Note: Descriptions are shown in the official language in which they were submitted.
CA 02938960 2016-08-05
DESCRIPTION
Title of the Invention: COAL BLEND
Technical Field
[0001]
The present invention relates to a coal-blended material obtained by mixing
ashless coal that is a solvent extract of coal, and steam coal.
Background Art
[0002]
In the production of steel using a blast furnace, coke obtained by carbonizing
raw
material coal under heating is used as a reducing agent. To produce coke
having high
quality, blended coal for coke containing heavy caking coal having high caking
property as
a main raw material is necessary. However, there is a concern that the heavy
caking coal
will be difficult to be available in future and the price thereof will rise
quickly.
[0003]
In view of the above, it is required to suppress the amount of heavy caking
coal
used and reduce the cost of a coke raw material by using low rank raw
materials (non-
caking coal, weak caking coal and steam coal) as a coke raw material.
[0004]
Patent Document 1 discloses a method for producing raw material coal for
producing coke, by heating a mixed coal containing low rank coal and ashless
coal that
does not substantially contain ash components (hyper-coal) at a softening
temperature of
the ashless coal or higher. Where the raw material coal for producing coke is
used as a
coke raw material, the amount of heavy caking coal used in the production of
coke can be
suppressed.
Prior Art Document
Patent Document
[0005]
Patent Document 1: JP-A-2009-215454
Summary of the Invention
Problem that the Invention is to Solve
[0006]
When low rank raw material having low caking property is simply blended with
blended coal for coke, the caking property of the blended coal for coke is
deteriorated, and
coke strength is also deteriorated. Therefore, it is controlled in a usual
operation such that
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negative influence by the blend of low rank raw material is controlled by
increasing high
rank raw material coal blended so that the representative properties (volatile
content,
average maximum reflectance and Gieseler fluidity) required in the blended
coke for coke
fall within proper ranges. However, in this method, it is necessary to
increase the amount
of expensive heavy caking coal used with increasing the amount of low rank raw
material
used, and the cost of coke raw material cannot be reduced.
[0007]
Petroleum type caking material practically used has high compensation effect
of
caking property, but has a restriction in the amount of production.
Furthermore, it has
high sulfur content and remains in coke. Where sulfur content in iron ore and
coke is
increased, there is a problem that the residual sulfur content in molten iron
is also
increased, and as a result, the load to a desulfurization treatment process is
increased. To
avoid this problem, the upper limit is set to the sulfur content input in a
blast furnace.
Furthermore, it is known that sulfur deteriorates properties of iron. In view
of those facts,
it is considered that the limit of the amount of the petroleum type caking
material blended
with the blended coal for coke is several %. Thus, the compensation of caking
property
has the limit, and it is not easy to increase the amount of low rank raw
material blended
with the blended coal for coke.
[0008]
An object of the present invention is to provide a coal-blended material that
can
reduce the cost of coke raw material.
Means for Solving the Problems
[0009]
A coal-blended material in the present invention is obtained by mixing an
ashless
coal that is a solvent extract of a coal, and a steam coal, in a weight ratio
of from 1:1 to 1:5
without heating, in which a mixed coal after the mixing has a Gieseler
fluidity of 1.0 (Log
ddpm) or more and an average maximum reflectance of 0.75 (%) or higher.
Advantageous Effects of the Invention
[0010]
According to the coal-blended material of the present invention, the cost of
coke
raw material can be reduced.
Brief Description of the Drawing
[0011]
[FIG. 1] This is a schematic view of an ashless coal production equipment.
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Mode for Carrying Out the Invention
[0012]
A preferred embodiment of the present invention is described below by
reference
to the drawing.
[0013]
(Constitution of Coal-Blended Material)
The coal-blended material according to the embodiment of the present invention
is
obtained by mixing ashless coal in which coal is used as a raw material, and
steam coal, in
a weight ratio of from 1:1 to 1:5 without heating. The ashless coal is a
solvent extract of
coal and is one obtained by extracting a coal component that is soluble in a
solvent from a
slurry obtained by mixing and heating coal and a solvent.
[0014]
(Steam coal)
Steam coal used in the coal-blended material of the present embodiment is
bituminous coal, subbituminous coal and brown coal, classified into coal rank
of C to F2 in
Table 1. That is, the steam coal of the present embodiment is coal having a
calorific value
(dry ash free base) (kcal/kg) of 5800 or more and less than 8400.
3
[0015]
[Table 1]
Calorific value
Classification by Classification by
Classification by
Rank (Dry ash-free Fuel ratio
Classification by use
coal rank caking property cokability -
base) kcal/kg
Al 4.0 or For general and
blast furnace .
Anthracite - Non-caking coal -
A2 more sintering
1.5 or
B1 Heavy caking coal
more
__________________________________________ 8,400 or more
- Raw material coal for coke
1.5 or
Bituminous coal B2 Medium caking
coal
more
Caking coal
8,100 or more and -
2
P
less than 8,400
C
- Weak caking
coal Raw material coal for coke
0
D
7,800 or more and
0
-and PCI
-
Subbituminous less than 8,100
0
For boiler and electric power
,
coal 7,300 or more and
0
,
E -
0
less than 7,800
6,800 or more and
Fl - Non-caking coal Non-caking coal
less than 7,300
Brown coal For electric power
5,800 or more and
F2 -
less than 6,800
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= 3
[0016]
The calorific value (dry ash free base) (kcal/kg) defined in Japanese
Industrial
Standards (JIS M 1002:1978) is calculated by the following formula.
Calorific value (corrected dry ash free base)=Calorific value/(100-1.08xash
content¨water content)x100
[0017]
The fuel ratio is a value obtained by dividing fixed carbon by a volatile
content.
When steam coal is heated to high temperature in an inert gas such as
nitrogen, a side chain
part and/or bridge part of a polymer matrix constituting the steam coal are
cut by thermal
decomposition, and low boiling components such as low molecular weight
hydrocarbon,
CO, 112, and the like are generated and are discharged to the outside of steam
coal particles
in the form of a gas. Those low boiling components such as low molecular
weight
hydrocarbon, CO, H2, and the like, which are discharged to the outside of
steam coal
particles in the form of a gas, are called a volatile content (VM) of steam
coal, and the
volatile content is represented by dry-base. The fixed carbon means a non-
volatile
component of carbons contained in steam coal.
[0018]
Steam coal that is bituminous coal, subbituminous coal or brown coal and has a
calorific value (dry ash free base) (kcal/kg) of 5800 or more and less than
8400, is raw
material coal for coke and PCI (pulverized coal injection to a blast furnace),
and is coal for
boiler and electric power. Caking property thereof is inferior to that of
bituminous coal
belonging to coal rank of B1 and B2 in Table 1, that is, heavy caking coal and
medium
caking coal that are raw materials for coke.
[0019]
(Ashless coal)
The ashless coal used in the coal-blended material of the present embodiment
is
one obtained by extracting a coal component that is soluble in a solvent from
a slurry
obtained by mixing and heating coal and a solvent, and has an ash content of 5
wt% or less
and preferably 3 wt% or less. The "ash content" used herein means a residual
inorganic
material when coal has been heated at 815 C and ashed, and the inorganic
material
includes silicic acid, alumina, iron oxide, lime, magnesia, an alkali metal,
and the like.
The ashless coal is completely free from water content.
[0020]
The ashless coal is excellent in fluidity and expansibility and shows high
effect as
a caking material. Preferred ashless coal is one having maximum fluidity (log
MF)
confirmed by a Gieseler fluidity test by Gieseler plastometer method defined
in HS M8801
of 4.78 (Log ddpm) or more. Furthermore, one having a solidification
temperature
exceeding 450 C is also preferred as the ashless coal.
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= =
[0021]
Coal as a raw material of the ashless coal is not particularly limited.
Bituminous
coal having high extraction rate may be used and a lower rank coal
(subbituminous coal or
brown coal) that is less expensive may be used. Therefore, in the present
embodiment,
steam coal is used as a raw material of ashless coal. By producing ashless
coal with
steam coal as a raw material, utilization of steam coal in the production of a
coal-blended
material is expanded. Furthermore, by using steam coal as a raw material of
ashless coal,
a process of from the production of ashless coal to the production of a coal-
blended
material can be integratedly performed such that ashless coal is produced in a
production
area of steam coal and a coal-blended material is produced with the ashless
coal and the
steam coal.
[0022]
(Production Method of Ashless Coal)
A production method of ashless coal is described here. An ashless coal
production equipment 100 used in the production method of ashless coal
includes 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, and solvent separators 8
and 9, from the
upstream side of a production process, in this order, as illustrated in FIG.
1.
[0023]
The production method of ashless coal includes an extraction step, a
separation
step and an ashless coal acquirement step. Each step is described below. In
the present
embodiment, steam coal is used as a raw material of ashless coal.
[0024]
(Extraction Step)
The extraction step is a step of heating a slurry obtained by mixing coal and
a
solvent and extracting a coal component that is soluble in a solvent
(dissolving in a
solvent). This extraction step is performed in the slurry preparation tank 3,
the preheater
5 and the extraction tank 6 in FIG. 1.
[0025]
Coal as a raw material is introduced into the slurry preparation tank 3 from
the
coal hopper 1, and a solvent is introduced into the slurry preparation tank 3
from the
solvent tank 2. The coal and solvent introduced into the slurry preparation
tank 3 are
mixed by a stirrer 3a, thereby preparing a slurry containing the coal and the
solvent. The
slurry prepared in the slurry preparation tank 3 is fed to the preheater 5 by
means of the
transport pump 4, and heated to a predetermined temperature. Thereafter, the
slurry is fed
to the extraction tank 6 and maintained at a predetermined temperature while
stirring with
a stirrer 6a, thereby performing extraction. An aromatic solvent (hydrogen
donating or
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non-hydrogen donating solvent) can be preferably used as the solvent for
extracting a coal
component that is soluble in a solvent.
[0026]
(Separation Step)
The separation step is a step of separating the slurry obtained in the
extraction step
into a solution in which a coal component that is soluble in a solvent has
been dissolved
and a solid content-concentrated liquid (solvent-insoluble component-
concentrated liquid)
in which a coal component that is insoluble in a solvent (solvent-insoluble
component such
as ash component) has been concentrated, by, for example, a gravitational
settling method.
This separation step is performed in the gravitational settling tank 7 in FIG.
1. The slurry
obtained in the extraction step is separated into a supernatant liquid as a
solution and a
solid content-concentrated liquid by gravity in the gravitational settling
tank 7. The
supernatant liquid in the upper part of the gravitational settling tank 7 is
transferred to a
solvent separator 8, and the solid content-concentrated liquid settled in the
lower part of
the gravitational settling tank 7 is transferred to a solvent separator 9:
[0027]
(Ashless Coal Acquirement Step)
The ashless coal acquirement step is a step of obtaining ashless coal (HPC) by
evaporation-separating the solvent from the solution (supernatant liquid)
separated in the
separation step. This ashless coal acquirement step is performed in the
solvent separator
8 in FIG. 1. The solution separated in the gravitational settling tank 7 is
fed to the solvent
separator 8, and the solvent is evaporation-separated from the supernatant
liquid in the
solvent separator 8.
[0028]
A method for separating the solvent from the solution (supernatant liquid) can
use
a common method such as a distillation method or an evaporation method.
Ashless coal
(HPC) that does not substantially contain an ash component can be obtained by
separating
the solvent from the supernatant liquid.
[0029]
The ashless coal does not almost contain an ash component, is completely free
from water content, and shows calorific value higher than that of raw material
coal.
Furthermore, softening and melting properties (fluidity) that are particularly
important
quality as a raw material of coke for making iron are greatly improved, and
even though
raw material coal does not have softening and melting properties, the ashless
coal (HPC)
obtained have good softening and melting properties.
[0030]
The solvent is separated from the solid content-concentrated liquid separated
in
the gravitational settling tank 7, in the solvent separator 9, thereby by-
product coal in
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which solvent-insoluble components containing ash components and the like have
been
concentrated (also called RC, residual coal) can be obtained.
[0031]
(Coal-Blended Material)
The coal-blended material of the present embodiment is described below. The
low rank raw materials (non-caking coal, weak caking coal and steam coal)
including the
above -described steam coal have caking property inferior to that of heavy
caking coal and
medium caking coal that are raw material coals for coke. Therefore, in the
case where
low rank raw material is used as a coke raw material, the representative
properties (volatile
content, average maximum reflectance and Gieseler fluidity) required in a
blended coal for
coke are required to be within proper ranges by increasing blending proportion
of heavy
caking coal in the blended coal for coke. In other words, the amount of
expensive heavy
caking coal used must be increased with increasing the amount of low rank raw
materials
used in the blended coal for coke. Therefore, the cost for a coke raw material
cannot be
reduced.
[0032]
It is conducted in the coke production to compensate caking property by using
a
petroleum type caking material practically used. However, the petroleum type
caking
material has high sulfur content, remains in coke, and increases sulfur
content contained in
coke. On the other hand, the sulfur content input in a blast furnace is
limited.
Therefore, it is considered that the limit of the amount of the petroleum type
caking
material blended with the blended coal for coke is several %. For this reason,
it is not
easy to increase the amount of low rank raw materials blended with the blended
coal for
coke.
[0033]
In view of the above, the coal-blended material of the present embodiment is
obtained by mixing ashless coal and steam coal in a weight ratio of from 1:1
to 1:5 and
more preferably in a weight ratio of from 1:3 to 1:5, without heating. By
mixing the
ashless coal and steam coal in such a weight ratio without heating, Gieseler
fluidity of a
mixed coal after mixing is 1.0 (Log ddpm) or more and more preferably 1.5 (Log
ddpm) or
more. Furthermore, the average maximum reflectance of the mixed coal is 0.75
(%) or
more. Each of the Gieseler fluidity and average maximum reflectance of the
mixed coal
means a value obtained by weight-averaging numerical values of ashless coal
and steam
coal contained in the mixed coal. The Gieseler fluidity of the mixed coal is
preferably
less than 4.0 (Log ddpm) and more preferably less than 3.8 (Log ddpm). The
average
maximum reflectance of the mixed coal is preferably less than 1.2 (%) and more
preferably
lesslhan 1.0 (%). By this, the properties of the coal-blended material
obtained are
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equivalent to the properties of general heavy caking coal (general heavy
caking) or
medium caking coal belonging to ranks B to D in Table 2.
[0034]
[Table 2]
Average
Volatile Gieseler
maximum
content fluidity
Classification Rank Type reflectance
VM Ro log MF
% Log
ddpm
A LV 17-20 1.3-1.6 0.8-2.5
Heavy caking coal General heavy
20-27 1.0-1.3 1.5-4.0
caking
C High fluidity 26-33 0.8-1.0 3.0-4.0
Medium caking General
coal D medium 20-27 0.9-1.3 1.5-3.0
caking
E Medium VM About 25
About 1.0 1.0-1.5
Slightly weak
= High VM 33-38 About 0.7
1.5-2.5
caking coal
G Low VM 15-20 1.2-
1.7 2.0 or less
[0035]
Properties of general heavy caking coal (general heavy caking) or medium
caking
coal are that a volatile content is from 20 to 33 (mass %), an average maximum
reflectance
is from 0.8 to 1.3 (%) and Gieseler fluidity is from 1.5 to 4.0 (Log ddpm).
The average
maximum reflectance (%) is calculated based on the formula defined in Japanese
Industrial
Standards (JIS M 8816:1992).
[0036]
As described above, the ashless coal is excellent in fluidity and
expansibility, and
shows high effect as a caking material. For this reason, mixed coal having
caking
properties comparable to those of heavy caking coal having good quality can be
obtained
by mixing the ashless coal and steam coal without heating. When the ashless
coal and
steam coal are mixed in a weight ratio of from 1:1 to 1:5 without heating,
Gieseler fluidity
of the mixed coal after the mixing is 1.0 (Log ddpm) or more and the average
maximum
reflectance is 0.75 (%) or more. By this, a coal-blended material having
properties
equivalent to those of general heavy caking coal (general heavy caking) or
medium caking
coal can be obtained. By using the coal-blended material as a coke raw
material in place
of heavy caking coal, the amount of heavy caking coal used in the coke
production can be
reduced, and the amount of steam coal contained in a blended coal for coke can
be
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increased. Furthermore, the ashless coal has a sulfur content comparable to
that of steam
coal. Therefore, there is no limitation by sulfur content in the amount 61 the
ashless coal
blended with the blended coal for coke. As a result, by using the coal-blended
material
obtained by mixing ashless coal and steam coal without heating, as a coke raw
material,
the amount of low rank raw material that can be blended with the blended coal
for coke
can be increased. By this, the cost of a coke raw material can be reduced.
Mixing of
ashless coal and steam coal is performed without applying heat from the
outside by heating
means. There may be the case that coal itself to be blended has heat, and in
such a case,
the temperature during mixing can be about lower than 100 C, lower than 60 C
or the like.
[0037]
The ashless coal and steam coal have been coarsely ground during mixing or
before mixing. The coarse grinding used herein means grinding to obtain a
particle
diameter of 20 mm or less. The ashless coal and steam coal may be
simultaneously
introduced into a grinder and mixed without heating while coarsely grinding,
and may be
separately introduced into grinders, coarsely ground, and then introduced into
a coal mixer
so as to have an appropriate mixing ratio, followed by mixing without heating.
In the
case where the ashless coal and steam coal are simultaneously introduced into
a grinder
and are mixed while coarsely grinding, both are further uniformly mixed, and
as a result,
the ashless coal is easy to adhere to the circumference of particles of the
steam coal. In
the case of verifying a particle diameter of coal as to, for example, whether
or not the
particle diameter of coal is 20 mm or less, a screening test defined in, for
example, JIS A
1102 is used.
[0038]
The ashless coal tends to be easily ground as compared with steam coal. Finely
ground coal generally tends to cause dust generation. Furthermore, in finely
ground coal,
low temperature oxidation is generally easy to proceed. Therefore, there is a
concern of
spontaneous combustion by generation of heat by oxidation. Therefore, by
coarsely
grinding the ashless coal and steam coal, those are uniformly mixed during
mixing, and the
ashless coal adheres to the circumference of particles of the steam coal. By
this, dust
generation and low temperature oxidation are suppressed, and as a result, a
coal-blended
material can be stored and transported in a stable manner. Furthermore, by
that the
ashless coal having high caking property adheres to the circumference of
particles of the
steam coal having low caking property, the caking effect by the ashless coal
is enhanced,
and as a result, the caking property of the coal-blended material can be
increased.
[0039]
When used as a raw material coal for coke, the coal-blended material is ground
into a particle size of general blended coal for coke (the proportion of
particles having a
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particle size of 3 mm or less is about 80 wt% of the whole) by a grinder
accompanying
with a coke furnace.
[0040]
As described above, coal as a raw material of ashless coal is steam coal. By
using a coal-blended material obtained by mixing ashless coal in which steam
coal is a raw
material and steam coal without heating, as a coke raw material, the amount of
the steam
coal contained in the blended coal for coke is further increased. Therefore,
the cost of a
coke raw material can be further reduced. Furthermore, a process of from the
production
of ashless coal to the production of a coal-blended material is integratedly
performed such
that ashless coal is produced in a production area of steam coal and a coal-
blended material
is produced with the ashless coal and the steam coal, thereby transport cost
and the like can
be suppressed. As a result, the production cost can be reduced.
[0041]
In the case of integratedly performing a process of from the production of
ashless
coal to the production of a coal-blended material in the production area of
steam coal, it is
preferred that by-product coal obtained as a by-product in the production of
ashless coal is
used as a fuel of a local electric power plant or a fuel in an ashless coal
production process.
By effectively utilizing the by-product coal that is a by-product as a fuel,
the production
cost of ashless coal or even the production cost of a coal-blended material
can be
decreased.
[0042]
(Evaluation of Mixing Ratio)
Mixing ratio (weight ratio) between ashless coal and steam coal was evaluated
from properties of a coal-blended material expected in the case of mixing at
least one kind
of representative four kinds of steam coals A, B, C, and D and ashless coal
without heating.
The properties of the coal-blended material aim at the properties of heavy
caking coal
(general heavy caking) or medium caking coal (properties of ranks B to D) in
Table 2, and
were set such that Gieseler fluidity is 1.0 (Log ddpm) or more and an average
maximum
reflectance is 0.75 (%) or more.
[0043]
The ashless coal produced and steam coal were transported from a coal yard or
a
silo, simultaneously introduced into a grinder, and mixed in a state of an
ordinary
temperature (about 25 C) without heating while coarsely grinding such that a
particle size
is 20 mm or less. Alternatively, the ashless coal and steam coal were
separately
introduced into the respective grinders, and ground such that a particle size
is 20 mm or
less, and they were then introduced into a coal mixer in a proper mixing
ratio, followed by
mixing without heating. Representative analytical values (volatile content,
average
maximum reflectance and Gieseler fluidity) as raw material coal for coke,
expected in the
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case of mixing at least one kind of the representative four kinds of steam
coals A, B, C, and
D and ashless coal without heating were calculated, and the mixing ratio
satisfying the
aimed properties was evaluated. Properties of the ashless coal and four kinds
of steam
coals A, B, C, and D are shown in Table 3.
[0044]
[Table 3]
Volatile Average maximum
Gieseler
content reflectance ,
fluidity
Brand
VM Ro log MF
% % Log
ddpm _
Caking Ashless
43.2 0.9 6.0
material coal
A , 32.0 0.7 0.6
B 28.5 0.9 0.3
Steam coal
C 34.1 0.7 1.3
D 25.3 0.9 0.6
[0045]
The ashless coal and steam coal A were mixed without heating while changing
the
mixing ratio (weight ratio) by 6 stages between 1:1 and 1:20, and properties
were
evaluated. The results are shown in Table 4.
[0046]
[Table 4]
Average
VolatileGieseler
maximum
content fluidity
Mixing ratio reflectance
No. Evaluation
VM Ro log MF
Ashless Steam
%
coal coal A % Log ddpm
Invention
1 1 37.6 0.8 3.3 Good
Example
1 3 34.8 0.7 2.0 Poor
1 5 33.9 0.7 1.5 Poor
Comparative
1 8 33.2 0.7 1.2 Poor
Example 1 10 33.0 0.7 1.1 Poor
1 20 32.5 0.7 0.9 Poor
[0047]
When the mixing ratio (weight ratio) is 1:1, the average maximum reflectance
and
Gieseler fluidity were within the target ranges, but the volatile content was
higher than
33% that is the upper limit of the target range. When the mixing ratio (weight
ratio) is
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from 1:3 to 1:5, the Gieseler fluidity was within the target range, but the
volatile content
was higher than 33% that is the upper limit of the target range, and the
average maximum
reflectance was lower than 0.8% that is the lower limit of the target range.
When the
mixing ratio (weight ratio) is 1:8, the volatile content was higher than 33%
that is the upper
limit of the target range, and the average maximum reflectance and Gieseler
fluidity were
lower than the lower limits of the target ranges. When the mixing ratio
(weight ratio) is
from 1:10 to 1:20, the volatile content was within the target range, but the
average
maximum reflectance and Gieseler fluidity were lower than the lower limits of
the target
ranges. From the above, it was judged that the mixing ratio (weight ratio) of
1:1 is good.
[0048]
Next, the ashless coal and steam coal B were mixed without heating while
changing the mixing ratio (weight ratio) by 6 stages between 1:1 and 1:20, and
properties
were evaluated. The results are shown in Table 5.
[0049]
[Table 5]
Average
VolatileGieseler
maximum
Mixing ratio content fluidity
reflectance
No.
Evaluation
VM Ro log MF
Ashless Steam
Log ddpm
coal coal B
1 1 35.9 0.9 3.2 Good
Invention
1 3 32.2 0.9 1.7 Optimum
Example
1 5 31.0 0.9 1.3 Good
1 8 30.1 0.9 0.9 Poor
Comparative
1 10 29.8 0.9 0.8 Poor
Example
1 20 29.2 0.9 0.6 Poor
[0050]
When the mixing ratio (weight ratio) is 1:1, the average maximum reflectance
and
Gieseler fluidity were within the target ranges, but the volatile content was
higher than
33% that is the upper limit of the target range. When the mixing ratio (weight
ratio) is
1:3, the volatile content, average maximum reflectance and Gieseler fluidity
were all
within the target ranges. When the mixing ratio (weight ratio) is from 1:5 to
1:20, the
volatile content and average maximum reflectance were within the target
ranges, but the
Gieseler fluidity were lower than 1.5 (Log ddpm) that is the lower limit of
the target range.
However, when the mixing ratio (weight ratio) is 1:5, the Gieseler fluidity
was 1.0 (Log
ddpm) or more. From the above, it was judged that the mixing ratio (weight
ratio) of 1:3
is optimum and the mixing ratios (weight ratios) of 1:1 and 1:5 are good.
[0051]
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Next, the ashless coal and steam coal C were mixed without heating while
changing the mixing ratio (weight ratio) by 6 stages between 1:1 and 1:20, and
properties
were evaluated. The results are shown in Table 6.
[0052]
[Table 6]
Average
VolatileGieseler
maximum
Mixing ratio content fluidity
reflectance
No.
Evaluation
VM Ro log MF
Ashless Steam
Log ddpm
coal coal C
1 1 38.7 0.82 3.6 Good
Invention
1 3 36.4 0.77 2.4 Good
Example
1 5 35.6 0.75 2.1 Good
1 8 35.1 0.74 1.8 Poor
Comparative
1 10 34.9 0.74 1.7 Poor
Example
1 20 34.5 0.73 1.5 Poor
[0053]
When the mixing ratio (weight ratio) is 1:1, the average maximum reflectance
and
Gieseler fluidity were within the target ranges, but the volatile content was
higher than
33% that is the upper limit of the target range. When the mixing ratio (weight
ratio) is
from 1:3 to 1:20, the Gieseler fluidity was within the target range, but the
volatile content
was higher than 33% that is the upper limit of the target range, and the
average maximum
reflectance was lower than 0.8% that is the lower limit of the target range.
However,
when the mixing ratio (weight ratio) is 1:3 or 1:5, the average maximum
reflectance was
0.75 (%) or higher. From the above, it was judged that the mixing ratios
(weight ratios)
of from 1:1 to 1:5 are good.
[0054]
Next, the ashless coal and steam coal D were mixed without heating while
changing the mixing ratio (weight ratio) by 6 stages between 1:1 and 1:20, and
properties
were evaluated. The results are shown in Table 7.
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CA 02938960 2016-08-05
[0055]
[Table 7]
Average
VolatileGieseler
maximum
Mixing ratio content fluidity
reflectance
No.
Evaluation
VM Ro log MF
Ashless Steam
Log ddpm
coal coal D
1 1 34.3 0.9 3.3
Optimum
1 3 29.8 0.9 2.0
Optimum
Invention
1 5 28.3 0.9 1.5
Optimum
Example
1 8 27.3 0.9 1.2 Good
1 10 26.9 0.9 1.1 Good
Comparative
1 20 26.2 0.9 0.9 Poor
Example
[0056]
When the mixing ratio (weight ratio) is 1:1, the average maximum reflectance
and
Gieseler fluidity were within the target ranges, but the volatile content was
higher than
33% that is the upper limit of the target range. When the mixing ratio (weight
ratio) is
from 1:3 to 1:5, the volatile content, average maximum reflectance and
Gieseler fluidity
were all within the target ranges. When the mixing ratio (weight ratio) is
from 1:8 to
1:20, the volatile content and average maximum reflectance were within the
target ranges,
but the Gieseler fluidity was lower than 1.5 (Log ddpm) that is the lower
limit of the target
range. However, when the mixing ratio (weight ratio) is 1:8 or 1:10, the
Gieseler fluidity
was 1.0 (Log ddpm) or more. From the above, it was judged that the mixing
ratios
(weight ratios) of from 1:1 to 1:5 are optimum and the mixing ratios weight
ratios) of 1:8
and 1:10 are good.
[0057]
From the above, it was judged that the mixing ratio between ashless coal and
steam coal in which properties are equivalent to those of general heavy caking
coal
(general heavy caking) or medium caking coal is a weight ratio of from 1:1 to
1:5, and
more preferably a weight ratio of from 1:3 to 1:5.
[0058]
The above evaluation is conducted so that the weight of steam coal is larger
than
that of ashless coal. In the case where the weight of ashless coal is larger
than that of
steam coal, the Gieseler fluidity and volatile content are increased and are
excessive, and
the properties greatly deviate from the target properties. Therefore, the
effect as a coal-
blended material cannot be expected.
[0059]
CA 02938960 2016-08-05
(Effect)
As described above, in the present embodiment, a coal-blended material is
obtained by mixing ashless coal and steam coal in a weight ratio of from 1:1
to 1:5 without
heating. The ashless coal is excellent in fluidity and expansibility, and
shows high effect
as a caking material. For this reason, mixed coal having caking properties
comparable to
those of heavy caking coal having good quality can be obtained by mixing the
ashless coal
and steam coal without heating. When the ashless coal and steam coal are mixed
in a
weight ratio of from 1:1 to 1:5 without heating, Gieseler fluidity of the
mixed coal after the
mixing is 1.0 (Log ddpm) or more and the average maximum reflectance is 0.75
(%) or
more. By this, a coal-blended material having properties equivalent to those
of general
heavy caking coal or medium caking coal can be obtained. By using the coal-
blended
material as a coke raw material in place of heavy caking coal, the amount of
heavy caking
coal used in the coke production can be reduced, and the amount of steam coal
contained
in a blended coal for coke can be increased. Specifically, the amount of the
coal-blended
material blended with a blended coal for coke is suitably from 10 mass % to 50
mass %,
and preferably suitably from 20 mass % to 30 mass %, based on the whole
blended coal for
coke. In the case where ashless coal is used alone as an additive, it was
necessary to
adjust the proper amount thereof depending on properties of the blended coal.
However,
the coal-blended material of the present invention is one where proper amounts
of ashless
coal and steam coal are previously blended, and therefore, it can be easily
added to and
blended with the blended coal for coke in a proper amount. Furthermore, the
ashless coal
has a sulfur content comparable to that of steam coal. Therefore, there is no
limitation by
sulfur content in the amount of the ashless coal blended with the blended coal
for coke.
As a result, by using the coal-blended material obtained by mixing ashless
coal and steam
coal without heating, as a coke raw material, the amount of low rank raw
material that can
be blended with the blended coal for coke can be increased. By this, the cost
of a coke
raw material can be reduced.
[0060]
Ashless coal and steam coal have been coarsely ground. The ashless coal tends
to be easily ground as compared with steam coal. Finely ground coal generally
tends to
cause dust generation. Furthermore, in finely ground coal, low temperature
oxidation is
generally easy to proceed. Therefore, there is a concern of spontaneous
combustion by
generation of heat by oxidation. Therefore, by coarsely grinding ashless coal
and steam
coal, those are uniformly mixed during mixing, and the ashless coal adheres to
the
circumference of particles of steam coal. By this, dust generation and low
temperature
oxidation are suppressed, and as a result, a coal-blended material can be
stored and
transported in a stable manner. Furthermore, by that the ashless coal having
high caking
property adheres to the circumference of particles of steam coal having low
caking
16
CA 02938960 2016-08-05
property, the caking effect by the ashless coal is enhanced, and as a result,
the caking
property of the coal-blended material can be increased.
[0061]
Furthermore, coal as a raw material of ashless coal is steam coal. By using a
coal-blended material obtained by mixing ashless coal in which steam coal is a
raw
material and steam coal without heating, as a coke raw material, the amount of
the steam
coal contained in the blended coal for coke is further increased. Therefore,
the cost of a
coke raw material can be further reduced. Furthermore, a process of from the
production
of ashless coal to the production of coal-blended material is integratedly
performed such
that ashless coal is produced in a production area of steam coal and a coal-
blended material
is produced with the ashless coal and the steam coal, thereby transport cost
and the like can
be suppressed. As a result, the production cost can be reduced.
[0062]
(Modification Example of Present Embodiment)
The embodiment of the present invention is described above. However, it
merely exemplifies a specific example and does not particularly limit the
present invention,
and the design of specific constitution and the like can be appropriately
changed.
Furthermore, the action and effect described in the embodiment of the present
invention
merely enumerate the most preferred action and effect resulting from the
present invention,
and the action and effect by the present invention are not limited to those
described in the
embodiment of the present invention.
[0063]
The present application is based on a Japanese patent application filed on
March
31, 2014 (Application No. 2014-072439), the contents thereof being
incorporated herein by
reference.
Industrial Applicability
[0064]
The coal-blended material of the present invention is useful as raw material
coal
for coke production, and can be produced inexpensively.
Description of Reference Numerals
[0065]
1 Coal hopper
2 Solvent tank
3 Slurry preparation tank
3a Stirrer
4 Transport pump
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=
Preheater
6 Extraction tank
6a Stirrer
7 Gravitational settling tank
5 8, 9 Solvent separator
100 Ashless coal production equipment
18
