Method for producing block-shaped molded article mainly composed of carbon

Abstract

Provided is a method for producing a high-density and high-strength briquette mainly composed of carbon from coal having insufficient caking properties or a high-concentration carbon-containing material derived from coal. A method for producing a briquette molded article mainly composed of carbon, the method comprising: a pulverizing step for pulverizing coal having a volatile content of 1-20 mass% on a dry basis to obtain pulverized coal having a maximum particle diameter of 300 [mu] m or less; and a hot pressing step in which the pulverized coal is press-molded in an oxygen-isolated environment at a temperature within the temperature range of 600-1250 DEG C to obtain a bulk molded article.

Description

Technical Field

[0001] The present invention relates to a method for producing a block-shaped molded product mainly composed of carbon. Background Art

[0002] Patent Document 1 discloses a method for producing a high-density carbon material. In this method, only a self-sintering carbonaceous powder is heated to 400-600°C under atmospheric pressure, and then the heated carbon material raw material is heated at a speed of 50-400 kg / cm while being kept in the above temperature range. 2 The molded article is produced by applying pressure of 1000 to 10000, and the obtained molded article is then fired and graphitized. It should be noted that the self-sintering carbonaceous powder refers to bulk mesophase, mesocarbon microbeads, petroleum-based or coal-based green coke.

[0003] Patent Document 2 discloses a method for estimating the thermal history of coal or coke. This method is characterized by estimating the maximum temperature reached during the thermal history of the coal or coke within a range of 300°C to less than 600°C based on the intensity of the baseline of a spectrum obtained through Raman spectroscopy.

[0004] Non-Patent Document 1 discloses the results of a study on coke strength (the strength of blast furnace shaped coke) based on an indirect tensile strength test method.

[0005] A method for producing coke is described in non-patent document 2. In this method, various types of coal (carbon content of 67.0 to 84.6 wt%-daf, natural logarithm of fluidity of 0 to 1.1) including non-stick coal are crushed to a particle size of less than 106 μm, or finely crushed to less than about 10 μm by ball milling, and then the crushed material is molded at a temperature of 240°C and a mechanical pressure of 128 MPa, and the molded material is further carbonized. In this method, a bulk density of 1.10 to 1.49 g / cm can be produced. 3 , and coke having a cold tensile strength of 1.6 to 35.1 MPa.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Publication No. 1-32162

[0009] Patent Document 2: Japanese Patent No. 5929075

[0010] Non-patent literature

[0011] Non-Patent Document 1: Study on Coke Strength Based on Indirect Tensile Strength Test Method (I), Fuel Association Journal, Vol. 54, No. 584, 1975, pp. 983-993, Miyagawa Masao et al. [Retrieved October 14, 2019], URL: https: / / www.jstage.jst.go.jp / article / jie1922 / 54 / 12 / 54_12_983 / _pdf

[0012] Non-patent literature 2: K.Uchida, S.Kudo, A.Mori, UPMAshik, K.Norinaga, Y.Dohi, K.Uebo and Ji.Hayashi: ISIJ International, 59(2019), P.1449. Summary of the Invention

[0013] Most solid carbon materials are made by molding coal or high-concentration carbon-containing materials made from coal into blocks. In this case, the block-shaped product requires a specified strength or bulk density depending on the application. Block-shaped products with carbon as the main body are manufactured by using liquid phase components such as coking coal or asphalt, which are adhesives, to bond or fuse the particles together to form blocks. However, in block molding using a liquid phase, the liquid phase components will decompose and produce gas. Therefore, sometimes foaming occurs in the block-shaped product, making the block-shaped product porous and reducing the bulk density, causing problems. In addition, the price of coking coal is higher than that of non-coking coal, and the price of asphalt, a binder, is even higher than that of coking coal, which also poses problems in this regard.

[0014] However, if coke or pitch is not used, conventional technologies cannot produce a block-shaped product, and even if a block-shaped product is produced, it may not have sufficient strength. In addition, there are also cases where it is desirable to effectively utilize coal that has lost its adhesive liquid phase component for some reason during the coal processing process, or coal that has been thermally treated (thermally treated coal).

[0015] In view of these circumstances, when manufacturing solid carbon materials, it is desired to provide a method for producing a high-density and high-strength carbon-based block-shaped molded product from coal with insufficient cohesiveness or a high-concentration carbon-containing material derived from coal.

[0016] The present invention has been made in view of the above-mentioned actual situation, and an object thereof is to provide a method for producing a high-density and high-strength carbon-based block-shaped product from coal having insufficient cohesiveness or a high-concentration carbon-containing material derived from coal.

[0017] The method for producing a block-shaped molded product according to the present invention to achieve the above-mentioned object is as follows.

[0018] [1] A method for producing a carbon-based bulk molded article, comprising:

[0019] a pulverizing step of pulverizing coal having a volatile matter content of 1% by mass or more and less than 20% by mass on a dry basis to obtain coal powder having a maximum particle size of 300 μm or less; and

[0020] In the hot pressing step, the pulverized coal is pressurized and molded in an oxygen-isolated environment at a temperature within a range of 600° C. to 1250° C. to obtain a block-shaped molded product.

[0021] [2] The method for producing a carbon-based block-shaped product according to [1] above, wherein the volatile matter of the coal is less than 13% by mass on a dry basis.

[0022] [3] The method for producing a carbon-based block-shaped product according to [1] or [2] above, wherein the coal is heat-treated coal.

[0023] [4] A method for manufacturing a carbon-based bulk molded object, comprising:

[0024] a heat treatment step of heat-treating the coal to obtain heat-treated coal having a volatile matter content of 1% by mass or more and less than 20% by mass on a dry basis;

[0025] a pulverizing step of pulverizing the heat-treated coal to obtain coal powder having a maximum particle size of less than 300 μm; and

[0026] In the hot pressing step, the pulverized coal is pressurized and molded in an oxygen-isolated environment at a temperature within a range of 600° C. to 1250° C. to obtain a block-shaped molded product.

[0027] [5] The method for producing a carbon-based block-shaped product according to [4] above, wherein the volatile matter of the heat-treated coal is less than 13% by mass on a dry basis.

[0028] [6] The method for producing a carbon-based bulk molded product according to any one of [3] to [5], wherein the heat treatment is performed at a first temperature of 500° C. to 1000° C. or less,

[0029] The press molding is performed at a temperature equal to or higher than the first temperature.

[0030] [7] The method for producing a carbon-based block-shaped molded product according to any one of [1] to [6] above, wherein the molding pressure of the press molding is 20 MPa or more.

[0031] [8] The method for producing a carbon-based block-shaped molded product according to any one of [1] to [7] above, wherein the heating is started after the pressurization is started in the pressurization.

[0032] [9] The method for producing a carbon-based block-shaped product according to any one of [1] to [8] above, wherein the coal is non-caking coal.

[0033] According to the present invention, a method for producing a high-density and high-strength carbon-based block-shaped product from coal having insufficient cohesiveness or a high-concentration carbon-containing material derived from coal can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a graph showing the relationship between the bulk density and volatile matter of the block-shaped molded product of Example 1.

[0035] Figure 2 This is a graph showing the relationship between the indirect tensile strength and the volatile matter of the block-shaped molded product of Example 1.

[0036] Figure 3 This is a graph showing the relationship between the indirect tensile strength of the block-shaped molded product of Example 2 and the heat treatment temperature.

[0037] Figure 4 This is a graph showing the relationship between the indirect tensile strength of the block-shaped molded product of Example 3 and the molding pressure.

[0038] Figure 5 This is a graph showing the relationship between the indirect tensile strength of the block-shaped molded product of Example 5 and the lower limit temperature of the molding temperature range. DETAILED DESCRIPTION

[0039] A method for producing a carbon-based bulk molded product according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0040] [First embodiment]

[0041] The method for producing a carbon-based block-shaped article according to this embodiment includes: a pulverization step of pulverizing coal having a volatile matter content of 1% to 20% by mass on a dry basis (DB) to produce coal powder having a maximum particle size of 300 μm or less; and a hot pressing step of pressurizing the coal powder in an oxygen-free environment at a temperature within the range of 600°C to 1250°C to produce a block-shaped article. Hereinafter, the volatile matter content of the coal is expressed in dry basis mass%.

[0042] In this production method, a high-density and high-strength carbon-based block-shaped product can be produced from coal having a volatile matter of 1% by mass or more and less than 20% by mass, that is, coal with insufficient cohesiveness, or a high-concentration carbon-containing material derived from coal.

[0043] Hereinafter, the carbon-based block molded article according to the present embodiment may be referred to simply as a block molded article. It should be noted that the term "carbon-based block molded article" refers to a block molded article having a carbon ratio of 70% to 100% by mass on a dry basis.

[0044] Specifically, in this manufacturing method, the block-shaped molded product is formed based on the solid-phase sintering phenomenon, rather than the liquid-phase sintering phenomenon in which the liquid-phase components that can become volatiles are used to bond or fuse the coal powder particles. Therefore, a high-strength block-shaped molded product can be obtained that can withstand the impact during transportation or the static load when it is stored in a processing site or hopper as a filling layer. In addition, a bulk density (apparent density) greater than 1.1 g / cm can be obtained. 3 High-density block molding (high-density block molding).

[0045] It should be noted that the bulk density of the block molded article in this embodiment is the value obtained by dividing the mass of the block molded article by the external volume of the block molded article (the sum of the volume of the solid portion of the target substance and the volume of open and closed pores). The mass of the block molded article is measured using an electronic balance. The external volume of the block molded article is the value obtained by measuring the diameter and height of the cylindrical block molded article with a vernier caliper and calculating it.

[0046] The strength of the block-shaped molded product in this embodiment refers to the cold indirect tensile strength measured by the method described in Non-Patent Document 1. Hereinafter, the indirect tensile strength measured by this method may be simply referred to as strength.

[0047] As the strength of the degree of static load when being able to withstand the impact during transportation or being made into a filling layer and being stored in a processing site or a hopper, it is necessary to have an intensity of more than 1MPa. In the following description, when the block molding has an intensity of more than 1MPa, the block molding is evaluated as high strength (high strength). Wherein, sometimes a block molding (i.e., coke) with an intensity of a degree that can be used in an existing blast furnace process is evaluated as a coke that can be used as high strength. It should be noted that the coke with an intensity that can generally be used in a blast furnace process refers to a coke with an intensity of more than 3MPa. In addition, when compared with an existing manufacturing method, when its intensity is relatively high compared to a block molding made of coal using the same degree of volatile matter, the block molding is evaluated as high strength.

[0048] Examples of coal with a volatile content of 1% by mass or more and less than 20% by mass include some bituminous coal, semi-anthracite coal, and anthracite. Coal with a volatile content of 1% by mass or more and less than 20% by mass has insufficient caking properties. Coal with a volatile content of 1% by mass or more and less than 20% by mass may be coal that has lost its volatile content for some reason during the coal processing process, or heat-treated coal obtained by heat-treating coal. That is, the concept of coal with a volatile content of 1% by mass or more and less than 20% by mass in this embodiment includes not only unprocessed coal, but also coal-based materials such as heat-treated coal that are derived from coal and contain carbon as a main component. In the following description of the first embodiment, simply referring to coal refers to coal with a volatile content of 1% by mass or more and less than 20% by mass.

[0049] The volatile content of coal is a value measured in accordance with "Coal and coke - Industrial analysis methods" (JIS M 8812: 2004) specified in Japanese Industrial Standards (JIS).

[0050] The pulverization step is a process for pulverizing coal to obtain coal powder with a maximum particle size of 300 μm or less. It should be noted that the particle size in this embodiment refers to the maximum particle size unless otherwise specified. When measured using a particle size distribution measuring device, the maximum particle size can be determined as follows.

[0051] In the present embodiment, the particle size and particle size distribution can be measured using a commercially available particle size distribution measuring device. In the present embodiment, an imaging particle size distribution measuring device "Morphologi 4" (hereinafter referred to as the particle size distribution measuring device) manufactured by Malvern Panalytical is used, and images of 55,000 to 74,000 particles are obtained using a microscope in which the device is equipped with a software that analyzes the image to obtain the equivalent circular particle size (projected area circle equivalent diameter), and the particle size and particle size distribution based on the equivalent circular particle size are used. That is, the particles contained in the mixed powder are accumulated from the smaller side of the particle size distribution measured by the particle size distribution measuring device to a particle size that reaches 95% as the maximum particle size (maximum value). The following descriptions of the particle size or particle size distribution, etc., refer to the values ​​measured by the above-mentioned particle size distribution measuring device.

[0052] If the pulverized coal contains coarse particles larger than 300 μm, these particles may remain in the molded block, reducing its strength. During the subsequent hot pressing step, smaller particle sizes promote solid-phase sintering, which causes the coal particles to bond together. Therefore, the remaining coarse particles can hinder particle bonding, sometimes leading to a decrease in strength. Furthermore, since defects are more likely to form around the coarse particles in the molded block, applying external forces can cause stress concentration, which can become a starting point for failure and, in some cases, reduce strength.

[0053] The particle size of the coal powder is preferably 100 μm or less. By making the particle size of the coal powder appropriately small, the physical structure in the block molding becomes dense and homogeneous, which helps to increase the strength of the block molding. It should be noted that the finer the particle size of the coal powder, the higher the strength of the block molding, so it is preferred. Therefore, there is no limit to the minimum particle size of the coal powder. However, from the perspective of productivity, even if it is desired to reduce the particle size of the coal powder, making the maximum particle size of the particles contained in the coal powder less than 20 μm leads to an increase in the fine grinding cost, and the performance of the block molding is effectively improved. Therefore, as long as the maximum particle size is 20 μm or more, a block molding with sufficient strength can be manufactured.

[0054] There are no particular limitations on the fine pulverization method or apparatus. As a coal fine pulverization apparatus, a medium mill such as a cutter mill, hammer mill, pin mill, jet mill, or ball mill can be used. The fine pulverization apparatus is not limited to an apparatus that performs only fine pulverization; for example, a pulverizer with a built-in classifier can be used.

[0055] The hot pressing step is a process of pressing the pulverized coal in an oxygen-isolated environment at a temperature within a temperature range of 600° C. to 1250° C. to form a block to obtain a block-shaped product.

[0056] During the hot pressing step, the pulverized coal is mechanically compressed to form a shape, known as pressure molding. Mechanical compression refers to compressing the pulverized coal using a physical wall such as a pestle and mortar, a mold (die), or compression rollers. Hereinafter, the pressure mechanically applied to the pulverized coal during the hot pressing step is referred to as molding pressure.

[0057] In the hot pressing step, the pulverized coal can be pressurized (i.e., hot pressed) at a temperature within the temperature range of 600°C to 1250°C. The hot pressing step can be, for example, performed by heating the pulverized coal to a temperature within the above-mentioned temperature range and then stopping heating, and performing press molding at a temperature within the above-mentioned temperature range. Alternatively, the hot pressing step can be performed by heating and raising the temperature of the pulverized coal while performing press molding at a temperature within the above-mentioned temperature range. In this case, in the entire process of heating and raising the temperature of the pulverized coal, pressurization can be performed only in a part of the process, or in the entire process. From the viewpoint of suppressing or preventing the temperature drop during press molding, it is preferred to perform the hot pressing step under heating, at least for the purpose of heat preservation, even if the temperature is not raised.

[0058] The hot pressing apparatus used to press-form the pulverized coal at a temperature within the range of 600°C to 1250°C is not particularly limited. The pulverized coal can be pressurized by containing the pulverized coal within a space enclosed by the aforementioned wall (e.g., within a mold undergoing hot pressing) and applying pressure through compression of the wall. The heat source used to heat the pulverized coal can be, for example, resistance heating, microwave heating, or high-frequency induction heating.

[0059] When pulverized coal is heated, it expands thermally. Consequently, the bulk density of the coal layer decreases. In contrast, heating the pulverized coal under pressure counteracts this thermal expansion, compressing the coal layer and suppressing the decrease in bulk density. This increases the number of contact points between particles and promotes solid-phase sintering. As a result, a high-density, high-strength block can be more efficiently produced.

[0060] The heating of the pulverized coal in the hot pressing step can be carried out via the above-mentioned wall body. In addition, the temperature range of the pulverized coal during pressurization in the hot pressing step is referred to as the forming temperature range. That is, the forming temperature range refers to the temperature range from the temperature of the pulverized coal at the start of pressurization (the lower limit temperature of the forming temperature range) to the temperature of the pulverized coal at the end of pressurization (the upper limit temperature of the forming temperature range) in the process of heating the pulverized coal. The upper limit temperature in the forming temperature range is 1250°C, which is the same as the upper limit temperature of the hot pressing step. The lower limit temperature in the forming temperature range is, for example, the temperature of the pulverized coal at the moment of being put into the mold for hot pressing.

[0061] During the hot pressing step, pulverized coal is heated to a temperature of 600°C or higher in an atmosphere that is deprived of oxygen. This allows the coal particles to bond and densify through solid-phase sintering. This results in a high-density, high-strength, block-shaped product. It should be noted that the bonding between the coal particles during solid-phase sintering generally occurs (or is observed) at temperatures above 600°C.

[0062] The atmosphere in the hot pressing step that blocks oxygen supply is, for example, an atmosphere in a space where an inert gas such as nitrogen flows while blocking the inflow of air (oxygen). The raw material burns and disappears in an atmosphere where oxygen is supplied.

[0063] The molding temperature range in the hot pressing step needs to include temperatures within the temperature range of 600°C to 1250°C. The molding temperature range preferably includes temperatures within the temperature range of 600°C to 1000°C. In other words, a portion or all of the molding temperature range must overlap with the temperature range of 600°C to 1250°C. In this way, a solid-phase sintering phenomenon can be generated to form coal powder into blocks. As described above, the solid-phase sintering phenomenon occurs above 600°C. The solid-phase sintering phenomenon occurs significantly at 600°C to 1250°C. Since carbonization is performed at a temperature of 600°C to 1250°C in the hot pressing step and serves as a carbonization treatment, there is no need to perform a separate carbonization treatment. Carbonization treatment can be further performed after the hot pressing step serving as a carbonization treatment.

[0064] When the carbonization treatment is performed after the hot pressing step, it is performed in an atmosphere that is isolated from oxygen supply, similar to the hot pressing step. The carbonization temperature as the temperature of the carbonization treatment can be 600°C or above. This is because the solid phase sintering phenomenon that causes the particles in the pulverized coal to bond with each other occurs above 600°C as described above. On the other hand, if the carbonization temperature exceeds 1250°C, the separation of impurity elements occurs in the block molding, and the strength decreases. When the carbonization temperature is below 1250°C, the higher the carbonization temperature, the higher the bulk density or strength of the block molding. In the case of coke for blast furnace use, high strength (3MPa or more, preferably 5MPa or more) is required for the block molding, so the carbonization temperature can be 900°C to 1250°C, more preferably 900°C to 1100°C. In addition, the carbonization temperature is preferably performed at a temperature higher than the temperature of the hot pressing step. For example, when the hot pressing step is performed at 700°C, by performing the carbonization treatment at a temperature higher than 700°C, the block molding can be shrunk to increase the density and further improve the strength. In addition, when the hot pressing step also serves as the carbonization treatment, the highest temperature reached in the hot pressing step is the carbonization temperature.

[0065] When the temperature of the pulverized coal is raised while performing pressure molding, the lower the lower limit temperature of the molding temperature range is, the better. In addition, when the temperature of the pulverized coal is raised while performing pressure molding, the higher the upper limit temperature of the molding temperature range is, the better. This is because when the temperature of the pulverized coal is raised while performing pressure molding, if the molding temperature range is wide, the reaction time can be extended. It should be noted that the lower limit temperature of the molding temperature range is the temperature (for example, room temperature) when pressurization is started in the hot pressing step. A part of the temperature range of the heating process can be used as the molding temperature range, but in order to expand the molding temperature range, pressurization can be started after the heating of the pulverized coal is started, for example, at the beginning of heating or immediately after heating.

[0066] The heating rate is preferably 30° C. / min or less. By setting the heating rate to 30° C. / min or less, temperature variations can be reduced and local strength reduction can be avoided.

[0067] The higher the forming pressure, the more contact points between the coal particles in the pulverized coal increase, which promotes the solid phase sintering phenomenon. Therefore, the higher the forming pressure, the higher the bulk density of the pulverized coal, and thus the higher the strength.

[0068] When the molding pressure is 20 MPa or more, the bulk density and strength (i.e., the quality of the bulk molded product) become stable. If the molding pressure is less than 20 MPa, a high-strength molded product may not be obtained. Therefore, the molding pressure is preferably 20 MPa or more. It should be noted that if the molding pressure is too high, the manufacturing cost may increase. A molding pressure of 300 MPa or less is sufficient.

[0069] If the volatile matter of the coal used as the raw material of the pulverized coal is less than 1% by mass, it is sometimes impossible to obtain a block-shaped molded product with an appropriate bulk density or strength from the pulverized coal. It is believed that in the solid-phase sintering phenomenon produced in the hot pressing step, the reaction of the coal or heat-treated coal used as the raw material undergoing aromatization or polycyclization becomes the driving force. Hydrogen is released in this reaction. In addition, on this basis, CO, methane, other hydrocarbons, etc. are released along with the decomposition of oxygen-containing functional groups or alkyl groups. That is, the amount of hydrogen, CO, methane, and other hydrocarbons released when the volatile matter of the raw material and the aromatization or polycyclization reaction that becomes the driving force of the solid-phase sintering phenomenon occur corresponds to each other, indicating the potential of the solid-phase sintering phenomenon. That is, if the volatile matter is less than 1% by mass, it is difficult to produce the solid-phase sintering phenomenon.

[0070] If the volatile matter is too high, such as exceeding 20% ​​by mass, the gas generated during heating (gas volatilized by the volatile matter, gas generated by the decomposition of the volatile matter) will expand, or the coal powder will melt and foam. Therefore, sometimes the compression of the coal powder by the hot pressing device during pressure molding is hindered, the coal powder cannot be fully pressurized, and the bulk density of the block molding decreases. In addition, the gas generated during heating may cause the internal pressure of the space surrounded by the wall of the hot pressing device, such as the bowl or mold, to exceed the pressure you want to apply to the coal powder. In such a case, there is also a risk of damage to the hot pressing device or the wall. In addition, the gas generated during heating is also likely to cause contamination of the wall. Therefore, the volatile matter of the coal is made less than 20% by mass.

[0071] In particular, to obtain agglomerated products with a strength of 3 MPa or greater, suitable for blast furnace coke, the volatile content of the coal should be set to 8% by mass or greater. Within the range of 1% by mass to less than 20% by mass, the higher the volatile content of the coal, the stronger the agglomerated products can be. By setting the volatile content of the coal to 8% by mass to less than 20% by mass, a method for producing low-cost coke with a strength suitable for use in existing blast furnace processes can be provided.

[0072] [Second embodiment]

[0073] In the first embodiment, a method for producing a carbon-based block-shaped article comprising a pulverizing step and a hot pressing step was described. The pulverizing step was described as a process for pulverizing coal having a volatile content of 1% to 20% by mass to produce coal powder with a maximum particle size of 300 μm or less. Furthermore, as examples of coal having a volatile content of 1% to 20% by mass, some bituminous coal, semi-anthracite coal, anthracite, coal that has lost its volatile content for some reason during coal processing, or heat-treated coal obtained by heat-treating the coal were described. The present embodiment differs from the first embodiment in that the method for producing a carbon-based block-shaped article further comprises a heat-treating step for heat-treating the coal to produce heat-treated coal having a volatile content of 1% to 20% by mass. The other aspects are the same. That is, in the second embodiment, the method for producing a carbon-based block-shaped article comprises a heat-treating step prior to the pulverizing step, wherein the heat-treating step pulverizes the heat-treated coal obtained in the heat-treating step. In the following description, descriptions of parts similar to those of the first embodiment will be omitted as appropriate.

[0074] The heat treatment step is a step for obtaining heat-treated coal to be supplied to the pulverization step. The heat treatment step is as follows: the coal is heated to 500°C or higher and 1000°C or lower in an oxygen-free environment.

[0075] The coal heat-treated in the heat treatment step (hereinafter referred to as raw coal) has a volatile content of, for example, 1 to 45% by mass. Examples of coals having such a volatile content include lignite, subbituminous coal, bituminous coal, semi-anthracite, and anthracite.

[0076] Raw coal with a high volatile content also tends to have high fluidity. On the other hand, raw coal with a low volatile content tends to have low fluidity. Thus, fluidity varies depending on the size of the volatile content, but in the method for manufacturing a block-shaped molded object involved in this embodiment, the fluidity of the raw coal can be arbitrarily selected. For example, if coking coal with high fluidity is used as raw coal and it is heat-treated at 500°C or above in an oxygen-isolated environment, the liquid phase components will undergo thermal decomposition and polycondensation. Then, among the decomposed or polycondensed components, the light components evaporate and the heavy components solidify and remain. The coking coal after heat treatment loses its liquid phase components, so its fluidity completely disappears. Therefore, coal showing any fluidity can be used.

[0077] In this embodiment, the common logarithm logMF of the maximum fluidity (MF: Maximum Fluidity of JIS M8801) of the raw coal is preferably 0.8 or greater. If such raw coal is used, the bulk density of the block molded product can sometimes be made higher than the bulk density of a block molded product produced by conventional techniques (for example, a block molded product produced by the method of Non-Patent Document 2. When the logMF of the raw coal is 0.8 or greater, the bulk density of such a block molded product tends to decrease as the logMF increases, as foaming due to volatile matter generated in the liquid phase is significant).

[0078] As described above, the heat treatment of the raw coal is performed by heating the raw coal to 500° C. or higher and 1000° C. or lower in an oxygen-blocked environment.

[0079] As the heat treatment temperature decreases, more volatile matter remains in the heat-treated coal, leading to more pronounced solid-phase sintering during the hot pressing step. Consequently, a high-density, high-strength block can be obtained.

[0080] If the heat treatment temperature is lower than 500°C, excessive amounts of volatile matter or tar remain in the heat-treated coal and pulverized coal. For example, if the volatile matter content of the heat-treated coal exceeds 20% by mass, as described in the first embodiment, the pulverized coal may melt, foam, or expand during the hot pressing step, resulting in a decrease in bulk density and damage or contamination of the hot pressing equipment. This is not preferred.

[0081] If the heat treatment temperature exceeds 1000° C., the volatile matter remaining in the heat-treated coal and pulverized coal may be less than 1% by mass. In this case, as described in the first embodiment, the solid phase sintering phenomenon is unlikely to occur.

[0082] The heat treatment of the raw coal can be performed in an atmosphere that is isolated from oxygen supply. For example, the heat treatment of the raw coal can be performed while the raw coal is contained in a container that forms a space that blocks the inflow of air while allowing the circulation of an inert gas. The heat treatment of the raw coal can be performed by heating the container containing the raw coal and utilizing heat conduction from the container. Specifically, the heat treatment of the raw coal can be performed by heating the container while the raw coal is contained, thereby heating the container to a temperature of 500°C to 1000°C.

[0083] Typically, since the reaction rate of the thermal decomposition reaction of the raw coal in the heat treatment is fast, the time required for the completion of the thermal decomposition reaction in the heat treatment is short. Therefore, the processing time required for heat treatment is more than 1 minute. The time for heat treatment (processing time of heat treatment, hereinafter referred to as heat treatment time) is preferably more than 10 minutes. Thus, there is no temperature difference between the temperature of the raw coal and the temperature of the container, and the raw coal can be heat-treated uniformly. In addition, the temperature of the raw coal as a whole can be reliably increased to the heat treatment temperature (i.e., uniformly heated) for heat treatment, which can suppress the uneven quality of the heat-treated coal.

[0084] The upper limit of the heat treatment time is not particularly limited, but if the heat treatment time is too long, the energy required for the heat treatment increases, and the cost increases, so it is not preferred. The heat treatment time is usually 60 minutes or less. It should be noted that the heat treatment time refers to the time from the moment the temperature of the raw coal reaches a prescribed heat treatment temperature of 500°C or more and 1000°C or less (hereinafter referred to as the first temperature) and the time the first temperature is maintained.

[0085] The heat treatment can be performed using a heating device such as an electric furnace, a rotary kiln, a fluidized bed furnace, a spiral heating furnace, a vertical furnace, or a cracking furnace.

[0086] The hot pressing step is the same as that of the first embodiment, but the following design can be further performed.

[0087] As described above, in this embodiment, the raw coal is heat-treated at a first temperature in the heat treatment step to produce heat-treated coal. Specifically, any thermal decomposition reactions that may occur in the heat-treated coal below the first temperature are completed, and further thermal decomposition reactions will not occur unless the heat is heated above the first temperature. Therefore, to initiate the thermal decomposition reaction that drives solid-phase sintering, the pulverized coal must be heated to a temperature above the first temperature. Therefore, in the hot pressing step, the molding temperature range can be set above the first temperature.

[0088] (Variation 1)

[0089] In the above embodiment, the coal pulverized in the pulverization step is coal having a volatile content of 1% to less than 20% by mass. Examples of coal having a volatile content of 1% to less than 20% by mass include some bituminous coal, semi-anthracite coal, anthracite, coal that has lost its volatile content for some reason during the coal processing process, or heat-treated coal obtained by heat-treating the coal. Furthermore, in the second embodiment, it was described that when the heat treatment step is performed at a temperature below the first temperature, the carbonization temperature during the heat forming in the hot pressing step can be set to a temperature above the first temperature. However, when producing agglomerated molded products using coal that has lost its volatile content for some reason during the coal processing process, for example, coal that has not been intentionally heat-treated as in the heat treatment step, the first temperature at which the coal was heat-treated may be unclear.

[0090] In this way, when the first temperature when the coal is heat-treated is unclear, for example, the thermal history inference method of coal or coke disclosed in Patent Document 2 can be used to infer the first temperature when the coal is heat-treated, and the molding temperature range in the hot pressing step can be determined based on the inferred first temperature.

[0091] (Variation 2)

[0092] In the above embodiment, the hot pressing step is performed to obtain a block-shaped molded product. The block-shaped molded product obtained in the hot pressing step can also be further graphitized to produce a graphite material. When producing a graphite material from the block-shaped product, after the hot pressing step, the graphitization treatment is preferably performed at a temperature of 2000°C or higher, more preferably 2200°C or higher, in an oxygen-free atmosphere.

[0093] Example

[0094] The following describes examples.

[0095] (Example 1)

[0096] As Example 1, raw material coal or thermally treated coal having various volatile contents was used to produce a block-shaped molded article by the production method according to the present embodiment and evaluated.

[0097] Various raw coals are pre-crushed to a particle size of 74 μm or less (200 mesh pass), and then heat-treated at different heat treatment temperatures within the range of 600°C to 900°C to obtain heat-treated coal (heat treatment step). In the case of raw coal with a high volatile content (for example, when the raw coal is coking coal), it is sometimes formed into a block shape by heat treatment. Therefore, in this embodiment, regardless of the type of raw coal used to produce the heat-treated coal, it is crushed to a particle size of 74 μm or less after heat treatment to obtain coal powder (crushing step). A portion of the raw coal (raw coal with a volatile content of less than 20% by mass) is not heat-treated and is directly crushed to produce coal powder. It should be noted that an ultracentrifugal crusher (manufacturer: Verder Scientific, model: ZM200) is used for any of the above-mentioned crushing processes.

[0098] The pulverized coal is further subjected to hot pressing (hot pressing step). First, 1.32 g of pulverized coal is filled in a casting mold (mold, diameter: 12 mm). Then, while applying a molding pressure (mechanical pressure) of 50 MPa under nitrogen flow, heating is performed from room temperature to 1000°C at a heating rate of 20°C / min. After the casting mold reaches 1000°C, it is maintained at 1000°C for 5 minutes. Thereafter, the temperature is lowered and the block-shaped molded products (1-1 to 1-15) involved in Example 1 are recovered.

[0099] The bulk density and indirect tensile strength of the above-mentioned block-shaped products were measured. It should be noted that the indirect tensile strength was measured as the cold indirect tensile strength using the method described in Non-Patent Document 1. The bulk density was calculated from the dimensions obtained by measuring the outer volume with a vernier caliper, and the mass was calculated using an electronic balance, as described above. Table 1 shows the heat treatment temperature of the coal used to produce each block-shaped product in Example 1, the volatile matter content after heat treatment, the bulk density of the block-shaped product, and the indirect tensile strength. Figure 1 Graph showing the relationship between the bulk density and volatile matter of the block-shaped molded product of Example 1 is shown in FIG. Figure 2 Graph showing the relationship between the indirect tensile strength and volatile matter of the block-shaped molded product of Example 1 is shown in FIG.

[0100] [Table 1]

[0101]

[0102] (Comparative Example 1)

[0103] As Comparative Example 1, raw material coal or thermally treated coal having various volatile contents was used to produce agglomerated molded products according to the coke production method described in Non-Patent Document 2 (conventional method), and the products were evaluated.

[0104] A casting mold (mold, diameter: 12 mm) was filled with 1.50 g of coal powder obtained in the same manner as in Example 1. A mechanical pressure of 100 MPa was then applied to obtain a molded product. The molded product was then heated in an electric furnace at a heating rate of 3°C / min until it reached 1000°C. After reaching 1000°C in the electric furnace, the temperature was maintained at 1000°C for 5 minutes. The temperature was then lowered, and the block-shaped molded products (R1-1 to R1-26) of Comparative Example 1 were recovered.

[0105] The bulk density and indirect tensile strength of the above-mentioned briquettes were measured in the same manner as in Example 1. Table 2 shows the heat treatment temperature of the coal used to produce each briquette in Comparative Example 1, the volatile matter after heat treatment, the bulk density and indirect tensile strength of the briquettes. Figure 1 In addition to the results of Example 1, a graph showing the relationship between the bulk density and volatile matter of the block-shaped molded product of Comparative Example 1 is also shown. Figure 2 Similarly, in addition to the results of Example 1, a graph showing the relationship between the indirect tensile strength and the volatile matter of the block-shaped molded product of Comparative Example 1 is also shown.

[0106] [Table 2]

[0107]

[0108] According to Tables 1, 2 and Figure 1 、 2 The results of Example 1 and Comparative Example 2 shown in FIG. 1 show that the block-shaped product of Example 1 produced using coal or thermally treated coal having a volatile matter content of less than 13% by mass has a higher bulk density and strength than the block-shaped product of Comparative Example 1 produced by the conventional method.

[0109] The bulk density of the block-shaped products involved in Example 1 is 1.1 g / cm 3 Above is high density.

[0110] In particular, when the volatile matter was less than 9% by mass, the block could not be formed in Comparative Example 1, but could be formed in Example 1. That is, the block formed in Example 1 had higher bulk density and strength than the block formed in Comparative Example 1.

[0111] When the volatile matter was 8% by mass or more, the block-shaped product of Example 1 achieved a strength sufficient to be used as high-strength coke.

[0112] When the volatile matter is 13% by mass or more, the block-shaped molded product of Example 1 is comparable to the block-shaped molded product of Comparative Example 1, and has high bulk density and strength.

[0113] So, according to Figure 1 、 2The results of Example 1 shown above clearly indicate that the method for producing a block-shaped molded product according to this embodiment can produce a block-shaped molded product using coal or thermally treated coal having a volatile matter content of at least less than 20% by mass.

[0114] Based on the above results, it can be seen that the method for manufacturing block-shaped molded products involved in this embodiment can manufacture high-density and high-strength carbon-based block-shaped molded products from coal with insufficient bonding properties, i.e., a volatile matter of more than 1 mass% and less than 20 mass%, or high-concentration carbon-containing materials derived from coal (such as heat-treated coal).

[0115] (Example 2)

[0116] In order to confirm the influence of the heat treatment temperature, a block-shaped molded product according to Example 2 was produced and evaluated as follows.

[0117] In Example 2, a block-shaped article was produced using coal subjected to a different heat treatment temperature, and its bulk density and indirect tensile strength were measured. Coal (1) (volatile matter: 10.0 mass%) and Coal (2) (volatile matter: 20.0 mass%) were used as the raw coals.

[0118] In the production of the block-shaped molded product of Example 2, the block-shaped molded products (2-1 to 2-12) involved in Example 2 were obtained in the same manner as in Example 1, except that the heat treatment temperature was changed to different levels within the range of 600°C to 1100°C to obtain heat-treated coal.

[0119] The bulk density and indirect tensile strength of the block molded product of Example 2 were measured in the same manner as in Example 1. Table 3 shows the type of coal used to produce each block molded product in Example 2, the heat treatment temperature, the volatile matter after heat treatment, the bulk density and indirect tensile strength of the block molded product. Figure 3 Graph 2 shows the relationship between the indirect tensile strength of the block-shaped molded product of Example 2 and the heat treatment temperature.

[0120] [Table 3]

[0121]

[0122] According to Table 3 and Figure 3It can be seen that as the heat treatment temperature becomes higher, the volatile matter decreases monotonically, and the strength of the block molding also decreases monotonically. In particular, when the heat treatment temperature is above 900°C, although block moldings are obtained, the strength drops significantly. For example, block moldings 2-5, 2-10 and 2-11 dropped by 1.0MPa. Furthermore, when the heat treatment temperature is 1100°C, the volatile matter is less than 1% by mass, and no block molding is obtained. When the heat treatment temperature is below 800°C, the block molding is high density and high strength. When the heat treatment temperature is greater than 800°C and is above 900°C, the heat-treated coal with volatile matter that cannot be block-molded by the prior art (refer to the case where the volatile matter is less than 9% by mass in Comparative Example 1) can be block-molded with a strength that can measure the strength. It can be said that a high-strength block molding is obtained relative to the block molding of the prior art. It should be noted that the bulk density and strength of the block-shaped molded product also depend on the amount of volatile matter in the heat-treated coal after heat treatment. Therefore, when the heat treatment temperature exceeds 1000°C, it is not impossible to immediately produce a block-shaped product with high density and high strength. However, regardless of the type of coal heat-treated, the amount of volatile matter decreases monotonically as the heat treatment temperature increases, reaching a value approximately close to 1% by mass or less than 1% by mass when the heat treatment temperature exceeds 1000°C. Therefore, it is considered that the heat treatment temperature is preferably 1000°C or less.

[0123] (Example 3)

[0124] In order to confirm the influence of the molding pressure, a block-shaped molded product according to Example 3 was produced and evaluated as follows.

[0125] In the manufacture of the block-shaped molded product of Example 3, coal (1) is used as raw coal. In addition, heat treatment is performed only at a heat treatment temperature of 600°C to obtain heat-treated coal, and the molding pressure is set to 10MPa, 20MPa, 35MPa and 50MPa. Except for this, the same procedure as in Example 1 is carried out to obtain the block-shaped molded products (3-1 to 3-4) involved in Example 3.

[0126] The bulk density and indirect tensile strength of the block molded product of Example 3 were measured in the same manner as in Example 1. Table 4 shows the molding pressure during production of each block molded product in Example 3, the bulk density of the block molded product, and the indirect tensile strength. Figure 4 Graph 2 shows the relationship between the indirect tensile strength and the molding pressure of the block-shaped molded product of Example 3. The volatile matter of the heat-treated coal in Example 3 (heat-treated coal (1)) was 8.2% by mass.

[0127] [Table 4]

[0128]

[0129] According to Table 4 and Figure 4 The graph shows that the molding pressure is preferably 20 MPa or higher. When the molding pressure is 20 MPa or higher, the block molded product has high density and high strength. When the molding pressure is less than 20 MPa (10 MPa), a block molded product is obtained, but the strength decreases by 1.0 MPa.

[0130] (Example 4)

[0131] In order to confirm the influence of the molding temperature range, a block-shaped molded product according to Example 4 was produced and evaluated as follows.

[0132] In the manufacture of the block-shaped molded product of Example 4, coal (1) is used as raw coal. In addition, heat treatment is performed only at a heat treatment temperature of 600°C to obtain heat-treated coal. In the hot pressing step, molding pressure is applied only within a specific temperature range of 200°C from room temperature to 1000°C during the heating process as the molding temperature range. Except for this, the same procedure as in Example 1 is carried out to obtain the block-shaped molded products (4-1 to 4-5) involved in Example 4.

[0133] The bulk density and indirect tensile strength of the block-shaped product of Example 4 were measured in the same manner as in Example 1. Table 5 shows the molding temperature range, bulk density, and indirect tensile strength of the block-shaped product in Example 4. It should be noted that the heat-treated coal in Example 4 (heat-treated coal (1)) had a volatile matter of 8.2% by mass, as shown in Example 3.

[0134] [Table 5]

[0135]

[0136] As shown in Table 5, it can be seen that when the molding temperature range does not include a temperature range of 600°C or higher, no block-shaped molded product can be obtained. Furthermore, it can be seen that when the molding temperature range includes a temperature within the temperature range of 600°C to 1000°C (when press molding is performed at a temperature within the temperature range of 600°C to 1000°C), a block-shaped molded product with high bulk density and high strength can be obtained.

[0137] (Example 5)

[0138] In order to confirm the influence of the molding temperature range, a block-shaped molded product according to Example 5 was produced and evaluated as follows.

[0139] In the manufacture of the block-shaped molded product of Example 5, in the hot pressing step, the lower limit temperature of the molding temperature range is set to 25°C, 200°C, 400°C, 600°C and 800°C, and the upper limit temperature of the molding temperature range is set to 1000°C (that is, only the lower limit temperature of the molding temperature range is changed) and molding pressure is applied. Otherwise, the same procedure as in Example 4 is carried out to obtain the block-shaped molded product (5-1 to 5-5) involved in Example 5.

[0140] The bulk density and indirect tensile strength of the block molded product of Example 5 were measured in the same manner as in Example 1. Table 6 shows the lower limit temperature of the molding temperature range in Example 5, the bulk density of the block molded product, and the indirect tensile strength. Figure 5 Graph 2 shows the relationship between the indirect tensile strength of the block-shaped molded product of Example 5 and the lower limit temperature of the molding temperature range.

[0141] [Table 6]

[0142]

[0143] As shown in Table 6 and Figure 5 As shown in Table 6, it can be seen that as the lower limit temperature decreases, the strength of the block molded product increases. Therefore, it can be concluded that to improve the strength of the block molded product, the lower limit of the molding temperature range should be as low as possible. Furthermore, as shown in Table 6, the bulk density of the block molded product increases as the lower limit temperature decreases. Therefore, it can be concluded that to increase the bulk density of the block molded product, the lower limit of the molding temperature range should be as low as possible.

[0144] Comprehensive observation of the results shown in Table 5 and Table 6 shows that when the molding temperature range includes a temperature included in the temperature range of 600°C to 1000°C (when press molding is performed at a temperature included in the temperature range of 600°C to 1000°C), a block-shaped molded product with high bulk density and high strength can be obtained. In addition, if the molding temperature range includes a temperature range of less than 600°C, the bulk density or strength of the block-shaped product is sometimes further improved, so it is preferred. In other words, it is preferred that a part of the molding temperature range overlaps with the temperature range above room temperature (25°C) and less than 600°C. A particularly preferred specific example is that, like the block-shaped product 5-1, the molding pressure is continuously applied from the start to the end of the heating of the hot press.

[0145] As described above, a method for producing high-density and high-strength carbon-based shaped blocks from insufficiently cohesive coal or high-concentration carbon-containing materials derived from coal can be provided. The shaped blocks produced by this production method can be strong enough to withstand impact during transportation or static loads when stored as a filling layer at a processing site or in a hopper. Furthermore, the shaped blocks can be strong enough to be used in existing blast furnace processes.

[0146] It should be noted that the configuration disclosed in the above-mentioned embodiment (including other embodiments, the same below) can be used in combination with the configuration disclosed in other embodiments as long as there is no contradiction. In addition, the embodiments disclosed in this specification are for illustration only, and the embodiments of the present invention are not limited to this and can be appropriately changed within the scope of the purpose of the present invention.

[0147] Industrial applicability

[0148] The present invention can be used in a method for producing a block-shaped molded product mainly composed of carbon.

Claims

1. A method for producing a carbon-based bulk molded object, comprising: a pulverizing step of pulverizing coal having a volatile matter content of 1% by mass or more and less than 20% by mass on a dry basis to obtain coal powder having a maximum particle size of 300 μm or less; as well as In the hot pressing step, the coal powder is pressed and molded at a temperature within a range of 600° C. to 1250° C. in an oxygen-isolated environment to obtain a block-shaped molded product.

2. The method for producing a carbon-based bulk molded product according to claim 1, wherein: The volatile matter of the coal is less than 13% by mass on a dry basis.

3. The method for producing a carbon-based bulk molded product according to claim 1, wherein: The coal is heat-treated coal.

4. A method for producing a carbon-based bulk molded object, comprising: a heat treatment step of heat-treating the coal to obtain heat-treated coal having a volatile matter content of 1% by mass or more and less than 20% by mass on a dry basis; a pulverizing step of pulverizing the heat-treated coal to obtain coal powder with a maximum particle size of less than 300 μm; as well as In the hot pressing step, the coal powder is pressed and molded at a temperature within a range of 600° C. to 1250° C. in an oxygen-isolated environment to obtain a block-shaped molded product.

5. The method for producing a carbon-based bulk molded product according to claim 4, wherein: The volatile matter of the heat-treated coal is less than 13% by mass on a dry basis.

6. The method for producing a carbon-based bulk molded product according to any one of claims 3 to 5, wherein: The heat treatment is performed at a first temperature of 500° C. or higher and 1000° C. or lower. The press molding is performed at a temperature above the first temperature.

7. The method for producing a carbon-based bulk molded product according to any one of claims 1 to 6, wherein: The molding pressure of the press molding is 20 MPa or more.

8. The method for producing a carbon-based bulk molded product according to any one of claims 1 to 7, wherein: The press molding starts heating after the pressurization starts.

9. The method for producing a carbon-based bulk molded product according to any one of claims 1 to 8, wherein: The coal is non-caking coal.

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