JP7725112B1 - Solid fuel manufacturing method - Google Patents

Abstract

[Problem] To provide a method for producing solid fuel that can produce dechlorinated and torrefied solid fuel by shear heat from agitating blades without using external heating. [Solution] This method for producing solid fuel involves agitating waste plastics and an anti-adhesion material in a high-speed rotary mixer while heating them to over 180°C by shear heat from the agitating blades, and granulating them while dechlorinating and torrefying them, wherein the anti-adhesion material is at least one selected from biomass powder and granules, solid fuel, and oils with a flash point higher than the maximum temperature of the waste plastics and anti-adhesion material during granulation. [Selected Figure] Figure 1

Description

The present invention relates to a method for producing solid fuel using waste plastic as a raw material.

The 2015 G7 Summit raised the issue of marine litter and plastic waste as a global issue. To prevent illegal dumping of plastic waste resulting from undisposed sources, Japan doubled the amount of temporary storage capacity for plastic waste in 2019 and formulated the "Plastic Resource Circulation Strategy" in May of the same year. The "Plastic Resource Circulation Strategy" outlines a strategy for recycling plastic containers and packaging (plastic packaging) and non-plastic packaging waste generated by households at low cost and with low _CO2 emissions, achieving high resource recovery rates, including thermal recovery. It also calls for the elimination of illegal dumping, aiming for zero marine plastic emissions. The Ministry of the Environment's figures for illegal dumping in fiscal years 2020 and 2021 show that waste plastic, sludge, and wood chips are listed as combustible waste, excluding construction waste. Criticism has also been directed at greenhouse gas emissions generated when illegally dumping plastic waste resulting from marine plastic is also being focused on.

Meanwhile, technologies are known for recycling waste plastic and paper into solid fuels such as RPF (Refuse-derived paper and plastics densified fuel). In light of the increasing cost of industrial waste disposal and the resulting illegal dumping of waste plastics containing high levels of chlorine-containing polyvinyl chloride (PVC), which are considered unsuitable for use as fuel, the current requirement that waste plastics must have a chlorine content of 0.3% or less, as defined by JIS Z7311:2010 "Refuse-derived paper, plastics, and other solid fuels (RPF)," has been revised, and the RPF industry is now moving toward easing acceptance restrictions, allowing use of fuel with a chlorine content of 1% or less.

One proposed technology for dechlorinating high-chlorine-content waste plastics is a twin-screw dechlorination treatment device that uses external indirect heating. One example of such a dechlorination treatment device is a twin-screw dechlorination device (Patent Document 1). Patent Document 1 states, "Without an active mixing/kneading function, energy efficiency is poor and uniform dechlorination is not possible. In an embodiment of the invention, the molten waste plastic is heated by the heater and passes through the cylinder of the dechlorination device (external indirect heating), and the twin-screw rotating screws, which actively mix and knead the plastic, apply a shearing action to generate shear heat, allowing the molten waste plastic to be efficiently heated and thermally decomposed." However, no detailed data on shearing action and processing capacity is provided.

There has also been a report on waste plastic dechlorination technology using a twin-screw dechlorination device (see Non-Patent Document 1). The example in this report can be summarized as follows: "The residual chlorine concentration remains almost unchanged for residence times of 10 minutes or more. After water washing, general waste plastic with a chlorine content of 1.8 wt% is dechlorinated to a residual chlorine concentration of just over 0.8 wt% (about half the amount of chlorine added) through the shearing action of a twin-screw rotating screw with an outer diameter of 174 mm and a peripheral speed of approximately 0.37 m/s, which passes through a cylinder heated to a heating temperature of 310°C by external indirect heating and levels off for residence times of 10 minutes or more." However, no detailed data on processing capacity is provided.

Japanese Patent Application Laid-Open No. 2002-86447

Masayoshi Tokihisa et al., "Plastic Dechlorination Solid Fuel Production Equipment," Journal of the Japan Paper and Pulp Technology Association, Vol. 55, No. 5, pp. 82-88, May 2001

The objective of the present invention is to provide a method that can produce dechlorinated and torrefied granular solid fuel by shear heating of the stirring blades without using external heating.

While investigating methods for producing solid fuel from waste plastic, the inventors discovered that dechlorinated and semi-carbonized granular solid fuel can be produced by heating the waste plastic and anti-adhesion material to over 180°C using shear heat from the agitator blades in a high-speed rotary mixer and then granulating them, leading to the completion of the present invention.

That is, the present invention is as follows.
[1] A method for producing solid fuel in which waste plastics and anti-adhesion materials are stirred in a high-speed rotary mixer and heated to over 180°C by shear heat from the stirring blades, and granulated while undergoing dechlorination and semi-carbonization,
A method for producing solid fuel, characterized in that the anti-adhesion material is at least one selected from biomass powder, the solid fuel, and oil having a flash point higher than the maximum temperature of the waste plastic and anti-adhesion material during granulation.
[2] The method for producing a solid fuel according to the above [1], wherein the produced solid fuel has a chlorine content of 1.0 mass % or less.
[3] The method for producing a solid fuel according to [1] or [2] above, characterized in that the anti-adhesion material contains at least biomass powder and granules, and the biomass powder and granules are organic sludge powder and granules generated from a wastewater treatment facility.

[4] A method for producing solid fuel according to any one of [1] to [3] above, characterized in that the granulation involves melting waste plastics by shear heat from the stirring blades, dechlorinating and semi-carbonizing them, and then adding water to solidify and granulate the waste plastics.
[5] The method for producing a solid fuel according to any one of [1] to [4] above, characterized in that a purging treatment of air or an inert gas is carried out when heating to above 180°C by shear heat of the stirring blades of the high-speed rotary mixer.
[6] The method for producing a solid fuel according to the above [4], wherein the water used for the hydration contains a neutralizing agent for neutralizing chlorinated compounds.

[7] A method for producing a solid fuel according to any one of [1] to [6] above, characterized in that the produced solid fuel has a chlorine content of 1.0 mass% or less, a higher heating value of 25 MJ/kg or more, a moisture content of 5 mass% or less, and an ash content of 10 mass% or less, in accordance with the RPF quality standards.
[8] The method for producing a solid fuel according to any one of [1] to ^[7] above, characterized in that the produced solid fuel has a chlorine content of 1.0 mass% or less, a bulk density of 0.4 t/m3 or more, an average particle diameter _D50 of 10.0 mm or less, 90% or more of all particles having a particle size of 0.01 mm or more, and an angle of repose of 50° or less.
[9] The method for producing a solid fuel according to any one of [1] to [8] above, wherein the produced solid fuel has a sulfur content of 1% by mass or less.

[10] A granular solid fuel containing plastic, characterized in that the chlorine content is 1.0 mass% or less, the granular solid fuel complies with the RPF quality standards, has a higher heating value of 25 MJ/kg or more, a moisture content of 5 mass% or less, and an ash content of 10 mass% or less.
[11] A granular solid fuel containing plastic, characterized in that the chlorine content is 1.0 mass% or less, the bulk density is 0.4 t/m3 or ^more , the average particle diameter _D50 is 10.0 mm or less, 90% or more of all particles have a particle size of 0.01 mm or more, and the angle of repose is 50° or less.

The solid fuel production method of the present invention makes it possible to produce granular solid fuel that has been dechlorinated and torrefied by the shear heat of the stirring blades, without using external heating.

1 is an explanatory diagram of a method for producing solid fuel according to an embodiment of the present invention. FIG. 1 is an explanatory diagram of a high-speed rotary mixer used in the examples. FIG. 2 is a graph showing the cumulative undersize particle size distribution of the solid fuels obtained in Examples 2 and 3.

The solid fuel production method of the present invention involves stirring waste plastic and anti-adhesion material in a high-speed rotary mixer while heating them to over 180°C using shear heat from the stirring blades, resulting in granulation accompanied by dechlorination and semi-carbonization. The anti-adhesion material is at least one selected from biomass powder and granules, solid fuel, and oils with a flash point higher than the maximum temperature of the waste plastic and anti-adhesion material during granulation.

The solid fuel production method of the present invention heats waste plastics and specific anti-adhesion materials in a high-speed rotary mixer using shear heat from the mixing blades without using external heating, producing dechlorinated and semi-carbonized granular solid fuel. Furthermore, if the biomass powder contains sulfur-containing compounds, the sulfur components can be volatilized and removed (desulfurized) by thermal decomposition.

In addition, the solid fuel manufacturing method of the present invention melts and mixes waste plastic with an anti-adhesion material, preventing adhesion of the molten waste plastic and enabling granulation that involves dechlorination and semi-carbonization.

Furthermore, the solid fuel manufacturing method of the present invention allows for granulation regardless of whether water is added, and can produce solid fuel of equal or superior quality to solid fuel produced using conventional twin-screw dechlorination equipment with external heating.

Furthermore, the solid fuel production method of the present invention dechlorinates, desulfurizes, and semi-carbonizes waste plastics by direct heating caused by the powerful local shearing of the agitating blades of a high-speed rotary mixer, thereby realizing reduced _CO2 emissions through low power consumption and enabling efficient production of solid fuel with low initial and running costs.In other words, the solid fuel production method of the present invention has lower initial and running costs (power consumption) per processing capacity, as well as lower power consumption and _CO2 emissions, compared to production methods using conventional twin-screw dechlorination equipment with external heating, allowing for efficient production of solid fuel at low cost.

Patent Document 1 and Non-Patent Document 1 do not mention the processing capacity of screw-type dechlorination technology, but Non-Patent Document 1 states that "the residual chlorine concentration changes very little with a residence time of 10 minutes or more." The lower the screw rotation speed, the longer the residence time and the better the dechlorination performance, but the lower the processing capacity and the less direct heating caused by the shear of the screw, resulting in dechlorination relying more on external indirect heating as mentioned above, and the lower the efficiency of direct heating.

In contrast, the present invention has been evaluated in Example 3, which demonstrates that the granulation process is performed at a lower resin temperature with the same dechlorination rate as the dechlorination technology of Patent Document 1. At the same resin temperature, the present invention, which does not use external indirect heating, consumes less power for direct heating. As the resin temperature rises, the melt viscosity increases, increasing the power consumption for both drive components. Therefore, the present invention, which has a lower resin temperature than Patent Document 1, consumes less power for drive components.

Furthermore, when comparing the power consumption required for external indirect heating and screw drive in Patent Document 1 with the power consumption required for direct heating and drive of only the agitator blades of the present invention, the latter consumes less power for heating and drive. As will be explained later, the initial cost of the high-speed rotary mixer of the present invention is approximately 20% cheaper than the twin-screw system of Patent Document 1, given the same processing capacity.

[Waste plastic]
The waste plastics (waste plastics) to be treated in the present invention are not particularly limited as long as they can be treated using a high-speed rotary mixer, and examples thereof include recycled plastic container packaging (recyclable plastics). The form of the waste plastics may be in a discarded state or may be processed after disposal, with processed plastics being preferred. As processed waste plastics, crushed waste plastics are more preferred. The shape of the waste plastics may include various shapes such as fluff, beads, flakes, chips, powder, and pellets.

Examples of types of waste plastic include general-purpose waste plastics, such as PP (polypropylene), PE (polyethylene), PS (polystyrene), and PET (polyethylene terephthalate), which are the main components of plastic container recycling. The preferred waste plastics are those containing polyvinyl chloride (PVC), which is unsuitable for recycling and settles during wet gravity separation of plastic container recycling. The solid fuel manufacturing method of the present invention can recycle this polyvinyl chloride-containing plastic into solid fuel.

[Anti-adhesion material]
Examples of the anti-adhesion material of the present invention include biomass powder, solid fuel, and oil with a flash point higher than the maximum temperature (also called resin temperature) of the waste plastic and anti-adhesion material during granulation, and these may be mixed with the waste plastic alone or in combination. The addition of these anti-adhesion materials prevents the adhesion of molten waste plastic, enabling granulation accompanied by dechlorination and semi-carbonization.

(biomass powder)
The biomass powder or granule of the present invention is not particularly limited as long as it is volatile biomass that generates gases such as carbon monoxide and hydrogen when heated, or combustible biomass, and examples thereof include powder or granule of organic sludge generated from wastewater treatment facilities containing a large amount of organic matter, such as food factories, sewage treatment plants, paper mills, animal farms, etc. The biomass powder or granule of the present invention can also be applied to biomass that has a high chlorine or sulfur content and is therefore unsuitable for use as fuel and difficult to treat, such as bark, bamboo, organic sludge, and livestock manure.

For example, wastewater treatment organic sludge discharged from a material recycling processing plant that performs wet gravity separation of the container-recycling plastics, and polyvinyl chloride (PVC)-containing waste plastics that settle during the wet gravity separation, can be dechlorinated, desulfurized, and semi-carbonized to form a pelletized form in the high-speed rotary mixer, making it possible to effectively utilize them as a solid fuel instead of fossil fuels.This makes it possible to realize a zero-emission material recycling plant that does not require industrial waste treatment of polyvinyl chloride (PVC)-containing waste plastics and wastewater treatment organic sludge, contributing to low _CO2 emissions.

The biomass granular material of the present invention serves to suppress the melting and adhesion of waste plastics, improving the efficiency of dechlorination and desulfurization processes. Specifically, when the resin temperature rises and the waste plastics melt, the molten plastics adhere to the mixer due to their melting and adhesion, but cannot be heated by the local shear heat generated by the mixing blades. The melting and adhesion of waste plastics, which hinders dechlorination and desulfurization, is suppressed by mixing biomass granular material. When biomass granular material and molten waste plastics are mixed and stirred, the melting and adhesion decreases, and the stirred biomass granular material scrapes off the molten adhesion, suppressing melting and adhesion, and enabling granulation accompanied by dechlorination and semi-carbonization.

(solid fuel)
As the anti-adhesion material of the present invention, the solid fuel (granules) produced by the manufacturing method of the present invention can be used instead of biomass powder and granules. The solid fuel of the present invention can also be mixed with biomass powder and granules. The solid fuel of the present invention is semi-carbonized, which reduces its melting stickiness when heated, and is dechlorinated and desulfurized, making it useful as a substitute for biomass powder and granules. In other words, adding solid fuel prevents adhesion of molten waste plastics and enables granulation accompanied by dechlorination and semi-carbonization.

(oil)
As the anti-adhesion material of the present invention, instead of biomass powder or solid fuel, oil having a flash point higher than the maximum temperature of the waste plastic and anti-adhesion material during granulation (hereinafter, sometimes referred to as high flash point oil) can be used. Also, this high flash point oil can be mixed with biomass powder or solid fuel.

Adding oil with a flash point higher than the maximum temperature of the waste plastic and anti-adhesive material during granulation, such as soybean oil with a flash point of 330°C, can prevent adhesion and burning, similar to adding oil to a frying pan to prevent adhesion and burning. Adding this oil forms an oil film inside the mixer, providing lubrication and uniform heat conduction, preventing adhesion and burning and enabling granulation accompanied by dechlorination, desulfurization, and semi-carbonization. Furthermore, mixing waste plastic and high-flash-point oil can improve the higher heating value of the granulated fuel. Waste oil is preferred as the high-flash-point oil. Specifically, the flash point of the high-flash-point oil used should preferably be one that exceeds the maximum resin temperature for dechlorination and desulfurization. The maximum resin temperature is preferably a temperature that does not reduce yield. The maximum resin temperature varies depending on the components of the waste plastic being added, so it is not limited; however, for example, 300°C or below is preferred for waste plastic containers and packaging.

The amount of biomass powder and/or anti-adhesion material added to granulation involving dechlorination, desulfurization, and semi-carbonization is preferably large, as the adhesive strength increases as the resin temperature increases upon melting. Specifically, for example, when waste plastic and biomass powder are added simultaneously to a mixer, the amount is preferably such that the latter penetrates into the gaps between the former and the resulting volume remains the same after mixing. Similarly, when the solid fuel or high-flash-point oil according to the present invention is added simultaneously with the waste plastic, the amount is preferably such that the resulting volume remains the same after mixing.

The ratio of waste plastics and anti-adhesion materials (biomass powder, solid fuel, high flash point oil) to be added varies depending on their particle size and bulk density. For example, the maximum mass of organic sludge with a dry bulk density of 0.8 t/ ^{m3 and} an average particle size _D50 of 0.9 mm that can be added to a mass of waste plastics with a dry bulk density of 0.1 t/m3 to be crushed with a Φ20 mm screen is approximately 100%.
By adjusting the amount of anti-adhesion material added so that the volume does not increase after mixing, the volume of the molten material, which is the most reduced volume, can be maintained at 60 to 70 percent of the mixer's capacity. This ensures the amount of waste plastic added and the processing capacity, and also enables dechlorination within the time required to process the planned amount, ensuring the planned amount of dechlorination and desulfurization.

If there is room in the planned waste plastic processing capacity, this does not necessarily mean that the amount of anti-adhesion material added can be increased. The amount of anti-adhesion material added is preferably 1% by mass or more of the waste plastic, more preferably 5% by mass or more, and even more preferably 10% by mass or more. There is no particular upper limit, but it is preferably 1000% by mass or less of the waste plastic, more preferably 600% by mass or less, even more preferably 300% by mass or less, even more preferably 200% by mass or less, and most preferably 100% by mass or less.

When using biomass powder or solid fuel as the anti-adhesion material, there are no particular restrictions on the size (particle size) or moisture content of the anti-adhesion material fed into the mixer. The powerful shearing of the agitator blades rotating at high speed inside the mixer causes the material to be pulverized, reduced in volume, mixed, dried, kneaded, melted, and then dechlorinated, desulfurized, and torrefied. Therefore, it is preferable for the raw material fed into the mixer to have a small particle size and low moisture content. In other words, the smaller the particle size and the lower the moisture content of the anti-adhesion material, the shorter the pulverization, volume reduction, and drying time, ensuring more time for dechlorination within the time required to process the planned amount, and allowing the planned amount of dechlorination and desulfurization to be achieved.

Specifically, the particle size of the biomass powder and solid fuel is preferably 3.0 mm or less, more preferably 1.5 mm or less, and even more preferably 0.1 to 1.0 mm. The moisture content of the biomass powder and solid fuel is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

In the solid fuel production method of the present invention, the waste plastic melted by the strong local shear heat of the agitator blades coats the surface of the biomass powder and granules while kneading, while the fine powder is bonded by the melt adhesive force, and dechlorination, desulfurization, and semi-carbonization proceed, resulting in granulation to a granular particle size. For example, wastewater treatment organic sludge with a particle size of 0.09 mm or less, which accounts for 15% of the total mass, and wastewater treatment organic sludge with a particle size of 1.2 mm or more, which accounts for 40% of the total mass, are mixed with waste plastic with a dry bulk density of 0.15 t/ ^m3 to be crushed with a Φ20 mm screen, at a ratio of 10% by mass, and granulation is performed in a mixer, resulting in granulation to a granular particle size distribution as shown in Figure 3 (see Example 2).

[High-speed rotary mixer]
The high-speed rotary mixer directly heats the waste plastics and anti-adhesion materials placed inside it with the powerful shear heat generated by the high-speed rotation of the agitator blades, to a resin temperature of over 180°C as detected by a resin temperature sensor, enabling granulation accompanied by dechlorination, desulfurization, semi-carbonization, and granulation. Here, the resin temperature in this specification refers to the temperature of the mixture of waste plastics placed inside the high-speed rotary mixer and anti-adhesion materials (biomass powder, solid fuel, oil).

The solid fuel manufacturing method of the present invention melts plastics by directly heating them using the powerful local shear heat of the agitator blades, without the need for external or indirect heating, starting from a resin temperature of room temperature (equivalent to the ambient air temperature). This means that the temperature of the local shear area is higher than the resin temperature detected by the resin temperature sensor, and dechlorination, which involves thermal decomposition of chlorine compounds contained in waste plastics, can be carried out more efficiently and with less power consumption than Patent Document 1, which uses external indirect heating.

If the main components of waste plastics, such as PP (polypropylene), PE (polyethylene), PS (polystyrene), and PET (polyethylene terephthalate), contained in plastic containers, can be kept from thermal decomposition, a decrease in the yield of these main components can be prevented. It is known that PP, PE, PS, and PET undergo thermal decomposition at resin temperatures of 300°C or higher, so if the resin temperature is maintained at 300°C or lower during granulation, a decrease in the yield of these main components can be prevented. Since the resin temperature at which thermal decomposition occurs varies depending on the components of the waste plastic, there is no upper limit to the resin temperature, but the upper limit of the resin temperature is preferably 500°C or lower, more preferably 400°C or lower, and even more preferably 300°C or lower.

It is also well known that polyvinyl chloride (PVC) undergoes thermal decomposition at resin temperatures of 200°C or higher, and that the higher the resin temperature, the greater the amount of volatilization. However, in a granulation test (Example 2) using powdered waste plastic and organic sludge of the present invention, it was confirmed that direct heating from strong local shear heat caused hydrogen chloride (HCl) to be generated in the gas exhausting volatile gases at a resin temperature of 160°C, and that the hydrogen chloride concentration rapidly increased at resin temperatures of 180°C or higher, resulting in dechlorination. Therefore, when treating polyvinyl chloride (PVC), temperatures may be below 250°C or below 200°C.

In other words, while preventing a decrease in yield, the higher the resin temperature, the greater the amount of volatilization due to thermal decomposition, which increases the amount of chlorine removed and promotes torrefaction, so a higher resin temperature is desirable, but if it is too high, yield will decrease. For example, in the case of container recycling plastics, it is preferable to dechlorinate and torrefy the chlorine content to 1% or less at a resin temperature range of 180°C to 300°C, which does not reduce the yield of these main components. However, if the amount of chlorine removed is prioritized over a decrease in yield, there is no need to limit the upper limit of the resin temperature.

An example of a high-speed rotary mixer is a high-speed fluid mixer that mixes ingredients by rotating a stirring blade attached to the bottom of the container at high speed. Specific examples of high-speed fluid mixers include a Henschel mixer and a microspeed mixer.

The peripheral speed of the agitator blades during dechlorination and semi-carbonization treatments should be such that the resin can be heated to the above-mentioned temperature range by shear heat from the agitator blades. While it depends on factors such as the shape of the agitator blades, it is difficult to generalize. For example, in a Henschel mixer, the maximum speed is achieved and the greatest shear heat is generated at the outermost periphery of the agitator blades, which rotate at high speed. The maximum speed at the outermost periphery varies depending on the capacity of the mixer, but due to factors such as bearing durability, it is generally around 10 to 100 m/s, with 20 to 80 m/s being preferable, and 30 to 50 m/s being more preferable.

The smaller the mixer's capacity, the smaller the outer circumference of the agitator blades, and therefore the higher the agitator blade rotation speed (rpm). The higher the outer circumference speed, the greater the shear heat generated. By mixing at such speeds, the waste plastic (and anti-adhesion material) in the vertical container is subjected to the strong shear force of the agitator blades rotating at high speed, generating strong local shear heat that directly heats the waste plastic (and anti-adhesion material).

High-speed flow mixers such as Henschel mixers can perform granulation involving dechlorination, desulfurization, torrefaction, and granulation with low power consumption and high efficiency by using direct heating through the powerful local shear of rapidly rotating agitating blades rather than external indirect heating using an electric heater or other device that heats through the mixer walls. The solid fuel production method of the present invention does not require external indirect heating, but it is possible to supplement direct heating through powerful local shear heat with external indirect heating to increase the granulation processing capacity for dechlorination, desulfurization, and torrefaction, as well as the amount of dechlorination and desulfurization.

If the amount of chlorine removed by granulation using direct heating due to strong local shear heat and supplemented by external indirect heating is the same as the amount of chlorine removed by granulation using external indirect heating through the cylinder of a twin-screw dechlorination device such as that described in Patent Document 1 and direct heating due to local low shear heat, the former (the present invention) will consume less power and be more efficient.

In the solid fuel production method of the present invention, the resin temperature exceeds 180°C due to localized direct heating caused by the powerful shear heat generated by the high-speed rotating agitator blades. This melts the waste plastic and thermally decomposes chlorine-containing compounds, such as polyvinyl chloride (PVC), contained in the waste plastic, thereby volatilizing and removing the chlorine components (dechlorination). Furthermore, when biomass powders, such as organic sludge, contain sulfur-containing compounds, the sulfur-containing compounds can be thermally decomposed to volatilize and remove the sulfur components (desulfurization). In a granulation test (Example 2) using waste plastic and organic sludge, the hydrogen chloride (HCl) and sulfur oxide ( _SO2 ) concentrations in the exhaust gas rapidly increased from a resin temperature of 180°C due to the powerful localized shear heat generated by the high-speed rotating agitator blades, resulting in desulfurization. Furthermore, the solid fuel production method of the present invention can thermally decompose and volatilize organic biomass powders, converting them into a carbon-rich substance (semi-carbonization).

The more waste plastic is put into the mixer (filling amount), the higher the density of the waste plastic near the local area where it comes into contact with the agitator blades, allowing more of the waste plastic to be sheared. At the same time, the high-density waste plastic flowing through the mixer due to the agitator blades comes into contact with the mixer's inner walls, increasing resistance and increasing local shear force. As a result, shear heat due to direct heating increases, the resin temperature rises more quickly over time, and processing capacity improves.

The mixer is a batch-type process that uses high-speed rotating agitator blades to crush, reduce volume, and mix materials, while also directly heating them to the extent that they are dried, kneaded, and melted using powerful local shear heat, thereby dechlorinating, desulfurizing, and semi-carbonizing the materials and granulating them.

As mentioned above, the amount that can be fed into the mixer should preferably be such that the volume of the molten material, which will reduce the volume the most, is 60-70% of the mixer's capacity. In one-cycle batch processing, if the molten material volume is less than 60-70% of the mixer's capacity in a single feeding, it is preferable to feed the waste plastic and anti-adhesion material two or more times and perform batch processing at that 60-70% volume.

[Efficient dechlorination, desulfurization, and torrefaction, and production method for granular solid fuel]
The high-speed rotary mixer uses a batch processing method in which waste plastics are pulverized, reduced in volume, and mixed while being agitated by strong local shearing at the points where they come into contact with the agitating blades, and also directly heated to the extent that they are dried, kneaded, and melted by strong local shear heating, thereby carrying out dechlorination, desulfurization, and semi-carbonization, but a continuous processing method is also possible. In the production method of the present invention, it is preferable to use multiple batch processing type high-speed rotary mixers and stagger the timing of dechlorination, which consumes the most power in one batch processing, to reduce the maximum power consumption and perform processing efficiently.

High-speed rotary mixers can control the rotation speed by driving a motor via an inverter to rotate the agitator blades. In Example 2 of the present invention, it was confirmed that the higher the current value of the motor that rotates the mixer's agitator blades, the stronger the shear force of the agitator blades, raising the resin temperature and improving dechlorination and desulfurization performance. In Example 3 of the present invention, by operating the motor at a current value as close as possible to the rated current value, high processing capacity and high dechlorination and desulfurization rates were possible. It was also confirmed that even if the rotation speed of the agitator blades decreases, efficient processing capacity can be maintained as long as the current value is close to the rated current, and semi-carbonized granules can be produced through the dechlorination and desulfurization processes.

Furthermore, slowing the rotation speed of the agitator blades weakens the shear force, lowering the resin temperature and motor current. Therefore, slowing the rotation speed reduces the motor current and prevents the motor from overloading.

If the resin temperature is too low, increasing the rotation speed will increase the resin temperature and motor current. By adjusting the rotation speed, the resin temperature and motor current can be controlled, allowing the motor to operate as close to the rated current as possible. This achieves the highest processing capacity and dechlorination and desulfurization processing, enabling highly efficient processing.

(Air or inert gas purging)
When heating to temperatures above 180°C due to shear heat from the agitator blades of a high-speed rotary mixer, it is preferable to perform a purging treatment with air or an inert gas. The purging treatment not only adjusts the exhaust temperature but also the concentration of HCl and other substances volatilized by dechlorination and desulfurization and filling the mixer. High concentrations of HCl and other substances in the mixer can cause corrosion problems in the equipment, so the purging rate is preferably as high as possible. The purging rate varies depending on the mixer capacity and the amount of dechlorination and desulfurization, so it cannot be generally limited. However, a ventilation rate of approximately 1x the mixer capacity per minute is preferable; for example, if the mixer capacity is 20 L, a room-temperature purging rate of approximately 20 L/min or more is preferable. Instead of air, an inert gas such as nitrogen can be used as the gas used for the treatment. Using an inert gas is safer because it prevents fires due to high-temperature problems such as resin temperature increases.

Strengthening dechlorination and desulfurization generates large amounts of acidic gases such as HCl and _SO2 , which corrode metal machinery inside the mixer and exhaust pipe, resulting in breakdowns and other problems. Purging with air or inert gas can dilute the acidic gas concentration and reduce the risk of corrosion problems, but it also lowers the temperature of the exhaust gas that evaporates inside the mixer and is exhausted. The temperature range for dechlorination and desulfurization exceeds the dew point of HCl and _SO2 , approximately 120°C, at which corrosion accelerates, so corrosiveness in the dechlorination temperature range is suppressed.

In order to reduce the risk of corrosion by purging with air or inert gas, it is preferable not only to lower the concentration of acidic gas components as much as possible, but also to adjust the purge amount so that the exhaust temperature does not fall below the dew point of HCl and _SO2 . The correlation between the purge amount and the exhaust temperature varies depending on the mixer capacity, the amount of resin introduced, the rotation speed of the agitator blades, the resin temperature, the motor rating, etc., and therefore cannot be generally limited. For example, in Example 3, the minimum exhaust temperature during dechlorination was 160°C when the room temperature purge amount was 1.25 times the mixer capacity per minute, and the maximum exhaust temperature during dechlorination was 234°C when it was 2.75 times the mixer capacity.

(Water addition treatment)
The hydrophobic resin heated to a high temperature after dechlorination, desulfurization, semi-carbonization, and granulation in a high-speed rotary mixer is preferably rapidly cooled by adding water while stirring, like hot oil exploding violently, and then solidified and granulated while being pulverized. That is, the granulation is preferably carried out by melting the waste plastic to dechlorinate and semi-carbonize it using shear heat from the stirring blades, and then adding water to solidify and granulate the waste plastic. This shortens the granulation time and enables more efficient granulation compared to granulation without adding water, as in Example 2 of the present invention.

In addition, at the same time as the water expands 1,700 times in one go and the resulting steam is sprayed, the thermally expanded metal mixer contracts all at once, and deposits adhering to the mixer's inner walls are removed, just as pouring water on a burnt frying pan instantly removes the burnt food. If water-soluble chlorine or sulfur compounds are contained in waste plastics and anti-adhesion materials that have been subjected to direct heating treatment using strong local shear heating, these can be dissolved in the treated water and discharged together with the water. After the water treatment, the waste typically undergoes solid-liquid separation and drying processes, and the solid fuel is recovered with the water-soluble chlorine and sulfur compounds dechlorinated and desulfurized.

The treated water used for hydration may contain a neutralizing agent that neutralizes dissolved chloride compounds such as hydrogen chloride and sodium chloride. A specific example of a neutralizing agent is caustic soda.

The more water is added, the smaller the granule size will be, improving cleaning performance against water-soluble inorganic chlorine and redeposited HCl, as well as melt-adherent removal performance, so a higher amount is preferable. However, if too much water is added, the burden on subsequent processes of cleaning, solid-liquid separation, drying, and wastewater treatment will increase, so it is preferable to add water in an amount that is sufficient for cleaning, solid-liquid separation, drying, and wastewater treatment, plus the evaporated mass.

The amount of evaporation varies depending on factors such as the mixer capacity and the temperature of the resin to which water is added, so it is not possible to make a generalized limit, but the mass added when the resin temperature is around 250°C (the sum of the mass of resin and the mass of biomass powder, etc.) is a good guide for the evaporation mass. Furthermore, since water can be added in an emergency if the resin temperature becomes abnormally high, the water adding device is also suitable as a safety device for preventing fires, etc. From the perspective of promoting the process and removing deposits from inside the mixer, the amount of water added is preferably 50% by mass or more of the waste plastic, more preferably 100% by mass or more, and even more preferably 200% by mass or more. The upper limit is preferably 800% by mass or less.

[Low-cost, efficient dechlorination, desulfurization, torrefaction, and granular solid fuel production equipment]
When waste plastics and anti-adhesion materials that have been heat-treated using shear heat contain small amounts of water-soluble chlorine compounds, sulfur compounds, or redeposited HCl, adding less water makes it possible to treat the granulated product without affecting its chlorine, sulfur, particle size, or moisture content. This allows for the performance of washing, solid-liquid separation, and drying processes to be reduced, or for these facilities to be omitted and solid fuel to be recovered directly. As a result, initial and running costs related to wastewater treatment can be reduced, and _{CO2 emissions} can be reduced by reducing power consumption.

This dechlorination, desulfurization, and torrefaction granulation equipment uses a high-speed rotary mixer with an amount of water added that eliminates the need for wastewater treatment, and directly heats the wastewater using powerful local shear heat.When installed in the above-mentioned zero-emission material recycling plant, it can replace the granulation equipment of the waste plastic dechlorination treatment plant described in Patent Document 1, which uses a low-shear force twin-screw system with external indirect heating through a cylinder.However, the former granulation equipment (this invention) has the same processing capacity, is about 20% cheaper in initial cost, and produces solid fuel with the same dechlorination ability to a residual chlorine content of 1% or less, with lower running costs and lower _CO2 emissions due to lower power consumption due to lower resin temperature.Furthermore, the latter does not form a zero-emission plant because it treats organic sludge from wastewater treatment as industrial waste.

[Unexpected semi-carbonized granule formation during dechlorination and desulfurization treatment using a high-speed rotary mixer (Example 2)]
As mentioned above, PP, PE, PS, and PET do not undergo thermal decomposition or volatilization unless the resin temperature is above 300°C, whereas polyvinyl chloride (PVC) begins thermal decomposition, volatilization, and carbonization at resin temperatures above 200°C. 87.3% by mass of waste plastic containers and packaging (81.1% PP, PE, PS, and PET blend, 3.8% ash, 2.4% PVC), 8.0% by mass of organic sludge (4.0% ash), and 4.7% soybean oil (flash point 330°C, lower than the ignition point) were added to a mixer. Due to the strong local shear heat generated by the high-speed rotating agitator blades, dechlorination and desulfurization proceeded even at resin temperatures below 258°C, resulting in loss of melt adhesion. As a result, the current value of the agitator motor decreased, and the resin temperature dropped to a range where dechlorination was not possible, so granulation was performed without adding water. The resulting black granular product, as shown in Figure 3, was obtained.

The amount of volatilization of the resulting granules was analyzed according to industrial analysis (JIS M8812), revealing that 28.5% of the mass input to the mixer dry had volatilized, resulting in semi-carbonized granules.

As mentioned above, the amount of polyvinyl chloride (PVC) and organic sludge other than ash that volatilizes at a resin temperature of 258°C or less should be small, at about 6.4% by mass, but unexpected semi-carbonized granulation was achieved, with volatilization at about four times the amount. Furthermore, in this granulation test, we expected to produce glass granules with an average particle size _D50 of about 1 to 2 cm by adding water in a semi-molten state at a resin temperature before the resin melts in a similar mixer, but in fact we were able to produce granules with a granular particle size without adding water, as shown in Figure 3.
As shown in the results of Example 2 of the present invention, the unexpected formation of semi-carbonized granules was confirmed as a result of the dechlorination and desulfurization treatment using a high-speed rotary mixer.

[Dechlorination, desulfurization, torrefaction, granular solid fuel]
According to the solid fuel production method of the present invention, it is possible to produce a solid fuel having a chlorine content of 1.0% or less, a bulk density of 0.4 t/m3 or ^more , an average particle diameter _D50 of 10.0 mm or less, 90% or more of all particles having a particle size of 0.01 mm or more, and an angle of repose of 50° or less. Furthermore, according to the solid fuel production method of the present invention, it is possible to produce a solid fuel having a chlorine content of 1.0% by mass or less, a higher heating value of 25 MJ/kg or more, a moisture content of 5% by mass or less, and an ash content of 10% by mass or less, which comply with the RPF quality standards. Furthermore, according to the solid fuel production method of the present invention, it is possible to produce a solid fuel having a sulfur content of 1% or less.

The granular solid fuel of the present invention will now be described.
The granular solid fuel of the present invention is a granular solid fuel containing plastic, characterized in that it has a chlorine content of 1.0 mass% or less, a bulk density of 0.4 t/ ^m3 or more, an average particle diameter _D50 of 10.0 mm or less, 90% or more of all particles having a particle size of 0.01 mm or more, and an angle of repose of 50° or less.

The chlorine content of the granular solid fuel of the present invention is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, and even more preferably 0.6% by mass or less. In the present invention, the chlorine content of the solid fuel can be reduced by efficiently raising the resin temperature at low cost. Furthermore, the bulk density is 0.4 t/ ^m3 or more, preferably 0.5 t/ ^m3 or more, more preferably 0.6 t/ ^m3 or more, and even more preferably 0.7 t/ ^m3 or more. By having the bulk density in this range, transportation and handling costs can be reduced. Furthermore, the average particle diameter _D50 is 10.0 mm or less _, preferably 5.0 mm or less, more preferably 1.0 mm or less, and even more preferably 0.6 mm or less. By having the average particle diameter _D50 in this range, combustibility and coal co-firing ability are improved. Furthermore, the particle size is 0.01 mm or larger for 90% or more of the total particles, preferably 0.05 mm or larger, more preferably 0.08 mm or larger, and even more preferably 0.1 mm or larger. By keeping the particle size within this range, scattering and dust explosions can be suppressed. Furthermore, the angle of repose is preferably 50° or smaller, more preferably 40° or smaller. By keeping the angle of repose within this range, the flow path of the device is less likely to be clogged and transport is easier. Regarding sulfur content, although there are no established standards for the sulfur content of solid fuels such as RPF, a sulfur content testing method for waste-derived fuels is established in JIS Z 7302-7, and this measurement method can be used to manage the sulfur content so that it complies with the sulfur content regulations of the shipping destination. For example, Fukuoka City has measures regarding the use of petroleum-based fuels with a sulfur content standard of 1.0% or less. The sulfur content of the granular solid fuel of the present invention can be 1.0% or less.

The solid fuel produced in the examples of the present invention has a particle size of approximately 0.1 mm or more, resulting in almost no scattering of fine powder, excellent handling, and reduced risk of dust explosions. Furthermore, despite its angle of repose being comparable to that of commercially available RPF pellets (particle size diameter 6-40 mm x length 2-3 times the diameter, approximately 30-40°, bulk density 0.3-0.5 t/ ^m³ ), its small particle size makes it less likely to form bridges between particles at tank outlets, etc., and facilitates transportation by equipment. Furthermore, its bulk density of 0.9 t/ ^m³ is higher than that of commercially available RPF pellets, which have a bulk density of 0.3-0.5 t/ ^m³ , thereby reducing transportation and handling costs. Furthermore, as a fuel, its particle size is smaller than that of commercially available RPF pellets, making it easier to inject into a combustion furnace and allowing for rapid combustion. Furthermore, biomass powder can be easily mixed with coal, and by torrefying the powder, its energy density per unit weight increases, its calorific value approaches that of coal, and its water resistance improves. This makes it easier to crush, and it can be easily mixed with pulverized coal. As a result, handling for storage, transportation, and combustion improves, and the ratio of mixed coal combustion increases, contributing to lower _CO2 emissions and lower costs.
Due to the above characteristics, the solid fuel manufacturing method of the present invention can produce granular solid fuel that is equivalent to or better than the currently available RPF solid fuel and is superior in terms of quality and functionality, and can be used as an alternative fuel to heavy oil, coal, etc.

[Compatible with the quality of solid fuels such as RPF]
The solid fuel manufacturing method of the present invention can produce granular solid fuel of quality specified in the RPF quality standard. Specifically, by blending waste plastic, biomass powder, and oil that conform to the RPF quality specified in JIS Z 7311:2010 "Solidified Fuel from Waste Paper, Plastic, etc. (RPF)," it is possible to produce solid fuel that conforms to the specified RPF quality, which is a higher heating value of 25 MJ/kg or more, a moisture content of 5% by mass or less, and an ash content of 10% by mass or less. For blends that conform to RPF quality, it is preferable to use raw materials with as little ash as possible, which affects the higher heating value. The lower the ash content, the higher the higher heating value, and the longer the life of the mixer's agitator blades and other components due to wear. Regarding wear, we note that increasing the hardness of the agitator blades and the interior of the mixer chamber, which come into contact with the waste plastic and biomass powder, by quenching them, can extend the life of the components.

In the examples, organic sludge from wastewater treatment that has been subjected to compost fermentation (ash content 50.4% by mass, higher heating value 11.2 MJ/kg), which is readily available and readily available, was used as the biomass powder. However, if organic sludge from food factory wastewater treatment (ash content 14.6% by mass, 17.0 MJ/kg) were used, the amount of sludge that conforms to RPF quality could be doubled. Furthermore, if wood-based biomass powder, which has low ash content and high higher heating value, is used, the amount of biomass powder that conforms to RPF quality can be increased more than organic sludge. This does not apply if the quality of the solid fuel required by the destination does not require compliance with RPF quality.

An outline of a method for producing a solid fuel according to an embodiment of the present invention is shown in FIG.
Solid fuel was produced using the high-speed fluid mixer shown in Figure 2. The top of the vessel 2 of the high-speed fluid mixer (high-speed rotary mixer) 1 is equipped with a raw material inlet 3, an exhaust outlet 4, a water-adding nozzle 5 for spraying treated water, and an air purge nozzle 6 for spraying air or inert gas during dechlorination. The bottom of the vessel 2 is equipped with upper and lower impellers 7 and a discharge valve 8. A resin temperature sensor 9 for detecting the resin temperature is also installed within the vessel 2. Furthermore, an exhaust temperature sensor 10 installed at the exhaust outlet detects the temperature of the exhaust gas. The black arrows in the figure indicate the movement of the treated material within the device.

Table 1 shows an overview of the test conditions.

Specifically, the following tests were carried out and evaluated.
The raw material waste plastic (resin) used was sediment from container recycling plastics (mainly a mixture of PP, PE, PS, and PET (92.8% by mass), ash content 4.4% by mass DB, PVC 2.8% by mass (equivalent value of chlorine content 1.57% by mass DB)).
Wastewater treatment organic sludge (ash content 50.4 mass% DB, chlorine content 1.13 mass% DB, sulfur content 0.61 mass% DB) was used as the raw material biomass powder.
As the raw material oil, soybean oil (chlorine content <0.02 mass % DB, sulfur content <0.02 mass % DB, flash point 330°C) was used.

Sediment and organic sludge from container recycling plastics were fed into a high-speed fluid mixer, where they were fluidized and stirred by high-speed rotating impellers with a maximum tip speed of 56 m/s, while being pulverized, reduced in volume, and mixed. They were also directly heated using only powerful local shear heating to the extent that they dried, kneaded, and melted, resulting in dechlorination, desulfurization, and semi-carbonization, followed by granulation. While the mixer was operating, the water vapor, chlorine-based gases, and sulfur-based gases generated were treated as safe exhaust gases by exhaust gas cleaning equipment such as wet scrubbers, which removed the chlorine and sulfur. Air purging was performed during this dechlorination process. The motor was driven via an inverter, and the rotation speed was adjusted.

[Evaluation of Example 2: Unexpected semi-carbonized granule formation due to dechlorination and desulfurization treatment using a high-speed rotary mixer]
2 kg-wet polyvinyl chloride (PVC)-containing resin, 0.2 kg-wet chlorine- and sulfur-containing organic sludge, and 0.1 kg soybean oil were charged into a mixer. Direct heating by the agitator blades alone melted the resin, and once the resin temperature exceeded approximately 160°C, the chlorine contained in the resin and the sulfur contained in the organic sludge thermally decomposed, generating hydrogen chloride (HCl) and sulfur dioxide (SO ₂ ), which were then vented. At resin temperatures above 180°C, the concentrations of hydrogen chloride and sulfur dioxide rapidly increased, indicating dechlorination and desulfurization. As the temperature of the molten resin increased, the concentrations of hydrogen chloride and sulfur dioxide increased. At a maximum resin temperature of 258°C, dechlorination and desulfurization occurred, carbonization of the resin progressed, decreasing shear resistance. The resin temperature decreased without the addition of water, producing a semi-carbonized, black, granular product (dry bulk density 0.92 t/m ³ , dry angle of repose 35°).

An air purge of 60 L/min during dechlorination reduced the hydrogen chloride and sulfur dioxide concentrations inside the mixer chamber and in the exhaust, and the exhaust temperature during dechlorination remained above 150°C, which suppresses dew-point corrosion. The curves for motor current, resin temperature, and exhaust concentrations (hydrochloric acid, sulfur dioxide) each showed a correlated increase and decrease.

As shown in FIG. 3, the cumulative undersieve particle size distribution of the granular solid fuel granulated without adding water showed that the granulation was larger than the particle size of the powder, with a particle size of approximately 0.1 mm to 1.2 mm (approximately 90% by mass undersieve) and an average particle size of 0.57 mm-D ₅₀ .

While there are no established methods or standard values for calculating the degree of torrefaction, the material was torrefied to an index degree of torrefaction (dry volatilization amount after treatment / dry volatilization amount before treatment) of 32.0% by mass. At resin temperatures below 258°C, only about 6.4% by mass of the dry input amount (PVC, organic sludge excluding ash) should have volatilized, but in fact 28.5% by mass of the dry input amount volatilized. The amounts of volatilization before and after treatment were analyzed in accordance with JIS M 8812, an industrial analysis standard useful for the Refuse-Derived Fuel Testing Method (JIS Z 7302).

[Example 3 Evaluation: Granulation and washing method and granule properties with equivalent dechlorination rate at lower resin temperature compared to Patent Document 1 and Non-Patent Document 1]
Three kg of polyvinyl chloride (PVC)-containing resin (2 kg + 1 kg added twice) and 1.2 kg of chlorine- and sulfur-containing organic sludge were charged into a mixer, where dechlorination, desulfurization, semi-carbonization, and granulation were performed using direct heating solely from the shear heat of the agitator blades. Adding an extra 6 L of water during agitation (cooling solidification, melting adhesion removal, chlorine and sulfur washing) produced semi-carbonized black granular granules (dry bulk density 0.88 t/ ^m3 , dry angle of repose 35°). At a maximum resin temperature of 280°C, the chlorine content decreased from 1.45% D.B. to 0.68% D.B. (index dechlorination rate 53%) and the sulfur content decreased from 0.16% D.B. to 0.068% D.B. (index desulfurization rate 56%). There was virtually no adhesion inside the mixer chamber or on the agitator blades.

Indicated dechlorination/desulfurization rate = (amount of chlorine/sulfur added - amount of chlorine/sulfur added from solid fuel) / amount of chlorine/sulfur added

Air purging during dechlorination controls the hydrogen chloride and sulfur dioxide concentrations inside the mixer chamber and in the exhaust, as well as the exhaust temperature. The exhaust temperature during dechlorination remained above 150°C, which suppresses dew-point corrosion. By adjusting the mixing blade motor frequency, the correlated resin temperature and motor current value could be controlled, preventing the motor from shutting down due to overload. Dechlorination, desulfurization, semi-carbonization, water addition, and granulation were performed.

After adding a large amount of water and stirring and granulating, the granulated product was discharged in a mixed state with the added water. The chlorine and other substances contained in the granulated product were washed away by solid-liquid separation, and when the water quality of the separated liquid was measured, it showed an acidity similar to that of HCl.
The liquid after washing with water and solid-liquid separation had a pH of 5.0 (acidic) and a total chlorine content of 4.8 mg/L.

As shown in FIG. 3, the cumulative undersieve particle size distribution of the granular granules produced was larger than the powder particle size, with a particle size of approximately 0.1 mm to 1.2 mm (approximately 85% by mass undersieve) and an average particle size of 0.56 mm-D ₅₀ .

[Comparative evaluation of Example 1 and Example 2: Higher input amount leads to higher shear heat]
With the same input materials, blending ratio, and agitator blade rotation speed, the processing time from the start of operation to the maximum resin temperature (direct heating processing using only agitator blade shear heat) was 1 hour 54 minutes for Example 1 and 45 minutes for Example 2. Example 2, which had 1.33 times the input amount of Test 22, was 69 minutes (61%) shorter than Example 1, which means that the shear heat increases when the input amount is large.

[Comparative evaluation of Example 2 with Examples 4 and 5: Effect of adding water and increasing the amount of organic sludge to prevent melting and adhesion]
The contribution to preventing melting and adhesion due to an increase in the amount of organic sludge was demonstrated from the state of melting and adhesion inside the mixer and on the agitator blades after granulation in Examples 2 and 4. Furthermore, the effect of adding water to remove adhered matter was demonstrated from the state of melting and adhesion inside the mixer and on the agitator blades after granulation in Examples 2 and 5.

The solid fuel produced by the method of the present invention can be used as an alternative fuel to heavy oil and coal, and is therefore industrially useful, complying not only with the Containers and Packaging Recycling Law and the Plastic Resource Recycling Strategy, but also with the Basic Energy Plan and the Feed-in Tariff Scheme.

REFERENCE SIGNS LIST 1 High-speed rotary mixer 2 Container 3 Feeding port 4 Exhaust port 5 Water addition nozzle 6 Air purge nozzle 7 Mixing blade 8 Discharge valve 9 Resin temperature sensor 10 Exhaust temperature sensor

Claims (11)

A method for producing solid fuel, comprising the steps of: stirring waste plastics and anti-adhesion material in a high-speed rotary mixer; heating the waste plastics and anti-adhesion material to a temperature of over 180°C by shear heat generated by stirring blades; and granulating the waste plastics and anti-adhesion material while dechlorinating and semi-carbonizing the waste plastics;
A method for producing solid fuel, characterized in that the anti-adhesion material is at least one selected from biomass powder, the solid fuel, and oil having a flash point higher than the maximum temperature of the waste plastic and anti-adhesion material during granulation. The method for producing solid fuel according to claim 1, characterized in that the produced solid fuel has a chlorine content of 1.0 mass% or less. The method for producing solid fuel described in claim 1, characterized in that the anti-adhesion material contains at least biomass powder and granules, and the biomass powder and granules are organic sludge powder and granules generated from wastewater treatment facilities. The method for producing solid fuel described in claim 2, characterized in that the anti-adhesion material contains at least biomass powder and granules, and the biomass powder and granules are organic sludge powder and granules generated from wastewater treatment facilities. A method for producing solid fuel according to any one of claims 1 to 4, characterized in that the granulation involves melting the waste plastic, dechlorinating it, and semi-carbonizing it using shear heat from the agitator blades, and then adding water to solidify and granulate the waste plastic. A method for producing solid fuel according to any one of claims 1 to 4, characterized in that an air or inert gas purging process is performed when heating to above 180°C by shear heat from the stirring blades of the high-speed rotary mixer. The method for producing solid fuel described in claim 5, characterized in that an air or inert gas purging process is performed when heating to above 180°C by shear heat from the stirring blades of the high-speed rotary mixer. The method for producing solid fuel described in claim 5, characterized in that the water used for the hydration contains a neutralizing agent that neutralizes chlorinated compounds. A method for producing solid fuel according to any one of claims 1 to 4, characterized in that the produced solid fuel has a chlorine content of 1.0% by mass or less, a higher heating value of 25 MJ/kg or more, a moisture content of 5% by mass or less, and an ash content of 10% by mass or less, in accordance with RPF quality standards. 5. The method for producing a solid fuel according to claim 1, wherein the produced solid fuel has a chlorine content of 1.0% by mass ^{or less} , a bulk density of 0.4 t/m3 or more, an average particle diameter _D50 of 10.0 mm or less, 90% or more of all particles having a particle size of 0.01 mm or more, and an angle of repose of 50° or less. A method for producing solid fuel according to any one of claims 1 to 4, characterized in that the produced solid fuel has a sulfur content of 1% by mass or less.