Solid fuel and method for producing solid fuel

Abstract

This solid fuel comprises: a biocoke of at least 85% fixed carbon on the anhydrous ash-free basis; and an inorganic binder containing CaO in a dry state at 50 mass% or higher. This method for producing a solid fuel comprises a step in which a solid fuel is obtained by kneading and molding a molding starting material comprising: a biocoke of at least 85% fixed carbon on the anhydrous ash-free basis; an inorganic binder containing CaO in a dry state at 50 mass% or higher; and water.

Description

Solid fuel and its manufacturing method

[0001] The present disclosure relates to solid fuels and methods for producing the same.

[0002] CO2 for global warming countermeasures ２ As a means of reducing CO2 emissions, technological developments are underway to use biomass instead of existing fossil fuels. Patent Document 1 proposes using a carbon-containing molded product obtained by adding a binder to biomass charcoal, molding the mixture, and dry distilling it, instead of the coke used in waste melting treatment facilities.

[0003] Japanese Patent Application Laid-Open No. 2006-57082

[0004] Patent Document 1 states that an organic binder is preferable when using a carbon-containing molded product as a fuel. However, organic binders are generally expensive and have difficulty maintaining strength in high-temperature environments. Therefore, the present disclosure provides a solid fuel that has sufficient strength in high-temperature environments and a method for producing the same.

[0005] One aspect of the present disclosure provides a solid fuel comprising biomass char having a fixed carbon content of 85% by mass or more on an anhydrous ash-free basis and an inorganic binder having a CaO content of 50% by mass or more in a dry state. Because the solid fuel contains biomass char having a fixed carbon content of 85% by mass or more and an inorganic binder, the solid fuel has sufficient strength in high-temperature environments.

[0006] One aspect of the present disclosure provides a method for producing a solid fuel, comprising the steps of kneading and forming a raw material comprising biomass char having a fixed carbon content of 85% by mass or more on an anhydrous ash-free basis, an inorganic binder having a CaO content of 50% by mass or more in a dry state, and water. Because this production method uses biomass char having a fixed carbon content of 85% by mass or more and an inorganic binder, the resulting solid fuel has sufficient strength in high-temperature environments.

[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 producing the same.

[0008] The present invention relates to a gasification melting furnace and a waste melting treatment facility, and is a method for measuring the strength of the waste material under hot and cold conditions.

[0009] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings where 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] A solid fuel according to one embodiment includes biomass char having a fixed carbon content of 88% by mass or more on an anhydrous and ash-free basis, and an inorganic binder having a CaO content of 50% by mass or more in a dry state.

[0011] In this specification, biomass refers to biological resources other than fossil fuels. Examples of biomass include waste materials such as thinned wood, pruned branches, waste wood, bark chips, other wood, bamboo, grass, coconut shells, palm oil residue, vegetables, fruits, food waste, and sludge. The biomass may be woody biomass such as thinned wood, pruned branches, waste wood, bark chips, and other wood. Biomass carbonized material can be obtained by dry distilling such biomass.

[0012] The fixed carbon of the biomass charcoal may be 85% by mass or more, 88% by mass or more, or 90% by mass or more on an anhydrous ash-free basis. Biomass charcoal with a high fixed carbon content has a low volatile content, and therefore few components volatilize even in high-temperature environments. Therefore, it is possible to maintain sufficient strength even in high-temperature environments. The fixed carbon on an anhydrous ash-free basis can be determined by converting the value of fixed carbon on an anhydrous basis measured in accordance with "8. Calculation method for fixed carbon mass fraction (%)" of JIS M 8812:2006 "Coals and cokes - Proximate analysis methods" into a value on an anhydrous ash-free basis.

[0013] The particle size of the biomass char 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 is too large, the adhesion between the biomass char particles may decrease, resulting in a decrease in strength. If the particle size is too small, the contact area between the biomass char particles may increase too much, resulting in a decrease in strength. The particle size of the biomass char can be measured using a sieve. When sieved using a sieve with 2 mm openings, the particle size that falls through the sieve is 2 mm or less.

[0014] The content of biomass char in the solid fuel is 50% by mass or more, and may be 60% by mass or more, or 65% by mass or more. By increasing the content of biomass char, the calorific value of the solid fuel can be sufficiently increased. The content of biomass char 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 a solid fuel can have even higher strength in high-temperature environments.

[0015] The inorganic binder is an inorganic substance that functions to bind biomass char particles together. The inorganic binder has a CaO content of 50% by mass or more in a dry state. In a dry state, the CaO content in the inorganic binder may be 55% by mass or more, or 60% by mass or more. Such an inorganic binder can lower the melting point of slag when used as solid fuel in a gasification melting furnace or a cupola furnace. In these facilities, limestone is sometimes used as a secondary material, and the CaO in the inorganic binder can replace part or all of the limestone.

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

[0017] The waste, solid fuel, and secondary materials are charged into the melting furnace 40 by the charging device 50. Examples of waste include municipal solid waste, industrial waste, processed waste such as incineration ash obtained by drying, incinerating, crushing, etc., and landfill waste containing soil and sand excavated after these waste materials have been buried in a landfill. The secondary materials may include at least one selected from limestone, iron ore, magnesia, periclase, diatomite, and jamonite. The use of such secondary materials allows the waste 48 to be sufficiently melted inside the melting furnace 40. Coal, coke, molded charcoal, etc. may also be used together with the solid fuel of this embodiment.

[0018] Waste, solid fuel, and secondary materials are charged into the melting furnace 40 from the charging device 50. Oxygen or oxygen-enriched air is supplied from the lower tuyere 47, and air is supplied as a combustion support gas from the upper tuyere 45. The solid fuel charged into the melting furnace 40 is combusted with the oxygen or oxygen-enriched air supplied from the lower tuyere 47 and functions as a heat source. The waste 48 including secondary 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 pyrolysis residue 43. The pyrolysis residue 43 is combusted mainly with the air supplied from the upper tuyere 45.

[0019] The pyrolysis gas generated in the melting furnace 40 rises up the shaft 42 and is introduced into the combustion chamber through an exhaust gas pipe 52 connected to the bottom of the charging device 50. The combustion exhaust gas is burned as combustible gas and then the waste heat is recovered in a boiler. The exhaust gas then has its temperature adjusted in a cooling tower, passes through a dust collector and a catalytic reaction tower, and is discharged from a chimney.

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

[0021] The combustible matter in the waste 48 and the biomass char contained in the solid fuel are gasified, rise within the melting furnace 40, and are introduced into the combustion chamber via an exhaust gas pipe 52. Meanwhile, the ash turns into molten slag via the pyrolysis residue 43. The CaO and silica source contained in the inorganic binder function as melting point adjusters and basicity adjusters for the molten slag. The molten slag, whose melting point and basicity have been adjusted, flows down the coke packed layer 41 at the furnace bottom 46 and is discharged from a slag discharge port 49.

[0022] The maximum temperature of the melting furnace 40 may be, for example, 1600°C or higher in the combustion / melting zone 40c. The solid fuel charged from the charging device 50 has sufficient strength in a high-temperature environment, so it can maintain its shape for a while after being introduced into the melting furnace 40. During this time, the solid fuel is prevented from pulverizing, and the inorganic binder is prevented from scattering. As a result, the CaO contained in the inorganic binder of the solid fuel functions satisfactorily as a melting point adjuster and basicity adjuster for the molten slag. The basicity (CaO / SiO ２ The composition of the solid fuel and the amount of secondary materials charged from the charging device 50 may be adjusted so that the ratio (R) is, for example, 0.7 to 1.0. This allows molten slag with excellent fluidity to be discharged from the slag discharge port 49.

[0023] The molten slag can be discharged from the slag discharge port 49 either continuously (continuous slag discharge) or intermittently (intermittent slag discharge). In the case of intermittent slag discharge, the interval between discharges can be, for example, 30 minutes or more, or even 1 hour or more. The molten slag discharged from the slag discharge port 49 can be introduced into a water granulation tank containing cooling water and granulated there.

[0024] In a cupola furnace, the solid fuel of this embodiment can be used instead of coke stacked in the furnace body. Pig iron, scrap steel, and other metals are loaded in a predetermined ratio from above the solid fuel, which has been stacked to a certain height. The solid fuel is burned while air is sent through tuyeres located at the bottom of the furnace body, and the resulting combustion heat melts the metals. The metals are melted in a melting zone in the center of the furnace body and discharged from a tapping port at the bottom. Because the solid fuel has sufficient strength in a high-temperature environment, it can stably form a bed within the furnace body. The CaO contained in the solid fuel functions as a melting point adjuster, allowing for a reduction in the amount of secondary materials used, such as limestone.

[0025] The inorganic binder may contain Portland cement as defined in JIS R 5210:2009. Such a solid fuel can have sufficiently high strength in high-temperature environments and can significantly reduce production costs. Examples of Portland cement include ordinary Portland cement, high-early-strength Portland cement, ultra-high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement. The CaO content of Portland cement can be measured in accordance with JIS R 5202:2010, "Chemical Analysis Methods for Cement." By including Portland cement in the inorganic binder, the hot strength of the solid fuel can be sufficiently increased.

[0026] The inorganic binder may contain components other than Portland cement. Examples include clay and sodium silicate. Examples of clay include bentonite (montmorillonite) and kaolin. When 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 above-mentioned range.

[0027] The inorganic binder content 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 high-temperature environments. The inorganic binder content 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 inorganic binder content, the biomass char content can be increased, thereby sufficiently increasing the calorific value of the solid fuel.

[0028] The solid fuel may contain components other than the biomass char and the inorganic binder. Examples of such components include coke powder and an organic binder. By including coke powder in the solid fuel, the coke powder can be effectively used as a heat source. Examples of organic binders include polyvinyl alcohol, carboxymethyl cellulose, and starch. By including an organic binder, the cold strength of the solid fuel (molded body) can be increased, thereby improving the handleability immediately after molding.

[0029] The solid fuel is a compact obtained by compression molding. There is no limitation on the size of each compact, and it can be, for example, 1 to 800 cm. ３ , 3 to 600 cm ３ , or 50 to 200 cm ３ When solid fuel of such a size is used as fuel for a gasification melting furnace and a cupola, it is possible to form an appropriate grate and ensure a sufficiently stable combustion state within the furnace.

[0030] The hot strength of the solid fuel is preferably 300 N or more, more preferably 500 N or more, even 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 or cupola, an appropriate grate can be formed, ensuring a sufficiently stable combustion state within the furnace.

[0031] The hot strength and cold strength herein are measured by the following procedure. A solid fuel is heated in air at 1000°C for 30 minutes using an electric furnace. It is then cooled to room temperature (approximately 20°C) in a nitrogen atmosphere. If the solid fuel is cylindrical, after cooling, the solid fuel (sample 10) is placed on a measurement table 20 as shown in FIG. 2 , and a load is applied in the direction of the arrow (radial direction). The load at which cracks or breaks occur in the sample 10 is taken as the hot strength (N). A solid fuel with high hot strength has sufficiently high strength in a high-temperature environment. Alternatively, a load is applied to another sample 10 as shown in FIG. 2 without heating using an electric furnace, and the load at which cracks or breaks occur in the sample 10 is taken as the cold strength (N).

[0032] The solid fuel of this embodiment contains biomass charcoal, which reduces fossil fuel consumption and carbon dioxide emissions. By using it as fuel for gasification melting furnaces and cupolas, the melting point of slag can be adjusted. Furthermore, the amount of limestone used as a secondary material can be reduced.

[0033] A method for producing a solid fuel according to one embodiment includes a dry distillation step of dry distilling and carbonizing biomass to obtain a biomass char having a fixed carbon content of 85% by mass or more on an anhydrous ash-free basis, a pulverization step of pulverizing the biomass char, a molding step of kneading and molding a raw material containing the pulverized biomass char, 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 details described for the solid fuel also apply to this manufacturing method.

[0034] The carbonization step may be carried out by heating the biomass to a carbonization temperature of 200°C or higher in an oxygen-free atmosphere. The ease with which carbonization of biomass proceeds varies depending on the tree species, the part of the tree, etc. Regardless of the tree species and the part of the tree of the biomass, from the viewpoint of stably and smoothly proceeding with carbonization, the carbonization may be carried out by heating the biomass to 250°C or higher, or may be carried out by heating to 320°C or higher. From the viewpoint of increasing the yield of the carbon material, the carbonization step may be carried out 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 may be 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 may be 2 hours or less, from the viewpoint of improving the productivity of the biomass char. The fixed carbon content of the biomass char can be adjusted by changing the carbonization temperature and carbonization time.

[0036] In the pulverization step, the particle size of the biomass char is adjusted. The pulverization may be performed using a pulverization mill. The particle size of the biomass char may be adjusted to the above-mentioned range. By performing the pulverization step after the carbonization step, the pulverization can be performed smoothly.

[0037] In the molding process, biomass charcoal, inorganic binder, water, and other optional components are blended and kneaded to prepare a molding raw material. Optional components include coke powder, organic binder, and inorganic substances other than 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. This allows for sufficient strength of the solid fuel. From a similar perspective, 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 a similar perspective, the mass ratio of water to the total of the biomass charcoal and inorganic binder may be 15 to 65%, 20 to 60%, or 25 to 55%. This allows for sufficient hardening of the inorganic binder even if the biomass charcoal absorbs some of the water. After kneading, the molding raw material is molded to obtain a compact. For molding, a conventional molding machine such as a uniaxial press or a briquette roll can be used.

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

[0039] After the curing step, a drying step may be carried out in an atmosphere at a higher temperature than that in the curing step, thereby reducing the moisture content of the inorganic binder and obtaining a solid fuel with even higher strength.

[0040] The solid fuel obtained by the manufacturing method of this embodiment has sufficient strength in high-temperature environments. Therefore, it is useful as fuel for, for example, a gasification melting furnace or a cupola. In this case, the melting point of the slag can be adjusted. Furthermore, the amount of limestone used as a secondary material can be reduced. Furthermore, since biomass carbide is used, fossil fuel consumption can be reduced, thereby reducing carbon dioxide emissions.

[0041] Although exemplary embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. The use of the solid fuel is not limited to gasification and melting furnaces and cupolas. The present disclosure includes the following embodiments.

[0042] [1] A solid fuel comprising a biomass charcoal having a fixed carbon content of 85% by mass or more on an anhydrous ash-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 biomass charcoal content is 50% by mass or more and the inorganic binder content is 15% by mass or more. [3] The solid fuel according to [1] or [2], wherein the hot strength measured after heating in air at 1000°C for 30 minutes and cooling is 1000 N or more. [4] The solid fuel according to any one of [1] to [3], wherein the inorganic binder comprises Portland cement. [5] The solid fuel according to any one of [1] to [4], wherein the particle size of the biomass charcoal 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 coke breeze. [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 function of adjusting the melting point of slag. [9] A method for producing a solid fuel, comprising a step of kneading and forming a raw material comprising biomass charcoal having a fixed carbon content of 85% by mass or more on an anhydrous ash-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 size of the biomass charcoal is 10 mm or less.

[11] The solid fuel according to [9] or

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

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

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

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

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

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

[14] , wherein the raw material for forming further contains coke powder.

[0043] The present disclosure will be described in more detail below with reference to examples and comparative examples, although the present disclosure is not limited to the following examples.

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

[0045] Proximate analysis of each biomass char was carried out in accordance with JIS M 8812:2006 "Coals and cokes - Proximate analysis methods." The results are shown in Table 1. The measurement results for fixed carbon and volatile matter are values ​​on an anhydrous ash-free basis.

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

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

[0048]

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

[0050] [Effect of inorganic binder content] (Examples 5 to 7) Solid fuels were prepared in the same manner as in Example 2, except that the blending ratio of each biomass char to commercially available high-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. Table 2 also shows the results of Example 2 for comparison.

[0051] (Examples 8 to 10) Solid fuels were prepared in the same manner as in Example 4, except that the blending ratio of each biomass char to commercially available high-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. Table 2 also shows the results of Example 4 for comparison.

[0052]

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

[0054] [Effect of particle size of biomass char] (Examples 11 to 14) Solid fuels were produced in the same manner as in Example 2, except that the sieve used to sieve the biomass char was changed and biomass chars with particle sizes 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) Biomass charcoal with the particle sizes shown in Table 3 was prepared by varying the grinding time using a powder mill. Solid fuel was produced in the same manner as in Example 4, except that biomass charcoal with these particle sizes was used, and the hot strength of the solid fuel was measured. The results are shown in Table 3. For comparison, the results of Example 4 are also shown in Table 3.

[0056]

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

[0058] [Effect of Water Addition Rate] (Examples 19 to 23) Solid fuels were prepared in the same manner as in Example 13, except that the mass ratio of water to high-early-strength Portland cement (water addition rate) was changed as shown in Table 4, and the hot strength of the solid fuels 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) Solid fuels were prepared in the same manner as in Example 2, except that the mass ratio of water to high-early-strength Portland cement (water addition rate) was changed as shown in Table 4, and the hot strength of the solid fuels was measured. The results are shown in Table 4. Table 4 also shows the results of Example 2 for comparison.

[0060]

[0061] "Moisture content" in Table 4 is the mass ratio of water to the total of biomass charcoal and high-early-strength 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 about 33 mass%.

[0062] [Effect of Type of Inorganic Binder and Curing Conditions] (Examples 29 to 31) Solid fuels were prepared in the same manner as in Example 2, except that the curing time of the compacts at 40°C was changed as shown in Table 5, and the hot strength of the solid fuels 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) Solid fuels were prepared in the same manner as in Example 2, except that commercially available ordinary Portland cement (manufactured by Tokuyama Corporation) was used instead of high-early-strength Portland cement, and the curing time of the compacts at 40°C was changed as shown in Table 5. The results are shown in Table 5.

[0064]

[0065] The results in Table 5 confirm that even if the inorganic binder is ordinary Portland cement, if the curing time is extended, a solid fuel having sufficient strength in a high-temperature environment can be obtained.

[0066] [Effects of Additives] (Examples 35 to 41) The following additives were prepared. All of them are commercially available products: Polyvinyl alcohol Carboxymethyl cellulose Starch Bentonite Kaolin Gairome clay Sodium silicate

[0067] The biomass charcoal used in Example 2 and commercially available high-early-strength Portland cement were blended in a mass ratio of 70:30, and water was added and kneaded. The additives were added in the amounts shown in Table 6. The amounts shown in Table 6 are mass ratios relative to the total mass of the biomass charcoal and high-early-strength Portland cement. The mass ratio of water to high-early-strength Portland cement (water addition rate) was 1.1. Aside from using these molding raw materials, a solid fuel was prepared in the same manner as in Example 2, 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 manner as in Example 2, but without adding any additives.

[0068] In each example, the strength of the molded body was also measured immediately after molding and before curing at 40°C for 1 day. The results of this strength measurement are shown in Table 7 as "cold strength." The unit of values ​​in Tables 6 and 7 is "N."

[0069] The cold strength is measured immediately after molding without heat treatment. As in the case of the hot strength, the cold strength was measured by placing the molded body (sample 10) on a measurement table 20 as shown in Figure 2, applying a load in the direction of the arrow (radial direction), and measuring the strength at the time when cracks or fractures occurred.

[0070]

[0071]

[0072] As shown in Table 6, the addition of additives did not significantly change the hot strength. On the other hand, as shown in Table 7, it was confirmed that the inclusion of additives can significantly improve the cold strength. This improves the handling ability until the inorganic binder hardens. In particular, it was found that the cold strength was particularly high when polyvinyl alcohol, a type of organic binder, was added.

[0073] 10...sample, 20...measurement table, 40...melting furnace, 40a...drying / preparation zone, 40b...pyrolysis zone, 40c...combustion / melting zone, 41...coke packed bed, 42...shaft section, 43...pyrolysis residue, 44...morning glory section, 45...upper tuyere, 46...furnace bottom section, 47...lower tuyere, 48...waste, 49...slag discharge port, 50...charging device, 52...exhaust gas pipe, 100...waste melting treatment equipment.

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, 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 claim 1 or 2, wherein the inorganic binder contains Portland cement.

5. The solid fuel according to claim 1 or 2, wherein the particle size 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 producing 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 producing a solid fuel according to claim 9, wherein the particle size of the biomass carbide is 10 mm or less.

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

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

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