Method for producing chlorine reduced solid fuel

Abstract

To provide a method for producing a chlorine-reduced solid fuel capable of reducing chlorine by a simple operation without requiring washing with water.SOLUTION: The method for producing the chlorine-reduced solid fuel comprises: a first sorting step of separating an earth and sand glass reduced raw material obtained by reducing earth and sand glass from a plastic-containing waste; a heating step of heating the earth and sand glass reduced raw material and embrittling it; and a second sorting step of separating a solid fuel from the embrittled earth and sand glass reduced raw material. The first sorting step includes a step of crushing the plastic-containing waste, sieving the crushed matter, separating it into an upper sieve and a lower sieve, and recovering the upper sieve, sorting the lower sieve by wind, and separating it into a heavy weight portion and a light weight portion, and recovering the light weight portion. The second sorting step includes a step of crushing the embrittled earth and sand glass reduced raw material, sorting the crushed material by wind, separating it into a heavy product and a light product, and recovering the light product.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a chlorine-reduced solid fuel. [Background technology]

[0002] Some waste plastics discarded as industrial waste or general waste have been exported overseas for material recycling, but in recent years exports have become difficult. In addition, the amount of waste plastics that are simply incinerated or disposed of in landfills remains large, and there is a need to reconstruct the waste plastic recycling system in order to reduce CO2 emissions and make effective use of domestic resources. Plastic waste that is simply incinerated or disposed of in landfills often contains a wide variety of plastics as well as many other impurities, such as metals, glass, stone, and fibers. This makes material recycling and chemical recycling difficult in many cases. Instead, it is effectively utilized as a heat source for power generation and cement production. In order to utilize plastic waste containing many impurities as a heat source, various methods have been developed, including using it as is, as well as pre-processing such as crushing, molding, and carbonization to improve handling and homogenize quality during heat source utilization. One method for utilizing plastic waste as a heat source is to produce solid fuel by heating it in a heating furnace and recovering the organic components. However, some plastic waste contains chlorine-containing plastics such as polyvinyl chloride and polyvinylidene chloride, and solid fuels produced from such chlorine-containing plastic waste tend to contain high concentrations of residual chlorine. Solid fuels containing high concentrations of chlorine release harmful hydrogen chloride gas during use, which can cause environmental degradation and corrosion of heating furnaces, requiring treatment by water washing.

[0003] Conventionally, a method for producing a solid fuel with reduced chlorine content has been proposed, for example, by heating chlorine-containing plastics in a low-oxygen atmosphere to 250-300°C to evaporate water and release chlorine without pyrolysis, and then heating to 400-500°C for pyrolysis, thereby producing a pyrolysis residue that does not contain salt derived from the chlorine in the chlorine-containing plastic (Patent Document 1). It has also been reported that halogen-containing waste containing chlorine is fed into a sorting device to separate it into halogen-containing waste with a high chlorine content and low-chlorine-concentration waste with an even lower chlorine content, and then the halogen-containing waste with a high chlorine content is introduced into a halogen separation means together with ammonia-containing material such as sewage sludge, whereby the ammonia contained in the ammonia-containing material reacts with the chlorine contained in the halogen-containing waste during pyrolysis, thereby minimizing the amount of residual chlorine (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-67800 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-155779 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method described in Patent Document 1 has problems with stable operation because the thermoplastic resin softens or melts during the first heating stage, causing it to fuse with other resins, leading to agglomeration and coarsening. This can lead to insufficient thermal decomposition of the resin and increases the risk of clogging of the furnace due to the thermoplastic resin fusing to the furnace walls. Furthermore, the method described in Patent Document 2 requires large-scale heating equipment exceeding the capacity of the halogen-containing waste to be treated, which inevitably increases equipment costs. Furthermore, when high-moisture waste such as sewage sludge is used, the large amount of water vapor generated from the admixture significantly increases the heat capacity of the furnace atmosphere, posing a problem of increased thermal energy required for heating. An object of the present invention is to provide a method for producing a solid fuel that can reduce chlorine by a simple operation without requiring water washing. [Means for solving the problem]

[0006] The present inventors investigated the reasons why water washing is unavoidable when producing solid fuel from plastic-containing waste and found that the reason is the presence of sediment glass in the plastic-containing waste. Specifically, alkali metal elements such as Na and K or alkaline earth metal elements such as Ca and Mg in the sediment glass react with some of the chlorine released during the treatment of the plastic-containing waste to form alkali metal salts or alkaline earth metal salts, making it necessary to remove these salts. The present inventors then discovered that by removing the sediment glass from the plastic-containing waste in advance and treating the sediment glass-removed raw material, reduced-chlorine solid fuel can be produced with a simple procedure without the need for water washing.

[0007] That is, the present invention provides the following [1] and [2]. [1] A first sorting step of sorting a sediment-glass-reduced raw material from plastic waste; a heating step of heating and embrittling the sediment glass reduction raw material; The second sorting process separates solid fuel from embrittled sediment and glass-reduced raw materials. Equipped with The first sorting step includes a step of crushing the plastic-containing waste, sieving the crushed material, separating it into oversized and undersized pieces, and recovering the oversized pieces, and also wind-separating the undersized pieces to separate them into heavy pieces and light pieces, and recovering the light pieces, The second sorting step includes crushing the embrittled sediment and glass reduced raw material, air-separating the crushed material, separating it into heavy products and light products, and recovering the light products; Method for producing reduced chlorine solid fuel. [2] The method for producing a reduced-chlorine solid fuel according to [1] above, wherein the temperature in the heating step is 300 to 650°C. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for producing a solid fuel that can reduce chlorine by a simple operation without requiring washing with water. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a flowchart illustrating an embodiment of a manufacturing method of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an example of a heating device applicable to the heating step according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the method for producing a chlorine-reduced solid fuel of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a flow chart showing an embodiment of the method for producing a chlorine-reduced solid fuel of the present invention.

[0011] The method for producing reduced-chlorine solid fuel of the present invention comprises a first sorting step, a heating step, and a second sorting step, as shown in Figure 1. Each step will be described below.

[0012] <First sorting process> The first sorting step is intended to remove sediment and glass from plastic-containing waste and produce a sediment and glass-reduced raw material. Chlorine-containing plastics such as polyvinyl chloride contained in plastic waste produce hydrogen chloride gas when heated, and the hydrogen chloride gas reacts with alkali metal oxides and alkaline earth metal oxides to produce soluble chloride salts according to the following reaction:

[0013] (Reaction of alkali metal oxides with hydrogen chloride) R2O + 2HCl → 2RCl + H2O (R represents an alkali metal) (Reaction of alkaline earth metal oxides with hydrogen chloride) MO + 2HCl → MCl2 + H2O (M represents an alkaline earth metal)

[0014] The above oxides, which are a source of hydrogen chloride, are primarily present as sedimentary glass in glass, ceramic waste, and other materials. Glass and ceramic waste are relatively hard materials, but they are easily broken down and pulverized by impact or compression. Therefore, by crushing plastic-containing waste before heating, the glass and ceramic waste can be pulverized. Then, by sieving the crushed material, the pulverized glass and ceramic waste can be separated from the resins and metals that are difficult to crush and pulverize. Furthermore, while the specific gravity of resins and fibers is 0.9 to 1.5, the specific gravity of glass and ceramic waste is 2.5. Therefore, the resins and fibers that fall through the sieve can be separated by air sorting. Therefore, this process includes the steps of crushing plastic-containing waste, sieving the crushed material, separating it into oversized and undersized pieces, and recovering the oversized pieces, and also separating the undersized pieces by air separation into heavy and light pieces, and recovering the light pieces. This removes the sediment glass component that contains a large amount of alkali metal oxides and alkaline earth metal oxides, thereby reducing elements that capture hydrogen chloride when heated and suppressing chlorine from remaining in the sediment glass reduction raw material.

[0015] (including plastic waste) Plastic-containing waste is not particularly limited as long as it contains plastic, but examples include shredder dust, automobile shredder dust, construction waste plastic, agricultural waste plastic, fishing waste plastic, and marine waste plastic. These wastes typically contain chlorine-containing plastics such as polyvinyl chloride and polyvinylidene chloride. Here, "shredder dust" as used herein refers to the mixture of debris discarded after industrial or municipal waste is shredded in an industrial shredder and metals are recovered. Examples of waste include discarded automobiles, discarded home appliances, vending machines, and office equipment. Plastic-containing waste may be a mixture of two or more types of waste, and may contain foreign matter other than plastic, such as soil, metal, glass, paper, and wood chips.

[0016] The size of the plastic-containing waste is not particularly limited, but from the viewpoint of preventing clogging during transportation and heat transfer during heating, it is preferable that the major axis is 50 mm or less. Here, in this specification, the "major axis of the waste plastic" refers to the value obtained by collecting the largest waste plastic from among the waste plastics and measuring the point where the diameter of the waste plastic is largest.

[0017] (Crushing) Crushing is carried out with the aim of breaking down the glass sediment contained in plastic-containing waste into fine particles, but if the plastic-containing waste contains urethane foam, fiber, etc., the glass sediment may become entangled in these materials, which may reduce the efficiency of removal. Therefore, in addition to breaking down the glass sediment into fine particles, crushing treatment of plastic-containing waste is carried out with the aim of separating the urethane foam, fiber, etc. from the glass sediment that has become entangled in them.

[0018] A crusher can be used for the crushing treatment. The crusher is preferably a shear type or an impact type. Examples include a hammer crusher, an impact mill, and a cutting mill. Crushing may be performed two or more times, and when performed two or more times, the same crusher or crushers of different types may be used. In addition, a crusher that can adjust the crushed particle size by providing a screen at the discharge outlet of the crushed material is preferred. The opening diameter of the screen provided in the crusher can be appropriately set within a range of 10 to 50 mm depending on the particle size of the raw material.

[0019] (Sieving) This is done to separate the finely ground soil and glass from the resin and metals produced by the crushing process. A sieve separator can be used for sieving. The type of sieve separator is not particularly limited, and for example, a vibrating sieve separator, a rotary sieve separator, a wave sieve separator, etc. can be appropriately selected. The mesh size of the sieve separator can be appropriately set to 10 mm or less, but from the viewpoint of suppressing metal dissipation into fine particles, it is preferably 6 mm or less, more preferably 4 mm or less. Note that, from the viewpoint of sorting efficiency, the lower limit of the mesh size is preferably 0.5 mm or more, more preferably 1 mm or more.

[0020] (Wind sorting) The fine particles recovered by sieving contain a fair amount of crushed fibers and resins, so the soil and glass are separated from the resin and fibers by wind sorting. For the air sorting, an air sorter can be used. The type of the air sorter is not particularly limited, and for example, a circulation type, a suction type, a zigzag type, or the like can be appropriately selected. For example, when using a circulation system, a fan creates an air flow from bottom to top, causing heavy objects to move downward against the air flow, while light objects move upward with the air flow, separating them into heavy and light objects. In this case, it is preferable to set the wind speed for wind sorting so that the heavy products are mainly composed of soil, sand, and glass. For example, the wind speed is preferably 3 m / s or more, more preferably 8 m / s or more, and preferably 25 m / s or less, and even more preferably 15 m / s or less.

[0021] <Heating process> The heating step is carried out for the purpose of heating the sediment-glass reduced raw material, which is made by reducing sediment-glass from plastic-containing waste, to embrittle it and also to dechlorinate it. A heating furnace can be used to heat the soil and glass reduction raw material. The type of heating furnace is not particularly limited, and examples that can be used include a fixed furnace, a stoker furnace, a rotary kiln furnace, a fluidized bed furnace, a vertical furnace, and a multi-tier furnace. A conveyor for transporting waste plastic from the waste plastic supply port to the discharge port may be installed inside the heating furnace.

[0022] A low-oxygen atmosphere is preferred for heating, as it allows the heat content of plant- and animal-derived fibers, such as resin materials and cellulose, contained in waste plastics to be fixed in the solid fuel after heating, facilitating crushing, pulverization, and physical separation in post-processing. Furthermore, considering the perspectives of continuous heating in a low-oxygen atmosphere, retaining a large amount of heat content in the solid fuel obtained after heating, and maximizing the value of plastic-containing waste as a fuel, processing under low oxygen conditions using an externally heated rotary kiln is most preferred. The low-oxygen heating atmosphere can be achieved by filling the furnace with nitrogen or water vapor. Alternatively, the low-oxygen atmosphere can be achieved by filling the furnace with gas components (e.g., HO, CO, flammable gases such as lower hydrocarbons) generated by the thermal decomposition of the raw materials themselves.

[0023] Alternatively, a double-walled heating device, as shown in Figure 2, may be used, in which a container equipped with a gas diffusion port is housed within a heating furnace. The heating device shown in Figure 2 has a first zone in which an inert gas or superheated steam is circulated within a container containing plastic waste, promoting gas volatilization and plastic embrittlement in a low-oxygen atmosphere, and a second zone in which oxidation of the gas generated in the first zone is promoted. Examples of inert gases include nitrogen, helium, and argon. Furthermore, superheated steam can be produced by superheating saturated steam generated by a boiler or the like using a superheating means such as a superheated steam generator.

[0024] The heating temperature is preferably 300°C or higher, more preferably 330°C or higher, even more preferably 380°C or higher, and even more preferably 430°C or higher in order to promote the thermal decomposition of polyvinyl chloride, chloroprene rubber, etc., and is preferably 650°C or lower, more preferably 600°C or lower, even more preferably 570°C or lower, and even more preferably 530°C or lower in order to prevent the metallic aluminum in the raw material from melting. The heating time is preferably 30 minutes or more, more preferably 40 minutes or more, even more preferably 50 minutes or more, and is preferably 180 minutes or less, more preferably 150 minutes or less, even more preferably 120 minutes or less.

[0025] <Second sorting process> The second sorting process aims to separate solid fuel from the embrittled sediment and glass reduced raw material, and includes a process of crushing the embrittled sediment and glass reduced raw material, wind-separating the crushed material, separating it into heavy products and light products, and recovering the light products.

[0026] (Crushing) The embrittlement obtained by heating the soil and glass reduction raw material contains a mixture of combustibles suitable for fuel and useful metals. Furthermore, the polymer compounds in the waste are decomposed into smaller molecules through thermal decomposition during the heating process, significantly reducing their mechanical strength, making them easily pulverizable by impact or compression.

[0027] A crusher can be used for the crushing treatment. The type of crusher is preferably one that crushes by collision stress or compression force. Specific examples include a hammer crusher, impact mill, ball mill, rod mill, roller mill, and jaw crusher. Crushing may be carried out two or more times, and when carried out two or more times, the same crusher or crushers of different types may be used. The crusher does not need to be equipped with a screen for adjusting particle size, but crushing is carried out so that the maximum particle size obtained after crushing is 30 mm or less, preferably 20 mm or less.

[0028] (Wind sorting) Wind separation is carried out for the purpose of separately recovering combustible materials that have been finely divided by the crushing process and valuable metals. For the air sorting, an air sorter can be used. The type of the air sorter is not particularly limited, but examples include a circulation type, a suction type, and a zigzag type. The wind speed for wind sorting is preferably set so that the light materials are mainly composed of solid fuels. For example, the wind speed is preferably 3 m / s or more, more preferably 5 m / s or more, and is preferably 20 m / s or less, more preferably 15 m / s or less. If the type of crusher in the preceding process is a type that recovers fine particles using airflow, such as a roller mill, there is no need to provide a separate air sorter.

[0029] Although the present invention has been described in detail above based on the embodiments thereof, the present invention is not limited to the above embodiments. Various modifications of the present invention are possible without departing from the spirit and scope of the present invention. For example, in the manufacturing method shown in FIG. 1, the light materials separated by air sorting in the second sorting step are recovered as solid fuel, but the heavy materials separated by air sorting contain valuable metals. Therefore, the heavy materials separated by air sorting may be gravity-separated to separately recover light metals such as aluminum and heavy metals such as copper, iron, and stainless steel. A gravity separator can be used for gravity separation. The gravity separator may be either a dry or wet type, but a dry table-type gravity separator is preferred, and an air table separator is more preferred. [Example]

[0030] The following examples will explain the present invention in more detail, but the present invention is not limited to the examples below.

[0031] Example 1 <First sorting process> (Crushing) Shredder dust collected from dismantled and crushed electrical appliances, furniture, etc. was crushed in a small crusher to particles of 15 mm or less. The shredder dust was crushed using a swing hammer crusher equipped with a φ20 mm granulating screen. (Sieving) The crushed material was sieved using a JIS sieve with an opening diameter of 2 mm. (Wind sorting) The undersieve (2mm pass-through material) was used to remove heavy materials containing a large amount of sediment and glass using a zigzag wind sorter, and the sediment and glass-reduced raw material was collected as light material. The wind speed for wind sorting was set at 12 m / s.

[0032] <Heating process> For heating, a heating device was used, which was a box-type electric furnace (internal volume 9 L) shown in FIG. 2, in which a cylindrical stainless steel container (internal volume 0.6 L) equipped with a gas diffusion port was placed. The sediment glass reduction raw material was placed in a SUS container, and the furnace temperature was raised to a range of 300 to 550°C while nitrogen gas (N2) was flowed into the SUS container, and the heat treatment was carried out by holding the temperature for 60 minutes. After the heat treatment, nitrogen gas was passed through the furnace to cool it down, and then an embrittlement of the sand and glass reduced raw material was obtained.

[0033] <Second sorting process> (Crushing) A small crusher was used to crush the embrittled material used as the raw material for reducing soil and glass. (Wind sorting) The combustibles that had been crushed into fine particles were separated from the metals that had not been crushed into fine particles by an air separator, and the solid fuel was recovered as a lightweight material. The wind speed for air separator was set at 8 m / s. The heavy products separated by the air sorter were then gravity sorted, with iron and copper being recovered as heavy products and aluminum being recovered as light products. An air table was used as the gravity sorter.

[0034] Example 2 In the heating process, the same operations as in Example 1 were performed except that the sediment-glass reducing raw material was placed in a SUS container, and the furnace temperature was raised to within the range of 300 to 550°C while superheated steam (SHS) was flowed into the SUS container, and the heating treatment was carried out by holding the temperature for 60 minutes.

[0035] Comparative Example 1 The same procedures as in Example 1 were carried out, except that the first selection step was not carried out.

[0036] Comparative Example 2 The same procedure as in Example 2 was carried out, except that the first selection step was not carried out.

[0037] The shredder dust and the soil and glass reduction raw material used in the first sorting process were each incinerated at 550°C until they reached a constant weight, after which semi-quantitative analysis was performed using XRF (FP method), and the total alkali content was calculated using the following formula.

[0038] Total alkalinity (Na2O equivalent) Na2Oeq(%) = Na2O(%) + 0.658K2O(%)

[0039] In addition, to evaluate the desalination rate during the heating process, the sample before heating and the heat-treated product after cooling were each pulverized, and chlorine was extracted by the Eschka method and quantified by ion chromatography.

[0040] The desalination rate by heating was calculated using the following formula.

[0041] Desalination rate (%) = [1-(amount of chlorine in the heat-treated material (g) ÷ amount of chlorine in the sample before heating (g))] x 100

[0042] Table 1 shows the production conditions and analysis results for each of the examples and comparative examples.

[0043] [Table 1]

[0044] Table 1 shows that by first removing soil and glass from plastic-containing waste, then heating the soil and glass-removed raw material to embrittle it, crushing the embrittled material, and then wind-separating the crushed material to recover the lighter material, solid fuel with reduced chlorine can be produced with simple operations, without the need for water washing.

Claims

1. A first sorting step of sorting a sediment-glass-reduced raw material from plastic-containing waste; a heating step of heating and embrittling the sediment glass reduction raw material; A second sorting step for sorting solid fuel from embrittled sediment and glass reduced raw material. Equipped with The first sorting step includes a step of crushing the plastic-containing waste, sieving the crushed material, separating it into oversized and undersized materials, and recovering the oversized materials, and also separating the undersized materials by air force to separate them into heavy materials and light materials, and recovering the light materials, The second sorting step includes crushing the embrittled sediment and glass reduced raw material, air-separating the crushed material, separating it into heavy products and light products, and recovering the light products. Method for producing reduced chlorine solid fuel.

2. 2. The method for producing a reduced-chlorine solid fuel according to claim 1, wherein the temperature in the heating step is 300 to 650°C.

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