JP2001181650A - Method for preparing coal for charging into coke oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing coal for charging into a coke oven, by which the coal capable of giving coke having a high strength is prepared. SOLUTION: This method for preparing the coal for charging into a coke oven is characterized by comprising a process for classifying plural brands of coal into three or more groups having different coking properties, a process for compounding the classified brands of the coal for each group, a process for crushing the coal compounded for each group to obtain a grain size corresponding to each coking property, and a process for mixing all groups of the coal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting coal charged in a coke oven.

[0002]

2. Description of the Related Art Various types of coke typified by coke for blast furnaces are produced by blending and pulverizing a large number of brands of coal (raw coal) and then charging the resulting mixture into a coke oven. The charged coal is carbonized at a high temperature in the furnace to form coke. A particularly important quality control item during coke production is coke strength. The coke strength varies depending on the particle size of the pulverized coal, even if the blending conditions of the coal are the same. Therefore, in order to obtain high coke strength, the particle size of the whole coal blend after pulverization is generally controlled so that the particle ratio of 3 mm or less is 70 to 90% by weight.

[0003] Depending on the type of coal, the particle size and pulverizability at the time of arrival differ. Therefore, when the blended coal is pulverized as it is, soft coal with good pulverizability is preferentially pulverized. It exists as coarse particles having a large particle size after pulverization. Since there is a large difference in the thermal expansion and contraction behavior during dry distillation between the non-finely caking coal particles and the surrounding area that serves as the coke substrate, large thermal stress occurs at the interface between the non-finely caking coal particles having a large particle size. Cracks are likely to occur. As a result, the coke strength may decrease.

[0004] Therefore, before the pulverized coal is pulverized, it is necessary to remove the raw materials having different properties.
Several methods have been proposed for improving coke strength by dividing the group into two groups and separately pulverizing each group to a particle size according to properties.

One of the methods is disclosed in Japanese Unexamined Patent Publication No. Hei 8-25995.
No. 3 (hereinafter referred to as Document 1). The method of Document 1 divides coal into two groups having different grindability, and the group with high grindability grinds coarser than the target particle size of the entire blended coal, and the group with low grindability grinds finer than the target value. . Adjust the mixture ratio of both groups to obtain the final particle size target value. By separately pulverizing the coal according to the pulverizability, adjust the particle size of the fine powder portion of the entire blended coal,
The purpose is to increase the bulk density of coal charged into a coke oven to improve the coke strength. In the literature 1, coal having a hard glove pulverizability index (HGI) of 80 or more is defined as high pulverizable coal, and coal having a hard glove pulverizability index of less than 80 is defined as low pulverizable coal.

However, coal having high pulverizability includes not only caking coal but also non-coking coal. FIG. 1 shows the results of measurement of the relationship between HGI and the maximum average reflectance (Ro) for both caking coal and non-moking caking coal. As shown in FIG. 1, the coal having an HGI of 80 or more includes not only caking coal but also non-fine caking coal having high reflectance (high-reflectance non-fine caking coal). Therefore, when a group having high grindability is roughly pulverized as in the method of Document 1, the proportion of particles having a large particle size of non-coking coal increases, and as described above, coke strength may decrease. . Therefore, there is a possibility that the coke strength cannot be sufficiently increased by the method of Reference 1.

Another method of pulverizing raw coal into two groups having different properties is disclosed in JP-A-9-279152 (hereinafter referred to as Reference 2). The method of Document 2 divides the coal into two groups with different total expansion rates, crushes the coal with the higher total expansion coarser than the specified particle size, and crushes the coal with the lower total expansion finer than the specified particle size Is what you do. However, since coal having a small total expansion contains non-coking coal, if finely pulverized, the proportion of fine powder of non-coking coal having both low reflectance and high reflectance increases. The fine powder having a high reflectivity further reduces the coke strength similarly to the fine powder having a low reflectivity. Therefore, when the coal having a small total expansion coefficient is finely pulverized as in the method of Reference 2, the coke strength may be reduced. Therefore, there is a possibility that the coke strength cannot be sufficiently increased even by the method of Reference 2.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preparing coal for charging a coke oven, which can obtain high-strength coke.

[0009]

According to the present invention, a step of classifying a plurality of brands of coal into three or more groups having different coking properties, a step of blending coal for each group, and a step of A method for preparing coal for charging a coke oven, comprising: a step of pulverizing blended coal to a particle size according to coking properties; and a step of mixing coals of all groups. .

In the present invention, in the classification step, the coal is classified into groups of low-reflectivity non-fine caking coal, high-reflectivity non-fine caking coal and caking coal, In order to keep the whole particle size distribution after mixing the coal at a predetermined value, the coal of the group of the low-reflectance non-finely-coking coals has a particle ratio of 3 mm or less of 3 to 12% less than the predetermined value. Crushed so that the proportion of particles of 3 mm or less is within ± 3% by weight of the predetermined value. Is preferably ground so that the proportion of particles having a size of 3 mm or less is 3 to 12% by weight lower than the predetermined value.

Further, in the present invention, in the pulverizing step, the coal of the group of low-reflectance non-coking coal is further pulverized so that the ratio of particles having a diameter of 0.5 mm or less is 40% by weight or less. It is preferable to pulverize the coal of the group of the high-reflectance non-coking coals so that the ratio of particles having a size of 0.5 mm or less is 45% by weight or less.

[0012] The non-coking coal refers to coal having a Gieseller fluidity (MF) of 10 or less, or coal having an MF of 200 or less and a maximum average reflectance (Ro) of 0.8 or less. In addition, high-reflectivity non-slightly caking coal refers to coal having an MF of 10 or less and Ro of about 0.9 or more, and low-reflectance non-slightly caking coal means MF of 10 or less and Ro of about 10% or less. Coal below 0.9.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a raw coal is first divided into three or more groups having different coking properties. Next, coal is blended in the same group according to predetermined blending conditions. Next, the blended coal is pulverized for each group, and the particle size distribution of each group is determined according to its coking properties. However, the particle size distribution of each group is determined so that the particle size distribution of the entire blended coal after mixing all the groups can be maintained at a predetermined target particle size value. Finally, all the pulverized coals of the group are mixed to obtain a coke oven charging coal having a predetermined particle size distribution. The particle size distribution of the charging coal is an average particle size distribution of the entire charging coal, and is set to a predetermined target value of the particle size for increasing the charging bulk density and coke strength into the coke oven.

[0014] The coking property is a property such that when the coal is carbonized, after softening and melting, when the temperature is further increased, coke is formed by baking. The strength of the cokeability is determined based on the magnitude of the generated coke (JIS-M0104).

As described above, the raw coal is divided into three or more groups having different coking properties and separately pulverized,
It is possible to suppress an increase in coarse particles and fine powder of non-coking coal and to increase the strength of the generated coke. Cokeability is determined by three or more parameters such as TI (all inerts) in addition to MF and Ro described above. Therefore, the effect of improving the coke strength is greater when the groups are divided into as many as three or more groups. For example, if coking coal is 2
When divided into groups, in order to keep the overall particle size after mixing constant, it is necessary to finely pulverize the other group by the amount of coarsely pulverizing one group. However, the coke strength of high-reflectivity non-finely caking coal is reduced regardless of whether it is coarse or fine. , There is a possibility that the coke strength is reduced. Accordingly, coke strength can be improved by dividing the raw coal into three or more groups and separately pulverizing the group of high-reflectance non-slightly caking coal. Note that the number of groups is actually
The decision is made in consideration of an increase in the quality improvement effect amount due to an increase in the number of groups and an increase in cost associated therewith.

In order to pulverize coal into a desired particle size distribution, the number of rotations of the pulverizer per unit time or the gap between the pulverizing blade and the impact plate may be adjusted.

In the present invention, the raw coal is preferably classified into three groups: low-reflectance non-slightly caking coal, high-reflectance non-slightly caking coal, and caking coal. Cokeability is
Caking coal is the best, and worse in order of low-reflectance non-slightly caking coal and high-reflectance non-slightly caking coal. In addition, the pulverizability of a caking coal having a high Ro and a high-reflectance non-slightly caking coal is as good as that of the caking coal, and the low-reflectance non-slightly caking coal is bad.

As described above, the raw coal is divided into three groups having different coking properties and pulverizability, and the low-reflectivity non-slightly caking coal and the high-reflectance non-slightly caking coal having different influences on the coke strength reduction. As a separate group, suppresses the increase in coarse particles of low-reflectivity non-fine caking coal due to the difference in grindability, and further suppresses the increase in coarse particles and fine powder of high-reflectivity non-fine caking coal be able to. As a result, the generated coke intensity can be further increased.

Since the coarse particles of the low-reflectance non-coking coal group have poor coking properties, it is preferable that the coal of this group be pulverized finer than the target particle size of the entire blended coal. That is, the low-reflectance non-slightly caking coal is 3 mm
The ratio of the following particles is 3 to 12 higher than the predetermined value of the whole blended coal.
It is preferable to pulverize so as to increase the weight%. If it is less than 3% by weight, the amount of coarse particles causing cracks becomes relatively large, and the coke strength decreases. On the other hand, 12% by weight
If the pulverization is too fine to exceed the above, the amount of fine powder increases and the coke strength also decreases.

The coal of the group of low-reflectance non-coking coal is further pulverized so that the ratio of particles having a size of 0.5 mm or less is 40% by weight or less, so that the coke strength due to excessive fine powder is reduced. The decrease can be further suppressed.

Further, as described above, the coke strength of the high-reflectivity non-finely caking coal decreases even if coarse particles or fine particles increase. As mentioned above, this coal has good crushability,
The generation of coarse particles is suppressed without finely pulverizing unlike low-reflectance non-sintered coal. Therefore, it is preferable that the pulverization of the coal is limited to the target value of the particle size of the entire blended coal, and the increase of the fine powder is suppressed on the contrary. That is, it is preferable that the coal of the group of the high-reflectance non-coking coal is pulverized so that the ratio of the particles having a size of 3 mm or less is within ± 3% by weight of the target particle size. If the content is less than -3% by weight, coarse particles causing cracks increase and coke strength decreases as described above. If the content exceeds + 3% by weight, fine powder increases as described above, and the coke strength also decreases.

The coal of the group of high-reflectivity non-sintered coal is further pulverized so that the particle ratio of 0.5 mm or less is 45% by weight or less, whereby the low-reflectance non-sintered coal is reduced. As in the case, a decrease in coke strength due to excessive fine powder can be further suppressed.

Further, as described above, coking coal has good coking properties, so that the decrease in coke strength due to an increase in coarse particles or fine powder is small. However, as described above, the low-reflectance non-fine coking coal is pulverized finer than the target particle size of the entire blended coal, and consequently, the coking coal is preferably pulverized coarser than the target particle size of the whole. That is, the caking coal is preferably pulverized so that the ratio of particles having a size of 3 mm or less is 3 to 12% by weight lower than a predetermined value, contrary to the non-reflective non-micro caking coal. By doing so, the particle size distribution of the entire blended coal can be maintained at a predetermined target particle size value. In other words, it is desirable to adjust the particle size distribution of the entire blended coal by adjusting the particle size of the caking coal.

[0024]

EXAMPLES (Examples 1 to 3) Coal for charging a coke oven was produced from 12 types of coals, and the coal was carbonized to produce coke. The target particle size of the entire charging coal is 3
The ratio of particles having a diameter of not more than mm was 76% by weight. First, coal of each brand was classified into three groups: low-reflectivity non-slightly caking coal, high-reflectance non-slightly caking coal, and caking coal. Then, for each group, coal of each brand was blended under predetermined blending conditions. Next, for each group, the blended coal was pulverized to realize three types of particle size distributions shown in Table 1 below. The particle size distribution was adjusted by adjusting the rotation speed and the gap of the blade of the crusher.

[0025]

[Table 1]

Next, the pulverized coal of each group was mixed with
The mixture was mixed at a ratio of 1: 1 and almost reached the target particle size (3 mm
The following coal was charged at a proportion of 76% by weight).
Finally, the charging coal thus produced was charged into a coke oven and then carbonized to produce coke.

In each of the examples, as shown in Table 1 above, the ratio of the particles having a size of 3 mm or less in the low-reflectance non-coking coal is 3 to 12% by weight higher than the target particle size and 0.5 mm or less. Was 40% by weight or less. In addition, particles of 3 mm or less of high reflectance non-sintered coal are the same as the target value,
0.5 mm or less was set to 45% by weight or less. Furthermore, 3 mm or less of the caking coal was set to be 3 to 10% by weight lower than the target value.

(Comparative Examples 1 to 4) In the same manner as in Example 1 except that the particle size distribution of each group after pulverization was changed to the four types shown in Table 1, the target value of the particle size (the ratio of particles having a particle size of 3 mm or less was substantially reduced) was obtained. (76% by weight) and coal was carbonized by carbonization. As shown in Table 1 above, in each comparative example, the ratio of particles having a size of 3 mm or less in the low-reflectance non-sintered coal was set to be equal to or less than the overall target value.

Examples 1 to 3 manufactured as described above,
The drum strength of each coke of Comparative Examples 1 to 4 was measured. The measurement conditions were DI ³⁰ ₁₅ (particle size 1 remaining after 30 rotations of the drum).
5% or more of particles). FIG. 2 shows the measurement results. All the cokes of the examples clearly showed higher strength than the coke of the comparative example, and the effect of the present invention was confirmed.

[0030]

According to the present invention, it is possible to provide a method for preparing coal for charging a coke oven, which can obtain high-strength coke. As a result, when the present invention is used, the current coke strength can be maintained even if the amount of non-coking coal which is inexpensive but low-grade coal is increased, so that the cost of coking coal can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a measurement result between a hard glove grindability index (HGI) and a maximum average reflectance of coal.

FIG. 2 is a view showing measurement results of coke drum strength in Examples and Comparative Examples.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Izumi Shimoyama, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Inside Nihon Kokan Co., Ltd. (72) Toshiharu Nonaka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan (72) Inventor Masaaki Maruoka 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Japan Nippon Kokan Co., Ltd. (72) Takuya Tomooka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Steel Tube Co., Ltd. F-term (reference) 4H012 MA01 QA04

Claims (3)

[Claims] 1. A process of classifying coal of a plurality of brands into three or more groups having different coking properties, a process of blending coal for each group, and a process of pulverizing and blending coal blended for each group. A method for preparing coal for charging a coke oven, comprising: a step of setting a particle size according to the properties; and a step of mixing coals of all groups. 2. In the classifying step, the coal is classified into low-reflectivity non-slightly caking coal, high-reflectance non-slightly caking coal and caking coal, and in the pulverizing step, coals of all groups are classified. In order to keep the overall particle size distribution after mixing at a predetermined value, the coal of the group of low-reflectance non-coking coals has a particle ratio of 3 mm or less 3 to 12% by weight higher than the predetermined value. And pulverizing the coal of the group of the high-reflectance non-coking coals so that the ratio of particles of 3 mm or less is within ± 3% by weight of the predetermined value. The method for preparing coal for charging a coke oven according to claim 1, wherein the coal is pulverized so that the ratio of particles having a size of 3 mm or less is 3 to 12% by weight lower than the predetermined value. 3. The pulverizing step further comprises pulverizing the coal of the group of low-reflectivity non-coking coals so that the ratio of particles having a size of 0.5 mm or less is 40% by weight or less. The method for preparing coal for charging a coke oven according to claim 2, wherein the coal of the group of finely caking coal is pulverized so that the ratio of particles having a size of 0.5 mm or less is 45% by weight or less.