Manufacturing method of solid fuel

Abstract

To provide a method for manufacturing solid fuel that enables the stable production of solid fuel even when reducing the amount of anti-fusing agents such as pulverized coal used when manufacturing solid fuel using waste materials including waste plastics. [Solution] A method for producing solid fuel is provided, comprising a heating step of heating waste raw materials containing waste plastic in a heating furnace to thermally decompose at least a portion of the waste plastic, wherein the waste raw materials include a first waste containing thermoplastic plastic and a second waste having a higher mass ratio of construction waste plastic than the first waste, and in the heating step, the first waste and the second waste are introduced into the heating furnace together or separately.

Description

Technical Field

[0005] ,

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

Background Art

[0002] Various techniques for producing solid fuel by heat-treating waste containing waste plastic have been studied (Patent Documents 1 to 3). In Patent Document 1, attempts have been made to produce solid fuel with reduced chlorine by individually heating and embrittling waste containing chlorine such as waste plastic, pulverizing it, and then performing air classification. When heating waste containing such waste plastic, the molten plastic adheres to the furnace wall of the heating furnace, increasing the maintenance frequency of the operating equipment. For this reason, in Patent Documents 2 and 3, techniques have been proposed to mix thermoplastic plastic and fine coal before heating with a heating device to suppress the fusion of the thermoplastic plastic inside the heating device.

Prior Art Documents

Patent Documents

[0003]

Patent Document No. 1

Patent Document No. 2

Patent Document No. 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] From the perspective of promoting decarbonization, it is preferable to reduce the amount of fine coal used. Therefore, the present disclosure provides a method for producing solid fuel that can stably produce solid fuel even when reducing the amount of anti-fusion agents such as fine coal when producing solid fuel using waste raw materials containing waste plastic.

Means for Solving the Problems

[0005] One aspect of this disclosure is, A method for producing solid fuel, comprising a heating step of heating waste raw materials including waste plastic in a heating furnace to thermally decompose at least a portion of the waste plastic, The aforementioned waste raw materials are The first waste includes thermoplastic plastics, and the second waste has a higher mass ratio of construction waste plastics than the first waste. The present invention provides a method for producing solid fuel, wherein the heating step involves introducing the first waste and the second waste into the heating furnace together or separately.

[0006] In the above manufacturing method, during the heating process, a first waste containing thermoplastic plastic and a second waste with a higher mass ratio of construction waste plastic than the first waste are introduced into the heating furnace together or separately. It is believed that the mud and sand contained in the construction waste plastic of the second waste adhere to the surface of the molten thermoplastic plastic contained in the first waste introduced into the heating furnace. This suppresses the fusion of the thermoplastic plastic into the inside of the heating furnace. Therefore, solid fuel can be stably produced even with a reduced amount of anti-fusion agents such as pulverized coal. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a method for manufacturing solid fuel that enables the stable production of solid fuel even when the amount of anti-fusing agents such as pulverized coal is reduced when manufacturing solid fuel using waste raw materials including waste plastics. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view showing an example of a solid fuel manufacturing apparatus. [Figure 2] This graph shows the particle size distribution of the solid fuels in Comparative Examples 1, 2, and 3. [Figure 3] (A) is a photograph of the solid fuel of Comparative Example 4, (B) is a photograph of the solid fuel of Example 1, and (C) is a photograph of the solid fuel of Example 2. [Modes for carrying out the invention]

[0009] Embodiments of the present disclosure will be described below, with reference to the drawings as appropriate. However, the following embodiments are illustrative for the purpose of illustrating the present disclosure and are not intended to limit the present disclosure to the following. In the description, the same reference numerals will be used for elements that are the same or have the same function, and redundant explanations will be omitted as appropriate. Also, positional relationships such as up, down, left, and right will be based on the orientation of the reference numerals in the drawings unless otherwise specified. The dimensional ratios of each element are not limited to the ratios shown. In the description, the symbol "~" used in numerical ranges indicates a numerical range that includes the upper and lower limits. For example, "X~Y" indicates a numerical range of "X or greater and Y or less". Numerical ranges in which the upper and / or lower limits of a numerical range are replaced with the values ​​described in the examples are also included in the present disclosure. If a numerical range is illustrated with only the upper limit or only the lower limit, a numerical range combining the numerical range with only the upper limit and the numerical range with only the lower limit is also included in the present disclosure. Numerical ranges in which the upper and / or lower limits of one numerical range are replaced with the upper and / or lower limits of another numerical range are also included in the present disclosure.

[0010] A method for producing solid fuel according to one embodiment includes a heating step of heating waste raw materials containing waste plastics in a heating furnace to thermally decompose at least a portion of the waste plastics. The waste raw materials include a first waste containing thermoplastic plastics and a second waste having a higher mass ratio of construction-related plastics than the first waste.

[0011] The waste raw materials containing waste plastics may be either industrial waste or general waste, and examples include container recycling residue, shredder dust, construction waste plastics, agricultural waste plastics, fishery waste plastics, marine waste plastics, etc. The waste raw materials may also contain foreign matter other than waste plastics. Examples of foreign matter include paper, rubber, wood scraps, metal scraps, metal wires, metal foils, glass scraps, concrete scraps, ceramic scraps, slag, rubble, mud, and sand. From the viewpoint of obtaining a heat-treated product with large particle size and a solid fuel with high added value, the mass percentage of waste plastics in the waste raw materials may be 40% by mass or more, 50% by mass or more, or 60% by mass or more. The second waste may be construction plastics themselves, or a mixture of construction waste plastics and other waste raw materials. The first waste may contain construction plastics in a lower mass ratio than the second waste.

[0012] The first type of waste includes thermoplastics. Thermoplastics are plastics manufactured using thermoplastic resins. Thermoplastics may include, for example, at least one selected from the group consisting of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyethylene terephthalate, polyamide, polycarbonate, and acrylic. The form of the thermoplastics is not particularly limited and may be, for example, foam, film, or granular.

[0013] The thermoplastic content in the first waste may be 30% by mass or more, 40% by mass or more, or more than 50% by mass. Waste materials with a high thermoplastic content tend to melt and fuse into the inside of the heating furnace when heated, and also tend to fuse and become coarse. In the above manufacturing method, by using a specified second waste, it is possible to suppress the fusion and coarsening of thermoplastics and their fusion into the inside of the heating furnace.

[0014] The first waste may include, in addition to thermoplastics, thermosetting plastics, combustible materials such as fibers, paper, wood, leather, elastomers and rubber, and noncombustible materials such as metals, ceramics, glass and mud. Thermosetting plastics are plastics manufactured using thermosetting resins. Thermosetting plastics may include, for example, at least one selected from the group consisting of polyurethane, melamine, unsaturated polyester, phenolic resin, urea resin, silicone resin, epoxy resin, and alkyd resin. The form of the thermosetting plastic is not particularly limited and may be, for example, fluff, foam, or granular. From the viewpoint of ensuring a sufficiently high calorific value of the solid fuel, the proportion of combustible materials in the first waste may be 60% by mass or more, 70% by mass or more, or 80% by mass or more.

[0015] The first type of waste may include rigid plastics. In this disclosure, rigid plastics have a tensile modulus of 1000 MPa or more, as measured in accordance with ASTM D638. Rigid plastics have excellent mechanical strength, heat resistance, and chemical resistance, and are used in a wide range of fields, such as electronic equipment housings, automotive parts, household goods, and building materials. Rigid plastics may include, for example, at least one selected from the group consisting of polycarbonate, polypropylene, polystyrene, acrylonitrile butadiene styrene, polyamide, polyethylene terephthalate, polyvinyl chloride, polymethyl methacrylate, and polyphenylene sulfide.

[0016] Since hard plastics have a higher melting point than soft plastics, they are considered to be less likely to fuse during the heating process. From the viewpoint of obtaining a heat-treated product with sufficiently small particle size, the hard plastic content in the first waste may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 35% by mass or more. From the viewpoint of increasing the degree of freedom in selecting the first waste, the hard plastic content in the first waste may be 60% by mass or less, or 50% by mass or less.

[0017] The first waste may contain at least one selected from the group consisting of container recycling residues and shredder dust.

[0018] The maximum particle size of the first waste may be less than 50 mm, less than 40 mm, or less than 30 mm. Thereby, the variation in the particle size of the heat-treated product can be made sufficiently small. In the present disclosure, the "maximum particle size" is based on the size of the sieve opening. The first waste having a particle size less than 50 mm can be obtained as the undersize when sieving is performed using a sieve with a 50 mm opening.

[0019] The second waste contains construction waste plastics. The mass ratio of the construction waste plastics in the second waste may be 50% by mass or more, 70% by mass or more, or 90% by mass or more. The construction waste plastics are waste plastics generated at a construction site. The construction waste plastics may be obtained by separating the waste generated at the construction site. Such construction waste plastics may contain mud and sand in addition to the waste plastics. The construction waste plastics may contain one or both of thermoplastic plastics and thermosetting plastics.

[0020] The second waste may have a higher total content of mud and sand than the first waste. Since the properties of mud and sand do not change even when heated in the heating process, they have the function of suppressing the fusion of thermoplastic plastics inside the heating furnace and the coarsening of thermoplastic plastics due to fusion. The content of mud and sand in the second waste may be 10% by mass or more, 20% by mass or more, or 25% by mass or more from the viewpoint of sufficiently reducing a fusion inhibitor such as pulverized coal. The content of mud and sand in the second waste may be 50% by mass or less, or 40% by mass or less from the viewpoint of sufficiently increasing the calorific value of the solid fuel.

[0021] The amount of mud and sand is determined based on the mass of the material in a dry state, excluding moisture. The mud and sand may be attached to waste plastics or other components contained in the second type of waste, or they may be present on their own without attachment. The mud may be clay and silt, etc. The mud and sand may consist of mineral particles with a particle size of less than 2 mm, and multiple particles may be aggregated into clumps. Mineral particles with a particle size of less than 2 mm are particles that can pass through a sieve with a mesh size of 2 mm.

[0022] The second waste may contain fibers, paper, and wood chips. The fibers in this disclosure may be natural fibers, synthetic fibers, or recycled fibers. The fibers may be included in the form of woven fabrics, knitted fabrics, nonwoven fabrics, felts, filters, nets, ropes, or composite materials. The paper in this disclosure is made from plant fibers such as wood pulp, mixed with water, formed into sheets, and dried. Examples of paper include printing and writing paper, packaging paper, specialty paper, industrial paper, art and craft paper, and corrugated cardboard. The wood chips may be wood chips, shavings, bark, chips, or dust.

[0023] The second waste may have a higher total content of fibers, paper, and wood chips than the first waste. Of the fibers, natural fibers and recycled fibers tend to carbonize rather than melt during the heating process. Paper and wood chips also tend to carbonize during the heating process. These carbonized materials have the function of preventing thermoplastics from fusing into the inside of the heating furnace and from becoming bulky due to the fusion of thermoplastics. From the viewpoint of fully exhibiting these functions, the total content of fibers, paper, and wood chips in the second waste may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 35% by mass or more. From the viewpoint of improving the freedom of obtaining the second waste, the total content of fibers, paper, and wood chips in the second waste may be 80% by mass or less, 70% by mass or less, or 60% by mass or less.

[0024] The second waste may include combustible materials such as thermoplastics, thermosetting plastics, leather, elastomers, and rubber, as well as non-combustible materials such as metals, ceramics, and glass. Specific examples of thermoplastics and thermosetting plastics may be as described above. The combustible material content in the second waste may be lower than that of the first waste. From the viewpoint of ensuring a sufficiently high calorific value for solid fuel, the proportion of combustible materials in the second waste may be 50% by mass or more, 60% by mass or more, or 70% by mass or more.

[0025] The thermoplastic content in the second waste may be lower than that in the first waste. The thermoplastic content in the second waste may be less than 40% by mass, less than 30% by mass, or less than 20% by mass. By using such second waste, it is possible to suppress the fusion and coarsening of thermoplastics and their adhesion to the inside of the heating furnace.

[0026] The maximum particle size of the second waste can be less than 100 mm, less than 80 mm, or less than 60 mm. This allows for a sufficient reduction of coarse particles that may be generated by the fusion of plastics. The second waste with a maximum particle size of less than 100 mm can be obtained as the residue after sieving using a sieve with a mesh size of 100 mm.

[0027] The first waste and the second waste may be introduced separately into the heating furnace and mixed within the furnace, or there may be a mixing step before the heating step in which the waste is heated in the furnace, in which a mixed raw material containing at least the first waste and the second waste is prepared. In the waste raw material, the ratio of the second waste to the sum of the first and second waste may be 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, or 30% by mass or more. By increasing the ratio of the second waste to the first waste, the fusion of thermoplastic plastics into the inside of the heating furnace can be sufficiently suppressed. From the viewpoint of effectively utilizing the first waste containing thermoplastic plastics, the ratio of the second waste to the sum of the first and second waste may be 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less. The ratio of the second waste to the sum of the first and second waste may be 5 to 80% by mass.

[0028] The total content of mud and sand in the waste raw material may be 3% by mass or more, 5% by mass or more, or 8% by mass or more. By increasing the total content of mud and sand, it is possible to sufficiently suppress the fusion of thermoplastics into the inside of the heating furnace and the fusion and coarsening of thermoplastics. The total content of mud and sand in the waste raw material may be 15% by mass or less, or 10% by mass or less. This makes it possible to maintain a high calorific value of the solid fuel. The total content of mud and sand in the waste raw material may be 3 to 15% by mass from the viewpoint of achieving a good balance of the above characteristics. Mud and sand in the waste raw material may be contained only in the second waste, or they may be contained in both the first and second waste.

[0029] In the mixing process, the first waste, the second waste, and pulverized coal may be mixed to obtain a mixed raw material containing these. The mixed raw material thus obtained may be introduced into a heating furnace. Alternatively, the waste raw material containing the first and second waste and the pulverized coal may be introduced into the heating furnace separately. The mixing process can be carried out using, for example, a V-type mixer, a W-type mixer, a drum-type mixer, a self-rotating or revolving screw conveyor, a kiln-type dryer, etc.

[0030] The total content of mud and sand in the mixed raw materials may be 2% by mass or more, 4% by mass or more, or 6% by mass or more. By increasing the total content of mud and sand, it is possible to sufficiently suppress the fusion of thermoplastics into the inside of the heating furnace and the coarsening of thermoplastics through fusion. The total content of mud and sand in the mixed raw materials may be 12% by mass or less, or 8% by mass or less. This allows for maintaining a high calorific value of the solid fuel. The total content of mud and sand in the waste raw materials may be 2 to 12% by mass, from the viewpoint of achieving a good balance of the above characteristics.

[0031] The total content of pulverized coal, mud, and sand in the mixed raw materials may be 25% by mass or more, 30% by mass or more, 35% by mass or more, or 40% by mass or more. By increasing this total content, the fusion of thermoplastic plastics inside the heating furnace can be sufficiently suppressed. From the viewpoint of promoting the fuel conversion of waste plastics, the total content of pulverized coal, mud, and sand in the mixed raw materials may be 60% by mass or less, or less than 50% by mass.

[0032] The mass ratio of pulverized coal to waste raw materials may be 1.0 or less, 0.8 or less, 0.6 or less, or 0.4 or less. Even with such a low mass ratio of pulverized coal, the use of the second type of waste suppresses the fusion of thermoplastic plastics inside the heating furnace, allowing for the stable production of solid fuel. In the solid fuel manufacturing method of this embodiment, pulverized coal may not be used at all. By reducing the amount of pulverized coal used, the amount of fossil fuels used can be reduced, further promoting decarbonization.

[0033] The ratio of second-class waste to pulverized coal may be 20% by mass or more, 30% by mass or more, or 40% by mass or more. By increasing this ratio, the amount of fossil fuels used can be reduced and decarbonization can be further promoted. The ratio of second-class waste to pulverized coal may be 80% by mass or less, or 70% by mass or less.

[0034] The maximum particle size of the waste material may be less than 50 mm, less than 40 mm, or less than 30 mm. Reducing the particle size of the waste material improves the mixability of the first and second waste. This allows for a significant reduction in the amount of pulverized coal used and further promotes decarbonization. Before the mixing process, a crushing process may be performed to crush the first and second waste separately, or a crushing process may be performed to crush the mixed material obtained in the mixing process. The crushing process may be performed using, for example, a shredder, granulator, or crusher. In the mixing process, the first and second waste may be crushed while being mixed.

[0035] The waste material is introduced into a continuous or batch heating furnace and heated to 250-500°C, 300-450°C, or 300-400°C. The heating time may be 0.5-3 hours or 1-2 hours. This allows for sufficient thermal decomposition and desalination of waste plastics while producing solid fuel with a high yield. The inside of the heating furnace may be an inert gas atmosphere. The heating furnace may be a rotary kiln equipped with lifter blades, for example, from the viewpoint of suppressing the fusion of thermoplastic plastics inside the furnace.

[0036] The mass ratio of particles with a particle size of 16 mm or larger in the heat-treated product (solid fuel) obtained in the heating process may be 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less. The lower limit of the mass ratio of particles with a particle size of 16 mm or larger may be 1% by mass. The mass ratio of particles with a particle size of 16 mm or larger is the mass ratio on the sieve when sieved using a sieve with a mesh size of 16 mm.

[0037] The average particle size (Dp50) of the heat-treated material (solid fuel) may be less than 15 mm, less than 10 mm, less than 8 mm, or less than 6 mm. The average particle size (Dp50) can be determined by the following procedure: The heat-treated material is sieved to determine the mass ratio in each of the seven particle size ranges: less than 1.0 mm, 1.0 mm to less than 2.0 mm, 2.0 mm to less than 2.8 mm, 2.8 mm to less than 4.7 mm, 4.7 mm to less than 9.5 mm, 9.5 mm to less than 16 mm, and 16 mm or more. The median of each particle size range is considered to have the mass ratio in that particle size range, and a quadratic function is found that has a correlation coefficient (r) closest to 1. Note that the mass ratio of less than 1.0 mm and 16 mm or more is considered to be the mass ratio of particle sizes 1.0 mm and 16 mm. Based on the obtained quadratic function, the particle size at which the cumulative weight ratio from the smallest particle size side becomes 50% by mass is taken as the average particle size (Dp50).

[0038] The heat-treated material may be used as solid fuel as is. That is, the solid fuel may have the particle size and average particle size described above. A post-pulverization step may be performed to pulverize the heat-treated material obtained in the heating step. A classification step may be performed to classify the pulverized material after pulverization. This makes it possible to obtain solid fuel with uniform particle size. Alternatively, a classification step may be performed to classify the heat-treated material without a post-pulverization step. The post-pulverization step may be performed using, for example, a mill. The classification step may be performed using, for example, a vibrating sieve or a centrifugal classifier.

[0039] The total content of mud and sand in the heat-treated material (solid fuel) may be 3% by mass or more, 5% by mass or more, or 9% by mass or more. Such heat-treated material (solid fuel) reduces the consumption of pulverized coal while suppressing fusion into the inside of the heating furnace. Therefore, it can be manufactured stably while promoting decarbonization. The total content of mud and sand in the heat-treated material (solid fuel) may be 30% by mass or less, 20% by mass or less, or 10% by mass or less. This allows the calorific value of the heat-treated material (solid fuel) to be maintained at a sufficiently high level.

[0040] The above-described method for manufacturing solid fuel may be carried out using, for example, the manufacturing apparatus 100 shown in Figure 1. The manufacturing apparatus 100 in Figure 1 comprises an indirectly heated rotary kiln 10 having a kiln body 12 (inner cylinder) and an outer cylinder 14, an introduction section 50 for introducing raw materials 51 into the kiln body 12 of the rotary kiln 10, and an outlet section 30 for discharging the heat-treated material 53 (solid fuel) from the kiln body 12 of the rotary kiln 10. The introduction section 50 only needs to have a configuration that can transport the raw materials 51, and may include, for example, a conveyor. The raw materials 51 may be a mixed raw material containing first waste, second waste, and pulverized coal. Upstream of the introduction section 50, a mixer for mixing the first waste, second waste, and pulverized coal may be provided. In a modified example, the introduction section 50 may separately introduce the mixed raw material of the first waste and second waste and the pulverized coal into the kiln body 12 and mix them within the kiln body 12. In yet another variation, the introduction section 50 may introduce the first waste, the second waste, and pulverized coal separately into the kiln body 12 and mix them within the kiln body 12.

[0041] In the rotary kiln 10, the kiln body 12 has lifter blades inside and is rotatably supported by rollers 15 and 16. Raw material 51 is introduced into the kiln body 12 from the inlet 50. The rotation axis of the kiln body 12 is slightly inclined with respect to the horizontal, with the inlet 50 side being higher than the outlet 30 side. Therefore, the raw material 51 introduced into the kiln body 12 is agitated by the lifter blades as the kiln body 12 rotates, moving from the inlet 50 side to the outlet 30 side. In Figure 1, the raw material 51 moves from left to right inside the kiln body 12.

[0042] In addition to the raw material 51, an inert gas may be introduced into the kiln body 12 of the rotary kiln 10. Examples of inert gases include nitrogen gas and exhaust gas containing carbon dioxide. The inert gas may also move along with the raw material 51 within the kiln body 12 from the upstream side to the downstream side. The raw material 51 is heated within the kiln body 12, causing the waste plastic to melt or carbonize to become a heat-treated product 53. The heat-treated product 53 is discharged from the kiln body 12 to the outlet section 30 and introduced into the cooler 40. After being cooled in the cooler 40, the heat-treated product 53 is discharged from the manufacturing apparatus 100. The heat-treated product 53 discharged from the manufacturing apparatus 100 may be used as solid fuel as is, or it may be crushed in a pulverizer and used as solid fuel.

[0043] The pyrolysis gas G3 generated by heating the raw material 51 inside the kiln body 12 is discharged from the outlet 32 ​​of the outlet section 30. An outer cylinder 14 is provided on the outer circumference of the kiln body 12. The outer cylinder 14 forms a hot gas flow path 17 that indirectly heats the kiln body 12. Hot gas G1 is supplied to the hot gas flow path 17 formed by the outer cylinder 14 from the gas inlet 21. The hot gas G1 may be exhaust gas from combustion equipment such as a boiler. The temperature of the hot gas G1 may be, for example, 400 to 500°C. The hot gas G1 heats the kiln body 12 by flowing through the hot gas flow path 17. The hot gas G1 that has heated the kiln body 12 is discharged to the outside as exhaust gas G2 from the gas outlet 22. Since the manufacturing apparatus 100 is supplied with waste raw materials including both the first waste and a second waste with a higher mass ratio of construction waste plastics than the first waste, it is possible to suppress the fusion of molten thermoplastics to the inner wall 13 of the kiln body 12. This allows for stable and continuous operation.

[0044] The manufacturing apparatus used in the solid fuel manufacturing method of this embodiment is not limited to that shown in Figure 1. For example, the manufacturing apparatus may be a batch furnace equipped with lifter blades. In the manufacturing method of this embodiment, it is possible to suppress the adhesion of mud and sand to the surface of thermoplastic plastics and the resulting fusion of the thermoplastic plastics. Therefore, the frequency of maintenance of the heating equipment can be reduced, and the production of solid fuels can be continued stably. In addition, it is possible to reduce the amount of coal-derived anti-fusing agent used, thereby promoting decarbonization.

[0045] The above-described embodiment includes the following: [1] A method for producing a solid fuel, comprising a heating step of heating waste raw materials including waste plastic in a heating furnace to thermally decompose at least a portion of the waste plastic, The aforementioned waste raw materials are The first waste includes thermoplastic plastics, and the second waste has a higher mass ratio of construction waste plastics than the first waste. A method for producing solid fuel, wherein in the heating step, the first waste and the second waste are introduced into the heating furnace together or separately. [2] The method for producing a solid fuel according to [1], wherein the second waste has a higher total content of mud and sand than the first waste. [3] The method for producing solid fuel according to [1] or [2], wherein the total content of mud and sand in the waste raw material is 3% by mass or more. [4] Prior to the heating step, the mixing step is to prepare a mixed raw material containing at least the first waste and the second waste, A method for producing solid fuel according to any one of [1] to [3], wherein the heating step involves introducing the mixed raw materials into the heating furnace. [5] The method for producing solid fuel according to [4], wherein the mixed raw materials contain pulverized coal, and the ratio of the second waste to the pulverized coal is 10% by mass or more. [6] The method for producing solid fuel according to [5], wherein the total content of the pulverized coal and mud and sand in the mixed raw materials is 30% by mass or more. [7] The method for producing solid fuel according to [5] or [6], wherein the total content of the pulverized coal and the second waste in the mixed raw materials is 40% by mass or more. [8] A method for producing a solid fuel according to any one of [1] to [8], wherein the total content of mud and sand in the solid fuel is 3% by mass or more.

[0046] This disclosure is not limited to the embodiments described above. For example, the waste materials used in the heating process are not limited to the first and second wastes, but one or more types of waste with different compositions, or materials other than waste, may be introduced into the heating furnace. [Examples]

[0047] The contents of this disclosure will be explained in more detail below with reference to examples and comparative examples. However, this disclosure is not limited to the examples described below.

[0048] (Comparative Examples 1-3) Shredder dust obtained from the market was crushed in a crusher to obtain the first waste (particle size: less than 22 mm). The composition of the first waste, determined by manual sorting, is shown in Table 1. Construction waste plastics obtained from the market were crushed in a crusher to obtain the second waste (particle size: less than 50 mm). The composition of the second waste, determined by manual sorting, is shown in Table 1. The proportion of thermoplastics in Table 1 is the sum of the proportions of fluff plastic, polyvinyl chloride, rigid plastic, expanded polystyrene, and polyurethane.

[0049] [Table 1]

[0050] A mixed raw material was prepared by mixing the first or second waste with commercially available pulverized coal (Dp50: 3.6 mm) in the mass ratio shown in Table 2. This mixed raw material was introduced into a heating furnace equipped with a lifter blade and heated while an inert gas was circulated. The heating rate was increased from room temperature to 200°C at a rate of 6°C / min, and from 200°C to 320°C at a rate of approximately 2°C / min. The rotation speed of the heating furnace was set to 1.9 rpm. The waste plastic contained in the mixed raw material melted and / or thermally decomposed, and the furnace temperature reached 350°C. After holding for 1 hour, heating was stopped and the material was allowed to cool, and the heat-treated material was removed from the heating furnace. In this way, solid fuels (heat-treated materials) of Comparative Examples 1 to 3 were obtained. The particle size of the solid fuel was examined using a sieve. The particle size distribution was as shown in Figure 2.

[0051] [Table 2]

[0052] Table 2 also shows the component ratios of the waste raw materials and the mixed raw materials. Comparing Comparative Example 1 and Comparative Example 2, as shown in Figure 2, Comparative Example 2, which used the second waste, had a smaller particle size of solid fuel than the first waste. This is due to the lower proportion of thermoplastic plastics and the higher total content of mud and sand in the second waste compared to the first waste. Comparative Example 3 had a smaller particle size of solid fuel than Comparative Example 1, despite containing less pulverized coal (half the amount in Comparative Example 1). These results confirm that the second waste has a higher anti-fusion effect than the first waste.

[0053] (Comparative Example 4, Examples 1 and 2) The first and second waste materials used in Comparative Examples 1-3, along with pulverized coal of a different variety than that used in Comparative Examples 1-3, were mixed in the mass ratios shown in Table 3 to prepare the mixed raw materials. This mixed raw material was introduced into a heating furnace equipped with the same lifter blades as in Comparative Examples 1-3, and heated while circulating inert gas. Heating under the same conditions as in Comparative Examples 1-3 yielded the heat-treated products of Comparative Example 4 and Examples 1 and 2. The particle size of the solid fuel was examined using a sieve in the same manner as in Comparative Examples 1-3.

[0054] Solid fuels were screened to determine the mass ratios for seven particle size ranges: less than 1.0 mm, 1.0 mm to less than 2.0 mm, 2.0 mm to less than 2.8 mm, 2.8 mm to less than 4.7 mm, 4.7 mm to less than 9.5 mm, 9.5 mm to less than 16 mm, and 16 mm or larger. The median value of each particle size range was considered to represent the mass ratio within that range, yielding seven data points. For the particle size ranges of less than 1.0 mm and 16 mm or larger, the respective mass ratios were considered to represent particle sizes of 1.0 mm and 16 mm. Using these seven data points, a quadratic function was found that yielded the correlation coefficient (r) closest to 1. Based on this quadratic function, the particle size at which the cumulative mass percentage from the smallest particle size side reached 50% by mass was defined as the average particle size (Dp50). The results are shown in Table 3.

[0055] [Table 3]

[0056] As shown in Table 3, although Examples 1 and 2 had a lower proportion of pulverized coal in the raw materials than Comparative Example 4, there was little coarsening of the heat-treated material. Figure 3(A) shows photographs of the solid fuel from Comparative Example 4, Figure 3(B) shows photographs of the solid fuel from Example 1, and Figure 3(C) shows photographs of the solid fuel from Example 2. The particle size of the solid fuel from Examples 1 and 2 tended to be larger than that of Comparative Example 4, but there were no extremely coarse particles. Furthermore, no fusion of thermoplastic plastics occurred inside the heating furnace, confirming that the solid fuel could be manufactured stably. [Explanation of symbols]

[0057] 10...Rotary kiln, 12...Kiln body, 14...Outer cylinder, 15,16...Rollers, 17...Hot gas flow path, 21...Gas inlet, 22...Gas outlet, 30...Outlet section, 32...Outlet section, 40...Cooler, 50...Inlet section, 51...Raw material, 53...Heated product, 100...Manufacturing equipment.

Claims

1. A method for producing solid fuel, comprising a heating step of heating waste raw materials including waste plastic in a heating furnace to thermally decompose at least a portion of the waste plastic, The aforementioned waste raw materials are The first waste includes thermoplastic plastics, and the second waste has a higher mass ratio of construction waste plastics than the first waste. A method for producing solid fuel, wherein in the heating step, the first waste and the second waste are introduced into the heating furnace together or separately.

2. The method for producing solid fuel according to claim 1, wherein the second waste has a higher total content of mud and sand than the first waste.

3. The method for producing solid fuel according to claim 1, wherein the total content of mud and sand in the waste raw material is 3% by mass or more.

4. Prior to the heating step, there is a mixing step of preparing a mixed raw material containing at least the first waste and the second waste, A method for producing solid fuel according to any one of claims 1 to 3, wherein the heating step involves introducing the mixed raw materials into the heating furnace.

5. The method for producing solid fuel according to claim 4, wherein the mixed raw materials contain pulverized coal, and the ratio of the second waste to the pulverized coal is 10% by mass or more.

6. The method for producing solid fuel according to claim 5, wherein the total content of the pulverized coal, mud, and sand in the mixed raw materials is 30% by mass or more.

7. The method for producing solid fuel according to claim 5, wherein the total content of the pulverized coal and the second waste in the mixed raw materials is 40% by mass or more.

8. A method for producing a solid fuel according to claim 1 or 2, wherein the total content of mud and sand in the solid fuel is 3% by mass or more.

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