Manufacturing method of solid fuel

Abstract

To provide a method for producing solid fuel that can suppress the fusion of waste plastics and subsequent coarsening of the heat-treated material when waste raw materials containing waste plastics are heated. [Solution] A method for producing solid fuel having 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 mainly containing thermoplastic plastic and a second waste mainly containing thermosetting plastic, and in the heating step, the first waste and the second waste are introduced into the heating furnace together or separately.

Description

Technical Field

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[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 including waste plastics have been studied (Patent Documents 1 to 3). In Patent Document 1, attempts have been made to produce solid fuel with reduced chlorine by heating waste to embrittle it, pulverizing it, and then performing air classification. By the way, when heating waste including waste plastics, 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 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a method for producing solid fuel capable of suppressing the fusion of waste plastics and the coarsening of the heat-treated product when heating a waste raw material including waste plastics.

Means for Solving the Problems

[0005] One aspect of the present 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 It includes a first waste containing thermoplastic plastic as the main component, and a second waste containing thermosetting plastic as the main component, 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 as the main component and a second waste containing thermosetting plastic as the main component are introduced into the heating furnace together or separately. It is thought that the thermosetting plastic or its pyrolysis products contained in the second waste adhere to the surface of the molten thermoplastic contained in the first waste introduced into the heating furnace. This is presumed to suppress the fusion and coarsening of the thermoplastic. Therefore, according to the above manufacturing method, the burden of crushing the heat-treated material is reduced, and fine solid fuel can be produced efficiently. Furthermore, according to the above manufacturing method, the amount of coal-derived anti-fusing agent can also be reduced. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a method for producing solid fuel that can suppress the fusion of waste plastics and subsequent coarsening of the heat-treated material when waste raw materials containing waste plastics are heated. [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 and 2. [Figure 3] This graph shows the particle size distribution of the solid fuels in Examples 1 and 2 and Comparative Examples 1 and 3. [Figure 4]This graph shows the particle size distribution of the solid fuels in Examples 1, 3, and 4 and Comparative Example 1. [Figure 5] (A) is a photograph of the solid fuel of Comparative Example 1, (B) is a photograph of the solid fuel of Example 3, (C) is a photograph of the solid fuel of Example 1, and (D) is a photograph of the solid fuel of Example 4. [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 plastic in a heating furnace to thermally decompose at least a portion of the waste plastic. The waste raw materials include a first waste containing thermoplastic plastic as the main component and a second waste containing thermosetting plastic as the main component.

[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, etc. From the viewpoint of obtaining heat-treated material with large particle size and from the viewpoint of obtaining solid fuel with high added value, the mass percentage of waste plastics in the waste raw materials may be 70% by mass or more, 80% by mass or more, or 90% by mass or more.

[0012] In this disclosure, "main component" refers to the component that is present in the largest amount by mass relative to the total. Therefore, the first waste has a higher content of thermoplastic plastics than thermosetting plastics. The second waste has a higher content of thermosetting plastics than thermoplastic plastics. The thermoplastic plastic content in the first waste may be 50% by mass or more, 65% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. Waste with a high thermoplastic plastic content tends to melt, fuse, and become coarser when heated. In this manufacturing method, since the waste raw material includes the second waste which contains thermosetting plastics as the main component, the coarsening of thermoplastic plastics can be suppressed.

[0013] The first waste may contain either or both fluff and container recycling residue. The first waste may also contain, as by-components, combustible materials such as thermosetting plastics, fibers, paper, cardboard, wood, leather, elastomers, and rubber, as well as non-combustible materials such as metals, ceramics, glass, sand, and stones. However, from the viewpoint of ensuring a sufficiently high calorific value for the solid fuel, the proportion of combustible materials in the first waste may be 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more.

[0014] Thermoplastic plastics are plastics manufactured using thermoplastic resins. Thermoplastic plastics may contain, 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 thermoplastic plastic is not particularly limited, and may be, for example, a foam, film-like, or granular form.

[0015] The particle size of the first waste may be less than 100 mm, less than 80 mm, or less than 60 mm. By this, it is possible to sufficiently reduce the coarse particles that may be generated by the fusion of thermoplastic plastics. In addition, the "particle size" in the present disclosure is based on the size of the mesh opening of the sieve.

[0016] The content of the thermosetting plastic in the second waste may be more than 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. The thermosetting plastic has an effect of suppressing the coarsening of the heat-treated product by adhering to the surface of the melt of the thermoplastic plastic.

[0017] In addition to the thermosetting plastic, the second waste may contain combustibles such as thermoplastic plastics, fibers, paper, cardboard, wood, leather, elastomers, and rubber, as well as incombustibles such as metals, ceramics, glass, sand, and stone. However, from the viewpoint of sufficiently increasing the calorie of the solid fuel, the ratio of the combustibles in the second waste may be 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more.

[0018] Thermosetting plastics are plastics manufactured using thermosetting resins. Thermosetting plastics may contain, 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, an adhesive, a foam, film-like, or granular form.

[0019] The particle size of the second waste may be less than 100 mm, less than 90 mm, or less than 80 mm. This makes it easier to adhere to the thermoplastic contained in the first waste with high uniformity. As a result, the fusion of the thermoplastic can be sufficiently suppressed, and the particle size of the heat-treated product can be made even smaller. From a similar perspective, it is preferable that the average particle size (Dp50) of the second waste is smaller than the average particle size (Dp50) of the first waste. These average particle sizes (Dp50) can be determined in the same manner as the average particle size (Dp50) of the heat-treated product.

[0020] The second waste may contain polyurethane. Polyurethane can sufficiently suppress the fusion and coarsening of the thermoplastic. The ratio of polyurethane to the total waste raw material may be 2% by mass or more, 4% by mass or more, 6% by mass or more, or 8% by mass or more. The ratio of polyurethane to the total waste raw material may be 30% by mass or less, 20% by mass or less, or 15% by mass or less from the perspective of suppressing the coarsening of the solid fuel. The range of the ratio of polyurethane to the total waste raw material may be 2 - 30% by mass.

[0021] The first waste and the second waste may be separately introduced into the heating furnace and mixed in the heating furnace, or may have a mixing step of preparing a mixed raw material containing at least the first waste and the second waste before the heating step of being heated in the heating furnace. In the waste raw material, the ratio of the second waste to the first waste may be 2% by mass or more, 4% by mass or more, 6% by mass or more, or 8% by mass or more from the perspective of sufficiently suppressing the fusion and coarsening of the thermoplastic. In the waste raw material, the ratio of the second waste to the first waste may be 40% by mass or less, 30% by mass or less, or 25% by mass or less from the perspective of suppressing the coarsening of the solid fuel. The range of the ratio of the second waste to the first waste may be 2 - 40% by mass.

[0022] In the mixing process, a mixed raw material containing the first waste, the second waste, and pulverized coal may be obtained. The mixed raw material thus obtained may be introduced into a heating furnace. Alternatively, the waste raw material containing the first waste and the 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 rotating or revolving screw conveyor, a kiln-type dryer, etc. The mass ratio of pulverized coal to waste raw material may be less than 1.0, less than 0.8, or less than 0.6. Since thermosetting plastics have the effect of suppressing the fusion of thermoplastic plastics inside the heating furnace, pulverized coal may not be used at all in the method for producing solid fuel of this embodiment.

[0023] The particle size of the waste material may be less than 100 mm, less than 80 mm, or less than 60 mm. This can sufficiently promote decarbonization. By reducing the particle size of the waste material, the miscibility of the first waste and the second waste is improved, and the particle size of the heat-treated material obtained in the heating furnace can be further reduced. Before the mixing process, a crushing process may be performed to crush the first waste and the 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 pulverizer. In the mixing process, the first waste and the second waste may be crushed while being mixed.

[0024] 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 the production of solid fuel with a high yield while sufficiently performing thermal decomposition and desalination of waste plastics. The inside of the heating furnace may be an inert gas atmosphere. The heating furnace may be, for example, a rotary kiln equipped with lifter blades.

[0025] The heat-treated material obtained in the heating process has suppressed coarsening and possesses a sufficiently small particle size. For example, in the heat-treated material, the mass ratio of coarse particles with a particle size of 16 mm or larger may be 30% by mass or less, 20% by mass or less, 10% by mass or less, or 5% by mass or less. The lower limit of the mass ratio of coarse particles with a particle size of 16 mm or larger may be 1% by mass. The mass ratio of coarse 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.

[0026] In the heat-treated material, the mass ratio of particles having a particle size of 5 mm or more and less than 16 mm may be 30 to 70% by mass, or 40 to 65% by mass. In the heat-treated material, the mass ratio of particles having a particle size of less than 5 mm may be 10% by mass or more, 15% by mass or more, or 20% by mass or more. Since the coarsening of such heat-treated material is sufficiently suppressed, the load on the grinding process can be reduced. In addition, the chlorine content is sufficiently reduced, which can increase the added value of the solid fuel.

[0027] The average particle size (Dp50) of the heat-treated material (solid fuel) may be 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 seven data points are obtained. Note that for the particle size ranges of less than 1.0 mm and 16 mm or more, the respective mass ratios are considered to have particle sizes of 1.0 mm and 16 mm. Using the seven data points, a quadratic function is found that has a correlation coefficient (r) closest to 1. Note that the mass ratio of particles smaller than 1.0 mm to those 16 mm or larger is considered to be the mass ratio of particles with a particle size of 1.0 mm to those with a particle size of 16 mm. Based on the calculated quadratic function, the particle size at which the cumulative mass ratio from the smaller particle size side becomes 50% by mass is defined as the average particle size (Dp50).

[0028] 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. The heat-treated material obtained in the heating process may be pulverized after cooling. Pulverization may be carried out, for example, using a mill.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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 fusion and coarsening of thermoplastics on the surface of thermoplastics. Therefore, the burden of crushing the heat-treated material can be reduced, and fine solid fuel can be efficiently manufactured. In addition, since it is possible to suppress the fusion of thermoplastics inside the heating furnace, the amount of coal-derived anti-fusion agent used can also be reduced. This can also promote decarbonization.

[0034] 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 It includes a first waste containing thermoplastic plastic as the main component, and a second waste containing thermosetting plastic as the main component, 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 thermosetting plastic contained in the second waste contains polyurethane. [3] The method for producing a solid fuel according to [2], wherein the ratio of polyurethane to the total waste material is 2 to 30% by mass. [4] The heating step is preceded by a mixing step of preparing a mixed raw material containing 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 in the mixing step, pulverized coal is mixed to prepare the mixed raw material containing the first waste, the second waste and the pulverized coal. [6] A method for producing solid fuel according to any one of [1] to [5], wherein the ratio of the second waste to the first waste in the waste raw material is 2 to 40% by mass. [7] A method for producing solid fuel according to any one of [1] to [6], wherein the content of the thermoplastic in the first waste is 65% by mass or more. [8] A method for producing solid fuel according to any one of [1] to [7], wherein the content of the thermosetting plastic in the second waste exceeds 50% by mass. [9] In the heating step, pulverized coal is introduced into the heating furnace along with the waste material. The mass ratio of the pulverized coal to the waste material is less than 1.0. The method for producing solid fuel according to any one of [1] to [8], wherein the heat-treated product obtained in the heating step has a mass ratio of coarse particles having a particle size of 16 mm or more of 30% by mass or less.

[0035] 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]

[0036] 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.

[0037] (Comparative Example 1) Waste mainly composed of fluff plastic was crushed in a crusher to obtain the first waste (particle size: <50 mm). The proportion of thermoplastic plastic (fluff) in this first waste, determined by manual sorting, was 95.2% by mass, and the proportion of fibers, paper, and wood chips was 4.8% by mass. This first waste was mixed with commercially available pulverized coal (Dp50: 3.6 mm) in a 1:1 mass ratio to prepare a mixed raw material. This mixed raw material was introduced into a heating furnace equipped with lifter blades 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 heating furnace rotation speed was set to 1.9 rpm. The plastic contained in the mixed raw material melted and 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 manner, a solid fuel (heat-treated product) for Comparative Example 1 was obtained. The particle size distribution of the solid fuel was examined using a sieve. The particle size distribution is shown in Figure 2.

[0038] (Comparative Example 2) Waste consisting mainly of fluff-like plastic, different from that used in Comparative Example 1, was crushed in a crusher to obtain the first waste (particle size: <50 mm). The proportion of thermoplastic plastic (fluff) in this first waste, determined by manual sorting, was 60.5% by mass, and the other compositions are shown in Table 1. This first waste and the pulverized coal used in Comparative Example 1 were mixed in a 1:1 mass ratio to prepare a mixed raw material. Except for using this mixed raw material, heating was carried out in a heating furnace in the same manner as in Comparative Example 1 to obtain the solid fuel (heat-treated product) of Comparative Example 2. The particle size distribution of the solid fuel was examined using a sieve. The particle size distribution is shown in Figure 2.

[0039] [Table 1]

[0040] As shown in Table 1, the compositional components of the first waste in Comparative Example 1 and the first waste in Comparative Example 2 were significantly different. As shown in Figure 2, the solid fuel in Comparative Example 1 had a larger particle size than the solid fuel in Comparative Example 2. This result indicates that the compositional components of the first waste affect the particle size of the solid fuel. Therefore, in order to investigate which components affect the particle size of the solid fuel, different waste components were added to the first waste in Comparative Example 1, and the change in the particle size of the solid fuel was examined.

[0041] (Example 1) The first waste material used in Comparative Example 1, granular polyurethane obtained by cutting commercially available polyurethane (particle size: approximately 20-30 mm, corresponding to the second waste material), and pulverized coal were mixed in a mass ratio of 89.3:10.7:100 to prepare a mixed raw material. Except for using this mixed raw material, the solid fuel (heat-treated product) of Example 1 was obtained by heating in a heating furnace in the same manner as in Comparative Example 1. The particle size distribution of the solid fuel was examined using a sieve. The average particle size (Dp50) was also determined from the particle size distribution. The results are shown in Table 2 and Figure 3. The method for deriving the average particle size (Dp50) is as described above.

[0042] (Example 2) The first waste material used in Comparative Example 1, granular rigid plastic (particle size: approximately 20 mm, corresponding to the second waste material) obtained by separating the first waste material and the waste material mainly composed of fluff-like plastic, and pulverized coal were mixed in a mass ratio of 89.3:10.7:100 to prepare a mixed raw material. The rigid plastic mainly contained thermoplastic plastic. Except for using this mixed raw material, the solid fuel (heat-treated product) of Example 2 was obtained by heating in a heating furnace in the same manner as in Comparative Example 1. The particle size of the solid fuel was examined using a sieve. The average particle size (Dp50) was also determined from the particle size distribution. The results are shown in Table 2 and Figure 3.

[0043] (Comparative Example 3) The first waste material used in Comparative Example 1, granular polystyrene foam (particle size: approximately 20-30 mm) obtained by cutting commercially available polystyrene foam, and pulverized coal were mixed in a mass ratio of 89.3:10.7:100 to create a mixed raw material. Except for using this mixed raw material, the process was carried out in a heating furnace in the same manner as in Comparative Example 1 to obtain the solid fuel (heat-treated product) of Comparative Example 3. The particle size of the solid fuel was examined using a sieve. The average particle size (Dp50) was also determined from the particle size distribution. The results are shown in Table 2 and Figure 3.

[0044] [Table 2]

[0045] Table 2 shows the ratio of components in the waste raw materials. Table 2 and Figure 3 also show the results for Comparative Example 1. As shown in Table 2 and Figure 3, it was confirmed that polyurethane, a thermosetting plastic, had the greatest effect in suppressing the coarsening of solid fuel. Next, the effect of the amount of polyurethane added was investigated.

[0046] (Example 3) The first waste material used in Comparative Example 1, the granular polyurethane material used in Example 1, and pulverized coal were mixed in a mass ratio of 94.5:5.5:100 to obtain a mixed raw material. Except for using this mixed raw material, the process was carried out in a heating furnace in the same manner as in Comparative Example 1 to obtain the solid fuel (heat-treated product) of Example 3. The particle size of the solid fuel was examined using a sieve. The results are shown in Table 3 and Figure 4.

[0047] (Example 4) The first waste material used in Comparative Example 1, the polyurethane granules used in Example 1, and pulverized coal were mixed in a mass ratio of 80:20:100 to obtain a mixed raw material. Except for using this mixed raw material, the process was carried out in a heating furnace in the same manner as in Comparative Example 1 to obtain the solid fuel (heat-treated product) of Example 4. The particle size of the solid fuel was examined using a sieve. The results are shown in Table 3 and Figure 4.

[0048] [Table 3]

[0049] Table 3 shows the ratio of components in the waste raw materials. Table 3 and Figure 4 also show the results for Comparative Example 1 and Example 1. Figure 5(A) shows photographs of the solid fuel from Comparative Example 1, Figure 5(B) from Example 3, Figure 5(C) from Example 1, and Figure 5(D) from Example 4. As shown in Table 3, Figure 4, and Figures 5(A)-(D), it was confirmed that Example 1, in which the proportion of polyurethane in the waste raw materials was 10.7% by mass, yielded the solid fuel with the smallest particle size. [Explanation of symbols]

[0050] 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 It includes a first waste containing thermoplastic plastic as the main component and a second waste containing thermosetting plastic as the main component, 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 claim 1, wherein the thermosetting plastic contained in the second waste includes polyurethane.

3. The method for producing a solid fuel according to claim 2, wherein the ratio of the polyurethane to the total waste material is 2 to 30% by mass.

4. Prior to the heating step, there is a mixing step of preparing a mixed raw material containing 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 mixing step involves mixing in pulverized coal to prepare the mixed raw material containing the first waste, the second waste, and the pulverized coal.

6. A method for producing solid fuel according to any one of claims 1 to 3, wherein the ratio of the second waste to the first waste in the waste raw material is 2 to 40% by mass.

7. A method for producing a solid fuel according to any one of claims 1 to 3, wherein the content of the thermoplastic in the first waste is 65% by mass or more.

8. A method for producing a solid fuel according to any one of claims 1 to 3, wherein the content of the thermosetting plastic in the second waste exceeds 50% by mass.

9. In the heating step, pulverized coal is introduced into the heating furnace along with the waste raw material. The mass ratio of the pulverized coal to the waste material is less than 1.

0. The method for producing solid fuel according to any one of claims 1 to 3, wherein the heat-treated product obtained in the heating step has a mass ratio of coarse particles having a particle size of 16 mm or more of 30% by mass or less.

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