Solid fuel and method for producing same

Abstract

This solid fuel comprises: a biomass carbonized material having at least 74 mass% of fixed carbon on an anhydrous ash-free basis; and an inorganic binder having a CaO content of at least 50 mass% in a dry state.

Description

Solid fuel and method for manufacturing the same

[0001] This disclosure relates to solid fuel and a method for producing the same. This application claims priority under Japanese Patent Application No. 2024-199298, filed in Japan on November 14, 2024, the contents of which are incorporated herein by reference.

[0002] Currently, in order to reduce carbon dioxide emissions, technologies are being developed to use biomass (biological resources) instead of fossil fuels. When biomass is used as fuel, carbon dioxide (CO2) is emitted, just like with fossil fuels. ２ Although carbon dioxide is emitted, the photosynthesis of plants, which are the raw materials for biomass, absorbs carbon dioxide, thus reducing overall carbon dioxide emissions.

[0003] Patent Document 1 discloses a technology using biomass in which a molded product with a crushing strength of 50 kg or more is obtained by adding a binder to powdered coke, mixing, and molding. In this case, powdered coke, which is harder than coal, is used as the raw material, and the average particle size of the powdered coke is set to 40 to 1000 μm, thereby disclosing a technology for producing a carbon-containing molded product with a crushing strength of 50 kg or more.

[0004] Japanese Patent Application Publication No. 2006-57082

[0005] Patent Document 1 states that when carbon-containing molded products are used as fuel, organic binders are preferred. However, organic binders are generally expensive and it is difficult to maintain their strength in high-temperature environments. Therefore, this disclosure provides a solid fuel that has sufficient strength in high-temperature environments and a method for manufacturing the same.

[0006] The solid fuel of this disclosure comprises a biomass char with a fixed carbon content of 74% by mass or more on an anhydrous, ash-free basis, and an inorganic binder with a CaO content of 50% by mass or more in a dry state.

[0007] The method for producing solid fuel according to this disclosure comprises a step of kneading and molding a molding raw material containing a biomass char with a fixed carbon content of 74% by mass or more on an anhydrous, ash-free basis, an inorganic binder with a CaO content of 50% by mass or more in a dry state, and water.

[0008] According to each of the above embodiments of the present invention, it is possible to provide a solid fuel having sufficient strength in a high-temperature environment and a method for producing the same.

[0009] This is a diagram illustrating the method for measuring particle strength. This is a diagram illustrating the method for measuring hot strength and cold strength.

[0010] The following describes the solid fuel and the method for manufacturing the solid fuel according to the embodiment.

[0011] <Solid Fuel> The solid fuel according to this embodiment comprises a biomass char with a fixed carbon content of 74% by mass or more on an anhydrous, ash-free basis, and an inorganic binder with a CaO content of 50% by mass or more in a dry state.

[0012] (Biomass Carbon) In this specification, biomass refers to organic resources of biological origin, excluding fossil resources. Examples of biomass include thinned wood, pruned branches, waste wood, bark chips, other wood, bamboo, grass, coconut shells, palm oil residue, vegetables, fruits, food waste, sludge, and other waste materials. Coconut shells are preferred as biomass because they can improve the particle strength of the biomass carbon. Examples of coconuts used as raw materials for coconut shells include palm oil palm, giant palm, and coconut palm. Biomass carbon can be obtained by dry distillation of such biomass.

[0013] The fixed carbon content of the biomass char in this embodiment is 74% by mass or more on an anhydrous, ash-free basis. Here, the anhydrous, ash-free basis refers to the base of the analytical value under the assumption that there is no moisture or ash content, and ash content refers to the proportion of inorganic substances remaining when the sample is heated and ashed under specified conditions. A fixed carbon content of 74% by mass or more in the biomass char ensures that the strength of the biomass char can be sufficiently maintained even in high-temperature environments. Preferably, the fixed carbon content of the biomass char is 77% by mass or more. More preferably, the fixed carbon content of the biomass char is 80% by mass or more. Even more preferably, the fixed carbon content of the biomass char is 85% by mass or more. Particularly preferably, the fixed carbon content of the biomass char is 90% by mass or more. There is no particular upper limit to the fixed carbon content of the biomass char, but for example, it is 99% by mass.

[0014] The fixed carbon content of anhydrous, ashless biomass char can be determined by converting the anhydrous fixed carbon value, measured in accordance with JIS M 8812:2006 "Coal and coke - Industrial analytical methods" "8. Method for calculating fixed carbon mass fraction (%)", to an anhydrous, ashless value.

[0015] The particle strength of the biomass char is 10.0 N / mm². ２ Preferably, the particle strength of the biomass char is 15.0 N / mm². ２ It is more preferable that the above conditions are met. The particle strength of the biomass char is 20.0 N / mm². ２ It is even more preferable that the particle strength of the biomass char is 10.0 N / mm². ２ This allows for a further improvement in the hot strength of biomass char.

[0016] The particle strength of biomass char can be measured in accordance with JIS Z 8841, except for the sample used for measurement. The testing machine used for measuring particle strength should have a parallel plane for the compression surface of the loading section, a sufficiently hard surface that does not deform, a smooth surface, and a movable pressure plate that can move at a constant speed, as shown in Figure 1. The measurement sample should be placed approximately in the center of the fixed compression surface of the testing machine, as shown in Figure 1. One biomass char should be placed at the position. The measurement after sample placement should be carried out according to the method described in JIS Z 8841.

[0017] The particle size of the biomass char is preferably 10 mm or less. It is more preferably 2.0 mm or less. Even more preferably 1.0 mm or less. If the particle size of the biomass char becomes too large, the adhesion between the particles may decrease, leading to a decrease in strength.

[0018] The particle size of the biomass char is preferably 0.4 mm or larger. It is more preferably 0.5 mm or larger. Even more preferably 0.6 mm or larger. If the particle size becomes too small, the contact area between the biomass char particles increases too much, which may reduce the strength.

[0019] The particle size of biomass char can be measured using a sieve. When sieved using a sieve with a mesh size of 2 mm, the particle size below the sieve is 2 mm or less.

[0020] The biomass char content in solid fuel is preferably 50% by mass or more of the total mass of the solid fuel. A biomass char content of 60% by mass is more preferable. A biomass char content of 65% by mass or more is even more preferable. By increasing the biomass char content, the calorific value of the solid fuel can be sufficiently increased.

[0021] The biomass char content in solid fuel is preferably 90% by mass or less of the total mass of the solid fuel. More preferably, the biomass char content is 85% by mass or less. Even more preferably, the biomass char content is 80% by mass or less. Particularly preferably, the biomass char content is 75% by mass or less. Such solid fuel can have even higher strength in high-temperature environments.

[0022] (Inorganic Binder) An inorganic binder is an inorganic substance that has the function of binding together particles of biomass char. In a dry state, the CaO content of the inorganic binder is 50% by mass or more of the total mass of the inorganic binder. In a dry state, the CaO content of the inorganic binder may be 55% by mass or more, or 60% by mass or more. Such an inorganic binder can reduce the melting point of the slag when used as solid fuel in a gasification melting furnace or a cupola furnace. In these facilities, limestone is sometimes used as an auxiliary material, but some or all of the limestone can be replaced by CaO from the inorganic binder. Here, a dry state refers to a state in which the object is dried at a temperature of 120 to 200°C until it reaches a constant mass, and the free water contained inside the object is removed.

[0023] The inorganic binder may contain Portland cement as defined in JIS R 5210:2009. Such solid fuels can have sufficiently high strength in high-temperature environments while significantly reducing manufacturing costs. Examples of Portland cement include ordinary Portland cement, rapid-hardening Portland cement, ultra-rapid-hardening Portland cement, moderate-heat Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement. The CaO content in Portland cement can be measured in accordance with the "Chemical Analysis Method for Cemetery" in JIS R 5202:2010. By including Portland cement in the inorganic binder, the hot strength of the solid fuel can be sufficiently increased.

[0024] The inorganic binder may contain components other than Portland cement (other inorganic substances). The inorganic binder does not contain water (except for hydration water and crystal water). The other inorganic substances are not particularly limited as long as they are inorganic substances, and examples include clay and sodium silicate. Examples of clay include bentonite (montmorillonite) and kaolin. If the inorganic binder contains multiple types of components, it is sufficient that the CaO content of the inorganic binder as a whole is within the range described above. If the inorganic binder contains components other than Portland cement, it can be measured in accordance with the Inorganic Element Measurement Method, Book 2, issued by the Ministry of the Environment.

[0025] In the solid fuel according to this embodiment, the inorganic binder content is preferably 10% by mass or more of the total mass of the solid fuel. More preferably, the inorganic binder content is 15% by mass or more. Even more preferably, the inorganic binder content is 20% by mass or more. Particularly preferably, the inorganic binder content is 25% by mass or more. If the inorganic binder content is within the above range, the strength of the solid fuel in a high-temperature environment can be improved.

[0026] In this embodiment, the inorganic binder content in the solid fuel is preferably 45% by mass or less of the total mass of the solid fuel. More preferably, the inorganic binder content is 40% by mass or less. Even more preferably, the inorganic binder content is 35% by mass or less. By lowering the inorganic binder content and increasing the biomass char content, the calorific value of the solid fuel according to this embodiment can be increased.

[0027] (Optional Components) The solid fuel may contain components other than biomass char and inorganic binders (optional components). Examples of such components include powdered coke and organic binders. By including powdered coke in the solid fuel, the powdered coke can be effectively utilized as a heat source. Examples of organic binders include polyvinyl alcohol, carboxymethylcellulose, and starch. The optional component preferably contains at least one selected from the group consisting of carboxymethylcellulose, polyvinyl alcohol, starch, and sodium silicate. By including the above components, the cold strength of the solid fuel (molded body) can be increased. This improves the handling properties immediately after molding.

[0028] In this embodiment, the content of optional components in the solid fuel is preferably 10% by mass or less of the total mass of the solid fuel. More preferably, the content of optional components is 8% by mass or less. Even more preferably, the content of optional components is 5% by mass or less. Since optional components do not need to be included, the lower limit is 0% by mass.

[0029] (Size of solid fuel) Solid fuel is a molded body obtained by compression molding. There are no restrictions on the size of individual molded bodies; for example, 1 to 800 cm². ３ , 3-600cm ３ , or 50-200 cm ３ This is acceptable. When solid fuel of this size is used as fuel for gasification melting furnaces and cupolas, it can sufficiently stabilize the combustion state inside the furnace. The shape of the solid fuel is not particularly limited. The shape of the solid fuel may be, for example, cylindrical.

[0030] (Hot Strength of Solid Fuel) The hot strength of the solid fuel according to this embodiment is preferably 300 N or more. The hot strength of the solid fuel is more preferably 800 N or more. The hot strength of the solid fuel is preferably 1000 N or more. The hot strength of the solid fuel is more preferably 2500 N or more. The hot strength of the solid fuel is particularly preferably 8000 N or more. By having the hot strength of the solid fuel within the above range, the strength of the solid fuel in a high-temperature environment can be increased. For example, if the solid fuel according to this embodiment is used as a solid fuel for a gasification melting furnace and a cupola, the combustion state inside the furnace can be made sufficiently stable.

[0031] The hot and cold strengths described herein are measured by the following procedure. The solid fuel is heated in an electric furnace in air at 1000°C for 30 minutes. After that, it is cooled to room temperature (approximately 20°C) in a nitrogen atmosphere. If the solid fuel is cylindrical, after cooling, as shown in Figure 2, the solid fuel (sample 10) is placed on the measuring stand 20 and a load is applied in the direction of the arrow (radial direction). The load at which a crack or fracture occurs in the sample 10 is defined as the hot strength (N). Solid fuels with high hot strength have sufficiently high strength in high-temperature environments. Alternatively, using another sample 10, without heating in an electric furnace, a load is applied as shown in Figure 2, and the load at which a crack or fracture occurs in the sample 10 is defined as the cold strength (N).

[0032] Since the solid fuel according to this embodiment contains biomass char with a predetermined amount of fixed carbon, it is possible to reduce the consumption of fossil fuels and thus reduce carbon dioxide emissions. By using it as fuel for gasification and melting furnaces and cupolas, the melting point of the slag can be adjusted. In addition, the amount of limestone used as an auxiliary material can be reduced.

[0033] <Method for Manufacturing Solid Fuel> The method for manufacturing solid fuel according to this embodiment comprises a carbonization step, a crushing step, a molding step, and a curing step. Furthermore, this manufacturing method may also include a drying step. Each of these steps will be described below. The solid fuel obtained by this manufacturing method may be the solid fuel described in <Solid Fuel> in the above embodiment. If the solid fuel obtained by this manufacturing method is the solid fuel described in <Solid Fuel> in the above embodiment, the solid fuel described in this <Method for Manufacturing Solid Fuel> will have the same characteristics as the solid fuel described in <Solid Fuel>.

[0034] (Carbonization Process) The carbonization process is a process in which the above biomass is carbonized by carbonization to obtain biomass char with fixed carbon content of 74% by mass or more on an anhydrous, ash-free basis. In the carbonization process, the biomass may be heated to a carbonization temperature of 200°C or higher in an oxygen-free atmosphere (oxygen concentration of 0.5% by volume or less). An example of a carbonization temperature is 200 to 900°C, but the carbonization temperature may be determined from various perspectives. In the carbonization process, the biomass may be heated to 250°C or higher, or to 320°C or higher. The ease with which biomass carbonization proceeds varies depending on the tree species and part of the tree. However, by heating the biomass to 250°C or higher for carbonization, or to 320°C or higher for carbonization, carbonization can be carried out stably and smoothly regardless of the tree species and part of the tree of the biomass. Thus, the lower limit of the carbonization temperature may be 200°C, 250°C, or 320°C. On the other hand, from the viewpoint of increasing the yield of carbon material, the biomass may be heated to 900°C or below, or to 700°C or below, during the carbonization process. The upper limit of the carbonization temperature may be 900°C or 700°C.

[0035] In the carbonization process, an example of the heating time to the above carbonization temperature range is 20 minutes or more and 3 hours or less. From the viewpoint of sufficiently carbonizing the biomass, the heating time to the above carbonization temperature range may be 20 minutes or more, or 30 minutes or more. The lower limit of the heating time to the above carbonization temperature range may be 20 minutes or 30 minutes. From the viewpoint of improving the productivity of biomass carbon, the heating time to the above carbonization temperature range may be 3 hours or less, or 2 hours or less. The upper limit of the heating time to the above carbonization temperature range may be 3 hours or 2 hours. By changing the carbonization temperature and carbonization time, the fixed carbon of the biomass carbon can be adjusted.

[0036] (Grinding Process) The grinding process is a process of grinding the biomass char. The particle size of the biomass char is adjusted in the grinding process. Grinding may be carried out using a grinding mill, for example, but is not limited to this method. The particle size of the biomass char may be adjusted to the range described above in <Solid Fuels>. Grinding can be carried out smoothly by performing the grinding process after the carbonization process.

[0037] (Molding Process) The molding process is a process of kneading the molding raw materials to form the product. The molding process includes crushed biomass char, an inorganic binder having a CaO content of 50% by mass or more in a dry state, and water. In the molding process, in addition to these biomass char, inorganic binder, and water, other optional components are added and kneaded to prepare the molding raw materials. Examples of optional components include powdered coke and organic binders. In the molding raw materials, the mass ratio of water to inorganic binder (water / inorganic binder) may be 0.5 or more, 0.7 or more, or 1.0 or more. This makes it possible to sufficiently increase the strength of the solid fuel. From a similar viewpoint, the mass ratio of water to inorganic binder (water / inorganic binder) may be 3.0 or less, 2.5 or less, or 2.0 or less. From a similar viewpoint, it is preferable that the mass ratio of water to the total of biomass char and inorganic binder (water / (biomass char + inorganic binder)) is 15% or more. It is more preferable that the mass ratio of water to the total of biomass char and inorganic binder be 20% or more. It is even more preferable that the mass ratio of water to the total of biomass char and inorganic binder be 25% by mass or more. It is preferable that the mass ratio of water to the total of biomass char and inorganic binder be 65% or less. It is more preferable that the mass ratio of water to the total of biomass char and inorganic binder be 60% or less. It is even more preferable that the mass ratio of water to the total of biomass char and inorganic binder be 55% or less. This allows the inorganic binder to harden sufficiently even if the biomass char absorbs some of the water. After kneading, the molding raw material is molded to obtain a molded body. For molding, a conventional molding machine such as a uniaxial pressure molding machine or a briquette roll can be used, but this method is not limited to this method.

[0038] (Curing Process) The curing process is the process of curing the molded body. In the curing process, the inorganic binder contained in the molded body is hardened to obtain solid fuel. Therefore, appropriate curing conditions (e.g., curing time and curing temperature) should be selected according to the type of inorganic binder. For example, if the inorganic binder is Portland cement, curing may be carried out by holding it at 20°C or higher for 4 hours or more, 6 hours or more, 10 hours or more, or 24 hours or more.

[0039] (Drying Process) After the curing process, a drying process may be performed. The drying may be carried out, for example, in an atmosphere at a temperature higher than that of the curing process, but is not limited to this method. By drying, the moisture contained in the inorganic binder can be reduced, and a solid fuel having higher strength can be obtained.

[0040] The solid fuel obtained by the manufacturing method of the present embodiment has sufficient strength in a high-temperature environment. The use of the solid fuel of the present disclosure is not limited. The solid fuel of the present disclosure is useful, for example, as a fuel for a gasification melting furnace or a cupola. When used in a gasification melting furnace, the solid fuel of the present disclosure can be used in place of coke. In this case, the melting point of the slag can be adjusted. Also, the amount of limestone used as an auxiliary material can be reduced. Further, since biomass carbide is used, the consumption of fossil fuels can be reduced and the carbon dioxide emission can be reduced.

[0041] Note that the technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. In addition, within the scope not departing from the spirit of the present invention, it is possible to appropriately replace the components in the above embodiment with well-known components.

[0042] (Appended Note) The solid fuel and the solid fuel according to the above embodiment are grasped, for example, as follows. (1) The solid fuel according to Aspect 1 of the present disclosure includes a biomass carbide having a fixed carbon of 74% by mass or more on an ash-free and moisture-free basis, and an inorganic binder having a CaO content of 50% by mass or more in a dry state.

[0043] According to the above configuration, the solid fuel has sufficient strength in a high-temperature environment.

[0044] (2) The solid fuel according to Aspect 2 of the present disclosure is the solid fuel of (1), and the particle strength of the biomass carbide is 10.0 N / mm ２ or more.

[0045] According to the above aspect, the strength of the solid fuel in a high-temperature environment can be further improved.

[0046] (3) The solid fuel according to embodiment 3 of the present disclosure is the solid fuel of (1) or (2), wherein the fixed carbon is 77% by mass or more on an anhydrous, ashless basis.

[0047] According to the above embodiment, the strength of the solid fuel in a high-temperature environment can be further improved.

[0048] (4) The solid fuel according to embodiment 4 of the present disclosure is any one of the solid fuels (1) to (3) wherein the biomass char content is 50% by mass or more and the inorganic binder content is 10% by mass or more.

[0049] According to the above embodiment, the calorific value of the solid fuel can be sufficiently increased. Furthermore, the strength of the solid fuel in high-temperature environments can be improved.

[0050] (5) The solid fuel according to embodiment 5 of the present disclosure is any one of the solid fuels (1) to (4) which has a hot strength of 1000 N or more, measured after being heated in air at 1000°C for 30 minutes and then cooled.

[0051] According to the above embodiment, the combustion state inside the furnace can be made sufficiently stable.

[0052] (6) A solid fuel according to embodiment 6 of the present disclosure is any one of the solid fuels (1) to (5), wherein the inorganic binder comprises Portland cement.

[0053] According to the above embodiment, the hot strength of the solid fuel can be sufficiently increased.

[0054] (7) The solid fuel according to embodiment 7 of the present disclosure is any one of the solid fuels (1) to (6) wherein the particle size of the biomass char is 10.0 mm or less.

[0055] According to the above embodiment, the strength of the solid fuel can be maintained.

[0056] (8) A solid fuel according to embodiment 8 of the present disclosure is any one of the solid fuels (1) to (7), further comprising at least one selected from the group consisting of carboxymethylcellulose, polyvinyl alcohol, starch, and sodium silicate.

[0057] According to the above embodiment, the cold strength of the solid fuel (molded body) can be increased.

[0058] (9) A solid fuel according to embodiment 9 of the present disclosure is any one of the solid fuels (1) to (8), further comprising powdered coke.

[0059] According to the above embodiment, powdered coke can be effectively utilized as a heat source.

[0060] (10) A method for producing solid fuel according to embodiment 10 of the present disclosure comprises a step of kneading and molding a molding raw material which includes a biomass char with a fixed carbon content of 74% by mass or more on an anhydrous, ashless basis, an inorganic binder with a CaO content of 50% by mass or more in a dry state, and water.

[0061] According to the above embodiment, a solid fuel having sufficient strength in a high-temperature environment can be manufactured.

[0062] (11) A solid fuel according to aspect 11 of the present disclosure is a method for producing the solid fuel of (10), wherein the particle strength of the biomass char is 1000.0 N / mm ２ The method for producing solid fuel according to claim 11, as described above.

[0063] According to the above embodiment, it is possible to manufacture solid fuel with improved strength in high-temperature environments.

[0064] (12) A solid fuel according to embodiment 12 of the present disclosure is a method for producing the solid fuel according to (10) or (11), wherein the particle size of the biomass char is 10.0 mm or less.

[0065] According to the above embodiment, it is possible to manufacture a solid fuel that can maintain its strength in a high-temperature environment.

[0066] (13) A solid fuel according to embodiment 13 of the present disclosure is a method for producing any one of the solid fuels of (10) to (12), wherein the inorganic binder comprises Portland cement.

[0067] According to the above embodiment, a solid fuel with sufficiently high hot strength can be manufactured.

[0068] (14) A solid fuel according to embodiment 14 of the present disclosure is a method for manufacturing any one of the solid fuels described in (10) to (13), wherein the hot strength of the solid fuel is 1000 N or more.

[0069] According to the above embodiment, it is possible to manufacture a solid fuel that can sufficiently stabilize the combustion state inside the furnace.

[0070] (15) A solid fuel according to embodiment 15 of the present disclosure is a method for producing any one of the solid fuels described in (10) to (14), wherein the mass ratio of the water to the inorganic binder is 0.5 or more.

[0071] According to the above embodiment, a solid fuel with high strength can be manufactured.

[0072] (16) A solid fuel according to embodiment 16 of the present disclosure is a method for producing a solid fuel according to any one of (10) to (15), further comprising at least one selected from the group consisting of carboxymethylcellulose, polyvinyl alcohol, starch, and sodium silicate.

[0073] According to the above embodiment, a solid fuel with high cold strength can be manufactured.

[0074] (17) A solid fuel according to embodiment 17 of the present disclosure is a method for producing any one of the solid fuels of (10) to (16), wherein the molding raw material further comprises powdered coke.

[0075] According to the above embodiment, a solid fuel can be manufactured that can use powdered coke as a heat source.

[0076] The contents of this disclosure will be described in more detail below with reference to examples and comparative examples. However, this disclosure is not limited to the following examples.

[0077] (Effect of Fixed Carbon in Biomass Carbon) Acacia and pine chips and palm kernel shells (PKS) were prepared as biomass. Each chip and palm kernel shell was heated in an electric furnace in an oxygen-free atmosphere at approximately 700°C for 30 minutes by dry distillation, and then cooled in a nitrogen gas atmosphere. In this way, 11 types of biomass carbon with different fixed carbon contents were obtained (Carbon Nos. 1 to 11). Similarly, palm kernel shells were heated in an electric furnace in an oxygen-free atmosphere at approximately 700°C for 30 minutes by dry distillation, and then cooled in a nitrogen gas atmosphere. Six types of biomass carbon were obtained (Carbon Nos. 12 to 17). Each biomass carbon was crushed using a powder mill (CGOLDENWALL, model number: HC-2500) to adjust the particle size to 1.0 mm or less.

[0078] "Fixed Carbon Measurement" Industrial analysis of each biomass char was performed in accordance with JIS M 8812:2006 "Coal and coke - Industrial analytical methods". The results are shown in Tables 1 and 2A. The measurement results for fixed carbon and volatile matter are based on an anhydrous, ash-free basis.

[0079]

[0080] "Measurement of Particle Strength" The particle strength of biomass char (rubber tree) (95% fixed carbon) and biomass char (palm kernel shell) (93% fixed carbon) was measured in accordance with JIS Z 8841. Ten biomass chars with particle diameters ranging from 0.6 mm to 0.9 mm were selected, and one biomass char was placed approximately in the center of the fixed compression surface of the testing machine for measurement. The average of the ten biomass chars was taken as the particle strength of the biomass char. The particle strength of the biomass char (rubber tree) was 5.8 N / mm². ２ The particle strength of the biomass char (palm shell) was 10.0 N / mm². ２ It was found that PKS (palm kernel shells) has significantly higher particle strength than acacia and pine because it is made from coconut shells. For reference, the particle strengths of acacia and pine are shown in Table 1A. As shown in Table 1A, it was confirmed that acacia and pine have lower particle strength than PKS (palm kernel shells).

[0081]

[0082] "Preparation of Solid Fuel" Each biomass char, with a particle size adjusted to 1.0 mm or less, was mixed with commercially available rapid-hardening Portland cement (manufactured by Tokuyama Corporation) in a mass ratio of 70:30, and water was added and kneaded. The CaO content of the rapid-hardening Portland cement was 65% by mass. At this time, the mass ratio of water to rapid-hardening Portland cement (water addition rate) was 1.1. After kneading, a cylindrical molded body (diameter × height = 50 mm × 50 mm) was produced using a uniaxial press molding machine. This molded body was cured at 40°C for one day to obtain solid fuel.

[0083] "Hot Strength" The solid fuel was placed in an electric furnace and heated in air at 1000°C for 30 minutes. After that, it was cooled to approximately 20°C under a nitrogen atmosphere. This solid fuel (sample 10) was placed on the measuring stand 20 as shown in Figure 2, and the strength was measured at the point when a crack or fracture occurred after applying a load in the direction of the arrow (radial direction). The measurement results are shown in the "Hot Strength" column of Tables 2 and 2A. Note that the fixed carbon values ​​for solid fuels No. 9 and No. 55 in Table 2 are the fixed carbon values ​​used to estimate the hot strength. The hot strengths for solid fuels No. 9 and No. 55 in Table 2 are estimated values ​​obtained using the least squares method from the fixed carbon and hot strength of solid fuels No. 10 to 12. The "-" in column No. 12 of Table 2A indicates that the sample was brittle after heating and could not be measured.

[0084]

[0085]

[0086] As shown in Table 2, it was confirmed that solid fuels with high hot strength can be obtained by using biomass char with a high fixed carbon content. Furthermore, biomass char using palm kernel shells, which have high particle strength, showed higher hot strength than biomass char using pine and acacia.

[0087] [Effect of Inorganic Binder Content] Solid fuels were prepared in the same manner as described in "Preparation of Solid Fuel" above, except that the mixing ratio of each biomass char to commercially available rapid-hardening Portland cement was changed as shown in Table 3, and the hot strength of the solid fuels was measured. The results obtained are shown in Table 3. For comparison, Table 3 also shows the results for solid fuels No. 4 and No. 8. As is clear from the results for solid fuels No. 4, 8, and 13-18, lowering the ratio of Portland cement in the solid fuel reduces the hot strength of the solid fuel. In the linear relationship between the ratio of Portland cement and the solid fuel obtained from the results when the biomass was acacia or pine, the slope in the case of acacia was almost the same as the slope in the case of pine. Therefore, for solid fuel No. Using the hot strength of 11, the ratio of carbides, and the slope of the relational equation obtained for acacia and pine, the hot strength of biomass carbides (solid fuel No. 11) was estimated when the ratio was 80-90% by mass. The results obtained are shown for solid fuels No. 20-22.

[0088]

[0089] As shown in Table 3, it was confirmed that the hot strength could be increased by increasing the proportion of inorganic binder (early-strength Portland cement). When the biomass was acacia and pine, the hot strength of the solid fuel could be increased to 1000 N or more by increasing the inorganic binder content in the solid fuel to 15% by mass or more. Furthermore, from the results for solid fuels No. 20 to 22, it was estimated that using palm kernel shells as biomass would result in a high value of 1774 N even with a low proportion of Portland cement of about 10% by mass.

[0090] [Effect of Particle Size of Biomass Carbon] Solid fuel was prepared in the same manner as described in "Preparation of Solid Fuel" above, except that the particle size was changed by altering the grinding time in the powder mill or by changing the sieve used for sieving the biomass carbon, as shown in Table 4. The hot strength of the solid fuel was then measured. The results are shown in Table 4. For comparison, the results for solid fuels No. 4 and No. 8 are also shown in Table 4.

[0091]

[0092] As shown in Table 4, it was confirmed that the hot strength of the solid fuel could be adjusted by changing the particle size of the biomass char. The solid fuel with the highest hot strength was obtained when the particle size of the biomass char was 1.0 mm or less.

[0093] [Effect of Water Addition Rate] Solid fuel was prepared in the same manner as described in "Preparation of Solid Fuel" above, except that the particle size of the biomass char and the mass ratio of water to rapid-hardening Portland cement (water / inorganic binder) were changed as shown in Table 5, and the hot strength of the solid fuel was measured. The results are shown in Table 5. For comparison, the results for solid fuels No. 4 and No. 25 are also shown in Table 5.

[0094]

[0095] In Table 5, "Moisture content" refers to the mass ratio of water to the total of biomass char and rapid-hardening Portland cement. As shown in Table 4, it was confirmed that the hot strength increased as the water addition rate increased to 1.1 and the moisture content increased to approximately 33% by mass.

[0096] [Influence of Inorganic Binder Type and Curing Conditions] Solid fuel was prepared in the same manner as described in "Preparation of Solid Fuel" above, except that the curing time of the molded body at 40°C and the Portland cement were changed as shown in Table 6, and the hot strength of the solid fuel was measured. The results are shown in Table 6. For comparison, the results for solid fuel No. 4 are also shown in Table 6.

[0097]

[0098] The results in Table 6 confirm that even if the inorganic binder is ordinary Portland cement, a solid fuel with sufficient strength in a high-temperature environment can be obtained by extending the curing time.

[0099] [Effects of Additives] The following additives were prepared. All are commercially available products. • Polyvinyl alcohol • Carboxymethylcellulose • Starch • Bentonite • Kaolin • Kaolinite clay • Sodium silicate

[0100] Biomass char of char No. 4 and commercially available rapid-hardening Portland cement were mixed in a mass ratio of 70:30, and water was added and kneaded. At this time, the above additives were added in the addition ratios shown in Table 7. The addition ratios shown in Table 7 are the mass ratios to the total of biomass char and rapid-hardening Portland cement. The mass ratio of water to rapid-hardening Portland cement (water addition rate) was set to 1.1. Solid fuel was prepared in the same manner as in "Preparation of Solid Fuel" described above, except for the use of these molding raw materials, and the hot strength of the solid fuel was measured. The results are shown in Table 7.

[0101] In each example, the strength of the molded article was also measured immediately after molding and before curing at 40°C for one day. The results of this strength measurement are shown in Table 8 as "cold strength". The units of the values ​​in Tables 7 and 8 are "N".

[0102] Cold strength is the strength measured immediately after molding, without any heat treatment. Similar to hot strength, the molded body (sample 10) was placed on the measuring stand 20 as shown in Figure 2, and the strength was measured at the point when a crack or fracture occurred after applying a load in the direction of the arrow (radial direction).

[0103]

[0104]

[0105] As shown in Table 7, there was no significant change in hot strength even with the addition of additives. On the other hand, as shown in Table 8, it was confirmed that the cold strength could be significantly improved by including additives. This improves the handling properties until the inorganic binder hardens. In particular, it was found that the cold strength was especially high when polyvinyl alcohol, a type of organic binder, was added.

[0106] The solid fuel and its manufacturing method described herein have sufficient strength in high-temperature environments and therefore have high potential for industrial application.

[0107] 10...Sample, 20...Measurement stage

Claims

1. A solid fuel comprising biomass char with a fixed carbon content of 74% by mass or more on an anhydrous, ash-free basis, and an inorganic binder with a CaO content of 50% by mass or more in a dry state.

2. The particle strength of the biomass char is 10.0 N / mm². ２ The solid fuel according to claim 1.

3. The solid fuel according to claim 1 or 2, wherein the fixed carbon content is 77% by mass or more, and is based on an anhydrous, ash-free material.

4. The solid fuel according to claim 1 or 2, wherein the biomass char content is 50% by mass or more, and the inorganic binder content is 10% by mass or more.

5. The solid fuel according to claim 1 or 2, wherein the hot strength measured after heating in air at 1000°C for 30 minutes and then cooling is 1000 N or more.

6. The solid fuel according to claim 1 or 2, wherein the inorganic binder comprises Portland cement.

7. The solid fuel according to claim 1 or 2, wherein the particle size of the biomass carbon is 10.0 mm or less.

8. The solid fuel according to claim 1 or 2, further comprising at least one selected from the group consisting of carboxymethylcellulose, polyvinyl alcohol, starch, and sodium silicate.

9. The solid fuel according to claim 1 or 2, further comprising powdered coke.

10. A method for producing solid fuel, comprising the step of kneading and molding a molding raw material containing biomass char with a fixed carbon content of 74% by mass or more on an anhydrous, ash-free basis, an inorganic binder with a CaO content of 50% by mass or more in a dry state, and water.

11. The particle strength of the biomass char is 10.0 N / mm². ２ The method for producing solid fuel according to claim 10.

12. The method for producing solid fuel according to claim 10 or 11, wherein the particle size of the biomass char is 10.0 mm or less.

13. The method for producing a solid fuel according to claim 10 or 11, wherein the inorganic binder comprises Portland cement.

14. The method for producing a solid fuel according to claim 10 or 11, wherein the hot strength of the solid fuel is 1000 N or more.

15. The method for producing a solid fuel according to claim 10 or 11, wherein the mass ratio of water to the inorganic binder in the molding raw material is 0.5 or more.

16. The method for producing a solid fuel according to claim 10 or 11, wherein the molding raw material further comprises at least one selected from the group consisting of carboxymethylcellulose, polyvinyl alcohol, starch, and sodium silicate.

17. The method for producing a solid fuel according to claim 10 or 11, wherein the molding raw material further comprises powdered coke.

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