SPECIFICATION
TITLE OF INVENTION
METHOD OF MEASURING DILATATION OF COAL, METHOD OF ESTIMATING
SPECIFIC VOLUME OF COAL, METHOD OF MEASURING ABILITY TO FILL
INTER-PARTICLE SPACE, AND COAL BLENDING METHOD
Field of the Invention
[0001]
The present invention relates to a method of measuring a dilatation of coal which is an evaluation parameter of the thermoplastic property of coal, a method of estimating a specific volume of coal, a method of measuring an ability to fill inter-particle space, and a coal blending method.
Priorities are claimed on Japanese Patent Application No. 2009-056920, filed March 10,2009, Japanese Patent Application No. 2009-173075, filed July 24,2009, and Japanese Patent Application No. 2009-239098, filed October 16, 2009, the contents of which are incorporated herein by reference.
Description of Related Art
[0002]
In general, blast furnace coke is manufactured by blending many kinds of coal in accordance with the quality required for a blast furnace and then carbonizing the coal blend in a coke oven. When blast furnace coke has a low strength, the flow of a reducing gas in a blast furnace is hindered due to coke breeze which is generated from the coke when the coke is charged into the blast furnace. In this case, the reduction reaction of iron ore is inhibited and it becomes difficult to perform a stable operation in
the blast furnace. Accordingly, blast furnace coke is required to have a strength which
is higher than or equal to a predetermined value.
[0003]
As the coke strength, a drum index such as a JIS drum index (for example, DI1506 or DI15015), an ISO micum index or an ASTM tumbler index, or a shatter index is used. All of these indices indicate the degree of maintaining the state of lump coke without generating coke breeze when a predetermined mechanical impact is applied to the coke (lump coke). The drum index is obtained by automatically repeatedly performing a drop impact test of coke in a cylindrical container. Therefore, this drum index is essentially the same kind of index as the shatter index.
[0004]
When changing the blending of coals, it is necessary to predict the coke strength in advance from the characteristics of various kinds of cokes blended with each other in order to manufacture coke having a predetermined strength (target value) or more. Therefore, techniques for estimating the coke strength from the characteristics of various kinds of cokes blended with each other have been developed, and in many conventional methods, the coke strength is estimated from the coal rank and the caking property which are the characteristics of coal. As an index indicating the coal rank of coal, volatile matter, a reflectance, a carbon content and the like are used. In addition, as an index indicating the caking property of coal, expansibility (for example, dilatation and specific volume), fluidity and the like defined in JIS M 8801 are used.
[0005]
In addition, for example, a method of estimating the coke strength by calculating two parameters corresponding to the coal rank and the caking property from analysis values of macerals, and a method of estimating the coke strength by calculating two
parameters corresponding to the coal rank and the caking property from elemental
analysis values have also been developed. However, in these conventional methods, for
example, when coal (coal in the coal blend) to be used is greatly changed, the coke
strength cannot be estimated with sufficient accuracy.
[0006]
Patent Citation 1 discloses a method of obtaining the ability to fill inter-particle space in the plastic stage of the coal from a product of the specific volume in the plastic stage of the coal and the bulk density of the coal at the time of charging into a coke oven and estimating the surface fracture strength of the coke from this ability to fill inter-particle space in the plastic stage of the coal.
[0007]
This method in Patent Citation 1 is based on the following findings. In the case in which the dilatation of coal with respect to the void fraction between coal particles is high in the plastic stage of the coal, the coal particles cannot be sufficiently expanded. On the other hand, in the case in which the dilatation with respect to the void fraction between the coal particles is low, the coal particles freely expand since there is sufficient space between the particles. When the coal particles freely expand in the plastic stage of the coal, the gas bubbles in the coal particles are broken, and large continuous pores and non-adhesive portions between the coal particles are generated, whereby fragile coke is manufactured. The coal for normal coke making starts to soften and is expanded at a temperature of about 400°C, and is re-solidified at a temperature of about 500°C. Therefore, when obtaining a ratio of filling the spaces with the coal particles during the period from the softening to the re-solidification of the coal (during coking), it is possible to predict the amount of defects of non-adhesive particle boundaries and continuous pores in the coke and estimate the surface fracture strength of the coke.

Patent Citation
[0008]
[Patent Citation 1] Japanese Unexamined Patent Application, First Publication
No. 2002-121565
SUMMARY OF THE INVENTION Problems to be Solved by the Invention
[0009]
However, in recent years, it has been required to use coal having a low caking property, which has not been used as a raw material for coke making, due to the rising price for coal and the like. In greater detail, in order to manufacture coke, it is required to use low-caking property coal (extremely-low total dilatation coal) of which the total dilatation measured by a dilatation test of JIS M 8801 is 0%. For example, this low-caking property coal having a total dilatation of 0% is burned and used in a boiler as fuel.
[0010]
In the method of estimating the coke strength in Patent Citation 1, using coal having a total dilatation of 0% is not considered. Therefore, it is unclear whether this method can be used or not when using coal having a total dilatation of 0%. For this reason, the inventors estimated the strength of coke which is manufactured from the coal blend including coal having a total dilatation of 0% on the basis of the method of Patent Citation 1. Furthermore, the coke strength of blast furnace coke, which is manufactured by carbonizing the coal blend including the above-described coal having a total dilatation of 0%, was measured. Then, the measured coke strength was compared with the estimated coke strength.
[0011]
Table 1 shows values of evaluation parameters for evaluation of thermoplastic properties of coals A to G. The coals A to G are different brands of coals. The coals A and B are coals having a high caking property and the coals C to G are coals having a low caking property and a total dilatation of 0%.
[0012]
[Table 1]
(Table Removed)
[0013]
Here, as described in Patent Citation 1, the specific volume V (cm3/g) in the plastic stage of the coal is obtained from the following Equation (1) or (2) using a coal volume ΔV (cm ) at the time of maximum expansion or a dilatation b (%) of the coal.
V=ΔV/w ...(1)
V=0.96π (l+b/100)/w ...(2)
The reference symbol w represents the amount (g) of coal charged into a dilatometer (dilatometer tube). The coal volume ΔV at the time of maximum expansion and the dilatation b of the coal are measured by a dilatometer.
From the above-described Equation (2), it is found that the coals having the same dilatation b have the same specific volume V in the plastic stage of the coal.
Furthermore, as shown in Patent Citation 1, the ability to fill inter-particle space in the
plastic stage of the coal can be obtained by multiplying the specific volume V in the
plastic stage of the coal by the bulk density of the coal at the time of charging into a coke
oven. In addition, the ability to fill inter-particle space correlates with the coke strength
(for example, surface fracture strength). Accordingly, since the coals having the same
specific volume V (cm3/g) in the plastic stage of the coal have the same ability to fill
inter-particle space (-), they have the same coke strength.
[0014]
Accordingly, the inventors manufactured cokes by carbonizing different kinds of coal blends X1 to X10, and measured coke strengths DI (drum index). The measurement results thereof are shown in Tables 2 and 3. Furthermore, the correlation between the abilities to fill inter-particle space of these coal blends X1 to X10 and the coke strengths DI is shown in FIG. 4. The weighted average efficiency of the specific volume of each of the coals of Table 1 was used as the specific volumes of the coal blends X1 to X10. The data of close squares corresponds to Comparative Example 1 using the coal blends
X1 to X5 corresponding to Table 2. The data of open triangles corresponds to Comparative Example 2 using the coal blends X6 to X10 corresponding to Table 3.
[0015]
Tables 2 and 3 show the blending ratios of the coals A to G used in the coal blends X1 to X10. That is, in the coal blend Xi, 25 mass% of coal A, 25 mass% of coal B, and 50 mass% of coal C are blended. In the coal blend X2, 25 mass% of coal A, 25 mass% of coal B, and 50 mass% of coal D are blended. In the coal blend X3,25 mass% of coal A, 25 mass% of coal B, and 50 mass% of coal E are blended. In the coal blend X4, 25 mass% of coal A, 25 mass% of coal B, and 50 mass% of coal F are blended. In the coal blend X5,25 mass% of coal A, 25 mass% of coal B, and 50 mass% of coal G are
blended.
[0016]
[Table 2]
(Table Removed)
[0017]
In addition, in the coal blend X6, 50 mass% of coal A and 50 mass% of coal C are blended. In the coal blend X7, 50 mass% of coal A and 50 mass% of coal D are blended. In the coal blend X8, 50 mass% of coal A and 50 mass% of coal E are blended. In the coal blend X9, 50 mass% of coal A and 50 mass% of coal F are blended. In the coal blend X10, 50 mass% of coal A and 50 mass% of coal G are blended.
[0018]
[Table 3]
(Table Removed)
[0019]
The coal blends X1 to X5 have the same ability to fill inter-particle space in the
plastic stage of the coal blend. Therefore, from the above description, it is thought that
the coke strengths DI using the coal blends X1 to X5 are the same. Similarly, the coal blends X6 to X10 have the same ability to fill inter-particle space. Therefore, from the above description, it is thought that the coke strengths DI using the coal blends X6 to X10 are the same.
[0020]
However, as shown in Table 2, the coke strengths DI using the coal blends X1 to X5 are different from each other. Similarly, as shown in Table 3, the coke strengths DI using the coal blends X6 to X10 are also different from each other. Accordingly, it is found that the coke strength estimation method in Patent Citation 1 cannot be applied when coke is manufactured using coal blend which includes coal having a total dilatation of 0%.
[0021]
Accordingly, the present invention provides a method of measuring a dilatation (or, specific volume) which can also be applied to the case of coal having a total dilatation of 0%. In addition, the present invention provides a method of estimating a specific volume which can also be applied to the case of coal blend including coal having a total dilatation of 0%. Furthermore, the present invention provides a method of measuring an ability to fill inter-particle space which can also be applied to the case of coal blend including coal having a total dilatation of 0%. In addition, the present invention provides a coal blending method using the method of measuring an ability to fill inter-particle space which can also be applied to the case of coal blend including coal having a total dilatation of 0%. Methods for Solving the Problem
[0022]
The present invention employs the following methods in order to provide a
dilatation measurement method which can also be applied to the case of coal having a
total dilatation of 0%.
(1) A method of measuring a dilatation of a coal according to the present
invention includes: charging the coal into a dilatometer tube; inserting a piston into the
dilatometer tube; heating the coal so that a heating rate in a plastic stage of the coal is 6
°C/min or higher; measuring a displacement of the piston; and obtaining a dilatation of
the coal from the displacement.
[0023]
(2) In the method of measuring the dilatation of the coal according to (1), conditions other than the heating rate may follow a dilatation test of JIS M 8801.
(3) In the method of measuring the dilatation of the coal according to (1), conditions other than the heating rate may follow a dilatation test of ISO 8264.
[0024]
(4) In the method of measuring the dilatation of the coal according to (1), the
coal may be an extremely-low total dilatation coal of which the total dilatation measured
by a dilatation test of JIS M 8801 is 0%.
[0025]
In addition, the present invention employs the following methods in order to provide a method of estimating a specific volume which can also be applied to the case of coal (extremely-low total dilatation coal) having a total dilatation of 0%.
(5) A method of estimating a specific volume in a plastic stage of an
extremely-low total dilatation coal of which a total dilatation measured by a dilatation
test of JIS M 8801 is 0% according to the present invention includes: obtaining in
advance a relationship between a standard specific volume in the plastic stage of the
extremely-low total dilatation coal which is obtained from a dilatation of the
extremely-low total dilatation coal which is measured by the method of measuring the
dilatation of the coal according to (1), and a standard oxygen concentration of the
extremely-low total dilatation coal; and estimating a specific volume in the plastic stage
of the extremely-low total dilatation coal from the oxygen concentration of the
extremely-low total dilatation coal which is measured on the basis of the relationship.
[0026]
(6) In the method of estimating the specific volume in the plastic stage
according to (5), the oxygen concentration of the extremely-low total dilatation coal may
be 9 mass% or higher.
[0027]
(7) In the method of estimating the specific volume in the plastic stage
according to (5), the oxygen concentration of the extremely-low total dilatation coal may
be 12 mass% or lower.
[0028]
In addition, the present invention employs the following methods in order to provide a method of measuring an ability to fill inter-particle space which can also be applied to the case of coal blend including coal having a total dilatation of 0%.
(8) A method of measuring an ability to fill inter-particle space according to the
present invention includes: measuring a dilatation of the coal using the method of
measuring the dilatation of the coal according to (1); obtaining a specific volume in a
plastic stage of the coal from the dilatation; and obtaining an ability to fill inter-particle
space in the plastic stage of the coal by multiplying the specific volume by a bulk density
of the coal at the time of charging into a coke oven.
[0029]
(9) In the method of measuring the ability to fill inter-particle space according to
(8), the coal may be an extremely-low total dilatation coal of which a total dilatation
measured by a dilatation test of JIS M 8801 is 0%.
[0030]
(10) A method of measuring an ability to fill inter-particle space according to the
present invention includes: preparing a plurality of coals; obtaining specific volumes in a
plastic stage of the coals by applying the method of measuring the dilatation of the coal
according to (1) to at least one of the coals; obtaining an average specific volume of a
coal blend by calculating a weighted average of the specific volumes in the plastic stage
of the coals using blending ratios of the coals as a weight; and obtaining an ability to fill
inter-particle space in the plastic stage of the coal blend by multiplying the average
specific volume by a bulk density of the coal blend at the time of charging into a coke
oven.
[0031]
(11) In the method of measuring the ability to fill inter-particle space according
to (10), the coal blend may include an extremely-low total dilatation coal of which a total
dilatation measured by a dilatation test of JIS M 8801 is 0%.
[0032]
(12) A method of measuring an ability to fill inter-particle space according to the
present invention includes: obtaining a specific volume in a plastic stage of an
extremely-low total dilatation coal of which a total dilation measured by a dilatation test
of JIS M 8801 is 0% using the method of estimating the specific volume of the coal
according to (5); and obtaining an ability to fill inter-particle space in the plastic stage of
the extremely-low total dilatation coal by multiplying the specific volume by a bulk
density of the extremely-low total dilatation coal at the time of charging into a coke oven.
[0033]
(13) A method of measuring an ability to fill inter-particle space according to the
present invention includes: preparing a plurality of coals, at least one of the coals being
an extremely-low total dilatation coal of which a total dilatation measured by a dilatation
test of JIS M 8801 is 0%; obtaining specific volumes in a plastic stage of the coals by
applying the method of estimating the specific volume of the coal according to (5) to the
extremely-low total dilatation coal among the coals; obtaining an average specific
volume of a coal blend by calculating a weighted average of the specific volumes in the
plastic stage of the coals using blending ratios of the coals as a weight; and obtaining an
ability to fill inter-particle space in the plastic stage of the coal blend by multiplying the
average specific volume by a bulk density of the coal blend at the time of charging into a
coke oven.
[0034]
(14) In the method of measuring the ability to fill inter-particle space according
to (12) or (13), an oxygen concentration of the extremely-low total dilatation coal may be
9 mass% or higher.
[0035]
(15) In the method of measuring the ability to fill inter-particle space according
to (12) or (13), an oxygen concentration of the extremely-low total dilatation coal may be
12 mass% or lower.
[0036]
The present invention employs the following methods in order to provide a coal blending method which can also be applied to the case of coal blend including coal having a total dilatation of 0%.
(16) A coal blending method according to the present invention includes:
preparing a plurality of coals; obtaining specific volumes in a plastic stage of the coals by
applying the method of measuring the dilatation of the coal according to (1) to at least
one of the coals; obtaining an average specific volume of a coal blend by calculating a
weighted average of the specific volumes in the plastic stage of the coals using blending
ratios of the coals as a weight; obtaining an ability to fill inter-particle space in the plastic
stage of the coal blend by multiplying the average specific volume by a bulk density of
the coal blend at the time of charging into a coke oven; estimating a coke strength of a
coke using the coal blend from the ability to fill inter-particle space in the plastic stage of
the coal blend on the basis of the previously obtained relationship between a standard
ability to fill inter-particle space in the plastic stage of the coal blend and a standard coke
strength of the coke which is manufactured from the coal blend; and blending the coals
so that the coke strength of the coke using the coal blend is higher than or equal to a
predetermined value.
[0037]
(17) In the coal blending method according to (16), the coal blend may include
an extremely-low total dilatation coal of which the total dilatation measured by a
dilatation test of JIS M 8801 is 0%.
[0038]
(18) A coal blending method according to the present invention includes:
preparing a plurality of coals, at least one of the coals being an extremely-low total
dilatation coal of which a total dilatation measured by a dilatation test of JIS M 8801 is
0%; obtaining specific volumes in the plastic stage of the coals by applying the method
of estimating the specific volume of the coal according to (5) to the extremely-low total
dilatation coal among the coals; obtaining an average specific volume of a coal blend by
calculating a weighted average of the specific volumes in a plastic stage of the coals
using blending ratios of the coals as a weight; obtaining an ability to fill inter-particle
space in the plastic stage of the coal blend by multiplying the average specific volume by
a bulk density of the coal blend at the time of charging into a coke oven; estimating a
coke strength of a coke using the coal blend from the ability to fill inter-particle space in
the plastic stage of the coal blend on the basis of the previously obtained relationship
between a standard ability to fill inter-particle space in the plastic stage of the coal blend
and a standard coke strength of the coke which is manufactured from the coal blend; and
blending the coals so that the coke strength of the coke using the coal blend is higher
than or equal to a predetermined value.
[0039]
(19) In the coal blending method according to (18), an oxygen concentration of
the extremely-low total dilatation coal may be 9 mass% or higher.
[0040]
(20) In the coal blending method according to (18), an oxygen concentration of
the extremely-low total dilatation coal may be 12 mass% or lower.
Effects of the Invention
[0041]
According to the present invention, it is possible to measure a dilatation (specific volume) and an ability to fill inter-particle space so as to distinguish coal of which the total dilatation measured by a dilatation test of JIS M 8801 is 0%. In addition, it is possible to easily estimate the specific volume of coal having a total dilatation of 0%. Furthermore, according to the present invention, the coke strength can be easily and accurately estimated at the time of coal blending, and thus the blending ratio of coals can be appropriately determined.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042]
FIG. 1 is a relationship diagram showing the relationship between a heating temperature and the displacement of a piston.
FIG. 2 is a correlation diagram showing the relationship between an ability to fill inter-particle space and a coke strength DI shown in Tables 5 and 6.
FIG. 3 is a correlation diagram showing the relationship between an ability to fill inter-particle space and a coke strength DI shown in Tables 8 and 9.
FIG. 4 is a correlation diagram showing the relationship between an ability to fill inter-particle space and a coke strength DI shown in Tables 2 and 3.
FIG. 5 is a correlation diagram showing the relationship between an ability to fill inter-particle space and a coke strength DI shown in Tables 10 and 11.
FIG. 6 is a correlation diagram showing the relationship between an oxygen concentration of extremely-low total dilatation coal and a specific volume of extremely-low total dilatation coal which is measured at a heating rate of 12 °C/min.
FIG. 7 is a correlation diagram showing the relationship between an oxygen concentration of extremely-low total dilatation coal and a specific volume of extremely-low total dilatation coal which is measured at a heating rate of 6 °C/min.
DETAILED DESCRIPTION OF THE INVENTION
[0043]
The strengths such as a drum index and a shatter index of coke indicate the amount (or, residual amount for lump coke) of coke breeze which is generated from lump coke when a mechanical impact is applied to the lump coke.
[0044]
In general, the particle size distribution of the coke after application of the
mechanical impact has a peak of coarse particles and a peak of fine particles. The coke
belonging to this peak of coarse particles is generated by volume fracture. In addition,
the coke belonging to the peak of fine particles is generated by surface fracture. The
line between the peak of coarse particles (coke generated by volume fracture) and the
peak of fine particles (coke generated by surface fracture) in the above-described particle
size distribution changes in accordance with the coke particle size before application of
the mechanical impact, and in the case of blast furnace coke, the coke particle size is
about 6 mm.
[0045]
The fracture of coke is a brittle fracture starting at a defect in the coke. There is a difference in the defect which is a cause (starting point) of the fracture between the volume fracture and the surface fracture. The starting point of the volume fracture is a large crack which can be visually observed. The starting point of the surface fracture is a portion in which adhesion between coal particles (average particle size of about 1 mm) is insufficient and a crack small enough to be visually confirmed by a microscope.
[0046]
The large crack which is a cause of the volume fracture is generated due to thermal stress which is generated by uneven contraction of the entire coke. The amount of this crack is controlled by the temperature distribution in the coke at the time of carbonization and the contraction coefficient at the time of coal re-solidification. The small crack which is a cause of the surface fracture is generated not by the contraction of the entire coke, but by stress due to local and uneven contraction between coal particles. In addition, the amount of the portion in which adhesion between coal particles is insufficient, which is a main cause of the surface fracture, is controlled by the caking
property and the bulk density of the coal.
[0047]
Here, among the coke breeze which is generated by a coke strength test, the coke breeze having a particle size of 6 mm or less is classified as coke which is generated by the surface fracture.
[0048]
The inventors found that different brands of coals having a total dilatation of 0% can be distinguished from each other by increasing the heating rate (rate of temperature increase) in the plastic stage of coal when the specific volume V (dilatation b) is measured. For example, in Patent Citation 1, since a method defined in JIS M 8801 is used, the heating rate when obtaining the specific volume in the plastic stage of coal is 3.0±0.1 °C/min. However, in the present invention, this heating rate is increased to 6.0 °C/min or more and the specific volume V (or, dilatation b) is measured so as to distinguish the different brands of coals having a total dilatation of 0%. In addition, in this description, the "coal (extremely-low total dilatation coal) having a total dilatation of 0%" is defined as coal of which the total dilatation measured in a dilatation test of JIS M 8801 is 0%. When the dilatation b of this extremely-low total dilatation coal is measured in accordance with ISO 8264, this dilatation b is a predetermined minimum value. In this case, the dilatations b of a plurality of extremely-low total dilatation coals cannot be distinguished. In addition, since the specific volume V and the dilatation b can be converted into each other by the above-described Equation (2), both can be used as expansion characteristics representing the dilatation.
[0049]
The reason for this is as follows. When coal is heated, a gas is generated in molten coal particles, and due to a pressure of this generated gas, the molten coal
particles are expanded. When the heating rate increases, the rate of gas generation by
pyrolysis increases. Due to an increase of this rate of gas generation, the coal particles
are expanded even when the plastic amount of the coal particles is small. Accordingly,
by increasing the heating rate, a difference in the specific volume which cannot be
obtained by the heating rate described in JIS M 8801 can be measured.
[0050]
In order to examine the effect of the heating rate on this difference in the specific volume, the dilatation test was performed using test instruments which are used in a dilatometer method of JIS M 8801. In this dilatation test, a piston was inserted into a dilatometer tube into which coal D having a total dilatation of 0% had been charged, and heating was performed at a predetermined heating rate to measure the displacement of the piston. FIG. 1 shows the relationship between the heating temperature and the displacement of the piston. The data of a measurement example 1 shows the displacement of the piston when the heating is performed at a heating rate of 3.0 °C/min which is defined in JIS M 8801. The data of a measurement example 2 shows the displacement of the piston when the heating is performed at a heating rate of 12.0 °C/min which is higher than the heating rate defined in JIS M 8801.
[0051]
As shown in FIG 1, the coal was not expanded when heated at a heating rate of 3.0 °C/min. When heated at a heating rate of 12.0 °C/min, the coal was expanded, and the piston was greatly displaced. In this manner, even when coal which is not expanded at a heating rate of 3.0 °C/min is used, a reliably high dilatation can be obtained if the dilatation can be measured at a heating rate of 12.0 °C/min.
[0052]
In addition, the inventors found that in extremely-low total dilatation coal, there
is a certain correlation between the specific volume in the plastic stage of coal measured
by the dilatation test in which a heating rate Vtemp in the plastic stage of coal is 6.0
°C/min or higher and the oxygen concentration of the coal measured by a measurement
method defined in JIS M 8813.
Specifically, it was found that in the extremely-low total dilatation coal, the higher the above-described oxygen concentration of the coal is, the lower the specific volume in the plastic stage of coal is.
When the oxygen concentration in the coal is high, the radicals which are generated by pyrolysis in the plastic stage of coal are deactivated and easily stabilized due to oxygen. Therefore, as the oxygen concentration in the coal increases, the caking property (thermoplastic property) is thought to be lowered. Accordingly, the specific volume in the plastic stage of the extremely-low total dilatation coal which is used in actual coal blend can be easily estimated by the following method. First, in main coals for coke making, the specific volume in the plastic stage of coal and the oxygen concentration of the coals are measured by the above-described methods, and a database showing the relationship between the specific volume (standard specific volume) in the plastic stage of coal and the oxygen concentration (standard oxygen concentration) of the coal is prepared in advance. This database and the oxygen concentration of extremely-low total dilatation coal are compared with each other.
Through this method, the dilatation test of the extremely-low total dilatation coal, which takes a long time for measurement, can be skipped, and the specific volume in the plastic stage of the extremely-low total dilatation coal can be estimated using the oxygen concentration of the coal. In general, this oxygen concentration of the coal is analyzed as chemical analysis data together with elements such as carbon in order to manage the
quality of the coal for coke making as a raw material. A method of analyzing this
oxygen concentration of the coal is not limited to the measurement method defined in JIS
M 8813. For example, a measurement method defined in ISO 333 or ISO 1994 can also
be used.
The oxygen concentration of the extremely-low total dilatation coal is, for example, 9 mass% or higher as shown in FIGS. 6 and 7 to be described later. That is, the lower limit of the oxygen concentration of coal having a total dilatation of 0% (extremely-low total dilatation coal) can be defined as 9 mass%.
[0053]
Here, as described above, the coke strength can be estimated by obtaining the ability to fill inter-particle space in the plastic stage of coal. An ability to fill inter-particle space Z(-) in the plastic stage of coal can be calculated from the following Equation (3) using a bulk density Sd (g/cm3) of the coal at the time of charging into a coke oven.
[0054]
Z=VxSd ...(3)
That is, the ability to fill inter-particle space Z in the plastic stage of coal is calculated by obtaining the specific volume V (cm3/g) in the plastic stage of coal and the bulk density Sd (g/cm3) of the coal at the time of charging into a coke oven, and thus the coke strength can be estimated.
[0055]
Furthermore, the specific volume V in the plastic stage of coal is calculated by the above-described Equations (1) and (2) using the dilatation b (%) which is measured by the dilatometer of JIS M 8801.
[0056]
However, when measuring the dilatation b, an electric furnace is heated at a
heating rate of 6.0 °C/min or higher, which is higher than a heating rate of the
dilatometer method of JIS M 8801 in the temperature range of from 300°C to 500°C.
The electric furnace is preferably heated at a heating rate of 12 °C/min or higher. This
heating rate is preferably 50 °C/ min or lower in consideration of the measurement
accuracy of the dilatation and the heating capability of the electric furnace. In addition,
as in JIS M 8801 (or ISO 8264), the dilatation b (%) is defined as a "percentage of the
displacement from the zero position of the piston to the highest position thereof with
respect to the initial length of a sample formed into a rod shape". In addition, the test
conditions other than the heating rate follow the standards of JIS M 8801 (or ISO 8264).
[0057]
Furthermore, the relationship between the ability to fill inter-particle space Z in the plastic stage of coal and the coke strength which are derived from the above-described Equations (1) to (3) is obtained in advance. From this relationship, the coke strength can be estimated.
[0058]
The estimation method of coke strength will be described in detail. First, the specific volumes in the plastic stage of various kinds of coals (brands) are measured, and these coals are blended and then carbonized to manufacture coke. At this time, regarding coal (extremely-low total dilatation coal) having a total dilatation of 0%, the relationship between the oxygen concentration (standard oxygen concentration) of the coal and the specific volume (standard specific volume) in the plastic stage of coal is previously obtained. Furthermore, the bulk density of the coal at the time of charging into a coke oven is previously measured. Next, the coke strength of the manufactured coke is measured. For example, as the coke strength, a drum index DI1506 according to
a drum test method of JIS K 2151 is measured. That is, as a coke strength DI, a drum
index DIrd which is a d mm oversize weight percentage after r rotations can be used. As
the coke strength, another strength index such as an ISO micum index or an ASTM
tumbler index can also be measured.
[0059]
Furthermore, the relationship between the ability to fill inter-particle space (standard ability to fill inter-particle space) in the plastic stage of coal which is calculated from the specific volume in the plastic stage of coal and the bulk density of the coal at the time of charging into the coke oven, and the coke strength DI1506 (standard coke strength) is obtained. When using coal blend including two or more kinds of coals, the weighted average efficiency (weighted average specific volume) of the specific volumes (measured values or estimated values) of the coals may be used as the specific volume (specific volume of the coal blend, average specific volume of the coal blend) in the plastic stage of coal.
As described above, in order to estimate the coke strength, the specific volumes in the plastic stage of the coals which are used are measured in accordance with the above-described method, and the bulk density of the coal (coal blend) at the time of charging into the coke oven when carbonization is performed is predicted from the coal moisture, particle size, and the like. Furthermore, the ability to fill inter-particle space in the plastic stage of coal is calculated from the specific volume in the plastic stage of the coal (coal blend) and the value of the bulk density of the coal (coal blend) at the time of charging into the coke oven. From the value of this ability to fill inter-particle space, the coke strength is estimated using the previously obtained relationship between the ability to fill inter-particle space (standard ability to fill inter-particle space) in the plastic stage of coal and the coke strength (standard coke strength).
[0060]
When the specific volume of the extremely-low total dilatation coal is not
directly measured, the previously prepared database showing the relationship between
the oxygen concentration (standard oxygen concentration) of the coal and the specific
volume (standard specific volume) in the plastic stage of coal, and the oxygen
concentration of the extremely-low total dilatation coal which is used are compared with
each other. Through this method, the specific volume (estimated specific volume) in
the plastic stage of the extremely-low total dilatation coal is estimated. When the
specific volume of the extremely-low total dilatation coal is not directly measured, the
weighted average specific volume is calculated using this estimated specific volume. In
addition, regarding coals other than the extremely-low total dilatation coal of the coal
blend, the specific volume in the plastic stage of coal is calculated from the dilatation
measured by the above-described dilatation test in which the heating rate Vtemp in the
plastic stage of the coal is 6.0 °C/min or higher or the dilatometer method of JIS M 8801.
The weighted specific volumes, each of which is obtained by multiplying this specific
volume by the blending ratio of the coal, of the coals other than the extremely-low total
dilatation coal are added up to obtain the sum of the weighted specific volumes. In
addition, the estimated weighted specific volumes, each of which is obtained by
multiplying the above-described estimated specific volume by the blending ratio of the
coal, of the extremely-low total dilatation coals are added up to obtain the sum of the
estimated weighted specific volumes. The weighted average specific volume (average
specific volume of the coal blend) can be calculated by adding up the sum of the
estimated weighted specific volumes and the sum of the weighted specific volumes.
Furthermore, the bulk density of the coal (coal blend) at the time of charging into the
coke oven during carbonization is predicted from the coal moisture, particle size, and the
like. In addition, the ability to fill inter-particle space in the plastic stage of coal is
calculated from the specific volume in the plastic stage of the coal (coal blend) and the
value of the bulk density of the coal (coal blend) at the time of charging into the coke
oven. From the value of this ability to fill inter-particle space, the coke strength is
estimated using the previously obtained relationship between the ability to fill
inter-particle space (standard ability to fill inter-particle space) in the plastic stage of coal
and the coke strength (standard coke strength).
[0061]
The coke is a porous material and the coke strength is also affected by porosity. That is, when the porosity of the coke is high, the effective cross-sectional area is reduced and properties such as an effective elastic modulus and an effective surface energy change, whereby the coke strength is lowered. Accordingly, the relationship between the porosity of the coke and the coke strength is previously obtained, and when considering the effect of a change in the porosity due to the coal blending, the bulk density of the coal and the like on the coke strength, the estimated accuracy of the coke strength is improved.
[0062]
Here, the porosity of the coke can be estimated from, for example, the bulk density of the coal and the coke yield. In addition, the coke yield can be estimated from, for example, the volatile matter of the coal.
[0063]
As described above, in the present invention, coal is charged into a dilatometer tube of a dilatometer and a piston is inserted into this dilatometer tube. Then, the coal charged into the dilatometer tube is heated so that the heating rate in the plastic stage of the coal is 6 °C/min or higher, the displacement of the piston is measured, and a
dilatation (or, specific volume) is obtained from this displacement. In this case, the
temperature range for the heating rate of 6 °C/min or higher may be from 300°C to
500°C. In addition, conditions other than the heating rate may follow the dilatation test
of JIS M 8801. Similarly, conditions other than the heating rate may follow the
expansibility test method of ISO 8264. Furthermore, the coal of which the dilatation is
to be measured may be coal of which the total dilatation measured by the dilatation test
of JIS M 8801 is 0%. In addition, the coal of which the dilatation is to be measured
may be single brand coal, and may be coal blend obtained by blending a plurality of
brands of coals. The dilatation is calculated as a percentage of the displacement from
the zero position of the piston to the highest position (position of the piston when the coal
is expanded at the maximum) thereof with respect to the initial length of the coal in the
dilatometer tube.
[0064]
The specific volume in the plastic stage of extremely-low total dilatation coal can be estimated by the following method. That is, the relationship between the specific volume (standard specific volume) in the plastic stage of the extremely-low total dilatation coal which is obtained from a dilatation of the coal (extremely-low total dilatation coal) which is measured by the above-described dilatation test in which the heating rate Vtemp in the plastic stage of the coal is 6.0 °C/min or higher and the oxygen concentration (standard oxygen concentration) of the extremely-low total dilatation coal is obtained in advance. The specific volume in the plastic stage of the extremely-low total dilatation coal is estimated from the oxygen concentration of the extremely-low total dilatation coal which is measured on the basis of this relationship.
[0065]
In addition, in a first embodiment of the method of measuring an ability to fill
inter-particle space of the present invention, a plurality of coals are prepared and the
above-described method of measuring a dilatation of coal is applied to at least one of this
plurality of coals to obtain the specific volumes in the plastic stage of the plurality of
coals. The coals of which the dilatation are to be measured may include at least
extremely-low total dilatation coal of which the total dilatation measured by the
dilatation test of JIS M 8801 is 0%. That is, when extremely-low dilatation coal is
included in the plurality of coals, the above-described method of measuring a dilatation
of coal is applied to at least one extremely-low dilatation coal to measure the dilatation of
the extremely-low dilatation coal, and the specific volume in the plastic stage of the
extremely-low dilatation coal is obtained using Equation (2). Furthermore, the
weighted average of the specific volumes in the plastic stage of the plurality of coals is
calculated using blending ratios of the plurality of coals as the weight, and thus the
average specific volume of coal blend is obtained. Then, as shown in Equation (3), the
ability to fill inter-particle space in the plastic stage of the coal blend is obtained by
multiplying this average specific volume by the bulk density of the coal blend at the time
of charging into a coke oven. Here, the coal of which the ability to fill inter-particle
space is to be measured may be single brand coal, and may be coal blend obtained by
blending a plurality of brands of coals. In addition, when obtaining the ability to fill
inter-particle space in the plastic stage of single coal, the above-described method of
measuring a dilatation of coal is used to measure the dilatation of the coal and the
specific volume in the plastic stage of the coal is obtained from this dilatation. As
shown in Equation (3), the ability to fill inter-particle space in the plastic stage of the coal
is obtained by multiplying this specific volume by the bulk density of the coal at the time
of charging into the coke oven.
[0066]
In addition, in a second embodiment of the method of measuring an ability to fill
inter-particle space of the present invention, a plurality of coals including extremely-low
total dilatation coal of which the total dilatation measured by the dilatation test of JIS M
8801 is 0% are prepared, and the specific volumes in the plastic stage of the plurality of
coals are obtained by applying the above-described method of estimating a specific
volume of coal to the extremely-low total dilatation coal among the plurality of coals.
Furthermore, the weighted average of the specific volumes in the plastic stage of the
plurality of coals is calculated using blending ratios of the plurality of coals as the weight,
and thus an average specific volume of coal blend is obtained. Then, as shown in
Equation (3), the ability to fill inter-particle space in the plastic stage of the coal blend is
obtained by multiplying this average specific volume by the bulk density of the coal
blend at the time of charging into a coke oven. In addition, when obtaining the ability
to fill inter-particle space in the plastic stage of single coal, the above-described method
of estimating a specific volume of coal is used to obtain the specific volume in the plastic
stage of the extremely-low total dilatation coal of which the total dilatation measured by
the dilatation test of JIS M 8801 is 0%. As shown in Equation (3), the ability to fill
inter-particle space in the plastic stage of the extremely-low total dilatation coal is
obtained by multiplying this specific volume by the bulk density at the time of charging
into the coke oven of the extremely-low total dilatation coal.
[0067]
Furthermore, in a first embodiment of the coal blending method of the present invention, a plurality of coals are prepared and the above-described method of measuring a dilatation of coal is applied to at least one of this plurality of coals to obtain the specific volumes in the plastic stage of the plurality of coals. The coal of which the dilatation is to be measured may include at least extremely-low total dilatation coal of which the total
dilatation measured by the dilatation test of JIS M 8801 is 0%. That is, when
extremely-low total dilatation coal is included in the plurality of coals, the
above-described method of measuring a dilatation of coal is applied to at least one
extremely-low total dilatation coal to measure the dilatation of the extremely-low total
dilatation coal, and the specific volume in the plastic stage of the extremely-low total
dilatation coal is obtained using Equation (2). Furthermore, the weighted average of the
specific volumes in the plastic stage of the plurality of coals is calculated using blending
ratios of the plurality of coals as the weight, and thus the average specific volume of coal
blend is obtained. Then, as shown in Equation (3), the ability to fill inter-particle space
in the plastic stage of the coal blend is obtained by multiplying this average specific
volume by the bulk density of the coal blend at the time of charging into a coke oven.
On the basis of the relationship between the previously measured ability to fill
inter-particle space (standard ability to fill inter-particle space) and the previously
measured coke strength (standard coke strength), the coke strength of coke using the coal
blend is estimated from the ability to fill inter-particle space in the plastic stage of the
coal blend. On the basis of this estimation, the plurality of coals are blended so that the
coke strength of the coke using the coal blend is higher than or equal to a predetermined
value (target value). As this coke strength, a drum index DI1506 (-) according to the
drum test of JIS K 2151 may be used. This drum index DI1506 represents a 6 mm
oversize percentage after 150 rotations by a drum test machine. In addition, as the coke
strength, another strength index such as an ISO micum index or an ASTM tumbler index
can also be used. Furthermore, the coal blend may include at least coal of which the
total dilatation measured by the dilatation test of JIS M 8801 is 0%. In addition, the
dilatation (specific volume) of the extremely-low total dilatation coal among the plurality
of coals is obtained using the above-described method of measuring a dilatation of coal
(method of measuring a dilatation at a heating rate of 6.0 °C/min or higher) or the
above-described method of estimating a specific volume of coal (method of estimating a
specific volume from the oxygen concentration).
[0068]
In addition, in a second embodiment of the coal blending method of the present invention, a plurality of coals including extremely-low total dilatation coal of which the total dilatation measured by the dilatation test of JIS M 8801 is 0% are prepared, and the specific volumes in the plastic stage of the plurality of coals are obtained by applying the above-described method of estimating a specific volume of coal to the extremely-low total dilatation coal among the plurality of coals. Furthermore, the weighted average of the specific volumes in the plastic stage of the plurality of coals is calculated using blending ratios of the plurality of coals as the weight, and thus an average specific volume of coal blend is obtained. Then, as shown in Equation (3), the ability to fill inter-particle space in the plastic stage of the coal blend is obtained by multiplying this average specific volume by the bulk density of the coal blend at the time of charging into a coke oven. On the basis of the relationship between the previously measured ability to fill inter-particle space (standard ability to fill inter-particle space) and the previously measured coke strength (standard coke strength), the coke strength of coke using the coal blend is estimated from the ability to fill inter-particle space in the plastic stage of the coal blend. On the basis of this estimation, the plurality of coals are blended so that the coke strength of the coke using the coal blend is higher than or equal to a predetermined value (target value). As this coke strength, a drum index DI1506 (-) according to the drum test of JIS K 2151 may be used. This drum index DI1506 represents a 6 mm oversize percentage after 150 rotations by a drum test machine. In addition, as the coke strength, another strength index such as an ISO micum index or an ASTM tumbler index
can also be used. Furthermore, the coal blend may include at least coal of which the
total dilatation measured by the dilatation test of JIS M 8801 is 0%.
Examples
[0069]
(Examples 1 and 2)
The coals A to G were subjected to the dilatation test using the dilatometer method of JIS M 8801. The heating rate at the temperature of from 300°C to 500°C in the plastic stage of the coal was set to 12 °C/min which is higher than that of JIS. These coals A to G were sieved into a particle size of 2.8 mm or less (undersize of 2.8 mm). As shown in Table 4, the specific volumes of the coals A, B, C, D, E, F, and G were 5.07 cm3/g, 2.10 cm3/g, 1.75 cm3/g, 1.65 cm3/g, 1.43 cm3/g, 1.29 cm3/g, and 1.27 cm3/g, respectively.
[0070]
[Table 4]
(Table Removed)
[0071]
As shown in Table 1, in the case of the heating rate of 3.0 °C/min, it was not possible to distinguish the specific volumes of the extremely-low total dilatation coals C to G. However, as shown in Table 4, it was possible to distinguish the specific volumes of these coals C to G by increasing the heating rate to 12.0 °C/min. In addition, in the
case of the coals A and B of which the total dilatation was not 0%, a difference between the specific volumes of the coals A and B was enlarged by increasing the heating rate from 3.0 °C/min to 12.0 °C/min.
[0072]
The oxygen concentrations of the coals C to G which were extremely-low total dilatation coals were measured, and the relationship between an oxygen concentration 0% of the coal and a specific volume V in the plastic stage was obtained. Oxygen concentrations 0% of the above-described coals were measured on the basis of an "Calculating Method of Oxygen Percentage (Measurement Method of Oxygen Content)" of "Coal and Coke-Determination of constituents" of JIS M 8813. FIG. 6 is a diagram showing the relationship between the oxygen concentration 0% and the specific volume V in the plastic stage of the coals C to G which were extremely-low total dilatation coals. As shown in FIG. 6, the specific volume V in the plastic stage of coal increased with a reduction in the oxygen concentration 0% of the coal. As an example of an equation expressing this relationship, the specific volume V in the plastic stage of coal is expressed by Equation (4) using the oxygen concentration 0% of the coal.
V=-0.25xO%+4.25 ...(4)
The specific volume V in the plastic stage of coal can be easily estimated by measuring the oxygen concentration 0% of the extremely-low total dilatation coal and substituting this oxygen concentration 0% into Equation (4). As an equation expressing the relationship between the oxygen concentration 0% of the coal and the specific volume V in the plastic stage, a primary expression such as Equation (4) is preferably used since the specific volume can be easily estimated. However, an arbitrary estimated equation can also be used as the relational expression between the oxygen concentration 0% of the coal and the specific volume V in the plastic stage of
coal.
[0073]
In the above-described FIG. 6, the oxygen concentration of the coal G having the highest oxygen concentration was 12%. When measuring a dilatation (specific volume) of extremely-low total dilatation coal having a higher oxygen concentration than this coal G, the heating rate is preferably set to be higher than 12 °C/min. Through this method, the specific volumes in the plastic stage of coal can be distinguished, and the relationship between the oxygen concentration of the coal and the specific volume in the plastic stage of coal can be obtained by the primary expression. That is, in the case of extremely-low total dilatation coal having an oxygen concentration of 12% or lower, the specific volumes in the plastic stage of coal can be distinguished by setting the heating rate to 12 °C/min. In addition, in the case of extremely-low total dilatation coal having an oxygen concentration higher than 12%, the specific volumes in the plastic stage of coal can be reliably distinguished by setting the heating rate to a rate higher than 12 °C/min.
[0074]
Furthermore, specific volumes of coal blends X1 to X10 including the coals C to G were calculated and the coal blends were subjected to a breaking strength test. Table 5 shows the results of the coal blends X1 to X5 (Example 1) and Table 6 shows the results of the coal blends X6 to X10 (Example 2).
[0075]
Here, a specific method of calculating the specific volume in the plastic stage of the coal blend X1 will be described. The specific volumes in the plastic stage of the coals (coals of which the total dilatation is not 0%) other than the extremely-low total dilatation coal which are included in the coal blend Xi, that is, the coals A and B are measured by the dilatation test according to the dilatometer method of JIS M 8801. The
weighted specific volume 0.6325 (cm3/g) is calculated by multiplying the specific
volume 2.53 (cm3/g) in the plastic stage of the coal A which is shown in Table 1 by the
blending ratio 0.25 of the coal A. The weighted specific volume 0.2625 (cm3/g) is
calculated by multiplying the specific volume 1.05 (cm3/g) in the plastic stage of the coal
B which is shown in Table 1 by the blending ratio 0.25 of the coal B. By measuring the
oxygen concentration of the coal C and by interpolating or extrapolating this measured
oxygen concentration in FIG 6, the estimated specific volume 1.75 (cm3/g) in the plastic
stage of the coal C is obtained. The estimated weighted specific volume 0.875 (cm3/g)
is calculated by multiplying this estimated specific volume in the plastic stage of the coal
C by the blending ratio 0.50 of the coal C. The specific volume 1.77 (cm3/g) in the
plastic stage of the coal blend X1 is obtained by adding up the above-described weighted
specific volumes of the coals A and B and the estimated weighted specific volume of the
coal C. Also in the case of the coal blends X2 to X10, the specific volume in the plastic
stage of coal is calculated by the same method. The specific volume (dilatation) of the
extremely-low total dilatation coal may be directly measured at a heating rate of 12
°C/min to obtain the specific volume of the coal blend. In this case, the weighted
specific volume 0.875 (cm3/g) is calculated by multiplying the specific volume 1.75
(cm3/g) in the plastic stage of the coal C by the blending ratio 0.5 of the coal C. Then,
the specific volume 1.77 (cm3/g) in the plastic stage of the coal blend X1 can be obtained
by adding up the weighted specific volumes of the coals A to C.
[0076]
[Table 5]
(Table Removed)
[0077] [Table 6]
(Table Removed)
[0078]
Furthermore, FIG. 2 shows the relationship between the ability to fill inter-particle space and the coke strength DI shown in Tables 5 and 6. The data of close squares corresponds to Example 1 using the coal blends X1 to X5 corresponding to Table 5. The data of open triangles corresponds to Example 2 using the coal blends X6 to X10 corresponding to Table 6. The horizontal axis of FIG. 2 represents the ability to fill inter-particle space in the plastic stage of coal, and the vertical axis represents the coke strength DI. The coke strength DI is a drum index DI1506 according to the drum test of JIS K 2151. As shown in FIG. 2, there is a certain correlation between the ability to fill inter-particle space and the coke strength DI. Therefore, the strength of coke in which fragile coal having a total dilatation of 0% is included in coal blend can be accurately
estimated by accumulating this correlation as the database.
[0079]
(Examples 3 and 4)
The coals C to G were subjected to the dilatation test according to the dilatometer method of JIS M 8 801. The heating rate at the temperature of from 3 00°C to 500°C in the plastic stage of the coal was set to 6 °C/min which is higher than that of JIS. These coals C to G were sieved into a particle size of 2.8 mm or less (undersize of 2.8 mm). As shown in Table 7, the specific volumes of the coals C, D, E, F, and G were 1.43 cm3/g, 1.34 cm3/g, 1.26 cm3/g, 1.25 cm3/g, and 1.24 cm3/g, respectively.
[0080]
[Table 7]
(Table Removed)
[0081]
As shown in Table 1, in the case of the heating rate of 3.0 °C/min, it was not possible to distinguish the specific volumes of the coals C to G having a total dilatation of 0%. However, as shown in Table 7, it was possible to distinguish the specific volumes of these coals C to G by increasing the heating rate to 6.0 °C/min. Furthermore, from the comparison of Table 4 with Table 7, it was found that by increasing the heating rate, a difference between the specific volumes of the coals C to G increases and the specific volumes of the coals C to G can be distinguished more significantly.
[0082]
The oxygen concentrations of the coals C to G which were coals (extremely-low total dilatation coals) having a total dilatation of 0% were measured, and the relationship between an oxygen concentration 0% of the coal and a specific volume V in the plastic stage of coal was obtained. The oxygen concentrations 0% of the coals were measured on the basis of the "Calculating Method of Oxygen Percentage (Measurement Method of Oxygen Content)" of "Coal and Coke-Determination of constituents" of JIS M 8813. FIG. 7 is a diagram showing the relationship between the oxygen concentration 0% and the specific volume V in the plastic stage of the coals C to G. As shown in FIG. 7, the specific volume V in the plastic stage of coal increased with a reduction in the oxygen concentration 0% of the coal. As an example of an equation expressing this relationship, the specific volume V in the plastic stage of coal is expressed by Equation (5) using the oxygen concentration 0% of the coal.
V=-0.09xO%+2.23 ...(5)
As shown in FIGS. 6 and 7, it was found that even in the case of coal (extremely-low total dilatation coal) of which the total dilatation measured in the conventional dilatation test of JIS M 8801 is 0%, the specific volumes in the plastic stage of coal can be distinguished by increasing the heating rate in the dilatation test to 6.0 °C/min or higher, and the relationship between the specific volume in the plastic stage of coal and the oxygen concentration of the coal can be approximated by the primary expression.
[0083]
Furthermore, the specific volumes of the coal blends X1 to X10 including the coals C to G were calculated and the coal blends were subjected to a breaking strength test. Table 8 shows the test results of the coal blends X1 to X5 (Example 3) and Table 9
shows the test results of the coal blends X6 to X10 (Example 4).
[0084]
Here, a specific method of calculating the specific volume in the plastic stage of the coal blend X1 will be described. The specific volumes in the plastic stage of the coals A and B other than the extremely-low total dilatation coal which are included in the coal blend X1 are measured using the dilatation test according to the dilatometer method of JIS M 8801. The weighted specific volume 0.6325 (cm3/g) was calculated by multiplying the specific volume 2.53 (cm3/g) in the plastic stage of the coal A which is shown in Table 1 by the blending ratio 0.25 of the coal A. The weighted specific volume 0.2625 (cm3/g) was calculated by multiplying the specific volume 1.05 (cmVg) in the plastic stage of the coal B which is shown in Table 1 by the blending ratio 0.25 of the coal B. By measuring the oxygen concentration of the coal C and by interpolating or extrapolating this measured oxygen concentration in FIG 7, the estimated specific volume 1.43 (cm3/g) in the plastic stage of the coal C was obtained. The estimated
weighted specific volume 0.715 (cm3/g) was calculated by multiplying this estimated specific volume in the plastic stage of the coal C by the blending ratio 0.50 of the coal C. The specific volume 1.61 (cm3/g) in the plastic stage of the coal blends X1 was obtained by adding up the above-described weighted specific volumes of the coals A and B and the estimated weighted specific volume of the coal C. Also in the case of the coal blends X2 to X10, the specific volume in the plastic stage of coal was calculated by the same method. The specific volume (dilatation) of the extremely-low total dilatation coal may be directly measured at a heating rate of 6 °C/min to obtain the specific volume of the coal blend. In this case, the weighted specific volume 0.715 (cm3/g) is calculated by multiplying the specific volume 1.43 (cm3/g) in the plastic stage of the coal C by the blending ratio 0.50 of the coal C. Then, the specific volume 1.61 (cm3/g) in the plastic
stage of the coal blend X1 can also be obtained by adding up the weighted specific
volumes of the coals A to C.
[0085]
[Table 8]
(Table Removed)
[0086] [Table 9]
(Table Removed)
[0087]
Furthermore, FIG. 3 shows the relationship between the ability to fill inter-particle space and the coke strength DI shown in Tables 8 and 9. The data of close squares corresponds to Example 3 using the coal blends X1 to X5 corresponding to Table 8. The data of open triangles corresponds to Example 4 using the coal blends X6 to X10 corresponding to Table 9. The horizontal axis of FIG. 3 represents the ability to fill inter-particle space in the plastic stage of coal, and the vertical axis represents the coke
strength DI. The coke strength DI is a drum index DI1506 according to the drum test of
JIS K 2151. As shown in FIG. 3, there is a certain correlation between the ability to fill
inter-particle space and the coke strength DI. By accumulating this correlation as the
database, the coke strength can be easily estimated even when fragile coal having a total
dilatation of 0% is used as coal blend of coke. Furthermore, from the comparison of
FIG. 2 with FIG 3, it was found that by increasing the heating rate, a difference between
the abilities to fill inter-particle space of the coal blends X1 to X10 increases and the coke
strength can be more accurately estimated.
[0088]
In the above-described Examples 1 to 4, the dilatation test of the coals (coals A and B) other than the extremely-low total dilatation coal was performed by the dilatometer method of JIS M 8801. Also in the dilatation test of the coals other than the extremely-low total dilatation coal, the heating rate in the plastic stage of coal can be increased to 6.0 °C/min or higher as in the case of the extremely-low total dilatation coal. For example, in the following Examples 5 and 6, the heating rate in the plastic stage of coal is set to 12.0 °C/min in the case of the coals A and B.
[0089]
(Examples 5 and 6)
Furthermore, strengths DI (estimated DI) of cokes manufactured from coal blends X11 to X20 were estimated using the specific volumes of the coals A and B shown in Table 4 and the oxygen concentrations of the coals C to G The specific volumes of the coal blends X11 to X20 were obtained by a weighted average method to be described later. In addition, the ability to fill inter-particle space was calculated using Equation (3), and the coke strength (measured DI) was measured by a breaking strength test. Table 10 (Example 5) shows the specific volumes (weighted average specific volumes)
and the coke strengths DI (estimated values and measured values) of coal blends using
the coal blends X11 to X15. Similarly, Table 11 (Example 6) shows the specific volumes
(weighted average specific volumes) and the coke strengths DI (estimated values and
measured values) of coal blends using the coal blends X16 to X20.
[0090]
[Table 10]
(Table Removed)
[0091] [Table 11]
(Table Removed)
[0092]
A specific method of calculating the weighted average specific volume of the coal blend X1 will be described. The weighted specific volume 1.521 (cm3/g) is calculated by multiplying the specific volume 5.07 (cm3/g) in the plastic stage of the coal A which is shown in Table 4 by the blending ratio 0.3 of the coal A. The weighted specific volume 0.63 (cm3/g) is calculated by multiplying the specific volume 2.10
(cm3/g) in the plastic stage of the coal B which is shown in Table 4 by the blending ratio
0.3 of the coal B. By measuring the oxygen concentration of the coal C and by
interpolating or extrapolating this measured oxygen concentration in FIG 6, the
estimated specific volume 1.75 (cm3/g) in the plastic stage of the coal C is obtained.
The estimated weighted specific volume 0.7 (cm3/g) is calculated by multiplying this
estimated specific volume in the plastic stage of the coal C by the blending ratio 0.40 of
the coal C. Next, the weighted average specific volume 2.85 (cm3/g) of the coal blend
X11 is calculated by adding up the weighted specific volumes of the coals A and B and
the estimated weighted specific volume of the coal C. The weighted average specific
volumes of the coal blends X12 to X15 are also calculated by the same method.
[0093]
Similarly, the weighted average specific volumes of the coal blends X16 to X20 are obtained with reference to Table 4 and FIG. 6. Furthermore, the ability to fill inter-particle space in the plastic stage of coal is calculated using Equation (3). Table 11 shows the calculated weighted average specific volumes and the abilities to fill inter-particle space in the plastic stage of coal.
[0094]
In addition, the specific volume of the extremely-low total dilatation coal can also be directly measured to calculate the specific volume of the coal blend. For example, regarding the composition of the coals in the coal blend Xn, the blending ratios of the coals A, B, and C are 30 mass%, 30 mass%, and 40 mass%, respectively. The specific volume of this coal blend X11 can be calculated by adding up products of the specific volume of each coal and the blending ratio of each coal. For example, as shown in Table 4, since the specific volume of the coal A is 5.07, the specific volume of the coal B is 2.10, and the specific volume of the coal C is 1.75, the specific volume of
this coal blend X11 is calculated as 2.85 from Equation (6).
(5.07x0.3)+(2.10x0.3)+(l .75x0.4)=2.85 .. .(6)
[0095]
FIG. 5 shows the relationship between the ability to fill inter-particle space and the coke strength DI. The data of close squares (measured DI) corresponds to the coal blends X11 to X15 of Table 10 showing Example 5. The data of open triangles (measured DI) corresponds to Table 11 showing Example 6. Using the solid line of FIG. 5, estimated DIs of cokes using the coal blends X11 to X20 can be obtained from the abilities to fill inter-particle space in the plastic stage of coal. For example, since the ability to fill inter-particle space of the coal blend X11 is 2.28(-), the estimated DI of the coal blend X11 can be evaluated as 79.7(-) from the solid line of FIG. 5. From Tables 10 and 11, it is found that a difference between the estimated DI and the measured DI in the cokes using the coal blends X11 to X20 is small. In this manner, by performing the dilatation test at a heating rate of 6.0 °C/min or higher, the coke strength can be accurately and easily estimated even when coal having a total dilatation of 0% is included in coal blend. In addition, a target specific volume of the coal blend can be determined so that the coke strength is nearly higher than or equal to a predetermined value. Therefore, coal brands to be used in coal blend and blending ratios of the coal brands can be determined. For example, coal blend (for example, the coal blend X11
having a weighted average specific volume of 2.85 (cm3/g)) having a weighted average specific volume of 2.81 (cm3/g) or higher is used in order to enhance the coke strength DI to 78(-) or higher. In this manner, even when coal (coal in the coal blend) to be used is changed, the blending ratio of each coal can be easily determined.
[0096]
(Modified Examples)
In the above-described embodiments, coke having a total dilatation of 0%, coal
blend which includes coal having a total dilatation of 0%, and coke using this coal blend
have been described. However, the method of measuring a dilatation of coal, the
method of measuring an ability to fill inter-particle space, and the coal blending method
of the present invention are not limited to thereto. That is, the present invention can
also be applied to coal having a total dilatation higher than 0%, coal blend which
includes only coals having a total dilatation higher than 0%, and coke using this coal
blend.
In addition, the above-described dilatation b(%) measured by a dilatometer and the estimated specific volume V can be used not only in the estimation of the coke strength, but also in, for example, the estimation of another physical quantity such as an swelling pressure. Industrial Applicability
[0097]
It is possible to provide a method of measuring a dilatation which can be applied to the case of coal having a total dilatation of 0%, a method of estimating a specific volume of coal, a method of measuring an ability to fill inter-particle space, and a coal blending method.

What is claimed is:
1. A method of measuring a dilatation of a coal, the method comprising:
charging coal into a dilatometer tube; inserting a piston into the dilatometer tube;
heating the coal so that a heating rate in a plastic stage of the coal is 6 °C/min or higher;
measuring a displacement of the piston; and
obtaining a dilatation of the coal from the displacement.
2. The method of measuring the dilatation of the coal according to claim 1,
wherein conditions other than the heating rate follow a dilatation test of JIS M 8801.
3. The method of measuring the dilatation of the coal according to claim 1,
wherein conditions other than the heating rate follow a dilatation test of ISO 8264.
4. The method of measuring the dilatation of the coal according to claim 1,
wherein the coal is an extremely-low total dilatation coal of which a total dilatation measured by a dilatation test of JIS M 8801 is 0%.
5. A method of estimating a specific volume in a plastic stage of an extremely-low total
dilatation coal of which a total dilatation measured by a dilatation test of JIS M 8801 is
0%, the method comprising:
obtaining in advance a relationship between a standard specific volume in the
plastic stage of the extremely-low total dilatation coal which is obtained from a dilatation
of the extremely-low total dilatation coal which is measured by the method of measuring
the dilatation of the coal according to claim 1, and a standard oxygen concentration of the
extremely-low total dilatation coal; and
estimating a specific volume in the plastic stage of the extremely-low total
dilatation coal from the oxygen concentration of the extremely-low total dilatation coal
which is measured on the basis of the relationship.
6. The method of estimating the specific volume in the plastic stage according to claim
5,
wherein the oxygen concentration of the extremely-low total dilatation coal is 9 mass% or higher.
7. The method of estimating the specific volume in the plastic stage according to claim
5,
wherein the oxygen concentration of the extremely-low total dilatation coal is 12 mass% or lower.
8. A method of measuring an ability to fill inter-particle space, the method comprising:
measuring a dilatation of the coal using the method of measuring the dilatation
of the coal according to claim 1;
obtaining a specific volume in a plastic stage of the coal from the dilatation; and obtaining an ability to fill inter-particle space in the plastic stage of the coal by
multiplying the specific volume by a bulk density of the coal at the time of charging into
a coke oven.
9. The method of measuring the ability to fill inter-particle space according to claim 8,
wherein the coal is an extremely-low total dilatation coal of which a total dilatation measured by a dilatation test of JIS M 8801 is 0%.
10. A method of measuring an ability to fill inter-particle space, the method
comprising:
preparing a plurality of coals;
obtaining specific volumes in a plastic stage of the coals by applying the method of measuring the dilatation of the coal according to claim 1 to at least one of the coals;
obtaining an average specific volume of a coal blend by calculating a weighted average of the specific volumes in the plastic stage of the coals using blending ratios of the coals as a weight; and
obtaining an ability to fill inter-particle space in the plastic stage of the coal blend by multiplying the average specific volume by a bulk density of the coal blend at the time of charging into a coke oven.
11. The method of measuring the ability to fill inter-particle space according to claim
10,
wherein the coal blend includes an extremely-low total dilatation coal of which a total dilatation measured by a dilatation test of JIS M 8801 is 0%.
12. A method of measuring an ability to fill inter-particle space, the method
comprising:
obtaining a specific volume in a plastic stage of an extremely-low total dilatation
coal of which a total dilation measured by a dilatation test of JIS M 8801 is 0% using the
method of estimating the specific volume of the coal according to claim 5; and
obtaining an ability to fill inter-particle space in the plastic stage of the
extremely-low total dilatation coal by multiplying the specific volume by a bulk density
of the extremely-low total dilatation coal at the time of charging into a coke oven.
13. A method of measuring an ability to fill inter-particle space, the method
comprising:
preparing a plurality of coals, at least one of the coals being an extremely-low total dilatation coal of which a total dilatation measured by a dilatation test of JIS M 8801 is 0%;
obtaining specific volumes in a plastic stage of the coals by applying the method of estimating the specific volume of the coal according to claim 5 to the extremely-low total dilatation coal among the coals;
obtaining an average specific volume of a coal blend by calculating a weighted average of the specific volumes in the plastic stage of the coals using blending ratios of the coals as a weight; and
obtaining an ability to fill inter-particle space in the plastic stage of the coal blend by multiplying the average specific volume by a bulk density of the coal blend at the time of charging into a coke oven.
14. The method of measuring the ability to fill inter-particle space according to claim
12 or 13,
wherein an oxygen concentration of the extremely-low total dilatation coal is 9
mass% or higher.
15. The method of measuring the ability to fill inter-particle space according to claim
12 or 13,
wherein an oxygen concentration of the extremely-low total dilatation coal is 12 mass% or lower.
16. A coal blending method comprising:
preparing a plurality of coals;
obtaining specific volumes in a plastic stage of the coals by applying the method of measuring the dilatation of the coal according to claim 1 to at least one of the coals;
obtaining an average specific volume of a coal blend by calculating a weighted average of the specific volumes in the plastic stage of the coals using blending ratios of the coals as a weight;
obtaining an ability to fill inter-particle space in the plastic stage of the coal blend by multiplying the average specific volume by a bulk density of the coal blend at the time of charging into a coke oven;
estimating a coke strength of a coke using the coal blend from the ability to fill inter-particle space in the plastic stage of the coal blend on the basis of the previously obtained relationship between a standard ability to fill inter-particle space in the plastic stage of the coal blend and a standard coke strength of a coke which is manufactured from the coal blend; and
blending the coals so that the coke strength of the coke using the coal blend is higher than or equal to a predetermined value.
17. The coal blending method according to claim 16,
wherein the coal blend includes an extremely-low total dilatation coal of which a total dilatation measured by a dilatation test of JIS M 8801 is 0%.
18. A coal blending method comprising:
preparing a plurality of coals, at least one of the coals being an extremely-low total dilatation coal of which a total dilatation measured by a dilatation test of JIS M 8801 is 0%;
obtaining specific volumes in a plastic stage of the coals by applying the method of estimating the specific volume of the coal according to claim 5 to the extremely-low total dilatation coal among the coals;
obtaining an average specific volume of a coal blend by calculating a weighted average of the specific volumes in the plastic stage of the coals using blending ratios of the coals as a weight;
obtaining an ability to fill inter-particle space in the plastic stage of the coal blend by multiplying the average specific volume by a bulk density of the coal blend at the time of charging into a coke oven;
estimating a coke strength of a coke using the coal blend from the ability to fill inter-particle space in the plastic stage of the coal blend on the basis of the previously obtained relationship between a standard ability to fill inter-particle space in the plastic stage of the coal blend and a standard coke strength of the coke which is manufactured from the coal blend; and
blending the coals so that the coke strength of the coke using the coal blend is higher than or equal to a predetermined value.
19. The coal blending method according to claim 18,
wherein an oxygen concentration of the extremely-low total dilatation coal is 9 mass% or higher.
20. The coal blending method according to claim 18,
wherein an oxygen concentration of the extremely-low total dilatation coal is 12 mass% or lower.