U.S. patent application number 15/034044 was filed with the patent office on 2016-09-22 for method for producing ashless coal.
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 | 20160272910 15/034044 |
Document ID | / |
Family ID | 53478369 |
Filed Date | 2016-09-22 |
United States Patent
Application |
20160272910 |
Kind Code |
A1 |
KINOSHITA; Shigeru ; et
al. |
September 22, 2016 |
METHOD FOR PRODUCING ASHLESS COAL
Abstract
Provided is a method for producing ashless coal, said method
comprising a slurry preparation step in which a slurry is prepared
by mixing coal and a solvent, the coal that is included in the
slurry is dewatered, and the temperature of the slurry is
increased. The slurry preparation step comprises a
preparation/dewatering step and a preparation/temperature increase
step. In the preparation/dewatering step, preparation of the slurry
and dewatering of the coal are performed by mixing coal and a
liquid solvent that is circulated during a circulation step. In the
preparation/temperature increase step, the slurry is prepared and
the temperature of the slurry is increased by mixing the slurry
with solvent vapor that is circulated during the circulation
step.
Inventors: |
KINOSHITA; Shigeru; (Hyogo,
JP) ; OKUYAMA; Noriyuki; (Hyogo, JP) ;
YOSHIDA; Takuya; (Hyogo, JP) ; SAKAI; Koji;
(Hyogo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.) |
Kobe-shi, Hyogo |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA KOBE SEIKO SHO
(KOBE STEEL, LTD.)
Kobe-shi, Hyogo
JP
|
Family ID: |
53478369 |
Appl. No.: |
15/034044 |
Filed: |
December 9, 2014 |
PCT Filed: |
December 9, 2014 |
PCT NO: |
PCT/JP2014/082579 |
371 Date: |
May 3, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10L 2290/22 20130101;
C10L 2290/24 20130101; C10L 9/00 20130101; C10L 2290/06 20130101;
C10L 5/04 20130101; C10L 2290/08 20130101; C10L 2290/544 20130101;
C10L 2290/10 20130101 |
International
Class: |
C10L 5/04 20060101
C10L005/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 25, 2013 |
JP |
2013-267439 |
Claims
1. A method for producing ashless coal, the method comprising:
mixing coal and a solvent to prepare a slurry, and performing a
dehydration of the coal contained in the slurry and a temperature
increase of the slurry; heating the slurry to extract a
solvent-soluble component of the coal, to obtain an extracted
slurry; separating the extracted slurry into a solution containing
the solvent-soluble component of the coal and a solid-content
concentrated liquid having concentrated therein a solvent-insoluble
component of the coal; evaporating and separating the solvent from
the solution to obtain ashless coal; and circulating the solvent to
a slurry preparation, wherein the slurry preparation comprises:
mixing liquid solvent of the circulating step with the coal to
prepare the slurry and dehydrate the coal; and mixing vapor solvent
of the circulating step with the slurry to increase the temperature
increase of the slurry.
2. The method according to claim 1, wherein, during the mixing of
the vapor solvent with the slurry, a concentration of the slurry is
adjusted to be an inlet concentration suitable to extract the
solvent-soluble component of the coal.
3. The method according to claim 1, wherein, during the mixing of
the vapor solvent with the slurry, a temperature of the slurry is
increased to an inlet temperature suitable for mixing the coal with
the solvent.
4. The method according to claim 1, wherein the vapor solvent of
the circulating step and the slurry are mixed by a venturi
scrubber.
5. The method according to claim 1, further comprising: feeding
coal, to be mixed with the solvent to prepare the slurry, by way of
a coal feed line; and flowing a purge gas into the coal feed line
to thereby discharge a vapor produced in the mixing step from the
coal feed line.
6. The method according to claim 2, wherein, during the mixing of
the vapor solvent with the slurry, a temperature of the slurry is
increased to an inlet temperature suitable for mixing the coal with
the solvent.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for producing
ashless coal.
BACKGROUND ART
[0002] Conventionally, there are methods for producing ashless coal
(for example, Patent Document 1). A production method of ashless
coal described in Patent Document 1 is as follows (see, claim 1 of
the document): "A method for producing ashless coal, including a
slurry preparation step of mixing a solvent and coal to prepare a
slurry, an extraction step of heating the slurry obtained in the
slurry preparation step . . . to extract a coal component soluble
in the solvent, a separation step of separating a coal component
insoluble in the solvent from the slurry obtained in the extraction
step, a step of recovering the solvent from the slurry separated in
the separation step, the slurry containing a coal component
insoluble in the solvent to obtain ashless coal, and a step of
circulating the recovered solvent to the slurry preparation
step".
PRIOR ART DOCUMENT
Patent Document
[0003] Patent Document 1: Japanese Patent No. 4,045,229
SUMMARY OF THE INVENTION
Problems that the Invention is to Solve
[0004] The production method of ashless coal described in Patent
Document 1 includes, as described above, "a step of recovering the
solvent from the slurry separated in the separation step, the
slurry containing a coal component insoluble in the solvent to
obtain ashless coal" (this step is referred to as "ashless coal
acquisition step"). The solvent recovered in the ashless coal
acquisition step is at a high temperature (e.g., 270.degree. C.).
On the other hand, the production method of ashless coal described
in Patent Document 1 includes "an extraction step of heating the
slurry obtained in the slurry preparation step . . . to extract a
coal component soluble in the solvent". The slurry fed to the
extraction step is heated (preheated) before the extraction step.
Therefore, it can be considered that the heat energy possessed by
the solvent (high temperature-side fluid) recovered in the ashless
coal acquisition step could be used as a heat source for the slurry
(low temperature-side fluid) fed to the extraction step. In
addition, it can be considered that heating of the low
temperature-side fluid by the high temperature-side fluid could be
performed in a heat exchanger.
[0005] However, the heat exchange by a heat exchanger requires
providing a temperature difference between the heat exchanger inlet
temperature of the high temperature-side fluid and the heat
exchanger outlet temperature of the low temperature-side fluid.
Therefore, in this heat exchange, part of the heat energy of the
solvent (high temperature-side fluid) recovered in the ashless coal
acquisition step is not transferred to the slurry (low
temperature-side fluid) fed to the extraction step.
[0006] An object of the present invention is to provide a
production method of ashless coal, where a heat exchange between
coal and solvent and a heat exchange between slurry and solvent are
efficiently performed and the heat energy generated in the
production process of ashless coal can be thereby effectively
utilized.
Means for Solving the Problems
[0007] The method for producing ashless coal of the present
invention includes a slurry preparation step of mixing coal and a
solvent to prepare a slurry, and performing a dehydration of the
coal contained in the slurry and a temperature increase of the
slurry, an extraction step of heating the slurry obtained in the
slurry preparation step to extract a solvent-soluble component of
the coal, a separation step of separating the slurry obtained in
the extraction step into a solution containing the solvent-soluble
component of the coal and a solid-content concentrated liquid
having concentrated therein a solvent-insoluble component of the
coal, an ashless coal acquisition step of evaporating and
separating the solvent from the solution separated in the
separation step to obtain ashless coal, and a circulation step of
circulating the solvent evaporated and separated in the ashless
coal acquisition step. The slurry preparation step includes a
preparation and dehydration step of mixing a solvent liquid
circulated in the circulation step and the coal to thereby perform
the preparation of the slurry and the dehydration of the coal, and
a preparation and temperature increase step of mixing a solvent
vapor circulated in the circulation step and the slurry to thereby
perform the preparation and the temperature increase of the
slurry.
Advantage of the Invention
[0008] Due to the configuration above, the heat exchange between
coal and solvent and the heat exchange between slurry and solvent
are efficiently performed, and the heat energy generated in the
production process of ashless coal can be thereby effectively
utilized.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 A schematic view of the ashless coal production
system 1.
[0010] FIG. 2 A schematic view of the ashless coal production
system 101 of Comparative Example.
MODE FOR CARRYING OUT THE INVENTION
[0011] The production method of ashless coal and the ashless coal
production system 1 for performing the production method of ashless
coal are described by referring to FIG. 1.
[0012] The ashless coal production system 1 is an apparatus for
producing ashless coal (HPC; Hyper-coal) by removing ash from raw
material coal (sometimes simply referred to as "coal"). The ashless
coal production system 1 is equipped with coal/slurry processing
devices 11 to 37, circulation paths 41 to 46, and
on-circulation-path devices 51 to 91.
[0013] The coal/slurry processing devices 11 to 37 are devices for
processing coal and a slurry (described later). The coal/slurry
processing devices 11 to 37 have a coal feed line 11 and a vapor
discharge unit 13. Furthermore, the coal/slurry processing devices
11 to 37 have a slurry preparation device 20, a preheater 31, an
extraction tank 33, a separation unit 35, and a solvent recovery
unit 37, in the order from the upstream side in the production
process of ashless coal.
[0014] The coal feed line 11 feeds coal to the slurry preparation
device 20 (coal feeding step). The coal feed line 11 feeds coal
from a feeder, etc. (not shown) to a preparation and dehydration
tank 21 (described later) of the slurry preparation device 20. This
coal is, for example, bituminous coal or low-grade coal (brown coal
or subbituminous coal). The bituminous coal is higher in the
extraction rate (the proportion of soluble coal component extracted
with a solvent) than the low-grade coal. The low-grade coal is more
inexpensive than bituminous coal.
[0015] In the vapor discharge unit 13, a purge gas is flowed into
the coal feed line 11 to thereby discharge the vapor produced in a
preparation and dehydration tank 21 (described later) from the coal
feed line 11 (vapor discharging step). The purge gas is a gas being
a gaseous state in the coal feed line 11 and is, for example,
nitrogen (purge nitrogen). The vapor discharge unit 13 is provided
to reduce the problem of clogging of the coal feed line 11. The
"problem of clogging" above may be caused as follows. Vapor is
generated as a result of heating and dehydration of coal in a
preparation and dehydration tank 21 (described later). The majority
of the vapor is water vapor, and part of the vapor is a solvent
vapor (solvent in gaseous state). When this vapor enters the coal
feed line 11, the vapor is cooled and forms a condensate, and the
condensate adheres to the inner surface of the coal feed line 11.
When coal adheres to the condensate, the coal clogs the coal feed
line 11 (the passage is narrowed or the passage is completely
clogged). In this way, the "problem of clogging" may be caused. The
vapor discharge unit 13 has a valve 13a and a purge gas feed unit
13b.
[0016] The valve 13a is disposed on the coal feed line 11. The flow
of substances (coal, vapor, and purge gas) passing through the coal
feed line 11 is controlled by the opening/closing of the valve 13a.
A plurality (for example, two) of valves 13a are preferably
disposed in series on the coal feed line 11. In the case of
disposing a plurality of valves 13a on the coal feed line 11, the
vapor can be more effectively prevented from entering the coal feed
line 11, compared with a case where only one is disposed. The valve
13a is, for example, a rotary valve.
[0017] The purge gas feed unit 13b feeds a purge gas into the coal
feed line 11 (purge gas feeding step). In the case where two valves
13a are disposed in series on the coal feed line 11, the purge gas
feed unit 13b feeds a purge gas between two valves 13a.
[0018] In the slurry preparation device 20, coal and a solvent are
mixed to prepare a slurry (coal-solvent slurry) and the dehydration
and temperature increase of slurry are performed (slurry
preparation step).
[0019] The solvent fed to the slurry preparation device 20 is one
which dissolves coal. The solvent is preferably one ensuring that
the proportion (extraction rate) of soluble coal component
extracted in the extraction tank 33 is high. In view of extraction
rate, the solvent is preferably stable even in a heated state and
preferably has a high dissolving power for coal (an excellent
affinity for coal). This solvent is preferably one providing a high
solvent recovery rate in a solvent recovery unit 37. In view of the
solvent recovery rate, it is preferred that the solvent is readily
recoverable by distillation or other methods. In view of pressure
reduction in the extraction tank 33 and the separation unit 35 and
the extraction rate in the extraction tank 33, etc., the boiling
point of the solvent is, for example, preferably from 180 to
300.degree. C. and more preferably from 230 to 280.degree. C. The
solvent is, for example, a coal derivative. The solvent is obtained
by mainly refining a carbonization product of coal. The solvent is,
for example, a solvent containing an aromatic compound (aromatic
solvent). The main component of the solvent is a bicyclic aromatic.
The bicyclic aromatic includes, for example, naphthalene,
methylnaphthalene, dimethylnaphthalene, and trimethylnaphthalene.
Other components of the solvent include, for example, naphthalenes,
anthracenes and fluorenes, each having an aliphatic side chain, and
alkylbenzenes formed by adding biphenyl or a long-chain aliphatic
side chain thereto. Specifically, the solvent is, for example, a
methylnaphthalene oil or a naphthalene oil. The methylnaphthalene
oil or naphthalene oil is a distillation oil of a byproduct oil in
carbonization of coal for producing coke. The slurry preparation
device 20 has a preparation and dehydration tank 21 and a
preparation and temperature increase device 23.
[0020] In the preparation and dehydration tank 21, a solvent liquid
(solvent in a liquid state) and coal are mixed to thereby perform
the preparation of slurry and the dehydration of coal (preparation
and dehydration step). The solvent liquid fed to the preparation
and dehydration tank 21 is a solvent liquid circulated through part
of the circulation paths 41 to 46. The coal fed to the preparation
and dehydration tank 21 is fed by way of the coal feed line 11. The
mixing of solvent liquid and coal in the preparation and
dehydration tank 21 is performed, for example, by charging coal
into the solvent liquid in the preparation and dehydration tank 21.
A slurry is prepared by the mixing of solvent liquid and coal in
the preparation and dehydration tank 21. The S/C (Slurry/Coal; a
ratio of the mass of slurry to the mass of coal in a dry state) of
the slurry prepared in the preparation and dehydration tank 21 is,
for example, about 2.0.
[0021] In the preparation and dehydration tank 21, the dehydration
of coal is performed as follows. In the preparation and dehydration
tank 21, the solvent liquid is brought into direct contact with
coal by the mixing of solvent liquid and coal. In the preparation
and dehydration tank 21, due to the direct contact above, heat
exchange is directly performed between the solvent liquid and coal.
By this heat exchange in the preparation and dehydration tank 21,
the temperature of the coal is increased and the water (water
contained by coal) in the coal is evaporated. The temperature of
the solvent liquid fed to the preparation and dehydration tank 21
is equal to or more than the temperature necessary to perform the
dehydration and is less than the boiling point of the solvent. The
temperature of the solvent liquid fed to the preparation and
dehydration tank 21 is, for example, 230.degree. C. or more and
preferably 235.degree. C. or more, and, for example, 240.degree. C.
or less. In the example illustrated in FIG. 1, the temperature of
the solvent liquid fed to the preparation and dehydration tank 21
is 237.degree. C. (hereinafter, refer to FIG. 1 as to specific
examples of the temperature).
[0022] In the preparation and temperature increase device 23, a
solvent vapor and the slurry are mixed to thereby perform the
preparation and temperature increase of slurry (preparation and
temperature increase step). In the preparation and temperature
increase device 23, the concentration of the slurry is adjusted to
be an inlet concentration of the extraction tank 33. The inlet
concentration of the extraction tank 33 is set in advance. A device
for adjusting the slurry concentration need not be provided between
the preparation and temperature increase device 23 and the
extraction tank 33, and the ashless coal production system 1 does
not have such a device. The S/C of the slurry prepared in the
preparation and temperature increase device 23 is, for example,
about 4.0. In the preparation and temperature increase device 23,
the temperature of the slurry is increased to an inlet temperature
of a device (referred to as "post-slurry-preparation device") to
which the slurry is fed following the slurry preparation device 20.
The inlet temperature of the "post-slurry-preparation device" is
set in advance. Specifically, the "post-slurry-preparation device"
is the preheater 31 and, in the case of not providing a preheater
31, it is the extraction tank 33. A device for adjusting the slurry
temperature need not be provided between the preparation and
temperature increase device 23 and the "post-slurry-preparation
device", and the ashless coal production system 1 does not have
such a device. The preparation and temperature increase device 23
has a venturi scrubber 23a and a preparation and temperature
increase tank 23b.
[0023] The venturi scrubber 23a mixes a solvent vapor and the
slurry (first preparation and temperature increase step). The
solvent vapor fed to the venturi scrubber 23a is the solvent vapor
circulated through part of the circulation paths 41 to 46 (details
are described later). The slurry fed to the venturi scrubber 23a is
fed from the preparation and dehydration tank 21. The slurry fed to
the venturi scrubber 23a is the slurry after preparation and
dehydration thereof have been performed in the preparation and
dehydration tank 21. In the venturi scrubber 23a, the slurry is
brought into direct contact with the solvent vapor by the mixing of
slurry and solvent vapor. In the venturi scrubber 23a, due to the
direct contact above, heat exchange is directly performed between
the solvent vapor and the slurry. In the venturi scrubber 23a, the
slurry is heated by utilizing latent heat of the solvent vapor (by
utilizing heat generated at the time of condensation of the solvent
vapor). In the case where dehydration of coal in the preparation
and dehydration tank 21 is not completed, the venturi scrubber 23a
heats the slurry to thereby perform the dehydration of coal in the
slurry. The venturi scrubber 23a forms the slurry into fine
particle state and mixes the fine particulate slurry and the
solvent vapor. In the venturi scrubber 23a, the fine particulate
slurry and the solvent vapor are mixed by increasing the flow rate
of the fine particulate slurry and the solvent vapor and thereby
producing a shear force on the fine particulate slurry and the
solvent vapor. Here, in place of or in addition to the venturi
scrubber 23a, a unit (first preparation and temperature increase
unit) for mixing the solvent vapor and the slurry, other than a
venturi scrubber, may also be used. The "unit other than a venturi
scrubber" includes, for example, a static mixer. In the static
mixer, the fine particulate slurry and the solvent vapor are
stirred and mixed by an element (a member of twisted plate shape or
a member of screw shape) disposed inside a tube.
[0024] In the preparation and temperature increase tank 23b, the
mixture mixed in the venturi scrubber 23a is further mixed (second
preparation and temperature increase step). In the preparation and
temperature increase tank 23b, due to the mixing above, heat is
further exchanged between the slurry and the solvent. The interior
of the preparation and temperature increase tank 23b is pressurized
so that the vaporization of solvent (solvent vapor loss) can be
suppressed, and it is pressurized, for example, to 50 kPaG.
[0025] In the preheater 31, the slurry prepared in the preparation
and temperature increase device 23 (slurry preparation device 20)
is previously heated before being fed to the extraction tank 33
(preheating step). The preheater 31 may not be used.
[0026] In the extraction tank 33, the slurry obtained in the slurry
preparation device 20 is heated to extract a coal component soluble
in the solvent (solvent-soluble component) (extraction step). In
the extraction tank 33, an organic component in the coal is
extracted. Details of this extraction are as follows. The slurry
fed to the extraction tank 33 is heated and kept at a predetermined
temperature (described later) under stirring by a stirrer provided
in the extraction tank 33. In this manner, a solvent-soluble
component is extracted from the slurry. However, not only a
solvent-soluble component but also a component insoluble in the
solvent (solvent-insoluble component) (for example, ash) are
contained in the extract.
[0027] The slurry heating temperature in the extraction tank 33 is
a temperature allowing the solvent-soluble component to be
dissolved in the solvent. Specifically, the slurry heating
temperature is, for example, 300.degree. C. or more, and preferably
360.degree. C. or more. The slurry heating temperature is, for
example, 420.degree. C. or less, and preferably 400.degree. C. or
less. If the slurry heating temperature is less than 300.degree.
C., it is not enough to weaken the bond between coal molecules and
therefore, the amount of the solvent-soluble component dissolved in
the solvent decreases. If the slurry heating temperature exceeds
420.degree. C., the coal undergoes a vigorous pyrolysis reaction
and recombination of produced pyrolysis radicals occurs, and as a
result, the extraction rate of the solvent-soluble component
decreases.
[0028] The extraction conducted in the extraction tank 33 is
preferably performed in the presence of an inert gas (preferably,
for example, nitrogen that is inexpensive). In order to perform
this extraction, the solvent must be confined to a liquid phase
(the solvent must be prevented from volatilizing). For confining
the solvent to the liquid phase, the pressure (pressure applied to
the solvent and the slurry, operation pressure) in the extraction
tank 33 needs to be higher than the vapor pressure of the solvent.
The pressure in the extraction tank 33 is preferably from 1.0 to
2.0 MPa, though this may vary depending on the temperature during
extraction or the vapor pressure of the solvent used.
[0029] In the separation unit 35, the slurry obtained in the
extraction tank 33 is separated into a solution (solution part,
supernatant, overflow) containing a solvent-soluble component of
the coal and a solid-content concentrated liquid (underflow) having
concentrated therein a solvent-insoluble component of the coal
(separation step). The method for this separation is, for example,
a gravitational settling method, a filtration method or a
centrifugal separation method. The gravitational settling method is
a method of holding the slurry in the tank and settling the
solvent-insoluble component by utilizing gravity, thereby achieving
separation into a solution and a solid-content concentrated liquid.
In the following, a case where separation in the separation unit 35
is performed by the gravitational settling method is described. The
interior of the separation unit 35 is kept warm (or heated) and
pressurized. This warm keeping (or heating) and pressurization are
performed so as to prevent reprecipitation of the solvent-soluble
component eluted from the coal. The temperature in the separation
unit 35 is, for example, from 300 to 380.degree. C. The pressure in
the separation unit 35 is, for example, from 1.0 to 3.0 MPa. The
separation unit 35 is, for example, a two-stage type (the number of
gravitational settling tanks is 2). The two-stage type separation
unit 35 has a first gravitational settling tank 35a and a second
gravitational settling tank 35b. The separation unit 35 may be a
one-stage type (the number of gravitational settling tanks is 1).
Here, it is ideal that the separation unit 35 completely separates
a supernatant and a solid-content concentrated liquid, but a solid
content (coal component insoluble in the solvent) may get mixed in
with part of the supernatant, or the supernatant may get mixed in
with part of the solid-content concentrated liquid.
[0030] In the solvent recovery unit 37, the solvent is recovered
from the solution separated in the separation unit 35. The solvent
recovery unit 37 is a unit for obtaining ashless coal or byproduct
coal (described later) from the solution separated in the
separation unit 35. The solvent recovery unit 37 has a first
solvent recovery unit 37a and a second solvent recovery unit
37b.
[0031] The first solvent recovery unit 37a is a unit for obtaining
ashless coal (HPC) (a unit for performing the ashless coal
acquisition step) by evaporating and separating the solvent from
the solution separated in the separation unit 35. The ashless coal
is coal containing absolutely no water and containing substantially
no ash. The amount of ash contained in the ashless coal is 5 wt %
or less and preferably 3 wt % or less. The ashless coal has a
higher heating value, and better ignitability and burnout
performance than those of a raw material coal and therefore, is
used, for example, as a high-efficient fuel for a boiler, etc. The
ashless coal is higher in the fluidity (plastic properties) than a
raw material coal and is used, for example, as a raw material or
part of a raw material (blended coal) of coke for iron making.
[0032] The method for the evaporation and separation of solvent
performed in the first solvent recovery unit 37a includes, for
example, a distillation method and an evaporation method. The
evaporation method includes, for example, a spray dry method. The
distillation method includes, for example, a flash distillation
method and a thin-film distillation method. The first solvent
recovery unit 37a is, for example, a flash tank (flasher) for
performing a flash distillation method. Alternatively, the first
solvent recovery unit 37a is, for example, a thin-film distillation
tank for performing a thin-film distillation method. In addition,
the first solvent recovery unit 37a is, for example, a unit having
a flash tank and a thin-film distillation tank (disposed, for
example, on the downstream side of the flash tank).
(Flash Method)
[0033] The evaporation and separation of solvent by the flash
method is performed as follows. The pressure in the flash tank is
adjusted to a low pressure (for example, 70 kPaG) compared with
that in the separation unit 35. Then, the solution separated in the
separation unit 35 spouts into the flash tank. As a result, the
solvent in the solution is evaporated and separated from the
solution.
(Thin-Film Distillation Method)
[0034] The evaporation and separation of solvent by the thin-film
distillation method is performed as follows. The solution separated
in the separation unit 35 is introduced into the thin-film
distillation tank. Thereafter, a scraper (also called "wiper")
housed in the thin-film distillation tank forms a thin film of the
distillation object (the solution separated in the distillation
unit 35) on the inner wall of the thin-film distillation tank,
whereby continuous distillation is performed. The pressure in the
thin-film distillation tank is, for example, 0.1 MPaG. In order to
allow for appropriate evaporation of the solvent in the thin-film
distillation tank, the wall of the thin-film distillation tank is
heated. The heating of wall of the thin-film distillation tank is
performed, for example, by hot oil or performed, for example, by an
electric heater. In the case of performing the heating of wall of
the thin-film distillation tank by hot oil, a jacket (coating) is
provided on the inner and outer sides (or, for example, on either
one of the inner side and the outer side) of wall of the thin-film
distillation tank. Hot oil is flowed through the jacket. As a
result, the wall of the thin-film distillation tank is heated. The
heating of wall of the thin-film distillation tank is required, for
example, in the following case. The first solvent recovery unit 37a
sometimes has a flash distillation tank and a thin-film
distillation tank on the downstream side of the flash distillation
tank. In this case, the solution temperature drops due to
evaporation in the flash tank. Therefore, the heating of wall of
the thin-film distillation tank is performed so that the solvent
can be appropriately evaporated in the thin-film distillation
tank.
[0035] The second solvent recovery unit 37b is a unit for obtaining
byproduct coal (RC: Residue coal) (also called residual coal) (a
unit for performing the byproduct coal acquisition step) by
evaporating and separating the solvent from the solid-content
concentrated liquid separated in the separation unit 35. The
byproduct coal is coal having concentrated therein a
solvent-insoluble component (for example, ash) and is used, for
example, as part of the blended coal that is a raw material of
coke. The method for the evaporation and separation of solvent in
the second solvent recovery unit 37b includes a distillation method
and an evaporation method, similarly to the method for the
evaporation and separation of solvent in the first solvent recovery
unit 37a. The second solvent recovery unit 37b may not be
provided.
[0036] In the circulation paths 41 to 46, the solvent evaporated
and separated in the solvent recovery unit 37, etc. is circulated
(circulation step). The circulation paths 41 to 46 are flow
channels (pipings) for recycling the solvent. The circulation paths
41 to 46 include a first circulation path 41, a second circulation
path 42, a third circulation path 43, a fourth circulation path 44,
a fifth circulation path 45, and a sixth circulation path 46.
[0037] In the first circulation path 41, the solvent evaporated and
separated in the first solvent recovery unit 37a is circulated to
the preparation and dehydration tank 21 (first circulation step).
The first circulation path 41 introduces the solvent taken out from
the top of the first solvent recovery unit 37a into the preparation
and dehydration tank 21.
[0038] In the second circulation path 42, the solvent evaporated
and separated in the first solvent recovery unit 37a is circulated
to the preparation and temperature increase device 23 (second
circulation step). In the second circulation path 42, the solvent
evaporated and separated in the first solvent recovery unit 37a is
circulated to the venturi scrubber 23a. In the second circulation
path 42, the solvent evaporated and separated in the first solvent
recovery unit 37a is directly (without heat recovery or temperature
increase) circulated to the venturi scrubber 23a. The sum of the
piping pressure drop (for example, 20 kPaG) in the second
circulation path 42 and the operation pressure (for example, 50
kPaG) in the venturi scrubber 23a is equal to the operation
pressure (for example, 70 kPaG) in the first solvent recovery unit
37a. Therefore, the operation pressure in the first solvent
recovery unit 37a is set based on the sum of the operation pressure
in the venturi scrubber 23a and the piping pressure drop in the
second circulation path 42.
[0039] In the third circulation path 43, the solvent evaporated and
separated in the first solvent recovery unit 37a is circulated to
the separation unit 35 (third circulation step). In the third
circulation path 43, the solvent evaporated and separated in the
first solvent recovery unit 37a is circulated to the second
gravitational settling tank 35b. By feeding the solvent (a
high-temperature solvent concentrate) to the second gravitational
settling tank 35b through the third circulation path 43, the supply
of solvent necessary for the second gravitational settling tank 35b
is provided.
[0040] In the fourth circulation path 44, the solvent evaporated
and separated in the second solvent recovery unit 37b is circulated
to the preparation and dehydration tank 21 (fourth circulation
step). The fourth circulation path 44 introduces the solvent taken
out from the top of the second solvent recovery unit 37b into the
preparation and dehydration tank 21. In the vapor introduced into
the fourth circulation path 44 from the second solvent recovery
unit 37b, not only the solvent but also nitrogen are contained.
[0041] In the fifth circulation path 45, the vapor generated in the
slurry preparation device 20 is circulated to the preparation and
dehydration tank 21 (fifth circulation step). The vapor generated
in the slurry preparation device 20 contains the solvent and water
and contains water in a larger ratio than the solvent. In the fifth
circulation path 45, vapor generated in the preparation and
dehydration tank 21 is circulated to the preparation and
dehydration tank 21. In the firth circulation path 45, vapor
generated in the preparation and temperature increase tank 23b is
circulated to the preparation and dehydration tank 21. The portion
"A" depicted on the upper side of the slurry preparation device 20
in FIG. 1 is connected to the portion "A" depicted on the left side
of a cooler 81 in the same figure.
[0042] In the sixth circulation path 46, the solvent vapor
generated in the extraction tank 33 is circulated to the
preparation and dehydration tank 21 (sixth circulation step).
[0043] The on-circulation-path devices 51 to 91 are devices
disposed on the circulation paths 41 to 46 (excluding the second
circulation path 42). The on-circulation-path devices 51 to 91
include the following devices. The device disposed on the first
circulation path 41 includes a recovered solvent tank 51. The
device disposed on the third circulation path 43 includes, in the
order from the upstream side, an exhaust heat recovery boiler 61, a
heat exchanger 63 and a preheater 65. The device disposed on the
fourth circulation path 44 includes, in the order from the upstream
side, a bag filter 71, an exhaust heat recovery boiler 73, a cooler
75, a heat exchanger 77, and a recovered solvent tank 51. The
device disposed on the fifth circulation path 45 includes, in the
order from the upstream side, a cooler 81, an oil/water separation
tank 83, a heat exchanger 77, and a recovered solvent tank 51. The
device disposed on the sixth circulation path 46 includes, in the
order from the upstream side, an oil heater 91, a heat exchanger
63, a heat exchanger 77, an oil/water separation tank 83, a heat
exchanger 77, and a recovered solvent tank 51.
[0044] In the recovered solvent tank 51, a solvent liquid for
feeding to the preparation and dehydration tank 21 is prepared
(solvent liquid preparation step). The solvent fed to the recovered
solvent tank 51 is the solvent (solvent vapor) passing through the
first circulation path 41 and is more specifically the solvent
vapor evaporated and separated in the first solvent recovery unit
37a. The solvent vapor evaporated and separated in the first
solvent recovery unit 37a is directly (without heat recovery or
temperature increase) fed to the recovered solvent tank 51. In
addition, the solvent fed to the recovered solvent tank 51 is the
solvent flowing through the fourth circulation path 44, the fifth
circulation path 45 and the sixth circulation path 46 and is more
specifically the solution liquid after being subjected to heat
exchange in the heat exchanger 77 (described later).
[0045] In the exhaust heat recovery boiler 61, heat of the solvent
flowing through the third circulation path 43 is recovered (third
circulation path exhaust heat recovery step). The solvent fed to
the exhaust heat recovery boiler 61 is the solvent (solvent vapor)
passing through the third circulation path 43 and is more
specifically the solvent vapor evaporated and separated in the
first solvent recovery unit 37a. The solvent vapor evaporated and
separated in the first solvent recovery unit 37a is directly fed to
the exhaust heat recovery boiler 61. In the exhaust heat recovery
boiler 61, saturated vapor (steam) is produced by utilizing the
heat energy of the solvent fed to the exhaust heat recovery boiler
61. In the exhaust heat recovery boiler 61, the temperature of the
solvent vapor fed to the exhaust heat recovery boiler 61 is lowered
to condensate the solvent vapor. In the exhaust heat recovery
boiler 61, saturated vapor of, for example, 2.2 MPaG is produced,
for example, at 19.30 t/h. The exhaust heat recovery boiler 61 may
be replaced by an exhaust heat recovery unit other than a boiler.
As to the replacement with an exhaust heat recovery unit other than
a boiler, the same applies to the later-described exhaust heat
recovery boiler 73, etc. The exhaust heat recovery unit other than
a boiler includes, for example, a unit for heating hot oil (see,
the oil heater 91 described later).
[0046] In the heat exchanger 63, the temperature of the solvent
flowing through the third circulation path 43 is increased (third
circulation path temperature increase step). The low
temperature-side fluid (fluid to be temperature-increased) fed to
the heat exchanger 63 is the solvent flowing through the third
circulation path 43 and is more specifically the solvent liquid
after being subjected to heat exchange in the exhaust heat recovery
boiler 61. The high temperature-side fluid (fluid to increase
temperature) fed to the heat exchanger 63 is the solvent flowing
through the sixth circulation path 46 and is more specifically the
solvent (solvent vapor) after being subjected to heat recovery in
the oil heater 91 (described later).
[0047] In the preheater 65, the solvent flowing through the third
circulation path 43 is previously heated before being fed to the
separation unit 35 (third circulation path preheating step). The
solvent fed to the preheater 65 is the solvent (solvent liquid)
after being subjected to heat exchange in the heat exchanger 63. In
the preheater 65, the temperature of the solvent is increased to a
required temperature in the separation unit 35 (second
gravitational settling tank 35b).
[0048] In the bag filter 71, the solvent, etc. flowing through the
fourth circulation path 44 is filtered (filtration step). The
solvent fed to the bag filter 71 is the solvent (solvent vapor)
evaporated and separated in the second solvent recovery unit
37b.
[0049] In the exhaust heat recovery boiler 73, heat of the solvent
flowing through the fourth circulation path 44 is recovered (fourth
circulation path exhaust heat recovery step). The solvent fed to
the exhaust heat recovery boiler 73 is the solvent (solvent vapor)
having filtered in the bag filter 71. In the exhaust heat recovery
boiler 73, saturated vapor is produced by utilizing the heat energy
of the solvent. In the exhaust heat recovery boiler 73, saturated
vapor of, for example, 0.70 MPaG is produced, for example, at 6.03
t/h.
[0050] In the cooler 75, the solvent flowing through the fourth
circulation path 44 is cooled (fourth circulation path cooling
step). In the cooler 75, the solvent is cooled by using, for
example, cooling water. The solvent fed to the cooler 75 is the
solvent (solvent vapor) having heat-recovered in the exhaust heat
recovery boiler 73. In the cooler 75, the solvent vapor fed to the
cooler 75 is cooled and condensed.
[0051] In the heat exchanger 77, the temperature of the solvent
flowing through the fourth circulation path 44 is increased (fourth
circulation path temperature increase step). In the heat exchanger
77, the temperature of the solvent flowing through the fifth
circulation path 45 is increased (fifth circulation path
temperature increase step). In the heat exchanger 77, the
temperature of the solvent flowing through the sixth circulation
path 46 is increased (sixth circulation path temperature increase
step). The low temperature-side fluid fed to the heat exchanger 77
is the solvent flowing through the fourth circulation path 44 and
is more specifically the solvent (solvent liquid) after being
subjected to cooling in the cooler 75. The low temperature-side
fluid fed to the heat exchanger 77 is the solvent flowing through
the fifth circulation path 45 and sixth circulation path 46 and is
more specifically the solvent (solvent liquid) after being
subjected to oil/water separation in an oil/water separation tank
83 (described later). The high temperature-side fluid fed to the
heat exchanger 77 is the solvent flowing through the sixth
circulation path 46 and is more specifically the solvent (solvent
vapor) after being subjected to heat exchange in the heat exchanger
63 but before oil/water separation in an oil/water separation tank
83.
[0052] In the cooler 81, the vapor (as described above, the vapor
containing the solvent and water) flowing through the fifth
circulation path 45 is cooled (fifth circulation path cooling
step). In the cooler 81, the vapor is cooled by using, for example,
cooling water. In the cooler 81, the vapor is cooled and
condensed.
[0053] In the oil/water separation tank 83, the solvent (oil) and
water are separated from the fluid flowing through the fifth
circulation path 45, etc. (oil/water separation step). The fluid
fed to the oil/water separation tank 83 is the fluid flowing
through the fifth circulation path 45 and is more specifically the
liquid after being subjected to cooling in the cooler 81. The fluid
fed to the oil/water separation tank 83 is the fluid flowing
through the sixth circulation path 46 and is more specifically the
solvent (solvent liquid) after heat exchange in the heat exchanger
77. The water separated in the oil/water separation tank 83 is
discharged as waste water (WW) from the oil/water separation tank
83.
[0054] In the oil heater 91, the temperature of hot oil is
increased by utilizing the heat energy of the solvent (solvent
vapor) flowing through the sixth circulation path 46 (oil
temperature increase step). The solvent fed to the oil heater 91 is
the solvent vapor generated in the extraction tank 33. The hot oil
temperature-increased in the oil heater 91 is utilized as a heat
source in other steps. The hot oil is utilized, for example, as a
heat source in the solvent recovery unit 37. The hot oil is used,
for example, for the heating of wall of the thin-film distillation
tank of the solvent recovery unit 37 as described above. The oil
heater 91 may be replaced by an exhaust heat recovery unit (e.g.,
boiler) other than a unit for increasing the temperature of hot
oil.
(Ashless Coal Production System 101 of Comparative Example)
[0055] In order to perform a comparison in the later-described
"Comparison of Utility Amount", etc., the ashless coal production
system 101 of Comparative Example illustrated in FIG. 2 is
described. The difference between the ashless coal production
system 101 and the ashless coal production system 1 (see, FIG. 1)
(the difference affecting the comparison of utility amount) is as
in the following [Difference a] to [Difference e]. As to the
configurations shared in common by the ashless coal production
system 101 and the ashless coal production system 1 (see, FIG. 1),
the same symbols are used.
[Difference a]
[0056] The ashless coal production system 1 illustrated in FIG. 1
is equipped with a preparation and dehydration tank 21 and a
preparation and temperature increase device 23. Instead, the
ashless coal production system 101 illustrated in FIG. 2 is
equipped with, in the order from the upstream side, a slurry
preparation tank 121, a dehydration tank 122 and a temperature
increase tank 123. In the slurry preparation tank 121, coal and a
solvent are mixed to prepare a slurry. In the dehydration tank 122,
coal in the slurry prepared in the slurry preparation tank 121 is
dehydrated. In the temperature increase tank 123, the temperature
of the slurry after being subjected to dehydration in the
dehydration tank 122 is increased.
[Difference b]
[0057] The ashless coal production system 1 illustrated in FIG. 1
is equipped with a vapor discharge unit 13 on the coal feed line
11, but in the ashless coal production system 101 illustrated in
FIG. 2, a vapor discharge unit 13 (see, FIG. 1) is not provided.
Therefore, the "problem of clogging" (described above) of the coal
feed line 11 cannot be reduced by a vapor discharge unit 13. In
order to prevent water in the coal from evaporating in the slurry
preparation tank 121, the solvent fed to the slurry preparation
tank 121 is cooled (for example, to 107.degree. C.). Specifically,
the solvent is cooled by the configurations or steps in the
following [Difference c] to [Difference e].
[Difference c]
[0058] The ashless coal production system 101 is equipped with a
first circulation path 141. The first circulation path 141 is a
flow channel corresponding to the first circulation path 41 and the
second circulation path 42 of the ashless coal production system 1
illustrated in FIG. 1. The first circulation path 141 illustrated
in FIG. 2 is a flow channel for feeding the solvent vapor
evaporated and separated in the first solvent recovery unit 37a to
the slurry preparation tank 121. On the first circulation path 141,
the dehydration tank 122 and the temperature increase tank 123 are
disposed in the order from the upstream side. In the first
circulation path 141, the solvent (solvent vapor) evaporated and
separated in the first solvent recovery unit 37a is flowed to the
dehydration tank 122 and the temperature increase tank 123. In this
manner, heat exchange is indirectly performed between the solvent
flowing through the first circulation path 141, and the slurry in
the dehydration tank 122 and the temperature increase tank 123.
That is, the heat energy of the solvent vapor evaporated and
separated in the first solvent recovery unit 37a is used as a heat
source for the dehydration and temperature increase of the slurry
in the dehydration tank 122 and the temperature increase tank
123.
[Difference d]
[0059] The ashless coal production system 101 is equipped with an
exhaust heat recovery boiler 153 and a cooler 155. The exhaust heat
recovery boiler 153 and the cooler 155 are disposed on the first
circulation path 141. In the exhaust heat recovery boiler 153,
saturated vapor is produced by utilizing the heat energy of the
solvent (solvent liquid) after being subjected to heat exchange in
the temperature increase tank 123. In the exhaust heat recovery
boiler 153, saturated vapor of 0.50 MPaG is produced at 8.18 t/h.
In the cooler 155, the solvent (solvent liquid) after being
subjected to heat recovery in the exhaust heat recovery boiler 153
is cooled by using cooling water.
[Difference e]
[0060] The ashless coal production system 101 is equipped with an
exhaust heat recovery boiler 193 and a cooler 195. The exhaust heat
recovery boiler 193 and the cooler 195 are disposed on the sixth
circulation path 46. In the case of the ashless coal production
system 101, the sixth circulation path 46 circulates the vapor
generated in the extraction tank 33 to the slurry preparation tank
121. In the exhaust heat recovery boiler 193, saturated vapor is
produced by utilizing the heat energy of the solvent (solvent
vapor) after the temperature increase of hot oil in the oil heater
91. In the exhaust heat recovery boiler 193, saturated vapor of 0.5
MPaG is produced at 1.72 t/h. In the cooler 195, the solvent
(solvent liquid) after being subjected to heat recovery in the
exhaust heat recovery boiler 193 is cooled by using cooling water.
In the exhaust heat recovery boiler 73 of the ashless coal
production system 101, saturated vapor of 0.50 MPaG is produced at
6.88 t/h.
(Comparison of Utility Amount)
[0061] The utility amount in the ashless coal production method of
this embodiment (in the case of using the ashless coal production
system 1 illustrated in FIG. 1), relative to the ashless coal
production method of Comparative Example (in the case of using the
ashless coal production system 101), is shown below. [0062] Amount
of saturated vapor generated: increase of about 50% [0063] Amount
of cooling water used: decrease of about 30 wt %
(Amount of Saturated Vapor Generated)
[0064] In the ashless coal production system 1 illustrated in FIG.
1, the amount of saturated vapor generated is the total amount of
saturated vapors produced in the exhaust heat recovery boiler 61
and the exhaust heat recovery boiler 73. In the ashless coal
production system 101 illustrated in FIG. 2, the amount of
saturated vapor generated is the total amount of saturated vapors
produced in the exhaust heat recovery boiler 153, the exhaust heat
recovery boiler 193 and the exhaust heat recovery boiler 73. It can
be seen from the comparison result above, when the ashless coal
production system 1 illustrated in FIG. 1 is used, the amount of
vapor recoverable in the exhaust heat recovery boiler can be
increased, compared with Comparative Example.
(Amount of Cooling Water Used)
[0065] In the ashless coal production system 1, the amount of
cooling water used is the total amount of cooling waters used in
the cooler 75 and the cooler 81. In the ashless coal production
system 101 illustrated in FIG. 2, the amount of cooling water used
is the total amount of cooling waters used in the cooler 155, the
cooler 195 and the cooler 75. It can be seen from the comparison
result above, when the ashless coal production system 1 illustrated
in FIG. 1 is used, the amount of cooling water used in the cooler
can be decreased, compared with Comparative Example. As a result,
the running cost of the ashless coal production system 1 can be
reduced, compared with Comparative Example.
(Effects)
[0066] The effects by the ashless coal production method of this
embodiment are described below. In the following, the device used
for performing each step (the device corresponding to each step) is
indicated in parentheses after the name of step.
(Effect 1)
[0067] The ashless coal production method (ashless coal production
system 1) includes a slurry preparation step (slurry preparation
device 20), an extraction step (extraction tank 33), a separation
step (separation unit 35), an ashless coal acquisition step (first
solvent recovery unit 37a), and a circulation step (first
circulation path 41 and second circulation path 42). The slurry
preparation step (slurry preparation device 20) is a step of mixing
coal and a solvent to prepare a slurry, and performing dehydration
and temperature increase of slurry. The extraction step (extraction
tank 33) is a step of heating the slurry obtained in the slurry
preparation step (slurry preparation device 20) to extract a
solvent-soluble component of the coal. The separation step
(separation unit 35) is a step of separating the slurry obtained in
the extraction step (extraction tank 33) into a solution containing
the solvent-soluble component of the coal and a solid-content
concentrated liquid having concentrated therein a solvent-insoluble
coal component. The ashless coal acquisition step (first solvent
recovery unit 37a) is a step of evaporating and separating the
solvent from the solution separated in the separation step
(separation unit 35) to obtain ashless coal. The circulation step
(first circulation path 41 and second circulation path 42) is a
step of circulating the solvent evaporated and separated in the
ashless coal acquisition step (first solvent recovery unit 37a).
The slurry preparation step (slurry preparation device 20) includes
a preparation and dehydration step (preparation and dehydration
tank 21) and a preparation and temperature increase step
(preparation and temperature increase device 23).
[Configuration 1-1]
[0068] The preparation and dehydration step (preparation and
dehydration tank 21) is a step of mixing a solvent liquid
circulated in the circulation step (first circulation path 41) and
the coal to thereby perform the preparation of the slurry and the
dehydration of the coal.
[Configuration 1-2]
[0069] The preparation and temperature increase step (preparation
and temperature increase device 23) is a step of mixing a solvent
vapor circulated in the circulation step (second circulation path
42) and the slurry to thereby perform the preparation and the
temperature increase of the slurry.
[0070] In the preparation and dehydration step (preparation and
dehydration tank 21) of [Configuration 1-1], mixing of solvent and
coal is performed. Due to this mixing, the solvent is brought into
direct contact with coal, and heat exchange is thereby directly
performed between the solvent and coal. In addition, in the
preparation and temperature increase step (preparation and
temperature increase device 23) of [Configuration 1-2], mixing of
solvent and slurry is performed. Due to this mixing, the solvent is
brought into direct contact with the slurry, and heat exchange is
thereby directly performed between the solvent and the slurry.
These direct heat exchanges are more efficient, compared with
indirect heat exchange (for example, heat exchange using a heat
exchanger). Specifically, for example, the heat exchange using a
heat exchanger requires providing a temperature difference between
the heat exchanger inlet temperature of the high temperature-side
fluid (fluid to increase temperature) and the heat exchanger outlet
temperature of the low temperature-side fluid (fluid to be
temperature-increased). On the other hand, in the direct heat
exchange performed in [Configuration 1-1] and [Configuration 1-2],
the above-described temperature difference can be regarded as 0.
Therefore, the heat exchange between coal and solvent and the heat
exchange between slurry and solvent can be efficiently performed
(this action is referred to as [Action 1-1]).
[0071] Furthermore, in the preparation and dehydration step
(preparation and dehydration tank 21) of [Configuration 1-1], a
solvent liquid (liquid) and coal (solid) are mixed. The heat
exchange between solvent liquid (liquid) and coal (solid) is more
efficient, compared with the heat exchange between solvent vapor
(gas) and coal (solid). In addition, in the preparation and
temperature increase step (preparation and temperature increase
device 23) of [Configuration 1-2], a solvent vapor (gas) and a
slurry (a mixture of solid and liquid) are mixed. The heat exchange
between solvent vapor (gas) and slurry (a mixture of solid and
liquid) is more efficient, compared with the heat exchange between
solvent vapor (gas) and coal (solid). Therefore, by virtue of
[Configuration 1-1] and [Configuration 1-2], the heat exchange
between coal and solvent and the heat exchange between slurry and
solvent can be efficiently performed (this action is referred to as
[Action 1-2]). Due to [Action 1-1] and [Action 1-2], the heat
energy generated in the production process of ashless coal can be
effectively utilized.
(Effect 2)
[Configuration 2]
[0072] In the preparation and temperature increase step
(preparation and temperature increase device 23), the concentration
of the slurry is adjusted to be an inlet concentration of the
extraction step (extraction tank 33), which is an inlet
concentration set in advance.
[0073] By virtue of [Configuration 2], the concentration of slurry
need not be adjusted after the preparation and temperature increase
step but before the extraction step (between the preparation and
temperature increase device 23 and the extraction tank 33).
Therefore, the number of devices can be reduced, compared with a
case where a device for adjusting the concentration of slurry after
the extraction step but before the extraction step needs to be
provided. As a result, the equipment cost of the equipment (ashless
coal production system 1) for performing the ashless coal
production method can be reduced.
(Effect 3)
[Configuration 3]
[0074] In the preparation and temperature increase step
(preparation and temperature increase device 23), the temperature
of slurry is increased to an inlet temperature of a step (for
example, preheater 31) performed following the slurry preparation
step (slurry preparation device 20), which is an inlet temperature
set in advance.
[0075] By virtue of [Configuration 3], the temperature of slurry
need not be adjusted after the preparation and temperature increase
step but before a step performed following the slurry preparation
step (between the preparation and temperature increase device 23
and, for example, the preheater 31). Therefore, the number of
devices can be reduced, compared with a case where a device for
adjusting the temperature of slurry after the preparation and
temperature increase step but before a step performed following the
slurry preparation step needs to be provided. As a result, the
equipment cost of the equipment (ashless coal production system 1)
for performing the ashless coal production method can be
reduced.
(Effect 4)
[Configuration 4]
[0076] In the preparation and temperature increase step
(preparation and temperature increase device 23), solvent vapor and
slurry is mixed by a venturi scrubber 23a.
[0077] In the venturi scrubber 23a of [Configuration 4], the mixing
of solvent vapor (gas) and slurry (a mixture of solid and liquid)
can be unfailingly performed. Therefore, the heat exchange between
solvent vapor and slurry can be efficiently performed.
(Effect 5)
[0078] The ashless coal production method (ashless coal production
system 1) includes a coal feeding step (coal feed line 11) and a
vapor discharging step (vapor discharge unit 13). The coal feeding
step (coal feed line 11) is a step of feeding coal to be used in
the slurry preparation step (to be fed to the slurry preparation
device 20) by way of the coal feed line 11.
[Configuration 5]
[0079] The vapor discharging step (vapor discharge unit 13) is a
step of flowing a purge gas into the coal feed line 11 to thereby
discharge the vapor produced in the preparation and dehydration
step (preparation and dehydration tank 21) from the coal feed line
11.
[0080] By virtue of [Configuration 5], the vapor in the coal feed
line 11 can be kept from forming a condensate. Therefore, clogging
of the coal feed line 11 due to adhesion of coal to the condensate
can be suppressed. In addition, since [Configuration 5] can keep
the vapor in the coal feed line 11 from forming a condensate, it is
not necessary to prevent the generation of vapor in the preparation
and dehydration step (preparation and dehydration tank 21). In
turn, the solvent fed to the preparation and dehydration step
(preparation and dehydration tank 21) need not be cooled to such a
degree that vapor is not generated in the preparation and
dehydration step (preparation and dehydration tank 21). Therefore,
the number of devices (or the scale of device) can be reduced,
compared with a case where a cooler (for example, the cooler 155 of
FIG. 2) for performing the cooling above needs to be provided. As a
result, the equipment cost of the equipment (ashless coal
production system 1) for performing the ashless coal production
method can be reduced.
Modification Example
[0081] The embodiment above can be variously modified. For example,
although the temperature of the solvent or slurry is exemplified in
FIG. 1, the temperature of the solvent or slurry may be a
temperature different from the temperature exemplified in FIG.
1.
[0082] In addition, for example, although the state of solvent
(solvent liquid or solvent vapor) is distinguished by a solid arrow
and a dot-dash arrow in FIG. 1, the state of solvent may be a state
different from the state illustrated in FIG. 1. However, the
solvent fed to the preparation and dehydration tank 21 is a solvent
liquid, and the solvent fed to the venturi scrubber 23a is a
solvent vapor.
[0083] Furthermore, for example, the order of respective steps (the
connection order of respective devices) or the presence or absence
of each step (each device) may be appropriately changed. [Example
1]: All or part of third circulation path 43, fourth circulation
path 44, fifth circulation path 45, sixth circulation path 46, and
devices disposed on these circulation paths may not be present.
[Example 2]: Although the solvent flowing through the sixth
circulation path 46 is fed to the oil/water separation tank 83
after being subjected to heat exchange in the heat exchanger 77,
the solvent flowing through the sixth circulation path 46 may be
fed to the cooler 81 after being subjected to heat exchange in the
heat exchanger 77.
[0084] In addition, for example, part or the whole configurations
of the ashless coal production system 101 of Comparative Example
illustrated in FIG. 2 may be combined with or substituted by part
or the whole configurations of the ashless coal production system 1
illustrated in FIG. 1. Specifically, for example, the exhaust heat
recovery boiler 193 on the sixth circulation path 46 illustrated in
FIG. 2 may be disposed on the sixth circulation path 46 of the
ashless coal production system 1 illustrated in FIG. 1.
[0085] While the present invention has been described in detail and
with reference to specific embodiments thereof, it will be apparent
to one skilled in the art that various changes and modifications
can be made therein without departing from the spirit and scope of
the present invention. The present application is based on Japanese
patent application (Patent Application No. 2013-267439) filed on
Dec. 25, 2013 and the contents thereof are incorporated herein by
reference.
INDUSTRIAL APPLICABILITY
[0086] According to the present invention, the heat exchange
between coal and solvent and the heat exchange between slurry and
solvent are efficiently performed, so that the heat energy
generated in the production process of ashless coal can be
effectively utilized and thereby the ashless coal can be produced
at a low cost.
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
[0087] 1 Ashless coal production system [0088] 11 Coal feed line
[0089] 13 Vapor discharge unit [0090] 20 Slurry preparation device
[0091] 21 Preparation and dehydration tank [0092] 23 Preparation
and temperature increase device [0093] 23a Venturi scrubber [0094]
33 Extraction tank [0095] 35 Separation unit [0096] 37 Solvent
recovery unit [0097] 41 to 46 Circulation path
* * * * *