Method for producing coke

Abstract

To provide a method for producing coke capable of estimating coke strength with high accuracy and simplicity by precisely estimating the degree of coke strength reduction caused by the influence of voids around molded coal.SOLUTION: A method for estimating coke strength comprises: calculating a weighted average DI1506 (a1) of each test coal blend; determining a lower limit value (c1) of SV for the molded coal part based on the measured DI1506 (b1) of each test coal blend; calculating ΔDI for low SV test coal blends containing test molded coal having an SV lower than (c1); calculating a change degree of ΔDI (d1); deriving a relational expression between (d1) and the void filling degree of test fine coal; calculating a weighted average DI1506 (a2) in a coal blend to be used; and in the case (i) where the SV of the molded coal to be used is equal to or higher than (c1), setting (a2) as the target coke strength estimation value; or in the case (ii) where the SV of the molded coal to be used is lower than (c1), calculating ΔDI by multiplying the difference between (c1) and the molded coal SV by (d1), and setting a value obtained by subtracting ΔDI from (a2) as the target coke strength estimation value.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a method for estimating coke strength and a method for producing coke. [Background technology]

[0002] Conventionally, in the manufacture of coke used in blast furnace operation, various methods have been considered for maintaining good coke strength while increasing the blending ratio of inferior coal such as non- or slightly caking coal in a coal blend consisting of molded coal and pulverized coal, as a measure against the depletion of high-quality highly caking coal resources. In order to obtain a desired coke strength using a coal blend containing inferior coal, a coal pretreatment process can be useful. For example, as a coal drying process, a moisture-controlled coal charging method (Coal Moisture Coal; CMC), a pulverized coal agglomeration method (Dry-cleaned and Agglomerated Pre-compaction System; DAPS), etc. are known, and as a process for blending molded materials such as molded coal, a pulverized coal agglomeration method (Dry-cleaned and Agglomerated Precompaction System; DAPS), a molded coal blending method, and other methods for adjusting the crushed particle size of coal are known, and these are appropriately combined.

[0003] The above-mentioned coal pretreatment process is appropriately used to adjust the particle size composition and moisture content of the powdered coal, which is useful in terms of reducing the remaining voids in the coke and obtaining good coke strength even when the powdered coal has a relatively low expansion property. However, when molded coal is blended, voids are generated around the molded coal, and the voids around the molded coal may remain even after carbonization. In order to obtain good coke strength, it is advantageous for the blended coal to have sufficient expansion to fill the voids around the molded coal during carbonization.

[0004] Patent Document 1 describes a method for determining the strength of coke obtained from a mixture of briquettes and powdered coal by estimating the coke strengths of the briquettes and powdered coal parts and then calculating a weighted average according to the weight ratio of the two parts at the time of coking. The coke strength of the briquettes is estimated from the particle size, true specific gravity, volatile matter, expansion coefficient, and content of fine texture components of the raw materials constituting the briquettes, and the apparent density of the briquettes, as well as the heating rate and final carbonization temperature as carbonization conditions. The coke strength of the powdered coal part is estimated from the particle size, true specific gravity, volatile matter, expansion rate, content of fine structure components of the raw materials constituting the powdered coal part, and the bulk density of the powdered coal part, as well as the heating rate and final distillation temperature as distillation conditions, and the apparent density of the molded coal and the bulk density of the powdered coal are determined taking into consideration that the powdered coal part will be consolidated if the expansion volume of the molded coal part in the softening and melting temperature range exceeds the molded coal volume before distillation.

[0005] Patent Document 2 describes a method for estimating coke strength in which high-rank coal and low-rank coal are blended, the amount of fine coke generated by surface destruction of the coke (amount of surface-destroyed fine coke) and the amount of fine coke generated by volume destruction of the coke (amount of volume-destroyed fine coke) are estimated based on the coal properties measured for each blended coal before carbonization, and the coke strength after carbonization is estimated from the sum of the amounts of surface-destroyed fine coke and volume-destroyed fine coke, characterized in that the amount of volume-destroyed fine coke is estimated based on the average reflectance of the blended coal.

[0006] Patent Document 3 discloses a coke production method in which molded coal and a coal blend made by blending crushed coal powder are charged into a coke oven and carbonized, the method comprising the steps of: using a testing device, filling a container with the molded coal and the coal blend made by blending crushed coal powder by gravity; taking a cross-sectional image of the inside of the container by X-ray CT; quantifying the maximum width W of the void formed around the molded coal from the obtained cross-sectional image; measuring the maximum expansion volume of the molded coal during carbonization using the testing device; determining the amount of expansion of the molded coal as the change in circle equivalent diameter Δr (mm) before and after expansion; and changing the coal blend constituting the molded coal if the obtained change Δr is less than 40% of the maximum width W (mm); and determining a coal blend such that the change Δr is 40% or more of the maximum width W; and using the molded coal produced based on this blend. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 174951 / 1983 [Patent Document 2] JP 2005-194358 A [Patent Document 3] JP 2014-224242 A Summary of the Invention [Problem to be solved by the invention]

[0008] In the method described in Patent Document 1, the estimated coke strength of a coal blend is calculated by taking a weighted average of the estimated coke strengths of the molded coal portion and the powder coal portion, but since such additivity does not always hold, there are still problems in accurately estimating the coke strength. Patent Document 2 describes a method for estimating the coke strength of coke produced from powder coal, but does not mention estimating the coke strength of coke produced from a coal blend containing molded coal and powder coal.

[0009] In the method described in Patent Document 3, determining the blend of molded coals that ensures expansion (specific expansion volume SV) that does not cause a decrease in coke strength due to the influence of voids around the molded coals can be useful for producing high-strength coke. However, in this method, it was found that when the type of powdered coal is changed, the correspondence between the SV value of the molded coals of the blend determined based on the target coke strength and the target coke strength does not necessarily match the correspondence between the measured SV value of the molded coals and the measured coke strength. Therefore, in order to estimate the coke strength with higher accuracy, it has been desired to estimate the degree of decrease in coke strength due to the influence of voids around the molded coals with higher accuracy.

[0010] An object of one aspect of the present invention is to solve the above-mentioned problems and to provide a method for easily estimating coke strength with high accuracy or simply producing coke of desired strength by estimating with high accuracy the degree of reduction in coke strength caused by voids around molded coal when blended coal is carbonized. [Means for solving the problem]

[0011] The gist of the present invention is as follows. [1] A method for estimating the strength of coke produced by carbonizing a blended coal containing molded coal and powdered coal, comprising the steps of: A plurality of test coal blends are prepared, each of which is a combination of a plurality of test pulverized coals having different void filling degrees (SV×BD), which is the product of expansion specific volume SV and bulk density BD, and a plurality of test briquettes having different expansion specific volumes (SV); Actual measured DI of each test powder coal and each test briquette coal 150 Weighted average DI of each test coal blend based on 6 (drum index) 150 6(a1) is calculated, Actual measured DI of each test coal blend 150 Based on 6(b1), the DI of the blended coal was not affected by the change in the SV of the briquettes. 150 A lower limit value (c1) of the briquette part SV range in which 6 is constant is calculated, Among the multiple types of test coal blends, the weighted average DI of the low SV test coal blends including the test coal blends having an SV less than the SV lower limit (c1) of the briquette part is 150 6(a1) and actual DI 150 Calculate ΔDI, which is the difference from 6(b1), Based on the relationship between the SV of the briquette coal part of the low SV test coal blend and the ΔDI, a ΔDI change rate (d1) is calculated, which is the change in ΔDI per unit change in the briquette coal part SV; A relationship between the ΔDI change rate (d1) and the void filling rate of the test powder coal is obtained, In a coal blend containing powder coal to be used and briquettes to be used, the measured DI of each of the powder coal and briquettes 150 Weighted average DI of blended coal based on 6 150 6(a2) is calculated, (i) When the SV of the briquettes to be used is equal to or greater than the lower limit SV of the briquettes (c1), the weighted average DI of the briquettes is 150 6(a2) is the desired coke strength estimate, (ii) If the SV of the briquettes to be used is less than the lower limit of the SV of the briquettes (c1), the difference between the lower limit of the SV of the briquettes (c1) and the SV of the briquettes is multiplied by the change in ΔDI (d1) to calculate ΔDI, and the weighted average DI of the briquettes to be used is calculated. 150 The value obtained by subtracting the ΔDI from 6(a2) is the target coke strength estimate. Method for estimating coke strength. [2] A method for producing coke using a blended coal containing molded coal and powdered coal, comprising: A plurality of test coal blends are prepared, each of which is a combination of a plurality of test pulverized coals having different void filling degrees (SV×BD), which is the product of expansion specific volume SV and bulk density BD, and a plurality of test briquettes having different expansion specific volumes (SV); Actual measured DI of each test powder coal and each test briquette coal 150 Weighted average DI of each test coal blend based on 6 (drum index) 150 6(a1) is calculated, Actual measured DI of each test coal blend 150 Based on 6(b1), the DI of the blended coal was not affected by the change in the SV of the briquettes. 150A lower limit value (c1) of the briquette part SV range in which 6 is constant is calculated, Among the multiple types of test coal blends, the weighted average DI of the low SV test coal blends including the test coal blends having an SV less than the SV lower limit (c1) of the briquette part is 150 6(a1) and actual DI 150 Calculate ΔDI, which is the difference from 6(b1), Based on the relationship between the SV of the briquette coal part of the low SV test coal blend and the ΔDI, a ΔDI change rate (d1) is calculated, which is the change in ΔDI per unit change in the briquette coal part SV; A relational expression between the ΔDI change rate (d1) and the void filling rate of the test powder coal is obtained, and a void filling rate lower limit value (e1) at which the ΔDI change rate (d1) is equal to or less than a preset value (α) is obtained based on the relational expression; (i) using briquettes having an SV equal to or greater than the lower limit SV (c1) of the briquettes, and / or (ii) Using briquettes having an SV less than the lower limit SV (c1) of the briquettes, and using pulverized coal having a void filling degree equal to or greater than the lower limit SV (e1); Coke manufacturing method. Effect of the Invention

[0012] According to one aspect of the present invention, a method can be provided for estimating with high accuracy the degree of coke strength reduction caused by voids around molded coal when blended coal is carbonized, thereby enabling coke strength to be estimated with high accuracy and in a simple manner, or for simply producing coke of desired strength. [Brief description of the drawings]

[0013] [Figure 1] FIG. 3 is a graph showing the relationship between the briquette coal part SV and the DI1506 of the coke for levels 1 to 8 in Example 1. [Diagram 2] FIG. 3 is a diagram showing the relationship between the briquette coal part SV and the DI1506 of the coke for levels 9 to 12 in Example 1. [Diagram 3]FIG. 1 is a diagram showing the relationship between the briquette coal part SV and the DI1506 of the coke for levels 13 to 17 in Example 1. [Figure 4] FIG. 1 is a diagram showing the relationship between the briquette coal part SV and the DI1506 of the coke for levels 20 to 27 in Example 1. [Diagram 5] FIG. 1 is a diagram showing the relationship between the void filling rate of the powder coal portion and the rate of change in ΔDI in Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an exemplary embodiment of the present invention (sometimes referred to as the present embodiment in this disclosure) will be described, but the present invention is not limited to the following embodiment.

[0015] In this embodiment, DI (drum index) is used as an index of coke strength. In general, the surface fracture strength of coke can be expressed as a percentage of the mass of oversized coke (particle size over 6 mm) sieved through a 6 mm mesh sieve after a drum is rotated a predetermined number of times in a drum test (hereinafter, sometimes referred to as "DI6") to the total mass of charged coke, and the volumetric fracture fineness of coke can be expressed as a percentage of the mass of oversized coke (particle size over 6 mm) sieved through a 15 mm mesh sieve after a drum is rotated a predetermined number of times (hereinafter, sometimes referred to as "DI6") to the total mass of charged coke. 6-15 The coke undersize (particle size 15 mm or less) sieved through a 15 mm sieve after a specified number of drum revolutions contains a mixture of powder under the 6 mm sieve generated by surface destruction and powder over the 6 mm sieve and under the 15 mm sieve generated by volume destruction. The percentage of the mass of oversize coke (particle size over 15 mm) sieved through a 15 mm sieve after a specified number of drum revolutions to the total mass of charged coke (hereinafter referred to as "DI") 15 ") is DI6 to DI 6-15 The rotation speed of the drum test may be any value in the range of 10 to 150, and a typical example of the rotation speed is 150. In one embodiment, the index of coke strength is DI150 6, and in one embodiment DI 150 15 It may be. In view of the above, in this embodiment, DI is used as the coke strength. 150 This focuses on 6.

[0016] For stable blast furnace operation, it is important that the coke quality is stable throughout the operation. In other words, when the coke strength decreases during operation, it is necessary to determine the cause and then determine the operating conditions that can prevent the coke strength decrease. In this case, it is not realistic to consider all possible causes during blast furnace operation. Therefore, it is advantageous to identify in advance several factors that may be particularly useful for preventing the coke strength decrease and to be able to estimate the coke strength based on these factors.

[0017] In order to obtain good coke strength, it is important that the coal blend has sufficient expansion to fill the voids around the briquettes during carbonization. For example, the surface fracture strength DI between the briquettes and the powder coal of the coal blend is 150 The DI of the coal blend itself is calculated by measuring the DI of the coal blend itself and taking a weighted average according to the blending ratio of the briquettes and the powdered coal. 150 Without actually measuring 6, the surface destruction strength DI of the blended coal 150 6 can be estimated. The surface destruction powder of coke is generated due to insufficient softening, melting, and expansion of the raw coal, and is generated by local destruction in the part that received the drop impact. Therefore, the amount of destruction powder generated per drop impact is determined by the original structure of the part that received the drop impact. In other words, when the coke generated from the molded coal part and the coke generated from the pulverized coal part do not affect each other, the weighted average of the surface destruction strength holds, and the DI of the molded coal part can be estimated. 150 6 and DI of powdered coal 150 The weighted average of these two is the surface fracture strength DI of the blended coal. 150 It can be determined as an estimate of 6.

[0018] However, depending on the blend of briquettes and powdered coal, the weighted average DI 1506 and actual DI 150 6 may not match. This is thought to be due to the expansion property (expansion specific volume SV) of the briquettes. When briquettes are blended, gaps exist between the briquettes and the powder coal. If the expansion property of the briquettes is low, the gaps between the briquettes and the powder coal remain even after carbonization, and the powder coal near the interface between the briquettes and the powder coal expands freely, so the strength of the coke in the powder coal part near the interface between the briquettes and the powder coal is lower than when only the powder coal is carbonized. This is thought to be the reason why the estimated value based on the weighted average may not be close to the actual measured value. Therefore, the DI of the blended coal 150 In order to make the estimated value of 6 closer to the actual measured value, it is necessary to consider the influence of the voids around the briquettes on the DI 150 It is necessary to quantitatively estimate the degree of decrease in 6 (also referred to as the "void effect" or "ΔDI" in this disclosure) and calculate an estimated value that takes this void effect (ΔDI) into account.

[0019] When the SV of the briquettes of a coal blend falls below a certain value, the DI of the coke generated from the coal blend decreases with the decrease in the SV. 150 In general, it is assumed that coke is produced under conditions that do not cause void effects (ΔDI). However, the briquette SV can fluctuate during actual operation due to changes in the composition of incoming coal, changes in the briquette mix due to operating conditions, etc. This fluctuation can cause the briquette to no longer have sufficient expansiveness to fill the voids around the briquette, resulting in a decrease in DI. 150 6 may decrease. Furthermore, according to the study by the present inventors, even if only the briquette SV is taken into consideration, the accuracy of the estimation of the void effect (ΔDI) may not be high, that is, the amount of the void effect (ΔDI) is affected not only by the briquette SV but also by other factors. As the other factors, various coke production conditions (for example, coal properties of the powder coal part, charging density, etc.) are considered.

[0020] In view of the above, the present inventors have studied to identify the main factors that affect the void effect (ΔDI). As a result, they have found that in addition to the molded coal part SV, the void filling degree (SV × BD), which is the product of the expansion specific volume SV and the bulk density BD of the powder coal part, greatly affects the void effect (ΔDI). The void filling degree of the powder coal part is an index that indicates the ratio of the space that can be filled by expanded coal in a unit volume. According to this embodiment, by adopting a combination of the molded coal part SV and the void filling degree (SV × BD) of the powder coal part as an index, it is possible to realize a highly accurate estimation of the void effect (ΔDI). The fact that only two indices, the molded coal part SV and the void filling degree (SV × BD) of the powder coal part, are sufficient is also advantageous in terms of simplicity. By such a highly accurate estimation of the void effect (ΔDI), a method for estimating coke strength with high accuracy and simply, and a method for simply manufacturing coke of a desired strength can be provided.

[0021] [Method of estimating coke strength] One aspect of the present invention provides a method for estimating the strength of coke produced by carbonizing a coal blend containing molded coal and powdered coal. In this disclosure, powdered coal refers to pulverized coal, and includes coal whose particle size has been further adjusted after pulverization, and agglomerated coal when agglomerated coal is mixed. In this disclosure, agglomerated coal refers to coal with a spherical equivalent radius of less than 6 mm obtained by adding a caking filler to powdered coal (powdered coal under a 0.3 mm sieve in one aspect) and molding under pressure. In this disclosure, molded coal refers to coal with a spherical equivalent radius of 6 mm or more obtained by adding a caking filler to powdered coal (powdered coal under a 0.3 mm sieve in one aspect) and molding under pressure. A coal blend is a combination of molded coal and powdered coal.

[0022] In one aspect of the present invention, a method for estimating coke strength includes: A plurality of test coal blends are prepared, each of which is a combination of a plurality of test pulverized coals having different void filling degrees (SV×BD), which is the product of expansion specific volume SV and bulk density BD, and a plurality of test briquettes having different expansion specific volumes (SV); Actual measured DI of each test powder coal and each test briquette coal 150 Weighted average DI of each test coal blend based on 6 (drum index) 150 6(a1) is calculated, Actual measured DI of each test coal blend 150 Based on 6(b1), the DI of the blended coal was not affected by the change in the SV of the briquettes. 150 A lower limit value (c1) of the briquette part SV range in which 6 is constant is calculated, Among the multiple types of test coal blends, the weighted average DI of the low SV test coal blends including the test coal blends having an SV less than the SV lower limit (c1) of the briquette part is 150 6(a1) and actual DI 150 Calculate ΔDI, which is the difference from 6(b1), Based on the relationship between the SV of the briquette coal part of the low SV test coal blend and the ΔDI, a ΔDI change rate (d1) is calculated, which is the change in ΔDI per unit change in the briquette coal part SV; A relationship between the ΔDI change rate (d1) and the void filling rate of the test powder coal is obtained, In a coal blend containing powder coal to be used and briquettes to be used, the measured DI of each of the powder coal and briquettes 150 Weighted average DI of blended coal based on 6 150 6(a2) is calculated, (i) When the SV of the briquettes to be used is equal to or greater than the lower limit SV of the briquettes (c1), the weighted average DI of the briquettes is 150 6(a2) is the desired coke strength estimate, (ii) If the SV of the briquettes to be used is less than the lower limit of the SV of the briquettes (c1), the difference between the lower limit of the SV of the briquettes (c1) and the SV of the briquettes is multiplied by the change in ΔDI (d1) to calculate ΔDI, and the weighted average DI of the briquettes to be used is calculated. 150 The value obtained by subtracting the ΔDI from 6(a2) is the target estimated coke strength value. An example procedure for each step will be described below.

[0023] <Preparation of test coal blends> First, a plurality of types of test coal blends are prepared, which are combinations of a plurality of types of test coal briquettes with different void filling degrees (SV×BD), which is the product of the expansion specific volume SV and the bulk density BD. It is preferable to select a test coal briquettes that are free of defects. Factors that affect the void filling degree of the powdered coal include mainly the particle size composition of the powdered coal and the moisture content of the powdered coal. It is considered that the moisture content of the powdered coal affects the void filling degree by affecting the fluidity of the powdered coal. Therefore, in one embodiment, a plurality of types of powdered coal with different particle size composition and / or moisture content may be selected as the test powdered coal. The test powdered coal is composed of a level group having a void filling degree of 2 or more, preferably 3 or more different values ​​in one embodiment. From the viewpoint of estimation accuracy, it is advantageous to have a large number of different values, but from the viewpoint of work efficiency, the number of different values ​​may be 10 or less, or 8 or less in one embodiment. The test molded coal is composed of a group of levels having SV values ​​of 4 or more, preferably 5 or more. 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. The SV of the molded coal can be adjusted to a desired value, for example, by adjusting the type and / or amount of coal and / or caking filler used in the production of the molded coal.

[0024] <Actual DI 150 6 and weighted average DI 150 6> The DI values ​​measured for the test powder coal and test briquettes prepared above were 150 Based on 6, the weighted average DI of each test coal blend was calculated. 150 6(a1) is calculated. The drum test is performed in accordance with JIS K2151 for coke made only from powder coal and for coke made only from molded coal. 150 6 and the measured DI of molded coal 150 6 and 7 are weighted by the blending ratio of powder coal and briquettes in the blended coal to obtain the weighted average DI 150 6. In one embodiment, the blending ratio may be based on mass.

[0025] <Lower limit value of molten coal SV> Measured DI of test coal blend 150 Based on 6(b1), the DI of the blended coal was not affected by the change in the SV of the briquettes. 150 The lower limit of the briquette part SV range (c1) where 6 is constant is determined. An example of the procedure is as follows. a) For coke made from each test coal blend, a drum test was conducted in accordance with JIS K2151, and the measured DI 150 We get 6(b1). a) For each test coal blend, the SV is measured by a carbonization test using a dilatometer in accordance with JIS M8801. 3 / g) is the volume (cm) that 1 g of coal occupies after expansion 3 ) is an indicator that means b) For all test coal blends, the relationship between the briquette part SV (x-axis) and the measured DI (b1) (y-axis) is plotted for each level of fine coal. For example, when three levels of fine coal and ten levels of briquettes are selected, a first plot is prepared for the test coal blends relating to the combination of the first level of fine coal with each of the first to tenth levels of briquettes, a second plot is prepared for the test coal blends relating to the combination of the second level of fine coal with each of the first to tenth levels of briquettes, and a third plot is prepared for the test coal blends relating to the combination of the third level of fine coal with each of the first to tenth levels of briquettes. For each plot, the DI 150 The minimum value of the briquette SV in the region where DI 6 is maintained constant regardless of the value of the briquette SV is defined as the lower limit value (c1) of the briquette SV. 150 The region where DI 6 remains constant regardless of the value of the briquette SV is the region where DI 150 This means the region where the value of DI 6 falls within the standard deviation. For example, if the standard deviation of each plot is 0.4, the region where the coke strength is maintained constant regardless of the value of the briquette SV is the region where the coke strength falls within the range of ±0.4. In this way, the lower limit of the briquette SV for each level of powder coal is obtained. Note that the measured DI of the test coal blend increases with an increase in the briquette SV (x-axis). 150If the rate at which 6(b1) (y-axis) increases changes obviously and remains roughly the same, it can be considered a region that remains constant, and the judgment is not limited to the standard deviation.

[0026] <ΔDI> Among multiple types of test coal blends, the weighted average DI of low SV test coal blends including test coal briquettes with SV below the lower limit of the briquettes SV (c1) obtained above was used. 150 6(a1) and actual DI 150 Calculate ΔDI, which is the difference from 6(b1).

[0027] <ΔDI change rate (d1)> Based on the relationship between the briquette SV of the low SV test coal blend and the ΔDI calculated above, the ΔDI change rate (d1) is calculated, which is the change in ΔDI per unit change in the briquette SV. In one embodiment, the relationship between the briquette SV (x-axis) of the low SV test coal blend and ΔDI (y-axis) is plotted, and the slope is calculated by, for example, linear approximation, and the slope is defined as the ΔDI change rate (d1).

[0028] <Relationship between ΔDI change rate (d1) and void filling rate of test coal> The relation between the ΔDI change rate (d1) obtained above and the void filling rate (SV × BD) of the test pulverized coal is derived. In one embodiment, the relation between the void filling rate (x-axis) of each test pulverized coal and the ΔDI change rate (d1) (y-axis) is plotted, and the following relation (I) is derived, for example, by linear approximation. [ΔDI change rate (d1)] = a × [void filling rate of test coal] + b (I) (In the formula, a and b are constants.)

[0029] Here, the expansion specific volume SV of pulverized coal may be measured by a carbonization test using a dilatometer in accordance with JIS M8801. SV (cm 3 / g) is the volume (cm) that 1 g of coal occupies after expansion 3) is an index that means the bulk density BD of the fine coal. In one embodiment, the bulk density when only the fine coal is charged may be checked in advance. The expansion specific volume SV is multiplied by the bulk density BD to calculate the void filling degree (SV × BD).

[0030] <Estimation of coke strength for blended coal to be used> Using the values ​​obtained in the above steps, the strength of the coke to be produced from the coal blend to be used is estimated. In a coal blend containing powder coal to be used and briquettes to be used, the measured DI of each of the powder coal to be used and the briquettes to be used 150 Weighted average DI of blended coal based on 6 150 Calculate 6(a2). DI 150 6 Actual measurements and weighted average DI 150 The calculation of 6 may be performed in the same manner as described above for the test coal powder, briquettes, and blended coal. The SV of the briquettes to be used is measured. The SV may also be measured in the same manner as described above for the test coal briquettes. (i) If the SV of the briquettes to be used is equal to or greater than the lower limit (c1) of the briquettes calculated above, the weighted average DI of the blended coal is calculated. 150 6(a2) is the desired coke strength estimate, (ii) If the SV of the briquette coal to be used is less than the lower limit of the SV of the briquette coal (c1) calculated above, multiply the difference between the lower limit of the SV of the briquette coal (c1) calculated above and the SV of the briquette coal to be used by the ΔDI change rate (d1) calculated above to calculate ΔDI, and use this as the weighted average DI of the blended coal to be used. 150 The target coke strength estimate is calculated by subtracting the ΔDI from 6(a2).

[0031] When the SV of the coal briquette to be used is equal to or greater than the lower limit of the SV of the coal briquette (c1), it means that the coal briquette to be used has sufficient expansiveness to fill the voids around the coal briquette during carbonization. In this case, the weighted average DI of the coal blend to be used is 150 6 is the measured DI of the coal blend 150 Since the value is sufficiently close to 6, the weighted average DI of the blended coal can be calculated without considering the effect of voids (ΔDI). 1506 can be used as the estimated coke strength. On the other hand, if the SV of the briquette to be used is less than the lower limit of the briquette SV (c1), it means that the briquette to be used does not have sufficient expansion to fill the voids around the briquette during carbonization. Therefore, in this case, the estimated coke strength is calculated taking into account the void effect (ΔDI).

[0032] <DI 150 15 Estimates of According to the procedure described above, the DI as coke strength 150 As mentioned above, the coke strength related to the estimation is DI 150 Not limited to 6. For example, DI 150 6 to DI 150 6-15 By adding an additional step of subtracting DI 150 15 It is also possible to estimate DI 150 6-15 There is no particular limitation on the method of determining DI, and in one embodiment, it may be calculated from the shrinkage rate of coal. 150 6-15 may be an estimated value that can be calculated using known techniques (for example, the techniques described in JP 2020-94200 A). 150 6-15 The volumetric destruction fine ratio, expressed as: is an index of volume destruction, i.e. destruction caused by cracks generated by thermal stress resulting from uneven shrinkage of the entire coke. The DI, which is the coke strength taking into account surface destruction and volume destruction, 150 15 It may be useful in one embodiment to estimate

[0033] [Coke manufacturing method] One aspect of the present invention also provides a method for producing coke using a coal blend containing briquettes and powdered coal. In one aspect, a lower limit of the briquettes SV, which is the limit value at which the coke strength does not decrease when the briquettes SV is lowered, is determined, and a briquettes showing the lower limit of the briquettes SV or higher is selected and used to produce a high-strength coke. The lower limit of the briquettes SV indicates the limit at which the briquettes SV can be lowered (i.e., a lower quality briquettes can be used) without causing a decrease in coke strength due to the briquettes (more specifically, due to the free expansion of a part of the powdered coal due to insufficient expansion of the briquettes during coking) in a coal blend containing powdered coal to be used. Briquettes with a low SV can be inexpensive because of their inferior quality. Therefore, it is more advantageous to select and use briquettes that are equal to or higher than the lower limit of the briquettes SV but close to the lower limit in terms of obtaining high-strength coke at low cost. In one embodiment, the variation in briquette SV in actual operation is typically ±0.1 cm. 3 Considering that the SV of the molded coal is about 0.1 cm 3 By blending briquettes having an SV equal to or greater than the lower limit of the briquettes SV with the powdered coal to be used, it is possible to produce high strength coke.

[0034] On the other hand, when a low coke strength is predicted because the SV of the briquettes to be used is below the lower SV limit, such a coke strength may still be acceptable for practical use, and it is useful to estimate the void effect ΔDI with high accuracy in order to determine the coal blend composition that ensures the desired level of coke strength.

[0035] In one embodiment of the present invention, a method for producing coke using a blended coal containing briquettes and powdered coal is provided. A plurality of test coal blends are prepared, each of which is a combination of a plurality of test pulverized coals having different void filling degrees (SV×BD), which is the product of expansion specific volume SV and bulk density BD, and a plurality of test briquettes having different expansion specific volumes (SV); Actual measured DI of each test powder coal and each test briquette coal 150 Weighted average DI of each test coal blend based on 6 (drum index)150 6(a1) is calculated, Actual measured DI of each test coal blend 150 Based on 6(b1), the DI of the blended coal was not affected by the change in the SV of the briquettes. 150 A lower limit value (c1) of the briquette part SV range in which 6 is constant is calculated, Among the multiple types of test coal blends, the weighted average DI of the low SV test coal blends including the test coal blends having an SV less than the SV lower limit (c1) of the briquette part is 150 6(a1) and actual DI 150 Calculate ΔDI, which is the difference from 6(b1), Based on the relationship between the SV of the briquette coal part of the low SV test coal blend and the ΔDI, a ΔDI change rate (d1) is calculated, which is the change in ΔDI per unit change in the briquette coal part SV; A relational expression between the ΔDI change rate (d1) and the void filling rate of the test powder coal is obtained, and a void filling rate lower limit value (e1) at which the ΔDI change rate (d1) is equal to or less than a preset value (α) is obtained based on the relational expression; (i) using briquettes having an SV equal to or greater than the lower limit SV (c1) of the briquettes, and / or (ii) Briquettes having an SV of the briquettes less than the lower limit SV (c1) are used, and pulverized coal having a void filling degree equal to or greater than the lower limit void filling degree (e1) is used. An example procedure for each step in the coke production method will now be described.

[0036] First, a test coal blend was prepared in the same manner as described above for the method of estimating coke strength, and the actual DI 150 6 and weighted average DI 150 6. Determine the void filling rate of the powder coal (SV × BD), the lower limit of SV of the molded coal part, ΔDI, the rate of change in ΔDI (d1), and the relationship between the rate of change in ΔDI (d1) and the void filling rate of the test powder coal. Next, based on the relational expression between the ΔDI change rate (d1) and the void filling rate of the test powder coal, a void filling rate lower limit value (e1) is obtained at which the ΔDI change rate (d1) is equal to or less than a preset value (α). The value (α) is equal to or greater than 0, and may be preset so as to obtain coke having an acceptable strength according to the intended use. For example, in cases where the estimated value of the coke strength exceeds the operational control value, the value (α) (i.e., the upper limit value of the acceptable ΔDI change rate (d1)) can be set to more than 0. The procedure for setting the value (α) is not particularly limited. As an example, when the void filling rate of the powder coal part is less than 1.0, the coke strength of the powder coal part itself may be too low, making it difficult to maintain the strength required for blast furnace coke. In this case, the value of the ΔDI change rate corresponding to a void filling rate of 1.0 of the powder coal part can be set to the value (α). In the example of FIG. 5 described later, the value (α) can be set to 25. As another example, the value (α) may be set in consideration of the variation in coke strength during operation. For example, an allowable variation (such as ±2σ) of coke strength may be determined on the assumption that the coke strength may vary from a reference value during operation. The allowable lower deviation width (such as 2σ when the allowable variation is ±2σ) of the coke strength corresponding to this allowable variation may be divided by the variation of the molded coal part SV itself, and the value (α) may be set to this value. In one embodiment, the value (α) may be 0.

[0037] The following formula (I) [ΔDI change rate (d1)] = a × [void filling rate of test coal] + b (I) (In the formula, a and b are constants.) In the above, the value calculated as the void filling degree of the test powder coal when the value (α) is substituted for the ΔDI change rate (d1) is defined as the void filling degree lower limit value (e1). For example, when the value (α) is 0, the following formula: 0 = a × [void filling degree of test coal] + b The lower limit of the void filling degree (e1) may be determined according to the following:

[0038] And depending on the desired coke strength, (i) using briquettes having an SV equal to or greater than the lower limit SV of the briquettes (c1); and / or (ii) Using briquettes having a SV less than the lower limit of the briquettes (c1) and using pulverized coal having a void filling degree equal to or greater than the lower limit of the void filling degree (e1), coke having a desired strength can be easily produced.

[0039] Briquettes having an SV equal to or greater than the lower limit (c1) of the briquettes have sufficient expansiveness to fill the voids around the briquettes during carbonization. A blended coal containing such briquettes can ensure good coke strength. On the other hand, even when briquettes having an SV less than the lower limit (c1) of the briquettes are used, by combining them with powdered coal having a void filling degree equal to or greater than the lower limit (e1) of the void filling degree, the powdered coal also contributes to filling the voids around the briquettes during carbonization, thereby ensuring the desired coke strength. When powdered coal having a void filling degree equal to or greater than the lower limit (e1) of the void filling degree is used, the briquettes contained in the blended coal may be a combination of briquettes having an SV equal to or greater than the lower limit (c1) of the briquettes and briquettes having an SV less than the lower limit (c1) of the briquettes.

[0040] <Characteristics of coal> The raw coal and its blending used for estimating coke strength or producing coke are not particularly limited, but typical examples are as follows: (coking coal) The raw coal for use as the powdered coal and briquettes is not particularly limited, and may be a mixture of multiple types of coal that have been pulverized, or a single type of coal that has been pulverized. An example of the raw coal is a coal having a weighted average total expansion coefficient ΣTD of 20-100%, a weighted average volatile matter ΣVM of 20-32 dry%, and a weighted average vitrinite reflectance ΣRo of 0.7-1.3%, pulverized to a particle size of 60%-95% under 3 mm sieve ratio. The vitrinite reflectance Ro is measured by a method specified in JIS M8816.

[0041] In addition, the raw coal for briquettes may be a blend of good quality coal and poor quality coal in a blending ratio of 30 mass% or more. In the present disclosure, poor quality coal is coal having a total expansion coefficient TD of 50% or less, a volatile matter VM of 30 dry% or more, and an average vitrinite reflectance Ro of less than 0.8%.

[0042] (briquette charcoal) Briquette coal is produced by adding a binder to raw coal, kneading the mixture, and molding the mixture into a specific shape using a briquette machine. 3 ~125cm 3 , density is 1.1~1.2g / cm 3 Examples include those in the range of

[0043] The liquid binder added when producing molded coal is not particularly limited, and may be tar slag, coal tar, asphalt, or other bituminous binder. The amount of liquid binder added is, for example, 0.5 to 10.0 mass% based on the raw coal. When the amount is 0.5 mass% or more, molding is easy, and when the amount is 10.0 mass% or less, a decrease in packing density in the carbonization chamber caused by weak pseudo-particles formed by coal particles can be avoided. A solid binder may be added, and coal pitch, asphalt pitch, or other bituminous binder may be used.

[0044] (Blended coal) The blending ratio of the briquettes in the blended coal obtained by blending the briquettes with the powdered coal is not particularly limited, and is exemplified as 5 to 50 mass%. When the blending ratio is 50 mass% or less, the influence of segregation of the briquettes is not large, which is preferable. Also, when the blending ratio is 5 mass% or more, the effect of blending the briquettes with the blended coal is satisfactorily obtained. EXAMPLES

[0045] Hereinafter, exemplary embodiments of the present invention will be further described with reference to examples, but the present invention is not limited to these examples in any way.

[0046] [Example 1] Estimation of coke strength based on evaluation of void effect (ΔDI) (Coal used) The void effect ΔDI was evaluated for blended coals, which were made by blending powder coal with molded coal at a moisture content of 4 mass% or 10 mass%, through a carbonization test using a test coke oven.

[0047] Table 1 shows the properties of each coal, and Table 2 shows the blending conditions of the powder coal part in the blended coal using the coal in Table 1. Blending conditions 1 and 2 are granulated coal with a particle size of 0.3 to 3 mm (moisture content 4 mass%), blending conditions 3 and 4 are pulverized coal with a 3 mm undersieve ratio of 85% (i.e., the coal itself obtained by pulverization of the powder coal) (moisture content 4 mass%), and blending condition 5 is pulverized coal with a 3 mm undersieve ratio of 85% (however, moisture content 10 mass%). The 3 mm undersieve mass ratio as the crushed particle size was 92.5%, 93%, 85%, 85%, and 85% for blending conditions 1, 2, 3, 4, and 5, respectively. A tar-based caking filler was used as the liquid caking filler, and asphalt pitch (ASP) was used as the solid caking filler. The amount of caking filler in the table is shown as an external number to the dry coal.

[0048] Table 3 shows the blending ratio of the molded coal part. Powder coal with a crushed particle size of 3 mm and a mass ratio of 90% under the sieve was molded in blends 1 to 21 using a molding machine (BMS II manufactured by Shinto Kogyo Co., Ltd.) to produce molded coal. The molded coal was made into a pillow type with a particle size of about 40 mm. A tar-based binder was used as the liquid binder, and asphalt pitch (ASP) was used as the solid binder. For the three series of blending conditions 1 to 8, 9 to 13, and 14 to 21 of the molded coal part, in order to evaluate the influence of the molded coal part SV, the ΣVM was made almost the same value, while the molded coal part SV was made different. Table 4 shows the levels at which the powder coal part and the molded coal part were blended and carbonized in a test coke oven. The total expansion coefficients TD of the powder coal and briquette coal were measured in accordance with the method specified in JIS M8801. The results are shown in Tables 2 and 3.

[0049] (Measurement of SV of powdered coal and briquette coal) The expansion specific volume SV was determined using a dilatometer in accordance with the expansion test of JIS M8801. For the powdered coal portion, the powdered coal samples were prepared from the blending conditions shown in Table 2. For the briquetted coal portion, the briquetted coal samples were prepared from the blending conditions shown in Table 3, which were pulverized and adjusted to a particle size of 100% by mass of 3 mm sieve size. Each sample was pulverized to a bulk density of 1.10 g / cm using a briquetting machine for a dilatometer. 3 The mixture was placed in a reaction tube as a molded product with a height of 60 mm (on a dry basis). A carbonization test was performed by heating at a temperature increase rate of 3°C / min, and the SV was measured. The results are shown in Tables 2 and 3.

[0050] (DI by drum test 150 6 actual measurements) The drum test was performed in accordance with JIS K2151 at 150 revolutions and N=3. Powder coal with each blending condition shown in Table 2, briquettes with each blending condition shown in Table 3, and blended coals obtained by blending powder coal and briquettes at each level shown in Table 4 were each carbonized in a test coke oven to produce coke, which was then subjected to a drum test. The coke after the test was sieved through a 6 mm mesh sieve, and the percentage of the mass of the coke on the sieve (particle size over 6 mm) to the total mass of the charged coke was calculated as the DI. 150 It was calculated as 6. In addition, the weighted average DI of the blended coal 150 6 was calculated based on the following formula. Weighted average DI of blended coal 150 6 = (Measured DI of powdered coal 150 6) × (mass ratio of powder coal in blended coal) + (measured DI of briquetted coal) 150 6) × (mass ratio of briquettes in blended coal) The results are shown in Tables 4 and 5.

[0051] As shown in Figs. 1 to 4, the measured values ​​of the briquette SV and the measured DI for the blended coal 150 The relationship between the SV and the value of 6 was plotted for each blending condition of the powder coal part. Based on these plots, the lower limit of the briquette coal part SV, which is the limit at which the coke strength is maintained constant, was obtained.

[0052] As shown in Fig. 1, for levels 1 to 8 (powder coal part is granulated coal of blending condition 1, moisture content 4 mass%, void filling degree 0.99), the SV of the molded coal part is 1.04 cm3 / g or higher DI 150 6 were almost the same (i.e., within the standard deviation), but the SV of the briquette was 0.93 cm 3 / g, and 0.90cm 3 / g, the DI 150 6 was significantly decreased. Therefore, the SV of the molded coal part was 0.90 cm 3 / g and 0.93cm 3 The relation obtained by connecting the plots of [DI 150 6] = 42.5 × [molded coal SV] + 45.2 and the DI of other plots 150 The intersection point with the line showing the average value of 86.4 for 6 was determined as the lower limit of the SV of the briquettes, which was 0.97 cm 3 / g.

[0053] Similarly, as shown in Fig. 2, for levels 9 to 12 (powder coal part is granulated coal of blending condition 2, moisture content 4 mass%, void filling degree 1.20), the SV of the molded coal part is 0.90 cm 3 / g and 0.93cm 3 The relation obtained by connecting the plots of [DI 150 6]=26.2×[molded coal part SV]+61.2 and other plots of DI 150 The average value of 6 was 86.7. As a result, the lower limit of the SV of the molded coal was 0.97 cm 3 / g.

[0054] Similarly, as shown in Fig. 3, for levels 13 to 17 (fine coal part is pulverized coal of blending condition 3, moisture content is 4 mass%, void filling degree is 1.38), the SV of the molded coal part is 0.97 cm 3 / g, 1.04cm 3 / g, and 1.10 cm 3 The relationship obtained by linear approximation of the plot of / g is [DI 150 6]=5.35×[molded coal part SV]+82.5 and other plots and the above 1.10 cm 3 DI / g 150The average value of 6 was 88.5. Based on this, the lower limit of the briquette SV was calculated to be 1.12. However, in levels 13 to 17, the briquette SV was 1.10 cm 3 / g or higher measured DI 150 6 were almost the same (i.e., within the standard deviation), so the lower limit of the SV of the briquette was 1.10 cm 3 / g.

[0055] Similarly, as shown in Fig. 4, for levels 20 to 27 (fine coal part is pulverized coal of blending condition 5, moisture content is 10 mass%, void filling degree is 1.40), the SV of the molded coal part is 1.23 cm 3 / g, 1.29cm 3 / g, 1.38cm 3 / g, 1.40cm 3 The relationship obtained by linear approximation of the plot of / g is [DI 150 6]=3.46×[molded coal part SV]+81.0 and other plots of DI 150 The average value of 6 was 86.1. As a result, the lower limit of the SV of the molded coal was 1.47 cm 3 / g.

[0056] From the above results, it can be seen that the coal blend using pulverized coal tended to have a higher SV lower limit of the briquette coal part than the coal blend using granulated coal.

[0057] (Calculation of void effect ΔDI) Next, the weighted average DI for blended coal 150 6 and actual DI 150 The difference between the briquette part SV and the actual DI of the blended coal was calculated as the void effect ΔDI. However, in the level shown in Table 5, even for the briquette part SV that was equal to or greater than the lower limit of the briquette part SV, the difference was not zero. This is due to the measurement accuracy and the measured DI of the blended coal. 150This is considered to be due to the measurement variation of 6. Therefore, in this example, in order to treat the ΔDI of the level using molded coal having an SV equal to or greater than the lower limit of the molded coal part SV as zero, the following correction was made. Specifically, for the level below the lower limit of the molded coal part SV, the value obtained by subtracting the average value of the above differences in the level using molded coal having an SV equal to or greater than the lower limit of the molded coal part SV from the above differences was adopted as the ΔDI (corrected value). This eliminated the effects of measurement accuracy and measurement variation.

[0058] (Calculation of ΔDI change rate) Next, for the level using briquette coal with SV below the lower limit of the briquette coal SV, the briquette coal SV was plotted on the x-axis and ΔDI (corrected value) on the y-axis, and linear approximation was performed. The slope of the linear equation was defined as the degree of change in ΔDI. In other words, the degree of change in ΔDI was calculated by dividing the unit change in the briquette coal SV (1.0 cm 3 The results are shown in Table 5.

[0059] Next, the relationship between the ΔDI change rate and the void filling rate of the powder coal part was plotted as shown in Figure 5. From Figure 5, it can be seen that the lower the void filling rate of the powder coal part, the larger the ΔDI change rate. The plot in Figure 5 was linearly approximated to obtain the following relational expression (I). [ΔDI change rate ((cm 3 / g) -1 )]=-46.5×[void filling degree of powder coal part]+69.2 (I)

[0060] (Conversion of briquette blending ratio) Among levels 1 to 27, the blending ratio of briquettes in levels 1 to 12 and 20 to 27 is 25% by mass, and the blending ratio of briquettes in levels 13 to 17 is 12.5% ​​by mass. Therefore, in order to evaluate all levels on an equal footing, the relationship between the blending ratio of briquettes and ΔDI when the powder coal and briquettes are the same type was confirmed separately. Specifically, for levels 1a and 8a, which are the same as levels 1 and 8, respectively, except that the blending ratio of briquettes was 35.0% by mass, drum tests were performed in the same manner as levels 1 and 8, and the change in ΔDI was calculated. The results are shown in Tables 4 and 5.

[0061] The ΔDI change rate calculated from levels 1a and 8a was 35.6, while the ΔDI change rate calculated from levels 1 and 8 was 25.0. The relationship between the briquette blending ratio (x-axis) and the ΔDI change rate (y-axis) was plotted and linearly approximated, and the following relationship was obtained. [ΔDI change rate ((cm 3 / g) -1 )]=1.01×molded coal blending ratio (mass%) Based on this result, for levels 13 to 17, the converted value according to the following formula was used as ΔDI (corrected value). [ΔDI after conversion (corrected value)] = 1.01 × [ΔDI before conversion (corrected value)] × 25 (mass%) / 12.5 (mass%)

[0062] (Calculation of estimated coke strength) Next, among levels 1 to 27, the coal blends with SV of the briquettes below the lower limit of SV of the briquettes (levels 7, 8, 11, 12, 16, 17, and 24 to 27) were considered as coal blends to be used in coke production, and the DI of each coal blend was calculated. 150 6 was estimated for each level. The procedure is as follows for each level. First, the degree of void filling in the powder coal part of each coal blend was substituted for the term [void filling degree in the powder coal part] in the above relational formula (I) to calculate the degree of change in ΔDI. Next, the difference between the lower limit of the briquette part SV calculated above for the level group in which each coal blend and the powder coal part are of the same type and the actual measured value of the briquette part SV of each coal blend was multiplied by the degree of change in ΔDI calculated in the above section "Calculation of the degree of change in ΔDI". Next, the weighted average DI of each coal blend was calculated. 150 The DI for each coal blend is calculated by subtracting the above ΔDI from 6. 150 We obtained an estimate of 6. The results are shown in Table 5.

[0063] From the results shown in Table 5, in a coal blend in which the SV of the briquette is below the lower limit of the SV of the briquette, it is possible to evaluate the ΔDI taking into account the degree of void filling in the powder coal part, which is effective in reducing the DI of the entire coal blend. 150 It turns out that this is useful for estimating 6 with good accuracy.

[0064] In the above relational formula (I), the ΔDI change rate is 0 (cm 3 / g)-1 The void filling ratio of the powder coal part when the briquette coal part SV is 1.10 cm was 1.49. Therefore, when the void filling ratio of the powder coal part is this value or more, the coke strength can be estimated without considering the void effect ΔDI. For example, in levels 18 and 19 (powder coal part is pulverized coal under blending condition 4, moisture content 4 mass%, void filling ratio 1.51), the void filling ratio of the powder coal part exceeds the above 1.49. As a result, when the briquette coal part SV is 1.10 cm, the void filling ratio of the powder coal part is 1.10 cm. 3 / g and the SV of the molded coal is 0.97 cm 3 / g, and the actual DI for blended coal 150 6 and weighted average DI 150 Thus, in the case of a coal blend using powder coal with a void filling degree equal to or greater than the void filling degree value when the ΔDI change rate becomes 0, the DI of the powder coal part was almost the same without considering the effect of the void on the coke strength. 150 6 and Molded Charcoal DI 150 The weighted average of these two values ​​can be used as the estimated coke strength.

[0065] [Table 1]

[0066] [Table 2]

[0067] [Table 3]

[0068] [Table 4]

[0069] [Table 5]

Claims

1. A method for estimating strength of coke produced by carbonizing blended coal containing molded coal and powdered coal, comprising: A plurality of test coal blends are prepared, each of which is a combination of a plurality of test powder coals having different void filling degrees (SV x BD), which is the product of expansion specific volume SV and bulk density BD, and a plurality of test briquettes having different expansion specific volumes (SV); Actual measured DI of each test powder coal and each test briquette coal 150 6 Based on the drum index, the weighted average DI of each test coal blend was calculated. 150 6 (a1) is calculated, Actual measured DI of each test coal blend 150 6 Based on (b1), the DI of the blended coal was not affected even if the SV of the briquettes was changed. 150 6 A lower limit value (c1) of the briquette part SV range in which the briquette part SV is constant is obtained, Among the multiple types of test coal blends, a weighted average DI of a low SV test coal blend including a test coal blend having an SV less than the SV lower limit (c1) of the briquette portion is calculated. 150 6 (a1) and the measured DI 150 6 Calculate ΔDI, which is the difference from (b1), Based on the relationship between the briquette coal part SV of the low SV test coal blend and the ΔDI, a ΔDI change rate (d1) which is a change in ΔDI per unit change in the briquette coal part SV is calculated; Obtain a relationship between the ΔDI change rate (d1) and the void filling rate of the test powder coal, In a coal blend containing powdered coal to be used and briquettes to be used, the measured DI of each of the powdered coal and the briquettes 150 6 Weighted average DI of blended coal based on 150 6 (a2) is calculated, (i) When the SV of the briquettes to be used is equal to or greater than the lower limit SV of the briquettes (c1), the weighted average DI of the briquettes is 150 6 (a2) is the target coke strength estimate, (ii) When the SV of the briquettes to be used is less than the lower limit SV of the briquettes (c1), the difference between the lower limit SV of the briquettes (c1) and the SV of the briquettes is multiplied by the ΔDI change rate (d1) to calculate ΔDI, and the weighted average DI of the briquettes to be used is calculated. 150 6 The value obtained by subtracting the ΔDI from (a2) is set as the target coke strength estimated value. Method for estimating coke strength.

2. A method for producing coke using a blended coal containing molded coal and powdered coal, A plurality of test coal blends are prepared, each of which is a combination of a plurality of test powder coals having different void filling degrees (SV x BD), which is the product of expansion specific volume SV and bulk density BD, and a plurality of test briquettes having different expansion specific volumes (SV); Actual measured DI of each test powder coal and each test briquette coal 150 6 Based on the drum index, the weighted average DI of each test coal blend was calculated. 150 6 (a1) is calculated, Actual measured DI of each test coal blend 150 6 Based on (b1), the DI of the blended coal was not affected even if the SV of the briquettes was changed. 150 6 A lower limit value (c1) of the briquette part SV range in which the briquette part SV is constant is obtained, Among the multiple types of test coal blends, a weighted average DI of a low SV test coal blend including a test coal blend having an SV less than the SV lower limit (c1) of the briquette portion is calculated. 150 6 (a1) and the measured DI 150 6 Calculate ΔDI, which is the difference from (b1), Based on the relationship between the briquette coal part SV of the low SV test coal blend and the ΔDI, a ΔDI change rate (d1) which is a change in ΔDI per unit change in the briquette coal part SV is calculated; A relationship between the ΔDI change rate (d1) and the void filling rate of the test powder coal is obtained, and a void filling rate lower limit value (e1) at which the ΔDI change rate (d1) is equal to or less than a preset value (α) is obtained based on the relationship. (i) Using briquettes having an SV equal to or greater than the lower limit SV (c1) of the briquettes, and / or (ii) Use briquettes having an SV less than the SV lower limit (c1) of the briquettes, and use pulverized coal having a void filling degree equal to or greater than the void filling degree lower limit (e1); Coke manufacturing method.

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