Method for evaluating segregation of molded coal and method for producing coke

Abstract

This invention provides a method for evaluating the segregation of molten coal in a coal tower, which allows for the appropriate determination of the proportion of molten coal present around the furnace lid, and a method for producing coke that appropriately controls the proportion of molten coal present around the furnace lid. [Solution] A method for evaluating the segregation of molded coal around the furnace lid of a coke oven, comprising a first evaluation performed using a segregation testing device and a second evaluation performed using a coal tower and a coal charging car, wherein the degree of segregation is determined as the first evaluation, the corrected overall molded coal mass ratio is determined as the second evaluation, the corrected molded coal mass ratio around the furnace lid is determined using the obtained degree of segregation and the corrected overall molded coal mass ratio using the formula D=A / E (where D is the degree of segregation, A is the molded coal mass ratio around the furnace lid, and E is the overall molded coal mass ratio), and the corrected degree of segregation considering the segregation of molded coal in the coal tower is determined using the obtained corrected molded coal mass ratio around the furnace lid and the overall molded coal mass ratio of raw coal.

Description

Technical Field

[0001] The present invention relates to a method for evaluating segregation of formed coke and a method for producing coke.

Background Art

[0002] Conventionally, in the production of coke used in blast furnace operation, various methods have been studied to maintain good coke strength while increasing the blending ratio of inferior coke such as non-binder coke in the blended coke composed of formed coke and pulverized coal. In order to obtain a desired coke strength using a blended coke containing inferior coke, a pre-treatment process for coal is useful.

[0003] One of the pre-treatment processes for coal, the formed coke blending method, can improve the bulk density of the whole raw coal by blending formed coke with high density, and can improve the coke strength. Also, by utilizing the high density of the formed coke, it is possible to intensively blend inferior coke into the formed coke without reducing the coke strength. The formed coke blending method can also be combined with other coal pre-treatment processes such as a drying process and a pulverized particle size adjustment method.

[0004] It has also been proposed to suppress gas leakage in a coke oven using formed coke. For example, in Patent Document 1, a method for producing coke is proposed in which the entire amount of charged raw materials is formed coke in order to improve the productivity of coke, reduce gas leakage from the coke oven lid, and increase the ratio of inferior coke in the coke raw materials.

[0005] Also, in Patent Document 2, it is found that the cause of gas leakage from the lid is that the gas pressure in the gas passage space between the lid and the furnace wall becomes high in the initial stage of carbonization, and a method for producing coke is proposed in which formed coke is concentrated and charged near the lid at the bottom of the coke oven to function as a spacer to reduce the gas pressure and suppress gas leakage.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Publication No. 2000-282051 [Patent Document 2] Japanese Patent Application Publication No. 6-212162 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In the method described in Patent Document 1, since all the raw coal is molded coal, all the raw coal present near the furnace lid is molded coal. Similarly, in the method described in Patent Document 2, a large amount of molded coal is present near the furnace lid. When there is an excessive amount of molded coal near the furnace lid, carbon derived from the binder contained in the molded coal can adhere to the furnace lid bricks, which can reduce the sealing performance of the furnace lid. This reduced sealing performance makes gas and tar leaks from the furnace lid more likely. In addition, if carbon derived from molded coal adheres to the riser pipe of the coke oven and obstructs the gas flow, it can cause gas leaks from the furnace lid. Therefore, when using molded coal, it is desirable to appropriately understand and control the amount of molded coal charged around the furnace lid of the coke oven.

[0008] Furthermore, while various types of molded coal are used in coke production in coke ovens, it is desirable to appropriately control the ratio of molded coal around the oven lid during coke production to prevent an increase in carbon buildup, gas leaks, and tar leaks, even when the type of molded coal being charged is changed.

[0009] Furthermore, segregation of molten coal can occur not only within the coke oven but also in the coal tower where coal to be charged into the coke oven is temporarily stored. Coal stored in the coal tower is fed into multiple charging hoppers of the coal charging car from multiple charging ports aligned along the length of the coke oven, and then charged into the coke oven from discharge ports below the charging hoppers. If molten coal segregates in the coal tower at charging ports corresponding to the coke oven lid, more molten coal will be charged into the charging hoppers closer to the coke oven lid, resulting in a greater amount of molten coal present around the coke oven lid compared to other areas. However, conventionally, the uneven distribution of molten coal in the coal tower has not been adequately considered.

[0010] Therefore, the present invention aims to provide a method for evaluating the segregation of molten coal in a coke oven, which allows for the appropriate determination of the proportion of molten coal present around the furnace lid, taking into account the segregation of molten coal in the coal tower. Furthermore, it aims to provide a method for producing coke that appropriately controls the proportion of molten coal present around the furnace lid, taking into account the segregation of molten coal in the coal tower. [Means for solving the problem]

[0011] This application was made to solve the above-mentioned problems, and its gist is as follows.

[0012] (1) A method for evaluating the segregation of molten coal around the lid of a coke oven, comprising a first evaluation using a segregation test apparatus and a second evaluation using a coal tower and charging car for charging raw coal into the coke oven, The segregation testing apparatus comprises a hopper for containing raw coal including pulverized coal and molded coal, and a sample box into which the raw coal is charged from the hopper. The sample box is rectangular in shape, corresponding to the area near the furnace lid of the carbonization chamber of a coke oven, with one end corresponding to the furnace lid position and the other end corresponding to the coal charging position of the hopper. It is divided into multiple sections in the length and height directions from one end to the other. The coal tower has multiple charging ports for charging into multiple charging hoppers of the coal charging car, the charging ports and charging hoppers are arranged in the furnace length direction of the coke oven, raw coal is charged into the corresponding charging hoppers from the charging ports, and raw coal is discharged from the respective discharge ports of the charging hoppers. As the first evaluation, the raw coal to be tested is dropped from the hopper of the segregation test apparatus and loaded into the sample box. The ratio of molded coal contained in the raw coal loaded into the furnace lid area section, which is the section closest to one end of the sample box, is determined. Using the determined furnace lid area molded coal mass ratio and the total molded coal mass ratio, which is the blending ratio of molded coal in the entire raw coal, the degree of segregation, which indicates the degree of segregation of molded coal to the furnace lid area, is determined by the following formula (I). As the second evaluation, the target coking coal is loaded into the coal tower, the coking coal is discharged from each outlet of the coal charging car and collected, the molten coal mass ratio, which is the ratio of molten coal contained in the collected coking coal, is determined for each outlet, the ratio of the molten coal mass ratios for each outlet is determined, the maximum ratio, which is the larger ratio among the ratios of the molten coal mass ratios corresponding to the outlets at both ends, and the uniform ratio, which is the ratio of the molten coal mass ratios for each outlet assuming that molten coal is discharged without variation from each outlet, the coal tower segregation rate, which is the ratio of the maximum ratio to the uniform ratio is determined, and the corrected overall molten coal mass ratio, which takes into account the segregation of molten coal in the coal tower, is obtained by multiplying the overall molten coal mass ratio of the coking coal and the coal tower segregation rate. Using the degree of segregation obtained in the first evaluation and the corrected overall molded coal mass ratio obtained in the second evaluation, the corrected molded coal mass ratio around the furnace lid, taking into account the segregation of molded coal in the coal tower, is calculated using the following formula (I): A method for evaluating segregation of molded coal, characterized by determining the corrected degree of segregation considering segregation of molded coal in the coal tower using the following formula (I), with the corrected mass ratio of molded coal around the furnace lid and the total mass ratio of molded coal of the raw coal. D = A / E (I) In equation (I), D is the degree of segregation, A is the mass ratio of molded coal around the furnace lid, and E is the total mass ratio of molded coal.

[0013] (2) Determine the corrected degree of segregation of the target molten coal to be charged into the coke oven using the segregation evaluation method for molten coal described in (1) above. For a reference molded coal used as a basis for determining the overall molded coal mass ratio, which is the blending ratio in the raw coal of the target molded coal, the tar addition rate, which is the mass ratio of tar added during the production of the molded coal, is the same as that of the target molded coal. Substitute the corrected molded coal mass ratio around the furnace lid, obtained by the segregation evaluation method of the molded coal, and the corrected degree of segregation of the target molded coal into formula (I) to determine the overall molded coal mass ratio. A method for producing coke, characterized by using raw coal in which the target molded coal is blended at the determined total molded coal mass ratio. [Effects of the Invention]

[0014] According to this invention, it is possible to provide a method for evaluating the segregation of molten coal to appropriately determine the ratio of molten coal present around the furnace lid of a coke oven, taking into account the segregation of molten coal in the coal tower. Furthermore, it is possible to provide a method for producing coke that appropriately controls the ratio of molten coal present around the furnace lid, taking into account the segregation of molten coal in the coal tower. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram showing the configuration of the segregation testing apparatus according to the embodiment. [Figure 2] This figure shows the mass ratio of molded charcoal in each section of sample box 4 as determined in the example. [Modes for carrying out the invention]

[0016] This embodiment will be described with reference to the drawings. This embodiment includes a method for evaluating the segregation of molded coal and a method for manufacturing coke. The method for evaluating the segregation of molded coal is a method for appropriately evaluating the degree to which molded coal segregates around the furnace lid, taking into account the segregation of molded coal in the coal tower when raw coal mixed with molded coal is charged into a coke oven. The method for manufacturing coke is a method for manufacturing coke by appropriately controlling the ratio of molded coal charged around the furnace lid, using the evaluation results from the method for evaluating the segregation of molded coal, which takes into account the segregation of molded coal in the coal tower. With the method for manufacturing coke of this embodiment, it is possible to manufacture coke by mixing the desired amount of molded coal while appropriately controlling the segregation of molded coal around the furnace lid, which can cause gas leakage and tar leakage from the furnace lid of the coke oven.

[0017] Here, the "segregation" of the formed coal in the present embodiment means that the ratio of the formed coal existing in a specific range in the carbonization chamber of the coke oven is higher than the ratio of the formed coal in the entire carbonization chamber, and the formed coal is unevenly distributed in that range. Further, the "segregation" of the formed coal in the present embodiment includes the segregation of the formed coal in the coal tower as described above. In the present embodiment, unless otherwise specified, "segregation" means that the formed coal is unevenly distributed around the furnace lid in the carbonization chamber, or that the formed coal is unevenly distributed at the charging port (nearby) corresponding to the furnace lid side of the coke oven in the coal tower.

[0018] In the present embodiment, the ratio of the formed coal (and other coals) means the ratio on a mass basis unless otherwise specified. For example, when the mass ratio of the formed coal in the raw coal (blended coal) around the furnace lid is higher than the mass ratio of the formed coal in all the raw coal in the carbonization chamber, it can be said that the formed coal is segregated around the furnace lid.

[0019] (Segregation evaluation method) The segregation evaluation method of the formed coal will be described. The segregation evaluation method of the present embodiment is roughly divided into 1) Evaluation of segregation using a segregation test device (first evaluation), 2) Evaluation of segregation using a coal tower and a coal charging car (second evaluation), 3) Evaluation of the segregation of the formed coal based on the evaluations of 1) and 2), including three steps. In the step of 1), the segregation of the formed coal in the coke oven is evaluated. For this purpose, the degree of segregation is calculated using a segregation test device. In the step of 2), the segregation of the formed coal in the coal tower is evaluated. For this purpose, the degree of segregation of the formed coal is evaluated using a coal tower and a coal charging car, and the overall formed coal mass ratio (blending ratio) is calculated considering the degree of segregation. In the step of 3), the degree of segregation considering the segregation of the formed coal in the coal tower is calculated using the degree of segregation obtained in 1) and the overall formed coal mass ratio obtained in 2). The order of the steps of 1) and 2) is not particularly limited, and either may be performed first, or they may be performed in parallel. Hereinafter, each step will be described in detail.

[0020] <1) Evaluation of segregation using a segregation test device> First, we will describe the segregation testing apparatus 1 used to perform segregation evaluation in step 1). Figure 1 is a schematic diagram showing the configuration of the segregation testing apparatus 1 of this embodiment. The segregation testing apparatus 1 reproduces the charging conditions of raw coal around the furnace lid in the carbonization chamber of a coke oven. By conducting tests using the segregation testing apparatus 1, it is possible to determine the degree of segregation, which indicates the degree to which the target molded coal is segregated around the furnace lid in the coke oven.

[0021] The segregation test apparatus 1 includes a hopper 2 and a sample box 4. Hopper 2 simulates the hopper closest to the furnace lid of the carbonization chamber among the multiple hoppers on the charging car of an actual coke oven. Hopper 2 only needs to be large enough to hold the amount of raw coal to be charged into the sample box 4. In hopper 2, as in an actual coke oven, molded coal and powdered coal should be loaded alternately in layers to prevent the molded coal from being unevenly loaded into the furnace. When the gate plate 6 is opened, the raw coal can be loaded into the sample box 4. Hopper 2 is supported above the sample box 4 by, for example, a platform 8 that movably supports hopper 2. The segregation apparatus 1 may also be equipped with a guide frame 10. The guide frame 10 guides the loading of raw coal from hopper 2 to the sample box 4.

[0022] Sample box 4 is a box used to simulate the charging of raw coal around the furnace lid near the bottom of a coke oven. Sample box 4 is a rectangular parallelepiped and corresponds to the furnace bottom side portion around the furnace lid inside the carbonization chamber. Sample box 4 has an open top. The internal dimensions of sample box 4 can be, for example, 1100 mm in height (H), 1050 mm in length (L), and 450 mm in width (W). The width is preferably the same as the width of the carbonization chamber of an actual furnace (for example, 400 mm to 600 mm). The height and length can be 1000 mm or larger, and can be smaller than an actual furnace. The height, length, and width directions of sample box 4 correspond to the height direction of the carbonization chamber, the longitudinal direction which is the furnace length, and the width direction which is the furnace group length of the coke oven.

[0023] The sample box 4 is divided into multiple sections in a grid pattern. In this embodiment, the sample box 4 has a total of 16 sections: 4 layers in the height direction, 4 columns in the length direction, and 1 column in the width direction. Each section may have the same dimensions as the others. For example, in the case of the sample box 4 with the above dimensions, one section may be 250 mm high, 262.5 mm long, and 450 mm wide. The shape of one section is preferably square when viewed from the width direction. That is, it is preferable that the dimensions in the height direction and the length direction are the same. Note that the dimensions of each section are not limited to the above size; the length and height may be about twice the above length, for example, they can be set to an appropriate size in the range of 250 mm to 530 mm. Also, the number of sections in the sample box 4 is not limited to the above number; for example, it can be an appropriate number of sections in the range of 2 layers in the height direction × 2 columns in the length direction to 4 layers × 4 columns, and the number of sections in the height direction and the length direction may differ. The width direction may be one section.

[0024] One end of the sample box 4 corresponds to the furnace lid position, and the other end corresponds to the coal charging position of the hopper 2. Raw coal is loaded into the sample box 4 by free-falling from the hopper 2, which is located above the sample box 4. The hopper 2 should be filled with enough raw coal to completely fill the sample box 4, which has the dimensions described above.

[0025] Then, of the divisions in the sample box 4, the division of the first row, which is the row closest to the furnace lid position at one end, is considered to be the area around the furnace lid in the coke oven, and the degree of segregation of the molded coal is evaluated for this division. In this embodiment, the division of the first row that is considered to be the area around the furnace lid in the sample box 4 is also referred to as furnace lid area division a (shown by the dashed frame in Figure 1).

[0026] The procedure for calculating the degree of segregation using the segregation testing apparatus 1 is explained below. First, raw coal is loaded into the sample box 4 from the hopper 2. The raw coal is the raw coal whose degree of segregation of molded coal is to be evaluated. The loaded raw coal is sampled from each section of the sample box 4. Specifically, for example, the sample box 4 is provided with slits so that partitions can be inserted, and partitions are inserted into the slits to prevent coal from other sections from being mixed in during sampling. Then, all the raw coal from each section separated by the partition is collected from the top of the sample box 4. After sampling the upper layer is finished, the partition is removed and sampling of the lower layer is performed, and this process is repeated to collect raw coal from each section. Then, the mass of the raw coal and the mass of molded coal within it are measured for each sample section. The mass of molded coal can be measured by extracting only the molded coal from the sample and measuring its mass.

[0027] Next, based on the mass of raw coal and the mass of molded coal in each obtained section, the mass ratio of molded coal around the furnace lid can be determined using the following formula (1). The mass ratio of molded coal around the furnace lid is the ratio of molded coal contained in the raw coal charged into section a around the furnace lid.

[0028] The ratio of molded coal mass around the furnace lid A = Total mass of molded coal in section a around the furnace lid B ÷ Total mass of raw coal in section a around the furnace lid C (1) In this embodiment, the total mass B of molded coal is the sum of the masses of molded coal in each section from the first to the fourth layer of the first row, and the total mass C of raw coal is the sum of the masses of raw coal in the same section.

[0029] Using the mass ratio A of molded coal around the furnace lid obtained by formula (1) above, and the total mass ratio of molded coal, which is the blending ratio of molded coal in the total raw coal, the degree of segregation of the target molded coal can be determined by formula (2) below. The degree of segregation is a value that indicates the degree to which the target molded coal is segregated around the furnace lid.

[0030] Segregation degree D = Mass ratio of molded coal around the furnace lid A ÷ Total mass ratio of molded coal E (2) Here, the total molded coal mass ratio E is the ratio of the mass of molded coal to the total mass of raw coal charged into hopper 2, and represents the blending ratio of molded coal to raw coal.

[0031] A segregation degree of 1 means that the mass ratio of molded coal around the furnace lid is equal to the total mass ratio of molded coal, and that no segregation of molded coal has occurred around the furnace lid. A segregation degree greater than 1 means that segregation has occurred around the furnace lid.

[0032] The inventors confirmed that the mass ratio A of molded coal around the furnace lid, obtained by the segregation evaluation method using the segregation test apparatus 1 described above, was no different from the mass ratio of molded coal around the furnace lid obtained by the actual furnace segregation test apparatus (height 7210 mm × length 8144 mm × width 450 mm). Specifically, in the actual furnace segregation test apparatus, the furnace lid and the loading inlet are about 2000 mm apart, with the area around the furnace lid being defined as the area approximately 1000 mm from the furnace lid, and the area from approximately 1000 to 3000 mm from the furnace lid, with the loading inlet in between, being defined as the area directly below the loading inlet. In the large-scale segregation test apparatus for a real furnace, the total mass ratio of molded coal and the mass ratio of molded coal around the furnace lid were determined for the raw coal charged around the furnace lid and directly below the charging port. In a graph with the total mass ratio of molded coal on the horizontal axis and the mass ratio of molded coal around the furnace lid on the vertical axis, the results from the large-scale segregation test apparatus for a total molded coal mass ratio of 20-40% were compared with the results from segregation test apparatus 1, and it was confirmed that there was no difference. Therefore, the degree of segregation of molded coal can be evaluated accurately using segregation test apparatus 1. The above is the flow of the process for calculating the degree of segregation as an evaluation using segregation test apparatus 1.

[0033] <2) Evaluation of segregation using coal towers and coal-charging cars> Next, we will explain the evaluation of segregation in the coal tower. The coal tower and charging car used for the evaluation are equipment for charging coking coal into the coke oven. The coal tower has multiple charging ports arranged in the direction of the coke oven's furnace length, and the charging car also has multiple charging hoppers arranged in the direction of the furnace length. The same number of charging ports and charging hoppers (and their discharge ports) are arranged. As described above, the coking coal stored in the coal tower is fed from each charging port into the corresponding charging hopper of the charging car, and then charged into the coke oven from the discharge port below each charging hopper. Therefore, the degree of segregation of molten coal at each charging port of the coal tower is the same as the degree of segregation in the corresponding charging hopper. Thus, by evaluating the mass ratio of molten coal in the coking coal discharged from the discharge port of the charging car, it is possible to evaluate the segregation of molten coal at each charging port of the coal tower. If segregation of molten coal occurs in the coal tower, it may affect the segregation of molten coal around the furnace lid when it is finally charged into the coke oven. Therefore, in this embodiment, segregation in the coal tower is evaluated along with the segregation in the coke oven described above, and a blending ratio (corrected overall coal mass ratio E' described later) is calculated that takes into account the degree of segregation in the coal tower.

[0034] To evaluate the segregation of molten coal in a coal tower, first, raw coal is loaded into the actual coal tower and charging car in the same manner as during normal operation. Then, a small amount of raw coal is discharged from each outlet of the charging car, and the discharged raw coal is collected from each outlet. There are no particular limitations on the amount discharged or collected, but it is preferable to collect 50 kg or more, and it is sufficient to discharge an amount greater than or equal to the amount collected. It is also desirable that the amount collected from each outlet be of a similar mass. Next, the molten coal mass ratio of each sample collected from each outlet is determined. The molten coal mass ratio of each sample from each outlet can be determined by measuring the mass of raw coal and the mass of molten coal within it for each sample, as in the case of segregation test apparatus 1, and calculating (mass of molten coal) ÷ ​​(mass of raw coal). Then, the ratio of the molten coal mass ratios for each outlet determined is calculated. For example, if a coal tower has four loading ports and four discharge ports for the coal charging car, and the molten coal mass ratio of the raw coal discharged from each discharge port is the same (for example, 30% for all), then if the sum of the ratios is 1, the ratio of the molten coal mass ratio for each discharge port will be divided equally into four parts, resulting in 0.25 for each. If the ratio for any of the discharge ports is greater than 0.25, it can be concluded that the molten coal is segregated at the coal tower loading port corresponding to that discharge port.

[0035] Next, we identify the maximum ratio, which is the larger of the ratios of molten coal mass ratios at both ends of the discharge port. We also determine the uniformity ratio, which is the ratio of molten coal mass ratios at each discharge port, assuming that the molten coal is discharged uniformly without variation, that is, when the molten coal mass ratio in the raw coal discharged from each discharge port is the same. The sum of the uniformity ratios is set to the same value as the sum of the ratios of molten coal mass ratios obtained from the sample. Finally, we determine the ratio of the maximum ratio to the uniformity ratio (maximum ratio / uniformity ratio). This ratio represents how much larger the maximum ratio is compared to the uniformity ratio, and indicates the maximum degree of segregation occurring in the coal tower. Hereafter, this ratio will also be referred to as the "coal tower segregation rate". The reason for using the larger of the ratios of molten coal mass ratios at both ends is as follows: Raw coal discharged from the discharge ports at both ends of the charging car, which correspond to the furnace lid sides at both ends of the coke oven, is charged and accumulates around the furnace lid of the coke oven, affecting the segregation of molten coal around the furnace lid. Therefore, to evaluate segregation around the furnace lid, it is best to evaluate the ratio of molten coal mass at the outlets at both ends of the coal charging car. Then, from the perspective of preventing tar leakage, etc., it is sufficient to consider the largest segregation, so by considering the segregation in the coal tower based on the outlet that contains more molten coal, the segregation can be appropriately evaluated. For example, suppose in the example with four outlets as described above, the ratio of the outlets on both sides is 0.28 and 0.30. In that case, the maximum ratio is 0.30 and the uniform ratio is 0.25, so the coal tower segregation rate can be calculated as 0.30 ÷ 0.25 = 1.2.

[0036] Furthermore, depending on factors such as the collapse of molten coal during transport and the inventory level in the coal tower, the mass ratio of molten coal discharged from the charging car's outlet may change from the original manufacturing blend ratio, making it difficult to evaluate the degree of segregation based solely on the molten coal's mass ratio. However, by using ratios, it is possible to appropriately evaluate the degree of segregation based on the uniform ratio, regardless of fluctuations in the overall molten coal mass ratio within the coal tower or charging car. Therefore, by using the ratio of molten coal mass ratios at each outlet and its maximum ratio, the degree of segregation of molten coal when it is actually discharged from the outlet can be appropriately evaluated.

[0037] Next, the corrected overall molten coal mass ratio E', which takes segregation in the coal tower into account, is calculated by multiplying the calculated coal tower segregation rate by the overall molten coal mass ratio E, which is the blending ratio of molten coal in the raw coal. In other words, (overall molten coal mass ratio E) × (coal tower segregation rate) = (corrected overall molten coal mass ratio E') is calculated. If segregation occurs in the coal tower, the raw coal will be charged with an increased molten coal mass ratio as a result of that segregation. Therefore, by multiplying the coal tower segregation rate, which is an indicator of how much the molten coal has increased compared to when there is no segregation, by the original blending ratio, the overall molten coal mass ratio, the corrected overall molten coal mass ratio, which takes segregation in the molten coal into account, can be obtained. Furthermore, in order to avoid worsening gas leaks and tar leaks from the furnace lid, it is desirable to know the maximum value of the exhaust ports at both ends. Assuming that the molten coal is transported to the coal tower without collapsing during the transport process, and that there is no fluctuation in the molten coal mass ratio discharged from the charging car's outlet according to the coal inventory level, the corrected overall molten coal mass ratio E' can be calculated by using the blending ratio (overall molten coal mass ratio E) during raw coal production as the overall molten coal mass ratio of the coal tower. For example, if the overall molten coal mass ratio E (blending ratio) is 30% and the coal tower segregation rate is 1.2, the corrected overall molten coal mass ratio E' can be calculated as 30% × 1.2 = 36%. Furthermore, if the yield of molten coal, including collapse during the transport process, and the fluctuation in the molten coal mass ratio discharged from the charging car's outlet according to the coal inventory level are known, it is more desirable to calculate the corrected overall molten coal mass ratio E' by considering either or both the yield of molten coal and the fluctuation in the molten coal mass ratio discharged from the charging car's outlet in the blending ratio (overall molten coal mass ratio E) during raw coal production. In the example, the yield of molten coal was considered.

[0038] <3) Evaluation of segregation of molded charcoal based on evaluations 1) and 2)> Next, using the degree of segregation D obtained in step 1) and the corrected overall molded coal mass ratio E' obtained in step 2), the corrected molded coal mass ratio A' considering segregation of the coal tower is calculated using the above formula (2) (degree of segregation D = molded coal mass ratio A around the furnace lid ÷ overall molded coal mass ratio E). The corrected molded coal mass ratio A' around the furnace lid is the molded coal mass ratio around the furnace lid obtained by multiplying (E' × D) by the degree of segregation D obtained by the segregation test apparatus 1 in step 1), assuming that raw coal blended with the corrected overall molded coal mass ratio E' as the blending ratio. For example, if the corrected overall molded coal mass ratio E' is 36% as described above, and the degree of segregation D obtained using the segregation test apparatus 1 is 1.33, then the corrected molded coal mass ratio A' around the furnace lid is calculated as E' × D = 36% × 1.33 = 47.88%.

[0039] Next, using the corrected mass ratio of molded coal around the furnace lid A' and the overall mass ratio of molded coal E (mixing ratio of raw coal), the corrected degree of segregation D', considering segregation of molded coal in the coal tower, is calculated from equation (2) above. In the example above, the overall mass ratio of molded coal E of the raw coal is 30%, so the corrected degree of segregation D' is calculated as A'÷E=47.88%÷30%=1.596. The calculated corrected degree of segregation D' is the degree of segregation if the initial mixing ratio (overall mass ratio of molded coal E) is corrected to account for segregation in the coal tower, and the molded coal is charged into the coke oven with that corrected overall mass ratio of molded coal E'. It is the degree of segregation of molded coal around the furnace lid that reflects segregation in the coal tower.

[0040] The above is the flow of the segregation evaluation method of this embodiment. According to this segregation evaluation method, when segregation of molten coal occurs in a coal tower, the segregation of molten coal around the coke oven lid can be appropriately evaluated by taking into account the segregation of molten coal in that coal tower.

[0041] (Method of producing coke) Next, the coke manufacturing method of this embodiment will be described. The coke manufacturing method involves determining the overall molded coal mass ratio (molded coal blending ratio) that results in an appropriate value for the molded coal mass ratio around the furnace lid when using raw coal (target raw coal) blended with a desired molded coal (target molded coal), and then manufacturing coke using raw coal blended with the target molded coal at the determined ratio. The overall molded coal mass ratio of the target molded coal is set using the corrected molded coal mass ratio A' around the furnace lid of raw coal (reference raw coal) blended with a standard molded coal (reference molded coal).

[0042] The tar addition rate, which is the mass ratio of tar added during the production of molded charcoal, is common to both the standard molded charcoal and the target molded charcoal. This tar addition rate during molded charcoal production is calculated as (mass of tar added during molded charcoal production) ÷ (total mass of molded charcoal) × 100.

[0043] The following describes the process for manufacturing coke according to this embodiment. As an example, the standard molten coal is described as the molten coal currently used in coke production in a coke oven, and the target molten coal is described as the molten coal to be used next. It is assumed that carbon deposition, resulting gas leakage, and tar leakage are adequately suppressed in coke production using the current standard raw coal. The blending ratio of the target molten coal (overall molten coal mass ratio E) is determined so that the mass ratio of molten coal around the furnace lid of the target molten coal to be used next is equivalent to the mass ratio of molten coal around the furnace lid of the current standard molten coal (corrected mass ratio of molten coal around the furnace lid A').

[0044] Specifically, the corrected segregation degree D' of the target molded coal in the target coking coal is determined using the segregation evaluation method described in steps 1) to 3) above, which utilizes the segregation testing apparatus 1 and the coal tower / charging car. It has been confirmed that the segregation degree D and the corrected segregation degree D' hardly change with a change of about 5% in the blending ratio of molded coal (total molded coal mass ratio E), however, it is preferable that the blending ratio of the target molded coal in the test be the same as the blending ratio of the standard molded coal.

[0045] Similarly, the corrected mass ratio A' of molded coal around the furnace lid of the standard molded coal in the standard coking coal is determined using the segregation evaluation method described above. Note that the order in which the steps for determining the corrected segregation degree D' of the target molded coal and determining the corrected mass ratio A' of molded coal around the furnace lid of the standard molded coal are performed is not limited; either may come first, or they may be performed in parallel.

[0046] Then, the corrected mass ratio of molded coal around the furnace lid of the standard molded coal A' and the corrected degree of segregation of the target molded coal D' are substituted into equation (2) to obtain the total mass ratio of molded coal E. In other words, (total mass ratio of molded coal E) can be calculated as (corrected mass ratio of molded coal around the furnace lid of the standard molded coal A') ÷ (corrected degree of segregation of the target molded coal D'). In order to make the mass ratio of molded coal around the furnace lid A after switching to the target molded coal equivalent to the current corrected mass ratio of molded coal around the furnace lid A' of the standard molded coal, the calculation is performed using the corrected mass ratio of molded coal around the furnace lid A' of the standard molded coal and the corrected degree of segregation of the target molded coal D'. Then, the target molded coal is blended with the obtained total mass ratio of molded coal E, and coke is produced using the blended raw coal.

[0047] For example, if the corrected mass ratio A' of molten coal around the furnace lid of the current standard molten coal is 50%, and the corrected segregation degree D' of the target molten coal is 1.5, then the total mass ratio E of the target molten coal can be calculated as A'÷D'=50÷1.5≈33.3%. In this case, if coke production is carried out using raw coal blended with 33.3% of the target molten coal, the mass ratio of molten coal around the furnace lid can be made equivalent to the mass ratio of molten coal around the furnace lid of the standard raw coal currently in use (corrected mass ratio A' of molten coal around the furnace lid).

[0048] Therefore, according to the method of this embodiment described above, coke can be produced using raw coal blended with the desired molded coal in a blending ratio that results in an appropriate mass ratio of molded coal around the furnace lid, taking into account the segregation of molded coal in the coal tower. In current coke ovens using standard raw coal, if there is no carbon buildup and associated gas and tar leaks, or if they are suppressed to an appropriate level, the mass ratio of molded coal around the furnace lid can be made equivalent to that of the standard molded coal even when switching to the desired target molded coal. Thus, coke can be produced without increasing carbon buildup, gas leaks, or tar leaks. [Examples]

[0049] <Example 1: Evaluation of segregation of molded charcoal using a segregation testing apparatus> The degree of segregation was determined for multiple molded charcoal samples using segregation testing apparatus 1.

[0050] (Coal used) For the coking coal mixture, powdered coal with a particle size of approximately 85% below 3mm sieve weight and a moisture content of 10% by mass was used. Molded coal was produced by molding powdered coal with a particle size of 90% below 3mm sieve weight using a double-roll molding machine. In the production of molded coal, a tar-based binder was used as a liquid binder, and asphalt pitch (ASP) was used as a solid binder.

[0051] (Volume evaluation of molded charcoal) The volume (actual volume) of the prepared molded charcoal was determined using a small-scale apparent density measurement method. The volumes of the two types of molded charcoal prepared, a) and b), are shown in Table 1.

[0052] [Table 1]

[0053] (Evaluation of segregation of molded coal in a coke oven using a segregation testing apparatus) For each type of molded coal blended into the raw coal, segregation evaluation was performed using segregation testing apparatus 1, and the degree of segregation D in the coke oven, which can be determined by formula (2) above, was calculated. Segregation testing apparatus 1 is the apparatus shown in Figure 1 described in the above embodiment, and the internal dimensions of the sample box 4 are 1100 mm in height, 1050 mm in length, and 450 mm in width. The sample box 4 is divided into 16 sections, with 4 rows in the length direction and 4 layers in the height direction, and the dimensions of one section are 250 mm in height, 262.5 mm in length, and 450 mm in width.

[0054] For the aforementioned powdered coal with a moisture content of 10%, the mass ratio A of molded coal around the furnace lid and the degree of segregation D around the furnace lid were determined when using raw coal (Level 1) blended with molded coal a) from Table 1, and raw coal (Level 2) blended with molded coal a) and b). Level 1 raw coal was blended with 30% molded coal a), and Level 2 raw coal was blended with 16.5% molded coal a) and 13.5% molded coal b). In both cases, the overall blending ratio of molded coal (overall molded coal mass ratio E) was 30%. The results are shown in Table 2. As an example, Figure 2 shows the mass ratio of molded coal in each section of sample box 4, which was determined using segregation test apparatus 1 for Level 1 raw coal.

[0055] [Table 2]

[0056] From the values ​​shown in Tables 1 and 2, it was confirmed that when Level 2 raw coal is used in a coke oven, in which a portion of Level 1 molded coal a) is replaced with molded coal b) of a smaller volume, the degree of segregation decreases, and thus the increase in the mass ratio of molded coal around the furnace lid is suppressed.

[0057] <Example 2: Segregation evaluation in a coal tower> The segregation of molten coal in a coal tower was evaluated using actual equipment including a coal tower and a coal charging car. Evaluations were performed for coking coal of levels 1 and 2, as shown in Table 2. The coal tower has four charging inlets and four discharge ports (charging hoppers) on the coal charging car, each corresponding to one another. Coking coal was charged into the coal tower and then into the charging hopper from its charging inlet. The coking coal was then discharged from the charging hopper's discharge port, and approximately 50 kg samples were taken. The molten coal mass ratio of each sample was calculated. The ratio of the molten coal mass ratios of each sample was then determined. The ratio was calculated so that the sum of the ratios equaled 1. The larger of the ratios of the molten coal mass ratios of the discharge ports on both sides (discharge ports #1 and #4) was taken as the maximum ratio (indicated by the underline in Table 3 below), and the coal tower segregation rate (= maximum ratio / uniform ratio) was calculated. Since there are four discharge ports and the sum of the ratios equals 1, the uniform ratio was set to 0.25. The corrected overall molten coal mass ratio E' was calculated by multiplying the overall molten coal mass ratio E (molten coal blending ratio) of the coking coal by the molten coal yield and the coal tower segregation rate. The results are shown in Table 3 below. The molten coal yield was determined by dividing the +10mm (10mm sieved) mass ratio in the blended coal sampled from the belt conveyor immediately before the coal tower by the overall molten coal mass ratio E, although the method for determining the molten coal yield is not restricted. The yields were 68% for level 1 and 69% for level 2.

[0058] [Table 3]

[0059] Among the discharge ports of the charging hoppers arranged along the length of the coke oven, the ratio of molten coal mass at the #1 and #4 discharge ports at both ends tended to be higher than the uniform ratio of 0.25. Comparing the results for levels 1 and 2, mixing in some of the smaller volume molten coal b) reduced the maximum ratio of molten coal mass at the #1 and #4 discharge ports from 0.31 to 0.29. The corrected overall molten coal mass ratio E' (= overall molten coal mass ratio E × yield × coal tower segregation rate), which is the maximum value of the molten coal mass ratio at the #1 and #4 discharge ports (≒ coke oven charging inlet), was 30.0 × 0.68 × 1.24 = 25.3 at level 1 and 30.0 × 0.69 × 1.16 = 24.0% at level 2.

[0060] <Example 3: Evaluation of molded coal based on the evaluations of Examples 1 and 2, and calculation of the total mass ratio (blending ratio) of molded coal in coke production> Based on the results of Examples 1 and 2, the corrected segregation degree D' considering segregation in the coal tower was determined for coking coal at levels 1 and 2. Specifically, the corrected mass ratio of molded coal around the furnace lid was obtained by multiplying the segregation degree D obtained in Example 1 and the corrected overall molded coal mass ratio E' obtained in Example 2 using formula (2) above. Then, the corrected segregation degree D' was obtained by dividing the obtained corrected mass ratio of molded coal around the furnace lid A' by the overall molded coal mass ratio E (blending ratio: 30%). The calculation results are shown in Table 4 below.

[0061] Furthermore, using this corrected segregation degree D', the total molten coal mass ratio E (blending ratio) for Level 2 coking coal was calculated when producing coke by changing from Level 1 coking coal to Level 2 coking coal. The total molten coal mass ratio E for charging Level 2 coking coal was determined by assuming that the corrected molten coal mass ratio A' around the furnace lid, which takes into account segregation in the coal tower, was the same before and after the coking coal switch. Level 1 coking coal is the standard molten coal, and Level 2 coking coal is the target molten coal. The total molten coal mass ratio E for the standard coking coal is 30%, as described above.

[0062] In the above-described example, the corrected mass ratio A' of molded coal around the furnace lid for the standard coking coal (level 1) was 34.9%, and the corrected degree of segregation D' for the target coking coal (level 2) was 1.05. The blending ratio of the target molded coal (total mass ratio E) that maintains the mass ratio A of molded coal around the furnace lid at 34.9% for the standard coking coal when switching to the target coking coal is given by formula (2) above: E = A' of standard coking coal ÷ D' of target coking coal = 34.9 ÷ 1.05 = 33.24%.

[0063] [Table 4]

[0064] From the above results, it was confirmed that by using a target raw coal that partially contains smaller volume molten coal b) compared to standard molten coal a), the overall molten coal mass ratio E (blending ratio) can be increased (from 30% to 33.24%) while keeping the molten coal mass ratio around the furnace lid (corrected molten coal mass ratio around the furnace lid A') constant. [Explanation of symbols]

[0065] 1. Segregation testing apparatus 2 Hopper 4 Sample Box 6 Gate Plates 8 Platforms

Claims

1. A method for evaluating the segregation of molten coal around the lid of a coke oven, comprising a first evaluation using a segregation testing device and a second evaluation using a coal tower and charging car for charging raw coal into the coke oven, The segregation testing apparatus comprises a hopper for containing raw coal including pulverized coal and molded coal, and a sample box into which the raw coal is charged from the hopper. The sample box is rectangular in shape, corresponding to the area near the furnace lid of the carbonization chamber of a coke oven, with one end corresponding to the furnace lid position and the other end corresponding to the coal charging position of the hopper. It is divided into multiple sections in the length and height directions from one end to the other. The coal tower has multiple charging ports for charging into multiple charging hoppers of the coal charging car, the charging ports and charging hoppers are arranged in the furnace length direction of the coke oven, raw coal is charged into the corresponding charging hoppers from the charging ports, and raw coal is discharged from the respective discharge ports of the charging hoppers. As the first evaluation, the raw coal to be tested is dropped from the hopper of the segregation test apparatus and loaded into the sample box, and the ratio of molded coal contained in the raw coal loaded into the furnace lid area section, which is the section closest to one end of the sample box, is determined. Using the determined furnace lid area molded coal mass ratio and the total molded coal mass ratio, which is the blending ratio of molded coal in the entire raw coal, the degree of segregation, which indicates the degree of segregation of molded coal to the furnace lid area, is determined by the following formula (I). As the second evaluation, the target coking coal is loaded into the coal tower, the coking coal is discharged from each outlet of the coal charging car and collected, the molten coal mass ratio, which is the ratio of molten coal contained in the collected coking coal, is determined for each outlet, the ratio of the molten coal mass ratios for each outlet is determined, the maximum ratio, which is the larger ratio among the ratios of the molten coal mass ratios corresponding to the outlets at both ends, and the uniform ratio, which is the ratio of the molten coal mass ratios for each outlet assuming that molten coal is discharged without variation from each outlet, the coal tower segregation rate, which is the ratio of the maximum ratio to the uniform ratio is determined, and the overall molten coal mass ratio of the coking coal and the coal tower segregation rate are multiplied to determine the corrected overall molten coal mass ratio that takes into account the segregation of molten coal in the coal tower. Using the degree of segregation obtained in the first evaluation and the corrected overall molded coal mass ratio obtained in the second evaluation, the corrected molded coal mass ratio around the furnace lid, taking into account the segregation of molded coal in the coal tower, is calculated using the following formula (I): A method for evaluating segregation of molded coal, characterized by determining the corrected degree of segregation considering segregation of molded coal in the coal tower using the following formula (I), with the corrected mass ratio of molded coal around the furnace lid and the total mass ratio of molded coal of the raw coal. D = A / E (I) In equation (I), D is the degree of segregation, A is the mass ratio of molded coal around the furnace lid, and E is the total mass ratio of molded coal.

2. The corrected degree of segregation of the target molten coal to be charged into the coke oven is determined by the segregation evaluation method for molten coal described in claim 1. For a reference molded coal used as a basis for determining the overall molded coal mass ratio, which is the blending ratio in the raw coal of the target molded coal, the tar addition rate, which is the mass ratio of tar added during the production of the molded coal, is the same as that of the target molded coal, and the corrected degree of segregation of the target molded coal, obtained by the segregation evaluation method of the molded coal, is substituted into formula (I) above to determine the overall molded coal mass ratio. A method for producing coke, characterized by using raw coal in which the target molded coal is blended at the determined total molded coal mass ratio.

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