TECHNICAL FIELD
The present invention relates to a production method of reformed coal.
BACKGROUND ART
Low-grade coal (low-rank coal) with high moisture content, such as lignite
and sub-bituminous coal, has a low calorific value per unit of weight; thus, such
coal is heated so as to be dried and pyrolyzed and is also modified in a low-oxygen
atmosphere so as to reduce surface activity< As a result, the coal is converted to
reformed coal having a high calorific value per unit of weight while preventing
10 spontaneous combustion (see, for example, Patent Document l)o
It is also known that mercury can be removed in coal reformation processes
involving such pyrolysis described above through heating operation during
pyrolysis (see, for example, Patent Document 2).
15 CITATION LIST
20
Patent Literature
Patent Document 1: Japanese Unexamined Patent Application Publication
Noo 2011-37937A
Patent Document 2: US Patent Noo 5403365B
Patent Document 3: US Patent Noo 8394240B
Patent Document 4: US Patent Noo 7540384B
Non Patent Literature
Non Patent Document 1: Ro Weinstein and Ro Snoby, "Advances in dry jigging
25 improves coal quality\ p.29 to p.34, Mining Engineering, January 2007
2
5
Non Patent Document 2: William H. Pollock et al., "Lowering Costs with Dry
Coal Cleaning Technology to Meet New Environmental Requirements", p.l to p.l3,
presented at the lOth Anniversary CoalGen Conference, Pittsburgh, PA, August 10,
2010
SUMMARY OF INVENTION
Technical Problem
However, although the coal reformation process described above is capable
of obtaining reformed coal by removing mercury from the raw coal through
10 pyrolysis, there is a demand for coal having a lower mercury content.
15
The present invention has been conceived in order to solve the problem
described above, and an object of the present invention is to provide a production
method of reformed coal in which coal having a higher calorific value and lower
mercury content can be obtained.
Solution to Problem
A production method of reformed coal according to a first invention for
solving the problem described above includes: a drying step of drying coal to
obtain dried coal; a dry deashing step of removing ash from the dried coal
20 obtained in the drying step to obtain deashed dried coal; and a pyrolyzing step of
pyrolyzing the deashed dried coal obtained in the dry deashing step to obtain
deashed pyrolyzed coal.
A production method of reformed coal according to a second invention for
solving the problem described above is based on the production method of
25 reformed coal according to the first invention of the present invention and further
3
includes: a dividing step of dividing out a portion of the deashed dried coal
obtained in the dry deashing step; and a mixing step of mixing the deashed dried
coal divided out in the dividing step with the deashed pyrolyzed coal obtained in
the pyrolyzing step to obtain mixed coal.
5 A production method of reformed coal according to a third invention for
solving the problem described above is based on the production method of
reformed coal according to the first invention or the second invention. In such a
production method of reformed coal, the dry deashing step is performed using a
pulverizer that pulverizes the dried coal and a magnetic separation apparatus that
10 magnetically separates and removes the ash from the dried coal pulverized by the
pulverizer.
A production method of reformed coal according to a fourth invention for
solving the problem described above is based on the production method of
reformed coal according to the first invention or the second invention.
15 In such a production method of reformed coal, the dry deashing step is performed
using an air stream separation apparatus that, with an air stream, separates and
removes the ash from the dried coal.
A production method of reformed coal according to a fifth invention for
solving the problem described above is based on the production method of
20 reformed coal according to any one of the first to fourth inventions, in which the
coal is low-grade coal.
Advantageous Effects of Invention
In accordance with the production method of reformed coal according to the
25 present invention, it is possible to increase a calorific value of coal by drying and
4
dry deashing the coal, before pyrolyzing the coal. In addition, removing ash from
the dried coal through dry deashing before pyrolyzing the dried coal allows for the
removal of both the ash and mercury contained within the dried coal, resulting in
deashed pyrolyzed coal having a mercury content lower than that of pyrolyzed
5 coal obtained by pyrolyzing dried coal. As a result, coal having a higher calorific
value and a lower mercury content can be obtained.
Brief Description of Drawings
FIG. 1 is a process flow chart of a first embodiment of a production method
10 of reformed coal according to the present invention.
FIG. 2 is a process flow chart of a second embodiment of the production
method of reformed coal according to the present invention.
Description of Embodiments
15 Embodiments of a production method of reformed coal according to the
20
present invention will now be described with reference to the drawings. However,
the present invention is not limited to the embodiments described hereafter with
reference to the drawings.
[First Embodiment]
A first embodiment of the production method of reformed coal according to
the present invention will now be described with reference to FIG. 1.
The production method of reformed coal according to the present
embodiment includes, as illustrated in FIG. 1, a drying step S 1 of drying low-grade
coal (low-rank coal) 1 to obtain dried coal 2, a dry deashing step S2 of dry-
5
5
deashing the dried coal 2 obtained in the drying step S 1 usmg a dry deashing
apparatus to obtain deashed dried coal 3, and a pyrolyzing step S3 of pyrolyzing
the deashed dried coal 3 obtained in the dry deashing step S2 to obtain deashed
pyrolyzed coal 4.
The low-rank coal 1 is coal having a high (60 to 70%) moisture content,
such as lignite or sub-bituminous coal, which, although vast deposits thereof exist,
the coal has a low calorific value per unit of weight and is inefficient to transport.
The drying step S 1 is a step of removing water 5 from the low-rank coal 1.
In the drying step S 1, for example, feeding the low-rank coal 1 to a hot-air dryer
10 of belt conveyor type or the like and drying the low-rank coal 1 with hot air (1 00
to 280°C, preferably 150 to 200°C) produces dried coal 2 having a moisture
content of substantially 0%.
The dry deashing step S2 is a step of separating and removing, from the
dried coal 2, ash 6 contained in the dried coal 2. In the dry deashing step S2, for
15 example, feeding the dried coal 2 to a dry deashing apparatus provided with a
pulverizer that pulverizes the dried coal 2 and a magnetic separation apparatus that
magnetically separates and removes the ash 6 from the dried coal 2 pulverized by
the pulverizer, and pulverizing the dried coal 2 to, for example, a particle diameter
of 200 mesh or less and magnetically separating and removing the ash 6
20 (especially pyrite and the like having a high mercury content) produces deashed
dried coal 3 having, for example, an ash content of about 35% or less.
Alternatively, in the dry deashing step S2, for example, feeding the dried coal 2 to
the dry deashing apparatus, such as an air stream separation apparatus, allowing
the dried coal 2 to flow on a fluidized bed and supplying air thereto to separate
25 and remove the ash 6 (especially substances including high-mercury-content pyrite,
6
5
10
which are heavier than the coal) produces the deashed dried coal 3 having an ash
content of, for example, about 35% or less. In other words, the dry deashing step
S2 produces deashed dried coal 3 obtained by removing, from the dried coal 2, ash
6 along with the better part of the mercury in the dried coal 2.
The apparatus disclosed, for example, in Non Patent Document 1 can be
used as the dry deashing apparatus provided with the pulverizer and the magnetic
separation apparatus. The apparatus disclosed, for example, in Patent Document 4
or Non Patent Document 2 can be used as the dry deashing apparatus such as the
air stream separation apparatus.
The pyrolyzing step S3 is a step of removing volatile components 7 such as
tar from the deashed dried coal 3. In the pyrolyzing step S3, for example, feeding
the deashed dried coal 3 to a continuous pyrolyzer and pyrolyzing the deashed
dried coal 3 at an elevated temperature (300 to 500°C, preferably 400 to 450°C) to
separate and collect mercury contained in the deashed dried coal 3 along with the
15 volatile components 7 such as tar produces deashed pyrolyzed coal 4.
Thus, in accordance with the production method of reformed coal according
to the present embodiment, it is possible to dry, dry deash, and pyrolyze the lowrank
coal 1 to obtain deashed pyrolyzed coal 4, thereby allowing for a higher
calorific value than that of the low-rank coal 1. In addition, mercury in the low-
20 rank coal 1 can be removed in both the dry deashing step S2 and the pyrolyzing
step S3, with the mercury being physically removed along with the ash 6 in the dry
deashing step S2 before being removed along with the volatile components 7,
thereby allowing the deashed pyrolyzed coal 4 to have a lower mercury content
than that of pyrolyzed coal obtained by drying and pyrolyzing the low-rank coal 1.
7
As a result, deashed pyrolyzed coal 4 having a higher calorific value and a lower
mercury content can be obtainedo
[Second Embodiment]
A second embodiment of the production method of reformed coal according
5 to the present invention will now be described with reference to FIG. 2.
The present embodiment is constituted by the steps of the production
method of reformed coal illustrated in FIG. 1 to which a dividing step and a
mixing step are added. The rest of the steps is substantially identical to that
illustrated in FIG. 1 as described above, so the identical steps and substances will
10 be given the same reference numerals and duplicated description thereof will be
omitted as appropriate.
The production method of reformed coal according to the present
embodiment includes, as illustrated in FIG. 2, a drying step S 1 of drying low-grade
coal (low-rank coal) 1 to obtain dried coal 2, a dry deashing step S2 of dry
15 deashing the dried coal 2 obtained in the drying step S 1 using a dry deashing
apparatus to obtain deashed dried coal 3, a dividing step S 11 of dividing out a
portion of the deashed dried coal 3 obtained in the dry deashing step S2, a
pyrolyzing step S 12 of pyrolyzing deashed dried coal 3a that has not been divided
out in the dividing step S 11 to obtain deashed pyrolyzed coal 11, and a mixing step
20 S 13 of mixing the deashed pyrolyzed coal 11 obtained in the pyrolyzing step S 12
with deashed dried coal 3 b that has been divided out in the dividing step S 11 to
obtain mixed coal 120
The dividing step S 11 is a step of dividing out a portion of the deashed
dried coal 3. In the dividing step S 11, for example, feeding the deashed dried coal
8
3 to a dividing apparatus such as a conveyer belt or a screw feeder divides the
deashed dried coal 3 into the deashed dried coal 3a to be sent to the pyrolyzing
step S 12 and the deashed dried coal 3 b to be sent to the mixing step S 13. The
proportion of how the deashed dried coal 3 is divided can be adjusted according to
5 the target oxygen content or mercury content of the mixed coal 12. This is because
the oxygen content or mercury content of the deashed dried coal 3 and the deashed
pyrolyzed coal 11 can be adjusted in accordance with respective processing
conditions, and can also be determined through analysis.
The pyrolyzing step S 12 is a step, identical to the pyrolyzing step S3
10 described above, of removing volatile components 13 such as tar from the deashed
dried coal 3a. In the pyrolyzing step S 12, for example, feeding the deashed dry
coal 3a to a continuous pyrolyzer, pyrolyzing the deashed dry coal 3a at an
elevated temperature (300 to 500°C, preferably 400 to 450°C), and separating and
collecting mercury contained in the deashed dried coal 3a along with the volatile
15 components 13 such as tar, produces deashed pyrolyzed coal 11.
The mixing step S 13 is a step of mixing the deashed pyrolyzed coal 11
obtained in the pyrolyzing step S12 with the deashed dried coal 3b divided out in
the dividing step S 11. In the mixing step S 13, feeding the deashed dried coal 3b
divided out in the dividing step S 11 into a mixer along with the deashed pyrolyzed
20 coal 11 and stirring until the two are uniformly mixed produces mixed coal 12.
The mixing ratio of the deashed pyrolyzed coal 11 to the deashed dried coal
3b in the mixture are adjusted, as appropriate, according to the respective oxygen
content of the deashed pyrolyzed coal 11 and the deashed dried coal 3b, the
respective mercury contents of the deashed pyrolyzed coal 11 and the deashed
25 dried coal 3b, and the like. This is because the oxygen content and mercury
9
5
content of the deashed dried coal 3 can be obtained through the processing
condition of the dry deashing step S2 or analysis, and the oxygen content and
mercury content of the deashed pyrolyzed coal 11 can be obtained through the
processing condition of the pyrolyzing step S 12 or analysis.
Thus, in accordance with the production method of reformed coal according
to the present embodiment, it is possible to mix the deashed pyrolyzed coal 11
obtained by drying, dry deashing, and pyrolyzing the low-rank coal 1 with divided
out deashed dried coal 3b to obtain the mixed coal 12, thereby allowing for a
higher calorific value than that of the low-rank coal 1. In addition, because the
10 mixed coal 12 is a mixture of the deashed pyrolyzed coal 11 obtained by removing
mercury from the low-rank coal 1 through dry deashing and pyrolysis and the
deashed dried coal 3b obtained by removing mercury from the low-grade coal 1
through dry deashing, with the dry deashing physically removing mercury and the
pyrolysis uniformly chemically removing mercury from the entirety of the coal,
15 the mercury content of the deashed pyrolyzed coal 11 can be reduced to less than
that of pyrolyzed coal obtained by drying and pyrolyzing the low-rank coal 1. As a
result, the deashed pyrolyzed coal 11 having a higher calorific value and a lower
mercury content can be obtained. In addition, because the volume of the deashed
dried coal 3b to be mixed can be increased according to the respective oxygen
20 content and mercury content of the deashed pyrolyzed coal 11 and the deashed dry
coal 3b and the target oxygen content and mercury content of the mixed coal 12,
the yield can be increased over the production method of reformed coal according
to the first embodiment, which does not include the dividing step S 11 and the
mixing step S 13, resulting in higher productivity of the mixed coal 12.
25
10
EXAMPLES
Examples performed in order to confirm the effects of the production
method of reformed coal according to the present invention will now be described;
however, the present invention is not limited to the examples described below with
5 reference to various data.
In the present embodiment, low-rank coal having a mercury content of 69
ppm is used. The low-rank coal is dried with hot air at a temperature of, for
example, 100 to 280°C in the drying step to remove water from the low-rank coal
and obtain dried coal. As only the water has been removed from the low-rank coal,
10 the mercury content of the dried coal is 69 ppm, which is the same as the low-rank
coal.
Next, in the dry deashing step, the dried coal is pulverized to 200 mesh or
less and the ash is magnetically removed therefrom, for example, by a dry
deashing apparatus provided with a pulverizer and a magnetic separation apparatus,
15 and deashed dried coal is obtained. As a result, the ash constituting a portion of the
dried coal is removed. The ash is a substance such as pyrite having magnetic
properties, which contains more mercury than the other substances in the coal.
The mercury content of the deashed dried coal 3 is 24.2 ppm. The size of the
finely powdered ash-containing dried coal was set so as to allow 98% of the
20 calorific value of the coal to be retained while reducing mercury content by 65%.
In other words, the dry deashing step physically removes the mercury contained in
the dried coal.
Next, in the dividing step, a portion of the deashed dried coal is divided out.
The remainder of the deashed dried coal is pyrolyzed in the pyrolyzing step at an
25 elevated temperature (300 to 500°C, preferably 400 to 450°C) to obtain deashed
11
pyrolyzed coal. As a result, the mercury contained in the deashed dried coal is
volatilized along with the volatile components, and removed by 80%. The mercury
content of the deashed pyrolyzed coal is 4.83 ppm. In other words, the pyrolyzing
step chemically removes the mercury contained in the deashed dried coal.
5 Next, the deashed dried coal divided out in the dividing step and the
deashed pyrolyzed coal obtained in the pyrolyzing step are mixed to obtain mixed
coal. The divided out deashed dried coal and the deashed pyrolyzed coal obtained
in the pyrolyzing step are mixed at the ratio of, for example, 54% by weight to
46% by weight to obtain the mixed coal. The mercury content of the obtained
10 mixed coal is 13.8 ppm.
Thus, it was apparent that oxygen content and mercury content can be
adjusted by adjusting the particle size of the dried coal and the amount of ash to be
removed in the dry deashing step and the mixing ratio of deashed pyrolyzed coal
and deashed dried coal in the mixing step, thereby obtaining mixed coal having a
15 higher calorific value and a lower mercury content.
[Other Embodiments]
In the first embodiment, the production method of reformed coal in which
the low-rank coal 1 is dried, dry deashed, and pyrolyzed to obtain the deashed
pyrolyzed coal 4 has been described, but a production method of reformed coal in
20 which coal is obtained from the deashed pyrolyzed coal 4 having its surface
deactivated through a deactivating process in which the deashed pyrolyzed coal 4
is brought into contact with a specific treatment gas (oxygen-containing gas) is
also possible. In addition, a production method of reformed coal is also possible
in which, after the coal obtained by the deashed pyrolyzed coal 4 having its
12
surface deactivated through the deactivation process in which the deashed
pyrolyzed coal 4 is brought into contact with a specific treatment gas (oxygencontaining
gas), the coal is mixed with a binder such as corn starch or asphalt and
compressed (at a pressure of 1,200 kg/cm2 and a temperature of 300 to 450°C,
5 preferably 350 to 450°C) into a solid briquette such as a cylinder or a charcoal
briquette to produce formed coal.
In the second embodiment described above, the production method of
reformed coal has been described in which the deashed dried coal 3a obtained by
drying and dry deashing the low-rank coal 1 is pyrolyzed to obtain the deashed
10 pyrolyzed coal 11, a portion of the deashed dried coal 3 is divided out, and the
deashed pyrolyzed coal 11 and the divided out deashed dried coal 3b are mixed to
obtain the mixed coal 12, but a production method of reformed coal in which coal
is obtained by the mixed coal 12 having its surface deactivated through a
deactivation process in which the mixed coal 12 is brought into contact with a
15 specific treatment gas (oxygen-containing gas) is also possible. In addition, a
production method of reformed coal is also possible in which, after the coal is
obtained by the mixed coal 12 having its surface deactivated through the
deactivation process in which the mixed coal 12 is brought into contact with a
specific treatment gas (oxygen-containing gas), the coal is mixed with a binder
20 such as corn starch or asphalt and compressed (at a pressure of 1,200 kg/cm2 and a
temperature of 300 to 450°C, preferably 350 to 450°C) into a solid briquette such
as a cylinder or a charcoal briquette to produce formed coal.
13
5
Industrial Applicability
The production method of reformed coal according to the present invention
can obtain coal having a high calorific value and a lower mercury content, and
thus can be used to great advantage in industrial applications.
14
Reference Signs List
1 Low-grade coal (low-rank coal)
2 Dried coal
3 Deashed dried coal
5 3a, 3b Deashed dried coal
4 Deashed pyrolyzed coal
5 Water
6Ash
7 Volatile component
10 11 Deashed pyrolyzed coal
12 Mixed coal
13 Volatile component
S 1 Drying step
S2 Dry deashing step
15 S3 Pyrolyzing step
S 11 Dividing step
S 12 Pyrolyzing step
S 13 Mixing step

WE CLAIM:
1. A production method of reformed coal, the method comprising:
a drying step of drying coal to obtain dried coal;
a dry deashing step of removing ash from the dried coal obtained in
the drying step to obtain deashed dried coal; and
a pyrolyzing step of pyrolyzing the deashed dried coal obtained in
the dry deashing step to obtain deashed pyrolyzed coal.
The production method of reformed coal according to claim 1, further
comprising:
a dividing step of dividing out a portion of the deashed dried coal
obtained in the dry deashing step; and
a mixing step of mixing the deashed dried coal divided out in the
dividing step with the deashed pyrolyzed coal obtained in the pyrolyzing
step to obtain mixed coal.
3. The production method of reformed coal according to claim 1 or 2, wherein
the dry deashing step is performed using a pulverizer that pulverizes
the dried coal and a magnetic separation apparatus that magnetically
separates and removes the ash from the dried coal pulverized by the
pulverizer.
4. The production method of reformed coal according to claim 1 or 2, wherein
16
the dry deashing step is performed using an air stream separation
apparatus that, with an air stream, separates and removes the ash from the
dried coal.
5. The production method of reformed coal according to any one of claims 1
to 4, wherein
the coal is low-grade coal.