JP6889632B2 - Method for determining the mixing ratio and method for producing coke - Google Patents

Description

The present invention relates to a method for determining a blending ratio and a method for producing coke.

Coke used as a raw material for steelmaking is required to have high strength and a certain particle size in order to ensure air permeability in a blast furnace.

In general, it is known that when a low-shrinkage coal material is blended with coal, the strength of the obtained coke is reduced, while the coke particle size is improved.

Therefore, in Patent Document 1, by adjusting the composition in consideration of the degree of influence on the coke surface fracture crushing rate of the low-shrinkage coal material and the degree of influence on the coke particle size, both expansion of the coke particle size and maintenance of coke strength are achieved. I'm trying to do it.

Japanese Unexamined Patent Publication No. 2011-26514

On the other hand, in recent years, there has been a demand for coke that can further secure air permeability in a blast furnace.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for determining the mixing ratio of simple coal for producing coke capable of further ensuring air permeability in a blast furnace. There is. Another object of the present invention is to provide a method for producing coke that can further secure air permeability in a blast furnace.

The coke is fired in a furnace to obtain a coke mass, which is then crushed through steps such as fire extinguishing and transportation. That is, it is stabilized. Here, the coke particle size means the particle size of coke in a state of being crushed to some extent after undergoing a predetermined step.

The present inventors have diligently studied coke that can further secure the air permeability in the blast furnace. As a result, it was discovered that anisotropy occurs in the cracking method of coke that has undergone a certain degree of stabilization from the coke mass, depending on the amount and properties (for example, particle size) of the low-shrinkage coal material added as a coke raw material. .. Then, if the anisotropy of the cracking method is large, it is inferred that the coke contributes more to ensuring the air permeability in the blast furnace. It was also found that when the anisotropy of cracking is within a specific range, the decrease in coke strength is small, but the average particle size is significantly improved. Based on the above findings, the present invention has been completed.

The blending ratio determining method according to the present invention is a blending ratio determining method for a plurality of types of simple coal containing a low shrinkage coal material.
_{The coefficient α determined when Dp, initial particle size Dp 0} , and D (Dp) obtained by the following procedures (a) to (c) are applied to the Gaudin-Meloy-Harris particle size distribution formula shown in the formula (1) is It is characterized by including a step A of determining the blending ratio of the plurality of types of simple coal so as to be within a specific range.

（ここで、α、及び、γは係数である。）

(Here, α and γ are coefficients.)

Procedure (a): A charged coal containing a plurality of types of simple coal is carbonized to produce coke.
Procedure (b): Defines the initial particle size Dp ₀ of coke.
Procedure (c): The stabilized coke is sieved to obtain the weight% D (Dp) remaining on the sieve of each mesh Dp (mm).

The coefficient α is a coefficient representing the anisotropy of cracking. Specifically, the larger the coefficient α, the smaller the anisotropy of the cracking method, and the smaller the coefficient α, the larger the anisotropy of the cracking method.
According to the above configuration, the blending ratio of the plurality of types of simple coal is determined so that the coefficient α is within a specific range. In other words, if a value with a coefficient α as small as possible is adopted within the range where the decrease in coke strength is tolerable and the average particle size can be improved, the anisotropy of cracking becomes large, so that the inside of the blast furnace It is possible to determine the compounding ratio that can produce coke that can further secure the air permeability in the blast furnace.
In addition, within what range of the coefficient α, whether the decrease in coke strength is tolerable is small depending on the type of simple coal to be blended, etc., but the lower limit is the required coke. It can be decided as appropriate according to the specifications of.

In the above configuration, the step A is preferably a step of determining the blending ratio of the plurality of types of simple coal so that the coefficient α is in the range of 1.7 to 3.0.

According to the studies by the present inventors, in general, the coefficient α when the low shrinkage carbonaceous material is not blended is around 3. On the other hand, the coefficient α at which the decrease in coke strength became remarkable was around 1.5. Therefore, if the coefficient α is 1.7 or more, a significant decrease in coke strength is suppressed. On the other hand, if the coefficient α is set to 3.0 or less, the anisotropy of the cracking method can be increased to some extent.

In the above configuration, the low shrinkage coal material is preferably coke breeze.

Coke powder has a relatively low shrinkage rate among low-shrink coal materials. Therefore, since the difference in shrinkage rate from the surrounding charcoal becomes large, microcracks are generated before large cracks are generated, and the stress is relaxed. As a result, it is excellent in that the effect of improving the particle size can be more preferably obtained.

Further, the method for producing coke according to the present invention is as follows.
Step X of blending the plurality of types of simple coal at the blending ratio determined by the blending ratio determining method to obtain charged coal, and
Step Y to obtain coke by carbonizing the charged coal obtained in step X.
It is characterized by including.

According to the above configuration, the plurality of types of simple charcoal are blended at the blending ratio determined by the blending ratio determining method to obtain coke. Therefore, coke that can further secure the air permeability in the blast furnace can be obtained.

According to the present invention, it is possible to provide a method for determining the mixing ratio of simple coal for producing coke that can further secure the air permeability in the blast furnace. Further, it is possible to provide a method for producing coke that can further secure the air permeability in the blast furnace.

It is a graph for obtaining the coefficient α of Production Example 1. 6 is a graph showing the relationship between the coefficient α and the average particle size of the added coke breeze for Production Examples 1 to 6. 6 is a graph showing the relationship between the coefficient α and the coke intensity DI for Production Examples 1 to 6. 6 is a graph showing the relationship between the coefficient α and the average particle size of the obtained coke for Production Examples 1 to 6. It is a graph which shows the relationship between the coefficient α and the ratio of the added coke breeze about Production Example 7 to Production Example 11. 6 is a graph showing the relationship between the coefficient α and the coke intensity DI for Production Examples 7 to 11. 6 is a graph showing the relationship between the coefficient α and the average particle size of the obtained coke for Production Examples 7 to 11. It is the figure which showed typically the coke for crack confirmation.

Hereinafter, the method for determining the blending ratio according to the present embodiment will be described first, and then the method for producing coke according to the present embodiment will be described.

The blending ratio determining method according to the present embodiment is a blending ratio determining method for a plurality of types of simple coal including a low shrinkage coal material.
_{The coefficient α determined when Dp, initial particle size Dp 0} , and D (Dp) obtained by the following procedures (a) to (c) are applied to the Gaudin-Meloy-Harris particle size distribution formula shown in the formula (1) is The step A of determining the blending ratio of the plurality of types of simple coal so as to be within a specific range is included.

（ここで、α、及び、γは係数である。）

(Here, α and γ are coefficients.)

Procedure (a): Carbonized coal containing a plurality of types of simple coal is carbonized to produce coke.
Procedure (b): Defines the initial particle size Dp ₀ of coke.
Procedure (c): The stabilized coke is sieved to obtain the weight% D (Dp) remaining on the sieve of each mesh Dp (mm).

[Procedure (a)]
In step (a), charged coal containing a plurality of types of simple coal containing a low-shrinkage coal material is carbonized to produce coke. The size of the coke is not particularly limited. From the viewpoint of conducting the test under the same conditions as during operation, a diameter of about 450 mm is preferable. The test coke having a diameter of about 450 mm can be produced by using, for example, a movable wall furnace. On the other hand, from the viewpoint of facilitating the test, a diameter of about 300 mm is preferable. The test coke having a diameter of about 300 mm can be produced, for example, by using a can container.

The low-shrinkage coal material refers to a coal material having a shrinkage rate at 1000 ° C. smaller than that of coal as measured by a high-temperature dilatometer. The low shrinkage carbonaceous material contributes to increasing the coke particle size and increasing the anisotropy of cracking. The shrinkage rate is preferably 10% or less, and more preferably 5% or less. Specifically, the shrinkage rate is a value measured by the method described in Examples.

The present inventors speculate that the reason why the anisotropy of cracking increases when a low-shrinkage carbonaceous material is added is as follows. When the low-shrinkage carbon material (inactive substance) is added, the stress caused by the difference in heat shrinkage is relieved at the place where the inert substance is added. This stress relaxation is effective for the occurrence of small cracks, but it is assumed that it cannot be completely suppressed for the occurrence of large cracks. Therefore, the effect of adding the Inactive substance is considered to be greater for relatively small cracks. Here, in general, when a coke mass is cracked, a large crack (longitudinal crack) is formed in the carbonization direction (longitudinal direction), whereas a large number of small cracks (horizontal crack) are formed in the horizontal direction. It is in. From the above, lateral cracks with many small cracks are more susceptible to the crack suppression effect due to the inert substance, and as the rate of reduction of lateral cracks increases, the balance between vertical cracks and lateral cracks changes, and the cracking method differs. The direction becomes large.

Specific examples of the low-shrinkage coal material include coke breeze, anthracite, graphite, petroleum coke, carbon fiber and the like. Of these, powdered coke is preferable. Coke powder has a relatively low shrinkage rate among low-shrink coal materials. Therefore, since the difference in shrinkage rate from the surrounding coal becomes large, microcracks are generated before large cracks are generated, and the stress is relaxed. As a result, it is excellent in that the effect of improving the particle size can be more preferably obtained.

Various conditions (dry distillation temperature, dry distillation time, etc.) for producing coke are not particularly limited within an appropriate range for obtaining the coefficient α, and can be appropriately set. For example, the method described in the examples can be adopted.

[Procedure (b)]
In step (b), "the initial particle size Dp ₀ of the coke produced in step (a) is specified. For example, in actual operation, the coke width immediately after being extruded from the kiln, that is, the furnace width of the coke oven is set as the initial grain size. The diameter is Dp _{0. When} test coke is produced using a can container, the length of one side of the can container that is parallel to the direction in which the heat of the firing furnace is applied is the initial particle size. Dp _{0. The} same applies when test coke is produced using a movable wall furnace.

[Procedure (c)]
As a pretreatment for the α calculation described later, the coke is pulverized by a predetermined method. The crushing method is not particularly limited, but in an actual furnace, stabilization such as fire extinguishing and transportation in the process from the kiln mouth to the blast furnace is assumed. Further, in the test, it may be determined assuming the condition that the diameter is stabilized to the extent that the diameter is put into the actual furnace. For example, the method described in the examples can be adopted.
In the procedure (c), the stabilized coke is sieved to obtain the weight% D (Dp) remaining on the sieve of each mesh Dp (mm). The method for obtaining D (Dp) is not particularly limited, but for example, as described in Examples, sieving is performed with sieves of 50 mm, 38 mm, 25 mm, and 15 mm, and each sieve Dp (mm) is obtained. The weight% D (Dp) remaining on the sieve is obtained. However, the sieving method in the present invention is not limited to this example. For example, the size of each sieve is not limited to this example and can be set as appropriate. Further, the number of sieves to be sieved is not limited to this example, and can be set as appropriate. However, it is preferable to adopt the method described in the examples because the correlation between the obtained coefficient α and the anisotropy of the cracking method is better.

_{In step A, the coefficient is derived from the initial particle size Dp 0} defined in the above procedure (b) and the Dp and D (Dp) obtained in the above procedure (c) using the Gaudin-Meloy-Harris particle size distribution formula. Find α. The coefficient α can be obtained, for example, by the method described in Examples.

Next, it is determined whether or not the obtained coefficient α is within a specific range. If the obtained coefficient α is within a specific range, the compounding ratio compounded in the procedure (a) is determined as a specific compounding ratio.

On the other hand, if the obtained coefficient α is not within the specific range, the blending ratio is changed and the steps (a) to (c) are repeated. At this time, the mixing ratio is changed in the direction in which the coefficient α is within the specific range (the direction approaching the specific range). For example, when it is desired to lower the value of the coefficient α, a change such as increasing the addition amount of the low shrinkage carbonaceous material is made. When the obtained coefficient α is within the specific range by repeating the above operation, the compounding ratio finally compounded in the procedure (a) is determined as the specific compounding ratio.

The specific range is preferably 1.7 to 3.0. That is, it is preferable that the step A is a step of determining the blending ratio of the plurality of types of simple coal so that the coefficient α is in the range of 1.7 to 3.0.

According to the studies by the present inventors, in general, the coefficient α when the low shrinkage carbonaceous material is not blended is around 3. On the other hand, the coefficient α at which the decrease in coke strength became remarkable was around 1.5. Therefore, if the coefficient α is 1.7 or more, a significant decrease in coke strength is suppressed. On the other hand, if the coefficient α is set to 3.0 or less, the anisotropy of the cracking method can be increased to some extent.

The specific range is preferably within a range in which the coke strength DI of the coke is 80 or more. When the coke strength DI of the coke is 80 or more, it can be said that the strength is sufficiently maintained.

The specific range is preferably within a range in which the average particle size of the coke is 40 mm or more. When the average particle size of the coke is 40 mm or more, it can be said that the average particle size is sufficiently expanded.

As described above, according to the blending ratio determining method according to the present embodiment, the blending ratio of the plurality of types of simple coal is determined so that the coefficient α is within the specific range. In other words, if a value with a coefficient α as small as possible is adopted within the range where the decrease in coke strength is tolerable and the average particle size can be improved, the anisotropy of cracking becomes large, so that the inside of the blast furnace It is possible to determine the compounding ratio that can produce coke that can further secure the air permeability in the blast furnace.

The method for determining the blending ratio according to the present embodiment has been described above.

Next, a method for producing coke according to the present embodiment will be described.

The method for producing coke according to the present embodiment includes the step X of blending the plurality of types of simple coal at the blending ratio determined by the blending ratio determining method to obtain charged coal, and
Step Y to obtain coke by carbonizing the charged coal obtained in step X.
including.

[Step X]
In step X, the plurality of types of simple coal are blended at the blending ratio determined by the blending ratio determining method to obtain charged coal.

[Step Y]
In step Y, the charged coal obtained in step X is carbonized to obtain coke. As the conditions for carbonization and the like, conventionally known conditions may be adopted.

In the method for producing coke according to the present embodiment, a conventionally known method is adopted except that the plurality of types of simple coal are blended at the blending ratio determined by the blending ratio determining method to obtain charged coal. be able to.

As described above, according to the method for producing coke according to the present embodiment, the plurality of types of simple coal are blended at the blending ratio determined by the blending ratio determining method to obtain coke. Therefore, coke that can further secure the air permeability in the blast furnace can be obtained.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

<Preparation of test coke>
(Manufacturing Example 1: Base formulation A)
Multiple types of coal were mixed in a predetermined ratio. When blending, it was blended after being crushed with a jaw crusher, a coffee mill or a hammer mill so that the proportion of those having a crushed particle size of 3 mm or less was about 80%. In Production Example 1, powdered coke as a low-shrinkage coal material was not blended (the blending amount of powdered coke was set to zero).

After preparing the blended coal, the water content was adjusted to 7.5% ± 0.2%.

Next, the water-adjusted sample was filled in a can container having an L: 235 mm × W: 300 mm × H: 235 mm at a filling density of 735 dry-kg / m ³ .

Next, it was carbonized at a dry distillation temperature of 1050 ° C. for about 19 hours to obtain test coke.

(Manufacturing Example 2)
From the formulation of Production Example 1, the coal content was reduced by 3% (3% when the total blended coal was 100%), and 3% coke breeze A was added instead. That is, in Production Example 2, 3% of the total coal blended in Production Example 1 was transferred to coke breeze A. Except for this, test coke was obtained in the same manner as in Production Example 1. The coke breeze A has a particle size of less than 0.25 mm and an average particle size of 0.125 mm.

(Manufacturing Example 3)
From the formulation of Production Example 1, the coal content was reduced by 3% (3% when the total blended coal was 100%), and 3% coke breeze B was added instead. That is, in Production Example 3, 3% of the total coal blended in Production Example 1 was transferred to coke breeze B. Except for this, test coke was obtained in the same manner as in Production Example 1. The coke breeze B has a particle size of 0.25 mm or more and less than 0.50 mm, and an average particle size of 0.375 mm.

(Manufacturing Example 4)
From the formulation of Production Example 1, the coal content was reduced by 3% (3% when the total blended coal was 100%), and 3% coke breeze C was added instead. That is, in Production Example 4, 3% of the total coal blended in Production Example 1 was transferred to coke breeze C. Except for this, test coke was obtained in the same manner as in Production Example 1. The coke breeze C has a particle size of 0.50 mm or more and less than 1.00 mm, and an average particle size of 0.75 mm.

(Manufacturing Example 5)
From the formulation of Production Example 1, the coal content was reduced by 3% (3% when the total blended coal was 100%), and 3% coke breeze D was added instead. That is, in Production Example 5, 3% of the total coal blended in Production Example 1 was transferred to coke breeze D. Except for this, test coke was obtained in the same manner as in Production Example 1. The coke breeze D has a particle size of 1.00 mm or more and less than 1.50 mm, and an average particle size of 1.25 mm.

(Manufacturing Example 6)
From the formulation of Production Example 1, the coal content was reduced by 3% (3% when the total blended coal was 100%), and 3% coke breeze E was added instead. That is, in Production Example 6, 3% of the total coal blended in Production Example 1 was transferred to coke breeze E. Except for this, test coke was obtained in the same manner as in Production Example 1. The coke breeze E has a particle size of 1.50 mm or more and less than 2.00 mm, and an average particle size of 1.75 mm.

(Base formulation B)
A plurality of types of coal were blended so that the blended coal properties corresponded to Production Example 1.

(Manufacturing Example 7)
From the base composition B, the coal content was reduced by 1% (1% when the total combination coal was 100%), and 1% of coke breeze A was added instead. Except for this, test coke was obtained in the same manner as in Production Example 1.

(Manufacturing Example 8)
The coal content was reduced by 3% (3% when the total coal compound was 100%) from the base compound B, and 3% coke breeze A was added instead. Except for this, test coke was obtained in the same manner as in Production Example 1.

(Manufacturing Example 9)
The coal content was reduced by 6% (6% when the total coal compound was 100%) from the base compound B, and 6% of coke breeze A was added instead. Except for this, test coke was obtained in the same manner as in Production Example 1.

(Manufacturing Example 10)
The coal content was reduced by 1% (1% when the total coal compound was 100%) from the base compound B, and 1% of coke breeze C was added instead. Except for this, test coke was obtained in the same manner as in Production Example 1.

(Manufacturing Example 11)
The coal content was reduced by 3% (3% when the total coal compound was 100%) from the base compound B, and 3% coke breeze C was added instead. Except for this, test coke was obtained in the same manner as in Production Example 1.

The formulations of Production Examples 1 to 11 are summarized in Table 1.

<Measurement of shrinkage rate>
When the shrinkage rate of the test coke of Production Example 1 was measured under the following conditions, it was 12.8%. Moreover, when the shrinkage rate of the powdered corcos A to E was measured under the following conditions, it was 0.0% in each case.
[Shrinkage rate measurement conditions]
Equipment: High temperature dilatometer (JIS M 8801 expansiveness test method (dilatometer method) compliant)
Achievement temperature: 1000 ℃
Heating rate: 3 ° C / min
Sample amount: 5 g
Sample height: 100 mm
Sample particle size: less than 0.25 mm

<Calculation of coefficient α>
First, the initial particle size Dp ₀ of the produced coke was defined (procedure (b)). In Production Example 1, the initial particle size Dp ₀ was 300 mm.

Next, the test coke was dropped twice from a height of 2 m. Then, it was put into a drum (inner diameter 1.5 m × body length 1.5 m) and rotated at 15 rpm for 2 minutes. As described above, the test coke was crushed.

The coke after crushing was sieved with sieves of 50 mm, 38 mm, 25 mm, and 15 mm, and the weight% D (Dp) remaining on the sieve of each sieve Dp (mm) was obtained (procedure (procedure (procedure (procedure)). c)).

_{Next, from the initial particle size Dp 0} obtained in the above procedure (b) and the Dp and D (Dp) obtained in the above (c), the coefficient α is calculated using the Gaudin-Meloy-Harris particle size distribution formula. I asked.
Specifically, first, the equation (1) was modified to be as follows.
ln (1-D (Dp)) = γln (1- (Dp / Dp ₀ ) ^α )
Then, "ln (1-D (Dp))" is defined as the x-axis, and "ln (1- (Dp / Dp ₀ ) ^α )" is defined as the y-axis, and the initial particle diameters Dp ₀ , Dp, and D (Dp) are substituted. When the obtained values were plotted on the xy coordinates (4 points), the coefficient α was obtained so that the approximate straight line obtained by the least squares method had the highest correlation coefficient in the straight line passing through the origin. The results are shown in Table 2. For reference, FIG. 1 shows a graph for obtaining the coefficient α only for Production Example 1.

<Particle size distribution of test coke>
The particle size distribution after pulverization was measured using a sieve. The results are shown in Table 2.

<Calculation of average particle size of test coke>
It was calculated by a weighted average from the representative particle size and ratio of each particle size distribution shown in Table 2. Specifically, it was calculated as follows.
Typical particle size of fractions of 100 mm or more is 112.5 mm, ratio is A%,
The representative particle size of fractions of 75 mm or more and less than 100 mm is 87.5 mm, and the ratio is B%.
The representative particle size of fractions of 50 mm or more and less than 75 mm is 62.5 mm, and the ratio is C%.
The representative particle size of fractions of 38 mm or more and less than 50 mm is 44.0 mm, and the ratio is D%.
The representative particle size of fractions of 25 mm or more and less than 38 mm is 31.5 mm, and the ratio is E%.
The representative particle size of fractions of 15 mm or more and less than 25 mm is 20.0 mm, and the ratio is F%.
The representative particle size of fractions less than 15 mm was 7.5 mm, and the ratio was G%.
(Average particle size (mm)) = (112.5 × A + 87.5 × B + 62.5 × C + 44.0 × D + 31.5 × E + 20.0 × F + 7.5 × G) / 100
The results are shown in Table 2.

<Measurement of coke strength DI>
The obtained test coke was subjected to a shutter test twice, 30 rotations with a drum tester, and then 150 rotations with a drum tester to measure ^{DI 150} _15. DI ¹⁵⁰ ₁₅ is the ratio on the 15 mm sieve after 150 rotations by the drum tester specified in JIS K 2151. The results are shown in Table 2.

<Discussion 1: About Production Examples 1 to 6>
FIG. 2 is a graph showing the relationship between the coefficient α and the average particle size of the added coke breeze for Production Examples 1 to 6. FIG. 3 is a graph showing the relationship between the coefficient α and the coke intensity DI for Production Examples 1 to 6. FIG. 4 is a graph showing the relationship between the coefficient α and the average particle size of the obtained coke for Production Examples 1 to 6. FIGS. 2 to 4 were created based on the values in Table 2.
From FIG. 2, when the amount of coke breeze added as the low-shrinkage coal material is the same, the coefficient α decreases as the average particle size of the coke breeze added increases (the anisotropy of cracking increases). It turns out that there is a tendency.
Further, from FIG. 3, it can be seen that the coke intensity DI tends to decrease as the coefficient α decreases. However, when the coefficient α is in the range of 2 to 3, it can be seen that the degree of decrease in the coke strength DI is smaller than that in the base formulation (Production Example 1: No formulation of powdered coke).
Further, from FIG. 4, it can be seen that the average particle size of the obtained coke tends to increase as the coefficient α decreases. In particular, it can be seen that the average particle size of the obtained coke tends to increase as the coefficient α decreases until the coefficient α reaches around 2. However, in the range where the coefficient α is smaller than 2, the average particle size of the obtained coke does not change significantly regardless of the α value. It can also be seen that when the average particle size of coke powder is larger than a certain value, it does not contribute to the expansion of the average particle size of coke (for example, Production Example 6).
From the above, according to Production Examples 1 to 6, it can be seen that the coke with the powdered coke added has a smaller coefficient α than the coke without the addition. Further, when the coefficient α is particularly in the range of 2 to 3 (more preferably in the range of 2.0 to 2.5), the decrease in coke strength is suppressed and the coke strength can be obtained (see FIG. 3). It can be seen that the effect of increasing the average particle size of coke can also be obtained (see FIG. 4).

<Discussion 2: About Production Example 7 to Production Example 11>
FIG. 5 is a graph showing the relationship between the coefficient α and the ratio of the added coke breeze in Production Examples 7 to 11. FIG. 6 is a graph showing the relationship between the coefficient α and the coke intensity DI for Production Examples 7 to 11. FIG. 7 is a graph showing the relationship between the coefficient α and the average particle size of the obtained coke for Production Examples 7 to 11. FIGS. 5 to 7 were created based on the values in Table 2. Note that FIGS. 5 to 7 also plot Production Example 1 for comparison.
From FIG. 5, when the coke breeze as the low shrinkage coal material has the same properties (when the particle size distribution and the average particle size are the same), the coefficient α decreases as the amount of coke breeze added increases. It can be seen that there is a tendency (the anisotropy of cracking increases).
Further, from FIG. 6, it can be seen that the coke intensity DI tends to decrease as the coefficient α decreases. However, when the coefficient α is in the range of 2 to 3, it can be seen that the degree of decrease in the coke strength DI is smaller than that in the base formulation B (Production Example 7).
Further, from FIG. 7, it can be seen that the average particle size of the obtained coke tends to increase as the coefficient α decreases.
From the above, according to Production Examples 7 to 11, it can be seen that the coke to which a large amount of powdered coke is added has a smaller coefficient α than the coke to which a small amount of coke is added. Further, if the coefficient α is particularly in the range of 2 to 3 (more preferably in the range of 2.0 to 2.5), the decrease in coke strength is suppressed and the coke strength can be obtained (see FIG. 6). It can be seen that the effect of increasing the average particle size of coke is also obtained (see FIG. 7).

[Correlation verification between coefficient α and cracking anisotropy]
<Making coke for checking cracks>
(Manufacturing Example 12)
Multiple types of coal were mixed in a predetermined ratio. When blending, it was blended after being crushed with a jaw crusher or a coffee mill so that the proportion of those having a crushed particle size of 3 mm or less was about 80%. In Production Example 12, powdered coke as a low-shrinkage coal material was not blended (the blending amount of powdered coke was set to zero).

After preparing the blended coal, the water content was adjusted to 7.5% ± 0.2%.

Next, the water-adjusted sample was filled in a movable wall furnace having L: 1.17 m × W: 0.41 m × H: 0.80 m at a filling density of 735 dry-kg / m ³ .

Next, carbonization was carried out at a dry distillation temperature of 830 ° C. for 8 hours, at 920 ° C. for 6 hours, and at 960 ° C. for 2 hours, and then carbonized at 1010 ° C., and finally 1.5 hours after the coke core temperature reached 950 ° C. It was carbonized to obtain coke for checking cracks.

(Manufacturing Example 13)
From the formulation of Production Example 12, the coal content was reduced by 1% (1% when the total blended coal was 100%), and 1% of coke breeze A was added instead. That is, in Production Example 13, 1% of the total coal blended in Production Example 12 was transferred to coke breeze A. Other than that, a coke for confirming cracks was obtained in the same manner as in Production Example 12.

The formulations of Production Examples 12 to 13 are summarized in Table 3.

<Measurement of the number of cracks>
FIG. 8 is a diagram schematically showing a crack confirmation coke. The crack confirmation coke is in a state after being taken out from the movable wall furnace and before being crushed. As shown in FIG. 8, there are vertical cracks and horizontal cracks in the crack confirmation coke. Vertical cracks are cracks that extend in the width direction of the furnace, and lateral cracks are cracks that extend in the height direction of the furnace. The number of vertical cracks and the number of horizontal cracks were counted for the crack confirmation coke obtained in Production Example 12 and Production Example 13. The results are shown in Table 4. The ratio of the number of vertical cracks to the number of horizontal cracks [(number of vertical cracks) / (number of horizontal cracks)] is also shown in Table 4. Whether it belongs to a vertical crack or a horizontal crack was determined by measuring the angle of the crack with respect to one side of the coke block for checking the crack and determining which one it belongs to depending on whether it belongs to 45 ° or more.

<Calculation of coefficient α>
The coefficient α was set in the same manner as in Production Examples 1 to 11 except that the initial particle size Dp ₀ was 410 mm and the coke in the central portion excluding the end and the upper part of the coke in the firing term was used. Calculated. The results are shown in Table 4.

<Particle size distribution of coke for crack measurement>
The particle size distribution was measured in the same manner as the test coke (Production Examples 1 to 11). The results are shown in Table 4.

<Calculation of average particle size of coke for crack measurement>
It was calculated by a weighted average from the representative particle size and ratio of each particle size distribution shown in Table 4. Specifically, it was calculated by the same method as the test coke (Production Examples 1 to 11).

<Verification result>
From Table 4, when powdered coke was added, the ratio of longitudinal cracks to lateral cracks increased. From this, it can be seen that when powdered coke is added, the direction of cracks is biased. In addition, the coefficient α also became smaller when powdered coke was added to the coke for crack measurement. From the above, it was confirmed that when the coefficient α becomes smaller, the direction of the crack is biased, that is, the anisotropy of the cracking method becomes larger.
Further, from Table 4, it was also confirmed that the average particle size of the obtained coke increases as the coefficient α decreases in the coke for crack measurement.

Claims (3)

It is a method for determining the mixing ratio of multiple types of simple coal including low-shrinkage coal.
_{The coefficient α determined when Dp, initial particle size Dp 0} , and D (Dp) obtained by the following procedures (a) to (c) are applied to the Gaudin-Meloy-Harris particle size distribution formula shown in the formula (1) is , A method for determining a blending ratio, which comprises step A for determining the blending ratio of the plurality of types of simple coal so as to be in the range of 1.7 to 3.0.

(Here, α and γ are coefficients.)
Procedure (a): Carbonized coal containing a plurality of types of simple coal is carbonized to produce coke.
Procedure (b): Defines the initial particle size Dp ₀ of coke.
Procedure (c): The stabilized coke is sieved to obtain the weight% D (Dp) remaining on the sieve of each mesh Dp (mm). The method for determining a blending ratio according to claim 1, wherein the low-shrinkage charcoal material is coke breeze. Step X of blending the plurality of types of simple coal at the blending ratio determined by the blending ratio determining method according to claim 1 or 2 to obtain charged coal, and
Step Y to obtain coke by carbonizing the charged coal obtained in step X.
A method for producing coke, which comprises.

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