Method for producing composite granules containing waste plastics and method for treating waste plastics

Abstract

Provided are a method for producing composite granules and a method for treating waste plastics, the methods making it possible to reduce the organic-chlorine concentration in light oil and / or refined gas when chlorine-containing waste plastics are treated in a coke oven. Provided is a method for producing composite granules containing chlorine-containing waste plastics and a Ca-containing substance for dry distillation in the carbonization chamber of a coke oven, the method for producing composite granules comprising granulating materials comprising the chlorine-containing waste plastics and the Ca-containing substance at a temperature lower than the dechlorination temperature of the waste plastics.

Description

Method for producing composite granules containing waste plastic, and method for treating waste plastic

[0001] The present invention relates to a method for producing composite granules containing waste plastic, and a method for treating waste plastic.

[0002] In recent years, from the perspectives of effective utilization of resources and contribution to the realization of carbon neutrality, methods have been proposed for carbonizing waste plastic in coke ovens to obtain recycled resources such as carbonized products, tar, light oil, and refined gas. This method has advantages such as being capable of treating a large amount of waste plastic and effectively utilizing existing coke ovens. However, knowledge on carbonization conditions suitable for treating waste plastic is still insufficient. For example, when obtaining products such as tar, light oil, and refined gas from the gas generated during carbonization, an allowable upper limit may be set for the chlorine concentration in the product. Chlorine can exist as inorganic chlorine (that is, the chlorine (Cl) element constituting chlorine-containing inorganic substances) or organic chlorine (that is, the chlorine (Cl) element constituting chlorine-containing organic substances). In the present disclosure, when simply referring to "chlorine", the "chlorine" includes the above-mentioned inorganic chlorine and organic chlorine. If the waste plastic contains chlorine, chlorine may also remain in the recycled resource. Therefore, when treating chlorine-containing waste plastic, it is desired to establish treatment conditions that can control the chlorine concentration of the product within a desired range. When waste plastic is charged into a coke oven, reduction of the organic chlorine concentration in the product is particularly desired from the perspective of reducing the load on the environment and facilities.

[0003] As a method for controlling the quality of products obtained by carbonization using a coke oven, carbonization using coal blended with additives has been proposed. For example, Patent Document 1 describes a method for producing highly reactive coke for blast furnaces, which is characterized in that an alkaline earth metal compound or a mixture of alkaline earth metal compounds, which is a catalyst that activates the reaction of producing carbon monoxide from carbon and carbon dioxide, is added to coal, followed by carbonization in a coke oven.

[0004] On the other hand, regarding used plastics as a coke substitute, Patent Document 2 describes a method for blowing used plastics into a furnace, characterized in that, in the operation of a vertical furnace using used plastics as a furnace blowing material, a granular material is blown into the furnace, which is made by mixing used plastics with a substance that lowers the melting point of the ash produced by the combustion of used plastics, and at least a part of the substance that lowers the melting point of the ash may be a CaO source and / or an MgO source.

[0005] Japanese Patent Publication No. 2001-348576 Japanese Patent Publication No. 2006-152331

[0006] The alkaline earth metal compounds or mixtures thereof described in Patent Document 1 are used to improve the reactivity of coke, and the CaO and MgO sources described in Patent Document 2 are used to lower the melting point of the ash produced by combustion. However, these technologies have not contributed to reducing the chlorine concentration of products such as diesel fuel and purified gas obtained by carbonization using a coke oven. In particular, no conventional carbonization method has yet been proposed that uses chlorine-containing waste plastics and can achieve a reduction in the organochlorine concentration of diesel fuel and / or purified gas.

[0007] The present invention aims to solve the above problems and provide a method for producing composite granules and a method for processing waste plastics that can reduce the concentration of organic chlorine in light oil and / or purified gas when processing chlorine-containing waste plastics in a coke oven.

[0008] The gist of the present invention is as follows: [1] A method for producing a composite granule containing chlorine-containing waste plastic and a Ca-containing substance for carbonization in the carbonization chamber of a coke oven, comprising granulating a material containing chlorine-containing waste plastic and a Ca-containing substance at a temperature below the dechlorination temperature of the waste plastic. [2] The method for producing a composite granule according to item 1, wherein the granulation is carried out at a temperature of less than 250°C. [3] The method for producing a composite granule according to item 1 or 2, wherein the granulation is carried out at a temperature of 100°C or higher. [4] The method for producing a composite granule according to any one of items 1 to 3, wherein the Ca-containing substance is kept isolated from the outside air from the time it is combined with the chlorine-containing waste plastic until it is subjected to granulation. [5] A method for treating waste plastics by carbonizing a composite granule containing chlorine-containing waste plastic and a Ca-containing substance in the carbonization chamber of a coke oven, wherein the composite granule is produced by a method for producing composite granules that includes granulating a material containing chlorine-containing waste plastic and a Ca-containing substance at a temperature below the dechlorination temperature of the waste plastic, and the composite granule is charged into the carbonization chamber. [6] The method for treating waste plastics according to item 5, wherein the granulation is carried out at a temperature below 250°C. [7] The method for treating waste plastics according to item 5 or 6, wherein the granulation is carried out at a temperature of 100°C or higher. [8] The method for treating waste plastics according to any one of items 5 to 7, wherein coal is further charged into the carbonization chamber, and the amount of waste plastic charged as the composite granule is 0.5% to 5% by mass relative to 100% by mass of the amount of coal charged. [9] A method for treating waste plastics according to any one of items 5 to 8, wherein the Ca-containing substance is kept isolated from the outside air from the time it is combined with the chlorine-containing waste plastic until it is subjected to granulation.

[0009] According to the present invention, a method for producing composite granules and a method for processing waste plastics can be provided that can reduce the organochlorine concentration of light oil and / or purified gas when processing chlorine-containing waste plastics in a coke oven.

[0010] Figure 1 shows an example of the granulation procedure in this embodiment. Figure 2 shows the relationship between the organic chlorine concentration of the generated gas and the organic chlorine concentration of the diesel fuel. Figure 3 is a diagram illustrating the dechlorination of waste plastics. Figure 4 shows the effect of adding a Ca-containing substance on the chlorine concentration of waste plastics. Figure 5 shows the effect of adding a Ca-containing substance on the organic chlorine concentration of the generated gas.

[0011] The following describes exemplary embodiments of the present invention (which may also be referred to as "embodiments" in this disclosure), but the present invention is not limited to these embodiments.

[0012] One aspect of the present invention provides a method for producing composite granules containing chlorine-containing waste plastic and a Ca-containing substance for carbonization in the carbonization chamber of a coke oven. In one aspect, the method includes granulating a material containing chlorine-containing waste plastic and a Ca-containing substance at a temperature below the dechlorination temperature of the waste plastic. Another aspect of the present invention provides a method for processing waste plastic by carbonizing composite granules containing chlorine-containing waste plastic and a Ca-containing substance in the carbonization chamber of a coke oven. In one aspect of the method, composite granules are produced by a method for producing composite granules that includes granulating a material containing chlorine-containing waste plastic and a Ca-containing substance at a temperature below the dechlorination temperature of the waste plastic, and the composite granules are charged into the carbonization chamber.

[0013] In this disclosure, the dechlorination temperature of chlorine-containing waste plastics means the temperature at which, in mass spectrometry of chlorine-containing waste plastics, the count of the signal originating from hydrogen chloride (HCl) begins to increase with increasing temperature.

[0014] In addition to the composite granules, coal may or may not be charged into the carbonization chamber, but typically, coal is also charged. While the charging of components other than coal, waste plastics, and Ca-containing substances into the carbonization chamber is not excluded as long as it does not impair the effects of the present invention, in a typical embodiment, the only components charged into the carbonization chamber (i.e., intentionally introduced into the carbonization chamber) are coal, waste plastics, and Ca-containing substances. Therefore, in a typical embodiment, the only components intentionally included in the composite granules are waste plastics and Ca-containing substances.

[0015] When waste plastics are pyrolyzed in the carbonization chamber of a coke oven, they can produce carbonized products (carbon residue), hydrocarbon oil (tar or diesel fuel), refined gas (hydrocarbon gas, hydrogen gas, etc.), and by-products. In this embodiment, both waste plastics and coal may be carbonized, or waste plastics may be carbonized alone (i.e., without coal). Carbonization can produce carbonized products (coke), tar, diesel fuel, and refined gas as useful materials. The carbonized product (coke) can be used for blast furnaces and various other applications depending on its quality. The hydrocarbon oil can be used, for example, as a raw material for various chemical products. The refined gas can be used, for example, as fuel for power generation. In a typical embodiment, the product extracted from the coke oven may have a component composition of approximately 20% by mass of coke, approximately 40% by mass of oil, and approximately 40% by mass of refined gas.

[0016] A coke oven generally has a configuration in which carbonization chambers and combustion chambers are alternately arranged in the direction of the furnace width above a heat storage chamber. Waste plastics (and optionally further coal) charged into the carbonization chamber are carbonized by heat transfer from the combustion chamber, producing useful products such as carbonized material, tar, diesel fuel, and refined gas. The carbonized material is extruded in the direction of the furnace length by an extruder. The gases generated from the coke oven flow out of the furnace from the carbonization chamber via a riser pipe, where they are separated to produce tar, diesel fuel, and refined gas. In this disclosure, generated gases include all gases that flow out of the furnace from the carbonization chamber via a riser pipe during carbonization in the carbonization chamber of the coke oven. Each carbonization chamber usually has multiple charging holes. Waste plastics (and optionally further coal) may each be charged into the carbonization chamber from one or more charging holes, for example, two, three, four, or five charging holes.

[0017] If additional coal is charged, the timing of charging of coal and waste plastics is not limited. The order in which the carbonization of coal progresses and the carbonization of waste plastics progresses is not considered.

[0018] When chlorine-containing waste plastics are subjected to dry distillation, chlorine may remain in both the dry product and the generated gas. The majority of the chlorine in the generated gas (usually 99% or more, based on the number of chlorine atoms) is inorganic chlorine, existing as hydrogen chloride, etc. Inorganic chlorine can be neutralized by relatively easy methods, such as flushing with ammonia to convert it to ammonium chloride. On the other hand, some of the chlorine in the generated gas (usually less than 1%, based on the number of chlorine atoms) is organic chlorine, existing as chloromethane, chlorobenzene, etc., and is difficult to remove. Residual organic chlorine in the generated gas or the products obtained from it can cause environmental burdens and equipment malfunctions (corrosion, etc.).

[0019] In this embodiment, a composite granule containing chlorine-containing waste plastic and a Ca-containing substance is charged into the carbonization chamber. Therefore, in the carbonization chamber, the chlorine-containing waste plastic is carbonized in the presence of the Ca-containing substance. The chlorine contained in the chlorine-containing waste plastic is dechlorinated at a temperature above the dechlorination temperature of the waste plastic. Since the temperature inside the carbonization chamber during carbonization is significantly higher than this dechlorination temperature, dechlorination inevitably occurs during carbonization. In this case, if the Ca-containing substance is present, the chlorine released from the surface of the waste plastic can be captured by the Ca-containing substance, converted to CaCl2, and retained (i.e., trapped) in the coke. The released chlorine is mostly hydrogen chloride (HCl), with a small amount of chlorine (Cl2) also present. If the proportion of chlorine distributed into the coke from the chlorine brought into the carbonization chamber increases, the proportion of chlorine distributed into the generated gas from the chlorine brought into the carbonization chamber will decrease. Furthermore, in the generated gas, chlorine atoms introduced in the form of inorganic chlorine may constitute organic matter (i.e., inorganic chlorine may be converted to organic chlorine). If the chlorine concentration in the generated gas is reduced, the generation of organic chlorine in the generated gas will also be reduced, thus reducing the organic chlorine concentration in the generated gas. As a result, the organic chlorine concentration in the diesel fuel and purified gas obtained from the generated gas may be reduced. Thus, according to the method of this embodiment, the organic chlorine concentration in the generated gas can be reduced by the simple operation of adding a Ca-containing substance, and as a result, the organic chlorine concentration in the diesel fuel and purified gas obtained from the generated gas can be reduced. The organic chlorine concentration in the generated gas is determined by combustion ion chromatography. The generated gas sample to be used for measurement may be either before or after ammonia water flushing. If the sample is generated gas before ammonia water flushing, the sample is subjected to bubbling in water to remove inorganic chlorine before being used for measurement. According to the inventors' studies, inorganic chlorine (especially HCl) is removed by bubbling the generated gas in water, and it has been separately confirmed that inorganic chlorine is not actually present in the gas obtained by this treatment. Furthermore, if the sample is the gas generated after ammonia water flushing, the inorganic chlorine is removed by ammonia water flushing.Therefore, the chlorine concentration obtained by combustion ion chromatography of the generated gas can be considered as the organic chlorine concentration of the generated gas. Although the method of this embodiment focuses particularly on reducing the organic chlorine concentration of diesel fuel and refined gas, the same reduction in organic chlorine concentration can be achieved in tar obtained from the generated gas.

[0020] When collected waste plastics are granulated and charged into a carbonization chamber, if the granulation temperature is above the dechlorination temperature of the waste plastics, dechlorination will occur during granulation. If granulation is performed at a temperature above the dechlorination temperature using waste plastics alone, chlorine is released outside the waste plastics due to dechlorination, thus potentially reducing the chlorine concentration in the granules. However, if granulation is performed at a temperature above the dechlorination temperature in the presence of waste plastics and Ca-containing substances, the chlorine released by dechlorination is captured by the Ca-containing substances, converted to CaCl2, and remains in the granules. In other words, in the presence of waste plastics and Ca-containing substances, even if the granulation temperature is above the dechlorination temperature, it is difficult to obtain the benefits (i.e., reduction of chlorine concentration in the granules) that are obtained when the granulation temperature is above the dechlorination temperature in the absence of Ca-containing substances. From this perspective, in this embodiment, the temperature at which a material containing chlorine-containing waste plastics and Ca-containing substances is granulated is set below the dechlorination temperature of the waste plastics. According to this embodiment, the energy required for heating during granulation can be reduced while lowering the organochlorine concentration of the product obtained by carbonization to a desired level.

[0021] <Coal> The coal charged into the carbonization chamber may be one or more types of coal, and may be pulverized coal, molded coal, or a combination thereof. There are no particular restrictions on the type of coal. Pulverized coal refers to crushed coal, and includes coal that has been further size-adjusted after crushing, and agglomerated coal when agglomerated coal is mixed in. In this disclosure, agglomerated coal refers to coal with an equivalent spherical radius of less than 6 mm obtained by adding a binding agent to pulverized coal (in one embodiment, pulverized coal below a 0.3 mm sieve) and press-molding. In this disclosure, molded coal refers to coal with an equivalent spherical radius of 6 mm or more obtained by adding a binding agent to pulverized coal (in one embodiment, pulverized coal below a 0.3 mm sieve) and press-molding.

[0022] In one embodiment, the moisture content of the coal charged into the carbonization chamber may be 0% by mass to 10% by mass. The moisture content may be reduced, for example, by a conventionally known coal dryer.

[0023] <Waste Plastics> Waste plastics may be general waste or industrial waste, and there are no limitations on their origin. For example, waste plastics may originate from one or more sources selected from bottles (e.g., PET bottles and non-PET bottles), bottle caps, packaging films, packaging materials (e.g., expanded polystyrene packaging materials), home appliances (e.g., home appliance casings), logistics materials (e.g., pallets and containers), agricultural plastics, automobile parts, pipes, wire insulation materials, etc. In one embodiment, waste plastics may originate from one or more sources. Waste plastics may consist of one or more polymers.

[0024] Waste plastics are plastics collected as various types of waste, which may be general waste or industrial waste. In one aspect, they are plastics that meet the sorting standards of the revised Container and Packaging Recycling Law (Law Amending Part of the Law Concerning the Promotion of Separate Collection and Recycling of Containers and Packaging (Law No. 76 of June 15, 2006)), which came into effect in April 2007 (for example, PET bottles and plastic containers and packaging). Such sorting standards-compliant materials have a relatively uniform material composition, which may be advantageous for producing high-quality recycled materials.

[0025] Waste plastics may contain thermoplastic polymers and / or thermosetting polymers. Examples of thermoplastic polymers include polyolefins (e.g., polyethylene and polypropylene), polyesters (e.g., polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate), acrylic resins, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polystyrene, polycarbonate, polyamide, polyacetal, and fluororesins. Examples of thermosetting polymers include phenolic resins, melamine resins, urea resins, polyurethanes, epoxy resins, and unsaturated polyester resins.

[0026] The waste plastic charged into the carbonization chamber in this embodiment contains chlorine. Such waste plastic may consist solely of chlorine-containing polymers, or it may be a combination of chlorine-containing polymers and chlorine-free polymers. Examples of chlorine-containing polymers include polymers having at least chlorine-containing repeating units (e.g., polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer), and chlorinated products of the thermoplastic polymers or thermosetting polymers exemplified above (e.g., chlorinated polyolefins).

[0027] In one embodiment, the chlorine (Cl) element concentration in 100% by mass of the total amount of waste plastic charged into the carbonization chamber may be between 1% by mass and 70% by mass. In one embodiment, the Cl element concentration may be 1% by mass or more, or 5% by mass or more, or 10% by mass or more, or 20% by mass or more, or 30% by mass or more, or 40% by mass or more, or 50% by mass or more, or 55% by mass or more, and in one embodiment, it may be 70% by mass or less, or 65% by mass or less. The above Cl element concentration is the arithmetic mean of the polymers if the waste plastic is a combination of two or more polymers. For example, if the waste plastic is a 1:1 (mass ratio) combination of a chlorine-containing polymer with a Cl element concentration of 50% by mass and a chlorine-free polymer, the Cl element concentration in 100% by mass of the waste plastic is 25% by mass. The Cl element concentration of the waste plastic is a value obtained using combustion ion chromatography.

[0028] From the viewpoint of carbonization efficiency, the moisture content of the waste plastic may be 30% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less in one embodiment.

[0029] <Ca-containing substances> Useful Ca-containing substances are those that can react with chlorine-containing substances (mainly HCl) generated from waste plastics to form calcium chloride (CaCl2). Examples of Ca-containing substances include calcium hydroxide, calcium carbonate, and calcium oxide, but calcium hydroxide is preferred from the viewpoint of availability and ease of handling. Ca-containing substances may be used in any form, such as powder or dispersion in a medium (e.g., water).

[0030] The amount of Ca-containing substance added may be an extranumerator per 100% by mass of waste plastic, and may be 0.5% to 10% by mass in one embodiment, based on the element Ca. From the viewpoint of reducing the organochlorine concentration, the amount added may be 0.5% or more by mass, or 1% or more by mass, or 1.5% or more by mass in one embodiment. There is no particular upper limit on the amount of Ca-containing substance, but may be 10% or less by mass, or 8% or less by mass, or 6% or less by mass in one embodiment, based on the element Ca.

[0031] In one embodiment, after collection, waste plastic is crushed and / or melted, granulated, and then charged into a carbonization chamber. The Ca-containing substance only needs to be present with the waste plastic during granulation. That is, the timing of adding the Ca-containing substance can be before granulation of the waste plastic, during granulation, or both. The Ca-containing substance only needs to adhere to the waste plastic, and there are no restrictions on its form, but as an example, it may be added as a powder. An example of an addition method is the addition of Ca-containing substance powder to waste plastic with a particle size of 20 mm or less. Such a method is preferable from the viewpoint of distributing the Ca-containing substance on the waste plastic. It should be noted that the method of adding the Ca-containing substance after granulation of the waste plastic may be advantageous in that it offers a high degree of freedom in the method of adding the Ca-containing substance, and the Ca-containing substance is less affected by the granulation temperature. On the other hand, the method of adding a Ca-containing substance before and / or during the granulation of waste plastics may be advantageous in that the Ca-containing substance can be present not only on the surface of the composite granules but also inside them, thereby reducing the amount of Ca-containing substance lost during the transport of the composite granules, that is, in that the amount of Ca-containing substance added to the waste plastics can be controlled with greater precision.

[0032] <Granulation> The composite granules containing chlorine-containing waste plastic and Ca-containing material only need to have a granular form, and the granulation method is not limited. For example, the collected waste plastic may be crushed and / or melted, and then molded to a desired particle size (e.g., by extrusion molding). After collection, the waste plastic may undergo pretreatment other than granulation before being charged into the carbonization chamber. Examples of pretreatment include the above-mentioned crushing and / or melting, removal of foreign matter, and adjustment of moisture content by drying. Removal of foreign matter may include removal of metals using a magnetic separator, removal of heavy objects using an air separator, etc.

[0033] When crushing waste plastic, the crushing may be carried out using, for example, a compression type, shear type, cutting type, impact type, or friction type crusher. Figure 1 is a diagram showing an example of the granulation procedure in this embodiment. Referring to Figure 1, the waste plastic P may be crushed in the crusher 11 to obtain crushed material, and then the crushed material may be supplied to the granulator 12. Examples of granulators include twin-screw type compression molding machines. In one embodiment, the crusher 11 and the granulator 12 may be separate devices. In this case, one or more material supply mechanisms (not shown), such as a hopper or a conveying screw, may be present between the crusher and the granulator. In one embodiment, the material supply mechanism may be a quantitative supply mechanism. For example, the hopper may be a quantitative supply machine. The hopper may be equipped with an agitation mechanism inside. In another embodiment, the crusher 11 and the granulator 12 may be a crushing zone and a granulation zone in a single device (for example, a crushing and granulating machine).

[0034] If the waste plastic is not to be crushed, the waste plastic P may be supplied to the granulator 12 without passing through the crusher 11. In one embodiment of this case, the waste plastic P may be supplied to a material supply mechanism (not shown) located upstream of the granulator 12.

[0035] When melting waste plastic, the melting may be performed inside the granulator 12. The temperature of the molten material is not particularly limited as long as it is below the dechlorination temperature of the waste plastic.

[0036] Referring to Figure 1, waste plastic and Ca-containing substances may be combined in at least one of the following ways: • Add Ca-containing substance a to the waste plastic before it is supplied to the crusher 11. • Add Ca-containing substance b to the crusher 11. • Add Ca-containing substance c to the waste plastic after it leaves the crusher 11 and before it is supplied to the granulator 12. • Add Ca-containing substance d to the granulator 12.

[0037] When waste plastic is supplied to a granulator via a material supply mechanism such as a quantitative feeder, the Ca-containing substance c may be added to the material supply mechanism. If the material supply mechanism is equipped with a mixing mechanism such as a stirring mechanism, the waste plastic and the Ca-containing substance may be uniformly mixed in the mixing mechanism.

[0038] In one embodiment, the Ca-containing substance is kept isolated from the outside air from the time it is combined with chlorine-containing waste plastic until it is subjected to granulation. In this case, the Ca-containing substance can be subjected to granulation without any loss to the outside after being combined with the waste plastic. Therefore, the amount of Ca-containing substance added can be controlled with high precision. In one embodiment, the space through which the Ca-containing substance passes from the point of addition to the Ca-containing substance to the granulator may be a single closed space. Note that "isolated from the outside air" means a state in which the Ca-containing substance is not exposed to the outside air and does not scatter into the outside air. Therefore, in addition to a strictly airtight state, a state in which there is an inflow of outside air, etc., but the contact between the Ca-containing substance and the outside air is minimal may also be included in the state isolated from the outside air.

[0039] The granulation temperature is set to a temperature lower than the dechlorination temperature of chlorine-containing waste plastics, from the viewpoint of preventing equipment corrosion due to the absence of hydrogen chloride (HCl) generation. The dechlorination temperature may vary depending on the type of waste plastic. Therefore, it is best to set the granulation temperature after knowing in advance the dechlorination temperature that the waste plastic to be granulated can actually reach. The granulation temperature should be lower than the dechlorination temperature of the waste plastic. If the dechlorination temperature of the waste plastic is 250°C or higher, the granulation temperature may, in one embodiment, be less than 250°C, or 180°C or lower, or 130°C or lower, from the viewpoint of reducing the energy required for heating during granulation. There is no particular limit to the lower limit of the granulation temperature, but in one embodiment, it may be 100°C or higher, considering the efficiency of removing organic matter and water. In one embodiment, the granulation temperature can be set as the temperature of the waste plastic mixing section in the granulator. The difference between the dechlorination temperature and the granulation temperature is preferably 3°C or higher, 5°C or higher, 10°C or higher, or 50°C or higher, from the viewpoint of suppressing dechlorination during granulation, and preferably 80°C or lower, or 50°C or lower, from the viewpoint of the efficiency of water removal.

[0040] There are no particular restrictions on granulation conditions other than the granulation temperature, and they may be set as appropriate to obtain composite granules of the desired particle size. For example, the granulation time may be set to 1 to 10 minutes.

[0041] The particle size of the composite granules may, in one embodiment, be 10 mm to 50 mm or 25 mm to 40 mm. In the case of a shape with a base (e.g., cylinder, elliptical cylinder, etc.), the particle size refers to the major axis of the base (the maximum value if the values ​​differ between bases), and in the case of a shape without a base (e.g., sphere, ellipsoid, irregularly shaped solid, etc.), it refers to the major axis of the shape.

[0042] When coal is further charged, the amount of waste plastic charged into the carbonization chamber as a composite granule may be within a desired range relative to 100% by mass of the amount of coal charged into the carbonization chamber. The amount of waste plastic charged into the carbonization chamber as a composite granule may be set appropriately according to the properties of the desired product. From the viewpoint of obtaining the advantage of processing a large amount of waste plastic, the amount of waste plastic charged into the carbonization chamber as a composite granule may, in one embodiment, be 0.5% by mass or more, or 1% by mass or more, or 5% by mass or more, or 10% by mass or more, relative to 100% by mass of coal charged into the carbonization chamber. From the viewpoint of keeping the organochlorine concentration of the product low and obtaining high coke strength, in one embodiment, it may be 5% by mass or less, 3% by mass or less, or 1% by mass or less. The amount may be, for example, 1% by mass to 5% by mass.

[0043] <Carbonization> In this embodiment, waste plastics can be processed using a carbonization chamber used for coal carbonization. This allows waste plastics to be processed without interrupting the process of producing coke from coal. Alternatively, in this embodiment, a carbonization chamber not used for coal carbonization may be used. The carbonization conditions (temperature, time, etc.) may be the same as when producing coke using only coal. In one embodiment, the carbonization temperature may be 700°C to 1400°C, for example, 900°C to 1200°C. For example, in polyvinyl chloride (PVC), a primary pyrolysis reaction occurs at about 250°C or higher, and a secondary pyrolysis reaction occurs at about 400°C due to main chain severance. High-temperature carbonization using a coke oven is excellent for the thermal decomposition of waste plastics. In addition, in the method of this embodiment, the concentration of organochlorines in the generated gas is reduced by using a Ca-containing substance.

[0044] <Organochlorine Concentration> The target organochlorine concentration of the generated gas may be determined based on a desired value for the organochlorine concentration of a product obtained from the generated gas. In one aspect, light oil and purified gas can be produced from the generated gas. In one aspect, the target organochlorine concentration of the light oil may be 50 mg / L or less, 25 mg / L or less, 13 mg / L or less, or 10 mg / L or less. In one aspect, the target organochlorine concentration of the purified gas may be 18 μg / L or less, 9 μg / L or less, 5 μg / L or less, or 4 μg / L or less. According to studies by the present inventors, it has been separately confirmed that if the organochlorine concentration of the generated gas is reduced, the organochlorine concentrations of the light oil and the purified gas are also reduced. In a preferred embodiment, the target organochlorine concentration of the generated gas is determined so as to be below one or two desired values among the target organochlorine concentration of light oil and the target organochlorine concentration of purified gas. From this viewpoint, in one aspect, the target organochlorine concentration of the generated gas may be 20 μg / L or less, 10 μg / L or less, 6 μg / L or less, or 5 μg / L or less. A lower target organochlorine concentration of the generated gas is ideal, but reducing the organochlorine concentration to a lower value requires a larger amount of Ca-containing substance. In consideration of process efficiency, the influence on coke strength when increasing the amount of the Ca-containing substance, and the like, in one aspect, the target organochlorine concentration of the generated gas may be 3 μg / L or more.

[0045] In one aspect, the organochlorine concentration of the generated gas is measured by sampling a portion of the generated gas during carbonization. The timing for collecting the generated gas may be 5 minutes or 20 minutes after the start of carbonization, and further every 20 minutes thereafter up to 420 minutes. In one aspect, the organochlorine concentration of each of the light oil and the purified gas is measured as the chlorine concentration obtained when the light oil and the purified gas are sampled and each subjected to combustion ion chromatography measurement.

[0046] Hereinafter, exemplary embodiments of the present invention will be further described with reference to working examples, but the present invention is not limited to these working examples.

[0047] <<Preliminary Study Example 1>> As a preliminary study, the relationship between the organochlorine concentration in the generated gas and the organochlorine concentration in light oil and the refined gas was investigated. In an operating coke oven, tests were conducted for several days each using two types of plastics having different chlorine contents in all oven groups, and the generated gas from the oven groups was sampled at a suction main to measure the chlorine concentration. Inorganic chlorine was removed from the sample used for measurement through ammonia liquor flushing. Therefore, the value measured as the chlorine concentration in the generated gas was regarded as the organochlorine concentration of the generated gas. Separately, the chlorine concentration of light oil obtained through a chemical product refining process from the generated gas (from which inorganic chlorine was removed through ammonia liquor flushing) from all oven groups was also measured. Therefore, the value measured as the chlorine concentration in the light oil was regarded as the organochlorine concentration of the light oil.

[0048] The operation condition was a method in which coal and plastic are mixed in advance and charged into the coke oven, and the operation was changed to the following two levels. [Level 1] Waste plastic with a chlorine concentration of 8300 ppm was added at an addition rate of 1% by mass (based on 100% by mass of coal, expressed as an external percentage). [Level 2] Waste plastic with a chlorine concentration of 1300 ppm was added at an addition rate of 1% by mass (based on 100% by mass of coal, expressed as an external percentage).

[0049] At each level, the generated gas was collected at an offtake main, and sampling was performed twice with an interval of 6 hours or more. Sampling was also performed twice at a rate of once per day for light oil. In consideration of storage in a relay tank, two light oil samples were collected once per day after 2 days or more had passed since switching the waste plastic to be added. Each value was averaged for handling. If values vary, sampling may be performed more times and the average value may be used.

[0050] The measurement of chlorine concentration was performed according to the procedure described in [Measurement Conditions for Combustion Ion Chromatography] below. The results are shown in Table 1. A plot of these results is shown in Figure 2.

[0051]

[0052] Figure 2 shows the relationship between the organic chlorine concentration of the generated gas and the organic chlorine concentration of the diesel fuel. As can be seen from Figure 2, a correlation was confirmed between the organic chlorine concentration of the generated gas and the organic chlorine concentration of the diesel fuel. Although not evaluated in this study, since the main chlorine-containing chemical products obtained by refining the generated gas are diesel fuel and refined gas, it is considered that the organic chlorine concentration of the refined gas is also correlated with the organic chlorine concentration of the generated gas. Therefore, from these results, it is considered that if the organic chlorine concentration of the generated gas is reduced, the organic chlorine concentrations of the diesel fuel and refined gas will also be reduced.

[0053] <<Example of preliminary study 2>> As a preliminary study, the dechlorination temperature of waste plastics was investigated. Waste plastics were carbonized in an electric tubular furnace. The waste plastics used and the carbonization conditions are as follows.

[0054] <Materials Used> Recycled container waste plastic (mixture of polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polyvinyl chloride, and polyvinylidene chloride; chlorine concentration: 1.5% by mass) The above chlorine concentration was measured on a powder sample of waste plastic using the procedure described in [Measurement Conditions for Combustion Ion Chromatography] below.

[0055] <Evaluation of Dechlorination> For powder samples of waste plastics, the signal originating from hydrogen chloride (HCl) was evaluated using a multi-turn high-resolution mass spectrometer. For the carbonization process, the sample was placed in a quartz tube installed in an electric furnace, and helium gas was flowed through the quartz tube at a rate of 100 ml / min from the upstream end. The electric furnace was then heated to 10°C / min, and while heating the sample, the generated gas was continuously introduced into the multi-turn high-resolution mass spectrometer as the flowing gas. The signal indicated by the mass-to-charge ratio (m / Z) = 35.98 was treated as the signal originating from HCl, and the dechlorination temperature during carbonization was measured. At this time, the mass spectrometer was adjusted to a resolution R > 5000 to separate and measure other trace gases appearing at the same mass number. Furthermore, since introducing the necessary helium gas and the entire amount of generated gas into the mass spectrometer would prevent the maintenance of vacuum within the apparatus, the amount of introduced gas was adjusted to approximately 10 ml / min, and the remaining gas was exhausted. The results are shown in Figure 3. As shown in Figure 3, the temperature at which the count of the hydrogen chloride (HCl)-derived signal began to increase with rising temperature was 253°C. Based on these results, the dechlorination temperature for recycled plastic containers was determined to be 253°C.

[0056] ≪Manufacturing of Granulated Materials≫ <Materials Used> Waste Plastic: Same as in <Preliminary Study Example 2> Ca-containing substance: Ca(OH)2 reagent (available from Kishida Chemical Co., Ltd., product number 000-13605, average diameter 6.6 μm)

[0057] <Granulation> [Examples 1-1 to 1-3] Ca(OH)2 powder was added to waste plastic so that the addition rate of Ca(OH)2 was 3.1% by mass (approximately 1.68% by mass on a Ca element basis) (Example 1-1), 5.0% by mass (approximately 2.70% by mass on a Ca element basis) (Example 1-2), and 9.0% by mass (approximately 4.87% by mass on a Ca element basis) (Example 1-3) relative to 100% by mass of waste plastic, and the mixture was uniformly mixed to obtain a material for granulation. This material was granulated in a granulator with a diameter (i.e., die hole diameter) of 6 mm at a granulation temperature of 240.0°C to obtain composite granules with a diameter of 6 mm. Note that when Ca(OH)2 is 3.1% by mass relative to 100% by mass of waste plastic, the amount of Cl and Ca elements in the waste plastic is equimolar.

[0058] [Comparative Example 1-1] By granulating waste plastic in a granulator with a diameter (i.e., die hole diameter) of 6 mm at a granulation temperature of 240.0°C, granules of waste plastic alone with a diameter of 6 mm were obtained.

[0059] [Comparative Example 1-2] Granules of waste plastic with a diameter of 6 mm were obtained using the same procedure as in Comparative Example 1-1, except that the granulation temperature was changed to 350.0°C.

[0060] [Comparative Example 1-3] A composite granule with a diameter of 6 mm was obtained using the same procedure as in Example 1-1, except that the granulation temperature was changed to 350.0°C.

[0061] [Comparative Example 1-4] A composite granule with a diameter of 6 mm was obtained using the same procedure as in Example 1-2, except that the granulation temperature was changed to 350.0°C.

[0062] [Comparative Example 1-5] A composite granule with a diameter of 6 mm was obtained using the same procedure as in Example 1-3, except that the granulation temperature was changed to 350.0°C.

[0063] [Comparative Example 1-6] A composite granule with a diameter of 6 mm was obtained using the same procedure as in Comparative Example 1-3, except that the addition rate of Ca(OH)2 was 15.7% by mass (approximately 8.49% by mass on a Ca element basis).

[0064] The granulation conditions for each example are summarized in Table 2.

[0065]

[0066] <Chlorine Concentration Measurement> The chlorine concentration of each granule was measured using the procedure described in [Measurement Conditions for Combustion Ion Chromatography] below. The results are shown in Figure 4. In Figure 4, the chlorine concentration of the granules is expressed as the amount relative to 100% by mass of waste plastic.

[0067] As shown in Figure 4, in granulation at 240.0°C (low-temperature granulation), there was no trend of increasing chlorine concentration in the granulated material with increasing Ca-containing substance addition. This is thought to be because, in low-temperature granulation, almost no dechlorination occurs from the waste plastic, and therefore chlorine immobilization by the Ca-containing substance did not occur. On the other hand, in granulation at 350.0°C (high-temperature granulation), the chlorine concentration was significantly lower than in the case of low-temperature granulation at an addition rate of 0% by mass of Ca-containing substance. This means that chlorine in the waste plastic was dechlorinated. In high-temperature granulation, the chlorine concentration tended to increase with increasing Ca-containing substance addition. This means that the dechlorinated chlorine was immobilized in the granulated material by the Ca-containing substance. These results indicate that, in the coexistence of waste plastic and Ca-containing material, even if the granulation temperature is set above the dechlorination temperature, it is difficult to obtain the benefits (i.e., reduction of chlorine concentration in the granules) that are obtained when the granulation temperature is set above the dechlorination temperature in the absence of Ca-containing material. Therefore, granulation below the dechlorination temperature is advantageous in terms of energy efficiency. Furthermore, at an addition rate of 15.7% by mass of Ca-containing material, the chlorine concentration was almost the same as at an addition rate of 5.0% by mass. At addition rates of 5.0% by mass and 15.7% by mass, the amount of Ca-containing material was excessive relative to the waste plastic, and it is thought that the increase in Ca-containing material did not contribute to the chlorine concentration.

[0068] <Carbonization Test> <Test Conditions> Using a test carbonization furnace, coal and chlorine-containing waste plastic were carbonized, and the organochlorine concentration in the generated gas was evaluated. The test conditions were as follows: Sample width: 415 mm Sample length: 490 mm Sample height: 460 mm Charged coal bulk density: approximately 0.80 dry-t / m 3 For all levels, carbonization was carried out at a carbonization temperature of 1050°C for 21 hours. During this process, the waste plastic was charged in a mixture with coal.

[0069] <Materials Used> Waste plastic: Same as in the <Granulated Material Production> Ca-containing material: Same as in the <Granulated Material Production> Coal: Crushed coal with a 3mm sieve ratio of 80% by mass, moisture content 4% by mass

[0070] <Carbonization Test> [Comparative Example 2-1] Waste plastic was granulated in a granulator with a diameter (i.e., die hole diameter) of 6 mm at a granulation temperature of 240.0°C to obtain granules of waste plastic alone with a diameter of 6 mm. 71.27 kg of coal and 3.56 kg of the obtained granules of waste plastic alone were carbonized using a test carbonization furnace. The amount of granules of waste plastic alone added was 5% by mass relative to 100% by mass of coal.

[0071] [Example 2-1] Ca(OH)2 powder was added to waste plastic so that the addition rate of Ca(OH)2 was 3.1% by mass relative to 100% by mass of the waste plastic, and the mixture was uniformly mixed to obtain a material for granulation. This material was granulated in a granulator with a diameter (i.e., die hole diameter) of 6 mm at a granulation temperature of 240.0°C to obtain composite granules with a diameter of 6 mm. 71.27 kg of coal and 3.56 kg of the obtained composite granules were carbonized. The amount of composite granules added was 5% by mass relative to 100% by mass of coal.

[0072] <Chlorine Concentration Measurement> Twenty minutes after the start of carbonization, a portion of the generated gas was sampled, bubbled in water, and then collected in an aluminum gas bag (capacity 1 L). The chlorine concentration of the gas in the gas bag was analyzed using combustion ion chromatography. The analytical conditions were as follows:

[0073] [Measurement Conditions for Combustion Ion Chromatography] The test was performed using a combustion IC consisting of a Nitto Seiko Analytech Co., Ltd. / AQF-2100H combustion section and a Thermo Fisher Scientific Co., Ltd. / Integrion RFIC IC section. The IC column was Dionex IonPac AS22, and 20 mM KOH was used as the eluent. The amount of gas sample introduced was 100 ml, and the sample was burned at a temperature of 1000°C with a gas atmosphere of Ar: 200 ml / min and O2: 400 ml mixed atmosphere, and chlorine was measured.

[0074] Here, inorganic chlorine (HCl) is removed by bubbling the generated gas in water, and it has been separately confirmed that inorganic chlorine is not actually present in the gas obtained by this process. Therefore, the chlorine concentration of the gas in the gas bag was considered to be the organic chlorine concentration. The results are shown in Figure 5.

[0075] Figure 5 shows the organic chlorine concentration of the generated gas sampled during carbonization. As shown in Figure 5, 20 minutes after the start of carbonization, the organic chlorine concentration in the generated gas was significantly reduced in Example 2-1, where 3.1% by mass of a Ca-containing substance was added, compared to Comparative Example 2-1, where no Ca-containing substance was added. Such a reduction in the organic chlorine concentration in the generated gas is advantageous for reducing the organic chlorine concentration in the product. From these results, it can be seen that the effect of reducing organic chlorine concentration by adding a Ca-containing substance can be obtained even with low-temperature granulation, and therefore, the effect of chlorine can be suppressed energy-efficiently by low-temperature granulation.

Claims

1. A method for producing composite granules containing chlorine-containing waste plastic and a Ca-containing substance for carbonization in the carbonization chamber of a coke oven, comprising granulating a material containing chlorine-containing waste plastic and a Ca-containing substance at a temperature below the dechlorination temperature of the waste plastic.

2. The method for producing a composite granule according to claim 1, wherein the granulation is carried out at a temperature of less than 250°C.

3. The method for producing a composite granule according to claim 1, wherein the granulation is carried out at a temperature of 100°C or higher.

4. A method for producing a composite granule according to claim 1, wherein the Ca-containing substance is kept isolated from the outside air from the time it is combined with the chlorine-containing waste plastic until it is subjected to granulation.

5. A method for treating waste plastics by carbonizing a composite granule containing chlorine-containing waste plastic and a Ca-containing substance in the carbonization chamber of a coke oven, comprising: producing a composite granule by a method for producing composite granules that includes granulating a material containing chlorine-containing waste plastic and a Ca-containing substance at a temperature below the dechlorination temperature of the waste plastic; and charging the composite granule into the carbonization chamber.

6. The waste plastic treatment method according to claim 5, wherein the granulation is performed at a temperature of less than 250°C.

7. The method for treating waste plastics according to claim 5, wherein the granulation is performed at a temperature of 100°C or higher.

8. The method for treating waste plastics according to claim 5, wherein coal is further charged into the carbonization chamber, and the amount of waste plastic charged as composite granules is 0.5% to 5% by mass relative to 100% by mass of the amount of coal charged.

9. The method for treating waste plastics according to claim 5, wherein the Ca-containing substance is kept isolated from the outside air from the time it is combined with the chlorine-containing waste plastic until it is subjected to granulation.

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