U.S. patent application number 14/372584 was filed with the patent office on 2015-01-15 for solvent separation method.
This patent application is currently assigned to KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.). The applicant listed for this patent is Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.). Invention is credited to Shigeru Kinoshita, Noriyuki Okuyama, Koji Sakai, Takuya Yoshida.
Application Number | 20150013215 14/372584 |
Document ID | / |
Family ID | 48904964 |
Filed Date | 2015-01-15 |
United States Patent
Application |
20150013215 |
Kind Code |
A1 |
Sakai; Koji ; et
al. |
January 15, 2015 |
SOLVENT SEPARATION METHOD
Abstract
A method for separating solvent-containing water, which is
generated in the process for producing an ashless coal, into a
solvent and water readily without using any adsorbent or the like
(a solvent separation method). The solvent separation method
comprises: a solvent-containing water supply step of supplying the
solvent-containing water into a pressure vessel for solvent
separation purposes; and a temperature retention step of retaining
the temperature of the solvent-containing water that has been
supplied into the pressure vessel for solvent separation purposes
at a predetermined temperature (e.g., 100 to 180 DEG C. inclusive).
In the pressure vessel for solvent separation purposes, water in
the liquid form moves downward and the solvent moves upward due to
the difference between the density of water and the density of the
solvent at the predetermined temperature. In this manner, the
solvent-containing water can be separated into the solvent and
water.
Inventors: |
Sakai; Koji; (Hyogo, JP)
; Okuyama; Noriyuki; (Hyogo, JP) ; Kinoshita;
Shigeru; (Hyogo, JP) ; Yoshida; Takuya;
(Hyogo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) |
Hyogo |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA KOBE SEIKO SHO
(KOBE STEEL, LTD.)
Hyogo
JP
|
Family ID: |
48904964 |
Appl. No.: |
14/372584 |
Filed: |
January 9, 2013 |
PCT Filed: |
January 9, 2013 |
PCT NO: |
PCT/JP2013/050180 |
371 Date: |
July 16, 2014 |
Current U.S.
Class: |
44/627 |
Current CPC
Class: |
C10L 2290/52 20130101;
C10L 1/326 20130101; C10L 2290/544 20130101; B01D 17/0205 20130101;
C10L 2290/46 20130101; B01D 17/0214 20130101; C10L 9/02 20130101;
C10L 9/08 20130101; C10L 2290/547 20130101; B01D 17/042
20130101 |
Class at
Publication: |
44/627 |
International
Class: |
C10L 9/02 20060101
C10L009/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 1, 2012 |
JP |
2012-019488 |
Claims
1. A solvent separation method for separating solvent-containing
water, which is generated in the process for producing an ashless
coal, into a solvent and water, the method comprising: an
extraction step of extracting a solvent-soluble coal component by
heating a slurry obtained by mixing a coal and the solvent; a
separation step of separating a solution containing the
solvent-soluble coal component from the slurry obtained in the
extraction step; and an ashless coal acquisition step of obtaining
an ashless coal by vaporizing and separating the solvent from the
solution separated in the separation step, wherein a
solvent-containing water supply step of supplying the
solvent-containing water into a pressure vessel for solvent
separation purposes and a temperature retention step of retaining
the temperature of the solvent-containing water that has been
supplied into the pressure vessel for solvent separation purposes
at a predetermined temperature are included; and the
solvent-containing water is separated into the solvent and water by
moving water in the liquid form downward and moving the solvent
upward in the pressure vessel for solvent separation purposes due
to the difference between the density of water and the density of
the solvent at the predetermined temperature.
2. The solvent separation method according to claim 1, wherein in
the temperature retention step, the temperature of the
solvent-containing water is retained at the predetermined
temperature and the solvent-containing water is allowed to
stand.
3. The solvent separation method according to claim 1, wherein in
the temperature retention step, the temperature of the
solvent-containing water in the pressure vessel for solvent
separation purposes is retained at a temperature of 100 to 180 DEG
C. inclusive.
4. The solvent separation method according to claim 1, wherein the
pressure in the pressure vessel for solvent separation purposes is
specified to be a pressure higher than the saturated vapor pressure
of water.
5. The solvent separation method according to claim 1, wherein an
inert gas is filled in the pressure vessel for solvent separation
purposes.
6. The solvent separation method according to claim 1, wherein the
solvent-containing water, which is generated in the extraction step
in the process for producing an ashless coal, is supplied to the
pressure vessel for solvent separation purposes.
7. The solvent separation method according to claim 2, wherein in
the temperature retention step, the temperature of the
solvent-containing water in the pressure vessel for solvent
separation purposes is retained at a temperature of 100 to 180 DEG
C. inclusive.
8. The solvent separation method according to claim 2, wherein the
pressure in the pressure vessel for solvent separation purposes is
specified to be a pressure higher than the saturated vapor pressure
of water.
9. The solvent separation method according to claim 2, wherein an
inert gas is filled in the pressure vessel for solvent separation
purposes.
10. The solvent separation method according to claim 2, wherein the
solvent-containing water, which is generated in the extraction step
in the process for producing an ashless coal, is supplied to the
pressure vessel for solvent separation purposes.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for separating
solvent-containing water, which is generated in the process for
producing an ashless coal by removing ash from a coal, into a
solvent and water.
BACKGROUND ART
[0002] Examples of methods for producing an ashless coal include a
method described in PTL 1. PTL 1 describes a method for producing
an ashless coal, wherein a slurry is prepared by mixing a coal and
a solvent, a solvent-soluble coal component is extracted by heating
the resulting slurry, a solution containing the solvent-soluble
coal component is separated from the slurry, from which the coal
component has been extracted, and thereafter, an ashless coal is
obtained by recovering the solvent from the separated solution. An
oil component derived from a coal is used as the solvent.
CITATION LIST
Patent Literature
[0003] PTL 1: Japanese Unexamined Patent Application Publication No
2005-120185
SUMMARY OF INVENTION
Technical Problem
[0004] Here, in the above-described process for producing an
ashless coal, water (H.sub.2O) is produced from the coal serving as
a raw material. In the extraction of the coal component, the slurry
is heated to a temperature of, for example, 300 to 420 DEG C. The
coal undergoes a thermal decomposition reaction under such high
temperatures, and methane (CH.sub.4), carbon dioxide (CO.sub.2),
water (H.sub.2O), and the like are produced. Also, the coal serving
as a raw material contains water in the first place, and the water
is separated from the coal in extraction of the coal component with
the solvent.
[0005] The water (H.sub.2O) produced from the coal through thermal
decomposition and the water (H.sub.2O) separated from the coal in
extraction of the coal component are discharged as a gas (water
vapor) to the outside of the system of an ashless coal producing
facility, while much solvent is present in the gas
(solvent-containing water). Therefore, if the gas concerned is
entirely discarded, a solvent loss increases significantly, and
fresh supplementation of much solvent becomes necessary. As a
result, the running cost increases.
[0006] Meanwhile, in order to discard the gas containing the
solvent, for example, a treatment to remove the solvent from the
gas by using an adsorbent is necessary, and in the case where the
amount of solvent contained in the gas is large, the treatment cost
increases significantly. Also the solvent adsorbed by the adsorbent
is not readily separated from the solvent. That is, reuse of an
adsorbent which has been used for the adsorption treatment is
difficult.
[0007] The present invention has been made in consideration of the
above-described circumstances, and it is an object to provide a
method capable of separating solvent-containing water, which is
generated in the process for producing an ashless coal, into a
solvent and water readily without using any adsorbent or the
like.
Solution to Problem
[0008] The present invention is a solvent separation method for
separating solvent-containing water, which is generated in the
process for producing an ashless coal, into a solvent and water,
the method including an extraction step of extracting a
solvent-soluble coal component by heating a slurry obtained by
mixing a coal and the solvent, a separation step of separating a
solution containing the solvent-soluble coal component from the
slurry obtained in the above-described extraction step, and an
ashless coal acquisition step of obtaining an ashless coal by
vaporizing and separating the solvent from the solution separated
in the above-described separation step. This solvent separation
method is characterized in that a solvent-containing water supply
step of supplying the above-described solvent-containing water into
a pressure vessel for solvent separation purposes and a temperature
retention step of retaining the temperature of the above-described
solvent-containing water that has been supplied into the
above-described pressure vessel for solvent separation purposes at
a predetermined temperature are included and the above-described
solvent-containing water is separated into the solvent and water by
moving water in the liquid form downward and moving the solvent
upward in the above-described pressure vessel for solvent
separation purposes due to the difference between the density of
water and the density of the solvent at the predetermined
temperature.
[0009] In this regard, the term "solvent-containing water" refers
to water in the state in which a solvent and water are mixed (mixed
state) regardless of a liquid state or a gas state. Also, the term
"is generated in the process for producing an ashless coal" is in
the sense of being generated as a by-product in any portion of the
process for producing an ashless coal.
Advantageous Effects of Invention
[0010] According to the present invention, the solvent-containing
water, which is generated in the process for producing an ashless
coal, can be separated into the solvent and water readily without
using any adsorbent or the like. As a result, the adsorbent can be
reused, the solvent loss can he reduced and, in addition, the water
disposal cost can be reduced.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a block diagram showing an ashless coal producing
facility provided with a pressure vessel for solvent separation
purposes to separate a solvent containing water into a solvent and
water.
[0012] FIG. 2 is a diagram illustrating the outline of a separation
test to separate a solvent-containing water into a solvent and
water.
[0013] FIG. 3 is a graph showing the results of the separation
test.
DESCRIPTION OF EMBODIMENTS
[0014] The embodiments according to the present invention will be
described below with reference to drawings.
[0015] As shown in FIG. 1, an ashless coal producing facility 100
is provided with a coal hopper 1, a solvent tank 2, a slurry
preparation vessel 3, a transfer pump 4, a preheater 5, an
extraction vessel 6, a gravity settling vessel 7, a filter unit 8,
and a solvent separator 9 sequentially from the upstream side of an
ashless coal (HPC) production process. The solvent separator 9
vaporizes and separates a solvent from a solution (supernatant
liquid) separated in the gravity settling vessel 7.
[0016] Also, on the downstream side of the gravity settling vessel
7, a solvent separator 10 to vaporize and separate the solvent from
a solvent-insoluble component concentrate (solid content
concentrate) separated in the gravity settling vessel 7 (to
separate and recover the solvent from the solid content
concentrate) is disposed.
[0017] Also, the ashless coal producing facility 100 is provided
with a pressure vessel for solvent separation purposes 11 to
separate the solvent-containing water into the solvent and water.
This pressure vessel for solvent separation purposes 11 is
connected to the extraction vessel 6 with a pipe 25. That is, in
the present embodiment, the solvent-containing water in the gas,
which is generated in the extraction step in the process for
producing an ashless coal, is supplied from the extraction vessel 6
to the pressure vessel for solvent separation purposes 11, so as to
be separated into the solvent in the liquid form and water in the
liquid form.
[0018] In this regard, the pressure vessel for solvent separation
purposes 11 may be connected to the gravity settling vessel 7
rather than the extraction vessel 6 with a pipe or the like. That
is, the solvent-containing water (the solvent is a liquid and the
solvent is mixed into the water vapor) in the gas, which is
generated in the extraction step, may be supplied from the gravity
settling vessel 7 to the pressure vessel for solvent separation
purposes 11, so as to be separated into the solvent and water.
Meanwhile, in the case where a very small amount of water is
generated in the gravity settling vessel 7, the solvent-containing
water generated here can be separated into the solvent and water in
the pressure vessel for solvent separation purposes 11 by
connecting the pressure vessel for solvent separation purposes 11
to the gravity settling vessel 7.
[0019] Furthermore, one pressure vessel for solvent separation
purposes 11 may be connected to both the extraction vessel 6 and
the gravity settling vessel 7, or each of the extraction vessel 6
and the gravity settling vessel 7 may be connected to one pressure
vessel for solvent separation purposes 11. In the case where water
remains in the slurry supplied to the gravity settling vessel 7,
the water can be removed by discharging the solvent-containing
water in the gas containing the solvent from the gravity settling
vessel 7 to the pressure vessel for solvent separation purposes
11.
[0020] Also, the pressure vessel for solvent separation purposes 11
may be connected to the slurry preparation vessel 3 with a pipe or
the like. This is because in the case where a coal containing much
water is handled, the slurry preparation vessel 3 is heated to 100
to 120 DEG C., which is in the vicinity of the boiling point of
water, to recover water from the coal through vaporization and,
thereby, the water concentration in the slurry transferred to the
extraction step can be decreased. The solvent-containing water
generated here can be supplied from the slurry preparation vessel 3
to the pressure vessel for solvent separation purposes 11, so as to
be separated into the solvent and water.
[0021] Also, a tank may be disposed at some midpoint of the pipe 25
connected to the pressure vessel for solvent separation purposes
11. The solvent-containing water is condensed once into a liquid in
the tank concerned (the solvent-containing water is condensed by
lowering the temperature of the solvent-containing water) and,
thereafter, water is vaporized from the solvent-containing water by
heating to a temperature higher than or equal to the boiling point
of water again. Thus a vapor (including the solvent) resulting from
concentration of the water is transferred from the tank concerned
to the pressure vessel for solvent separation purposes 11.
According to this step, the solvent concentration in the
solvent-containing water transferred to the pressure vessel for
solvent separation purposes 11 is reduced, and the solvent loss
factor can be further reduced. In this regard, the solvent
remaining in the tank is drawn from the tank and is reused.
[0022] Here, an ashless coal production method (process for
producing an ashless coal) includes an extraction step, a
separation step, and an ashless coal acquisition step. Each of
these steps will be described below and, in addition, a method for
separating the solvent-containing water, which is generated in the
process for producing an ashless coal, into the solvent and water
will be described. In this regard, the coal serving as a raw
material in the production of the ashless coal is not specifically
limited. A bituminous coal having a high extraction rate (ashless
coal recovery percentage) may be used or a cheaper bony coal
(sub-bituminous coal, brown coal) may be used. Meanwhile, the
ashless coal refers to a coal having an ash content of 5 percent by
weight or less, and preferably 3 percent by weight or less.
[0023] (Extraction Step)
[0024] The extraction step is a step of extracting a
solvent-soluble coal component through heating of the slurry
obtained by mixing the coal and the solvent, in the present
embodiment, this extraction step is divided into the slurry
preparation step of preparing the slurry by mixing the coal and
water and the solvent-soluble component extraction step of
extracting (dissolving into the solvent) a solvent-soluble coal
component by heating the slurry prepared in the slurry preparation
step.
[0025] In extraction of the solvent-soluble coal component through
heating of the slurry obtained by mixing the coal and the solvent,
a solvent having a large solvent power with respect to a coal,
which is an aromatic solvent (hydrogen donor solvent or solvent not
having a hydrogen donating property) in many cases, and a coal are
mixed and are heated, so that organic components in the coal are
extracted.
[0026] The solvent not having a hydrogen donating property is a
coal derivative which is refined mainly from a coal carbonization
product and which is a solvent primarily containing a bicyclic
aromatic. This solvent not having a hydrogen donating property is
stable even in a heated state, has excellent affinity for a coal,
where the proportion of a soluble component (here, a coal
component) extracted by a solvent (may be referred to as an
extraction rate) is high, and is a solvent readily recoverable by a
method of distillation or the like. Examples of primary components
of the solvents not having a hydrogen donating property include
naphthalene, methylnaphthalene, dimethylnaphthalene, and
trimethylnaphthalene, which are bicyclic aromatics. Components of
other solvents not having a hydrogen donating property include
naphthalenes, anthracenes, fluorenes, which have aliphatic side
chains, and in addition, biphenyls and alkylbenzenes having long
aliphatic side chains are also included in the solvent not having a
hydrogen donating property.
[0027] In this regard, in the case explained above, the solvent not
having a hydrogen donating property is used as the solvent.
However, as a matter of course, hydrogen donating compounds
(including coal liquefaction oil) typified by tetralin may be used
as the solvent. In the case where the hydrogen donor solvent is
used, the yield of ashless coal is improved.
[0028] The specific gravities of these solvents (ratio to the
weight of water having the same volume) is about 1 at room
temperature (ambient temperature).
[0029] Meanwhile, the boiling point of the solvent is not
specifically limited. Solvents having boiling points of, for
example, 180 to 300 DEG C., in particular 240 to 280 DEG C. are
used preferably from the view point of, for example, reduction in
pressures in the extraction step and the separation step, the
extraction rate in the extraction step, the solvent recovery
percentages in the ashless coal acquisition step and the like.
<Slurry Preparation Step>
[0030] The slurry preparation step is executed in the slurry
preparation vessel 3 shown in FIG. 1. The coal serving as a raw
material is put into the slurry preparation vessel 3 from the coal
hopper 1 and, in addition, the solvent is put into the slurry
preparation vessel 3 from the solvent tank 2. The coal and the
solvent put into the slurry preparation vessel 3 are mixed with an
agitator 3a to become a slurry composed ref the coal and the
solvent.
[0031] The mixing ratio of the coal to the solvent is, for example,
10 to 50 percent by weight in terms of dry coal, and more
preferably 20 to 35 percent by weight.
<Solvent-Soluble Component Extraction Step>
[0032] The solvent-soluble component extraction step is executed in
the preheater 5 and the extraction vessel 6 shown in FIG. 1. The
slurry prepared in the slurry preparation vessel 3 is once supplied
to the preheater 5 by the transfer pump 4, so as to be heated to
the predetermined temperature and, thereafter, is supplied to the
extraction vessel 6, where extraction is performed while agitation
with the agitator 6a and retention at the predetermined temperature
are performed.
[0033] The heating temperature in the solvent-soluble component
extraction step, is not specifically limited in so far as the
solvent-soluble component is dissolved and is, for example, 300 to
420 DEG C., and more preferably 360 to 400 DEG C. from the view
points of sufficient dissolution of the solvent-soluble component
and an improvement in extraction rate.
[0034] Also, the heating time (extraction time) is not specifically
limited but is, for example, 10 to 60 minutes from the view points
of sufficient dissolution and an improvement in extraction rate.
The heating time is a total of the heating times in the preheater 5
and the extraction vessel 6 shown in FIG. 1.
[0035] In this regard, the solvent-soluble component extraction
step is performed in the presence of an inert gas, e.g, nitrogen.
The pressure in the extraction vessel 6 is preferably 1.0 to 2.0
MPa, although depending on the temperature in the extraction and
the vapor pressure of the solvent used. In the case where the
pressure in the extraction vessel 6 is lower than the vapor
pressure of the solvent, the solvent is volatilized and is not
confined in the liquid phase, so that extraction cannot be
performed. In order to confine the solvent in the liquid phase, a
pressure higher than the vapor pressure of the solvent is
necessary. On the other hand, if the pressure is too high, the
apparatus cost and the operation cost increase, so that there is no
economy.
[0036] (Method for Separating Solvent and Water)
[0037] As described above, in extraction of the coal component, the
slurry is heated to a temperature of, for example, 300 to 420 DEG
C. Here, under such high temperatures, the coal undergoes a thermal
decomposition reaction, and methane (CH.sub.4), carbon dioxide
(CO.sub.2), water (H.sub.2O), and the like are produced. Also, the
coal serving as a raw material contains water in the first place,
and water is insoluble in the solvent, so that water is separated
from the coal in extraction of the coal component with the
solvent.
[0038] (Solvent-Containing Water Supply Step)
[0039] The solvent-containing water supply step is a step of
supplying the solvent-containing water to the pressure vessel for
solvent separation purposes. The water (H.sub.2O) produced from the
coal through thermal decomposition and the water (H.sub.2O)
separated from the coal in extraction of the coal component are in
the state of a gas containing the solvent (the state of
solvent-containing water vapor) and is supplied (discharged) to the
pressure vessel for solvent separation purposes 11 through the pipe
25. The temperature in the pressure vessel for solvent separation
purposes 11 is specified to be lower than the temperature in the
extraction vessel 6 and, therefore, the water vapor is condensed
into a liquid.
[0040] (Temperature Retention Step)
[0041] The temperature retention step is a step of retaining the
temperature of the solvent-containing water that has been supplied
into the pressure vessel for solvent separation purposes 11 at a
predetermined temperature and is executed in the pressure vessel
for solvent separation purposes 11 shown in FIG. 1. The
solvent-containing water supplied to the pressure vessel for
solvent separation purposes 11 from the extraction vessel 6 is
heated in the pressure vessel for solvent separation purposes 11
with a heater 11a in such a way that the temperature becomes
constant at a temperature at which the difference between the
density of the water and the density of the solvent is large. For
example, the temperature is retained at 100 to 180 DEG C. inclusive
(a predetermined temperature within the range of 100 to 180 DEG
C.). Consequently, the solvent and water are separated by moving of
the water in the liquid form downward to the lower portion of the
pressure vessel for solvent separation purposes 11 and moving of
the solvent upward to the upper portion of the pressure vessel for
solvent separation purposes 11 due to the difference between the
density of the water and the density of the solvent at the
temperature concerned. In order to improve the separability between
the solvent and the water, it is preferable that the
solvent-containing water be allowed to stand for the predetermined
time. Also, it is preferable that the pressure vessel for solvent
separation purposes 11 be heat-insulated by a heat insulating
material to retain the temperature of the solvent-containing water
at a temperature higher than or equal to the predetermined
temperature. In this regard, the term "stand" refers to remain
stationary without agitation and the like.
[0042] The solvent collected in the upper portion of the pressure
vessel for solvent separation purposes 11 is drawn from the upper
portion of the pressure vessel for solvent separation purposes 11,
and the water collected in the lower portion of the pressure vessel
for solvent separation purposes 11 is drawn from the lower portion
of the pressure vessel for solvent separation purposes 11. The
drawn solvent is returned to the solvent tank 2 and is reused. The
drawn water is discarded.
[0043] Also, the temperature retention step is performed preferably
in the presence of an inert gas, e.g., nitrogen. That is, it is
preferable that the inert gas, e.g., nitrogen, be filled in the
pressure vessel for solvent separation purposes 11. The pressure in
the pressure vessel for solvent separation purposes 11 is specified
to be a pressure higher than the saturated vapor pressure of water
in such a way that a water vapor is condensed and the resulting
water keeps the liquid state and is adjusted to be a pressure of,
for example, 0.3 to 2.0 MPa by introduction of a nitrogen gas into
the pressure vessel.
[0044] Also, the solvent-containing water supplied to the pressure
vessel for solvent separation purposes 11 may be agitated with an
agitator or the like and, thereafter, the agitation may be stopped
at the point in time when the temperature becomes constant at the
predetermined temperature, followed by standing.
[0045] Meanwhile, the slurry is heated to a temperature of, for
example, 300 to 420 DEG C. in the extraction vessel 6. The heater
11a is not necessary insofar as the temperature of the
solvent-containing water supplied from the extraction vessel 6 to
the pressure vessel for solvent separation purposes 11 can be
retained at a temperature of, for example, 120 DEG C. or higher for
a predetermined time without heating.
[0046] (Case Where Extraction Vessel 6 is not Provided)
[0047] In some cases, the extraction vessel 6 is not provided, and
a solvent-soluble coal component is extracted in the pipe between
the preheater 5 and the gravity settling vessel 7. For example, the
length of the pipe between the preheater 5 and the gravity settling
vessel 7 is specified to be sufficient for extraction of the coal
component and the coal component is extracted in the pipe between
the preheater 5 and the gravity settling vessel 7. The coal is
directly supplied into the pipe, through which the solvent heated
to a high temperature (for example, 380 DEG C.) is passed, between
the preheater 5 and tbe gravity settling vessel 7. In this case,
the pressure vessel for solvent separation purposes 11 is connected
to the gravity settling vessel 7, the solvent-containing water is
supplied (discharged) from the gravity settling vessel 7 to the
pressure vessel for solvent separation purposes 11, and the
solvent-containing water is separated into the solvent and
water.
[0048] The explanation of the production process of an ashless coal
will be continued.
[0049] (Separation Step)
[0050] The separation step is a step of separating a solution
containing the coal component dissolved in the solvent from the
slurry obtained in the extraction step. Put another way, the
separation step is a step of separating the slurry obtained in the
extraction step into the solution containing the coal component
dissolved in the solvent and a solvent-insoluble component
concentrate (solid content concentrate). This separation step is
executed in the gravity settling vessel 7 shown in FIG. 1. The
slurry obtained in the extraction step is separated into a
supernatant liquid as a solution and a solid content concentrate
due to gravity in the gravity settling vessel 7 (gravity settling
method). The supernatant liquid in the upper portion of the gravity
settling vessel 7 discharged into the solvent separator 9 through
the filter unit 8, as necessary, and in addition, the solid content
concentrate settled into the lower portion of the gravity settling
vessel 7 is discharged into the solvent separator 10.
[0051] The gravity settling method is a method for settling and
separating the solvent-insoluble component through the use of the
gravity by holding the slurry in the vessel. A continuous
separation treatment is possible by supplying the slurry into the
vessel continuously while the supernatant liquid is discharged from
the upper portion and the solid content concentrate is discharged
from the lower portion continuously.
[0052] In order to prevent reprecipitation of the solvent-soluble
component eluted from the coal, it is preferable that the inside of
the gravity settling vessel 7 be heat-insulated or heated and
pressurized. The heating temperature is, for example, 300 to 380
DEG C., and the pressure in the vessel is specified to be, for
example, 1.0 to 3.0 MPa.
[0053] Meanwhile, as for the method for separating the solution
containing the coal component dissolved in the solvent from the
slurry obtained in the extraction step, a filtration method, a
centrifugal separation method, and the like are mentioned besides
the gravity settling method.
[0054] (Ashless Coal Acquisition Step)
[0055] The ashless coal acquisition step is a step of obtaining an
ashless coal by vaporizing and separating the solvent from the
solution (supernatant liquid) separated in the above-described
separation step. This ashless coal acquisition step is executed in
the solvent separator 9 shown in FIG. 1.
[0056] As for the method for separating the solvent from the
solution (supernatant liquid), a common distillation method or
vaporization method can be used and, for example, a flash
distillation method is used. A separated and recovered solvent can
be used repeatedly by circulation to the slurry preparation vessel
3. An ashless coal (HPC) containing substantially no ash (for
example, ash content is 3 percent by weight or less) can be
obtained from the supernatant liquid by separation and recovery of
the solvent. The ashless coal hardly contains ash, contains no
water, and exhibits a calorific value higher than that of the raw
material coal. Furthermore, the plastic property of coal, which is
particularly important quality of a raw material for the coke for
steelmaking, is improved to a great extent, and even when the raw
material coal does not have the plastic property of coal, the
resulting ashless coal (HPC) has good plastic property of coal.
Therefore, the ashless coal can be used as, for example, a blend
coal of the raw material for coke.
[0057] (By-Product Coal Acquisition Step)
[0058] A by-product coal acquisition step is a step of obtaining a
by-product coal by vaporizing and separating the solvent from the
solvent-insoluble component concentrate (solid content concentrate)
separated in the gravity settling vessel 7. This by-product coal
acquisition step is a step of recovering the solvent from the solid
content concentrate through vaporization and separation and is
executed in the solvent separator 10 shown in FIG. 1. In this
regard, the by-product coal acquisition step is not always a
necessary step.
[0059] As for the method for separating the solvent from the solid
content concentrate, a common distillation method or vaporization
method can be used as with the above-described ashless coal
acquisition step. A separated and recovered solvent can be used
repeatedly by circulation to the slurry preparation vessel 3. A
by-product coal (may be referred to as RC, or residual coal), in
which the solvent-insoluble component containing ash and the like
has been concentrated, can be obtained from the solid content
concentrate by separation and recovery of the solvent. The
by-product coal contains ash but no water and has a sufficient
calorific value. The by-product coal does not exhibit the plastic
property of coal. However, an oxygen-containing functional group
has been eliminated, so that in the case of use as a blend coal,
the plastic property of coal of the other coal contained in this
blend coal is not hindered. Therefore, this by-product coal can be
used as part of blend coal of the raw material for coke as with a
common non- or slightly-caking coal or can be used as various fuels
rather than the raw material for coke. In this regard, the
by-product coal may be discarded without being recovered.
EXAMPLES
[0060] Experiments to separate a solvent-containing water into a
solvent and water were performed. FIG. 2 is a diagram illustrating
the outline of a separation test to separate the solvent-containing
water into the solvent and water. An oil component (coal
derivative) refined from a coal containing methylnaphthalene, which
was a bicyclic aromatic, as a primary component was used as the
solvent. Distilled water was used as the water.
[0061] A vertically long autoclave 50 used in the experiment was a
cylindrical pressure vessel having a diameter of 62.3 mm and had a
structure in which a liquid was drawn from the bottom of the
autoclave 50 and a plurality of places at the predetermined heights
from the bottom, as shown in FIG. 2. The liquid was sampled from
six places in total at the heights of 0 mm, 170 mm, 380 mm, 590 mm,
700 mm, and 800 mm, where the height of the bottom of the autoclave
50 was specified to be 0 mm. In this regard, an agitator 50a was
disposed in the inside of the autoclave 50. A nitrogen gas was
filled in the autoclave 50, and the pressure in the autoclave 50
was adjusted to 1.5 MPa.
[0062] A solvent: 1,200 g and water: 1,200 g were put into the
autoclave 50. At room temperature (ambient temperature), the
solvent and the water were in a mixed state and the separability
was very poor. That is, at room temperature (ambient temperature),
there was almost no difference between the density of the water and
the density of the solvent.
[0063] The temperature of the mixed solution composed of the
solvent and the water was raised to the predetermined temperature
while agitation was performed. The temperature conditions were
specified to be 50 DEG C., 90 DEG C., 100 DEG C., 120 DEG C., 150
DEG C., and 200 DEG C. The agitation was stopped when the
temperature of the mixed solution became constant at a
predetermined temperature. After the agitation was stopped,
standing was performed for 30 minutes. Subsequently, the liquid was
taken out of the autoclave 50 into sampling containers 51a to 51f,
and the water concentration of the liquid was measured. The results
are shown in Table 1. FIG. 3 is a graph showing the results shown
in Table 1, the vertical axis indicates the height from the bottom
of the autoclave 50, and the horizontal axis indicates the water
concentration.
TABLE-US-00001 TABLE 1 Water concentration after standing for 30
minutes [wt %] Sampling container No. (height from bottom)
50.degree. C. 90.degree. C. 100.degree. C. 120.degree. C.
150.degree. C. 200.degree. C. 51a -- -- -- -- 0.63 2.16 (800 mm)
51f 40.1 2.69 0.81 2.18 1.94 6.5 (700 mm) 51b 11.7 48.0 0.27 2.81
0.84 29.2 (590 mm) 51c 41.0 70.9 70.2 95.4 72.3 37.3 (380 mm) 51d
54.4 65.1 89.7 91.2 97.6 -- (170 mm) 51e 12.5 33.3 93.0 94.6 98.0
68.8 (0 mm)
[0064] As is clear from Table 1 and FIG. 3, in the case where the
retention temperature was 50 DEG C., the water concentration
fluctuated as the height in the autoclave 50 was changed, and
obvious tendency of the solvent and the water to separate was not
observed visually. In the cases of 90 DEG C. and 200 DEG C., low
values of water concentration were shown in the upper portion of
the autoclave 50, but the values of water concentration at the
bottom were not sufficiently high (the solvent was included), so
that the separation performance was low.
[0065] On the other hand, in the cases where the retention
temperatures were 100 DEG C., 120 DEG C., and 150 DEG C., low
values of water concentration were shown in the upper portion of
the autoclave 50, high values were shown in the bottom, and large
changes were observed within the range of 400 mm to 600 mm from the
bottom. Consequently, it is clear that the separation performance
of the solvent was high in the cases of 100 DEG C., 120 DEG C., and
150 DEG C. In particular, the highest water concentration at the
bottom of 98 percent by weight was shown in the case of 150 DEG C.
Therefore, it was found that the temperature range in which the
retention temperature was 150 DEG C. was the best temperature range
for the solvent separation condition.
[0066] On the basis of this separation test, it was made clear that
the difference between the density of the water and the density of
the solvent changed with the temperature to a great extent
(depended on the temperature to a great extent). The present
invention has taken advantage of this property found here.
[0067] (Operations and Advantages)
[0068] The solvent separation method according to the present
invention includes the temperature retention step of retaining the
temperature of the solvent-containing water that has been supplied
into the pressure vessel for solvent separation purposes at the
predetermined temperature, and the solvent-containing water is
separated into the solvent and water by moving the water in the
liquid form downward and moving the solvent upward in the
above-described pressure vessel for solvent separation purposes
through the use of the difference between the density of the water
and the density of the solvent at the predetermined temperature. In
this regard, the pressure vessel is used in order to confine the
water in the liquid phase in the container. According to the
present invention, the solvent-containing water can be separated
into the solvent and the water readily by retaining the temperature
of the solvent-containing water at the predetermined temperature in
the pressure vessel without using an adsorbent or the like.
Consequently, the adsorbent can be recovered and reused for
extracting the coal component, so that the solvent loss can be
reduced and, in addition, the water disposal cost can be reduced.
In this regard, the solvent-containing water supply step of
supplying the solvent-containing water into the pressure vessel for
solvent separation purposes may be performed continuously or be
performed discontinuously.
[0069] Also, in the above-described temperature retention step, the
separation performance between the solvent and the water can be
improved by retaining the temperature of the solvent-containing
water at the predetermined temperature and, in addition, allowing
the solvent-containing water to stand.
[0070] Also, in the temperature retention step, the temperature of
the solvent-containing water in the pressure vessel for solvent
separation purposes is retained at a temperature of 100 to 180 DEG
C. inclusive and, thereby, the separation performance between the
solvent and the water becomes very good, so that the separation
time can be decreased. There is a merit that the capacity of the
pressure vessel for solvent separation purposes can be reduced.
More preferably, the temperature of the solvent-containing water in
the pressure vessel for solvent separation purposes is retained at
a temperature of 120 to 150 DEG C. inclusive.
[0071] Also, the pressure in the pressure vessel for solvent
separation purposes is specified to be a pressure higher than the
saturated vapor pressure of water and, thereby, the water can be
completely confined in the liquid phase in the pressure vessel, so
that the separation performance between the solvent and the water
is further improved.
[0072] Also, an inert gas is filled in the pressure vessel for
solvent separation purposes and, thereby, explosion of the solvent
can be prevented.
[0073] Also, it is preferable that the solvent-containing water,
which is generated in the above-described extraction step in the
process for producing an ashless coal, be supplied to the pressure
vessel for solvent separation purposes. Water is generated at the
maximum in the extraction step in the process for producing an
ashless coal, and a loss of solvent mixed into water and discharged
to the outside of the system can be reliably reduced by supplying
the solvent-containing water generated in at least this extraction
step to the pressure vessel for solvent separation purposes and
separating the solvent-containing water into the solvent and
water.
[0074] Up to this point, the embodiments according to the present
invention have been explained. However, the present invention is
not limited to the above-described embodiments and can be variously
modified and be executed within the scope of the claims.
REFERENCE SIGNS LIST
[0075] 1: coal hopper
[0076] 2: solvent tank
[0077] 3: slurry preparation vessel
[0078] 4: transfer pump
[0079] 5: preheater
[0080] 6: extraction vessel
[0081] 7: gravity settling vessel
[0082] 8: filter unit
[0083] 9, 10: solvent separator
[0084] 11: pressure vessel for solvent separation purposes
[0085] 100: ashless coal producing facility
* * * * *