Molded charcoal manufacturing method

Abstract

To provide a method for producing molded coal, which can produce molded coal with sufficient strength using a limited amount of binder. [Solution] The manufacturing method includes a preparation step (S21), a mixing step (S22), a briquetting step (S23), a derivation step (S11), a setting step (S12), and a calculation step (S13). In the derivation step (S11), a positive correlation between the size of each briquette and the mass ratio of binder to powder coal (RT ratio) is derived for each strength of the briquette. In the setting step (S12), a specific strength of the briquette required in the briquetting step (S23) and a specific mass ratio of the RT ratio required in the mixing step (S22) are set. In the calculation step (S13), a specific size of each briquette corresponding to the specific mass ratio is calculated based on the positive correlation corresponding to the specific strength. In the mixing step (S22), a binder is added to the powder coal in a specific mass ratio. In the briquetting step (S23), each briquette is briquetteed to a specific size or smaller.

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing molded charcoal. [Background technology]

[0002] In the coke production process, molded coal is used as part of the coke raw material to improve the strength of the coke produced. The raw material for molded coal is a mixture of powdered coal and a binder. This mixture is molded using a mold to produce a large number of molded coals. Therefore, molded coal is nothing more than a compacted powder body.

[0003] Briquettes are transported along a conveyor route consisting of many connected conveyor belts and are ultimately charged into a coke oven. Therefore, the briquettes are subjected to impacts when changing conveyor belts or when being charged into a coke oven (carbonization chamber). If the strength of the briquettes is low, they will collapse due to the impact. If collapsed briquettes are used as coke raw materials, the strength of the resulting coke may not be sufficiently improved.

[0004] Japanese Patent Laid-Open Publication No. 2018-44045 (Patent Document 1) describes a technique for preventing collapse of molded coal in a transport path. The technique described in Patent Document 1 is a coal pre-treatment method including a molded coal preparation step and a transport step. In the molded coal preparation step, molded coal is prepared using a heated binder, and in the subsequent transport step, the internal temperature of the molded coal in the transport path is adjusted to 50 to 60°C. Patent Document 1 describes that based on the finding that the drop strength of molded coal increases when the internal temperature of molded coal is 50 to 60°C, it is possible to prevent collapse of molded coal in the transport path by adjusting the internal temperature of the molded coal in the transport path to within the range of 50 to 60°C.

[0005] Japanese Patent Laid-Open Publication No. 2019-127523 (Patent Document 2) describes a technique for preventing the collapse of low-strength molded coal when it is charged into a coke oven. The technique described in Patent Document 2 is a molded coal charging method that uses a plurality of molded coals with different crushing strengths. In this charging method, high-strength molded coals are charged through a coal charging hole, and then low-strength molded coals are charged through another coal charging hole. Patent Document 2 describes that the low-strength molded coals fall onto the high-strength molded coals, so the falling height is effectively reduced, and the falling impact on the low-strength molded coals can be mitigated. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-44045 [Patent Document 2] Japanese Patent Application Publication No. 2019-127523 Summary of the Invention [Problem to be solved by the invention]

[0007] The technologies of Patent Documents 1 and 2 suppress the collapse of briquettes due to the impact of dropping them by devising methods for transporting briquettes and charging them into coke ovens. However, the technology of Patent Document 1 requires the installation of a thermal insulation cover on the transport path and a system for managing the temperature of the transport path, while the technology of Patent Document 2 requires the installation of a system for sorting low-strength briquettes from high-strength briquettes in a coal-charging car that charges the briquettes into the coke oven. Therefore, both technologies require investments unrelated to the actual operation of the coke oven. In order to suppress the collapse of briquettes without significantly changing the transport and charging methods already in use, it is necessary to produce high-strength briquettes.

[0008] Generally, in the manufacturing method of molded coal, increasing the mass ratio of binder to powdered coal improves the strength of the molded coal and suppresses the collapse of the molded coal due to the impact of dropping. This is because the binder strengthens the adhesion of the powdered coal to each other. However, since binder is expensive and limited, the amount of binder used in the manufacturing of molded coal is limited.

[0009] An object of the present disclosure is to provide a method for producing molded coal that can produce molded coal with sufficient strength using a limited amount of binder. [Means for solving the problem]

[0010] A manufacturing method according to the present disclosure is a method for manufacturing molded coal, which is a raw material for coke. The manufacturing method includes a preparing step, a mixing step, a molding step, a discharging step, a setting step, and a calculating step. In the preparing step, powdered coal is prepared. In the mixing step, a binder is added to the powdered coal and mixed to produce a mixture of the powdered coal and the binder. In the molding step, the mixture is molded into a number of molded coals. In the discharging step, a positive correlation between the size of each molded coal and the mass ratio of the binder added to the powdered coal to the powdered coal is derived in advance for each strength of the molded coal. In the setting step, a specific strength of the molded coal required in the molding step and a specific mass ratio of the binder required in the mixing step are set in advance. In the calculating step, a specific size of each molded coal corresponding to a specific mass ratio is calculated in advance based on the positive correlation corresponding to the specific strength. In the mixing step, a binder is added to the powdered coal in a specific mass ratio, and in the briquetting step, each briquette is briquetteed to a specific size or less. [Effects of the Invention]

[0011] According to the present disclosure, molded coal with sufficient strength can be produced using a limited amount of binder. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a flowchart illustrating a method for producing molded coal according to an embodiment. [Figure 2] FIG. 2 is an example of a graph showing the relationship between the size of briquettes and the mass ratio of binder to powdered coal (RT ratio) for each trommel strength. [Figure 3] FIG. 3 is a graph showing the relationship between the binder ratio and the trommel strength for each volume of each type of molded coal. [Figure 4] FIG. 4 is a graph showing the relationship between the volume of each molded coal and the binder ratio for each trommel strength. DETAILED DESCRIPTION OF THE INVENTION

[0013] The collapse of briquettes occurs due to the impact of dropping. To prevent the collapse of briquettes due to the impact of dropping, it is necessary to ensure the strength of the briquettes. The strength of briquettes is usually evaluated by trommel strength. Trommel strength is an index of the strength of briquettes, and is expressed as the mass ratio of briquettes that maintain a certain size or larger relative to the total briquettes when the briquettes to be evaluated are repeatedly dropped and impacted. The impact of dropping briquettes is calculated using the mass of each briquette, the falling distance, and the potential energy calculated from the gravitational acceleration. Therefore, it can be said that the mass of each briquette affects the strength of the briquettes. The mass of each briquette corresponds to the size of the briquettes.

[0014] As described above, it is known that the mass ratio of the binder to the powdered coal affects the strength of the molded coal. In this specification, the mass ratio of the binder to the powdered coal is sometimes referred to as the "RT ratio."

[0015] Therefore, the inventors of the present invention have conducted extensive research focusing on two factors that affect the strength of briquettes: the size of the briquettes and the mass ratio of binder to powdered coal (RT ratio). As a result, they have found that for briquettes of the same strength, there is a positive correlation between the size of the briquettes and the RT ratio. Furthermore, for briquettes of the same size, the strength of the briquettes generally increases as the RT ratio increases. Taking these factors into consideration, it has become clear that for briquettes of the same RT ratio, the strength of the briquettes increases as the briquettes' size decreases.

[0016] The method for producing molded carbon according to an embodiment of the present disclosure has been completed based on the above findings.

[0017] A manufacturing method according to an embodiment is a method for manufacturing molded coal, which is a raw material for coke. The manufacturing method includes a preparing step, a mixing step, a molding step, a discharging step, a setting step, and a calculating step. In the preparing step, powdered coal is prepared. In the mixing step, a binder is added to the powdered coal and mixed to produce a mixture of the powdered coal and the binder. In the molding step, the mixture is molded into a number of molded coals. In the discharging step, a positive correlation between the size of each molded coal and the mass ratio of the binder added to the powdered coal to the powdered coal is derived in advance for each strength of the molded coal. In the setting step, a specific strength of the molded coal required in the molding step and a specific mass ratio of the binder required in the mixing step are set in advance. In the calculating step, a specific size of each molded coal corresponding to a specific mass ratio is calculated in advance based on the positive correlation corresponding to the specific strength. In the mixing step, a binder is added to the powdered coal in a specific mass ratio, and in the briquetting step, each briquette is briquetteed to a specific size or less (first configuration).

[0018] Briquettes are produced from a mixture of powdered coal and a binder. Therefore, when the amount of binder to be added is fixed, the specific mass ratio is determined based on the total amount of required briquettes. In the first configuration, when briquettes are briquetted, a specific size of the briquettes corresponding to the specific mass ratio is calculated based on the positive correlation between the size of each briquette at a specific strength and the mass ratio of the binder to the powdered coal. Furthermore, the briquettes are briquetted so that they are equal to or smaller than the calculated specific size. Briquettes of a specific size produced at a specific mass ratio satisfy the specific strength.

[0019] Furthermore, as described above, at a specific mass ratio, as the size of the molded coal decreases, the strength of the molded coal increases. Therefore, molded coal below a specific size becomes molded coal with a specific strength or higher. In other words, the molded coal is manufactured by determining the size of the molded coal based on the amount of binder used so that the molded coal has a strength equal to or higher than the specific strength. Therefore, the molded coal manufactured by the first configuration always has a strength equal to or higher than the specific strength, regardless of the amount of binder used. Therefore, according to the first configuration, molded coal with sufficient strength can be manufactured with a limited amount of binder.

[0020] In the manufacturing method according to the first aspect, in the preparation step, coal may be pulverized to produce powdered coal (second aspect).

[0021] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or equivalent components are designated by the same reference numerals, and the same description will not be repeated.

[0022] [Manufacturing method of molded charcoal] FIG. 1 is a flowchart illustrating a method for producing molded coal according to this embodiment. Referring to FIG. 1, the method for producing molded coal includes a production condition setting step S1 and a production step S2. The production condition setting step S1 includes a derivation step S11, a setting step S12, and a calculation step S13. The production step S2 includes a preparation step S21, a mixing step S22, and a molding step S23. In this embodiment, the production step S2 is performed according to conditions predetermined through the production condition setting step S1. A large number of molded coals are produced through the production step S2. The produced molded coals are used as raw materials for coke.

[0023] Each step will be described in detail below. For convenience, the basic configuration of the manufacturing step S2 will be described first. After that, the configuration of the manufacturing condition setting step S1 will be described, and then the configuration of the manufacturing step S2, which is carried out in accordance with the conditions determined in the manufacturing condition setting step S1, will be described.

[0024] (Manufacturing process S2) (Preparation step S21) In the preparation step S21, pulverized coal is prepared. The pulverized coal is a raw material for briquettes, and the raw material for the pulverized coal is coal. In this embodiment, the coal is pulverized by a pulverizer to produce the pulverized coal. In this way, the pulverized coal is prepared. A known pulverizer can be used as the pulverizer. The particle size of the pulverized coal is changed as necessary. For example, the particle size of the pulverized coal is 0.5 mm to 2.0 mm.

[0025] (Mixing process S22) In the mixing step S22, a binder is added to the powdered coal and mixed to produce a mixture of the powdered coal and binder. The binder is added to maintain the shape of the molded coal. The binder is, for example, coal tar or its distillate. However, other known binders (e.g., soft pitch) may also be used as the binder. The amount of binder added to the powdered coal is controlled by the mass ratio of the binder to the powdered coal (RT ratio). In the mixing step S22, the mixture of the powdered coal and binder is mixed using a known mixer, and the binder is dispersed substantially uniformly in the powdered coal.

[0026] (Molding process S23) In the molding step S23, the mixture produced in the mixing step S22 is molded into a large number of molded charcoals. The molded charcoals can be molded using a known molding machine. For example, the molding machine includes a pair of roll dies, each of which has a large number of pockets formed on its surface. The mixture is supplied into the gap between the pair of roll dies that rotate relative to each other, and is compressed one after another by the pockets formed on the surface of the roll dies. This results in a large number of molded charcoals that reflect the shape (size) of the pockets. The molded charcoal has, for example, a flattened ellipsoid shape. The molded charcoal may have a flattened sphere shape or another shape (e.g., a cone shape).

[0027] (Manufacturing condition setting process S1) As described above, the manufacturing condition setting step S1 includes the derivation step S11, the setting step S12, and the calculation step S13.

[0028] (Derivation step S11) In the deriving step S11, a positive correlation between the size of each briquette and the mass ratio of the binder to the powdered coal is derived in advance for each strength of the briquette, based on past production results of briquette.

[0029] The strength of the molded coal is measured, for example, by trommel strength, which is measured using a trommel strength measuring device including a drum testing machine. The drum testing machine includes a rotatable drum with blades on the inner surface of the drum.

[0030] Five kilograms of briquettes to be measured are placed in a drum, which is then rotated at 12 rpm for five minutes. As the drum rotates, the briquettes are repeatedly stirred up by the blades and dropped. This causes the briquettes to be subjected to repeated dropping impacts. The briquettes are then removed from the drum and sieved through a 15 mm sieve. Briquettes with dimensions of approximately 15 mm or larger remain on the sieve. The mass of the briquettes on the sieve is then measured. The trommel strength of the briquettes is expressed as a percentage of the mass of the briquettes on the sieve relative to the mass of the briquettes placed in the drum. In other words, the trommel strength represents the yield of briquettes that can withstand dropping impacts under given conditions.

[0031] The rotation speed and rotation time of the drum can be set based on the drop impact given to the molded coal in actual operation. Specifically, the rotation speed and rotation time conditions can be set so that the drop impact given to the molded coal in the drum testing machine is comparable to the drop impact given to the molded coal in actual operation.

[0032] The sieve opening can be set based on the size of molded coal acceptable as a raw material for coke. The acceptable molded coal size is the size of molded coal that will improve the strength of the coke produced. Therefore, the sieve opening is not limited to 15 mm and may be changed as needed.

[0033] The size of the briquettes is expressed, for example, by the volume or dimensions (short side, long side, radius, etc.). That is, the size of the briquettes is expressed by an index that is proportional to the mass of the briquettes. Generally, it is preferable that the density of the briquettes is high, and it is considered that the difference in density between individual briquettes is small. Therefore, for example, the mass of an individual briquettes can be said to correspond to the volume of the individual briquettes. In this embodiment, the density of the briquettes is, for example, 0.9 g / cm 3 ~1.2g / cm 3 is.

[0034] FIG. 2 is a schematic diagram showing the relationship between the size of each formed coke and the RT ratio for each strength of the formed coke. In FIG. 2, the horizontal axis represents the size of the formed coke alone, and the vertical axis represents the RT ratio. The RT ratio is the mass ratio of the binder powder added. The mass ratio (RT ratio) of the binder to the pulverized coal in the mixture produced in the mixing step S22 is equivalent to the mass ratio of the binder to the pulverized coal in the formed coke alone formed in the forming step S23.

[0035] In FIG. 2, the relationship between the size of the formed coke alone and the RT ratio is shown for the cases where the strength (Trommel strength) of the formed coke is X1, X2, X3 (X1 < X2 < X3). A positive correlation is recognized between the size of the formed coke and the RT ratio at any strength. As shown in FIG. 2, in this embodiment, this positive correlation is represented by a linear function. That is, the RT ratio is proportional to the size of the formed coke. Also, generally, for formed cokes of the same size, the higher the RT ratio, the higher the strength of the formed coke. Therefore, as the strength of the formed coke increases, the above positive correlation shifts upward. That is, X1 < X2 < X3.

[0036] Since the RT ratio is proportional to the size of the formed coke, it can be said that when producing formed cokes having the same Trommel strength, the RT ratio can be reduced by reducing the size of the formed coke. For this reason, if the size of the formed coke is small, it becomes possible to reduce the amount of binder used. However, since the size of the formed coke affects the strength of the coke, the production amount of the coke, and the production amount of the formed coke, etc., considering such influence, it is preferable that the size of the formed coke is moderately large.

[0037] Referring to Figure 2, for briquettes with the same RT ratio, the smaller the briquettes' size, the higher the strength of the briquettes. This can be explained by the difference in potential energy equivalent to the impact of a fall. Briquettes can be considered as falling objects. Since the size of a briquettes corresponds to the mass of the briquettes, the potential energy of the briquettes is proportional to the size of the briquettes. The strength of the briquettes increases as the impact of a fall on the briquettes, i.e., the potential energy of the briquettes, decreases. Therefore, when producing briquettes with the same RT ratio, it can be said that the strength of the briquettes can be increased by reducing the size of the briquettes.

[0038] 2, for example, for briquettes having the same R-RT ratio, if the size of the briquettes is V2 or less, the strength of the briquettes will be X2 or more. In other words, for briquettes having the same R-RT ratio and strength of X2 or more, the upper limit of the briquettes size is V2.

[0039] (Setting process S12) In the setting step S12, a specific strength of the molded coal required in the molding step S23 and a specific mass ratio of the binder to powder coal required in the mixing step S22 are set in advance. The specific strength of the molded coal is the strength (trommel strength) required for the molded coal assuming actual operation. Therefore, the specific strength of the molded coal is set depending on the conditions of the molded coal transportation equipment, coke oven, etc. The specific mass ratio in the mixture before molding is set based on the limited amount of binder used and the total mass of the molded coal to be produced.

[0040] (Calculation step S13) In the calculation step S13, a specific size of each briquette corresponding to a specific mass ratio is calculated based on the positive correlation corresponding to the specific strength, i.e., the positive correlation between the size of each briquette and the mass ratio of the binder to the powdered coal derived in the derivation step S11. The specific strength of the briquette is the strength of the briquette set in the setting step S12. With reference to Fig. 2, for example, if the specific strength of the briquette is X2 and the specific mass ratio (RT ratio) of the binder is R, the specific size of the briquette is V2.

[0041] (Manufacturing process S2 after manufacturing condition setting process S1) As described above, the manufacturing process S2 after the manufacturing condition setting process S1 includes the preparation process S21, the mixing process S22, and the molding process S23.

[0042] In the preparation step S21, pulverized coal is prepared. Next, in the mixing step S22, a binder is added to the prepared pulverized coal and mixed to produce a mixture of pulverized coal and binder. At this time, the binder is added to the pulverized coal at a specific mass ratio. The specific mass ratio of the binder is the RT ratio set in the setting step S12.

[0043] Next, in the molding step S23, each molded coal is molded to have a specific size or less. The specific size of the molded coal is the size of the molded coal that corresponds to the specific mass ratio calculated in the calculation step S13. The roll mold used in this process has pockets that reflect the shape of the molded coal that is less than the specific size. Specifically, with reference to FIG. 2, for example, if the specific strength of the molded coal is X2 and the specific mass ratio of the binder is R, the specific size of the molded coal is V2. In this case, the pockets of the roll mold need only be formed so as to produce molded coal having a size less than V2, for example, V1.

[0044] [effect] In this embodiment, before molding the molded coal, in the deriving step S11 and the calculating step S13, the specific size of each molded coal is calculated based on the specific strength and specific mass of the molded coal determined in the setting step S12. Furthermore, in the molding step S23, each molded coal is molded to be equal to or smaller than the calculated specific size. That is, the size of the molded coal is determined based on the amount of binder used so that the molded coal has a strength equal to or greater than the specific strength. Therefore, the molded coal produced according to this embodiment always has a strength equal to or greater than the specific strength, regardless of the amount of binder used. Therefore, according to the molded coal manufacturing method according to this embodiment, molded coal with sufficient strength can be produced using a limited amount of binder.

[0045] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure. [Example]

[0046] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to the following examples.

[0047] In this example, the trommel strength of each briquette was investigated by changing the size of each briquette and the RT ratio. As a result, a positive correlation (FIG. 2) was derived between the size of each briquette and the RT ratio for each strength of the briquette used in this disclosure.

[0048] In this example, the volume of each briquette was used as the size of each briquette. 3 ,30cm 3 The trommel strength (%) of each volume of briquette was measured. 47 samples of each volume of briquette were prepared.

[0049] Figure 3 shows the results of measuring the trommel strength against the RT ratio for each volume of each briquette. 3 The data is marked with a circle and the volume is 30cm 3 The data for each volume are plotted with crosses. The data for each volume were fitted using the least squares method. Volume 10cm 3 The approximate line for the data is the dashed line, and the volume is 30 cm 3 The approximate line for the data is shown by the dashed line. The RT ratio on the horizontal axis of Figure 3 is calculated for a volume of 30 cm 3 The approximate line indicates the ratio to the RT ratio at which the strength is 90% (herein referred to as the "binder ratio"). For both volumes, the trommel strength tended to increase as the RT ratio (binder ratio) increased.

[0050] Furthermore, based on the approximation line in Figure 3, the relationship between the volume of each molded coal and the RT ratio (binder ratio) when the trommel strength is 90%, 92%, and 94% is shown in Figure 4. Referring to Figure 4, it is clear that there is a positive correlation between the volume of each molded coal and the RT ratio (binder ratio) at each strength.

[0051] As described above, this example shows that a positive correlation can be derived between the size of each briquette and the RT ratio for each strength of the briquette used in the present disclosure.

Claims

1. A method for producing molded coal, which is a raw material for coke, comprising: a preparation step of preparing powdered coal; a mixing step of adding a binder to the powdered coal and mixing the powdered coal to produce a mixture of the powdered coal and the binder; briquetting the mixture into a number of briquettes; a deriving step of deriving in advance, for each strength of the molded coal, a positive correlation between a size of each molded coal and a mass ratio of the binder to the powdered coal; a setting step of setting in advance a specific strength required in the molding step among the strengths of the molded charcoal and a specific mass ratio required in the mixing step among the mass ratios of the binder; a calculating step of calculating a specific size corresponding to the specific mass ratio among the sizes of each of the briquettes based on the positive correlation corresponding to the specific strength; Equipped with In the mixing step, the binder is added to the powdered coal in the specific mass ratio, In the molding step, each of the molded coals is molded to have a size equal to or smaller than the specific size.

2. The method of claim 1, In the preparation step, coal is pulverized to produce the powdered coal.

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