Method for estimating coke strength and method for producing coke

Abstract

To provide a method for estimating coke strength capable of estimating coke strength after volume change without using a crushing method.SOLUTION: A method for estimating coke strength includes a coke production step of producing coke while changing a molded coal volume for each of three coal blends having different void filling degrees of fine coal and molded coal, an influence degree calculation step of defining a slope of an approximate straight line representing a relationship between the molded coal volume and coke strength as an influence degree of the molded coal volume on the coke strength, and a constant calculation step of calculating constants a to c in formula (1) based on the calculation results. Coke using a coal blend A containing fine coal and molded coal as a raw material is defined as coke A, and coke using a coal blend B, in which the volume of molded coal in the coal blend A is changed from X1 to X2, as a raw material is defined as coke B. The coke strength of the coke B is estimated based on the coke strength of the coke A and formula (1). Formula (1) is "influence degree=void filling degree of fine coal×a+void filling degree of molded coal×b+c".SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In the past, in the production of blast furnace coke, various methods have been studied to address the depletion of high-quality heavily caking coal resources by increasing the blending ratio of inferior coal (such as non- or slightly caking coal) in a coal blend composed of molded coal and powder coal while maintaining good coke strength. Coal pretreatment processes can be useful for obtaining the desired coke strength using a coal blend containing inferior coal.

[0003] Briquetting, a coal pretreatment process, improves coke strength by increasing the bulk density of the coal charge through the use of denser briquettes. The high density of briquettes also allows for the inclusion of lower-quality coals in the briquettes without reducing coke strength. Briquetting can also be combined with other coal pretreatment processes, such as drying and grinding.

[0004] In the briquetting method, it is known that by changing the volume of briquetting coal under the condition of a constant blending ratio of briquetting coal, the bulk density of the blended coal, which is a mixture of briquetting coal and powder coal, changes, and therefore the coke strength changes.

[0005] Patent Document 1 describes a coke manufacturing method in which the particle size of the blended coal is adjusted depending on the void filling degree of the coal, focusing on the fact that the relationship between the particle size of the coal briquette and the coke strength changes depending on the void filling degree of the coal briquette. On the other hand, crushed coal briquette is often used as the coal briquette in the tests, and the particle size of the crushed coal is examined within a smaller range than that of ordinary coal briquette.

[0006] Furthermore, the relationship between the particle size of the briquette and the coke strength is summarized using an index called the void filling ratio of the briquette, which is calculated as the product of the expansion specific volume (SV) of the briquette and the bulk density of the coal blend. While the void filling ratio of the briquette is an index representing the degree of adhesion between coal particles in the briquette during thermoplastic melting, Patent Document 1 uses the bulk density of the coal blend rather than the density of the briquette to calculate the void filling ratio of the briquette, and treats briquette and powdered coal together. Since the coke strength of the briquette blend is calculated as a weighted average of the coke strength of the briquette and the powdered coal, it is not desirable to treat briquette and powdered coal together. Furthermore, the relationship between the particle size of the briquette and the coke strength is summarized assuming the bulk density of the coal blend is constant. However, the summary does not take into account the fact that the bulk density changes depending on the volume of the briquette. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-120898 [Patent Document 2] Japanese Patent Application Publication No. 174951 / 1983 [Non-patent literature]

[0008] [Non-Patent Document 1] Coke Circular;(11),13-5(1981) Summary of the Invention [Problem to be solved by the invention]

[0009] It is known that changing the volume of briquettes changes the bulk density of the coal blend and the coke strength. If we can clarify the effect of briquette volume on coke strength, it will be possible to narrow down the desired briquette volume from the viewpoint of coke strength.

[0010] One method for adjusting the particle size of briquette coal is the crushing method, and although there is prior art that has clarified the relationship between the volume of briquette coal and coke strength when using crushed briquette coal, the range of investigation into the volume of briquette coal is narrow.In addition, the crushing method has issues such as the need for additional crushers and screening equipment, and the difficulty of adjusting the particle size.

[0011] An object of the present invention is to estimate the coke strength after changing the volume of briquettes without using a crushing method. [Means for solving the problem]

[0012] Molded coal is characterized by its larger volume compared to powder coal and the use of binders such as coal tar during molded coal production. Because of its larger volume, gases generated during thermoplastic melting are more easily trapped within the molded coal, resulting in a higher void filling rate within the molded coal. This in turn compacts the surrounding powder coal, increasing the void filling rate of the powder coal and improving coke strength. Therefore, the void filling rate of the molded coal is thought to affect the change in coke strength when the molded coal volume is changed. Furthermore, the binder used during production has the effect of improving expansion, and this effect affects the molded coal and the surrounding powder coal. When the surrounding powder coal has low expansion, the expansion improvement effect of the binder is expected to improve the void filling rate, thereby improving coke strength. From this perspective, the void filling rate of the powder coal is also thought to affect the change in coke strength when the molded coal volume is changed.

[0013] The present inventors have discovered the following method for estimating coke strength when the volume of molded coal is changed, which does not rely on the crushing method. The method for estimating coke strength of the present invention includes: (1) a coke production step of producing coke for each of three coal blends, each of which differs in at least one of the void filling degree of the powder coal and the void filling degree of the briquettes, while varying the volume of the briquettes within a predetermined range; an influence degree calculation step of obtaining an approximation line representing the relationship between the volume of the briquettes and the coke strength for each coal blend, and calculating the slope of the approximation line as the influence degree of the briquettes volume on the coke strength; and a constant calculation step of calculating constants a to c in the following equation (1) based on the calculation result of the influence degree calculation step, wherein coke made from a coal blend A containing powder coal and briquettes is defined as coke A, and coke made from a coal blend B obtained by changing the volume of the briquettes of the coal blend A from X1 to X2 is defined as coke B, and the coke strength of the coke A is obtained by measuring or estimating the coke strength of the coke A in advance. 3 In the following cases, the degree of influence of the volume of the briquettes on the coke strength is calculated by substituting the void filling degree of the powder coal of the coal blend B and the void filling degree of the briquettes into formula (1), and then multiplying the calculated degree of influence by the difference between the volumes X1 and X2 (where the difference is X2-X1) to calculate a multiplication value, and adding this multiplication value to the coke strength obtained in the base information obtaining step to estimate the coke strength of the coke B. When the volume of the briquettes of the coal blend B is 50 cm 3 In the case of over 50cm2, the volume X2 is 3 and a coke strength estimating step of estimating the coke strength when the coke B is at a temperature of 1000° C. as the coke strength of the coke B.

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[0014] (2) The method for estimating coke strength according to (1) above, characterized in that the void filling degree of powdered coal is the product of the expansion specific volume of powdered coal and the bulk density of powdered coal, and the void filling degree of molded coal is the product of the expansion specific volume of molded coal and the apparent density of molded coal.

[0015] (3) The predetermined range is 4 cm 3More than 50cm 3 The method for estimating coke strength according to (1) or (2) above, characterized in that:

[0016] (4) A method for producing coke B using the method for estimating coke strength according to (1) or (2) above, comprising a step of determining a volume X2 of briquettes and a blending ratio of briquettes so that a target coke strength is satisfied and the bulk density of the coal blend B in producing the coke is not lower than the bulk density of the coal blend A by a predetermined amount or more, and confirming in the determining step that the target coke strength is satisfied by the coke strength estimating step. [Effects of the Invention]

[0017] According to the present invention, the coke strength when the volume of molded coal is changed can be estimated without using a crushing method. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing the relationship between the volume of molded coal and corrected coke strength (DI150 6) (Levels 2 to 5). [Figure 2] FIG. 1 is a diagram showing the relationship between the volume of molded coal and corrected coke strength (DI150 6) (Levels 7 to 9). [Figure 3] FIG. 1 is a diagram showing the relationship between the volume of molded coal and the measured value of coke strength (DI150 6) (Levels 11 to 13). DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] The method for estimating coke strength according to the present invention includes a "coke production step," an "influence degree calculation step," a "constant calculation step," a "base information acquisition step," and a "coke strength estimation step." Each step will be described in detail below.

[0021] (Coke making step) Three types of coal blends containing powder coal and briquettes are prepared, and coke is produced for each blend by changing the volume of the briquettes. The reason for preparing three types of coal blends is that there are three constants (a to c) to be calculated in the "constant calculation step." The plurality of coal blends differ from one another in at least one of the void filling degree (-) of the fine coal and the void filling degree (-) of the briquetted coal. The void filling rate of powder coal (-) is calculated by the expansion specific volume SV (cm 3 / g) × bulk density of powdered coal (g / cm 3 The void filling degree (-) of the briquette can be calculated by the expansion specific volume SV (cm 3 / g) × apparent density of molded coal (g / cm 3 ) can be calculated by the expansion specific volume SV (cm 3 / g) can be measured by, for example, a carbonization test using a dilatometer. 3 The apparent density (g / cm 3 ) of the briquettes can be measured by, for example, a bulk density measurement test (see, for example, Non-Patent Document 1). 3 ) can be measured, for example, by an apparent specific gravity measuring device.

[0022] The volume of the briquettes is changed within a specified range. 3 More than 50cm 3 The following ranges (hereinafter also referred to as predetermined volume ranges) are recommended, the reasons for which will be described later. Furthermore, since it is necessary to obtain an approximate straight line that defines the relationship between the molded coal volume and the coke strength in the "influence degree calculation step," it is desirable to change the volume at least three times in order to improve the accuracy of the approximate straight line. For example, when coal blends O, P, and Q are prepared, coke is produced while changing the volume of the briquettes within a predetermined volume range for each of the coal blends O, P, and Q. In the following description, the cokes obtained by carbonizing the coal blends O, P, and Q may be referred to as cokes O, P, and Q, respectively.

[0023] (Influence calculation step) An approximate line representing the relationship between the volume of the briquettes and the coke strength is determined for each coal blend, and the slope of the approximate line is calculated as the degree of influence of the volume of the briquettes on the coke strength. For example, if coal blends O, P, and Q are prepared in the "coke production step," coke strengths can be obtained for each of the cokes O, P, and Q by changing the volume of the briquettes. This allows three approximate lines representing the relationship between coke strength and the volume of the briquettes to be obtained. The coke strength may be an actual measurement obtained by a drum test or the like, or an estimated value calculated from a weighted average of the strength of the powder coal portion and the strength of the briquettes. The estimated value can be calculated, for example, based on Patent Document 2. The approximate lines can be calculated, for example, by the least squares method. As will be explained in the examples below, when the volume of the briquettes is 50 cm 3 In this embodiment, the approximate line is created by limiting the volume of the molded coal to a "predetermined volume range," so that a highly accurate approximate line can be obtained.

[0024] (Constant calculation step) Based on the calculation results of the "influence degree calculation step", the constants a to c in the following formula (1) are calculated.

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[0025] Here, a coal blend containing powder coal and briquette coal (where the volume of the briquette coal is X1) is defined as coal blend A, a coal blend containing powder coal and briquette coal (where the volume of the briquette coal is X2) is defined as coal blend B, and the cokes produced by carbonizing coal blend A and coal blend B are defined as coke A and coke B, respectively. Coal blends A and B have the same blending conditions for the powder coal and the same blending conditions for the briquette coal. In this embodiment, the coke strength of coke B is estimated by the following "base information acquisition step" and "coke strength estimation step" without using a crushing method.

[0026] (Base information acquisition step) The coke strength of coke A is determined. The coke strength may be an actual measured value obtained by a drum test or the like, or may be an estimated value estimated based on the above-mentioned method. Here, the timing of performing the "base information acquisition step" is not particularly limited. It may be performed before or after the above-mentioned "coke production step," "influence degree calculation step," and "constant calculation step."

[0027] (Coke strength estimation step) The coke strength estimation step varies depending on the volume of briquettes contained in coal blend B. (I) The volume of the coal briquettes contained in coal blend B is 50 cm 3 In the following cases: The void filling degree (-) of the fine coal of coal blend B and the void filling degree (-) of the briquettes are substituted into equation (1) to determine the degree of influence of the volume of the briquettes on the coke strength, and the determined degree of influence is multiplied by the difference between the volumes X1 and X2 (where the difference is X2 - X1) to determine a multiplication value. The method for determining the void filling degree (-) of the fine coal and the briquettes has been described above, so the description will not be repeated. After the multiplication value is calculated, this multiplication value is added to the coke strength of coke A obtained in the "base information acquisition step", and the result is estimated as the coke strength of coke B. (II) The volume of the coal briquettes contained in coal blend B is 50 cm 3 In the case of super Volume x2 = 50cm 3 The coke strength calculated by the method shown in (I) is estimated as the coke strength of coke B. As will be explained in the examples below, when the volume of the briquettes is 50 cm 3 If the temperature exceeds this range, the coke strength will hardly change.

[0028] According to this embodiment, by using the void filling ratio (-) of the powder coal and the briquette, the coke strength after changing the volume of the briquette can be estimated without using a crushing method, and therefore the volume of the briquette required from the viewpoint of coke strength can be easily determined.

[0029] By utilizing the above-described method for estimating coke strength, it is possible to produce coke B that satisfies the desired production volume and target coke strength. Specifically, in the step of determining the briquette volume X2 and the blending ratio of the briquette coals so that the target coke strength is satisfied and the bulk density of the coal blend B is not lower than the bulk density of the coal blend A by more than a predetermined amount during coke production, if the briquette volume X2 that satisfies the target coke strength is determined using the above-described method for estimating coke strength, it is possible to produce coke B that satisfies the desired production volume and target coke strength. A lower bulk density leads to a lower coke production amount, so the "predetermined amount" may be determined appropriately based on the desired production amount.

[0030] Example 1 The present invention will be specifically described below with reference to examples. The influence of the volume of briquette coal on the coke strength was evaluated by carbonization tests using a test coke oven for blended coals containing powder coal and briquette coal. Table 1 shows the volatile matter VM (mass%) and total swelling coefficient TD (%) of each of the coals A to H used. The volatile matter VM (mass%) was calculated on a dry basis (the same applies to the volatile matter ΣVM (mass%) of powder coal and briquette coal, which will be described later). [Table 1]

[0031] Table 2 shows the blending conditions 1 to 3 of the powder coal and the properties of the powder coal, such as the volatile matter ΣVM (mass%), total expansion coefficient ΣTD (%) and expansion specific volume SV (cm 3 / g) are shown. Powder coal blending condition 1 had a moisture content of 4 or 10 mass%, powder coal blending condition 2 had a moisture content of 4 mass%, and powder coal blending condition 3 had a moisture content of 10 mass%. In all cases, the crushed particle size was 85 mass% of the 3 mm undersieve. The bulk density (g / cm 3 ) was measured using a bulk density measuring tester (see Non-Patent Document 1) in which the drop height, hopper shape, and slide valve area were improved from ASTM D 291-86. The bulk density (g / cm 3 ) is not shown in Table 2, but as will be described later, it is the charging density (g / cm 3 ) when the blending ratio of briquettes in Table 4 is 0 mass%. 3 ) minus 0.05. As will be described later, in the test furnace, the bulk density was set to 0.05 (g / cm 3 By increasing the charging density, coke equivalent to that of a real furnace can be obtained. [Table 2]

[0032] Table 3 shows the blending conditions 1 to 3 of the briquettes and the properties of the briquettes, such as the volatile content ΣVM (mass%), total expansion coefficient ΣTD (%), and expansion specific volume SV (cm 3 / g) and the apparent density (g / cm 3 The briquettes were produced by briquetting powder coal with a crushed particle size of 3 mm and an undersize fraction of 90% by mass in a briquetting machine according to briquetting conditions 1 to 3. A tar-based binder was used as the liquid binder, and asphalt pitch (ASP) was used as the solid binder. The volumes were 4, 8, 18, 38, and 130 cm3. 3 Briquette coals with particle sizes of 20, 25, 33, 42, and 63 mm were produced. The apparent density of the briquette coals (g / cm 3 ) was measured using an apparent specific gravity measuring device. [Table 3]

[0033] The expansion specific volume SV (cm) of powder coal and briquette coal shown in Tables 2 and 3 3The carbonization test was carried out using a dilatometer. The powder coal and briquette coals of each powder coal blending condition and each briquette blending condition were crushed and adjusted to a particle size of 100% by mass of 3 mm sieve. Then, they were placed in a reaction tube and a carbonization test was carried out under heating conditions with a heating rate of 3 (°C / min). The height of the sample in the reaction tube was 60 mm. The expansion specific volume SV (cm 3 / g) measurement, the bulk density is 0.85 (g / cm 3 ) and the expansion specific volume of the briquette SV (cm 3 / g) measurement, the bulk density was 1.10 (g / cm 3 ) was decided.

[0034] Expansion specific volume of briquette SV (cm 3 / g) is the apparent density of the briquette (g / cm 3 The void filling degree (-) of the briquettes was calculated by multiplying the pore filling degree (-) of the briquettes (see Table 5 below). 3 / g) is the bulk density of the powdered coal (g / cm 3 ) to obtain the void filling degree (-) of the powder coal.

[0035] Powder coal and briquette were blended under the conditions of levels 1 to 13 shown in Table 4, and coke was produced by carbonization in a test coke oven. Each coke was subjected to a drum test. Levels 2 to 4 correspond to coal blend O, with the same powder coal blending conditions and briquette blending conditions but different briquette volumes. Levels 7 to 9 correspond to coal blend P, with the same powder coal blending conditions and briquette blending conditions but different briquette volumes. Levels 11 to 13 correspond to coal blend Q, with the same powder coal blending conditions and briquette blending conditions but different briquette volumes. The briquette blending ratios of coal blends O, P, and Q were set to different values. [Table 4]

[0036] The test conditions for the drum test were a rotation speed of 150 rpm and N = 3. The bulk density measured using the above-mentioned bulk density measuring tester (see Non-Patent Document 1) was adjusted to 0.05 (dry g / cm 3) and correct it to obtain the charge density (g / cm 3 This correction was made to take into account the low height of the test furnace and to obtain the same coke strength between the test furnace and the actual furnace.

[0037] Since the blending ratios of coal briquette in levels 2 to 5, 7 to 9, and 11 to 13 are different from each other, it is assumed that a proportional relationship exists between the blending ratio of coal briquette and coke strength. The coke strength (DI) at a blending ratio of coal briquette of 30 mass% is 150 6) coke strength (DI) of levels 2 to 5 and levels 7 to 9 150 For example, the coke strength (DI) of level 1 (briquette blending ratio: 0 mass%) and level 2 (briquette blending ratio: 50 mass%) was corrected. 150 6), the coke strength (DI) was calculated based on the results of the experiment. 150 6) and determine the change in coke strength (DI 150 6) by adding "the change in the amount x 30" to obtain the coke strength (DI 150 6) was calculated. 150 6), along with the corrected coke strength (DI 150 6) are shown in Table 5. [Table 5]

[0038] Briquette volume and corrected coke strength (DI) for levels 2-5 and levels 7-9 150 The relationship between the volume of briquettes and coke strength (DI) for levels 11 to 13 is shown in Figures 1 and 2, respectively. 150 6) is shown in Figure 3.

[0039] Referring to Figures 1 and 2, as the volume of the briquettes increases, the corrected coke strength (DI 150 6) decreased. Referring to Figure 3, as the volume of the briquettes increased, the coke strength (DI 150The measured values ​​of 6) increased. As mentioned above, the particle size of all the briquettes was 15 mm or more, and the results obtained differ from those in Patent Document 1, which states that the coke strength becomes constant when the particle size is 15 mm or more. This is thought to be due to the difference in the investigated range of particle size (volume) of the briquettes.

[0040] In Figure 1, the volume of the briquettes is 38 cm 3 and 130cm 3 The corrected coke strength (DI 150 6), we assumed that the coke strength would be constant when the volume of the briquette exceeded a certain level. 3 The slope of the approximation line at the briquette volume was calculated as the effect of the briquette volume on the coke strength, and the results are shown in Table 5.

[0041] As shown in Table 5, levels 2 to 5 (corresponding to coal blend O), levels 7 to 9 (corresponding to coal blend P), and levels 11 to 13 (corresponding to coal blend Q) differ in at least one of the void filling degree of the powder coal (-) and the void filling degree of the briquette coal (-). Therefore, the coke strength (DI 150 It is thought that the influence of the volume of briquette on the coke strength (DI 150 We thought that the influence of the volume of briquettes on 6) could be calculated using the above formula (1). Formula (1) is shown again below.

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[0042] By substituting the void filling rate (-) of the powder coal and the void filling rate (-) of the molded coal in each of the coal blends O, P, and Q into equation (1), a simultaneous equation consisting of three linear equations is obtained. By solving these simultaneous equations, the following values ​​were calculated: a = 0.118, b = 0.086, and c = -0.308.

[0043] In summary, the influence of the molded coal volume on coke strength can be calculated from the void filling ratio (-) of the powder coal and the void filling ratio (-) of the molded coal, and it is thought that the change in coke strength when the molded coal volume is changed can be estimated from the calculated influence of the molded coal volume on coke strength. Note that the coke strength before changing the molded coal volume can be an actual measured value, or if it can be estimated by a method other than that described in this example, that estimated value can be used.

[0044] The volume of the charcoal molded products is 4 to 38 cm. 3 On the approximate line at 130cm, the volume of the briquettes is 3 The volume of the briquettes that corresponds to the coke strength of 3 Therefore, the volume of the charcoal molded product is about 50 cm 3 It was thought that when the briquette volume X2 exceeds 50 cm (46 mm in particle size), the coke strength does not change significantly regardless of the briquette volume. Based on this idea, in the "coke strength estimation step," the briquette volume X2 is set to 50 cm 3 The coke strength of coke exceeding 50 cm2 is 3 It was thought that the coke strength would be the same as that at

[0045] Example 2 It was verified whether coke strength could be estimated based on formula (1) calculated in Example 1. As in Example 1, powder coal and briquettes were blended under the conditions of levels 14 to 18 shown in Table 6, and cokes were produced by carbonization in a test coke oven. Each coke was then subjected to a drum test to measure the coke strength (DI 150 As in Example 1, the void filling degrees (-) of the powder coal and the briquette coal were determined, and these void filling degrees (-) were substituted into the formula (1) calculated in Example 1 to determine the degree of influence of the volume of the briquette coal on the coke strength. Then, the coke strength (DI 150 6) was estimated. [Table 6]

[0046] Coke strength (DI150 6) The discrepancy between the measured value and the estimated value is very small, and it was found that the coke strength when the volume of the briquettes is changed can be accurately estimated by the method for estimating coke strength according to the present invention.

Claims

1. a coke-making step of producing coke from three coal blends, each of which has a different void filling degree of the powder coal and a different void filling degree of the briquettes, while varying the volume of the briquettes within a predetermined range; an influence degree calculation step of obtaining an approximation line representing the relationship between the volume of the briquettes and the coke strength for each of the coal blends, and calculating the slope of the approximation line as the influence degree of the volume of the briquettes on the coke strength; a constant calculation step of calculating constants a to c in the following formula (1) based on the calculation result of the influence degree calculation step; and When coke made from a coal blend A containing powder coal and briquettes is defined as coke A, and coke made from a coal blend B obtained by changing the volume of the briquettes of the coal blend A from X1 to X2 is defined as coke B, a base information acquiring step of previously determining the coke strength of the coke A by actual measurement or estimation; The volume of the coal blend B is 50 cm ３ In the following cases, the degree of influence of the volume of the briquettes on the coke strength is calculated by substituting the void filling degree of the powder coal of the coal blend B and the void filling degree of the briquettes into formula (1), and then the calculated degree of influence is multiplied by the difference between the volumes X1 and X2 (where the difference is X2-X1) to calculate a multiplication value, and this multiplication value is added to the coke strength obtained in the base information obtaining step to estimate the coke strength of the coke B. When the volume of the briquettes of the coal blend B is 50 cm ３ If the volume X2 is greater than 50 cm ３ a coke strength estimating step of estimating the coke strength when A method for estimating coke strength, comprising: [Equation 1]

2. The void filling degree of the powder coal is the multiplication value of the expansion specific volume of the powder coal and the bulk density of the powder coal; The void filling degree of the briquette is the product of the expansion specific volume of the briquette and the apparent density of the briquette. The method for estimating coke strength according to claim 1 .

3. The predetermined range is 4 cm ３ More than 50cm ３ 3. The method for estimating coke strength according to claim 1, wherein:

4. A method for producing coke B using the method for estimating coke strength according to claim 1 or 2, a determining step of determining a volume X2 of the briquettes and a blending ratio of the briquettes so that a target coke strength is satisfied and the bulk density of the coal blend B when producing coke is not lower than the bulk density of the coal blend A by a predetermined amount or more; In the determination step, it is confirmed by the coke strength estimation step that the target coke strength is satisfied. A method for producing coke characterized by:

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