SPECIFICATION
TITLE OF INVENTION
METHOD FOR PRODUCING HIGH-STRENGTH COKE
5 Field of the Invention
[0001]
The present invention relates to a method of producing high-strength coke for
blast furnaces using a caking additive.
Priority is claimed on Japanese Patent Application No. 2010-40650, filed
10 February 25, 2010, the content of which is incorporated herein by reference.
Description of Related Art
[0002]
Although high-quality strongly caking coal is required to manufacture
15 high-strength coke (reducing material) necessary for operation in a blast furnace,
high-quality strongly caking coal is becoming globally depleted. Therefore, a number
of methods in which high-strength coke is manufactured using low-quality non-coking
coal or non-coking or slightly-caking coal have thus far been proposed (refer to Patent
CitationsI and 2).
20 [0003]
In a case in which low-quality coal is used as coal for coke making, in order to
maintain the strength of coke, a technique in which a caking additive is added to the coal
for coke making and then the mixture is charged in a coke oven is generally known.
Furthermore, a process in which the coal for coke making is dried and classified in a
25 fluid bed in a step prior to charging of the mixture in the coke oven is known. In this
2
case, crushed coal is classified into fine coal and coarse coal, a caking additive is added
to the fine coal, and the mixture is mixed so that the fine coal is made into grains or
granules. Furthermore, the coarse coal and the grains or granules of the fine coal are
blended and charged into a coke oven (refer to Patent Citations 1 and 3 to 6).
5 [0004]
Meanwhile, the caking additive is added only to fine coal in order to suppress
dust emission, but the caking additive may be added to coarse coal as well as fine coal in
order to improve the strength of coke.
[0005]
10 As the caking additive, for example, a coal-derived caking additive (tar, pitch, or
the like) or a petroleum-derived caking additive (solvent deasphalting pitch, heavy
residue, or the like) is used (refer to Patent Citations 7 to 10 and Non Patent Citation 1).
Particularly, the kind and amount of the caking additive have a significant influence on
the strength of the coke.
15 [0006]
The inventors studied the correlation between the kind of the caking additive
and the strength of the coke, and found that coke strength significantly improves when a
petroleum-derived heavy residue is used as a caking additive (refer to Patent Citations 10
to 13).
20 [0007]
In order to enhance the productivity of a blast furnace, it is necessary to further
enhance the strength of the coke, and the caking additive plays an important role in a
current condition in which a large amount of low-quality coal should be used as the coal
for coke making.
25 [0008]
3
Based on the above finding, the inventors proposed a liquid caking additive
having a petroleum-derived solid caking additive dissolved in a coal-derived liquid
caking additive (refer to Patent Citation 14). When the liquid caking additive is used,
the dissolved petroleum-derived caking additive can easily permeate between coal
5 particles, and therefore the swelling pressure of the coal during carbonization is
suppressed, and coke strength improves.
Patent Citation
[0009]
10 [Patent Citation 1] Japanese Unexamined Patent Application, First Publication
No. 2003-226879
[Patent Citation 2] Japanese Unexamined Patent Application, First Publication
No. 2007-002052
[Patent Citation 3] Japanese Unexamined Patent Application, First Publication
15 No. 2006-283008
[Patent Citation 4] Japanese Unexamined Patent Application, First Publication
No. H10-183136
[Patent Citation 5] Japanese Unexamined Patent Application , First Publication
No. H11-116970
20 [Patent Citation 6] Japanese Unexamined Patent Application, First Publication
No. 2001-072982
[Patent Citation 7] Japanese Unexamined Patent Application, First Publication
No. S48-071401
[Patent Citation 8] Japanese Unexamined Patent Application, First Publication
25 No. S59-179586
4
[Patent Citation 9] Japanese Unexamined Patent Application, First Publication
No. H09-241653
[Patent Citation 10] Japanese Unexamined Patent Application, First
Publication No. 2006-291190
5 [Patent Citation 11] Japanese Unexamined Patent Application, First
Publication No. 2007-009016
[Patent Citation 12] Japanese Unexamined Patent Application, First
Publication No. 2007-009030
[Patent Citation 13] Japanese Unexamined Patent Application, First
10 Publication No. 2007-321076
[Patent Citation 14] Pamphlet of International Publication WO 2010/073535
[0010]
Non Patent Citation
[Non Patent Citation 1] Coal Chemistry and Industry (Sankyo Publishing Co.,
15 Ltd. 1977, p.315)
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0011]
20 As described above, when the liquid caking additive proposed by the inventors
(coal-derived liquid caking additive + petroleum-derived solid caking additive) (refer to
Patent Citation 14) is used, the dissolved petroleum-derived caking additive permeates
between coal particles, the swelling pressure of the coal during carbonization is
suppressed, and coke strength improves. However, since there is a limitation on the
25 amount of the petroleum-derived solid caking additive that can be dissolved in the
5
coal-derived liquid caking additive, there is also a limitation on the degree of
improvement in the strength of the coke.
[0012]
Therefore, an object of the present invention is to produce high-strength coke
5 through an aspect of a combination use in which coke strength further improves in a case
in which several kinds of caking additives having different characteristics are used in
combination.
Methods for Solving the Problem
10 [0013]
The inventors considered that, in order to solve the above problem, it is
important to understand the interaction (weight loss during co-carbonization) of a variety
of caking additives (from petroleum (petroleum-derived) and from coal (coal-derived))
and coal in a carbonization process, and thoroughly investigated the interaction. As a
15 result, it was determined that, when a coal-derived caking additive and a
petroleum-derived caking additive are made to coexist in coal for coke making and the
coal is carbonized, the interaction occurs in the carbonization process, and coke strength
further improves.
[0014]
20 The present invention is based on the above finding, and therefore the purport
thereof is as follows.
[0015]
(1) A method of producing high-strength coke according to a first aspect of the
present invention including carbonizing a coal feed including a first caking additive
25 whose maximum weight loss temperature is 400°C or higher and a second caking
6
additive whose maximum weight loss temperature is lower than 400°C in a coal for coke
making, the maximum weight loss temperature being defined as the temperature at which
the weight loss rate obtained through first derivative of weight loss with respect to time
during heating up to 900°C at 3 °C/min becomes the maximum.
5 [0016]
(2) In the method of producing high-strength coke according to the above (1),
the difference between the maximum weight loss temperature of the first caking additive
and the maximum weight loss temperature of the second caking additive may be 50°C or
more.
10 [0017]
(3) In the method of producing high-strength coke according to the above (1) or
(2), the total amount of the first caking additive and the second caking additive may be
0.2 mass% or more.
[0018]
15 (4) In the method of producing high-strength coke according to the above (1) or
(2), the ratio of the first caking additive to the total amount of the first caking; additive
and the second caking additive may be 0.1 to 0.9 in terms of mass ratio.
[0019]
(5) In the method of producing high-strength coke according to the above (1) or
20 (2), a plurality of the first caking additives may be included in the coal for coke making.
[0020]
(6) In the method of producing high-strength coke according to the above (1) or
(2), a plurality of the second caking additives may be included in the coal for coke
making.
25 [0021]
7
(7) In the method of producing high-strength coke according to the above (1) or
(2), the first caking additive may be a petroleum-derived caking additive.
[0022]
(8) In the method of producing high-strength coke according to the above (1) or
5 (2), the second caking additive may be a coal-derived caking additive.
Effects of the Invention
[0023]
According to the present invention, it is possible to produce high-strength coke
10 having a coke strength that is equivalent to or higher than a coke strength obtained by
mixing a single caking additive and coal for coke making.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024]
15 FIG. 1 is a view showing the weight loss curves of a variety of coals.
FIG. 2 is a view showing the weight loss curves of a variety of caking additives.
FIG. 3 is a view showing the weight loss curve of a sample in which coal E and a
coal-derived caking additive C2 are mixed at a weight ratio of 1:1.
FIG. 4 is a view showing the weight loss curve of a sample in which coal H and
20 the coal-derived caking additive C2 are mixed at a weight ratio of 1:1.
FIG 5 is a view showing the weight loss curve of a sample in which the coal E
and a coal-derived caking additive C3 are mixed at a weight ratio of 1:1.
FIG 6 is a view showing the weight loss curve of a sample in which the coal H
and the coal-derived caking additive C3 are mixed at a weight ratio of 1:1.
25 FIG. 7 is a view showing the weight loss curve of a sample in which the coal E
8
and a coal-derived caking additive Cl are mixed at a weight ratio of 1:1.
FIG 8 is a view showing the weight loss curve of a sample in which the coal H
and the coal-derived caking additive Cl are mixed at a weight ratio of 1:1.
FIG 9 is a view showing the weight loss curve of a sample in which the coal E
5 and a coal-derived caking additive C4 are mixed at a weight ratio of 1:1.
FIG. 10 is a view showing the weight loss curve of a sample in which the coal H
and the coal-derived caking additive C4 are mixed at a weight ratio of 1:1.
FIG 11 is a view showing the weight loss curve of a sample in which the coal E
and a coal-derived caking additive C5 are mixed at a weight ratio of 1:1.
10 FIG. 12 is a view showing the weight loss curve of a sample in which the coal H
and the coal-derived caking additive C5 are mixed at a weight ratio of 1:1.
FIG 13 is a view showing the weight loss curve of a sample in which the coal E
and a petroleum-derived caking additive P2 are mixed at a weight ratio of 1:1.
FIG. 14 is a view showing the weight loss curve of a sample in which the coal H
15 and the petroleum-derived caking additive P2 are mixed at a weight ratio of 1:1.
FIG 15 is a view showing the weight loss curve of a sample in which the
coal-derived caking additive Cl and a petroleum-derived caking additive PI are mixed at
a weight ratio of 1:1.
FIG. 16 is a view showing the weight loss curve of a sample in which the
20 coal-derived caking additive C3 and the petroleum-derived caking additive P1 are mixed
at a weight ratio of 1:1.
FIG 17 is a view showing the weight loss curve of a sample in which the
coal-derived caking additive Cl and a petroleum-derived caking additive P2 are mixed at
a weight ratio of 1:1.
25 FIG. 18 is a view showing the weight loss curve of a sample in which the
9
coal-derived caking additive C3 and the petroleum-derived caking additive P2 are mixed
at a weight ratio of 1:1.
FIG. 19 is a view showing the weight loss curve of a sample in which the coal E,
the coal-derived caking additive Cl, and the petroleum-derived caking additive P2 are
5 mixed at a weight ratio of 2:1:1.
FIG. 20 is a view showing the weight loss curve of a sample in which the coal E,
the coal-derived calling additive Cl, and the petroleum-derived caking additive Pl are
mixed at a weight ratio of 2:1:1.
FIG. 21 shows the relationship between H/C and Tmay (°C) of a coal-derived
10 caking additive and a petroleum-derived caking additive.
FIG. 22 is a view showing the relationship between the mixture ratio of the
petroleum-derived caking additive P2 in a caking additive (mixture ratio of P2) and the
coke strength DI15015 (-) in a case in which coke is manufactured by making the
coal-derived caking additive Cl and the petroleum-derived caking additive P2 coexist in
15 coal for coke making.
FIG. 23 is a view showing the relationship between the mixture ratio of P2 and
the coke strength DI15015 (-) in a case in which coke is manufactured by making the
coal-derived caking additive C3 and the petroleum-derived caking additive P2 coexist in
coal for coke making.
20 FIG. 24 is a view showing the relationship between the mixture ratio of the
petroleum-derived caking additive P1 in a caking additive (mixture ratio of P1) and the
coke strength DI15015 (-) in a case in which coke is manufactured by making the
coal-derived caking additive C3 and the petroleum-derived caking additive P1 coexist in
coal for coke making.
25
10
DETAILED DESCRIPTION OF THE INVENTION
[0025]
The present invention will be described in detail. Firstly, tests carried out to
clearly understand the interaction (weight loss during co-carbonization) between a
5 variety of (petroleum-derived and coal-derived) caking additives and coal in a
carbonization process and results thereof will be described.
[0026]
1) Interaction between coal-derived caking additive and coal
(1) Table 1 shows the properties of coals used in the tests. Table 2 shows the
10 properties of caking additives used in the tests.
[0027]
[Table 1]
N
Proximate
Analysis
Ultimate Analysis
(mass%, daf)
Gieseler
Plastometry
Ruhr
Dilatometry
Petrographic
Analysis
Coal
Ash VM C N
0
(sift)
Logio (Max.
Fluidity/ddpm)
Total
Dilatation
(%)
Mean Vit.
Ref.
(%)
Total
Inerts
(voL%)
9.5 17.8 83.8 4.4 0.9 1.3 0.93 31 15.3 1.55
B ! 10.3 19.8 81.3 4.5 1 1.6 2.3 1.93 36 33.7 1.36
C 10.3 22.7 80.5 4.4 1 1.2 3.2 1.79 34 28.3 1.31
D 10.5 20.7 81.3 4.7 1 1.8 1.7 2.62 122 24.5 1.35
E 8.6 24.3 82.1 4.9 1 1.8 2.5 3.03 153 32.5 1.20
F 9.0 25.4 81.1 4.7 1.3 3.3 2.30 80 22.0 1.27
9.2 30.5 78.9 5.0 1.7 4.8 2.32 14 27.2 0.85
9.2 36.4 76.7 5.3 1.8 6.4 2.56 44 20.1 0.74
I 9.2 38.7 77.3 5.6 1.8 5.7 3.74 108 17.7 0.72
*VM : Volatile Matter
00N
Type From coal
Name Cl C2 C3 C4 C5
Industrial VM 97.0 73.2 71.8 55.5 59.0
analysis (d.%) Ash 0.1 0.0 0.4 0.2 0.5
TS 0.4 0.4 0.5 0.4 0.5
Ultimate C 92.7 91.7 91.5 94.3 94.0
analysis H 5.6 5.0 5.2 4.4 4.5
(d.%) N 1.0 0.8 1.1 0.9 1.0
0 An 1.6 1.4 0.4 0.1
H/C (-) 0.719 0.652 0.684 0.554 0.575
HI 4.2 38.9 55.6 83.5 70.6
Solvent TI 0.0 11.2 9.3 39.8 22.0
fractionation QI 0.0 7.6 5.1 31.0 5.3
(%) R (TIQS) 0.0 3.6 4.2 8.9 16.7
y (HITS) 4.2 27.7 46.3 43.7 48.6
Softening point (°C) 38 83
*VM : Volatile Matter
Pi
40.9
0.2
5.4
86.2
5.8
1.4
1.0
0.807
73.5
45.1
19.8
25.3
28.4
242
7.5
83.3
8.2
0.3
0.5
1.182
68.6
0.0
ti
13
each of a variety of caking additives) were heated up to 900°C at 3 °C /min in a nitrogen
atmosphere, and a change in the weight (mass) of the sample over time was measured
using a thermobalance . The measurement results (weight loss curve) are shown in FIG.
2.
5 [0030]
As shown in FIG. 1, generally, the thermoplastic temperature range of coal is
400°C to 500°C. However, it was found from FIG. 2 that, in coal -derived caking
additives which are effective for improvement in the coke strength (the coal-derived
caking additives Cl, C2, C3, C4, and C5 in FIG. 2), the weight significantly decreases
10 before the temperature reaches 400°C at which the coal begins to soften and melt (for
example, the coal-derived caking additive C2 : 74%, the coal -derived caking additive
C3 : 72%), and the weight loss in the thermoplastic temperature range of coal at 400°C to
500°C is merely approximately 5%.
[0031]
15 In the coal -derived caking additive Cl having an action of improving calving
properties , thermal decomposition is completed at approximately 350°C. Meanwhile, in
the petroleum-derived caking additives (petroleum-derived caking additives P1 and P2 in
FIG. 2), the weight significantly decreases at 400°C to 500°C which is the thermoplastic
temperature range of the coal.
20 [0032]
Meanwhile, with regard to improvement in the calving properties of coal, the
following two mechanisms (i) and (ii) can be considered.
(i) The coal-derived caking additive thermally decomposes at 400°C to 500°C
(the thermoplastic temperature range of the coal) so as to discharge an extremely small
14
amount of the minor components, and the minor components contribute to improvement
in the caking properties of the coal.
(ii) In a process in which the coal-derived casting additive and coal are heated (a
co-carbonization process), the coal-derived caking additive and the coal interact with
5 each other, and, consequently, the coal is reformed so that the caking properties improve.
According to the above test results, it is considered that the caking properties
improve due to the mechanism (ii) rather than the mechanism (i).
[0033]
(2) In order to understand the interaction between the coal-derived caking
10 additive and the coal, the inventors heated 20 mg of a sample in which one kind of coal
and one hind of caking additive were mixed in a weight ratio of 1:1 up to 900°C at 3
°C/min in a nitrogen atmosphere, and measured a change in the weight (reduction) of the
sample over time using a thermobalance. Meanwhile , since coal E or coal H were used
as the coal , and any of the coal-derived caking additives Cl to C5 were used as the
15 coal-derived caking additive, 10 samples were prepared.
[0034]
In the past, the weight loss in the co-carbonization process of the coal and the
caking additive was measured using a mixture in which the caking additive was added to
the coal at a mixture ratio of 3% to 5% which is substantially the same mixture ratio as in
20 an actual machine. However, since the mixture ratio of the caking additive is small, it is
not always possible to precisely evaluate the interaction between the coal and the caking
additive due to weighing error.
[0035]
The inventors measured the weight loss in the co-carbonization process of the
25 coal and the caking additive using a mixture in which the coal and the caking additive
15
were mixed in a weight ratio of approximately 1:1 as a sample. The measurement
results (weight loss curves) are shown in FIGS. 3 to 12. Meanwhile, FIGS. 3 to 12 also
show the measurement results for the single coal and the single caking additive each.
[0036]
5 FIGS. 3 and 4 are results obtained when the coal-derived caking additive C2 was
used. FIGS. 5 and 6 are results obtained when the coal-derived caking additive C3 was
used. FIGS. 7 and 8 are results obtained when the coal-derived caking additive Cl was
used. FIGS. 9 and 10 are results obtained when the coal-derived caking additive C4
was used. FIGS. 11 and 12 are results obtained when the coal-derived caking additive
10 C5 was used.
[0037]
As shown in FIGS. 3 to 12, the actual measurement values (indicated by
"measured") of the weight loss of the mixtures of the coal-derived caking additives Cl to
C5 and the coal in the co-carbonization process were larger than the calculated values
15 (indicated by "talc.") of the weight loss in a temperature range of 200°C to 450°C. The
calculated value of the weight loss is a weighted average value of weight loss in a case in
which the test was carried out using coal alone and weight loss in a case in which the test
was carried out using the caking additive alone, which does not consider the interaction
between the coal and the caking additive (interaction between different materials).
20 From the above facts, it is found that the coal-derived caking additive causes a strong
interaction with the coal in a temperature range from a temperature at which the coal
does not begin to soften and melt yet to a temperature of the initial stage in which the
coal softens and melts.
[0038]
25 Meanwhile, compared to the coal H, in the coal E having favorable caking
1 6
properties (the maximum fluidity (Max. Fluidity) and Total Dilatation in Table 1), there is
a large difference between the actual measurement value and the calculated value. The
above fact means that coal having favorable caking properties causes a strong interaction
with a caking additive.
5 [0039]
2) Interaction between petroleum-derived caking additive and coal
Next, in order to understand the interaction between the petroleum-derived
caking additive and the coal, the inventors heated 20 mg of a sample in which the coal
(coal E or coal H) and the petroleum-derived caking additive P2 were mixed in a weight
10 ratio of 1:1 tip to 900°C at 3 °C/min in a nitrogen atmosphere, and measured a change in
the weight over time using a thermobalance. The measurement results (weight loss
curve) are shown in FIGS. 13 and 14. Meanwhile, FIGS. 13 and 14 also show the
measurement results for the single coal and the single caking additive each.
[0040]
15 From FIGS. 13 and 14, it is found that there is little interaction between the
petroleum-derived caking additive P2 and the coal in a temperature range of lower than
400°C, and the weight loss of the sample is large at 400°C to 500°C which is the
thermoplastic temperature range of the coal. The above fact means that, in the process
in which the coal softens and melts, the petroleum-derived caking additive P2 acts
20 directly on the coal or acts as a gas-forming material so as to contribute to improvement
in the caking properties of the coal.
[0041]
The inventors found the following facts from the above experiment results.
[0042]
25 (x) The actual measurement value of the weight loss during the co-carbonization
17
of the coal-derived caking additive and a coal mixture becomes larger than the calculated
value in a temperature range of 200°C to 450°C, The above fact means that the
interaction between the coal-derived caking additive and the coal occurs in a temperature
range from a temperature at which the coal does not begin to soften and melt yet to a
5 temperature of the initial stage in which the coal softens and melts.
[0043]
(y) While there is little interaction between the petroleum-derived caking
additive and the coal in a temperature range of lower than 400°C, the petroleum-derived
caking additive has some sort of action on the coal at 400°C to 500°C which is the
10 thermoplastic temperature range of the coal. The above fact means that the interaction
between the petroleum-derived caking additive and the coal occurs in a temperature
range after the beginning of softening and melting of the coal.
[0044]
(z) When the temperature at which the coal begins to soften and melt is assumed
15 to be 400°C, the caking additives can be classified into (zl) a coal-derived caking
additive that interacts with the coal in a temperature range of lower than 400°C, and (z2)
a petroleum-derived caking additive that strongly interacts with the coal in a temperature
range of 400°C or higher and does not interact with the coal in a temperature range of
lower than 400°C.
20 [0045]
Based on the above finding, the inventors considered that, when a coal-derived
caking additive and a petroleum-derived caking additive are used in combination, the
interactions by both caking additives overlap, and the coke strength further improves, and
carried out the following test.
18
[0046]
Firstly, a change in the weight of the caking additive (mixed caking additive) in
which the coal-derived caking additive and the petroleum-derived caking additive were
mixed over time (weight loss) in the co-carbonization process was measured in the
5 following manner.
[0047]
20 mg of a sample in which the coal-derived caking additive Cl or C3 and the
petroleum-derived caking additive P1 or P2 were mixed in a weight ratio of 1:1 was
heated up to 900°C at 3 °C/min in a nitrogen atmosphere, and a change in the weight of
10 the sample over time (weight loss) was measured using a thermobalance. The
measurement results (weight loss curve) are shown in FIGS. 15 to 18. Meanwhile,
FIGS. 15 to 18 also show changes in weights over time for the single coal and the single
caking additive each.
[0048]
15 From FIGS. 15 to 18, it is found that the actual measurement value (indicated by
"measured") of the weight loss of the mixture of the coal-derived caking additives and
the petroleum-derived caking additive in the co-carbonization process was larger than the
calculated value (indicated by "calc.") of the weight loss in a temperature range of 200°C
to 450°C.
20 [0049]
The above fact means that the caking additive (mixed caking additive) in which
the coal-derived caking additive and the petroleum-derived caking additive that does not
interact with the coal before softening and melting of the coal are mixed strongly
interacts with the coal in a temperature range from a temperature at which the coal does
25 not begin to soften and melt yet to a temperature of the initial stage in which the coal
19
softens and melts.
[0050]
That is, it is possible to explain that, in the co-carbonization process of the
mixed caking additive, the coal-derived caking additive and the petroleum-derived
5 caking additive interact with the coal at the same time, and an effect that is stronger than
the overlap effect of the effects of both materials is exhibited.
[0051]
The inventors carried out tests that confirm the synergy effect of the mixed
caking additive of the coal-derived caking additive and the petroleum-derived caking
10 additive in the following manner.
[0052]
A sample in which the coal E, the coal-derived caking additive C 1, and the
petroleum-derived caking additive P2 were mixed in a weight ratio of 2:1:1 and a sample
in which the coal E, the coal-derived caking additive C 1, and the petroleum-derived
15 caking additive P 1 were similarly mixed in a weight ratio of 2:1:1 were prepared. 20
mg of each of the samples was heated up to 900°C at 3 °C/min in a nitrogen atmosphere,
and a change in the weight of the sample over time (weight loss) was measured using a
thermobalance. The measurement results (weight loss curve) are shown in FIGS. 19
and 20. Meanwhile, FIGS. 19 and 20 also show the weight loss of the single coal and a
20 change (weight loss) in the weight of the single mixed caking additive over time.
[0053]
From FIGS. 19 and 20, it is found that, in the samples in which the coal E, the
coal-derived caking additive Cl, and the petroleum-, derived caking additives P1 and P2
were mixed, the actual measurement value of the weight loss during co-carbonization
25 (indicated by "measured") was larger than the calculated value of the weight loss
20
obtained from the actual measurement value of the weight loss of each of the three
materials (indicated by "vale.").
[0054]
Finally, it is found from FIGS. 19 and 20 that, by the co-carbonization of the
5 mixture in which a coal is mixed with a coal-derived caking additive that interacts with
coal at lower than 400°C and a petroleum-derived caking additive that does not interact
with coal at lower than 400°C and interacts with coal at 400°C or higher, a strong
synergetic interaction of the three kinds of raw materials (coal and two kinds of caking
additives) is exhibited in a temperature range (200°C to 400°C) from a temperature at
10 which the coal does not begin to soften and melt yet to a temperature of the initial stage
in which the coal softens and melts during the co-carbonization, a swelling pressure is
further suppressed during carbonization, and the coke strength significantly improves,
which provides a foundation for the present invention.
[0055]
15 Thus far, the caking additive has been classified into coal-derived one and
petroleum-derived one based on the source material, but the parameter that specifically
indicates a chemical phenomenon termed the interaction with coal is a change (reduction)
in the weight over time of the caking additive in the co-carbonization process.
[0056]
20 For a variety of caking additives, a change (reduction) in the weight of a sample
having a predetermined weight (5 mg to 20 mg) over time was measured using a
thermobalance when the sample was heated up to 900°C at 3 °C/min in nitrogen. In the
present invention, in a weight loss rate curve obtained through the first derivative of a
weight loss curve with respective to time, the temperature at which the weight loss rate
21
becomes the maximum is defined as the maximum weight loss temperature (Tmyx (°C)),
and the caking additive is classified using the Tmae (°C). The reasons are as follows.
[0057]
FIG 21 shows the relationship between H/C (the atom number ratio of hydrogen
5 to carbon) and Tmex (°C) (maximum weight loss temperature) of a coal-derived caking
additive and apetroleum-derived caking additive. In FIG. 21, the closed squares
indicate coal-derived caking additives, and open squares indicate petroleum-derived
caking additives. It is found from FIG. 21 that the caking additives are clearly
demarcated at 400°C as a boundary temperature. Meanwhile, the H/C of the
10 petroletiun-derived caking additives having a T,,,ax (°C) of 400°C or higher, which is used
in FIG. 21, is less than 2, and the H/C of the coal-derived caking additives having a Tmax
(°C) of lower than 400°C is less than 1.
[0058]
Here, the basic concept of the present invention is that coal for coke making in
15 which a caking additive having a maximum weight loss temperature of 400°C or higher
(a first caking additive) and a caking additive having a maximum weight loss
temperature of lower than 400°C (a second caking additive) coexist is carbonized.
[0059]
In the present invention, it is important that the caking additive having a
20 maximum weight loss temperature of 400°C or higher and the caking additive having a
maximum weight loss temperature of lower than 400°C coexist in the coal for coke
making, and the coexistence form of the caking additives is not particularly limited.
[0060]
The caking additive having a maximum weight loss temperature of 400°C or
22
higher and the caking additive having a maximum weight loss temperature of lower than
400°C may be sequentially mixed with the coal. In addition, the coal, the caking
additive having a maximum weight loss temperature of 400°C or higher, and the caking
additive having a maximum weight loss temperature of lower than 400°C may be mixed
5 at the same time.
[0061]
In addition, the caking additive having a maximum weight loss temperature of
400°C or higher and the caking additive having a maximum weight loss temperature of
lower than 400°C are mixed so as to manufacture a mixed caking additive, and the mixed
10 caking additive may be mixed with the coal.
[0062]
The inventors carried out the following tests in order to confirm the effect
(improvement in the coke strength) of the present invention.
[0063]
15 (Test 1)
3% of the following caking additives (caking additives a or b) were incorporated
into coal for coke making, 85% of which was composed of 3 mm or smaller (-3 mm)
particles_and which was composed of 50% of coal C and 50% of coal H (refer to Table 1),
the obtained mixture is carbonized at a bulk density of 0.85 so as to manufacture coke,
20 and a coke strength DI15015 (-) (hereinafter also expressed by DI) was measured.
[0064]
The caking additive a (Cl-P2 mixture) was a caking additive in which the
coal-derived caking additive Cl and the petroleum-derived caking additive P2 were
mixed. In addition, the caking additive b (C3-P2 mixture) was a caking additive in
23
which the coal-derived caking additive C3 and the petroleum-derived caking additive P2
were mixed. A crushed product 100% of which was composed of -3 mm particles was
used as the caking additive.
[0065]
5 The measurement results are shown in FIGS. 22 and 23. The vertical axis
indicates the difference (increase in DI) between the DI of coke manufactured by adding
the caking additive to the coal and the DI of coke manufactured by not adding the caking
additive to the coal. FIGS. 22 and 23 also show the increase in DI of the coke strength
in a case in which the coal-derived caking additives Cl and C3 and the
10 petroleum-derived calling additive P2 each was blended as single caking additive.
[0066]
It is found from FIGS. 22 and 23 that, when 3% of the caking additive was
incorporated into a coal for coke making and the coal was carbonized, the coke strength
significantly improved.
15 [0067]
(Test 2)
3% of the following caking additive c was incorporated into coal for coke
making, 85% of which was composed of -3 mm particles and'which was composed of
50% of coal C and 50% of coal H (refer to Table 1), the obtained mixture was carbonized
20 at a bulk density of 0.85 so as to manufacture coke, and a coke strength DI1S015 (-) was
measured.
The caking additive c (C3-P 1 mixture) was a caking additive in which the
coal-derived caking additive C3 and the petroleum-derived caking additive P1 were
mixed.
25 [0068]
24
The measurement results are shown in FIG. 24. The vertical axis indicates the
difference (increase in DI) between the DI of coke manufactured by adding the caking
additive to the coal and the DI of coke manufactured by not adding the caking additive to
the coal. FIG. 24 also shows the increase in DI of the coke strength in a case in which
5 the coal-derived caking additive C3 and the petroleum-derived caking additive P1 each
was blended as single caking additive.
[0069]
It is found from FIG. 24 that, when 3% of the calving additive was incorporated
into coal for coke making and the coal was carbonized, the coke strength significantly
10 improved.
[0070]
Therefore, in a method of producing high-strength coke according to an
embodiment of the present invention, a coal feed including a caking additive (first caking
additive) whose maximum weight loss temperature is 400°C or higher and a caking
15 additive (second caking additive) whose maximum weight loss temperature is lower than
400°C in coal for coke making is carbonized. Meanwhile, as described above, a
temperature at which the weight loss rate (weight loss rate in a weight loss rate curve)
obtained through the first derivative of weight loss (weight loss curve) with respective to
time when the sample (caking additive) is heated up to 900°C at 3 °C/min becomes the
20 maximum is defined as the maximum weight loss temperature.
Next, a preferable embodiment of the present invention will be described.
[0071]
When the caking additive whose maximum weight loss temperature is 400°C or
higher and the caking additive whose maximum weight loss temperature is lower than
25
400°C are used, the coke strength synergistically improves even in a case in which the
maximum weight loss temperatures of the two kinds of caking additives are close to each
other. However, basically, since the caking additive whose maximum weight loss
temperature is 400°C or higher and the caking additive whose maximum weight loss
5 temperature is lower than 400°C have different characteristics, the difference AT between
the maximum weight loss temperatures of the caking additives is preferably 50°C or
higher in a case in which the coke strength is significantly increased. Meanwhile, the
upper limit of the difference AT between the maximum weight loss temperatures is not
particularly limited, and may be, for example, 300°C in consideration of the
10 characteristics of the caking additive. Here, in a case in which the maximum weight
loss temperature of the caking additive whose maximum weight loss temperature is
400°C or higher is defined as Tpmax, and the maximum weight loss temperature of the
caking additive whose maximum weight loss temperature is lower than 400°C is defined
as T°max, the difference AT between the maximum weight loss temperatures can be
15 expressed by the following equation (1).
AT = TpmaTeinax ... (1)
[0072]
A plurality of (plural kinds of) caking additives whose maximum weight loss
temperature is 400°C or higher may be blended into coal for coke making. In addition,
20 a plurality of (plural kinds of) caking additives whose maximum weight loss temperature
is lower than 400°C may be blended into coal for coke making.
[0073]
The caking additive (first caking additive) whose maximum weight loss
temperature is 400°C or higher and the caking additive (second caking additive) whose
26
maximum weight loss temperature is lower than 400°C are preferably included in coal
for coke making in a total amount of 0.2 mass% or more. When the total amount of the
caking additive is less than 0.2 mass%, the interaction of the caking additives is small.
When the total amount of the caking additive in the entire coal feed is 0.2 mass% or more,
5 a synergistic improvement in the coke strength can be sufficiently expected.
[0074]
It is not necessary to particularly limit the upper limit of the total amount of the
caking additive in terms of improvement in the coke strength. However, currently,
when the ratio of the caking additive is too high, there are cases in which operational and
10 industrial problems, such as (a) an increase in the amount of carbon attached to a
chamber wall in a coke oven and (b) a decrease in the coke yield, occur. Therefore, the
upper limit of the total amount of the caking additive is preferably 10%.
[0075]
The amount of the caking additive whose maximum weight loss temperature is
15 400°C or higher and the amount of the caking additive whose maximum weight loss
temperature is lower than 400°C are preferably 1:9 to 9:1 in terms of mass ratio. That is,
the ratio of the caking additive whose maximum weight loss temperature is 400°C or
higher in the total amount of the caking additive is preferably 0.1 to 0.9 in terms of mass
ratio.
20 In addition, in order to sufficiently exhibit the caking properties of the caking
additive, the H/C of the caking additive whose maximum weight loss temperature is
400°C or higher is preferably more than 0 to less than 2, and the H/C of the caking
additive whose maximum weight loss temperature is lower than 400°C is preferably
more than 0 to less than 1.
27
Examples
[0076]
Next, examples of the present invention will be described. The conditions in
the examples are one example of conditions which are employed to confirm the
5 feasibility and effect of the present invention, and the present invention is not limited to
the example conditions. The present invention can employ a variety of conditions
within the scope of the purport of the present invention as long as the object of the
present invention is achieved.
[0077]
10 (Examples)
Coal feeds satisfying the conditions shown in Table 3 (coal for coke making and
caking additive) were heated in a furnace at a furnace temperature of 1250°C for 18.5
hours of carbonization time so as to manufacture coke, and the coke strength DI15015 (-)
was measured according to JIS K 2151. The measurement results are shown in Table 3.
15 It is found that the coke strength DI15o15 (-) of the examples was significantly high
compared to the coke strength DI15015 (-) of comparative examples (comparison between
comparative examples 1 and 2 and examples 1 to 3, comparison between comparative
examples 3 and 4 and examples 4 to 6, comparison between comparative examples 5 and
6 and examples 7 to 9, comparison between comparative examples 7 and 8 and examples
20 10 to 14, and comparison between comparative examples 8 and 10 and example 15).
[0078]
[Table 3]
28
Caking additive
(ratio to amount of coal)
Coke
Coal for Maximum weight Maximum weight strength
coke malting loss loss 150
temperature of temperature of
DI
1 5(-)
less than 400°C 400°C or more
Comparative
example 1
C 50%, H 50% Cl 3.0% 84.6
Example 1 C 50%, H 50% C12.1% P2 0.9% 86.0
Example 2 C 50%, H 50% Cl 1.5% P2 1.5% 85.9
Example 3 C 50%, H 50% Cl 0.9% P2 2.1% 85.6
Comparative
example 2
C 50%, H 50% P2 3.0% 84.8
Comparative
example 3
C 50%, H 50% C3 3.0% 85.4
Example 4 C 50%, H 50% C3 2.1% P2 0.9% 86.2
Example 5 C 50%, H 50% C3 1.5% P2 1.5% 86.1
Example 6 C 50%, H 50% C3 0.9% P2 2.1% 85.8
Comparative
example 4
C 50%, H 50% P2 3.0% 84.8
Ceoxmapmaprlaet iv5e
example 5
B 50%, H 50% C2 3.0% 85.3
Example 7 B 50%, H 50% C2 2.1% P1 0.9% 85.7
Example 8 B 50%, H 50% C2 1.5% P1 1.5% 85.9
Example 9 B 50%, H 50% C2 0.9% P 1 2.1% 85.8
Comparative
example 6
B 50%, H 50% P1 3.0% 84.5
Comparative
example 7
B 50%, H 50% C2 5.0% 85.6
Example 10 B 50%, H 50% C2 4.5% PI 0.5% 85.9
Example 11 B 50%, H 50% C2 4.0% P 1 1.0% 86.3
Example 12 B 50%, H 50% C2 2.0% P 1 2.0% 86.4
Example 13 B 50%, H 50% C2 1.0% P1 4.0% 86.0
Example 14 B 50%, H 50% C2 0.5% P1 4.5% 85.3
Comparative
example 8
B 50%, H 50% P 15.0% 84.6
Comparative
exam le 9
p B 50%, H 50% C2 1.0%° 84.3
Example 15 B 50%, H 50% C2 0.5% PI 0.5% 85.0
Comparative
example 10
B 50%, H 50% Pl 1.0% 84.0
* °%" in this table indicates mass percentage.
29
Industrial Applicability
[0079]
As described above, according to the present invention, it is possible to produce
high-strength coke having coke strength that is equivalent to or higher than a coke
5 strength obtained by mixing a single caking additive and coal for coke making.
Therefore, the present invention is highly applicable to the coke production industry.
30
What is claimed is:
1. A method of producing high-strength coke, the method comprising carbonizing a
coal feed including a first caking additive whose maximum weight loss temperature is
5 400°C or higher and a second caking additive whose maximum weight loss temperature
is lower than 400°C in a coal for coke making, the maximum weight loss temperature
being defined as a temperature at which a weight loss rate obtained through a first
derivative of weight loss with respect to time during heating up to 900°C at 3 °C/min
becomes the maximum.
10
2. The method of producing high-strength coke according to claim 1,
wherein a difference between the maximum weight loss temperature of the first
caking additive and the maximum weight loss temperature of the second caking additive
is 50°C or more.
15
3. The method of producing high-strength coke according to claim 1 or 2,
wherein a total amount of the first caking additive and the second caking
additive is 0.2 mass% or more.
20 4. The method of producing high-strength coke according to claim 1 or 2,
wherein a ratio of the first caking additive to the total amount of the first caking
additive and the second caking additive is 0.1 to 0.9 in terms of mass ratio.
5. The method of producing high-strength coke according to claim 1 or 2,
25 wherein a plurality of the first caking additives is included in the coal for coke
making.
6. The method of producing high-strength coke according to claim 1 or 2,
wherein a plurality of the second caking additives is included in the coal for
coke making.
7. The method of producing high-strength coke according to claim 1 or 2,
wherein the first caking additive is a petroleum-derived caking additive,
8. The method of producing high-strength coke according to claim 1 or 2,
wherein the second caking additive is a coah-derived caldng additive.