Coke manufacturing method

Abstract

To provide a method for producing coke that allows for easy determination of the SV of the molten charcoal portion even when combining molten charcoal of any volume with any amount of powdered charcoal, thereby enabling the easy production of high-strength coke. [Solution] A method for producing coke using blended coal containing molded coal and powdered coal, wherein a relationship formula between the cumulative filling loss per unit mass of molded coal and the lower limit of the molded coal portion SV is determined in advance, the actual cumulative filling loss per unit mass of molded coal is determined for a combination of powdered coal intended for use in coke production and arbitrarily selected molded coal for analysis, the actual cumulative filling loss per unit mass of molded coal is determined, the lower limit of the molded coal portion SV is determined by substituting the actual cumulative filling loss per unit mass of molded coal into the relationship formula, molded coal is produced such that the actual SV of the molded coal portion is equal to or greater than the lower limit of the molded coal portion SV, and the blended coal consisting of the powdered coal intended for use and the produced molded coal is used for coke production.

Description

[Technical Field]

[0001] This invention relates to a method for producing coke. [Background technology]

[0002] Conventionally, in the production of coke used in blast furnace operations, various methods have been considered to maintain good coke strength while increasing the proportion of inferior coal, such as non-coking coal, in the blended coal composed of molded coal and pulverized coal, in order to address the depletion of resources of high-quality, strongly coking coal. In order to obtain the desired coke strength using blended coal containing inferior coal, a coal pretreatment process may be useful. For example, known coal drying processes include the Coal Moisture Coal (CMC) method and the Dry-cleaned and Agglomerated Pre-compaction System (DAPS), while processes for blending molded materials such as molded coal include the Dry-cleaned and Agglomerated Precompaction System (DAPS), molded coal blending methods, and other methods for adjusting the particle size of crushed coal. These are combined as appropriate.

[0003] According to the molded coal blending method, the overall bulk density of the charged coal can be improved by blending high-density molded coal, potentially improving coke strength. Furthermore, by utilizing the high density of the molded coal, it is possible to concentrate lower-grade coal within the molded coal without reducing coke strength. The molded coal blending method can also be combined with other coal pretreatment processes, such as drying processes and crushing particle size adjustment methods.

[0004] In the molten coal blending method, voids are created around the molten coal due to the blending process, and these voids may persist even after carbonization. Since these residual voids around the molten coal cause a decrease in coke strength, it is important to produce molten coal with sufficient expandability to fill these voids during carbonization. To understand the expandability of the molten coal needed to fill these voids and to determine the coal blending ratios for the blended coal, it is crucial to accurately estimate the amount of voids around the molten coal in the blended coal charged into the coke oven.

[0005] Patent Document 1 describes a method for producing coke in which molded coal and blended coal made from crushed coal are charged into a coke oven and carbonized, characterized in that a test device is used to fill a container with molded coal and blended coal made from crushed coal by gravity, a cross-sectional image of the inside of the container is taken by X-ray CT, the maximum width W of the void formed around the molded coal is quantified from the obtained cross-sectional image, and further, the maximum expansion volume of the molded coal during carbonization is measured using the test device to determine the amount of expansion of the molded coal as the change in the equivalent circle diameter Δr (mm) before and after expansion, and if the determined change Δr is less than 40% of the maximum width W (mm), the coal composition constituting the molded coal is changed to determine a coal composition in which the change Δr is 40% or more of the maximum width W, and molded coal produced based on this composition is used.

[0006] Patent Document 2 describes a method for analyzing the amount of voids around molded charcoal when a blend of charcoal containing molded charcoal and powdered charcoal is filled into a container. The method involves filling a test container with molded charcoal and powdered charcoal by gravity using a test apparatus, capturing a cross-sectional image of the inside of the test container using X-ray CT, and determining the amount of voids around the molded charcoal by 3D analysis of the obtained cross-sectional image. In the 3D analysis, high-density areas where the density exceeds a predetermined value and low-density areas where the density is below the predetermined value are defined, the high-density areas are filtered using predetermined shape parameters to define the molded charcoal area, and optionally, areas within the high-density areas other than the molded charcoal area and whose volume exceeds a predetermined value are defined as agglomerated charcoal areas. The agglomerated charcoal areas are excluded from the analysis by being treated as having no pixel data, and an expansion process is performed (n+1) times, expanding the periphery of the molded charcoal area in a similar shape to the molded charcoal area by 1 unit volume each time. The above procedure is followed, where n is a natural number, and (n+1) is the number at which the average density of the region whose volume increased in the (n+1)th expansion treatment is approximately the same as the average density of the region whose volume increased in the nth expansion treatment. The average density of the region whose volume increased in the nth and subsequent expansion treatments is used as a threshold. For each expansion treatment, the region whose density exceeds the threshold is defined as the pulverized coal portion, and the region whose density is below the threshold is defined as the void portion. For each expansion treatment, the difference between the average density of the pulverized coal portion and the average density of the void portion is calculated. The amount of filling reduction is calculated by multiplying the volume of the region whose volume increased in each expansion treatment by the difference. The amount of filling reduction is accumulated over the total number of expansion treatments to calculate the cumulative amount of filling reduction, and the cumulative amount of filling reduction is used as an indicator of the amount of voids around the molded coal. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2014-224242 [Patent Document 2] Japanese Patent Publication No. 2024-059325 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the method described in Patent Document 1, the voids around the formed coal in the blended coal containing formed coal and pulverized coal are evaluated as a width by two-dimensional image analysis. By using this value to calculate the expansibility value of the formed coal required to obtain the target coke strength (specifically, the SV (specific volume) of the formed coal part), the blending of the coal constituting the blended coal can be determined. However, in the technique described in Patent Document 1, when the particle size composition of the pulverized coal used is changed, the correspondence between the SV of the formed coal part and the target coke strength may not match the correspondence between the actually measured value of the SV of the formed coal part and the actually measured value of the coke strength, and there is still room for improvement. On the other hand, in the method described in Patent Document 2, the voids around the formed coal are evaluated by integrating the filling reduction amount, which is a value considering density and volume, by 3D image analysis. In the method described in Patent Document 2, a relational expression between the integrated filling reduction amount and the SV of the formed coal part is obtained in advance, the integrated filling reduction amount is substituted into the relational expression to obtain the lower limit value of the SV of the formed coal part, and formed coal with an actually measured SV value of not less than the lower limit value of the SV of the formed coal part is manufactured, and the blended coal composed of the pulverized coal scheduled to be used and the manufactured formed coal is used for coke production. According to this method, if the volume of the formed coal is constant, the integrated filling reduction amount can be calculated regardless of the particle size composition of the pulverized coal, but when the volume of the formed coal changes, the integrated filling reduction amount changes. Therefore, when the volume of the formed coal is changed, the SV of the formed coal part cannot be calculated from the integrated filling reduction amount and needs to be determined by a carbonization test.

[0009] One aspect of the present invention is to solve the above problems and provide a method for producing coke that can easily realize the production of high-strength coke by easily grasping the SV of the formed coal part even when an arbitrary volume of formed coal and an arbitrary pulverized coal are combined.

Means for Solving the Problems

[0010] The gist of the present invention is as follows. [1] A method for producing coke using a blended coal containing formed coal and pulverized coal, The production method includes For the selected blended coal for testing, the integrated filling reduction amount obtained according to the following analysis method (A) is divided by the mass of the formed coal to obtain the integrated filling reduction amount per unit mass of the formed coal. The relational expression between the integrated filling reduction amount per unit mass of the formed coal and the lower limit value of the formed coal part SV range, where the coke strength is constant even when the formed coal part SV is changed, is obtained in advance. For the combination of pulverized coal planned to be used in coke production and arbitrarily selected formed coal for analysis, the measured value of the integrated filling reduction amount per unit mass of the formed coal, which is the value obtained by dividing the integrated filling reduction amount obtained according to the following analysis method (A) by the mass of the formed coal, is obtained. Substitute the measured value of the integrated filling reduction amount per unit mass of the formed coal into the relational expression to obtain the lower limit value of the formed coal part SV. Manufacture formed coal in which the measured value of the formed coal part SV is greater than or equal to the lower limit value of the formed coal part SV. Use the blended coal composed of the planned pulverized coal and the manufactured formed coal for coke production. This is the method. The analysis method (A) is as follows: Using a test device, fill the formed coal and pulverized coal into the test container by natural fall. Take a cross-sectional image of the inside of the test container by X-ray CT. Obtain the void volume around the formed coal by 3D analysis of the obtained cross-sectional image. In the 3D analysis: Define a high-density part with a density exceeding a predetermined value and a low-density part with a density less than or equal to the predetermined value respectively. Filter the high-density part with a predetermined shape parameter to define the formed coal part. Optionally, among the high-density parts, define a region that is outside the formed coal part and has a volume exceeding a predetermined value as a lump coal part. The lump coal part is excluded from the analysis target by treating it as non-existent pixel data. Perform an expansion process of expanding one unit volume at a time in a similar shape to the formed coal part from the periphery of the formed coal part (n + 1) times or more, where n is a natural number. The (n + 1) is a number such that the average density of the region with increased volume in the (n + 1)th expansion process is substantially the same as the average density of the region with increased volume in the nth expansion process. The average density of the region whose volume increased in the nth and subsequent expansion processes is used as the threshold. In each expansion treatment, the region whose volume increases is defined as follows: the region where the density exceeds the threshold is defined as the pulverized coal portion, and the region where the density is below the threshold is defined as the void portion. For each expansion treatment, the difference between the average density of the pulverized coal portion and the average density of the void portion is calculated for the region whose volume has increased. The amount of filling reduction is calculated by multiplying the volume of the region that has increased in volume during each expansion process by the difference value. The cumulative amount of filling loss is calculated by accumulating the aforementioned filling loss over the total number of expansion treatments. The method is A method for producing coke. [2] A method for producing coke using a blend of coal containing molded coal and powdered coal, The aforementioned manufacturing method is For the coal blend selected for the test, a relationship was previously determined between the cumulative packing loss per unit volume of molded coal, which is the value obtained by dividing the cumulative packing loss obtained according to the following analysis method (A) by the volume of molded coal, and the lower limit of the molded coal SV range, which is the lower limit of the molded coal SV range in which the coke strength remains constant even when the molded coal SV is changed. For combinations of pulverized coal intended for use in coke production and arbitrarily selected molded coal for analysis, the measured cumulative filling loss per unit volume of molded coal is obtained by dividing the cumulative filling loss obtained according to the following analysis method (A) by the volume of molded coal. Substitute the measured cumulative filling loss per unit volume of molded coal into the above relational formula to determine the lower limit of SV for the molded coal section. Molded charcoal is manufactured in which the measured SV value of the molded charcoal portion is equal to or greater than the lower limit of the SV value of the molded charcoal portion. The blended coal, consisting of the pulverized coal intended for use and the molded coal produced, is used for coke production. It is a method, The aforementioned analysis method (A) is: Using a test apparatus, molded coal and powdered coal are filled into a test container by gravity. Cross-sectional images of the inside of the test container were acquired using X-ray CT. The amount of voids around the molded coal was determined by 3D analysis of the obtained cross-sectional images. In the aforementioned 3D analysis, A high-density section where the density exceeds a predetermined value and a low-density section where the density is less than or equal to the predetermined value are defined, The high-density portion is filtered using a predetermined shape parameter to define the molded char portion. Optionally, within the high-density portion, any region other than the molded charcoal portion and whose volume exceeds a predetermined value is defined as the agglomerated charcoal portion, and this agglomerated charcoal portion is excluded from the analysis by being treated as having no pixel data. An expansion process is performed (n+1) or more times, starting from the periphery of the molded charcoal portion and expanding by 1 unit volume each time in a shape similar to the molded charcoal portion, where n is a natural number. The (n+1) mentioned above is the number at which the average density of the region whose volume increased in the (n+1)th expansion process is approximately the same as the average density of the region whose volume increased in the nth expansion process. The average density of the region whose volume increased in the nth and subsequent expansion processes is used as the threshold. In each expansion treatment, the region whose volume increases is defined as follows: the region where the density exceeds the threshold is defined as the pulverized coal portion, and the region where the density is below the threshold is defined as the void portion. For each expansion treatment, the difference between the average density of the pulverized coal portion and the average density of the void portion is calculated for the region whose volume has increased. The amount of filling reduction is calculated by multiplying the volume of the region that has increased in volume during each expansion process by the difference value. The cumulative amount of filling loss is calculated by accumulating the aforementioned filling loss over the total number of expansion treatments. The method is A method for producing coke. [Effects of the Invention]

[0011] According to one aspect of the present invention, a method for producing coke can be provided that allows for easy determination of the molten coal portion SV even when a molten coal of any volume and any powdered coal are combined, thereby enabling the easy production of high-strength coke. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram illustrating the image processing flow. [Figure 2] This is a schematic diagram illustrating the amount of filling loss. [Figure 3] This figure shows the particle size distribution of the charcoal powder used in the example. [Figure 4] This figure shows the relationship between the molded coal portion SV and the coke strength DI150 6 in blended coal of levels 1 to 8. [Figure 5] This figure shows the relationship between the molded coal portion SV and the coke strength DI150 6 in blended coal of levels 9 to 15. [Figure 6] This figure shows the relationship between the molded coal portion SV and the coke strength DI150 6 in blended coal at levels 16-23. [Figure 7] This figure shows the relationship between the molded coal portion SV and the coke strength DI150 6 in blended coal at levels 24-28. [Figure 8] This figure shows the relationship between the cumulative filling loss per unit mass of molded coal and the lower limit of the molded coal SV. [Figure 9] This figure shows the relationship between the cumulative filling loss per unit volume of molded coal and the lower limit of the molded coal SV. [Figure 10] This figure shows the relationship between the molded coal portion SV and the coke strength DI150 6 in blended coal at levels 29-34. [Modes for carrying out the invention]

[0013] The following describes exemplary embodiments of the present invention (which may also be referred to as these embodiments in this disclosure), but the present invention is not limited to these embodiments.

[0014] One aspect of the present invention provides a method for producing coke using a blend of coal containing molded coal and powdered coal. In this production method, For the coal blend selected for testing, a relationship is predetermined between the cumulative packing loss per unit mass of molded coal, which is the value obtained by dividing the cumulative packing loss obtained according to the following analysis method (A) by the mass of molded coal, and the lower limit of the molded coal SV range, which is the lower limit of the molded coal SV range in which the coke strength remains constant even when the molded coal SV is changed. For combinations of pulverized coal intended for use in coke production and arbitrarily selected molded coal for analysis, the cumulative filling loss per unit mass of molded coal is calculated by dividing the cumulative filling loss obtained according to the following analysis method (A) by the mass of molded coal. Substitute the measured cumulative packing loss per unit mass of molded coal into the above relational formula to determine the lower limit of SV for the molded coal section. Molded charcoal is manufactured in which the measured SV value of the molded charcoal portion is equal to or greater than the lower limit of the SV value of the molded charcoal portion. The blended coal, consisting of the pulverized coal intended for use and the molded coal produced, is used for coke production. (Analysis method (A)) Using a test apparatus, molded coal and powdered coal are filled into a test container by gravity. Cross-sectional images of the inside of the test container were acquired using X-ray CT. The amount of voids around the molded coal was determined by 3D analysis of the obtained cross-sectional images. In the aforementioned 3D analysis, A high-density section where the density exceeds a predetermined value and a low-density section where the density is less than or equal to the predetermined value are defined, The high-density portion is filtered using a predetermined shape parameter to define the molded char portion. Optionally, within the high-density portion, any region other than the molded charcoal portion and whose volume exceeds a predetermined value is defined as the agglomerated charcoal portion, and this agglomerated charcoal portion is excluded from the analysis by being treated as having no pixel data. An expansion process is performed (n+1) or more times, starting from the periphery of the molded charcoal portion and expanding by 1 unit volume each time in a shape similar to the molded charcoal portion, where n is a natural number. The (n+1) mentioned above is the number at which the average density of the region whose volume increased in the (n+1)th expansion process is approximately the same as the average density of the region whose volume increased in the nth expansion process. The average density of the region whose volume increased in the nth and subsequent expansion processes is used as the threshold. In each expansion treatment, the region whose volume increases is defined as follows: the region where the density exceeds the threshold is defined as the pulverized coal portion, and the region where the density is below the threshold is defined as the void portion. For each expansion treatment, the difference between the average density of the pulverized coal portion and the average density of the void portion is calculated for the region whose volume has increased. The amount of filling reduction is calculated by multiplying the volume of the region that has increased in volume during each expansion process by the difference value. The cumulative amount of filling loss is calculated by accumulating the aforementioned filling loss over the total number of expansion treatments.

[0015] One aspect of the present invention also provides a method for producing coke as described above, wherein the cumulative filling loss per unit volume of molded coal is evaluated instead of the cumulative filling loss per unit mass of molded coal.

[0016] In this disclosure, "pulverized coal" refers to crushed coal, and includes coal that has been further size-adjusted after crushing, and agglomerated coal if it is present. In this disclosure, "agglomerated coal" refers to coal with an equivalent spherical radius of less than 6 mm obtained by adding a binding filler to pulverized coal (pulverized coal below a 0.3 mm sieve in one embodiment) and pressurizing it. In this disclosure, "molded coal" refers to coal with an equivalent spherical radius of 6 mm or more obtained by adding a binding filler to pulverized coal (pulverized coal below a 0.3 mm sieve in one embodiment) and pressurizing it.

[0017] The inventors have previously found that by analyzing the amount of voids around molded coal with high precision using an index called packing loss, it is possible to produce high-strength coke while using a large amount of inferior coal. The coke strength of a blend containing molded coal and pulverized coal is almost constant when the SV of the molded coal portion is above a predetermined value, but when it falls below that predetermined value, it tends to decrease as the SV of the molded coal portion decreases. This tendency is observed similarly regardless of the expansion properties, moisture content, and particle size composition of the pulverized coal, and the above predetermined value differs depending on the cumulative packing loss. Molded coal with a low SV may be inexpensive because it is of inferior quality. Therefore, determining the above predetermined value of the SV of the molded coal portion, that is, the lower limit of the molded coal portion SV which is the limit value at which a decrease in coke strength does not occur when the SV of the molded coal portion is reduced, and selecting and using molded coal that exhibits this lower limit of the molded coal portion SV is advantageous in that high-strength coke can be obtained inexpensively.

[0018] By using the cumulative packing loss obtained by the analysis method (A) of this disclosure, it is possible to estimate the stacking packing loss of various types of coal powder with different properties without actual image analysis, based on a predetermined relationship between the properties of the coal powder, such as particle size composition and moisture content, and the stacking packing loss. Factors that can influence the cumulative packing loss include the particle size composition of the coal powder, the moisture content of the coal powder, and other factors. However, based on the inventors' prior investigations, it is considered that the particle size composition and moisture content of the coal powder have a particularly large influence on the amount of voids around the molded coal. Among the particle size composition, the mass ratio of coarse particles contained in the coal powder is thought to have a particularly strong influence on the amount of voids around the molded coal. This is because if the difference in particle size between the molded coal and the coal powder is small, the interparticle gaps are less likely to be filled with particles. In other words, it is considered that the volume of the molded coal, in addition to the particle size composition of the coal powder, also influences the cumulative packing loss. Furthermore, it is considered that the moisture content of the coal powder affects the amount of voids around the molded coal by affecting the fluidity of the coal powder.

[0019] As described above, cumulative packing loss is a useful indicator for estimating the SV of the molded coal portion. However, since the volume of the molded coal is also thought to affect this cumulative packing loss, when the volume of the molded coal is changed, it is necessary to re-examine the relationship between the cumulative packing loss and the particle size composition and moisture content of the pulverized coal, which requires re-analysis of the image. Therefore, the inventors have investigated various methods to eliminate the need for repeated image analysis when the volume of molded coal is changed, and have conceived of using cumulative packing loss per unit mass of molded coal or per unit volume of molded coal. By using cumulative packing loss per unit mass of molded coal or per unit volume of molded coal, the SV of the molded coal portion can be estimated simply and with high accuracy when any volume of molded coal and any pulverized coal are combined, thus enabling the simple production of high-strength coke.

[0020] <<Estimation of SV of molded coal based on cumulative filling loss per unit mass of molded coal>> The following provides a more detailed example of the case where the cumulative fill-down per unit mass of molded coal is used.

[0021] <Selection of charcoal powder samples> The pulverized coal samples are selected so as to include levels with different particle size configurations and levels with different moisture content. The pulverized coal samples may also include levels with the same particle size configuration or moisture content. In one embodiment, the pulverized coal samples consist of groups of levels where each of the particle size configuration and moisture content has two or more, preferably three or more, different values. From the viewpoint of estimation accuracy, a larger number of different values ​​is advantageous, but from the viewpoint of work efficiency, the number of different values ​​may be 10 or less, or 8 or less, in one embodiment.

[0022] The particle size composition value used for estimation is, in one embodiment, the value of the mass percentage of coarse particles, and preferably, one value selected from the group consisting of sieve mass percentage and particle size. The size of the molded coal is usually assumed to be 3cc to 130cc. The sieve size for the sieve mass percentage, which is an indicator of the mass percentage of coarse particles in the pulverized coal, more specifically, the mesh opening size according to JIS Z 8801-1, is typically 2mm or larger, preferably 2.8mm or larger, or 5.6mm or larger. From the viewpoint of more accurately estimating the influence of coarse particles in the pulverized coal on the amount of voids around the molded coal, the sieve size may, in one embodiment, be 8mm or smaller, or 6.7mm or smaller. As the particle size of the pulverized coal sample, the mass-average diameter, which is an indicator in which the presence of coarse particles contributes significantly to the value, is used.

[0023] <Analysis of voids around molded coal using analysis method (A)> The analysis of the amount of voids around the molded coal may be performed using "Analysis Method (A)" of this disclosure. An example of this analysis method will be described below.

[0024] In analysis method (A), a cross-sectional image of the blended coal obtained using X-ray CT (Computed Tomography) is analyzed in 3D. When attempting to evaluate the voids around molded coal by 3D analysis of cross-sectional images, the evaluation results vary depending on which areas are considered voids, as these voids are regions with low packing density but do not have a completely zero density. In this embodiment, the voids around molded coal are evaluated by 3D analysis of cross-sectional images, and in doing so, an index called packing loss is adopted, which takes volume into account by multiplying density by volume in the areas considered to be voids. Evaluation using packing loss allows for highly accurate quantitative evaluation of the amount of voids without constraints on the size and shape of the voids around molded coal.

[0025] In this disclosure, the expansion process refers to a process in which one voxel (unit volume) (central voxel) and 26 adjacent voxels (peripheral voxels) are considered, the maximum value of the peripheral voxels is calculated, and if it is greater than the value of the central voxel, the value of the central voxel is replaced with the maximum value. In the cross-sectional image, the molded coal is denser than its surroundings (i.e., has a larger X-ray CT value), so by performing this expansion process on the periphery of the molded coal, the molded coal expands in a similar shape at a rate of 1 voxel per process.

[0026] Figure 1 is a schematic diagram illustrating the image processing flow in one embodiment of the present invention. In the method of this embodiment, the voids around the molded coal are analyzed by performing 3D analysis in steps S12 to S18 on the X-ray CT cross-sectional image acquired in step S11. Below, an example of the procedure for analyzing the amount of voids around molded coal according to this embodiment will be described with reference to Figure 1.

[0027] (Step S11) In this step, molded coal and pulverized coal are filled into a test container by gravity using a test apparatus, and a cross-sectional image of the inside of the test container is captured by X-ray CT. The coal constituting each of the molded coal and pulverized coal may be one type or a combination of two or more types. The pulverized coal may include agglomerated coal in one embodiment, or it may not include agglomerated coal in another embodiment. The test apparatus and X-ray CT apparatus may be commercially available devices, and the measurement conditions of the X-ray CT may be set as desired. The voxel size is preferably small and is not particularly limited from the viewpoint of obtaining good analytical accuracy. In one embodiment of the present invention, the size was set to 0.488 mm × 0.488 mm × 0.488 mm.

[0028] (Step S12) In steps S12 to S18, the software attached to the X-ray CT scanner may be used for 3D analysis. In step S12, the analysis area (hereinafter also referred to as ROI) within the cross-sectional image (hereinafter also referred to as the original image) acquired in step S11 is binarized by density, and high-density areas where the density exceeds a predetermined value and low-density areas where the density is below a predetermined value are defined. The above default value may be set appropriately so that molded coal and agglomerated coal, if present, are classified as high-density areas, and pulverized coal other than agglomerated coal are classified as low-density areas, for example, 1.0 g / cm³. 3 That is acceptable.

[0029] (Step S13) In this step, the high-density portion described above is filtered using predetermined shape parameters to define the molded char portion. The molded char portion may be defined using the following procedure. a) For the high-density section defined in step S12, small particles (in one embodiment, small particles of 100 voxels or less) are removed to reduce noise. b) Separate the particles in the high-density portion after the processing in a) above so that each particle can be distinguished. Separation may be performed by labeling. c) From the high-density portion after the processing in b) above, the region corresponding to molded coal is extracted by filtering using predetermined shape parameters. The predetermined shape parameters are set so as to accurately define the molded coal portion, and in one embodiment, they may be one or more of the following: Anisotropy, Flatness, Elongation, Volume, etc. A combination of Anisotropy, Flatness, and Elongation is preferred because it allows for easy implementation of the desired filtering regardless of the size of the molded coal. For example, filtering may be performed using Anisotropy < 0.9, Flatness < 0.4, and Elongation > 0.4. d) In the region extracted in c) above, constrictions are detected and removed. Generally, molded charcoal often has constrictions in the burr area. Constrictions may be detected using the watershed method. e) The area after processing d) above is subjected to one shrink (i.e., one voxel shrink), small particle removal using the same procedure as a) above, one expansion (i.e., one voxel expansion), and smoothing in that order, and the remaining area is defined as the molded charcoal portion.

[0030] (Step S14) This step may only be performed if the pulverized coal contains agglomerated coal. In this step, the agglomerated coal region is defined as the area of ​​the high-density region defined in step S12 that is not the molded coal region defined in step S13 and whose volume exceeds a predetermined value. The agglomerated coal region is treated as having no pixel data. When pulverized coal contains agglomerated coal, the agglomerated coal has an equivalent sphere radius of less than 6 mm, but its density is as high as that of molded coal. If such agglomerated coal is included in the expansion treatment area in addition to molded coal, there is a risk that the voids will not be accurately evaluated. Therefore, if the blended coal contains agglomerated coal, the agglomerated coal is excluded from the analysis.

[0031] Specifically, the molded char portion defined in step S13 is subtracted from the high-density portion defined in step S12, and the remaining area is labeled. From this labeled area, volume filtering is performed (in one embodiment, Volume > 15 mm). 3 The aggregated charcoal portion is extracted by selecting only the region that satisfies the volume parameter.

[0032] Furthermore, if the blended coal contains agglomerate, voids are formed not only around the molded coal but also around the agglomerate. When agglomerate is present around the molded coal, it is conceivable that the amount of packing loss around the agglomerate should be included in the packing loss around the molded coal. Therefore, it is conceivable to determine the packing loss around the agglomerate and subtract it from the packing loss around the molded coal. However, according to the inventors' studies, the proportion of the packing loss around the agglomerate included in the packing loss around the molded coal is negligible, and the influence of the presence of voids around the agglomerate on coke strength is negligible. Therefore, in the evaluation of packing loss in this embodiment, the packing loss around the agglomerate does not need to be considered. Specifically, in the 3D analysis of this embodiment, the area corresponding to the agglomerate is excluded from the analysis of this embodiment by being treated as an area without pixel data. In this disclosure, the cumulative packing loss refers to the packing loss around the molded coal.

[0033] (Step S15) In this step, within the ROI of the original image, the molded charcoal portion defined in step S13 above is subjected to an expansion process of 1 unit volume (i.e., 1 voxel) at a time, starting from the periphery of the molded charcoal portion and expanding in a similar shape to the molded charcoal portion, at least (n+1) times, where n is a natural number. (n+1) is the number at which the average density of the region whose volume increased in the (n+1)th expansion process is approximately the same as the average density of the region whose volume increased in the nth expansion process. Here, "approximately the same" means, in one embodiment, that the average density of the region whose volume increased in the (n+1)th expansion process is within ±0.3% of the average density of the region whose volume increased in the nth expansion process. Here, ±0.3% corresponds to measurement variability and is not limited to this value.

[0034] After each expansion process is completed, the volume of the region increased by that expansion process (i.e., the volume increase due to that expansion process) and the average density are calculated. The volume corresponds to the number of voxels in the region whose volume increased. The average density is calculated by taking the number average of the CT values ​​of each voxel in the region whose volume increased by the number of voxels in that region. The expansion process is carried out at least until the average density of the region increased by one expansion process becomes approximately the same even if the number of expansion processes is increased. The total number of expansion processes may be (n+1), or it may be more than (n+1), for example, 10 or more, or 20 or more. In one embodiment, the total number of expansion processes may be 30 to 50, for example, 30.

[0035] (Step S16) In this step, the average density of the region whose volume increased in the nth expansion treatment is used as a threshold. For each expansion treatment, the region whose density exceeds the threshold is defined as the pulverized coal portion, and the region whose density is below the threshold is defined as the void portion.

[0036] (Step S17) Next, for the region whose volume increased in each expansion treatment, the difference between the average density of the pulverized coal portion and the average density of the void portion is calculated. The average density of the pulverized coal portion is the number average of the CT values ​​of each voxel contained in the pulverized coal portion, multiplied by the total number of voxels in the pulverized coal portion. The average density of the void portion is the number average of the CT values ​​of each voxel contained in the void portion, multiplied by the total number of voxels in the void portion. Next, the amount of filling reduction is calculated by multiplying the volume of the region whose volume increased in each expansion treatment by the above difference value.

[0037] (Step S18) In this step, the cumulative filling loss is calculated by accumulating the filling loss amount calculated in step S17 over the total number of expansion treatments. Figure 2 is a schematic diagram illustrating the filling loss amount. The filling loss amount calculated as described above in this step changes due to the presence of voids up to a certain number of expansion treatments (n times in one embodiment), but beyond that number (more than (n+1) times in one embodiment), it becomes almost constant because there are no longer any voids in the region increased by the expansion treatment. For example, in Figure 2, the filling loss amount in the region increased by each expansion treatment changes up to the 8th expansion treatment, but from the 9th expansion treatment onward, the filling loss amount becomes almost constant from the value after the 8th expansion treatment. The cumulative value of the filling loss amount over the number of expansion treatments until the filling loss amount becomes almost constant reflects the total amount of voids present around the molded coal. From the above viewpoint, in one embodiment, the cumulative filling loss amount obtained by summing the filling loss amounts over the total number of expansion treatments of (n+1) times or more is useful as an indicator of the amount of voids around the molded coal.

[0038] <Calculation of cumulative filling loss per unit mass of molded coal> For each blended coal sample, the cumulative packing loss obtained according to the analysis method described above is divided by the mass of the molded coal used in the analysis (in one embodiment, the dry mass) to obtain the cumulative packing loss per unit mass of molded coal.

[0039] <Coke production> In coke production, a relationship equation (II) between the cumulative packing loss per unit mass of molded coal and the lower limit of the molded coal portion's SV is determined in advance. For the blended coal containing the pulverized coal to be used, the cumulative packing loss per unit mass of molded coal is calculated, and this is substituted into the above relationship equation (II) to calculate the lower limit of the molded coal portion's SV. Molded coal whose SV is equal to or greater than this lower limit of the molded coal portion's SV can then be blended with the pulverized coal to be used. In order to construct a blended coal that can form high-strength coke while using a large amount of inferior coal, it is preferable that the value is as close as possible to the lower limit of the molded coal portion's SV. Specifically, the variation in the molded coal portion's SV in actual operation is usually ±0.1 cm. 3 Considering that it is approximately / g, the SV lower limit of the molded charcoal portion is +0.1cm. 3It is preferable to blend molded charcoal having an SV value of / g with the charcoal powder intended for use as described above.

[0040] In the coke manufacturing method of this embodiment, A) For the blended coal selected for testing, a relationship equation (II) is predetermined between the cumulative packing loss per unit mass of molded coal, obtained using the analysis method (A) of this disclosure, and the lower limit of the molded coal SV range, which is the lower limit of the molded coal SV range in which the coke strength remains constant even when the molded coal SV is changed. B) For combinations of pulverized coal intended for use in coke production and arbitrarily selected molded coal for analysis, the cumulative packing loss per unit mass of molded coal is determined using the analysis method (A) of this disclosure. Substitute the cumulative packing loss per unit mass of molded coal obtained in C) and B) into the above relational equation (II) to find the lower limit of SV for the molded coal section. D) Manufacture molded coal in which the measured SV value is equal to or greater than the lower limit of the SV value of the molded coal portion, and use the blended coal, which consists of the pulverized coal to be used and the manufactured molded coal, for coke production. The following provides a more detailed explanation.

[0041] (Derivation of the relationship equation (II) between the cumulative fill-down per unit mass of molded coal and the lower limit of SV in the molded coal section) In A) above, for the blended coal selected for testing, a relationship formula (II) is predetermined between the cumulative packing loss per unit mass of molded coal, calculated by the analysis method for the amount of voids around the molded coal in this embodiment, and the lower limit of the molded coal SV, which is the limit value at which a decrease in coke strength does not occur when the SV of the molded coal is reduced. In one embodiment, multiple levels of pulverized coal with different moisture content and / or particle size composition, and multiple levels of molded coal with different SV are selected. For the test blended coal, which is a combination of each level of pulverized coal and one level of molded coal arbitrarily selected, the cumulative packing loss per unit mass of molded coal is calculated using the method of this embodiment. For example, if three levels of pulverized coal and ten levels of molded coal are selected, the cumulative packing loss per unit mass of molded coal is calculated for a total of three types of test blended coal. For the molded coal used to calculate the cumulative packing loss per unit mass of molded coal, one without defects, etc., is selected from the above multiple levels.

[0042] The lower limit value of the molded carbon part SV, which is the limit value at which no decrease in coke strength occurs when the molded carbon part SV is decreased, is obtained as follows. a) For each level of the molded carbon selected for the test, the SV is measured by a carbonization test using a dilatometer in accordance with JIS M8801. b) For each of the cokes obtained from the test blend carbon, the coke strength is measured by a drum test in accordance with JIS K 2151. The coke strength may be, in one aspect, DI 150 15 or DI 150 6. DI 150 15 is the ratio of the amount on the 15 mm sieve after 150 rotations in the drum test and is an index mainly representing the volume fracture strength of the coke. DI 150 6 is the ratio of the amount passing through the 6 mm sieve after 150 rotations in the drum test and is an index mainly representing the surface fracture strength of the coke. c) For all test blends, plot the relationship between the SV of the molded coal portion (x-axis) and the coke strength obtained from the test blend (y-axis) for each level of pulverized coal. For example, if three levels of pulverized coal and ten levels of molded coal are selected, create a first plot for the test blends related to the combination of pulverized coal of the first level and each of the molded coals of the first to tenth levels, a second plot for the test blends related to the combination of pulverized coal of the second level and each of the molded coals of the first to tenth levels, and a third plot for the test blends related to the combination of pulverized coal of the third level and each of the molded coals of the first to tenth levels. For each plot, define the minimum value of the SV of the molded coal portion in the region where the coke strength is maintained at a constant level regardless of the value of the SV of the molded coal portion as the lower limit of the SV of the molded coal portion. The region in which coke strength remains constant regardless of the value of the molten coal portion SV is the region in which the coke strength value falls within the standard deviation for each plot. For example, if the standard deviation for each plot is 0.4, the region in which coke strength remains constant regardless of the value of the molten coal portion SV is the region in which the coke strength falls within the range of ±0.4. In this way, the lower limit of the molten coal portion SV for each level of pulverized coal is obtained. Note that if the degree to which the coke strength (y-axis) obtained from the test blended coal increases in response to an increase in the molten coal portion SV (x-axis) clearly changes and is maintained at approximately the same value, it can be considered a region in which it is maintained constant, and this judgment is not limited to the standard deviation. d) The cumulative filling loss per unit mass of molded coal for each level of pulverized coal, calculated above, is plotted on the x-axis, and the lower limit of SV of the molded coal portion for each level of pulverized coal, as defined above, is plotted on the y-axis. Then, for example, by linear approximation, equation (II) relating the cumulative filling loss per unit mass of molded coal and the lower limit of SV of the molded coal portion is derived.

[0043] (Selection of coal candidates for use in coke production) In B) above, the cumulative packing loss per unit mass of molded coal is determined using the void volume analysis method around the molded coal of this embodiment for combinations of pulverized coal intended for use in coke production and arbitrarily selected molded coal for analysis. Molded coal without defects may be selected.

[0044] In C) above, the cumulative packing reduction per unit mass of molded coal obtained in B) above is substituted into relation (II) obtained in A) above to determine the lower limit of SV for the molded coal portion. This lower limit of SV for the molded coal portion indicates the limit to which the SV for the molded coal portion can be reduced (i.e., to utilize lower quality molded coal) without causing a decrease in coke strength due to the molded coal (more specifically, due to voids remaining in the coke caused by insufficient expansion of the molded coal portion during coking) in the blended coal containing the pulverized coal to be used.

[0045] In step D) above, molded coal is produced in which the measured SV value is equal to or greater than the lower limit of the molded coal portion SV value determined above. It is preferable that the measured SV value of the manufactured molded coal is as close as possible to the lower limit of the molded coal portion SV value, but the variation in the molded coal portion SV during actual operation is usually ±0.1 cm. 3 Considering that it is approximately / g, for example, the lower limit of SV for molded charcoal + 0.1cm 3 A value of / g is preferred. Such molded coal may be of the lowest quality to the extent that it does not cause a decrease in coke strength due to the molded coal. The measured SV value of the molded coal can be adjusted to the desired value by, for example, adjusting the type and / or amount of coal and / or binding filler used in the production of the molded coal. By using the molded coal produced as described above in the production of coke, it becomes possible to produce coke that is inexpensive while maintaining the desired coke strength.

[0046] <<Estimation of SV of molded coal based on cumulative filling loss per unit volume of molded coal>> The above describes the case where the cumulative packing loss per unit mass of molded coal is used as an indicator of the amount of voids around the molded coal. However, instead of the cumulative packing loss per unit mass of molded coal, the cumulative packing loss per unit volume of molded coal may also be evaluated. The cumulative packing loss per unit volume of molded coal is the value obtained by dividing the cumulative packing loss by the volume of molded coal. The volume of molded coal may be the actual volume, which is the measured value obtained by the small-quantity apparent density measurement method in accordance with JIS K2151:2004. The procedure described above in "Estimation of Molded Coal SV Based on Cumulative Packing Loss per Unit Mass of Molded Coal" is replaced with "Cumulative Packing Loss per Unit Volume of Molded Coal," but the same procedure as described above may be adopted. This method also allows for the simple and accurate determination of the SV (saturation coefficient) of the molten coal portion when using any volume of molten coal and any amount of powdered coal, thus enabling the easy production of high-strength coke. [Examples]

[0047] The following describes exemplary embodiments of the present invention with reference to examples, but the present invention is not limited to these embodiments.

[0048] <Analysis of void volume around molded coal> (Coal used) For the analysis, we used pulverized coal of levels 1-3 shown in Table 1 and molded coal of levels 1-3 without defects, as shown in Table 2. "Pulverized coal" refers to the coal itself obtained by pulverization, while "whole-grain coal" refers to coal with a particle size of 0.3 mm to 3 mm. Figure 3 shows the particle size distribution of each type of pulverized coal. Note that the moisture content in Table 1 was measured using a moisture determination method compliant with JIS M 8812:2006.

[0049] The voids around the molded coal were analyzed by the amount of filling reduction using the following procedure.

[0050] (Step S11) Using a test apparatus, molded coal and powdered coal were filled into a test container by gravity, and cross-sectional images of the inside of the test container were acquired by X-ray CT. As the test apparatus, a Mini ASTM apparatus (drop height 1m) was used, which is a 1 / 2 scale version of the ASTM improved bulk density measuring apparatus (Qingtang et al., Coke Circular, 30(11), 13-5(1981)), which is an improved version of the bulk density test in accordance with ASTM D 291-86. The Mini ASTM test container (150 × 150 × 150 mm) was filled with coal by dropping 1.5 kg of pulverized coal of each level, followed by molded coal of each level, and finally the remaining 2.75 kg of pulverized coal of each level. The sample container filled with coal was imaged using an X-ray CT diagnostic device (TSX-201 (Aquilion LB) manufactured by Toshiba Medical Systems Corporation). The X-ray CT imaging conditions were as follows. Under the following imaging conditions, a resolution of 0.488 mm per pixel was obtained. Scan Mode: Helical Tube voltage: 120kV Tube current: 400mA FOV (Field of View): 440mm Image slice thickness: 0.5mm The obtained cross-sectional images were processed using the image analysis software Avizo. All analyses were performed in 3D. The region of interest (ROI) was defined as the central 120mm rectangular area (i.e., the central part (120×120×120mm) within the container dimensions (150×150×150mm)) to exclude wall effects.

[0051] (Step S12) Based on the X-ray CT value of each pixel within the ROI, the density (BD) is expressed by the following relationship: BD(t / m 3 ) = 0.001 × (X-ray CT value) + 1 The calculation was performed according to the following formula. Density is 1.0 g / cm³. 3 Areas exceeding 1.0 g / cm³ are high-density areas. 3 The following regions were defined as low-density areas.

[0052] (Step S13) a) Small particles of 100 voxels or less were removed from the high-density region defined in step S12. b) The high-density portion after the processing in a) above was subjected to a labeling process so that the particles could be separated and distinguished one by one. c) From the high-density region after the processing described in b) above, only those particles satisfying the shape parameters of Anisotropy < 0.9, Flatness < 0.4, and Elongation > 0.4 were selected as heteromorphic particles. d) The irregularly shaped particles extracted in c) above were subjected to the watershed method to detect and remove constrictions. e) The irregularly shaped particles after the process in d) above were processed in the following order: 1 voxel shrinkage, removal of small particles using the same procedure as in a), 1 voxel expansion, and smoothing. The remaining area was defined as the molded carbon portion. All expansion and shrinkage processes were performed in a spherical shape (ball dilation / ball erosion).

[0053] (Step S14) This step was not performed because agglomerated charcoal was not used.

[0054] (Step S15) Within the ROI of the original image, the molded char portion defined in step S13 above was subjected to an expansion process 30 times, in which one voxel was expanded each time from the periphery of the molded char portion in a shape similar to the molded char portion.

[0055] (Step S16) After each expansion treatment was completed, the volume of the area increased by that treatment (i.e., the volume increase due to one expansion treatment) and the average density were calculated. After more than 21 expansion treatments, the average density remained almost unchanged, so the average density after 21 expansion treatments was defined as the average density of the pulverized coal portion. This average density was used as a threshold, and the area exceeding this threshold was defined as the pulverized coal portion, while the area below this threshold was defined as the void portion.

[0056] (Step S17) The average density of the coal pulverized portion was calculated by taking the number average of the densities of each voxel corresponding to the coal pulverized portion, and the average density of the void portion was calculated by taking the number average of the densities of each voxel corresponding to the void portion, and the difference between the average density of the coal pulverized portion and the average density of the void portion was calculated. For each expansion treatment cycle, the amount of filling reduction was calculated according to the following formula. Filling reduction amount = [Volume of the region that increased in volume during each expansion treatment] × [Difference between the average density of the pulverized coal portion and the average density of the void portion]

[0057] (Step S18) The cumulative amount of filling loss was calculated by accumulating the above-mentioned filling loss over the number of expansion treatments. The results are shown in Table 3.

[0058] <Cumulative loss of filling per unit mass of molded coal, cumulative loss of filling per unit volume of molded coal> For each level, the cumulative fill-down amount obtained above was divided by the dry mass of the molded coal to calculate the cumulative fill-down amount per unit mass of molded coal. Then, the cumulative fill-down amount obtained above was divided by the actual volume of the molded coal to calculate the cumulative fill-down amount per unit volume of molded coal. The results are shown in Table 3.

[0059] <Evaluation of the lower limit of SV of molded coal by carbonization test using a test coke oven> Next, for blended coal prepared by mixing powdered coal with molded coal at a moisture content of 4% or 10% by mass, the lower limit of the SV value of the molded coal portion was evaluated by carbonization tests using a test coke oven.

[0060] Table 4 shows the properties of each coal, and Table 5 shows the blending conditions for the pulverized coal portion in the blended coal using the coals in Table 4. Blending condition 1 was whole-grain coal with a particle size of 0.3 to 3 mm (moisture content 4% by mass), blending condition 2 was crushed coal with an 85% sieve-down ratio of 3 mm (moisture content 4% by mass), blending condition 3 was crushed coal with an 85% sieve-down ratio of 3 mm (moisture content 10% by mass), and blending condition 4 was crushed coal with an 85% sieve-down ratio of 3 mm (moisture content 10% by mass). The 3 mm sieve-down ratio as the crushed particle size was 92.5%, 85%, 85%, and 85% for blending conditions 1, 2, 3, and 4, respectively. A tar-based binder was used as the liquid binder, and asphalt pitch (ASP) was used as the solid binder. For convenience, in this example, sieves with mesh openings of 2.8 mm and 5.6 mm according to JIS Z 8801-1 are referred to as 3 mm sieves and 6 mm sieves, respectively.

[0061] Table 6 shows the mixing conditions for the molded charcoal. Molded charcoal was produced by molding powdered coal with a 3mm particle size and a 90% mass ratio below the sieve using a molding machine (manufactured by Shinto Kogyo Co., Ltd.) under mixing conditions 1 to 30. The molded charcoal was produced in three types: pillow type with an actual volume of 4cc (for mixing conditions 24, 26-29 in Table 6), pillow type with an actual volume of 18cc (for mixing conditions 24-25, 27-30 in Table 6), and pillow type with an actual volume of 38cc (for mixing conditions 1-23 in Table 6). A tar-based binder was used as the liquid binder, and asphalt pitch (ASP) was used as the solid binder.

[0062] (Measurement of SV of molded charcoal by carbonization test using a dilartometer) A carbonization test was conducted using a dilartometer. Molded charcoal under each of the blending conditions shown in Table 6 was crushed and the particle size was adjusted to 100% of the mass below a 3 mm sieve. Then, using a molding machine for the dilartometer, the bulk density was determined to be 1.10 g / cm³. 3 (Dry basis), a molded product with a height of 60 mm was placed in a reaction tube and heated at a heating rate of 3°C / min to perform a carbonization test, and the SV of the molded carbon was measured. The results are shown in Table 6.

[0063] (Measurement of coke strength by drum test) Blended coal, consisting of pulverized coal and molded coal, was prepared under the conditions of levels 1 to 28 shown in Table 7. The resulting coke was then subjected to drum tests at rotation speeds of 30 and 150 revolutions per minute, with N=3. The results are shown in Table 7.

[0064] The lower limit of the molded coal SV, which is the limit at which the coke strength remains constant, was determined from the values ​​of the molded coal SV measured in the carbonization test using a dilartometer and the coke strength measured in the drum test.

[0065] Figure 4 shows the SV of the molded coal portion and the coke strength DI of blended coal at levels 1 to 8. 150 This figure shows the relationship with 6. From the results shown in Figure 4, the molded charcoal portion SV is 1.0 cm 3 In the range higher than / g, the coke strength DI of the entire coal blend is 1. 150 6 is almost identical, but the molded charcoal part SV is 0.93 cm 3 / g, plus 0.9cm 3 When the / g decreases, the coke strength DI 150 It can be seen that 6 has decreased significantly. The molded charcoal portion SV is 0.9 cm 3 / g and 0.93cm 3 The linear approximation line for the plots where / g is (and therefore the line connecting them) and the DI of the other plots 150 The intersection point with the line representing the average value of 6 was determined as the lower limit of the molded charcoal SV, which was 0.97 cm. 3 It was / g.

[0066] Similarly, Figures 5-7 show, in order, the molded coal portion SV and coke strength DI for blended coal at levels 9-15, 16-23, and 24-28. 150 This figure shows the relationship with 6. The SV and DI of the molded charcoal portion for levels 9 to 15 (i.e., 38cc of molded charcoal mixed with crushed charcoal with a moisture content of 4% by mass, which is blending condition 2). 150 The lower limit of SV in the molded charcoal portion, as determined from Figure 5 which shows the relationship with 6, is 1.10 cm. 3 The values ​​are / g, and the SV and DI of the molded charcoal portion for levels 16-23 (i.e., 38cc of molded charcoal mixed with crushed charcoal with a moisture content of 10% by mass, which is blending condition 3). 150The lower limit of SV in the molded charcoal portion, which can be determined from Figure 6 showing the relationship with 6, is 1.50 cm. 3 The values ​​are / g, and the SV and DI of the molded charcoal portion for levels 24-28 (i.e., 4cc of molded charcoal mixed with crushed charcoal with a moisture content of 10% by mass, which is blending condition 4). 150 The lower limit of SV in the molded charcoal portion, as determined from Figure 7 which shows the relationship with 6, is 1.58 cm. 3 It was / g.

[0067] Figure 8 shows the cumulative packing loss per unit mass of molded coal shown in Table 3, and the coke strength DI obtained from Figures 4-7. 150 This figure shows the relationship with the lower limit of SV in the molded coal section, which is the limit at which 6 is maintained at a constant value. By linearly approximating the plot shown in Figure 8, the following relationship (II-1) was obtained. This approximation formula is R 2 It showed a strong correlation of 0.9691. [Lower limit of SV for molded coal] = 0.4157 × [Cumulative filling loss per unit mass of molded coal × 10 -2 ]+0.78 (II-1)

[0068] Figure 9 shows the cumulative packing loss per unit volume of molded coal shown in Table 3, and the coke strength DI obtained from Figures 4-7. 150 This figure shows the relationship with the lower limit of SV in the molded coal section, which is the limit at which 6 is maintained at a constant value. By linearly approximating the plot shown in Figure 9, the following relationship (II-2) was obtained. This approximation formula is R 2 It showed a strong correlation of =0.9947. [Lower limit of SV for molded coal] = 0.3655 × [Cumulative filling loss per unit volume of molded coal × 10 -2 ]+0.7749 (II-2)

[0069] <Validity evaluation of the lower limit of SV value for molded coal, calculated from the cumulative fill loss per unit mass of molded coal, or the cumulative fill loss per unit volume of molded coal> [Example 1] For the cumulative packing loss per unit mass of molded coal shown in Table 3, using the above relational equation (II-1) as relational equation (II) in this disclosure, the coke strength DI for analysis condition 5 (when 18 cc of molded coal is mixed with crushed coal with a moisture content of 10% by mass)150 The lower limit of SV in the molded charcoal section, which is the limit at which 6 is maintained at a constant level, was found to be 1.52 cm. 3 The result was calculated as / g.

[0070] [Example 2] For the cumulative packing loss per unit volume of molded coal shown in Table 3, using the above relational equation (II-2) as relational equation (II) of this disclosure, the coke strength DI for analysis condition 5 (when 18 cc of molded coal is mixed with crushed coal with a moisture content of 10% by mass) 150 The lower limit of SV in the molded charcoal section, which is the limit at which 6 is maintained at a constant level, was found to be 1.54 cm. 3 The result was calculated as / g.

[0071] [Reference example 1] As shown in Table 7 for levels 29-34, carbonization tests were conducted to determine the lower limit of the molded coal portion's SV (Small Value), which is the limit at which the coke strength remains constant when 18cc of molded coal is mixed with crushed coal with a moisture content of 10% by mass. Figure 10 shows the molded coal portion's SV and DI for levels 29-34. 150 This figure shows the relationship with 6. The lower limit of SV in the molded charcoal portion, which can be determined from Figure 10, is 1.51 cm. 3 It was / g.

[0072] The results above show that the lower limit of SV in the molded charcoal portion is in close agreement with the value obtained from the carbonization test (Reference Example 1) and the value calculated from relational equation (II-1) (Example 1) or relational equation (II-2) (Example 2). The results are shown in Table 8.

[0073] As described above, by understanding the relationship between the cumulative filling loss per unit mass of molded coal and the lower limit of the molded coal SV, it is possible to calculate the lower limit of the molded coal SV when using any volume of molded coal and any powdered coal from the cumulative filling loss per unit mass of molded coal. Furthermore, by understanding the relationship between the cumulative filling loss per unit volume of molded coal and the lower limit of the molded coal SV, it is possible to calculate the lower limit of the molded coal SV when using any volume of molded coal and any powdered coal from the cumulative filling loss per unit volume of molded coal. In other words, according to this embodiment, the blend of coal used in coke production can be easily determined.

[0074] [Table 1]

[0075] [Table 2]

[0076] [Table 3]

[0077] [Table 4]

[0078] [Table 5]

[0079] [Table 6]

[0080] [Table 7]

[0081] [Table 8]

Claims

1. A method for producing coke using a blend of coal containing molded coal and powdered coal, The aforementioned manufacturing method is For the coal blend selected for testing, a relationship is predetermined between the cumulative packing loss per unit mass of molded coal, which is the value obtained by dividing the cumulative packing loss obtained according to the following analysis method (A) by the mass of molded coal, and the lower limit of the molded coal SV range, which is the lower limit of the molded coal SV range in which the coke strength remains constant even when the molded coal SV is changed. For combinations of pulverized coal intended for use in coke production and arbitrarily selected molded coal for analysis, the cumulative filling loss per unit mass of molded coal is calculated by dividing the cumulative filling loss obtained according to the following analysis method (A) by the mass of molded coal. Substitute the measured cumulative filling loss per unit mass of molded coal into the above relational formula to determine the lower limit of SV for the molded coal section. Molded charcoal is manufactured in which the measured SV value of the molded charcoal portion is equal to or greater than the lower limit value of the molded charcoal portion. The blended coal, consisting of the pulverized coal intended for use and the molded coal produced, is used for coke production. It is a method, The aforementioned analysis method (A) is: Using a test apparatus, molded coal and powdered coal are filled into a test container by gravity. Cross-sectional images of the inside of the test container were acquired using X-ray CT. The amount of voids around the molded coal was determined by 3D analysis of the obtained cross-sectional images. In the aforementioned 3D analysis, A high-density section where the density exceeds a predetermined value and a low-density section where the density is less than or equal to the predetermined value are defined, The high-density portion is filtered using a predetermined shape parameter to define the molded char portion. Optionally, within the high-density portion, any region other than the molded charcoal portion and whose volume exceeds a predetermined value is defined as the agglomerated charcoal portion, and this agglomerated charcoal portion is excluded from the analysis by being treated as having no pixel data. An expansion process is performed (n+1) or more times, starting from the periphery of the molded charcoal portion and expanding by one unit volume each time in a shape similar to the molded charcoal portion, where n is a natural number. The (n+1) is the number at which the average density of the region whose volume increased in the (n+1)th expansion process is approximately the same as the average density of the region whose volume increased in the nth expansion process. The average density of the region whose volume increased in the nth and subsequent expansion processes is used as the threshold. In each expansion treatment, the region whose volume increases is defined as follows: the region where the density exceeds the threshold is defined as the pulverized coal portion, and the region where the density is below the threshold is defined as the void portion. For each expansion treatment, the difference between the average density of the pulverized coal portion and the average density of the void portion is calculated for the region whose volume has increased. The amount of filling reduction is calculated by multiplying the volume of the region that has increased in volume during each expansion process by the difference value. The cumulative amount of filling loss is calculated by accumulating the aforementioned filling loss over the total number of expansion treatments. The method is A method for producing coke.

2. A method for producing coke using a blend of coal containing molded coal and powdered coal, The aforementioned manufacturing method is For the coal blend selected for testing, a relationship is predetermined between the cumulative filling loss per unit volume of molded coal, which is the value obtained by dividing the cumulative filling loss obtained according to the following analysis method (A) by the volume of molded coal, and the lower limit of the molded coal SV range, which is the lower limit of the molded coal SV range in which the coke strength remains constant even when the molded coal SV is changed. For combinations of pulverized coal intended for use in coke production and arbitrarily selected molded coal for analysis, the cumulative filling loss per unit volume of molded coal is calculated by dividing the cumulative filling loss obtained according to the following analysis method (A) by the volume of molded coal. Substitute the measured cumulative filling loss per unit volume of molded coal into the above relational formula to determine the lower limit of SV for the molded coal section. Molded charcoal is manufactured in which the measured SV value of the molded charcoal portion is equal to or greater than the lower limit value of the molded charcoal portion. The blended coal, consisting of the pulverized coal intended for use and the molded coal produced, is used for coke production. It is a method, The aforementioned analysis method (A) is: Using a test apparatus, molded coal and powdered coal are filled into a test container by gravity. Cross-sectional images of the inside of the test container were acquired using X-ray CT. The amount of voids around the molded coal was determined by 3D analysis of the obtained cross-sectional images. In the aforementioned 3D analysis, A high-density section where the density exceeds a predetermined value and a low-density section where the density is less than or equal to the predetermined value are defined, The high-density portion is filtered using a predetermined shape parameter to define the molded char portion. Optionally, within the high-density portion, any region other than the molded charcoal portion and whose volume exceeds a predetermined value is defined as the agglomerated charcoal portion, and this agglomerated charcoal portion is excluded from the analysis by being treated as having no pixel data. An expansion process is performed (n+1) or more times, starting from the periphery of the molded charcoal portion and expanding by one unit volume each time in a shape similar to the molded charcoal portion, where n is a natural number. The (n+1) is the number at which the average density of the region whose volume increased in the (n+1)th expansion process is approximately the same as the average density of the region whose volume increased in the nth expansion process. The average density of the region whose volume increased in the nth and subsequent expansion processes is used as the threshold. In each expansion treatment, the region whose volume increases is defined as follows: the region where the density exceeds the threshold is defined as the pulverized coal portion, and the region where the density is below the threshold is defined as the void portion. For each expansion treatment, the difference between the average density of the pulverized coal portion and the average density of the void portion is calculated for the region whose volume has increased. The amount of filling reduction is calculated by multiplying the volume of the region that has increased in volume during each expansion process by the difference value. The cumulative amount of filling loss is calculated by accumulating the aforementioned filling loss over the total number of expansion treatments. The method is A method for producing coke.

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