U.S. patent application number 14/764861 was filed with the patent office on 2015-12-31 for method for producing residue 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 | 20150376528 14/764861 |
Document ID | / |
Family ID | 51354027 |
Filed Date | 2015-12-31 |
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United States Patent
Application |
20150376528 |
Kind Code |
A1 |
SAKAI; Koji ; et
al. |
December 31, 2015 |
METHOD FOR PRODUCING RESIDUE COAL
Abstract
In a method for producing residue coal according to the present
invention, a solvent is separated by evaporation from a solid
material concentrate, which has been separated in a gravity
settling vessel (7), in a solvent separator (10), thereby producing
a residue coal mixture in which the solvent is remained in the
residue coal. Subsequently, the remaining solvent is separated by
evaporation from the residue coal mixture in a drier (11), thereby
producing the residue coal. In the drier (11), the remaining
solvent is separated by evaporation from the residue coal mixture
utilizing a heat the residue coal mixture itself has. In this
manner, an apparatus for drying the residue coal mixture can be
simplified, and the cost required for the drying can be
reduced.
Inventors: |
SAKAI; Koji; (Hyogo, JP)
; OKUYAMA; Noriyuki; (Hyogo, JP) ; YOSHIDA;
Takuya; (Hyogo, JP) ; KINOSHITA; Shigeru;
(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: |
51354027 |
Appl. No.: |
14/764861 |
Filed: |
February 7, 2014 |
PCT Filed: |
February 7, 2014 |
PCT NO: |
PCT/JP2014/052975 |
371 Date: |
July 30, 2015 |
Current U.S.
Class: |
44/627 |
Current CPC
Class: |
C10L 2290/08 20130101;
C10L 5/00 20130101; C10L 9/02 20130101; C10L 2290/544 20130101;
C10L 2290/54 20130101; C10L 2290/58 20130101; C10L 5/04
20130101 |
International
Class: |
C10L 5/00 20060101
C10L005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 13, 2013 |
JP |
2013-025509 |
Claims
1. A method for producing a by-product coal, comprising: (1)
heating a slurry prepared by mixing a coal and a solvent, thereby
extracting a coal component soluble in the solvent; (2) separating
the slurry which has been obtained in the extraction (1) into a
solution in which the coal component soluble in the solvent is
dissolved and a solid-content concentrated liquid in which a coal
component insoluble in the solvent is concentrated; and (3)
evaporating and separating the solvent from the solid-content
concentrated liquid which has been separated in (2), thereby
acquiring a by-product coal, wherein (3) comprises: (3a)
evaporating and separating the solvent from the solid-content
concentrated liquid which has been separated in (2), thereby
acquiring a by-product coal mixture containing a by-product coal in
which the solvent remains; and (3b) evaporating and separating the
remaining solvent from the by-product coal mixture, thereby
acquiring the by-product coal, wherein, in (3b), the remaining
solvent is evaporated and separated from the by-product coal
mixture by exploiting heat that the by-product coal mixture itself
has.
2. The method for producing a by-product coal according to claim 1,
wherein a temperature of the solid-content concentrated liquid to
be fed to (3a) is adjusted so that the by-product coal mixture to
be fed to (3b) has a calorific value allowing the remaining solvent
to be evaporated and separated from the by-product coal
mixture.
3. The method for producing a by-product coal according to claim 2,
wherein the temperature of the solid-content concentrated liquid to
be fed to (3a) is adjusted by heating at least one of the slurry to
be fed to (2) and the solid-content concentrated liquid to be fed
to (3).
4. The method for producing a by-product coal according to claim 1,
wherein (2) is performed under a pressurized condition, and in
(3a), the solvent is evaporated and separated from the
solid-content concentrated liquid by spraying the solid-content
concentrated liquid which has been in a high-temperature
high-pressure condition, which does not allow the solvent to be
evaporated and separated, into a normal-pressure tank.
5. The method for producing a by-product coal according to claim 2,
wherein (2) is performed under a pressurized condition, and in
(3a), the solvent is evaporated and separated from the
solid-content concentrated liquid by spraying the solid-content
concentrated liquid which has been in a high-temperature
high-pressure condition, which does not allow the solvent to be
evaporated and separated, into a normal-pressure tank.
6. The method for producing a by-product coal according to claim 3,
wherein (2) is performed under a pressurized condition, and in
(3a), the solvent is evaporated and separated from the
solid-content concentrated liquid by spraying the solid-content
concentrated liquid which has been in a high-temperature
high-pressure condition, which does not allow the solvent to be
evaporated and separated, into a normal-pressure tank.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for producing a
by-product coal which is yielded as a by-product when an ashless
coal is obtained through removal of ash components from coal.
BACKGROUND ART
[0002] A method for producing an ashless coal is disclosed in
Patent Document 1. In such a production method, a raw material coal
as a mixture of steam coal and caking coal is mixed with a solvent
to prepare a slurry, and the slurry thus prepared is heated,
thereby extracting coal components soluble in the solvent, then the
gravitational settling method is applied to the slurry in which the
coal components has been extracted, thereby separating the slurry
into a solution which contains the coal components soluble in the
solvent and a solid-content concentrated liquid containing coal
components insoluble in the solvent, and further the removal of the
solvent from the separated solution is carried out, thereby
obtaining an ashless coal.
PRIOR ART DOCUMENT
Patent Documents
[0003] Patent Document 1: JP-A-2009-227718
SUMMARY OF THE INVENTION
Problem that the Invention is to Solve
[0004] In the process for producing an ashless coal, a by-product
coal is yielded as a by-product in addition to an ashless coal as
the final product.
[0005] The by-product coal is obtained through the evaporative
separation of a solvent from a solid-content concentrated liquid.
In the process, a by-product coal mixture containing the by-product
coal in which the solvent remains is obtained first through the
evaporative separation of the solvent from the solid-content
concentrated liquid, and then the by-product coal is obtained
through the evaporative separation of the remaining solvent from
the by-product coal mixture.
[0006] In the case of intending to obtain a by-product coal through
the drying of a large quantity of by-product coal mixture, however,
there arises a problem that there is no drying means which allows
the temperature of the by-product coal mixture to be increased to
temperatures equal to or higher than the boiling temperature of the
solvent (about 240.degree. C.). The steam temperature of a steam
tube dryer as an example of drying means is 220.degree. C. at the
highest, and hence prolongation of a residence time becomes
necessary, which results in a cost increase.
[0007] An object of the present invention is therefore to provide a
method for producing a by-product coal, which allows a reduction in
cost for drying a by-product coal mixture through the
simplification of a device for drying the by-product coal
mixture.
Means for Solving the Problem
[0008] A method for producing a by-product coal according to the
present invention comprises: an extraction step of heating a slurry
prepared by mixing a coal and a solvent, thereby extracting a coal
component soluble in the solvent; a separation step of separating
the slurry which has been obtained in the extraction step into a
solution in which the coal component soluble in the solvent is
dissolved and a solid-content concentrated liquid in which a coal
component insoluble in the solvent is concentrated; and a
by-product coal acquirement step of evaporating and separating the
solvent from the solid-content concentrated liquid which has been
separated in the separation step, thereby acquiring a by-product
coal; wherein the by-product coal acquirement step comprises: a
by-product coal mixture acquirement step of evaporating and
separating the solvent from the solid-content concentrated liquid
which has been separated in the separation step, thereby acquiring
a by-product coal mixture containing a by-product coal in which the
solvent remains; and a by-product coal drying step of evaporating
and separating the remaining solvent from the by-product coal
mixture, thereby acquiring the by-product coal, wherein, in the
by-product coal drying step, the solvent remaining in the
by-product coal mixture is evaporated and separated by exploiting
heat that the by-product coal mixture itself has.
Advantageous Effects of the Invention
[0009] According to the method for producing a by-product coal in
the present invention, the device for drying a by-product coal
mixture is simplified, and thus, the cost for drying the by-product
coal mixture can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic diagram of an ashless coal production
equipment.
[0011] FIG. 2 is a graph showing evaluation results based on drying
time.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0012] In the following, an exemplary embodiment for carrying out
the present invention is illustrated in detail by reference to the
drawings.
(Method for Producing Ashless Coal)
[0013] The method of producing a by-product coal in accordance with
an exemplary embodiment in the present invention is carried out in
ashless-coal production equipment 100 to be used for a method of
producing an ashless coal. As shown in FIG. 1, the ashless-coal
production equipment 100 includes, in the order from the upstream
side of the production process of an ashless coal (HPC), a coal
hopper 1, a solvent tank 2, a slurry preparation tank 3, a
transport pump 4, a preheater 5, an extraction tank 6, a
gravitational settling tank 7, a filter unit 8, solvent separators
9 and 10, and a dryer 11.
[0014] The method of producing an ashless coal includes a slurry
preparation step, an extraction step, a separation step, an ashless
coal acquirement step and a by-product coal acquirement step. Of
these steps, the slurry preparation step, the extraction step, the
separation step and the by-product coal acquirement step are
included in the method for producing a by-product coal in
accordance with the present embodiment. Each of these steps is
explained below. Additionally, a coal to be used as a raw material
in the present production method has no particular restriction, and
bituminous coal high in extraction rate may be used or a low rank
coal low in price (such as subbituminous coal or brown coal) may be
used. Herein, the term "ashless coal" refers to a coal having an
ash content of 5 wt % or less, preferably 3 wt % or less.
(Slurry Preparation Step)
[0015] The slurry preparation step is a step of preparing a slurry
by mixing a coal and a solvent. This slurry preparation step is
performed in the slurry preparation tank 3 in FIG. 1. The coal as a
raw material is added to the slurry preparation tank 3 from the
coal hopper 1, and simultaneously, a solvent is added to the slurry
preparation tank 3 from the solvent tank 2. The coal and solvent
which are added to the slurry preparation tank 3 are mixed by the
stirrer 3a, thereby forming into a slurry composed of the coal and
the solvent.
[0016] The mixing proportion of the coals to the solvent is e.g.
from 10 to 50 wt %, preferably from 20 to 35 wt %, on a dried coal
basis.
(Extraction Step)
[0017] The extraction step is a step of extracting coal components
soluble in the solvent (a step of dissolving such components in the
solvent) by heating the slurry obtained in the slurry preparation
step. This extraction step is performed in the preheater 5 and the
extraction tank 6 in FIG. 1. The slurry which has been prepared in
the slurry preparation tank 3 is fed to the preheater 5 by means of
the transport pump 4, heated up to a predetermined temperature,
then fed to the extraction tank 6, and further kept at a
predetermined temperature while stirring by the stirrer 6a. In this
way, the extraction is performed.
[0018] In a case of extracting coal components soluble in the
solvent by heating the slurry prepared by mixing the coal with the
solvent, a solvent in which the coal is highly soluble, more
specifically an aromatic solvent (a hydrogen donative solvent or a
hydrogen nondonative solvent) in many cases, is mixed with a coal,
and by heating the resulting mixture, organic components in the
coal are extracted.
[0019] The hydrogen nondonative solvent is a coal-derived solvent
obtained mainly by refining carbonization products of coal and
predominantly composed of bicyclic aromatic compounds. Because such
a hydrogen nondonative solvent is stable even under conditions of
heating and has a high affinity for coal, the proportion of soluble
components (coal components) extracted with the solvent (hereafter
referred to as the extraction rate, too) is high, and the solvent
can be easily recovered by the methods such as distillation. Main
ingredients in the hydrogen nondonative solvent are bicyclic
aromatic compounds such as naphthalene, methylnaphthalene,
dimethylnaphthalene or trimethylnaphthalene. As the other
ingredients in the hydrogen nondonative solvent, examples thereof
include a naphthalene, a anthracene and a fluorine, which each have
aliphatic side chains, and further include biphenyl and an
alkylbenzene having long-chain aliphatic side chains.
[0020] Although the case of using a hydrogen nondonative compound
as the solvent is described in the above explanation, it goes
without saying that any of hydrogen donative compounds (including
the case of coal liquefied oil), typified by tetralin, can be used
as the solvent. The use of a hydrogen donative solvent brings about
enhancement of ashless coal yield.
[0021] Additionally, the solvent has no particular restriction as
to its boiling temperature. From the viewpoints of pressure
reductions in the extraction step and separation step, an
extraction rate in the extraction step, a solvent recovery rate in
the ashless coal acquirement step and the like, solvents having
boiling temperatures in a range of 180.degree. C. to 300.degree.
C., especially 240.degree. C. to 280.degree. C., can be used
favorably. In the present embodiment, the boiling temperature of
the solvent is about 240.degree. C.
[0022] The heating temperature of the slurry in the extraction step
has no particular limitations so long as dissolution of
solvent-soluble components can be achieved. From the viewpoint of
ensuring thorough dissolution of solvent-soluble components and
improvement in extraction rate, the heating temperature is e.g.
from 300.degree. C. to 420.degree. C., preferably 360.degree. C. to
400.degree. C. In the present embodiment, the slurry is heated by
the preheater 5, and thereby, as mentioned later, the temperature
of a solid-content concentrated liquid to be fed to a solvent
separator 10 is adjusted so that a by-product coal mixture to be
fed to a dryer 11 has a calorific value allowing the remaining
solvent to be evaporated and separated from the by-product coal
mixture.
[0023] The heating time (extraction time) also has no particular
limitations, but from the viewpoint of ensuring thorough
dissolution and improvement in extraction rate, the heating time is
e.g. from 10 to 60 minutes. Herein, the term "heating time" refers
to the sum of the heating time in the preheater 5 in FIG. 1 and the
heating time in the extraction tank 6 in FIG. 1.
[0024] The extraction step is carried out in the presence of an
inert gas such as nitrogen. The suitable pressure inside the
extraction tank 6 is e.g. from 1.0 to 2.0 MPa, though it depends on
the temperature during the extraction and the vapor pressure of a
solvent to be used. When the pressure inside the extraction tank 6
is lower than the vapor pressure of the solvent, the solvent
vaporizes and the solvent cannot be confined within the liquid
phase, and the extraction ends in failure. In order to confine the
solvent within the liquid phase, pressure higher than the vapor
pressure of the solvent is therefore necessary. On the other hand,
when the pressure is too high, it brings about increases in costs
of equipment and operation, and it is therefore uneconomical.
(Separation Step)
[0025] The separation step is a step of separating the slurry which
has been obtained in the extraction step into a solution in which
coal components soluble in the solvent are dissolved and a
solid-content concentrated liquid (solvent-insoluble component
concentrated liquid) which contains coal components insoluble in
the solvent (solvent-insoluble components such as ash components)
in a concentrated state, by the gravitational settling method. This
separation step is carried out in the gravitational settling tank 7
in FIG. 1. In the gravitational settling tank 7, the slurry which
has been obtained in the extraction step is separated into
supernatant liquor as the solution and the solid-content
concentrated liquid by dint of gravity. The supernatant liquor in
the upper part of the gravitational settling tank 7 is discharged
into the solvent separator 9, if necessary, by way of the filter
unit 8, and simultaneously, the solid-content concentrated liquid
settled in the lower part of the gravitational settling tank 7 is
discharged into the solvent separator 10.
[0026] The gravitational settling method is a method of holding the
slurry in the tank, and settling and separating the
solvent-insoluble components by exploiting gravity. The
solvent-insoluble components (e.g. ash components) having a
specific gravity larger than that of the solution in which coal
components soluble in the solvent are dissolved, settle in the
lower part of the gravitational settling tank 7 by the force of
gravity. By continuously discharging the supernatant liquor from
the upper part of the tank and the solid-content concentrated
liquid from the lower part of the tank while continuously feeding
the slurry into the tank, continuous separation treatment becomes
possible.
[0027] For prevention of reprecipitation of solvent-soluble
components eluted from the coal, it is appropriate that the inside
of the gravitational settling tank 7 be kept warm (or in a heated
state) or be left pressurized. The warming (heating) temperature is
e.g. from 300.degree. C. to 380.degree. C., and the pressure inside
the tank is e.g. from 1.0 MPa to 3.0 MPa.
[0028] In addition to the gravitational settling method, examples
of methods for separating the solution which contains coal
components dissolved in the solvent from the slurry which has been
obtained in the extraction step include a filtration method, a
centrifugal separation method and the like.
(Ashless Coal Acquirement Step)
[0029] The ashless coal acquirement step is a step of acquiring an
ashless coal (HPC) through the evaporative separation of the
solvent from the solution (supernatant liquor) which has been
separated in the separation step. This ashless coal acquirement
step is carried out in the solvent separator 9 in FIG. 1. After the
filtration in the filter unit 8, the solution which has been
separated in the gravitational settling tank 7 is fed to the
solvent separator 9, and in the solvent separator 9, the solvent is
evaporated and separated from the supernatant liquor. The
evaporative separation of the solvent from the solution is
preferably carried out in the presence of an inert gas such as
nitrogen. In the present embodiment, the solvent is evaporated and
separated from the solution in an atmosphere of nitrogen gas
introduced into the solvent separator 9.
[0030] As the method for separating the solvent from the solution
(supernatant liquor), a common distillation or evaporation method
or the like can be used. The solvent which has been separated in
the solvent separator 9 is returned to the solvent tank 2, and is
used in cycles. Circulating use of the solvent is preferable, but
not essential (which is also applicable to the by-product coal
acquirement step mentioned later). By separating the solvent from
the supernatant liquor, an ashless coal (HPC) containing
substantially no ash components can be obtained.
[0031] The ashless coal contains almost no ash components, is
absolutely free of moisture, and offers a calorific value higher
than a raw material coal. In addition, the ashless coal has an
extensive improvement in coal plastic properties (flowability)
which are especially important for a raw material of steelmaking
coke, and even when the raw material coal has no plastic
properties, the ashless coal (HPC) obtained from it has excellent
plastic properties. Accordingly, the ashless coal can be used e.g.
in a coal blend as a raw material for making coke. Further, the
ashless coal almost free of ash components has high combustion
efficiency and can reduce the amount of ashes produced. Attention
is therefore being given to the use of ashless coal as a gas
turbine direct-injection fuel in a high-efficiency, combined-cycle
generation system utilizing gas turbine combustion.
(By-Product Coal Acquirement Step)
[0032] The by-product coal acquirement step is a step of
evaporating and separating the solvent from the solid-content
concentrated liquid which has been separated in the separation
step, thereby acquiring a by-product coal. This by-product coal
acquirement step includes a by-product coal mixture acquirement
step and a by-product coal drying step.
(By-Product Coal Mixture Acquirement Step)
[0033] The by-product coal mixture acquirement step is a step of
evaporating and separating the solvent from the solid-content
concentrated liquid which has been separated in the separation
step, thereby acquiring a by-product coal mixture containing a
by-product coal in which the solvent remains. This by-product coal
mixture acquirement step is carried out in the solvent separator 10
in FIG. 1. The solid-content concentrated liquid which has been
separated by the gravitational settling tank 7 is fed to the
solvent separator 10, and the solvent is evaporated and separated
from the solid-content concentrated liquid in the solvent separator
10. The evaporative separation of the solvent from the
solid-content concentrated liquid is preferably performed in the
presence of an inert gas such as nitrogen. In the present
embodiment, the solvent separator 10 is a flash distillation tank
to be used in a flash distillation method. The flash distillation
method is a method of spraying a solid-content concentrated liquid
into a tank inside of which has been in an atmosphere of nitrogen
gas, thereby evaporating and separating the solvent.
[0034] The method for separating the solvent from the solid-content
concentrated liquid is not limited to the flash distillation
method, and a common distillation or evaporation method can be
applicable thereto as in the case of the ashless coal acquirement
step. The solvent which has been separated in the solvent separator
10 is returned to the solvent tank 2, and is used in cycles. By
separating the solvent from the solid-content concentrated liquid,
a by-product coal mixture containing the by-product coal in which
the solvent remains in a proportion of 5 to 10 wt % can be
obtained.
[0035] The solid-content concentrated liquid which has been
separated by the gravitational settling tank 7 has been in a
high-temperature high-pressure condition which does not allow the
solvent to be evaporated and separated. By spraying the
solid-content concentrated liquid which has been in such a
condition into the solvent separator 10 the inside of which is held
at normal pressure, the pressure on the solid-content concentrated
liquid is released. Thus, the boiling temperature of the solvent is
lowered, and the solvent is evaporated and separated at a dash from
the high-temperature solid-content concentrated liquid. At this
time, the temperature of the solid-content concentrated liquid to
be fed to the solvent separator 10 has been adjusted so that the
by-product coal mixture to be fed to the dryer 11 at a later time
has a calorific value allowing the remaining solvent to be
evaporated and separated from the by-product coal mixture. This
temperature adjustment is carried out, as mentioned above, by means
of the preheater 5 for heating the slurry which has been prepared
in the slurry preparation tank 3. This temperature adjustment may
be carried out by heating the solid-content concentrated liquid
which has been separated by the gravitational settling tank 7 but
before feeding into the solvent separator 10. Alternatively, this
temperature adjustment may be carried out by heating both the
slurry which has been prepared in the slurry preparation tank 3 and
the solid-content concentrated liquid which has been separated by
the gravitational settling tank 7.
(By-Product Coal Drying Step)
[0036] The by-product coal drying step is a step of evaporating and
separating the remaining solvent from the by-product coal mixture,
thereby acquiring the by-product coal. This by-product coal drying
step is carried out in the dryer 11 in FIG. 1. The by-product coal
mixture which has been obtained in the solvent separator 10 is fed
to the dryer 11 and the remaining solvent is evaporated and
separated from the by-product coal mixture in the dryer 11. The
evaporative separation of the solvent from the by-product coal
mixture is preferably carried out in the presence of an inert gas
such as nitrogen. In the present embodiment, the dryer 11 is a
rotary dryer which holds therein the by-product coal mixture and
carries out stirring while circulating therein a nitrogen gas as
carrier gas. By separating the remaining solvent from the
by-product coal mixture, it becomes possible to obtain the
by-product coal (RC, also referred to as residual coal) in which
solvent-insoluble components including ash components have been
concentrated.
[0037] The by-product coal contains absolutely no moisture though
it contains ash components, and has a sufficient calorific value.
The by-product coal shows no coal plastic properties, and when used
in a coal blend, it does not impair the coal plastic properties of
other kinds of coals included in the coal blend because it has been
subjected to elimination of oxygen-containing functional groups.
Thus, this by-product coal can be used as a portion of the coal
blend for coke-making material as in the case of usual non- or
slightly-caking coals, and may also be used for various kinds of
fuels without being used as a coke-making material.
[0038] In the present embodiment, the remaining solvent is
evaporated and separated from the by-product coal mixture in the
dryer 11 by exploiting the heat that the by-product coal mixture
itself, which is the mixture including the by-product coal and
solvent, has. More specifically, in the dryer 11, the by-product
coal mixture is only retained and stirred, and any heat is not
given to the by-product coal mixture. The expression that "the heat
that the by-product coal mixture itself has" means the heat borne
(possessed) by the by-product coal mixture obtained through the
separation of the solvent from the solid-content concentrated
liquid, and does not mean the heat generated from the by-product
coal mixture through chemical reaction. Since the by-product coal
mixture itself has heat, the by-product coal mixture has a given
calorific value. The calorific value that the by-product coal
mixture has is a value allowing the remaining solvent to be
evaporated and separated from the by-product coal mixture. When a
main ingredient of the solvent is methylnaphthalene, the calorific
value required for evaporating and separating the solvent in a unit
amount is 330 kJ/kg (the calorific value required for evaporation
of 1 kg of the solvent). As mentioned above, by adjusting the
temperature of the solid-content concentrated liquid fed to the
solvent separator 10, the by-product coal mixture fed to the dryer
11 is adjusted so as to have such a calorific value.
[0039] In order to dry powder, it generally becomes necessary to
use a device for applying heat to the powder. However, the
by-product coal mixture itself, which is obtained in the by-product
coal mixture acquirement step (the solvent separator 10), has a
considerable amount of heat. Thus, by evaporating and separating
the remaining solvent from the by-product coal mixture by
exploiting the heat that the by-product coal mixture itself has,
necessity for applying heat to the by-product coal mixture is
eliminated. With this being the situation, a device for drying the
by-product coal mixture can be simplified, and costs for drying the
by-product coal mixture can be reduced.
[0040] In addition, by adjusting the temperature of the
solid-content concentrated liquid fed to the by-product coal
mixture acquirement step (the solvent separator 10), the by-product
coal mixture fed to the by-product coal drying step (the dryer 11)
is adjusted so as to have a calorific value allowing the remaining
solvent to be evaporated and separated from the by-product coal
mixture. In general the application of heat to liquid is greater in
efficiency than the case where heat is applied to solid. The
temperature adjustment of the solid-content concentrated liquid in
a liquid state is therefore easier than that of the by-product coal
mixture in a somewhat solidified state. Thus, the temperature
adjustment is not given to the by-product coal mixture fed to the
by-product coal drying step (the dryer 11), but the temperature
adjustment is given to the solid-content concentrated liquid fed to
the by-product coal mixture acquirement step (the solvent separator
10). Thereby, it becomes possible to appropriately provide the
by-product coal mixture with a calorific value allowing the
remaining solvent to be evaporated and separated from the
by-product coal mixture.
[0041] Further, the temperature of the solid-content concentrated
liquid fed to the by-product coal mixture acquirement step (the
solvent separator 10) is adjusted by heating at least one of the
slurry prepared in the slurry preparation tank 3 and the
solid-content concentrated liquid separated by the gravitational
settling tank 7. Because the slurry and the solid-content
concentrated liquid are liquids, heat can be applied to them with
efficiency. Thus, by heating the slurry or the solid-content
concentrated liquid, the temperature of the solid-content
concentrated liquid fed to the by-product coal mixture acquirement
step can be adjusted appropriately.
(Drying Time Evaluation)
[0042] Next, the time required to dry the by-product coal was
evaluated at each of different drying temperatures. For making such
evaluations, a tube furnace was used. In a procedure for each
evaluation, first of all, the temperature was raised so that the
temperature inside the furnace reached a predetermined drying
temperature while circulating a nitrogen gas through the furnace.
Then, a by-product coal mixture containing 28 wt % of the solvent,
as a sample, was put in the furnace in a condition that the sample
was placed on a porcelain dish fitted with a thermocouple.
Thereafter, drying time measurement was started at the time when
the temperature of the sample reached the predetermined drying
temperature. The sample was taken out after the passage of a
predetermined time, and examined on the solvent content therein. In
accordance with this procedure, the evaluation is performed under
each of different drying temperatures of 210.degree. C.,
250.degree. C. and 270.degree. C. Evaluation results obtained are
shown in FIG. 2.
[0043] As to the times required to reduce the solvent content in
the sample to 2 wt % under different drying temperatures, they were
about 30 minutes under the drying temperature of 210.degree. C.,
about 15 minutes under the drying temperature of 250.degree. C. and
about 10 minutes under the drying temperature of 270.degree. C.
These results show that, as compared the case of the drying
temperature of 210.degree. C. corresponding to the steam
temperature of a steam tube dryer, the time required for drying
under the temperature of 250.degree. C. can be cut in about
one-half. In addition, it is also shown that the time required for
drying under the temperature of 270.degree. C. can be reduced to
about one-third as compared with the case under the drying
temperature of 210.degree. C.
(Effects)
[0044] As mentioned above, according to the method of producing a
by-product coal according to the present embodiment, the remaining
solvent is evaporated and separated from the by-product coal
mixture by exploiting heat that the by-product coal mixture itself
has, in the by-product coal drying step (the dryer 11). In general,
a device for applying heat to powder becomes necessary for the
powder to be dried. However, the by-product coal mixture itself,
which is obtained in the by-product coal mixture acquirement step
(the solvent separator 10), has a considerable amount of heat.
Thus, by evaporating and separating the remaining solvent from the
by-product coal mixture by exploiting the heat that the by-product
coal mixture itself has, necessity for applying heat to the
by-product coal mixture is eliminated. By doing so, a device for
drying the by-product coal mixture can be simplified, and costs for
drying the by-product coal mixture can be reduced.
[0045] In addition, by adjusting the temperature of the
solid-content concentrated liquid fed to the by-product coal
mixture acquirement step (the solvent separator 10), the by-product
coal mixture fed to the by-product coal drying step (the dryer 11)
is adjusted so as to have a calorific value allowing the remaining
solvent to be evaporated and separated from the by-product coal
mixture. In general, the application of heat to liquid is greater
in efficiency the case where heat is applied to solid. Therefore,
the temperature adjustment of the solid-content concentrated liquid
in a liquid state is easier than that of the by-product coal
mixture in a somewhat solidified state. Thus, the temperature
adjustment is not given to the by-product coal mixture fed to the
by-product coal drying step, but the temperature adjustment is
given to the solid-content concentrated liquid fed to the
by-product coal mixture acquirement step. By doing so, it becomes
possible to appropriately provide the by-product coal mixture with
a calorific value allowing the remaining solvent to be evaporated
and separated from the by-product coal mixture.
[0046] Further, the temperature of the solid-content concentrated
liquid fed to the by-product coal mixture acquirement step (the
solvent separator 10) is adjusted by heating at least one of the
slurry and the solid-content concentrated liquid. Because the
slurry and the solid-content concentrated liquid are liquids, heat
can be applied to them with efficiency. Thus, by heating the slurry
or the solid-content concentrated liquid, the temperature of the
solid-content concentrated liquid fed to the by-product coal
mixture acquirement step can be adjusted appropriately.
[0047] Furthermore, in the by-product coal mixture acquirement step
(the solvent separator 10), the solid-content concentrated liquid
which has been in a high-temperature high-pressure condition, which
does not allow the solvent to be evaporated and separated, is
sprayed into a tank the inside of which is kept at normal pressure,
and then, the pressure on the solid-content concentrated liquid is
released. Thus, the boiling temperature of the solvent is lowered,
and the solvent is evaporated and separated at a dash from the
high-temperature solid-content concentrated liquid. With this being
the situation, the solvent can be appropriately evaporated and
separated from the solid-content concentrated liquid.
MODIFICATION EXAMPLES OF PRESENT EMBODIMENT
[0048] Although an exemplary embodiment in the present invention
has been described in the foregoing, it merely exemplifies the
concrete example and should not be construed as particularly
limiting the present invention. The concrete configuration and on
the like can be modified as appropriate. Further, the actions and
effects described in the embodiment in the present invention are
merely recited as the most appropriate actions and effects produced
by the present invention, and actions and effects which can be
achieved by the present invention should not be construed as being
limited to those described in the exemplary embodiment in the
present invention.
[0049] This application is based on Japanese Patent Application No.
2013-025509 filed on Feb. 13, 2013, the entire contents of which
are incorporated herein by reference.
INDUSTRIAL APPLICABILITY
[0050] The method for producing a by-product coal in the present
invention allows simplification of a device for drying a by-product
coal mixture and the reduction of costs for drying.
DESCRIPTION OF REFERENCE NUMBERS
[0051] 1: Coal hopper
[0052] 2: Solvent tank
[0053] 3: Slurry preparation tank
[0054] 3a: Stirrer
[0055] 4: Transport pump
[0056] 5: Preheater
[0057] 6: Extraction tank
[0058] 6a: Stirrer
[0059] 7: Gravitational settling tank
[0060] 8: Filter unit
[0061] 9, 10: Solvent separator
[0062] 11: Dryer
[0063] 100: Ashless coal production equipment
* * * * *