Production method of charcoal briquette, charcoal briquettes and production method of 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 molded coal, and a method for producing molded coal and coke. [Background technology]

[0002] In the steelmaking process, various powdered raw materials are briquetted for use in order to reduce raw material costs and reduce environmental impact by preventing scattering. For example, briquettes made from powdered coal are used to manufacture coke. Since briquettes are made by molding powdered coal into lumps, scattering of dust can be suppressed even during handling during storage and transportation. In addition, cheap, low-grade powdered coal can be made into high-quality coke, which makes effective use of natural resources and reduces raw material costs.

[0003] Generally, powdered coal does not form into lumps as it is. For this reason, powdered coal is mixed with a binder and then molded under pressure in a molding machine to produce molded coal. In order to prevent powdering during handling, molded coal needs to have a certain level of strength.

[0004] As a technique for producing briquettes, Patent Document 1 discloses a technique for producing briquettes using a pulverized binder containing 50% by mass or more and 100% by mass or less of fine particles having a particle size of 0.01 to 0.3 mm as a solid binder. Patent Document 2 discloses a technique for gelatinizing starch in a starch gelatinizer, adding it to a powdered solid fuel such as powdered coal, and kneading and molding to form agglomerates. Patent Document 2 discloses that 10 to 17% by weight of gelatinized starch is added to the powdered solid fuel.

[0005] Patent Document 3 discloses a method for adding starch to powdered coal, mixing and pressurizing to produce molded coal, in which starch is dissolved in hot water, gelled, dried and powdered and then added to the powdered coal. Patent Document 3 states that starch should be added in an amount of 1 to 10% by mass relative to the mass of the molded product. Patent Document 4 discloses a technique for mixing a powder such as powdered coal with starch as a binder, in which the powder and starch are mixed in an unheated state, and then mixed in a heated state to mold the resulting mixture. [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] JP 2003-64377 A [Patent Document 4] JP 2022-112263 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the above-mentioned conventional techniques have the following problems. In Patent Document 1, petroleum-based pitch or coal-based pitch is used as the solid caking filler. Pitch such as coal tar pitch is harmful to the human body, and handling it poses a safety and health risk. For this reason, there is a problem that measures to prevent contact with workers during handling of the mixture and molding work when producing molded coal are costly. In addition, petroleum-based pitch and coal-based pitch emit an odor, which also causes a problem of worsening the working environment during the molded coal manufacturing process.

[0008] Patent Document 2 lists corn starch and potato starch as examples of starch powder used as a binder. These mainly use β-starch as a raw material, and α-starch gelatinized by a gelatinizer is used as a binder. However, since gelatinized α-starch is a gel-like sticky substance, it is difficult to uniformly mix the powdered coal and the binder when kneading with a kneader. This poses a problem of reduced productivity in the kneading process using a kneader. On the other hand, if one tries 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 poses a problem of increased manufacturing costs for molded coal.

[0009] In Patent Document 3, starch is dissolved in hot water to gelatinize it, and then dried and powdered binder is added to powdered coal. Unlike Patent Document 2, β-starch is converted into pasty α-starch and then powdered, so that the powdered coal and the binder are easily mixed when kneaded with a kneader, and it is considered that the amount of binder added can be reduced. However, Patent Document 3 describes that powdered tapioca is used as the starch. Generally, tapioca flour is spherical or semispherical with a particle size of about 4 to 35 μm, and since the particle size of tapioca flour is small, there is a problem that the tapioca flour scatters around during the kneading process, worsening the working environment. In addition, there is also a problem that the consumption of the binder increases when the tapioca flour scatters around, and the production cost increases. On the other hand, when water is added to prevent the tapioca flour from scattering, the powder is likely to become lumpy. This causes a problem in that it is difficult to uniformly mix the powdered coal and the binder in the kneading process.

[0010] In Patent Document 4, powdered coal and starch powder are mixed in an unheated state, and then further mixed in a heated state, so that in the process of producing a mixture, β-starch is gelatinized to increase the binding strength and achieve uniform dispersion of the binder. However, since the particle size of starch powder is generally about 1 to 50 μm, there is a problem that the starch powder scatters to the surroundings during the kneading process, worsening the working environment. In addition, if the starch powder scatters to the surroundings, there is a problem that the amount of binder added increases, increasing production costs.

[0011] The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for producing molded coal that can suppress scattering of a binder to the surroundings when a binder is added to coal powder and kneaded. Another object of the present invention is to provide a method for producing molded coal and coke that can suppress scattering of a binder to the surroundings during production. [Means for solving the problem]

[0012] The means for solving the above problems are as follows. [1] A method for producing molded charcoal, comprising: a mixing step of mixing coal powder with powdered rice having a particle diameter of 100 μm or more and 200 μm or less to form a mixture; and a molding step of molding the mixture to produce molded charcoal. [2] The method for producing molded charcoal described in [1], wherein the content of the powdered rice in the kneaded mixture is 1.0 mass% or more and 3.0 mass% or less. [3] The method for producing molded charcoal described in [1] or [2], wherein the powdered rice is produced by grinding stockpiled rice. [4] A method for producing molded charcoal described in any one of [1] to [3], wherein the powdered rice is produced by grinding alpha rice, and in the kneading process, water steam is supplied to adjust the moisture content of the kneaded mixture to 11 mass% or more and 15 mass% or less. [5] A method for producing molded charcoal described in any one of [1] to [3], wherein the powdered rice is produced by grinding β rice, and in the kneading process, water 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] Molded coal comprising coal powder having a particle diameter of 3.0 mm or less at 80 mass% or more and powdered rice having a particle diameter of 100 μm or more and 200 μm or less. [7] The molded carbon described in [6], wherein the powdered rice content is 1.0% by mass or more and 3.0% by mass or less. [8] A method for producing coke, comprising charging the molded coal produced by the method for producing molded coal described in [1] or [2] into a coke oven and carbonizing it to produce coke. Effect of the Invention

[0013] According to the present invention, the binder is made of crushed rice containing powdered rice having a particle size of 100 μm to 200 μm, which suppresses the scattering of the binder and prevents the deterioration of the working environment. Furthermore, by suppressing the scattering of the binder, the amount of binder added is prevented from increasing, and the increase in production costs is also suppressed. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing a molded coal production facility in which the molded coal production method according to this embodiment can be carried out. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing an example of a kneader. [Diagram 3] FIG. 3 is a graph showing the relationship between the powdered rice content and the drop strength of molded charcoal. [Figure 4] FIG. 4 is a graph showing the relationship between the moisture content and the drop strength of the molded coal. [Diagram 5] FIG. 5 is a graph showing the relationship between the heating temperature and the drop strength of the briquettes. [Figure 6] FIG. 6 is a graph showing the relationship between the powdered rice content and the drop strength of molded charcoal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be specifically described below through the embodiments of the present invention. The following embodiments are preferred examples of the present invention, and the present invention is not limited to these embodiments.

[0016] Fig. 1 is a schematic diagram showing a molded charcoal manufacturing facility 26 in which the molded charcoal manufacturing method according to this embodiment can be implemented. In the molded charcoal manufacturing method according to this embodiment, as shown in Fig. 1, coal powder 10 and powdered rice 12 having a particle size of 100 μm or more and 200 μm or less are fed into a mixer 22 and mixed in the mixer 22 to produce a mixture 14. This process is the mixing process. The powdered rice having a particle size of 100 μm or more and 200 μm or less is powdered rice that is sieved under a sieve with a mesh size of 200 μm and over a sieve with a mesh size of 100 μm.

[0017] The coal powder 10 is made of fine coal, which is a raw material for the molded coal 18. In addition to caking coal, low-grade non- or slightly caking coal is used as the coal powder 10. The coal powder 10 may include, for example, fine coal generated in a coke oven and collected by a dust collector.

[0018] The smaller the particle size of the coal powder 10, the more the number of contact points with the powdered rice 12 that serves as a binder will increase, and the strength of the molded coal 18 produced will be improved. For this reason, the coal powder 10 preferably contains 80 mass % or more of coal powder with a particle size of 3.0 mm or less, and more preferably 90 mass % or more. Note that a particle size of 3.0 mm or less refers to a particle size that can be sieved through a sieve with a mesh size of 3.0 mm. When using coal powder that contains less than 80 mass % of coal powder with a particle size of 3.0 mm or less, the coal powder may be pulverized or mixed with another coal powder with a finer particle size to adjust the particle size within the above range.

[0019] In the method for producing molded charcoal according to this embodiment, powdered rice 12 having 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 having a particle size of 100 μm or more and 200 μm or less is produced by grinding raw rice with a grinder. The raw rice may be brown rice from which the rice bran has not been removed, or white rice from which the rice bran has been removed. The raw rice is not limited by the standard or place of origin as edible rice, and non-glutinous rice or glutinous rice may be used. The raw rice may contain starch in the center of the rice excluding the bran layer. The raw rice may contain 70% by mass or more of starch, and may also contain proteins, lipids, and vitamins.

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

[0021] The raw rice may contain β-starch, which is a natural crystalline structure, or may be converted to a gelatinized state (α-starch) by cooking or the like. For example, most stockpiled rice stored as disaster preparedness supplies is already in the α-starch state, and it is preferable to use stockpiled rice that has passed its expiration date as a disaster preparedness supply. 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 stockpiled rice that has passed its expiration date.

[0022] Powdered rice 12 having a particle diameter of 100 μm or more and 200 μm or less is used as a binder for producing molded charcoal 18. If the particle diameter of the powdered rice 12 is less than 100 μm, the powdered rice scatters around during the kneading process with the coal powder 10, deteriorating the working environment. If the powdered rice scatters around, the consumption of the powdered rice as a binder increases, increasing production costs. On the other hand, if the particle diameter of the powdered rice 12 exceeds 200 μm, the number of contact points between the coal powder 10 and the powdered rice 12 decreases, and the drop strength of the molded charcoal 16 decreases. For this reason, in the method for producing molded charcoal according to this embodiment, powdered rice 12 having a particle diameter of 100 μm or more and 200 μm or less is used. It is preferable that the particle diameter of the powdered rice 12 is 130 μm or more and 180 μm or less.

[0023] Most commercially available rice flours have an average particle size of about 30 μm or more and 50 μm or less, which does not satisfy the particle size required for powdered rice 12. In addition, most commercially available rice has a grain thickness of 1.7 mm or more, which does not satisfy the particle size required for powdered rice 12. For this reason, powdered rice 12 is produced by grinding raw material rice with a grinder.

[0024] As the pulverizer, a fine pulverizer capable of pulverizing raw materials of about 1 to 5 mm to 200 μm or less can be used. Any pulverizing principle can be applied to the pulverizer. As the pulverizer, a pulverizer that pulverizes raw material rice by utilizing forces such as compression force, impact force, shear force, and friction force may be used. For example, a roller mill that compresses and pulverizes raw material rice between a rotating roller and a table, a hammer mill that pulverizes raw material rice by applying impact to the raw material rice with a hammer rotating at high speed, a rotary mill that pulverizes raw material rice by filling the raw material rice in a rotating cylindrical container and rotating the cylindrical container. In addition, a household flour mill may be used as an inexpensive pulverizer. For example, a high-speed mill manufactured by LabNect Co., Ltd. may be used. As the pulverizer, a dry pulverizer is preferably used. A wet pulverizer is not preferable because the pulverized rice may aggregate, making it difficult to mix uniformly with the coal powder in the kneading process.

[0025] The pulverized rice obtained by pulverizing raw rice in a pulverizer is adjusted to powdered rice 12 having a particle size of 100 μm or more and 200 μm or less using a classification device such as a sieve. However, since it is difficult to adjust the particle size within the above range, the kneader 22 may contain rice flour with an average particle size of less than 100 μm and coarsely pulverized rice with an average particle size of more than 200 μm, in addition to 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 the powdered rice 12 to the total amount of rice is preferably 80 mass% or more, more preferably 90 mass% or more, and even more preferably 100 mass%.

[0026] Next, the kneading process will be described. The powdered rice 12 with the adjusted particle size is used as a binder, and the powdered rice 12 and the coal powder 10 are kneaded using a kneader 22. In the kneading process, the powdered rice 12 is preferably added to the coal powder 10 so that the content of the powdered rice 12 in the kneaded mixture 14 after kneading is 1.0 mass% or more and 3.0 mass% or less. If the content of the powdered rice 12 is less than 1.0 mass%, the drop strength of the molded coal 16 decreases, which is not preferable. On the other hand, even if the content of the powdered rice 12 exceeds 3.0 mass%, there is almost no increase in the drop strength of the molded coal 16, and the coal content decreases. However, when α rice is used as the raw rice, the dispersibility of the binder in the mixture is slightly lower than when β rice is used. For this reason, when α rice is used, the content of α rice is preferably 1.2 mass% or more and 3.0 mass% or less.

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

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

[0029] FIG. 2 is a cross-sectional schematic diagram showing an example of the mixer 22. The mixer 22 has a charging section 30, a discharge section 32, a rotating shaft 34, a paddle blade 36, and a screw blade 38. Coal powder 10 and powdered rice 12, which is a binder, are charged from the charging section 30 at a preset ratio. A paddle blade 36 rotated by a rotating shaft 34 is provided at the front stage (upstream side) of the mixer 22. The paddle blade 36 has a flat plate (paddle), and the coal powder 10 and the powdered rice 12 are mixed by the rotation of the flat plate. A screw blade 38 rotated by the rotating shaft 34 is provided at the rear stage (downstream side) of the mixer 22. The screw blade 38 has a propeller-shaped blade. The rotation of the propeller-shaped blade further mixes the mixture 14, the viscosity of which has increased in the process of mixing the coal powder 10 and the powdered rice 12, and transfers it to the downstream side of the mixer 22. The kneaded material 14 transferred to the downstream side of the kneader 22 is discharged from a discharge section 32 .

[0030] The kneader 22 has a plurality of steam outlets 40 for supplying heated steam to the mixture being kneaded. Heated steam is supplied from the steam outlets 40 to the coal powder 10 and the powdered rice 12. The kneader 22 may also be provided with a heating means (not shown) for heating the mixture. As the heating means, in addition to the heated steam supplied from the steam outlets 40, for example, microwave irradiation may be used for heating, or an electric heater or a gas combustion device may be provided around or inside the kneader 22 for heating.

[0031] When alpha rice is used as the raw material rice, kneading can be performed without applying external heating in the kneading process using the kneader 22. The starch contained in alpha rice is gelatinized (gelatinized). Even in powdered rice obtained by pulverizing alpha rice, the starch contained in the powdered rice remains in a gelatinized state. Therefore, in the kneading process, simply adjusting the moisture content to between 11% and 15% by mass increases the viscosity of the powdered rice 12, and a lumpy kneaded product 14 is produced. In this case, there is no need to heat the kneaded product 14 in the kneading process. When alpha rice is used as the raw material rice, the kneading time in the kneader 22 only needs to be 15 seconds or more. Because a binder that has already been gelatinized is used, a lumpy kneaded product 14 is produced even in a short kneading process.

[0032] On the other hand, when β rice is used as the raw material rice, it is preferable to supply steam in the kneading process by the kneader 22 to adjust the moisture content of the kneaded material 14 to 11 mass % or more and 15 mass % or less, and to heat the kneaded material 14 to 70°C or more. For example, in the kneader 22 shown in FIG. 2, it is preferable to knead in an unheated state in the front stage (upstream side), and knead while heating by blowing heated steam from the steam outlet 40 in the subsequent rear stage (downstream side). Kneading in an unheated state in the front stage of the kneader 22 is for uniformly mixing the powdered rice 12 with a particle diameter of 100 μm or more and 200 μm or less with the coal powder 10. Heating while supplying steam in the rear stage of the kneader 22 is for gelatinizing the β rice mixed with the coal powder 10 to increase the adhesive strength between the coal powder 10 and the powdered rice 12.

[0033] Even in this case, it is preferable to adjust the moisture content of the kneaded material 14 to 11% by mass or more and 15% by mass or less. If the moisture content of the kneaded material 14 is less than 11% by mass, the gelatinization of the β rice does not proceed sufficiently, and the adhesive strength between the coal powder 10 and the powdered rice 12 does not increase, which is not preferable. Also, if the moisture content of the kneaded material 14 exceeds 15% by mass, the adhesive strength between the coal powder 10 and the powdered rice 12 decreases, the strength of the molded charcoal decreases, and drying after the molded charcoal takes a long time, which is not preferable. Also, it is preferable to heat the mixture to 70°C or more in the kneading process. Since the gelatinization start temperature of starch is 60°C or more, the β rice can be sufficiently gelatinized by heating to 70°C or more. On the other hand, since increasing the heating temperature only increases the amount of thermal energy consumed, it is preferable to heat the mixture to 90°C or less in the kneading process.

[0034] When β rice is used as the raw material rice 11, the kneading time by the kneader 22 is preferably 150 seconds or more. This allows the coal powder 10 and the powdered rice 12, which serves as a binder, to be mixed uniformly, and allows 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. A double roll molding machine is a relatively simple and versatile device, and since it is easy to apply a compressive force to the powder, it can produce molded charcoal with high strength. However, the molding machine is not limited to a double roll molding machine, and any molding machine using roll compression, rolling, or extrusion methods may be used.

[0036] The shape of the molded coal 1 molded by the molding machine 24 is not particularly limited, and may be, for example, any of a pillow shape, a Masek shape, and an egg shape. These shapes have no corners, so powdering during handling can be suppressed compared to molded coal with corners. The size of the molded coal is preferably 15 mm or more and 50 mm or less.

[0037] The molded coal 16 produced as described above uses coal powder 10 in which 80 mass % or more of the coal powder has a particle size of 3.0 mm or less, and is thus molded coal in which powdered rice 12 having a particle size of 100 μm or more and 200 μm or less is dispersed in the coal powder having a particle size of 3.0 mm or less that constitutes the molded coal. Such molded coal has a high drop strength and is not easily pulverized during handling. Furthermore, since the molded coal 16 contains powdered rice 12 having a particle size of 100 μm or more and 200 μm or less, scattering during kneading can be suppressed more than when the molded coal 16 contains powdered rice 12 having a particle size of less than 100 μm and does not contain powdered rice 12 having a particle size of 100 μm or more and 200 μm or less.

[0038] The method for producing molded coal according to the present embodiment can produce molded coal with high drop strength, which can be prevented from being pulverized during handling during storage and transportation. Therefore, by charging the molded coal into a coke oven and carbonizing it, high-quality coke with high strength can be produced from inexpensive, low-grade coal powder. EXAMPLES

[0039] <Example 1> An example will be described in which raw material rice is ground into powdered rice using a grinder, and then classified to produce powdered rice with a specified particle size distribution, which is then mixed with coal powder and molded coal is produced from the mixture. β rice and α rice were used as the raw material rice. White rice was used as the β rice. Furthermore, white rice that was steamed and then rapidly dried with hot air was used as the α rice. For all raw material rice, the mass of particles with a particle size of 1.7 to 5.5 mm was 90 mass % or more of the total raw material rice. For the coal powder, coal in which the mass of particles with a particle size of less than 3 mm was 95 mass % of the total coal was used.

[0040] The grinder used was a rotary mill that fills a rotating cylindrical container with raw rice and grinds it by rotating the cylindrical container. In the invention example, the grain size of the powdered rice was adjusted to a range of 100 μm to 200 μm using a grinder and a classifier, and the average grain size was adjusted by adjusting the distribution of grain sizes. On the other hand, in the comparative example, the raw rice was ground so as to contain coarse grains with a grain size of more than 200 μm. The average grain size of the powdered rice used as the binder and the content of the powdered rice in the molded charcoal are shown in Table 1. The average grain size is the mass average grain size. The mass average grain size is the average grain size obtained by calculating the average grain size from the measured amount that the number of grains with a grain size Dp is present in wi [g].

[0041] In the kneading process, powdered rice made by grinding raw rice was added to the coal powder as a binder to produce a kneaded material. In the kneading process, for the material made of α rice, water vapor was supplied in a room temperature environment without heating to adjust the moisture content of the kneaded material to 13% by mass. On the other hand, for the material made of β rice, the temperature of the kneaded material was adjusted to 80°C and the moisture content was adjusted to 13% by mass.

[0042] In the molding process, a pressurized roll molding machine was used to apply a compressive force to the mixture kneaded in the kneader to produce a 46mm x 46mm x 38mm Masek-shaped molded charcoal. The drop strength of the molded charcoal thus produced was evaluated. That is, after the molded charcoal produced was naturally cured for 2 hours, 10 molded charcoal produced under the same manufacturing conditions were dropped from a height of 2m three times, and the ratio of the weight of the lump 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 more, the powdering of the molded charcoal during handling during storage and transportation can be suppressed, and the scattering of dust due to the powdering of the molded charcoal can be suppressed. For this reason, using a drop strength of 80% as the standard, molded charcoal with a drop strength of 80% or more was judged to pass, and molded charcoal with a drop strength of less than 80% was judged to fail. Table 1 shows the evaluation results of the drop strength.

[0043] [Table 1]

[0044] From Table 1, it can be seen that when powdered rice with a particle size of 100 μm or more and 200 μm or less is used as a binder, molded charcoal with a drop strength of 80% or more can be produced. When 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 molded charcoal with a drop strength of 80% or more cannot be produced. On the other hand, it was confirmed that the smaller the particle size of the powdered rice used in the kneading process, the higher the strength of the molded charcoal tends to be. However, when the particle size of the powdered rice used is less than 100 μm, the powdered rice scatters around when it is added in the kneading process, worsening the working environment. Furthermore, the scattering around increases the amount of powdered rice added to mix a specified amount of powdered rice, and the manufacturing cost of molded charcoal increases.

[0045] For example, when alpha rice is used as the raw rice and rice flour crushed to an average particle size of 55 μm is used as the binder, it is necessary to add 3.5% by mass of rice flour to the coal powder to obtain molded coal with a drop strength of 80%. In contrast, in the invention example shown in Table 1, molded coal with sufficient strength can be produced by simply adding about 1.5% by mass of powdered rice to the coal powder. In this way, it was confirmed that by using powdered rice with a particle size of 100 μm or more and 200 μm or less as a binder, molded coal with sufficient strength can be produced while suppressing deterioration of the working environment and increases in the manufacturing costs of molded coal.

[0046] <Example 2> Next, Example 2 will be described in which a binder was produced using white rice, which is β rice, as the raw rice, and molded charcoal was produced from the mixture kneaded with coal powder. The raw rice and coal powder used were the same as those used in Example 1. In Example 2, powdered rice pulverized by a pulverizer was classified by a classifier to prepare a binder with an average particle size of 140 μm to 160 μm and a ratio of powdered rice having a particle size of 100 μm to 200 μm being 100% by mass. In Example 2, molded charcoal was produced by changing the powdered rice content, moisture content, and heating temperature in the kneading process, and the drop strength of the produced molded charcoal was measured.

[0047] Fig. 3 is a graph showing the relationship between the powdered rice content and the drop strength of molded charcoal. The horizontal axis of Fig. 3 is the powdered rice content (mass%), and the vertical axis is the drop strength (%) of the molded charcoal. The molded charcoal for which the drop strength was measured in Fig. 3 was molded from a mixture heated at 80°C in the kneading process and adjusted to a moisture content of 13 mass%.

[0048] As shown in Figure 3, by increasing the content of powdered rice in the molded coal to 1.0 mass% or more, the drop strength of the molded coal was increased to 80% or more. From these results, it was confirmed that by increasing the content of powdered rice (β rice) with a particle size of 100 μm to 200 μm to 1.0 mass% or more, molded coal with sufficient drop strength can be produced. On the other hand, even if the content of powdered rice exceeded 2.0 mass%, the drop strength of the molded coal hardly increased at all.

[0049] Fig. 4 is a graph showing the relationship between moisture content and the drop strength of molded charcoal. The horizontal axis of Fig. 4 is the moisture content (mass%) of the mixture, and the vertical axis is the drop strength (%) of the molded charcoal. The molded charcoal for which the drop strength was measured in Fig. 4 was molded charcoal obtained by heating the mixture at 80°C in the mixing process and adjusting the powdered rice content to 1.5% by mass.

[0050] As shown in Fig. 4, the drop strength of the molded coal was 80% or more when the moisture content of the kneaded material was in the range of 11% by mass to 15% by mass. This result confirmed that molded coal with sufficient drop strength can be produced by setting the moisture content of the kneaded material to 11% by mass to 15% by mass.

[0051] Fig. 5 is a graph showing the relationship between heating temperature and the drop strength of molded coal. The horizontal axis of Fig. 5 is the heating temperature (°C) in the kneading process, and the vertical axis is the drop strength (%) of the molded coal. The molded coal for which the drop strength was measured in Fig. 5 is molded coal made by molding a mixture containing 1.5% powdered rice by mass and having a moisture content adjusted to 10 to 11% by mass.

[0052] As shown in Figure 5, by setting the heating temperature in the kneading process to 70°C or higher, the drop strength of the molded coal was increased to 80% or more. This result confirmed that by setting the heating temperature of the kneaded material to 70°C or higher, molded coal with sufficient drop strength can be produced.

[0053] <Example 3> Next, Example 3 will be described in which alpha rice was used as the raw rice to generate a binder, which was then mixed with coal powder to produce molded charcoal. The alpha rice used was steamed white rice that was rapidly dried with hot air. In Example 3, the alpha rice was crushed and classified to prepare a binder in which the ratio of powdered rice having a particle size of 100 μm or more and 200 μm or less was 100 mass %. In Example 3, molded charcoal was produced by changing the content of powdered rice in the mixing process, and the drop strength of the produced molded charcoal was measured.

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

[0055] As shown in Figure 6, by increasing the powdered rice content to 1.2 mass% or more, the drop strength of the molded coal was increased to 80% or more. From these results, it was confirmed that molded coal with sufficient drop strength can be produced by increasing the content of powdered rice (α rice) with a particle size of 100 μm to 200 μm to 1.2 mass% or more. It has also been confirmed that when α rice is used as the raw rice and heated to 50°C in the kneading process, the drop strength of the molded coal can be increased to 80% or more even if the powdered rice content is 1.0 mass%. [Explanation of symbols]

[0056] 10 Coal powder 12 Rice powder 14 Mixture 16 Molded coal 22 Kneading machine 24 Molding machine 26 Molded charcoal manufacturing equipment 30 Loading section 32 Discharge section 34 Rotational Axis 36 Paddle Blade 38 Screw blade 40 Steam outlet

Claims

1. a kneading step of kneading coal powder with powdered rice having a particle diameter of 100 μm or more and 200 μm or less to obtain a kneaded mixture; A molding step of molding the kneaded mixture to produce molded coal; The method for producing molded charcoal comprising the steps of:

2. The method for producing molded charcoal according to claim 1 , wherein the content of the powdered rice in the kneaded mixture 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 2, wherein the powdered rice is produced by grinding stockpiled rice.

4. The powdered rice is produced by grinding alpha rice, The method for producing molded coal according to claim 1 or 2, wherein in the kneading step, water vapor is supplied to adjust the moisture content of the kneaded mixture to 11% by mass or more and 15% by mass or less.

5. The powdered rice is produced by grinding alpha rice, The method for producing molded coal according to claim 3 , wherein in the kneading step, water vapor is supplied to adjust the moisture content of the kneaded mixture to 11% by mass or more and 15% by mass or less.

6. The powdered rice is produced by grinding β rice, 3. The method for producing molded charcoal according to claim 1, wherein in the kneading step, water vapor is supplied to adjust the moisture content of the kneaded mixture to 11% by mass or more and 15% by mass or less, and the kneaded mixture is heated to 70°C or more.

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

8. Coal powder having a particle size of 3.0 mm or less of 80 mass% or more; Powdered rice having 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 powdered rice content is 1.0% by mass or more and 3.0% by mass or less.

10. A method for producing coke, comprising charging the briquettes produced by the method for producing briquettes according to claim 1 or 2 into a coke oven and carbonizing the briquettes to produce coke.

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