside and outside at a regular interval and the angle.
Many pieces of the corrugated sheets are made by cutting the waved
lamina material obtained thus. These prescribed number of sheets is
piled as the multi-layers. At the same time the packing in the
block form is constructed such that they are united for inclination
of the adjacent waves of the element to be mutually intersected. In
general, the packing layer is formed such that the packing of the
block form is piled up to multi-layers vertically in the column.
The waved surface of each element that composes the packing layer
is arranged so that the wide direction of elements vertical in the
column. ({circle around (1)}, {circle around (2)})
[0053] [FIG. 4] Constitution of packing layer
[0054] The horizontal cross section is a circle in the majority of
liquid-vapor contactors including the distillation column, and the
packing is provided with the stratified pile form in the tower.
First of all, the blocks of packing are installed thoroughly in the
horizontal section in the tower. In general, the blocks of packing
are paved according to the inside diameter of the tower though the
block of 1 piece is used when the inside diameter of the tower is
small. When plural blocks are used, blocks of different shape are
combined to become a circle in the whole horizontal section. The
block of 1 piece or two or more packing element paved over the
horizontal cross section in the tower is assumed to be one layer
like this, the packing layer is composed that is piled with
multi-layer in the vertical direction in the tower({circle around
(1)} is a part of {circle around (2)}).
[0055] [FIG. 5] Pitch (P) and height (H) of packing element
[0056] Horizontal distance ({circle around (1)}) of the crimp that
is from the top of the crease of the waved surface to adjacent top
of the one, or from bottoms of the one to adjacent ones is defined
as pitch (P). Vertical distance ({circle around (2)}) of the crimp
that is from the peak of the crease to the line of troughs or from
the trough of the crease to the line of peaks is defined as height
(H).
[0057] [FIG. 6] Relation between P/H and liquid flow pattern
[0058] Face AA `BB` and face BB `CC` are assumed to show the waved
surface connected with both sides of BB' that corresponds to the
crease. Triangle ABC is congruent with triangle. A'B'C'. BH is the
perpendicular line from top B in triangle ABC, the length of which
is the height (=H) of the crimp. Length AC is the pitch (=P) of the
crimp.
[0059] Virtual plane AA'CC' made of crease AA' and CC' is a
perpendicular plane as well as the packing form in the tower. If
length (=P) of AC is assumed to be constant and length (=H) of BH
is changed, the value of P/H can be changed. Crease AA `BB` and CC'
are mutually in parallel. The relation between the movement of the
particle and the value of P/H as shown with AD when the particle is
put on point A on the table side of waved surface AA `BB` here. A
horizontal inclination of this waved surface becomes small and this
particle is about to cross the crease BB' in a short time since
waved surface AA `BB` approaches plane AA `CC` vertical to BH if
the length of BH is reduced. If the length of BH is enlarged
oppositely, waved surface AA `BB` goes away from plane AA 'CC, and
then it takes time to cross the crease. The liquid flows away from
the crease BB' and falls the surface near AA' side when the length
of BH is enlarged and the value of P/H is reduced further. Liquid
load increases that crosses the waved surface and jumps over the
crease if oppositely the value of P/H is enlarged and the
inclination to horizontal direction is reduced. Liquid flow pattern
is determined depending on the value of P/H like this.
[0060] [FIG. 7] Display of ridge line
[0061] {circle around (2)} is a polygonal curve. {circle around
(3)} is the ridge line of peaks and {circle around (1)}, {circle
around (5)} are the ridge lines of troughs and {circle around (4)}
is a side parts of the wave.
[0062] [FIG. 8] General relation of slot dimension
[0063] These figures are showing of slots of the limited number to
make clear a general relation of slot dimension before fabrication.
Planes surrounded with continuous peaks or troughs are defined as
element. Two horizontal line intersecting crease is pressed to
become the banded opening, that is defined as tab 9 and empty
square is defined as slot 10. When horizontal length ({circle
around (6)}) is assumed to be `a` and distance from the crease to
adjacent crease({circle around (5)}) is assumed to be `c` , a
.gtoreq.0.5 c shall be confirmed. Moreover, d.gtoreq.3 mm shall be
confirmed when the distance in the vertical direction ({circle
around (3)} and {circle around (4)}) in the slot is assumed to be
`d`. In addition, FIG. {circle around (1)} shows the long direction
of sheet material and the dotted line exhibits the polygonal curve
and the crease (peaks or troughs) of waved surface.
[0064] [FIG. 9] Relation of F factor and HETP
[0065] {circle around (2)} shows the tendency of the existing
structured packing.
[0066] {circle around (1)} is of this packing and shows the
behavior that HETP improves with increase of liquid load, that is
different from the existing.
Form to Practice Invention
[0067] P/H is 3.5 or more in the packing of this invention.
Moreover, if shape of the upper cut of the slot is near horizontal,
the performance of the packing of this invention may be satisfied.
However, it is preferable that this cut is the horizontal and
straight considering easy manufacturing. Especially, in order to
omit the monitoring task when they are assembled to the shape of
waves and united like the block, both not only the top but also the
bottom of the slot are preferably located side by side by the
parallel straight line. Width of horizontal cut of the top and
bottom of the slot is described in claim -1. A higher performance
can be expected by making it wide as much as mechanical strength
permits within this range. As for the liquid, the possibilities of
inflowing to the slots becomes larger if this width becomes wider.
Interval length (=depth) of upper and lower side of the slots shall
be determined according to the design liquid load of the unit. In
the packing of this invention, the frequency of interfacial update
between liquid and vapor increases and contacting performance
improves as liquid flowing to slots becomes frequent. This update
can increases as the interval between upper and lower openings
approaches. On the other hand, since liquid flows in from upward
diagonally to the slot on waved surface, liquid accumulates in
front of upper line of the slot and hardly spreads around the upper
line if location of slot and the adjacent slot below is too close.
If the interval between the slots is narrow as for liquid load,
both bridging and liquid jumping of the slot makes performance to
decrease. If the interval is wide as for liquid load, reduction of
effective area makes performance to decrease, too. Bridging happens
even for extremely low liquid load in case when depth of slots is
narrow, for example 2 mm etc. It is necessary to avoid 3 mm or less
for depth of the slots from the observation of the experiment. The
upper depth boundary is not limited and depth from 6 to 10 mm is
considered to be passable. But for the range of liquid load used in
the existing packing, depth from 4 to 5 mm is desirable.
[0068] The existing structured packing often uses emboss
fabrication on surface to widely disperse liquid and to increase
contacting efficiency, while in the packing of this invention such
a surface fabrication is not meaningful since mass and heat
transfer mainly depends on not wetted area, but dispersion and
re-coalesces of liquid droplet. Though this invention is made clear
more concretely hereafter based on the embodiments, this invention
is not limited to them.
Embodiment 1
[0069] Various zonal materials such as metallic lamina, wire net,
and board plastic can be used in the packing of this invention as
well as the existing so far. The embodiment according to claim -1
is described as follows here.
[0070] Material: A stainless metallic lamina of 0.1 mm in
thickness
[0071] Pitch of element: 48.2 mm and Height of element: 11.6 mm
(P/H: 4.2)
[0072] Depth of the horizontal upper and lower slot: 4 mm
[0073] Specific surface area: 214m2/m3
[0074] Total reflux distillation was performed by using the same as
the above-mentioned structured packing under the atmospheric
pressure with binary components (water/acetic acid) system. The
following operating data were obtained as a result.
TABLE-US-00001 Run 1 Run 2 Run 3 Run 4 Run 5 F factor
m/s(kg/m.sup.3).sup.0.5 1.634 1.938 2.661 2.903 3.403 HETP mm 479
457 475 479 453 Pressure Pa/m 127 185 362 538 859 loss
[0075] It is an application example to the with large surface
tension system including water. The separation performance of this
packing was confirmed to be excellent since HETP was found to be
453.about.479 mm, on the other hand in the existing conventional
packing (Specific surface area is 250 m2/m.3), HETP was
600.about.650 mm.
[0076] Different from the existing structured packing, the behavior
was observed that HETP of this packing was decreasing with an
increase of F factor.
[0077] This F factor shows the capacity of the treating gas and
defined by the density of vapor multiplied by the square of a vapor
superficial velocity in the column and proportional to the capacity
of the treating gas.
Embodiment 2
[0078] The absorption experiment was performed by using the same as
embodiment 1 structured packing under the atmospheric pressure in
water/acetone/three air components system, and compared with Paul
Ring 1-1/2B under the same condition. The following operation data
were obtained as a result.
TABLE-US-00002 This packing Pall Ring 1-1/2B Acetone entrance vol %
1.824 1.827 Acetone exit vol % 0.023 0.185 HETP mm 900 1800
UnitPressure loss Pa/m 186 314 F factor m/s(kg/m.sup.3).sup.0.5 1.3
1.3 liquid rate m.sup.3/m.sup.2 h 55 55
[0079] It is an application for the absorption tower handling high
liquid load.
[0080] Near half value of HETP and pressure loss were obtained
compared with the typical conventional random packing (Paul Ring
1-1/2B).
[0081] For reference the existing structured packing showed poor
performance for high liquid load, for example over than 30
m.sup.3/m.sup.2h.
Embodiment 3
[0082] Total reflux distillation was performed by using the same as
embodiment 1 structured packing in [chloric benzene, ethyl benzene
system]. The following operation data were obtained under the
atmospheric pressure condition.
TABLE-US-00003 Run 1 Run 2 Run 3 Run 4 F factor
m/s(kg/m.sup.3).sup.0.5 1.459 2.024 2.558 2.899 HETP mm 249 253 234
205 Unit pressure Pa/m 186 283 619 1043 loss
[0083] The separation performance of this packing was confirmed to
be excellent since HETP was found to be 205-253 mm, on the other
hand in the existing conventional packing (Specific surface area
250 m2/m3), HETP was 300.about.350 mm.
[0084] Similar with the embodiment 1, the behavior was observed
that HETP of this packing was decreasing with an increase of F
factor.
[0085] Moreover, the following operation data were obtained in
total reflux distillation at vacuum pressure (100 mmHgA) in the
same apparatus and fluids.
TABLE-US-00004 Run 1 Run 2 Run 3 Run 4 F factor
m/s(kg/m.sup.3).sup.0.5 2.095 2.593 3.256 3.834 HETP mm 246 251 238
202 Unit pressure Pa/m 192 342 651 1336 loss
[0086] The tendency that HETP decreases with increase of F factor
was observed as well as at atmospheric pressure. High capacity was
proven since flooding did not occur even if F factor becomes 3.8 or
more.
INDUSTRIAL APPLICABILITY
[0087] Unit operation of liquid and vapor separation,
representative of which is distillation, is mostly used as well as
heat transfer and reaction. As the internals of separation unit,
structured packing is spreading in use since it has better
efficiency and lower pressure loss compared with tray. But
structured packing has the limitation of the treating system and
operating range. In this regard the packing of this invention not
only has efficiency higher than existing structured packing in
usual operating range, but also can be used for large surface
tension system and higher liquid load range that were inadequate
for the existing structured packing. By applying this invention,
economics of total plant unit can improve since the reduction of
plant installation cost and energy conservation in itself are
expected owing to drastic increase separation efficiency. The
packing of this invention can be replaced for tray by wide
application and progress of the economy.
* * * * *