Method for manufacturing molded charcoal, and method for manufacturing molded charcoal and coke.

Abstract

To provide a production method of charcoal briquettes that prevents the binder from scattering to the periphery when the binder is added to coal powder and mixed.SOLUTION: The production method of charcoal briquettes comprises: a mixing step of mixing coal powder and rice powder having a particle size of 100 μm or more and 200 μm or less to form a mixture; and a molding step of molding the mixture to produce charcoal briquettes.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing formed coal, formed coal, and a method for producing coke. Background Art

[0002] In iron manufacturing processes, various powdered raw materials are briquetted for use for the purposes of reducing raw material costs and reducing environmental load by preventing scattering. For example, lumpy formed coal obtained by briquetting powdered coal is used in coke production. Since formed coal is obtained by molding powdered coal into lumps, scattering of dust can be suppressed even during handling in storage and transportation. Furthermore, since inexpensive low-grade powdered coal can be converted into high-quality coke, effective utilization of natural resources can be achieved and raw material costs can be reduced.

[0003] Generally, powdered coal does not form lumps on its own. For this reason, formed coal is produced by mixing a binder into powdered coal and then performing pressure molding with a molding machine. In order to suppress pulverization during handling, formed coal is required to have a strength of at least a certain level.

[0004] As a technique for producing formed coal, Patent Document 1 discloses a technique for producing formed coal using, as a solid caking filler, a crushed caking filler (binder) that contains 50 mass% or more and 100 mass% or less of fine particles having a particle diameter of 0.01 to 0.3 mm. Patent Document 2 discloses a technique for obtaining lumps by adding starch, which has been gelatinized by a starch gelatinization apparatus, to powdered solid fuel such as powdered coal, and then kneading and molding the mixture. According to Patent Document 2, 10 to 17% by weight of gelatinized starch is added to the powdered solid fuel.

[0005] Patent Document 3 discloses a method for producing molded coal by adding starch to powdered coal, mixing, and press-molding. This method involves dissolving starch in hot water to gel it, then drying it to make a powder, which is then added to the powdered coal. According to Patent Document 3, it is preferable to add 1 to 10% by mass of starch relative to the mass of the molded product. Patent Document 4 discloses a method for mixing powdered coal or other powder with starch as a binder. This method involves mixing the powder and starch in an unheated state, and then mixing them in a heated state to obtain a mixture which is then molded. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2011 / 065303 [Patent Document 2] Japanese Patent Application Publication No. 62-15294 [Patent Document 3] Japanese Patent Publication No. 2003-64377 [Patent Document 4] Japanese Patent Publication No. 2022-112263 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the above-mentioned conventional technology has the following problems. Patent Document 1 uses petroleum-based pitch or coal-based pitch as a solid adhesive filler. Pitch such as coal tar pitch is harmful to the human body and poses safety and health risks when handled. Therefore, there is a problem that measures to prevent contact with workers during the handling of the mixture and molding process when manufacturing molded coal are costly. In addition, petroleum-based pitch and coal-based pitch emit odors, which also leads to a deterioration of the working environment in the molded coal manufacturing process.

[0008] Patent Document 2 exemplifies corn starch and potato starch as examples of starch powder used in binders. These primarily use β-starch as a raw material, and the α-starch gelatinized by a gelatinization device is used as the binder. However, since the gelatinized α-starch is a gel-like adhesive substance, it is difficult to uniformly mix the powdered coal and the binder when mixing in a kneader. This leads to the problem of reduced productivity in the kneading process. On the other hand, in order to uniformly mix the powdered coal and the binder, it becomes necessary to add a relatively large amount of starch to the powdered solid fuel. This leads to the problem of increased manufacturing costs for molded coal.

[0009] Patent Document 3 describes a binder made by dissolving starch in hot water to gel it, then drying and powdering it, which is added to powdered coal. Unlike Patent Document 2, since the β-starch is converted to a paste-like α-starch before being powdered, it is thought that the powdered coal and binder are more easily mixed when kneaded in a kneader, and the amount of binder added can also be reduced. However, Patent Document 3 describes the use of powdered tapioca as the starch. Generally, tapioca flour is spherical or hemispherical with a particle size of about 4 to 35 μm, and because the particle size of tapioca flour is small, there is a problem that the tapioca flour will scatter into the surroundings during the kneading process, worsening the working environment. In addition, if tapioca flour scatters into the surroundings, the consumption of binder will increase, which will increase production costs. On the other hand, if water is added to prevent the scattering of tapioca flour, clumps of powder tend to form. Therefore, a challenge arises in that it is difficult to uniformly mix the powdered coal and the binder during the mixing process.

[0010] Patent Document 4 describes a method in which powdered coal and starch powder are mixed in an unheated state, and then further mixed in a heated state. This process gelatinizes the β-starch during the formation of the mixture, increasing the bonding strength and achieving uniform dispersion of the binder. However, since the particle size of starch powder is generally around 1 to 50 μm, there is a problem that the starch powder scatters into the surroundings during the kneading process, worsening the working environment. Furthermore, when starch powder scatters into the surroundings, the amount of binder added increases, leading to increased production costs.

[0011] The present invention was made to solve the above problems, and its objective is to provide a method for producing molded coal that can suppress the scattering of the binder around the coal when the binder is added to and kneaded with coal powder. Furthermore, another objective of the present invention is to provide a method for producing molded coal and coke that can suppress the scattering of the binder around the coal during production. [Means for solving the problem]

[0012] The means to solve the above problems are as follows: [1] A method for producing molded charcoal, comprising: a kneading step of kneading coal powder and rice powder having a particle size of 100 μm or more and 200 μm or less to form a kneaded product; and a molding step of molding the kneaded product to produce molded charcoal. [2] The method for producing molded charcoal according to [1], wherein the content of the powdered rice in the kneaded product is 1.0% by mass or more and 3.0% by mass or less. [3] The method for producing molded charcoal according to [1] or [2], wherein the powdered rice is produced by crushing stored rice. [4] The method for producing molded charcoal according to any one of [1] to [3], wherein the powdered rice is produced by crushing α rice, and in the kneading step, steam is supplied to adjust the moisture content of the kneaded material to 11% by mass or more and 15% by mass or less. [5] The method for producing molded charcoal according to any one of [1] to [3], wherein the powdered rice is produced by grinding β rice, and in the kneading step, steam is supplied to adjust the moisture content of the kneaded material to 11% by mass or more and 15% by mass or less, and the kneaded material is heated to 70°C or higher. [6] A molded coal comprising coal powder in which a proportion of particles having a particle diameter of 3.0 mm or less is 80% by mass or more, and rice powder having a particle diameter of 100 µm or more and 200 µm or less. [7] The molded coal according to [6], wherein a content of the rice powder is 1.0% by mass or more and 3.0% by mass or less. [8] A method for producing coke, comprising charging molded coal produced by the method for producing molded coal according to [1] or [2] into a coke oven, and carbonizing the charged molded coal to produce coke.

Effects of the Invention

[0013] According to the present invention, since crushed rice containing rice powder having a particle diameter of 100 µm or more and 200 µm or less is used as a binder, scattering of the binder is suppressed, and deterioration of the working environment can be suppressed. Furthermore, by suppressing scattering of the binder, an increase in the added amount of the binder is suppressed, and an increase in production cost can also be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] [Figure 1] FIG. 1 is a schematic diagram showing a molded coal production facility in which the method for producing molded coal according to the present embodiment can be implemented. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of a kneader. [Figure 3] FIG. 3 is a graph showing the relationship between the content of rice powder and the drop strength of molded coal. [Figure 4] FIG. 4 is a graph showing the relationship between the moisture content and the drop strength of molded coal. [Figure 5] FIG. 5 is a graph showing the relationship between the heating temperature and the drop strength of molded coal. [Figure 6] FIG. 6 is a graph showing the relationship between the content of rice powder and the drop strength of molded coal. MODE FOR CARRYING OUT THE INVENTION

[0015] Hereinafter, the present invention will be specifically described through embodiments of the present invention. The following embodiments illustrate preferred examples of the present invention, and the present invention is not limited in any way by these embodiments.

[0016] FIG. 1 is a schematic diagram showing molded coal production equipment 26 capable of implementing the method for producing molded coal according to the present embodiment. In the method for producing molded coal according to the present embodiment, as shown in FIG. 1, coal powder 10 and rice powder 12 having a particle diameter of 100 μm to 200 μm are charged into a kneader 22, and kneaded in the kneader 22 to produce a kneaded product 14. This step is the kneading step. Note that rice powder having a particle diameter of 100 μm or more and 200 μm or less refers to rice powder that is sieved through a sieve with an opening of 200 μm and remains on a sieve with an opening of 100 μm.

[0017] For the coal powder 10, pulverized coal which is a raw material for the molded coal 18 is used. For the coal powder 10, besides caking coal, low-grade weakly caking coal is used. The coal powder 10 may include, for example, pulverized coal generated in a coke oven recovered by a dust collector.

[0018] The smaller the particle size of the coal powder 10 is, the more contact points there are between the coal powder 10 and the rice powder 12 serving as a binder, so the strength of the produced molded coal 18 is improved. For this reason, it is preferable that the content of coal powder having a particle diameter of 3.0 mm or less in the coal powder 10 is 80% by mass or more, and more preferably 90% by mass or more. Note that "having a particle diameter of 3.0 mm or less" refers to a particle size sieved through a sieve with an opening of 3.0 mm. When using coal powder in which the content of coal powder having a particle diameter of 3.0 mm or less is less than 80% by mass, the coal powder may be pulverized or mixed with other coal powder of fine particle size to adjust the particle size to fall within the above range.

[0019] In the method for producing molded charcoal according to this embodiment, powdered rice 12 with a particle size of 100 μm or more and 200 μm or less is used as a binder for producing molded charcoal 18. Powdered rice 12 with a particle size of 100 μm or more and 200 μm or less is produced by crushing raw rice in a pulverizer. The raw rice may be brown rice with the rice bran still attached or white rice with the rice bran removed. The raw rice is not limited by standards or origin as edible rice, and non-glutinous rice or glutinous rice may be used. The raw rice only needs to contain starch in the central part of the rice grain after removing the bran layer. The raw rice should contain 70% by mass or more of starch, and may also contain protein, lipids, vitamins, etc.

[0020] The size of the raw rice is not particularly limited, but it is preferable that the grain thickness is 1.7 mm or more and the weight of each grain is 17 g or more. However, the raw rice may contain broken rice grains with a thickness of less than 1.7 mm.

[0021] The raw rice may contain beta-starch, which is its natural crystalline structure, or it may have been converted to a gelatinized state (alpha-starch) through cooking or other means. For example, much of the rice stored as emergency supplies has already become alpha-starch, and it is preferable to use emergency rice that has passed its expiration date. In this case, the raw rice may be steamed rice that has been rapidly dried with hot air, or cooked rice that has been rapidly cooled and dried under reduced pressure. This makes it possible to reduce food waste without discarding emergency rice that has passed its expiration date.

[0022] As a binder for manufacturing molded coal 18, powdered rice 12 with a particle size of 100 μm or more and 200 μm or less is used. If the particle size of the powdered rice 12 is less than 100 μm, the powdered rice will scatter into the surroundings during the mixing process with coal powder 10, worsening the working environment. Furthermore, if the powdered rice scatters into the surroundings, the amount of binder consumed will increase, increasing production costs. On the other hand, if the particle size of the powdered rice 12 exceeds 200 μm, the number of contact points between the coal powder 10 and the powdered rice 12 will decrease, reducing the drop strength of the molded coal 16. For this reason, in the method for manufacturing molded coal according to this embodiment, powdered rice 12 with a particle size of 100 μm or more and 200 μm or less is used. Preferably, the particle size of the powdered rice 12 is 130 μm or more and 180 μm or less.

[0023] Commercially available rice flour mainly has an average particle size of 30 μm to 50 μm, which does not satisfy the particle size requirement for rice flour 12. Also, commercially available rice mainly has a grain thickness of 1.7 mm or more, which does not satisfy the particle size requirement for rice flour 12. For this reason, rice flour 12 is manufactured by grinding raw rice using a grinder.

[0024] As the grinder, a fine grinder capable of grinding raw materials of about 1 to 5 mm to 200 μm or less can be used. Any grinding principle can be applied to the grinder. As the grinder, a grinder that uses forces such as compression, impact, shear, and friction to grind the raw rice may be used. For example, known grinding methods such as a roller mill that compresses and grinds the raw rice between a rotating roller and a table, a hammer mill that grinds the raw rice by impacting it with a high-speed rotating hammer, and a rotary mill that grinds the raw rice by filling a rotating cylindrical container with raw rice and rotating the cylindrical container may be used. Alternatively, a household flour mill may be used as an inexpensive grinder. For example, a high-speed mill manufactured by Labonect Co., Ltd. may be used. It is preferable to use a dry grinder. Wet grinders are not preferred because the ground rice may agglomerate, making it difficult to uniformly mix it with coal powder in the kneading process.

[0025] The crushed rice obtained by crushing the raw rice in a pulverizer is then processed using a classifying device such as a sieve to produce powdered rice 12 with a particle size of 100 μm or more and 200 μm or less. However, since it is difficult to adjust the particle size to the above range, the kneader 22 may contain rice flour with an average particle size of less than 100 μm or coarsely crushed rice with an average particle size of more than 200 μm, along with the powdered rice 12 with a particle size of 100 μm or more and 200 μm or less. In this case, the mass ratio of powdered rice 12 to the total amount of rice is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass.

[0026] Next, the mixing process will be described. Using powdered rice 12 with adjusted particle size as a binder, the powdered rice 12 and coal powder 10 are mixed using a mixer 22. In the mixing process, it is preferable to add powdered rice 12 to the coal powder 10 so that the amount of powdered rice 12 in the mixed product 14 after mixing is between 1.0% by mass and 3.0% by mass. If the amount of powdered rice 12 is less than 1.0% by mass, the drop strength of the molded coal 16 decreases, which is undesirable. On the other hand, if the amount of powdered rice 12 exceeds 3.0% by mass, there is almost no increase in the drop strength of the molded coal 16, and the coal content decreases. However, when using α-rice as the raw material rice, the dispersibility of the binder in the mixture decreases slightly compared to when using β-rice. For this reason, when using α-rice, it is preferable to set the amount of α-rice to between 1.2% by mass and 3.0% by mass.

[0027] As described above, in the method for producing molded coal according to this embodiment, since powdered rice 12 with a particle size of 100 μm or more and 200 μm or less is used as the binder, scattering of the binder into the surrounding area during the kneading process can be suppressed. This suppresses deterioration of the working environment during the kneading process. Furthermore, by suppressing the scattering of the binder, an increase in the amount of binder added can be suppressed, and an increase in production costs can also be suppressed. In addition, the number of contact points between the coal powder 10 and the binder is ensured, and the adhesive strength between the coal powder 10 and the binder is increased. As a result, it becomes possible to produce molded coal with high strength.

[0028] Next, the kneader 22 will be described. The kneader can be any kneader capable of thoroughly mixing the coal powder 10 and the rice powder 12, and there are no particular restrictions on its capacity or processing volume. The kneader 22 used in the method for producing molded coal according to this embodiment is, for example, a Henschel type kneader, but kneaders such as horizontal paddle type and vertical paddle type may also be used.

[0029] Figure 2 is a schematic cross-sectional view showing an example of a kneader 22. The kneader 22 has a charging section 30, a discharge section 32, a rotating shaft 34, paddle blades 36, and screw blades 38. Coal powder 10 and powdered rice 12, which is a binder in a preset ratio, are charged into the charging section 30. Upstream of the kneader 22, there is a paddle blade 36 that rotates on the rotating shaft 34. The paddle blade 36 has a flat plate (paddle), and the rotation of this plate mixes the coal powder 10 and powdered rice 12. Downstream of the kneader 22, there is a screw blade 38 that rotates on the rotating shaft 34. The screw blade 38 has propeller-shaped blades. As the propeller-shaped blades rotate, the kneaded mixture 14, whose viscosity has increased during the mixing process of coal powder 10 and powdered rice 12, is further kneaded and transferred to the downstream side of the kneader 22. The kneaded material 14, which has been transferred to the downstream side of the kneader 22, is discharged from the discharge section 32.

[0030] The kneader 22 has a plurality of steam outlets 40 that supply heated steam to the mixture during kneading. Heated steam is supplied from the steam outlets 40 to the coal powder 10 and rice flour 12. The kneader 22 may also be provided with heating means (not shown) for heating the mixture. The heating means may not only be heated steam supplied from the steam outlets 40, but may also be microwave irradiation, for example, or electric heaters or gas combustion devices may be provided around or inside the kneader 22 for heating.

[0031] When using α-rice as the raw material, the mixing process in the kneader 22 does not require external heating. The starch contained in α-rice is gelatinized. Even in powdered rice obtained by crushing α-rice, the starch contained in the powdered rice remains in its gelatinized state. Therefore, in the mixing process, simply adjusting the moisture content to 11% by mass or more and 15% by mass or less increases the viscosity of the powdered rice 12, generating a lump-like mixture 14. In this case, there is no need to heat the mixture 14 in the mixing process. When using α-rice as the raw material, the mixing time in the kneader 22 should be 15 seconds or more. Since a gelatinized binder is used, a lump-like mixture 14 is generated even with a short mixing process.

[0032] On the other hand, when β rice is used as the raw material, it is preferable to supply steam during the kneading process in the kneader 22 to adjust the moisture content of the kneaded material 14 to 11% by mass or more and to heat the kneaded material 14 to 70°C or higher. For example, in the kneader 22 shown in Figure 2, it is preferable to knead in an unheated state in the upstream stage, and then in the downstream stage, to knead while heating by blowing heated steam from the steam nozzle 40. The reason for kneading in an unheated state in the upstream stage of the kneader 22 is to uniformly mix the powdered rice 12, which has a particle size of 100 μm or more and 200 μm or less, with the coal powder 10. Furthermore, the reason for heating while supplying steam in the downstream stage of the kneader 22 is to gelatinize the β rice mixed with the coal powder 10 and increase the adhesive strength between the coal powder 10 and the powdered rice 12.

[0033] In this case as well, it is preferable to adjust the moisture content of the kneaded mixture 14 to 11% by mass or more and 15% by mass or less. If the moisture content of the kneaded mixture 14 is less than 11% by mass, the gelatinization of the β rice will not proceed sufficiently, and the adhesive strength between the coal powder 10 and the powdered rice 12 will not be high, which is undesirable. Also, if the moisture content of the kneaded mixture 14 exceeds 15% by mass, the adhesive strength between the coal powder 10 and the powdered rice 12 will decrease, which is undesirable as it will reduce the strength of the molded charcoal and require a long time to dry after it has been formed into molded charcoal. Furthermore, it is preferable to heat the mixture to 70°C or higher during the kneading process. Since the gelatinization start temperature of starch is 60°C or higher, heating to 70°C or higher allows the β rice to be sufficiently gelatinized. On the other hand, since increasing the heating temperature only increases the consumption of thermal energy, it is preferable to heat the mixture to 90°C or lower during the kneading process.

[0034] When β-rice is used as the raw material rice 11, it is preferable that the mixing time in the kneader 22 be 150 seconds or more. This allows the coal powder 10 and the binder, which is the powdered rice 12, to be mixed uniformly, and the β-rice to be sufficiently gelatinized.

[0035] Next, the molding process will be described. The kneaded mixture 14, formed into a lump by the powdered rice 12, is pressurized and molded by a molding machine 24 to produce molded charcoal 16. It is preferable to use a double-roll molding machine as the molding machine 24. Double-roll molding machines are relatively simple in design, highly versatile, and make it easy to apply compressive force to the powder, thus enabling the production of molded charcoal with high strength. However, the molding machine is not limited to a double-roll molding machine; any molding machine using a roll compression, rolling, or extrusion method may be used.

[0036] The shape of the molded charcoal 1 formed using the molding machine 24 is not particularly limited and may be, for example, a pillow shape, a masec shape, or an egg shape. Since these shapes do not have corners, powdering during handling can be suppressed compared to molded charcoal with corners. The size of the molded charcoal is preferably between 15 mm and 50 mm.

[0037] The molded coal 16 produced in the manner described above uses coal powder 10 in which 80% or more by mass consists of particles with a particle size of 3.0 mm or less. As a result, the molded coal is composed of coal powder with a particle size of 3.0 mm or less, in which powdered rice 12 with a particle size of 100 μm to 200 μm is dispersed. Such molded coal has the characteristic of having high drop strength and being less likely to pulverize during handling. Furthermore, since the molded coal 16 contains powdered rice 12 with a particle size of 100 μm to 200 μm, scattering during mixing can be suppressed compared to the case where powdered rice with a particle size of less than 100 μm is included but powdered rice 12 with a particle size of 100 μm to 200 μm is not included.

[0038] The method for producing molded coal according to this embodiment allows for the production of molded coal with high drop strength, resulting in molded coal that is less prone to pulverization during storage and transportation. Consequently, by charging this molded coal into a coke oven and performing carbonization, high-strength, high-quality coke can be produced from inexpensive, low-grade coal powder. [Examples]

[0039] <Example 1> This section describes an example in which molded coal was produced from a mixture of powdered rice with coal powder, after which powdered rice with a predetermined particle size distribution was produced by crushing raw rice into powder using a pulverizer and then classifying it. Beta rice and alpha rice were used as raw rice. White rice was used as the beta rice. In addition, steamed white rice rapidly dried with hot air was used as the alpha rice. In both cases, the mass of particles with a particle size of 1.7 to 5.5 mm accounted for 90% or more of the total mass of the raw rice. As for the coal powder, 95% of the mass of particles with a particle size of less than 3 mm was used.

[0040] The pulverizer used was a rotary mill that pulverizes the raw rice by filling a rotating cylindrical container with raw rice and rotating the cylindrical container. Using the pulverizer and classifier, in the inventive example, the particle size of the powdered rice was adjusted to a range of 100 μm to 200 μm, and the average particle size was adjusted by adjusting the particle size distribution. On the other hand, in the comparative example, the raw rice was pulverized to include coarse powder with a particle size exceeding 200 μm. Table 1 shows the average particle size of the powdered rice used in the binder and the content of powdered rice relative to the molded charcoal. Note that the average particle size is the mass-average particle size. The mass-average particle size is the average particle size obtained from the measured quantity that there are wi [g] of particles with particle size Dp.

[0041] In the mixing process, powdered rice, obtained by crushing raw rice, was added as a binder to the coal powder to form a mixture. In the mixing process, for the mixture using α-rice as the raw rice, steam was supplied at room temperature without heating to adjust the moisture content of the mixture to 13% by mass. On the other hand, for the mixture using β-rice as the raw rice, the temperature of the mixture was adjusted to 80°C to adjust the moisture content to 13% by mass.

[0042] The molding process involved using a pressure roll molding machine to apply compressive force to the mixture kneaded in the kneader, producing 46mm x 46mm x 38mm Masec-shaped molded charcoal. The drop strength of the molded charcoal produced in this way was evaluated. Specifically, after allowing the molded charcoal to cure naturally for 2 hours, 10 pieces of molded charcoal produced under the same manufacturing conditions were dropped three times from a height of 2m, and the ratio of the weight of lumps of 15mm or more to the weight of the dropped molded charcoal was measured as the drop strength (%). If the drop strength measured by this evaluation method is 80% or higher, pulverization of the molded charcoal during storage and handling during transportation will be suppressed, and the scattering of dust due to pulverization of the molded charcoal will be suppressed. For this reason, using a drop strength of 80% as the standard, molded charcoal with a drop strength of 80% or higher was judged as acceptable, and molded charcoal with a drop strength of less than 80% was judged as unacceptable. Table 1 shows the evaluation results of the drop strength.

[0043] [Table 1]

[0044] Table 1 shows that when powdered rice with a particle size of 100 μm to 200 μm is used as a binder, molded charcoal with a drop strength of 80% or more can be produced. However, if the particle size of the powdered rice used in the kneading process is larger than 200 μm, the strength of the molded charcoal decreases, and it was not possible to produce molded charcoal with a drop strength of 80% or more. On the other hand, it was observed that the strength of the molded charcoal tended to increase as the particle size of the powdered rice used in the kneading process decreased. However, when the particle size of the powdered rice used is less than 100 μm, the powdered rice scatters into the surroundings when added in the kneading process, worsening the working environment. Furthermore, the scattering into the surroundings increases the amount of powdered rice that needs to be added to mix the required amount, thus increasing the production cost of molded charcoal.

[0045] For example, when using alpha rice as the raw material and grinding it to an average particle size of 55 μm, rice flour was used as a binder. To obtain molded coal with a drop strength of 80%, it was necessary to add 3.5% by mass of rice flour to the coal powder. In contrast, in the inventive example shown in Table 1, molded coal with sufficient strength could be produced by adding only about 1.5% by mass of rice flour to the coal powder. Thus, it was confirmed that by using rice flour with a particle size of 100 μm to 200 μm as a binder, molded coal with sufficient strength can be produced while suppressing deterioration of the working environment and an increase in the manufacturing cost of molded coal.

[0046] <Example 2> Next, we will describe Example 2, in which a binder was produced using white rice (β-rice) as the raw material, and molded charcoal was manufactured from a mixture obtained by kneading this binder with coal powder. The raw material rice and coal powder used were the same as in Example 1. In Example 2, powdered rice was crushed using a pulverizer and then classified using a classifier to prepare a binder with an average particle size of 140 μm to 160 μm and a particle size of 100 μm to 200 μm, with a ratio of 100% by mass of powdered rice. In Example 2, molded charcoal was manufactured by changing the powdered rice content, moisture content, and heating temperature during the kneading process, and the drop strength of the manufactured molded charcoal was measured.

[0047] Figure 3 is a graph showing the relationship between the powdered rice content and the drop strength of molded charcoal. The horizontal axis of Figure 3 represents the powdered rice content (mass%), and the vertical axis represents the drop strength of the molded charcoal (%). The molded charcoal whose drop strength was measured in Figure 3 was made by molding a mixture that was heated at 80°C during the mixing process and whose moisture content was adjusted to 13% by mass.

[0048] As shown in Figure 3, increasing the rice powder content in the molded charcoal to 1.0% by mass or more resulted in a drop strength of 80% or more. This result confirms that molded charcoal with sufficient drop strength can be produced by increasing the rice powder content (β-rice) with a particle size of 100 μm to 200 μm to 1.0% by mass or more. On the other hand, even when the rice powder content exceeded 2.0% by mass, the drop strength of the molded charcoal hardly increased.

[0049] Figure 4 is a graph showing the relationship between moisture content and the drop strength of molded charcoal. The horizontal axis of Figure 4 represents the moisture content (mass%) of the mixture, and the vertical axis represents the drop strength (%) of the molded charcoal. The molded charcoal whose drop strength was measured in Figure 4 was produced by heating the mixture at 80°C during the mixing process and molding the mixture with a rice flour content of 1.5 mass%.

[0050] As shown in Figure 4, the drop strength of the molded charcoal was 80% or more when the moisture content of the compound was within the range of 11% to 15% by mass. From these results, it was confirmed that molded charcoal with sufficient drop strength can be produced by adjusting the moisture content of the compound to 11% to 15% by mass.

[0051] Figure 5 is a graph showing the relationship between heating temperature and the drop strength of molded charcoal. In Figure 5, the horizontal axis represents the heating temperature (°C) during the mixing process, and the vertical axis represents the drop strength (%) of the molded charcoal. The molded charcoal whose drop strength was measured in Figure 5 was made by molding a mixture containing 1.5% by mass of rice flour and adjusted to a moisture content of 10-11% by mass.

[0052] As shown in Figure 5, raising the heating temperature in the kneading process to 70°C or higher resulted in a drop strength of 80% or more for the molded charcoal. This result confirms that molded charcoal with sufficient drop strength can be produced by heating the kneading material to 70°C or higher.

[0053] <Example 3> Next, we will describe Example 3, in which a binder was produced using α-rice as the raw material, and molded charcoal was manufactured from a mixture obtained by kneading it with coal powder. The α-rice used was steamed white rice that was rapidly dried with hot air. In Example 3, a binder was prepared in which the proportion of powdered rice with a particle size of 100 μm or more and 200 μm or less was 100% by mass by crushing and classifying the α-rice. In Example 3, molded charcoal was manufactured by changing the powdered rice content in the kneading process, and the drop strength of the manufactured molded charcoal was measured.

[0054] Figure 6 is a graph showing the relationship between the powdered rice content and the drop strength of molded charcoal. The horizontal axis of Figure 6 represents the powdered rice content (mass%), and the vertical axis represents the drop strength of the molded charcoal (%). The molded charcoal whose drop strength was measured in Figure 6 was molded from a mixture that was not heated during the mixing process and whose moisture content was adjusted to 13 mass%.

[0055] As shown in Figure 6, increasing the powdered rice content to 1.2% by mass or more resulted in a drop strength of 80% or more for the molded charcoal. This result confirms that molded charcoal with sufficient drop strength can be produced by increasing the powdered rice (α-rice) content of 1.2% by mass or more, with a particle size of 100 μm to 200 μm. Furthermore, it has been confirmed that when α-rice is used as the raw material, heating to 50°C during the kneading process results in a drop strength of 80% or more for the molded charcoal even with a powdered rice content of 1.0% by mass. [Explanation of symbols]

[0056] 10 Coal powder 12 Floured rice 14. Mixed ingredients 16 Molded coal 22 Mixing machine 24 Molding machine 26. Manufacturing equipment for molded charcoal 30 Loading section 32 Discharge section 34 Rotation axis 36 paddle feathers 38 Screw blades 40 Steam nozzles

Claims

1. A kneading process in which coal powder and rice flour with a particle size of 100 μm or more and 200 μm or less are kneaded together to form a paste, A molding process for molding the aforementioned mixture to produce molded charcoal, A method for producing molded charcoal, comprising the same characteristics.

2. The method for producing molded charcoal according to claim 1, wherein the content of the powdered rice in the kneaded product is 1.0% by mass or more and 3.0% by mass or less.

3. The method for producing molded charcoal according to claim 1 or claim 2, wherein the aforementioned rice powder is produced by crushing stored rice.

4. The aforementioned rice flour is produced by grinding α-rice. The method for producing molded charcoal according to claim 1 or claim 2, wherein in the kneading step, steam is supplied to adjust the moisture content of the kneaded material to 11% by mass or more and 15% by mass or less.

5. The aforementioned rice powder is produced by grinding alpha rice. The method for producing molded charcoal according to claim 3, wherein in the kneading step, steam is supplied to adjust the moisture content of the kneaded material to 11% by mass or more and 15% by mass or less.

6. The aforementioned rice flour is produced by grinding β-rice. The method for producing molded charcoal according to claim 1 or claim 2, wherein in the kneading step, steam is supplied to adjust the moisture content of the kneaded material to 11% by mass or more and 15% by mass or less, and the kneaded material is heated to 70°C or higher.

7. The aforementioned rice flour is produced by grinding β-rice. The method for producing molded charcoal according to claim 3, wherein in the kneading step, steam is supplied to adjust the moisture content of the kneaded material to 11% by mass or more and 15% by mass or less, and the kneaded material is heated to 70°C or higher.

8. Coal powder in which the proportion of particles with a diameter of 3.0 mm or less is 80% by mass or more, Floured rice with a particle size of 100 μm or more and 200 μm or less, Molded charcoal, including...

9. The molded charcoal according to claim 8, wherein the content of the aforementioned rice flour is 1.0% by mass or more and 3.0% by mass or less.

10. A method for producing coke, comprising charging molded charcoal produced by the method for producing molded charcoal according to claim 1 or claim 2 into a coke oven and producing coke by carbonization.

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