Solid fuel and method for producing solid fuel

Abstract

To provide a solid fuel having adequate strength in high-temperature environments and a method for producing the same.SOLUTION: Provided is a solid fuel comprising a biomass carbonaceous material having at least 85 mass% fixed carbon on an anhydrous ash-free basis and an inorganic binder containing at least 50 mass% CaO in a dry state. Also provided is a method for producing a solid fuel, the method comprising a step of obtaining a solid fuel by kneading and molding a molding starting material comprising a biomass carbonaceous material having at least 85 mass% fixed carbon on an anhydrous ash-free basis, an inorganic binder containing at least 50 mass% CaO in a dry state, and water.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to solid fuel and a method for producing the same.

Background Art

[0002] As a means for reducing CO2 for countermeasures against global warming, technological development is underway to utilize biomass instead of existing fossil fuels. In Patent Document 1, it has been proposed to use a carbon-containing molded product obtained by adding a binder to biomass carbide, molding it, and carbonizing it, instead of coke used in waste melting treatment facilities.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, when using a carbon-containing molded product as fuel, an organic binder is considered preferable. However, organic binders are generally expensive and difficult to maintain strength in high-temperature environments. Therefore, the present disclosure provides a solid fuel having sufficient strength in a high-temperature environment and a method for producing the same.

Means for Solving the Problems

[0005] One aspect of the present disclosure provides a solid fuel including a biomass carbide having a fixed carbon content of 85% 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. Since this solid fuel contains a biomass carbide having a fixed carbon content of 85% by mass or more and an inorganic binder, it has sufficient strength in a high-temperature environment.

[0006] One aspect of the present disclosure provides a method for manufacturing solid fuel, which includes a step of kneading and molding a molding raw material containing a biomass carbide having a fixed carbon content of 85% by mass or more on an ash-free and moisture-free basis, an inorganic binder having a CaO content of 50% by mass or more in a dry state, and water. In this manufacturing method, since a biomass carbide having a fixed carbon content of 85% by mass or more and an inorganic binder are used, it has sufficient strength in a high-temperature environment.

Advantages of the Invention

[0007] According to the present disclosure, it is possible to provide a solid fuel having sufficient strength in a high-temperature environment and a method for manufacturing the same.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0009] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings as appropriate. The following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents.

[0010] The solid fuel according to one embodiment includes a biomass carbide having a fixed carbon content of 88% 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.

[0011] As used herein, biomass refers to resources derived from organisms other than fossil fuels. Examples of biomass include thinned wood, pruned branches, waste wood, bark chips, other woods, bamboo, grass, coconut shells, palm oil residues, vegetables, fruits, food residues, sludge, and other wastes. Biomass may be lignocellulosic biomass such as thinned wood, pruned branches, waste wood, bark chips, and other woods. Biomass carbide can be obtained by carbonizing such biomass.

[0012] The fixed carbon of the biomass carbide may be 85% by mass or more, 88% by mass or more, or 90% by mass or more on an ash-free and moisture-free basis. Since biomass carbide with a high fixed carbon has a low volatile content, there are few components that volatilize even in a high-temperature environment. Therefore, sufficient strength can be maintained even in a high-temperature environment. The fixed carbon on an ash-free and moisture-free basis can be obtained by converting the value of the fixed carbon on a moisture-free basis measured in accordance with the "8. Method for Calculating Fixed Carbon Mass Fraction (%)" of JIS M 8812:2006 "Coals and Cokes - Industrial Analysis Methods" to the value on an ash-free and moisture-free basis.

[0013] The particle size of the biomass carbide may be 10 mm or less, 2 mm or less, 0.5 to 2 mm, or 0.8 to 1.5 mm. If the particle size becomes too large, the adhesion between the particles of the biomass carbide may decrease and the strength may decrease. If the particle size becomes too small, the contact area between the particles of the biomass carbide may increase too much and the strength may decrease. The particle size of the biomass carbide can be measured using a sieve. The particle size of the fraction passing through a sieve with a mesh size of 2 mm is 2 mm or less when sieved using a 2-mm sieve.

[0014] The content of the biomass carbide in the solid fuel is 50% by mass or more, and may be 60% by mass, 65% by mass or more. By increasing the content of the biomass carbide, the calorific value of the solid fuel can be made sufficiently high. The content of the biomass carbide in the solid fuel may be 90% by mass or less, 85% by mass or less, 80% by mass or less, or 75% by mass or less. Such solid fuel can have even higher strength in a high-temperature environment.

[0015] The inorganic binder is an inorganic substance having a function of binding particles of biomass carbide. The inorganic binder has a CaO content of 50% by mass or more in the dry state. In the dry state, the CaO content in the inorganic binder may be 55% by mass or more, or 60% by mass or more. With such an inorganic binder, when used as a solid fuel in a gasification melting furnace or a cupola furnace, the melting point of the slag can be reduced. In these facilities, limestone may be used as an auxiliary material, but part or all of the limestone can be replaced by the CaO of the inorganic binder.

[0016] FIG. 1 shows a waste melting treatment facility 100 including a coke bed type melting furnace 40 which is an example of a gasification melting furnace. The solid fuel of the present embodiment can replace the coke in such a melting furnace 40. The waste melting treatment facility 100 in FIG. 1 includes a melting furnace 40 and a charging device 50 provided above the melting furnace 40. The melting furnace 40 has a shaft portion 42, a morning glory portion 44 provided at the lower end of the shaft portion 42, and a furnace bottom portion 46 provided below the morning glory portion 44. From the shaft portion 42 to the furnace bottom portion 46, an upper tuyere 45 for the pyrolysis zone and a lower tuyere 47 for the combustion melting zone are provided in order from above. The upper tuyere 45 and the lower tuyere 47 may each be provided in a plurality of stages.

[0017] The waste, solid fuel, and auxiliary material are charged into the melting furnace 40 by the charging device 50. Examples of the waste include general waste, industrial waste, processed products such as incineration ash obtained by subjecting these to treatments such as drying, incineration, and crushing, and landfill waste including the soil and sand that have been landfilled once and then dug up again. The auxiliary material may include at least one selected from limestone, iron ore, magnesia, periclase, kudokanran stone, and jamon stone. By using such an auxiliary material, the waste 48 can be sufficiently melted inside the melting furnace 40. Coal, coke, formed charcoal, etc. may be used together with the solid fuel of the present embodiment.

[0018] Waste, solid fuel, and auxiliary materials are charged from the charging device 50 into the melting furnace 40. Oxygen or oxygen-enriched air is supplied from the lower tuyere 47, and air is supplied as combustion-supporting gas from the upper tuyere 45. The solid fuel charged into the melting furnace 40 is burned by the oxygen or oxygen-enriched air supplied from the lower tuyere 47 and functions as a heat source. The waste 48 containing the auxiliary materials charged into the melting furnace 40 is heated to, for example, 1600 °C or higher by the combustion of the solid fuel and becomes the pyrolysis residue 43. The pyrolysis residue 43 is mainly burned by the air supplied from the upper tuyere 45.

[0019] The pyrolysis gas generated in the melting furnace 40 rises through the shaft portion 42 and is introduced from the exhaust gas pipe 52 connected to the lower part of the charging device 50 into the combustion chamber. The combustion exhaust gas is burned as a combustible gas and then the waste heat is recovered in a boiler. Thereafter, the exhaust gas is cooled in a desuperheater tower and then discharged from the chimney after passing through a dust collector and a catalytic reaction tower.

[0020] A temperature gradient is generated inside the melting furnace 40 by the combustion of solid fuel and the like. Specifically, the melting furnace 40 has a drying / preheating zone 40a, a pyrolysis zone 40b, and a combustion / melting zone 40c from top to bottom. The auxiliary materials introduced from the charging device 50 into the melting furnace 40 reach the drying / preheating zone 40a, the pyrolysis zone 40b, and the combustion / melting zone 40c in this order together with the waste and the solid fuel. CaO and the like contained in the inorganic binder of the solid fuel reach the combustion / melting zone 40c.

[0021] The combustible components in the waste 48 and the biomass carbide contained in the solid fuel are gasified and rise inside the melting furnace 40, and are introduced into the combustion chamber via the exhaust gas pipe 52. On the other hand, the ash becomes molten slag through the pyrolysis residue 43. CaO and the silica source contained in the inorganic binder function as a melting point adjuster and a basicity adjuster for the molten slag. The molten slag with adjusted melting point and basicity flows down through the coke packing layer 41 at the furnace bottom 46 and is discharged from the tapping hole 49.

[0022] The maximum temperature of the melting furnace 40 may be, for example, 1600°C or higher in the combustion and melting zone 40c. Since the solid fuel charged from the charging device 50 has sufficient strength in a high-temperature environment, it can maintain its shape for a while after being introduced into the melting furnace 40. During this period, since pulverization of the solid fuel is suppressed, scattering of the inorganic binder is suppressed. As a result, CaO contained in the inorganic binder of the solid fuel sufficiently functions as a melting point adjuster and basicity adjuster of the molten slag. The composition of the solid fuel charged from the charging device 50 and the amount of auxiliary materials may be adjusted so that the basicity (CaO / SiO2) of the molten slag discharged from the slag tapping port 49 of the melting furnace 40 is, for example, 0.7 to 1.0. Thereby, molten slag having excellent fluidity is discharged from the slag tapping port 49.

[0023] The slag tapping of the molten slag from the slag tapping port 49 may be performed continuously (continuous slag tapping) or intermittently (intermittent slag tapping). The interval of slag tapping during intermittent slag tapping may be, for example, 30 minutes or longer, or 1 hour or longer. The molten slag discharged from the slag tapping port 49 may be introduced into a granulation tank containing cooling water and granulated, for example.

[0024] In the cupola furnace, the solid fuel of the present embodiment can be used instead of the coke stacked in the furnace body. Pig iron, steel scraps and other ingots and the solid fuel are charged at a predetermined ratio from above the solid fuel stacked to a certain height. While air is sent from the tuyere provided at the lower part of the furnace body, the solid fuel is burned, and the ingots are melted by the combustion heat. The ingots are melted in the melting zone at the central part of the furnace body and are led out from the tapping hole at the lowermost part. Since the solid fuel has sufficient strength in a high-temperature environment, a stable bed can be formed in the furnace body. Since CaO contained in the solid fuel functions as a melting point adjuster, the amount of use of auxiliary materials such as limestone can be reduced.

[0025] The inorganic binder may include Portland cement defined in JIS R 5210:2009. Such solid fuel can have sufficiently high strength in a high-temperature environment and can sufficiently reduce the manufacturing cost. Examples of Portland cement include ordinary Portland cement, early-strength Portland cement, ultra-early-strength Portland cement, medium-heat Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement. The content of CaO contained in Portland cement can be measured in accordance with the "Chemical Analysis Method of Cement" in JIS R 5202:2010. By including Portland cement in the inorganic binder, the hot strength of the solid fuel can be made sufficiently high.

[0026] The inorganic binder may contain components other than Portland cement. For example, clay, sodium silicate, etc. may be mentioned. Examples of clay include bentonite (montmorillonite), kaolin, etc. When the inorganic binder contains multiple types of components, the content of CaO in the entire inorganic binder may be within the above range.

[0027] The content of the inorganic binder in the solid fuel may be 10% by mass or more, 15% by mass or more, 20% by mass or more, or 25% by mass or more. Such solid fuel has higher strength in a high-temperature environment. The content of the inorganic binder in the solid fuel may be 45% by mass or less, 40% by mass or less, or 35% by mass or less. By reducing the content of the inorganic binder, the content of biomass carbide can be increased to make the calorific value of the solid fuel sufficiently high.

[0028] The solid fuel may contain components other than biomass carbide and inorganic binder. Such components include pulverized coke and organic binder. By including pulverized coke in the solid fuel, the pulverized coke can be effectively utilized as a heat source. Examples of the organic binder include polyvinyl alcohol, carboxymethyl cellulose, and starch. By including the organic binder, the cold strength of the solid fuel (formed body) can be increased, thereby improving the handleability immediately after forming.

[0029] The solid fuel is a formed body obtained by compression molding. There is no limit to the size of each formed body. For example, it may be 1 to 800 cm 3 , 3 to 600 cm 3 , or 50 to 200 cm 3 . The solid fuel of such a size can form a suitable fire grate when used as fuel for a gasification melting furnace and a cupola, and can make the combustion state in the furnace sufficiently stable.

[0030] The hot strength of the solid fuel is preferably 300 N or more, more preferably 500 N or more, still more preferably 800 N or more, and particularly preferably 1000 N or more. Such solid fuel can maintain a sufficiently high strength in a high-temperature environment. For example, when used as solid fuel for a gasification melting furnace and a cupola, it can form a suitable fire grate and make the combustion state in the furnace sufficiently stable.

[0031] The hot strength and cold strength in this specification are measured by the following procedure. The solid fuel is heated in air at 1000 °C for 30 minutes using an electric furnace, and then cooled to room temperature (about 20 °C) in a nitrogen atmosphere. When the solid fuel is cylindrical, after cooling, as shown in Figure 2, the solid fuel (sample 10) is placed on the measuring table 20, and a load is applied in the arrow direction (radial direction). The load at the time when cracks or fractures occur in the sample 10 is taken as the hot strength (N). The solid fuel with high hot strength has a sufficiently high strength in a high-temperature environment. Also, using another sample 10, without heating using an electric furnace, a load is applied as shown in Figure 2, and the load at the time when cracks or fractures occur in the sample 10 is taken as the cold strength (N).

[0032] Since the solid fuel of this embodiment contains biomass carbide, the consumption of fossil fuels can be reduced and the amount of carbon dioxide emissions can be reduced. By using it as fuel in a gasification melting furnace, cupola, etc., the melting point of the slag can be adjusted. Also, the amount of limestone used as an auxiliary material can be reduced.

[0033] A method for manufacturing a solid fuel according to an embodiment includes a carbonization step of carbonizing biomass by dry distillation to obtain a biomass carbide having a fixed carbon content of 85% by mass or more on an ash-free and moisture-free basis, a pulverization step of pulverizing the biomass carbide, and a molding step of kneading and molding a molding raw material including the pulverized biomass carbide, an inorganic binder having a CaO content of 50% by mass or more in a dry state, and water, and a curing step of curing the molded body. The solid fuel obtained by this manufacturing method may be the solid fuel described in the above embodiment. Therefore, the content described for the solid fuel is also applicable to this manufacturing method.

[0034] The carbonization step may be performed by heating the biomass at a carbonization temperature of 200°C or higher in an oxygen-free atmosphere. The ease of carbonization of biomass varies depending on the tree species and the part of the tree. From the viewpoint of allowing carbonization to proceed stably and smoothly regardless of the tree species and the part of the tree, the carbonization may be performed by heating the biomass to 250°C or higher, or may be performed by heating to 320°C or higher. From the viewpoint of increasing the yield of the carbon material, the carbonization step may be performed by heating the biomass to 900°C or lower, or 700°C or lower. That is, an example of the carbonization temperature is 200 to 900°C.

[0035] In the carbonization step, the heating time within the above temperature range may be 20 minutes or more, or 30 minutes or more, from the viewpoint of sufficiently carbonizing the biomass. In the carbonization step, the heating time within the above temperature range may be 3 hours or less, or 2 hours or less, from the viewpoint of improving the productivity of the biomass carbide. The fixed carbon of the biomass carbide can be adjusted by changing the carbonization temperature and the carbonization time.

[0036] In the crushing process, the particle size of the biomass carbide is adjusted. Crushing may be performed using a grinding mill. The particle size of the biomass carbide may be adjusted to the above-mentioned range. By performing the crushing process after the carbonization process, the crushing can be performed smoothly.

[0037] In the forming process, a molding raw material is prepared by blending biomass carbide, an inorganic binder, water, and other optional components and kneading them. Examples of the optional components include pulverized coke, an organic binder, and inorganic substances different from the inorganic binder. In the molding raw material, the mass ratio of water to the inorganic binder may be 0.5 or more, 0.7 or more, or 1.0 or more. Thereby, the strength of the solid fuel can be sufficiently increased. From the same viewpoint, the mass ratio of water to the inorganic binder may be 3.0 or less, 2.5 or less, or 2.0 or less. From the same viewpoint, the mass ratio of water to the total of the biomass carbide and the inorganic binder may be 15 - 65%, 20 - 60%, or 25 - 55%. Thereby, even if the biomass carbide absorbs a part of water, the inorganic binder can be sufficiently cured. After kneading, the molding raw material is molded to obtain a molded body. For molding, a uniaxial compression molding machine or an ordinary molding machine such as a briquette roll can be used.

[0038] In the curing process, the inorganic binder contained in the molded body is cured to obtain a solid fuel. Appropriate curing conditions may be selected according to the type of the inorganic binder. For example, when the inorganic binder is Portland cement, curing may be performed by holding at 20 - 50°C for 4 hours or more, 6 hours or more, 10 hours or more, or 24 hours or more.

[0039] After the curing process, a drying process may be performed. Drying may be performed in an atmosphere at a temperature higher than that of the curing process. Thereby, 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. Therefore, for example, it is useful as a fuel for a gasification melting furnace or a cupola. 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 amount of carbon dioxide emissions can be reduced.

[0041] As described above, the exemplary embodiments of the present disclosure have been described, but the present disclosure is not limited to the above embodiments at all. The use of the solid fuel is not limited to that for a gasification melting furnace and a cupola. The present disclosure includes the following embodiments.

[0042] [1] A solid fuel comprising a biomass carbide having a fixed carbon content of 85% 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. [2] The solid fuel according to [1], wherein the content of the biomass carbide is 50% by mass or more and the content of the inorganic binder is 15% by mass or more. [3] The solid fuel according to [1] or [2], having a hot strength of 1000 N or more measured after heating at 1000 °C for 30 minutes and cooling in air. [4] The solid fuel according to any one of [1] to [3], wherein the inorganic binder contains Portland cement. [5] The solid fuel according to any one of [1] to [4], wherein the particle size of the biomass carbide is 10 mm or less. [6] The solid fuel according to any one of [1] to [5], further comprising at least one selected from the group consisting of carboxymethyl cellulose, polyvinyl alcohol, starch, sodium silicate, and clay. [7] The solid fuel according to any one of [1] to [6], further comprising pulverized coke. [8] The solid fuel according to any one of [1] to [7], which is for a gasification melting furnace or a cupola and has a slag melting point adjusting function. [9]A method for manufacturing solid fuel, comprising a step of kneading and molding a molding raw material containing a biomass carbide having a fixed carbon content of 85% by mass or more on an ash-free and moisture-free basis, an inorganic binder having a CaO content of 50% by mass or more in a dry state, and water.

[10] The solid fuel according to [9], wherein the particle diameter of the biomass carbide is 10 mm or less.

[11] The method for manufacturing solid fuel according to [9] or

[10] , wherein the inorganic binder contains Portland cement.

[12] The method for manufacturing solid fuel according to any one of [9] to

[11] , wherein the hot strength of the solid fuel is 1000 N or more.

[13] The method for manufacturing solid fuel according to any one of [9] to

[12] , wherein the mass ratio of water to the inorganic binder in the molding raw material is 0.5 or more.

[14] The method for manufacturing solid fuel according to any one of [9] to

[13] , wherein the molding raw material further contains at least one selected from the group consisting of carboxymethyl cellulose, polyvinyl alcohol, sodium silicate, and clay.

[15] The method for manufacturing solid fuel according to any one of [9] to

[14] , wherein the molding raw material further contains pulverized coke.

Examples

[0043] Hereinafter, the content of the present disclosure will be described in more detail with reference to examples and comparative examples. However, the present disclosure is not limited to the following examples.

[0044] [Effect of Fixed Carbon in Biomass Carbide] (Examples 1 to 4, Comparative Examples 1 to 4) Acacia and pine chips were prepared as biomass. Each chip was heated and carbonized at about 700°C for 30 minutes in an oxygen-free atmosphere using an electric furnace, and cooled in a nitrogen gas atmosphere. In this way, eight types of biomass carbides having different fixed carbon contents were obtained. Each biomass carbide was pulverized using a powder mill (manufactured by CGOLDENWALL, model number: HC-2500), and the particle diameter was adjusted to 1 mm or less.

[0045] In accordance with JIS M 8812:2006 "Coals and Cokes - Proximate Analysis Method", proximate analysis of each biomass carbide was carried out. The results were as shown in Table 1. The measurement results of fixed carbon and volatile matter are values on a moisture - and ash - free basis.

[0046] Each biomass carbide with a particle size adjusted to 1 mm or less and commercially available early - strength Portland cement (manufactured by Tokuyama Corporation) were blended at a mass ratio of 70:30, and water was added and kneaded. The CaO content of the early - strength Portland cement was 65 mass%. At this time, the mass ratio of water to the early - strength Portland cement (water addition rate) was set to 1.1. After kneading, a cylindrical molded body (diameter × height = 50 mm × 50 mm) was produced using a uniaxial compression molding machine. This molded body was cured at 40 °C for 1 day to obtain a solid fuel.

[0047] The solid fuel was placed in an electric furnace and heated at 1000 °C for 30 minutes in air. Then, it was cooled to about 20 °C in a nitrogen atmosphere. This solid fuel (Sample 10) was placed on the measuring table 20 as shown in Figure 2, and a load was applied in the arrow direction (radial direction) to measure the strength at the time when cracks or fractures occurred. The measurement results are shown in the column of "hot strength" in Table 1.

[0048] [Table 1]

[0049] As shown in Table 1, it was confirmed that by using a biomass carbide with a high fixed - carbon content, a solid fuel with high hot strength can be obtained.

[0050] [Effect of Content of Inorganic Binder] (Examples 5 - 7) Solid fuels were produced in the same manner as in Example 2 except that the blending ratio of each biomass carbide and commercially available early - strength Portland cement was changed as shown in Table 2, and the hot strength of the solid fuels was measured. The results are shown in Table 2. For comparison, the results of Example 2 are also shown in Table 2.

[0051] (Examples 8 to 10) Solid fuels were produced in the same manner as in Example 4, except that the blending ratios of each biomass carbide and commercially available early-strength Portland cement were changed as shown in Table 2, and the hot strength of the solid fuels was measured. The results are shown in Table 2. Table 2 also shows the results of Example 4 for comparison.

[0052]

Table 2

[0053] As shown in Table 2, it was confirmed that the hot strength could be increased by increasing the ratio of the inorganic binder (early-strength Portland cement). By setting the content of the inorganic binder in the solid fuel to 15% by mass or more, the hot strength of the solid fuel could be made 1000 N or more.

[0054] [Effect of Particle Size of Biomass Carbide] (Examples 11 to 14) Solid fuels were produced in the same manner as in Example 2, except that the sieves used for screening the biomass carbide were changed and biomass carbides with particle sizes as shown in Table 3 were used, and the hot strength of the solid fuels was measured. The results are shown in Table 3. Table 3 also shows the results of Example 2 for comparison.

[0055] (Examples 15 to 18) The pulverization time by the powder mill was changed to prepare biomass carbides with particle sizes as shown in Table 3. Solid fuels were produced in the same manner as in Example 4, except that biomass carbides with such particle sizes were used, and the hot strength of the solid fuels was measured. The results are shown in Table 3. Table 3 also shows the results of Example 4 for comparison.

[0056]

Table 3

[0057] As shown in Table 3, it was confirmed that the value of the hot strength of the solid fuel can be adjusted by changing the particle size of the biomass carbide. When the particle size of the biomass carbide was 1 mm or less, a solid fuel having the highest hot strength could be obtained.

[0058] [Effect of water addition rate] (Examples 19 to 23) A solid fuel was produced in the same manner as in Example 13 except that the mass ratio of water to the early-strength Portland cement (water addition rate) was changed as shown in Table 4, and the hot strength of the solid fuel was measured. The results are shown in Table 4. Table 4 also shows the results of Example 13 for comparison.

[0059] (Examples 24 to 28) A solid fuel was produced in the same manner as in Example 2 except that the mass ratio of water to the early-strength Portland cement (water addition rate) was changed as shown in Table 4, and the hot strength of the solid fuel was measured. The results are shown in Table 4. Table 4 also shows the results of Example 2 for comparison.

[0060] [Table 4]

[0061] "Moisture" in Table 4 is the mass ratio of water to the total of the biomass carbide and the early-strength Portland cement. As shown in Table 4, it was confirmed that the hot strength increased as the water addition rate increased to about 1.1 and the moisture increased to about 33 mass%.

[0062] [Effect of type of inorganic binder and curing conditions] (Examples 29 to 31) A solid fuel was produced in the same manner as in Example 2 except that the curing time of the molded body at 40 °C was changed as shown in Table 5, and the hot strength of the solid fuel was measured. The results are shown in Table 5. Table 5 also shows the results of Example 2 for comparison.

[0063] (Examples 32 to 34) A solid fuel was produced in the same manner as in Example 2, except that commercially available ordinary Portland cement (manufactured by Tokuyama Corporation) was used instead of the early-strength Portland cement, and the curing time of the molded body at 40 °C was changed as shown in Table 5, and the hot strength of the solid fuel was measured. The results are shown in Table 5.

[0064] [Table 5]

[0065] From the results in Table 5, it was confirmed that even when the inorganic binder is ordinary Portland cement, a solid fuel having sufficient strength in a high-temperature environment can be obtained by increasing the curing time.

[0066] [Effect of Additives] (Examples 35 to 41) The following additives were prepared. All are commercially available products. · Polyvinyl alcohol · Carboxymethyl cellulose · Starch · Bentonite · Kaolin · Toad's eye clay · Sodium silicate

[0067] The biomass carbide used in Example 2 and commercially available early-strength Portland cement were blended at a mass ratio of 70:30, and water was added and kneaded. At this time, the above additives were added at the addition ratios shown in Table 6. The addition ratios shown in Table 6 are mass ratios with respect to the total of the biomass carbide and the early-strength Portland cement. The mass ratio of water to the early-strength Portland cement (water addition rate) was 1.1. A solid fuel was produced in the same manner as in Example 2, except that such molding raw materials were used, and the hot strength of the solid fuel was measured. The results are shown in Table 6. Example 2A in Table 6 is a solid fuel prepared in the same procedure as in Example 2 without adding an additive.

[0068] In each example, immediately after molding, the strength of the molded body before curing at 40°C for one day was also measured. The measurement results of this strength are shown in Table 7 as "cold strength". The units of the numerical values in Tables 6 and 7 are "N".

[0069] Cold strength is the strength measured immediately after molding without performing heat treatment. Similar to the hot strength, for the molded body (sample 10), as shown in Figure 2, it was placed on the measurement table 20, and a load was applied in the arrow direction (radial direction), and the strength at the time when cracks or fractures occurred was measured.

[0070] [Table 6]

[0071] [Table 7]

[0072] As shown in Table 6, even when additives were added, there was no significant change in the hot strength. On the other hand, as shown in Table 7, it was confirmed that the cold strength could be significantly improved by including additives. Thereby, the handleability until the inorganic binder hardens can be improved. In particular, it was found that when polyvinyl alcohol, which is a kind of organic binder, was added, the cold strength became particularly high.

Explanation of Signs

[0073] 10…Sample, 20…Measurement table, 40…Melting furnace, 40a…Drying / preheating zone, 40b…Pyrolysis zone, 40c…Combustion / melting zone, 41…Coke filling layer, 42…Shaft part, 43…Pyrolysis residue, 44…Morning glory part, 45…Upper tuyere, 46…Furnace bottom, 47…Lower tuyere, 48…Waste, 49…Tapping hole, 50…Charging device, 52…Exhaust gas pipe, 100…Waste melting treatment facility.

Claims

1. A solid fuel comprising a biomass carbide having a fixed carbon content of 85% 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.

2. The solid fuel according to claim 1, wherein the content of the biomass carbide is 50% by mass or more, and the content of the inorganic binder is 15% by mass or more.

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

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

5. The solid fuel according to claim 1 or 2, wherein the particle diameter of the biomass carbide is 10 mm or less.

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

7. The solid fuel according to claim 1 or 2, further comprising pulverized coke.

8. The solid fuel according to claim 1 or 2, which is for a gasification - melting furnace or a cupola and has a slag melting - point adjusting function.

9. A method for manufacturing a solid fuel, comprising a step of kneading and molding a molding raw material containing a biomass carbide having a fixed carbon content of 85% by mass or more on an ash - free and moisture - free basis, an inorganic binder having a CaO content of 50% by mass or more in a dry state, and water.

10. The method for manufacturing a solid fuel according to claim 9, wherein the particle diameter of the biomass carbide is 10 mm or less.

11. The method for manufacturing a solid fuel according to claim 9 or 10, wherein the inorganic binder contains Portland cement.

12. The method for manufacturing a solid fuel according to claim 9 or 10, wherein the hot strength of the solid fuel is 1000 N or more.

13. The method for manufacturing a solid fuel according to claim 9 or 10, wherein the mass ratio of water to the inorganic binder in the molding raw material is 0.5 or more.

14. The method for manufacturing a solid fuel according to claim 9 or 10, wherein the molding raw material further comprises at least one selected from the group consisting of carboxymethyl cellulose, polyvinyl alcohol, starch, sodium silicate, and clay.

15. The method for manufacturing a solid fuel according to claim 9 or 10, wherein the molding raw material further comprises pulverized coke.

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