A device for reducing the volume of waste plastics by removing chlorine and a method for reducing the volume of waste plastics by removing chlorine

Abstract

This invention provides a waste plastic volume reduction and dechlorination apparatus and method that achieves high production efficiency and reduces equipment and operating costs by appropriately distributing chlorine-based polymers and waste plastics (Po) containing PET in a high-temperature environment. [Solution] The present invention provides a waste plastic volume reduction and dechlorination apparatus and a waste plastic volume reduction and dechlorination method using this apparatus, comprising: a) an optical sorting apparatus for sorting waste plastic Po into PET concentrated intermediate material Pp and PET removal intermediate material Pq; b) a first volume reduction extrusion apparatus for obtaining a volume reduction intermediate material Pv while removing moisture from the PET removal intermediate material Pq at 120 to 200°C; c) a dechlorination extrusion apparatus for discharging volume reduction and dechlorination waste plastic Px while separating hydrogen chloride by raising the temperature of the volume reduction intermediate material Pv to 250 to 400°C; and d) a second volume reduction extrusion apparatus for reducing the volume of PET concentrated intermediate material Pp while removing moisture at 120 to 200°C.

Description

Technical Field

[0001] The present invention relates to a volume reduction and dechlorination apparatus for waste plastics and a method for volume reduction and dechlorination of waste plastics, which perform volume reduction and dechlorination of waste plastics.

Background Art

[0002] In recent years, about 4 million tons of waste plastics are discharged annually as industrial waste and about 4 million tons are collected from households as general waste. Most of the waste plastics have been incinerated or landfilled conventionally, but in recent years, due to the increasing concern about environmental problems, approximately 85% of the total discharge has come to be recycled. However, about 70% of the recycling is thermal recycling, which incinerates waste plastics and recovers them as thermal energy, and the proportion recycled as raw materials remains at about 30%. From the perspective of the effect of reducing the environmental load, recycling that recycles as raw materials is more preferable, and its expansion is demanded.

[0003] Recycling for recycling as raw materials includes material recycling that recycles as plastic raw materials, and chemical recycling that recycles the gas and oil obtained by pyrolysis as fuels and chemical raw materials. As an example of this chemical recycling, there is a technique of pyrolyzing pretreated waste plastics together with coal using a coke oven, which is one of the iron-making processes, to recover hydrocarbon oil, coke oven gas (also referred to as COG), and coke. Since a coke oven is a large-scale facility capable of large-scale processing, there is great expectation for expanding the processing of waste plastics in a coke oven.

[0004] In the processing of waste plastics in coke ovens, for example, Patent Document 1 acknowledges the need to reduce the chlorine content in waste plastics to 0.5% by mass or less beforehand due to concerns about corrosion of the furnace body and exhaust gas treatment system, and the impact on product quality. However, waste plastics collected in the market mainly contain 6-10% by mass of chlorine-based polymers such as polyvinyl chloride. This amounts to approximately 3-5% by mass in terms of chlorine content in the waste plastics. Therefore, pre-treatment methods have been developed to reduce the chlorine content in waste plastics to 0.5% by mass or less. For example, there is a pre-treatment method that separates lightweight plastics and heavy plastics by specific gravity separation using a centrifuge, and selects only the lightweight plastics with low chlorine content. Such pre-treatment is time-consuming and complicated to apply to all collected waste plastics, and it has been technically difficult or resulted in a low yield to reduce the chlorine content in waste plastics from 3-5% by mass to 0.5% by mass.

[0005] To address these problems, Patent Document 1 discloses an invention that reduces the burden of pretreatment to lower the chlorine content in waste plastics to 0.5% by mass, or even eliminates the pretreatment altogether. Specifically, in the invention described in the same document, as shown in Figure 7, coal pre-mixed with about 1% by mass of waste plastic is carbonized in the carbonization chamber 32 of a coke oven 30 to produce coke 34. The pyrolysis gas containing chlorine-based gas generated by carbonization is guided through the furnace top space 38 above the charge in the carbonization chamber 32, and then through a riser pipe 40 located above the carbonization chamber 32 to a bend pipe (also called a riser pipe bend section) 42. The pyrolysis gas containing chlorine-based gas is cooled by ammonia water flushing from an ammonia water flushing device 44 in the bend pipe 42, and the chlorine-based gas is incorporated into ammonia water as ammonium chloride and detoxified by being discharged through a dry main 46.

[0006] On the other hand, as a pretreatment technology applicable to dechlorination of waste plastics before charging them into a coke oven, for example, the technology described in Patent Document 2, which dechlorinates waste plastics while reducing their volume to produce solid fuel, is known. Specifically, the waste plastic solid fuel production apparatus 50 described in Patent Document 2, as shown in Figure 8, includes a volume reduction extruder 52 that kneads the waste plastics Po, weighed by a weighing machine 51, with a screw while heating it with a heater 53, thereby reducing its volume and removing water vapor. Furthermore, it includes a dechlorination extruder 54 that stirs the softened waste plastics with a screw while heating them with a heater 55 to separate the chlorine as hydrogen chloride. The gasified hydrogen chloride is then neutralized in a hydrogen chloride treatment apparatus 56 by dissolving it in water and reacting it with an alkali such as sodium hydroxide. As a result, water vapor and hydrogen chloride are selectively separated and removed, allowing hydrogen chloride to be efficiently removed by a small hydrogen chloride treatment apparatus 56. The waste plastic from which chlorine has been removed is continuously discharged from the dechlorination extruder 54, and in the granulation and cooling / dewatering device 57, it is cut to a predetermined length, cooled and solidified in water, and then dewatered. This waste plastic is then transported to a container 59 by a conveyor 58 as needed.

[0007] Furthermore, Patent Document 3 discloses an invention that combines a specific gravity separation means and an optical sorting means in order to separate plastics with a high chlorine content (chlorine-based polymers) and increase the recovery rate of recyclable plastics with reduced chlorine content. Specifically, in the invention described in the same document, as shown in Figure 9, plastics are separated according to their specific gravity, and the separated plastics Sa and Sb are sorted by an optical sorting device 70 based on the difference in wavelength absorption depending on the material. The optical sorting device 70 is composed of a control unit 71, a conveyor 72 having rollers 72a, a near-infrared sensor 73, a gas supply unit 74, a gas injection unit 75, and a recovery unit having separation and recovery trays 76a and 76b. The near-infrared sensor 73 identifies the material of the waste plastic by irradiating the waste plastic on the conveyor 72 with near-infrared light L and receiving the reflected near-infrared light. The control unit 71 controls the gas supply unit 74 based on the input sensor information, thereby performing an air jet at a predetermined timing, injecting gas A, such as air, from the gas injection unit 75 on the discharge side of the conveyor 72. This sorts the waste plastics Sa and Sb of different materials. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2000-104075 [Patent Document 2] Japanese Patent Application Publication No. 11-050072 [Patent Document 3] Japanese Patent Publication No. 2023-106978 [Overview of the project] [Problems that the invention aims to solve]

[0009] Incidentally, in the treatment of waste plastics containing chlorine-based polymers in a coke oven related to the invention described in Patent Document 1, the amount of waste plastics input is small, about 1% by mass of the coke amount, and coupled with improvements since the invention, prior dechlorination treatment was sometimes omitted. Nevertheless, in recent years, there has been an increasing demand for an increase in the amount of waste plastics processed in coke ovens, in order to realize a low-carbon society and a circular economy, and furthermore, to aim for a net-zero carbon society.

[0010] To meet the demand for increased processing volume of waste plastics in coke ovens, it becomes necessary to fully adopt waste plastic dechlorination technology, such as the invention described in Patent Document 2, as a pretreatment for waste plastic processing in coke ovens. On the other hand, in the invention described in Patent Document 2, if the total volume of waste plastics to be processed is to be raised to around 300°C or higher, a large amount of thermal energy will be consumed. Such an increase in thermal energy required for pretreatment could be counterproductive to achieving the low-carbon society that we aim for, and there is room for improvement in the high-energy-load dechlorination treatment described in Patent Document 2.

[0011] Furthermore, while the invention described in Patent Document 3 is also promising for the pretreatment of waste plastics containing chlorine-based polymers using a coke oven, the specific gravity separation method in the invention described in that document utilizes the difference in specific gravity in water, and the resulting equipment load on water treatment facilities and other equipment is significant, so there is room for improvement.

[0012] The present inventors focused on the problem of reducing the large amount of thermal energy required in the dechlorination extrusion apparatus described in Patent Document 2, among the problems found in such prior art, and investigated the effect of the type of plastic in waste plastics. As a result, they found that polyethylene terephthalate (PET), which is generally contained in waste plastics collected from the city at a concentration of about 5 to 20% by mass, reduces the dechlorination rate (see Figure 1), and that higher temperature processing is required to restore the dechlorination rate.

[0013] Therefore, the present invention aims to provide a waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method that use a dry optical sorting means to ensure proper distribution of PET pre-removal and dechlorination treatment, thereby increasing production efficiency and suppressing equipment and operating costs. [Means for solving the problem]

[0014] [1] A waste plastic volume reduction and dechlorination apparatus that reduces the volume of waste plastic Po, which consists of multiple types of materials including chlorine polymers and polyethylene terephthalate (PET), and dechlorinates it to obtain a waste plastic agglomerate that is substantially free of chlorine polymers, (a) A PET target optical sorting device that sorts the waste plastic Po, which is supplied in a state of being crushed to a predetermined size, into a PET concentrated intermediate material Pp, which is obtained by selectively concentrating PET, and a PET removed intermediate material Pq, which is obtained by selectively removing PET, based on the difference in wavelength absorption depending on the material. (b) A first volume reduction extruder that reduces the volume of the PET removal intermediate material Pq by raising the resin temperature to 120°C or higher and 200°C or lower, thereby removing moisture as water vapor and obtaining a volume reduction intermediate material Pv, (c) A dechlorination extruder that separates chlorine mainly as hydrogen chloride gas from the volume-reducing intermediate material Pv while raising the resin temperature to 250°C or higher and 400°C or lower, exhausts the gas, and discharges a volume-reducing, dechlorinated waste plastic Px that is substantially free of chlorine-based polymers, (d) A second volume reduction extruder that reduces the volume of the PET concentrated intermediate material Pp by raising the resin temperature to 120°C or higher and 200°C or lower, while removing moisture as water vapor, in order to obtain volume reduction waste plastic Py, A waste plastic volume reduction and dechlorination device.

[0015] [2](e) The PET optical sorting apparatus is further equipped with a first chlorine-based optical sorting apparatus that sorts the waste plastic Po into a chlorine-based concentrated intermediate material Pc, which is obtained by selectively concentrating chlorine-based polymers based on differences in wavelength absorption depending on the material, and a chlorine-based removed intermediate material Pd, which is obtained by selectively removing chlorine-based polymers. (a1) The PET optical sorting apparatus receives the chlorine-based concentrated intermediate material Pc instead of the waste plastic Po, and sorts the chlorine-based concentrated intermediate material Pc into a chlorine-based concentrated PET intermediate material Pcp, which is obtained by selectively concentrating PET based on the difference in wavelength absorption depending on the material, and a chlorine-based concentrated PET removal intermediate material Pcq, which is obtained by selectively removing PET. (b1) The first volume reduction extruder receives the chlorine-based concentrated PET removal intermediate material Pcq instead of the PET removal intermediate material Pq, (d1) The waste plastic volume reduction and dechlorination apparatus described in [1], wherein the second volume reduction extrusion apparatus receives the chlorine-based removal intermediate material Pd and the chlorine-based concentrated PET concentrated intermediate material Pcp instead of the PET concentrated intermediate material Pp.

[0016] [3](a2) The waste plastic volume reduction and dechlorination apparatus according to [2], wherein the supply destination of the chlorine-based concentrated PET concentrated intermediate material Pcp, which has been sorted by the PET target optical sorting apparatus, is changed from the second volume reduction extruder to the first chlorine-based target optical sorting apparatus.

[0017] [4](f) The transport path of the chlorine-removing intermediate material Pd sorted by the first optical sorting device for chlorine-removing materials is further provided with a second optical sorting device for chlorine-removing materials that sorts the chlorine-removing intermediate material Pd into a chlorine-removing residual concentrated intermediate material Pdc, which is obtained by selectively concentrating the chlorine-removing polymer based on the difference in wavelength absorption depending on the material, and a chlorine-removing repeated intermediate material Pdd, which is obtained by selectively removing the chlorine-removing polymer. (b2) The first volume reduction extruder receives the chlorine-based concentrated PET removal intermediate material Pdc in addition to the chlorine-based remaining concentrated intermediate material Pcq, (d2) The second volume reduction extrusion device is the waste plastic volume reduction and dechlorination device according to [2], which receives the supply of the chlorine-based removal repeating intermediate material Pdd in addition to the chlorine-based concentrated PET concentrated intermediate material Pcp.

[0018] [5](a3) The supply destination of the chlorine-based concentrated PET concentrated intermediate material Pcp, in which PET is selectively concentrated by the PET target optical sorting device, is changed to the chlorine-based target second optical sorting device instead of the second volume reduction extrusion device, and (f1) The supply destination of the chlorine-based removal residual concentrated intermediate material Pdc, in which chlorine-based polymers are selectively concentrated by the chlorine-based target second optical sorting device, is changed to the PET target optical sorting device instead of the first volume reduction extrusion device. The waste plastic volume reduction and dechlorination device according to [4].

[0019] [6] A waste plastic volume reduction and dechlorination method for reducing the volume of waste plastic Po composed of a plurality of materials including chlorine-based polymers and polyethylene terephthalate (PET) while dechlorinating to obtain a mass product of waste plastic substantially free of chlorine-based polymers, comprising: (a) The waste plastic Po supplied in a crushed state of a predetermined size is sorted into a PET concentrated intermediate material Pp in which PET is selectively concentrated and a PET removed intermediate material Pq in which PET is selectively removed by using an optical sorting device based on the difference in absorbance of wavelengths according to the material. This is a PET target optical sorting step. (b) The PET removed intermediate material Pq is heated using an extrusion device to a resin temperature of 120°C or higher and 200°C or lower to remove moisture as water vapor while reducing the volume to obtain a volume reduction intermediate material Pv. This is the first volume reduction extrusion step. (c) From the volume reduction intermediate material Pv, using an extrusion device, while heating to a resin temperature of 250°C or higher and 400°C or lower, chlorine is mainly separated as hydrogen chloride gas and exhausted, and at the same time, a volume reduction and dechlorination waste plastic Px substantially free of chlorine-based polymers is discharged. This is a dechlorination extrusion step. (d) A second volume reduction extrusion step of subjecting the PET concentrated intermediate Pp to heating using an extrusion device to raise the temperature to 120°C or higher and 200°C or lower, reducing the volume while removing moisture as water vapor to obtain a volume-reduced waste plastic Py. A method for volume reduction and dechlorination of waste plastics having

[0020] [7](e) Before the PET target optical sorting step, the waste plastic Po is sorted into a chlorine-based concentrated intermediate Pc in which chlorine-based polymers are selectively concentrated and a chlorine-based removed intermediate Pd in which chlorine-based polymers are selectively removed based on the difference in absorbance of wavelengths by material, further comprising a chlorine-based target first optical sorting step. (a1) In the PET target optical sorting step, instead of the waste plastic Po, the supply of the chlorine-based concentrated intermediate Pc is received, and based on the difference in absorbance of wavelengths by material, the chlorine-based concentrated intermediate Pc is sorted into a chlorine-based concentrated PET concentrated intermediate Pcp in which PET is selectively concentrated and a chlorine-based concentrated PET removed intermediate Pcq in which PET is selectively removed. (b1) In the first volume reduction extrusion step, instead of the PET removed intermediate Pq, the supply of the chlorine-based concentrated PET removed intermediate Pcq is received. (d1) In the second volume reduction extrusion step, instead of the PET concentrated intermediate Pp, the supply of the chlorine-based removed intermediate Pd and the chlorine-based concentrated PET concentrated intermediate Pcp is received. The method for volume reduction and dechlorination of waste plastics according to [6].

[0021] [8](a2) The method for volume reduction and dechlorination of waste plastics according to [7], wherein the supply destination of the chlorine-based concentrated PET concentrated intermediate Pcp sorted in the PET target optical sorting step is replaced from the second volume reduction extrusion step to the chlorine-based target first optical sorting step.

[0022] [9](f) The transport path of the chlorine-removing intermediate material Pd sorted in the first optical sorting step for chlorine-removing materials further comprises a second optical sorting step for chlorine-removing materials, which sorts the chlorine-removing intermediate material Pd into a chlorine-removing residual concentrated intermediate material Pdc, which has been selectively concentrated with chlorine-removing polymers based on differences in wavelength absorption depending on the material, and a chlorine-removing repeated intermediate material Pdd, which has been selectively removed with chlorine-removing polymers. (b2) The first volume reduction extrusion process receives the chlorine-based concentrated PET removal intermediate material Pcq in addition to the chlorine-based remaining concentrated intermediate material Pdc, (d2) The method for reducing the volume of waste plastics by dechlorinating them according to [7], wherein the second volume reduction extrusion step is to receive the chlorine-based concentrated PET concentrated intermediate material Pcp in addition to the chlorine-based repeated removal intermediate material Pdd.

[0023]

[10] (a3) The supply destination of the chlorine-based concentrated PET intermediate material Pcp obtained by selectively concentrating PET in the PET target optical sorting process is changed from the second volume reduction extrusion process to the chlorine-based second optical sorting process, (f1) The method for reducing the volume of waste plastics by dechlorinating (f1) the chlorine-based polymer selectively concentrated in the second optical sorting step for chlorine-based polymers, wherein the supply destination of the chlorine-based residual concentrated intermediate material Pdc obtained by selectively concentrating the chlorine-based polymer in the second optical sorting step for chlorine-based polymers is replaced with the first volume reduction extrusion step by the optical sorting step for PET. [Effects of the Invention]

[0024] According to the present invention, in the dechlorination treatment of waste plastics containing chlorine polymers, PET, which reduces the dechlorination rate and requires high-temperature treatment, can be removed in advance by an optical sorting means, thereby optimizing the thermal energy required for dechlorination treatment. Furthermore, according to the present invention, by subjecting only the waste plastics containing chlorine polymers sorted by the optical sorting means to the energy-intensive dechlorination treatment, it is possible to contribute to the appropriate allocation and efficiency of dechlorination treatment, and ultimately to the realization of a net-zero carbon society. Moreover, according to the present invention, by employing a dry optical sorting means instead of a specific gravity separation means that involves water treatment equipment with a large equipment load for sorting waste plastics containing chlorine polymers, it is possible to increase production efficiency and suppress equipment costs and operating costs. As described above, the present invention provides a waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method that offer high production efficiency, suppress equipment costs and operating costs, and ultimately contribute to the realization of a net-zero carbon society. [Brief explanation of the drawing]

[0025] [Figure 1] This figure shows the effect of PET content on the efficiency of dechlorination treatment of waste plastics. [Figure 2] This is a block diagram illustrating, in general terms, the equipment arrangement of a waste plastic volume reduction and dechlorination apparatus and the flow of a waste plastic volume reduction and dechlorination method according to one embodiment of the present invention. [Figure 3] This block diagram schematically illustrates the equipment arrangement of a waste plastic volume reduction and dechlorination apparatus and the flow of a waste plastic volume reduction and dechlorination method according to another embodiment of the present invention. [Figure 4] This is a block diagram illustrating, in general terms, the equipment arrangement of a waste plastic volume reduction and dechlorination apparatus and the flow of a waste plastic volume reduction and dechlorination method according to yet another embodiment of the present invention. [Figure 5] This is a block diagram illustrating, in general terms, the equipment arrangement of a waste plastic volume reduction and dechlorination apparatus and the flow of a waste plastic volume reduction and dechlorination method according to yet another embodiment of the present invention. [Figure 6] This is a block diagram illustrating, in general terms, the equipment arrangement of a waste plastic volume reduction and dechlorination apparatus and the flow of a waste plastic volume reduction and dechlorination method according to yet another embodiment of the present invention. [Figure 7] This diagram illustrates a conventional method for processing waste plastics containing chlorine-based polymers using a coke oven, using a schematic cross-sectional view of the inside of the coke oven. [Figure 8] This diagram schematically illustrates the configuration of a conventional waste plastic volume reduction and dechlorination apparatus. [Figure 9] This diagram provides a schematic explanation of the configuration of a conventional optical sorting device for waste plastics. [Modes for carrying out the invention]

[0026] Embodiments of the present invention will be described in detail below with reference to the drawings. In the embodiments shown below, the same or common parts are denoted by the same reference numerals in the drawings, and their descriptions will not be repeated. However, the present invention is not limited to the embodiments shown below.

[0027] (First Embodiment) Figure 1 shows the time dependence of the dechlorination rate of waste plastics using an extruder at a test temperature of 350°C, for two levels of waste plastics: one containing 19% by mass of polyvinyl chloride (PVC) and either no polyethylene terephthalate (PET) or 15% by mass of PET. From Figure 1, it can be easily inferred that PET, which is generally present in waste plastics collected from the public at around 5-20% by mass, reduces the dechlorination rate of waste plastics containing chlorine-based polymers when treated with an extruder. Furthermore, it can be seen that it is necessary to increase the treatment temperature or extend the treatment time (residence time) to avoid this effect. Therefore, in the waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method according to this embodiment, an optical sorting apparatus is used to selectively remove PET from the waste plastic before dechlorination treatment.

[0028] Figure 2 is a block diagram schematically illustrating the equipment arrangement of the waste plastic volume reduction and dechlorination apparatus 1 according to the first embodiment, and the flow of the waste plastic volume reduction and dechlorination method. As shown in Figure 2, the waste plastic volume reduction and dechlorination apparatus 1 comprises a PET target optical sorting apparatus 10p for sorting PET, a first volume reduction extruder 12, a dechlorination extruder 14, and a second volume reduction extruder 20. This allows for dechlorination at lower temperatures and improves energy efficiency by pre-removing PET from the waste plastic to be subjected to dechlorination treatment using the optical sorting apparatus, which would reduce the dechlorination rate and require high-temperature treatment.

[0029] In this embodiment, as shown in Figure 2, waste plastic Po, which consists of multiple types of materials including chlorine-based polymers and PET, is dechlorinated while reducing its volume to obtain a mass of waste plastic that is substantially free of chlorine-based polymers. In this embodiment, the following configuration is adopted. (a) In the PET optical sorting device 10p or the PET optical sorting process, waste plastic Po is sorted into a PET concentrated intermediate material Pp, in which PET is selectively concentrated, and a PET removed intermediate material Pq, in which PET is selectively removed, based on the difference in wavelength absorption depending on the material. Furthermore, the waste plastic (Po) supplied shall be supplied in a state where it has been crushed to a predetermined size beforehand.

[0030] (b) In the first volume reduction extrusion apparatus 12 or the first volume reduction extrusion process, the PET removal intermediate material Pq is heated to a resin temperature of 120°C or higher and 200°C or lower, and the volume is reduced while removing moisture as water vapor to obtain a volume reduction intermediate material Pv. (c) In the dechlorination extrusion apparatus 14 or the dechlorination extrusion process, chlorine is separated from the volume-reduced intermediate material Pv as mainly hydrogen chloride gas while the resin temperature is raised to 250°C or higher and 400°C or lower, and exhausted. At the same time, the dechlorination extrusion apparatus 14 or the dechlorination extrusion process discharges volume-reduced dechlorinated waste plastic Px that is substantially free of chlorine-based polymers. Furthermore, the volume-reduced and dechlorinated waste plastic Px used here is substantially free of chlorine-based polymers and is in a semi-molten state.

[0031] Here, it is desirable to provide a hydrogen chloride treatment device or hydrogen chloride treatment process (not shown) as an ancillary facility or ancillary process for recovering and treating the hydrogen chloride-containing gas exhausted from the dechlorination extruder 14. It is also desirable to provide a first granulation cooling device or first granulation cooling process (not shown) as an ancillary facility or ancillary process for cutting and cooling the volume-reduced dechlorinated waste plastic Px discharged from the dechlorination extruder 14.

[0032] (d) In the second volume reduction extrusion apparatus 20 or the second volume reduction extrusion process, the PET concentrated intermediate material Pp is heated to a resin temperature of 120°C or higher and 200°C or lower, and the volume is reduced while removing moisture as water vapor to obtain volume reduction waste plastic Py. Here, it is desirable to also provide a second granulation cooling device or a second granulation cooling process (not shown) as an ancillary equipment or process for cutting and cooling the volume-reduced waste plastic Py.

[0033] The volume-reduced and dechlorinated waste plastics Px and Py obtained in this way can be used, for example, as raw materials for coke ovens as a chemical recycling destination, but are not limited to this; they can also be used, for example, as solid fuels as a thermal recycling destination.

[0034] The waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method according to the first embodiment will be further described below, mainly with reference to Figure 2, and also with reference to Figures 8 and 9 relating to the background art of the present invention.

[0035] (Waste plastics to be processed) In this embodiment, the waste plastics (Po) targeted are generally assumed to be waste plastics collected from the public, such as waste plastics discharged by local governments under the Container and Packaging Recycling Law. Here, as an example of the composition of waste plastics generally collected from the public, the chlorine-based polymers mainly consist of polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC) at approximately 0-5% by mass, which translates to approximately 0-2% by mass in terms of chlorine content. On the other hand, the majority of the plastics constituting waste plastics other than chlorine-based polymers are polyethylene (PE), polypropylene (PP), polystyrene (PS), etc., with polyethylene terephthalate (PET) also present at approximately 5-20% by mass.

[0036] Based on these circumstances, the chlorine-based polymers contained in the waste plastic Po targeted in this embodiment are primarily assumed to be polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC). In this embodiment, the chlorine-based polymers contained in the waste plastic Po may also include chlorinated polyethylene (CPE), chlorinated polypropylene (CPP), and the like. Furthermore, the waste plastic Po targeted in this embodiment includes polyethylene terephthalate (PET). Furthermore, the waste plastics Po targeted in this embodiment include polyethylene (PE), polypropylene (PP), polystyrene (PS), and the like, as waste plastics other than chlorine-based polymers and PET.

[0037] For reference, Table 1 shows an example of the component composition of waste plastics (Po) containing chlorine-based polymers collected from the city, and Table 2 shows an example of the composition of plastics.

[0038] [Table 1]

[0039] [Table 2]

[0040] Furthermore, the method for measuring the chlorine content in waste plastics, which was used as needed in this embodiment, will be explained. Ten kg of waste plastics, such as waste plastics (Po) collected in the city, are crushed to approximately 10-20 mm using a cutter mill. The crushed waste plastics are then divided into 20 g / lots by repeatedly using the quartic method to obtain a representative sample. This sample is freeze-crushed and powdered. For qualitative analysis, the powder is analyzed by X-ray fluorescence analysis to obtain a percentage-order analysis result. For quantitative analysis, the amount of Cl ions in the chloride obtained by the cylinder-type Cl content test method of JIS K 2541 "Test Method for Sulfur Content of Crude Oil and Petroleum Products" is measured by ion chromatography and converted to the total Cl amount. This result is used as the average value of the chlorine content.

[0041] In this embodiment, the waste plastic Po is subjected to pretreatment such as removal of foreign matter, crushing, and weighing. For example, in the removal of foreign matter, it is preferable to remove foreign matter such as metal mixed in with the waste plastic Po in advance by methods such as air separation, manual sorting, or mechanical sorting. Furthermore, the supplied waste plastic (Po) is crushed to a predetermined size beforehand. Preferably, the crushed waste plastic (Po) is crushed using a crusher with a screen size of 40 mm to 100 mm. Pre-crushing the supplied waste plastic greatly improves the sorting accuracy in the optical sorting process. Also, if the screen size of the crusher used for crushing is less than 40 mm, it takes a long time to crush, which is undesirable. Furthermore, if the screen size exceeds 100 mm, the bulk density tends to decrease, which negatively affects the workability in subsequent processes, and is therefore undesirable. Specifically, it is particularly preferable to use a crusher with a screen size of about 100 mm.

[0042] (Optical sorting device) As an example of the optical sorting device 10, we will explain using the PET-targeting optical sorting device 10p shown in Figure 2. The chlorine-targeting first optical sorting device 10c1 and the chlorine-targeting second optical sorting device 10c2, which will be described later, are similar in that they sort the target resin and remove the resin that is not to be sorted. In the following explanation, these optical sorting devices may be simply referred to as sorting device 10p, sorting device 10c1, and sorting device 10c2. Furthermore, instead of using the waste plastic name and code derived from the sorting device to represent the intermediate waste plastic sorting material separated by these optical sorting devices, the following explanation may use a simplified representation as shown in the example below. Specifically, in the example of "chlorine-based concentrated PET concentrated intermediate material Pcp," the waste plastic name may be simplified to "intermediate material," resulting in the simple notation "intermediate material Pcp."

[0043] The PET optical sorting device 10p is a device that sorts waste plastic Po into PET concentrated intermediate material Pp, which is obtained by selectively concentrating PET based on the difference in wavelength absorption depending on the material, and PET removed intermediate material Pq, which is obtained by selectively removing PET. This PET optical sorting device 10p can employ a known optical sorting device that can be adjusted to sort PET as the sorting target. The PET concentrated intermediate material Pp sorted by the PET optical sorting device 10p is reduced in volume in the second volume reduction extrusion device 20 in the subsequent process to become volume-reduced waste plastic Py.

[0044] In this context, "absorption of wavelengths by material" can be rephrased as "absorption spectrum of wavelengths by material" or "frequency spectrum of reflected light by material."

[0045] Generally, optical sorting devices are known sorting devices that can automatically sort various types of waste plastics and foreign matter, as employed in the invention described in Patent Document 3, and sort materials according to the conditions. The sorting accuracy of optical sorting devices varies depending on the material composition and the degree of foreign matter contamination, but it is generally said to be around 70% to 90% in terms of sorting rate (10% to 30% in terms of unsorted material rate). If high-precision sorting is required, it can be improved by reducing the supply rate within a range where a decrease in production volume is acceptable, while maintaining or increasing the conveyor speed.

[0046] The general mechanism of an optical sorting device is to shine near-infrared light or similar on materials being dispersed and transported on a conveyor belt, analyze the frequency spectrum of the reflected light detected by an optical sensor to identify the material type, and then separate up to three types of materials by jet spray at the end of the conveyor. The jet spray separation method involves, for example, using a downward jet of air to direct the material towards the conveyor, an upward jet to direct it towards the conveyor farther away, and stopping the jet (allowing natural fall) to direct it towards the intermediate section. When separating into two types of materials, it is preferable to simplify the jet spray path while achieving material separation by using only one of the two jet directions (upward or downward) and combining it with stopping the jet (allowing natural fall) (see Figure 9).

[0047] (Volume reduction extrusion machine) The first volume reduction extruder 12 and the second volume reduction extruder 20 (also simply referred to as volume reduction extruders 12 and 20) are both composed of extruders and can employ known devices for reducing the volume of waste plastics (see volume reduction extruder 52 in Figure 8). Each of the volume reduction extruders 12 and 20 has a cylinder, a supply port such as a hopper for receiving waste plastics (intermediate material Pp or Pq) from the previous process, a screw for kneading the received waste plastics, and an outlet for discharging the reduced-volume waste plastic. Furthermore, the volume reduction extruders 12 and 20 have a vent (exhaust port) for exhausting water vapor generated from water adhering to the waste plastics due to the temperature rise during volume reduction. In the volume reduction extruders 12 and 20, the waste plastics are heated by the frictional heat generated when the screw kneads them. If further heating of the waste plastics is required, a heating device such as a jacket heater for heating the waste plastics may be provided in the cylinder.

[0048] In the volume reduction extruders 12 and 20, operating conditions such as the screw rotation speed, heating temperature by the heating device, and heating time are adjusted so that the temperature of the waste plastic is between 120°C and 200°C. By keeping the temperature of the waste plastic at this temperature, volatile components that do not contain chlorine compounds (such as hydrogen chloride), such as water vapor, are exhausted. The waste plastic is softened by the frictional heat generated by screw kneading and by heating by the heating device. The softened waste plastic is reduced in volume by kneading, and some waste plastics with low glass transition points, such as polystyrene, melt and fill the voids, and the reduced volume material is pushed out from the cylinder outlet.

[0049] When the temperature of waste plastic exceeds 120°C, at least low-density polyethylene (low-density PE), which has a glass transition temperature of approximately 110°C, and polystyrene (PS), which has a glass transition temperature of approximately 80°C, melt, allowing for efficient volume reduction of partially molten waste plastic. On the other hand, when the temperature of waste plastic exceeds 200°C, the thermal decomposition of polyvinyl chloride (PVC) in the waste plastic generates hydrogen chloride and other substances, so the temperature of waste plastic must be kept below 200°C.

[0050] In the volume reduction extruders 12 and 20, the residence time during which the waste plastic is held at a temperature of 120°C to 200°C is preferably between 1 minute and 5 minutes. By allowing the waste plastic to remain at this temperature for this duration in the volume reduction extruders 12 and 20, volatile components other than hydrogen chloride, such as water vapor, are effectively removed.

[0051] The volume-reduced intermediate material Pv extruded from the volume-reducing extruder 12 is supplied directly to the next process, the dechlorination extruder 14. The volume-reduced waste plastic Py is also extruded from the volume-reducing extruder 20.

[0052] (Dechlorination extrusion device) A known dechlorination extruder 14 can be connected to the discharge port of the volume reduction extruder 12 and separate the chlorine contained in the volume reduction intermediate material Pv to discharge volume reduction dechlorinated waste plastic Px that is substantially free of chlorine-based polymers (see dechlorination extruder 54 in Figure 8). Furthermore, the statement that the volume-reduced, dechlorinated waste plastic Px, which is part of the final product of this embodiment, "substantially does not contain chlorine-based polymers" means that the chlorine content is 1% by mass or less. This is based on the consideration that waste plastics with a chlorine content of 1% by mass or less can be chemically recycled in a coke oven, as disclosed in Patent Document 1.

[0053] Here, we also examine the chlorine content of Py, another final product in this embodiment. Py contains PET corresponding to the PET sorting rate (e.g., 90%) in the PET optical sorting device 10p, and also contains waste plastics other than PET corresponding to the over-sorting rate (e.g., 8%). Therefore, the chlorine content derived from the waste plastics due to this over-sorting rate is also important. When we estimate the mass balance by optical sorting in this embodiment, we confirm that the chlorine concentration in Py, which has passed through the PET concentrated intermediate material Pp, is 1% by mass or less, as shown in Table 3 later, and that it is essentially a waste plastic that does not contain chlorine-based polymers. This is consistent with the qualitative understanding that chlorine-based polymers are relatively diluted in the PET concentrated intermediate material Pp, in which PET is concentrated in the PET optical sorting device 10p. Table 3 shows the chlorine concentration of the PET concentrated intermediate material Pp before volume reduction. However, since the temperature is not raised to a level sufficient for dechlorination during the volume reduction process, the PET concentrated intermediate material Pp and the volume-reduced waste plastic Py are assumed to have the same chlorine concentration.

[0054] The dechlorination extruder 14 is composed of an extruder similar to that of the volume reduction extruder 12. Specifically, the dechlorination extruder 14 has a cylinder, a supply port for receiving the volume-reduced intermediate material Pv, a screw for stirring the waste plastic, and an outlet for discharging the volume-reduced dechlorinated waste plastic Px from which the chlorine has been separated. Furthermore, the dechlorination extruder 14 has a vent (exhaust port) for exhausting chlorine compounds (such as hydrogen chloride) generated by thermal decomposition. The cylinder is also equipped with a heating device such as a jacket heater for heating the waste plastic.

[0055] In the dechlorination extruder 14, the following are adjusted as operating conditions: (1) the rotation speed of the screw, (2) the heating temperature and heating time of the heating device, and (3) the overall processing temperature, processing time (residence time), and processing speed of the entire device, including the screw and heating device. The processing speed here has a negative correlation with the processing temperature and processing time. These operating conditions are adjusted so that the temperature of the waste plastic is between 250°C and 400°C. When the waste plastic is heated to this temperature range, chlorine-based polymers such as polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC) contained in the waste plastic are thermally decomposed. If the heating temperature is below 250°C, the chlorine-based polymers in the waste plastic will not be sufficiently thermally decomposed, and the thermal decomposition will take a long time, making the dechlorination extruder 14 large, which is undesirable. If the processing temperature exceeds 400°C, the volatilization loss of the waste plastic will be large, resulting in poor yield, and it will also consume excess energy relative to the dechlorination performance, which is economically undesirable. Furthermore, when the processing temperature exceeds 400°C, the amount of volatilization of other components may exceed that of the chlorine-based polymer, potentially leading to an increased residual chlorine concentration.

[0056] Furthermore, the processing time (residence time) for the waste plastic to reach a temperature of 250°C to 400°C is preferably in the range of 1 minute to 6 minutes. If the residence time is less than 1 minute, the chlorine-based polymers in the waste plastic will not be sufficiently thermally decomposed, and if the residence time exceeds 6 minutes, the volatilization loss of the waste plastic will be large, resulting in a poor yield and the consumption of excess energy, which is economically undesirable.

[0057] In this embodiment, as described above, based on the finding that PET contained in waste plastics in the market reduces the dechlorination rate of waste plastics containing chlorine polymers when treated with an extruder, PET is removed from the waste plastics by optical sorting. The inventors investigated the relaxation of the upper limit temperature for dechlorination treatment when PET is removed from waste plastic in this manner, using operational data from actual equipment. As a result, they confirmed that if the PET concentration of the waste plastic intermediate material supplied to the dechlorination extruder is reduced to less than 3% by mass, there is no decrease in the dechlorination rate due to PET even when the treatment temperature for dechlorination treatment is lowered to 350°C or below. Therefore, it is preferable to improve the efficiency of energy requirements by setting the upper limit of the dechlorination treatment temperature to 350°C when the PET concentration of the waste plastic subjected to dechlorination treatment is less than 3% by mass, and setting the upper limit of the dechlorination treatment temperature to 400°C when the PET concentration is 3% by mass or more.

[0058] (Hydrogen chloride treatment device) The hydrogen chloride treatment device (not shown) is a device that detoxifies gas containing hydrogen chloride, which is harmful in its raw state, and it is preferable to provide it as an auxiliary device in this embodiment. Specifically, the hydrogen chloride treatment device can be a known device that is connected by piping to the exhaust port of the dechlorination extruder 14 and recovers and treats gas containing hydrogen chloride (hydrogen chloride-containing gas). The hydrogen chloride-containing gas here includes not only hydrogen chloride but also organic gases (for example, pyrolysis gases of polystyrene (PS), polypropylene (PP), polyethylene terephthalate (PET), etc., which tend to be generated on the high-temperature side of the processing temperature range), and small amounts of air in the volume reduction product from the previous process. The hydrogen chloride treatment device burns the hydrogen chloride-containing gas and then dissolves the hydrogen chloride in water to recover it as hydrochloric acid. After the hydrogen chloride is converted to hydrochloric acid, it can also be neutralized by reacting it with an alkali such as sodium hydroxide. An exhaust pump is interposed in the piping, and the gas is guided to the hydrogen chloride treatment device by the suction (negative pressure) of the exhaust pump.

[0059] (granulation cooling device) It is preferable to provide a first granulation cooling device (not shown) on the discharge side of the dechlorination extruder 14, and a second granulation cooling device (not shown) on the discharge side of the second volume reduction extruder, as auxiliary devices in this embodiment to facilitate subsequent processing. These first and second granulation cooling devices can employ known devices that cool and granulate the volume-reduced dechlorinated waste plastic Px and volume-reduced waste plastic Py, which are extruded in a rod shape from the dies on the discharge side of the dechlorination extruder 14 and the second volume reduction extruder 20, by cutting them with a cutter or the like. The granulation cooling device here has a known function of cooling and solidifying the granulated volume-reduced dechlorinated waste plastic Px and volume-reduced waste plastic Py, for example in water, and then dewatering them. The volume-reduced dechlorinated waste plastic Px and volume-reduced waste plastic Py after being dewatered in the granulation cooling device are then used for chemical recycling in a coke oven or the like, or for thermal recycling as fuel.

[0060] (Estimate of material balance in optical sorting in the first embodiment) Here, we will explain the results of our calculation of the material balance when sorting waste plastic Po using the PET optical sorting device 10p in this embodiment. Note that this embodiment is not limited to the calculation results described below.

[0061] The assumptions for the calculations here are as follows: (1) Material to be processed: Waste plastic Po • Items to be processed: Waste plastics discharged by local governments in accordance with the Container and Packaging Recycling Law. • Waste plastic processing capacity: 6 t / h • Chlorine-based polymer content in waste plastic: 5% by mass • Average chlorine concentration of the chlorine-based polymer: 40% by mass • Chlorine concentration in waste plastic: 2% by mass • PET content in waste plastics: 15% by mass • Average PET concentration of the PET-containing plastic: 100% by mass (PET alone) • PET concentration in waste plastic: 15% by mass (2) Optical sorting device: PET-compatible optical sorting device 10p • Percentage of unsorted plastics per optical sorting pass: 10% • Misselection rate (over-sorting rate) of non-sorted plastics per optical sorting pass: 8%

[0062] Table 3 summarizes the estimated results for the hourly flow rate (processing rate), component concentration, etc., and data such as the supply process of the sorted intermediate materials, for both the waste plastic Po before sorting and the PET concentrated intermediate material Pp and PET removal intermediate material Pq after sorting. Note that in Table 3, for example, in the calculation of the amount of unsorted PET and the amount of oversorted waste plastics other than PET in the PET optical sorting device 10p, the detailed intermediate calculation results necessary because each target plastic is different are omitted, and only the final results are shown.

[0063] Table 3 shows that in this embodiment, the total volume of the PET removal intermediate material Pq is 4.78 t / h, with a chlorine concentration of 2.3 mass% and a PET concentration of 2 mass%. Even when this PET removal intermediate material Pq is reduced in volume to the volume-reduced intermediate material Pv in the first volume-reducing extruder 12, the PET concentration remains at 2 mass%, which is less than 3 mass%, eliminating concerns about a decrease in the dechlorination rate in the dechlorination extruder 14. Therefore, the dechlorination treatment temperature can be set to 350°C or lower. Furthermore, the chlorine concentration of 2.3 mass% here is considered acceptable because the dechlorination extruder 14 has the dechlorination capacity to remove 95% of the chlorine content of the incoming waste plastic, and the chlorine concentration of the volume-reduced and dechlorinated waste plastic Px can be reduced to 0.1 mass%.

[0064] Table 3 also shows that in this embodiment, the total volume of the PET concentrated intermediate material Pp is 1.22 t / h, with a chlorine concentration of 0.8 mass% and a PET concentration of 67 mass%. Even when this PET concentrated intermediate material Pp is reduced in volume by the second volume reduction extrusion device 20 to become volume-reduced waste plastic Py, the chlorine concentration remains sufficiently low, and it can be used as a raw material for coke ovens as a chemical recycling destination or as solid fuel as a thermal recycling destination. On the other hand, the high PET concentration of 67% by mass in the volume-reduced waste plastic Py is not a problem at all, as it is used at temperatures where PET is completely thermally decomposed in all applications.

[0065] The effects of this embodiment on conventional technologies, such as energy intensity and total dechlorination rate, will be examined later, including in comparison with other embodiments.

[0066] [Table 3]

[0067] (Second embodiment) Figure 3 shows the equipment arrangement and processing flow of a waste plastic volume reduction and dechlorination apparatus according to a second embodiment, which, in addition to the configuration of the first embodiment, further includes a first optical sorting apparatus 10c1 for chlorine-based materials in the pre-processing step before the PET-target optical sorting apparatus 10p. Referring to Figure 3, the waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method according to the second embodiment will be described.

[0068] As shown in Figure 3, the waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method according to the second embodiment differ from the waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method according to the first embodiment in the following respects. In other words, the second embodiment differs significantly in that the waste plastic Po is first processed in the first optical sorting device 10c1 for chlorine-based materials, and the chlorine-based polymer-concentrated intermediate material Pc is supplied to the optical sorting device 10p for PET materials. Consequently, the intermediate material of waste plastic supplied to the second volume reduction extruder 20 differs in that it consists of two types: a chlorine-based removal intermediate material Pd and a chlorine-based concentrated PET-concentrated intermediate material Pcp, instead of one type of PET-concentrated intermediate material Pp. Furthermore, the intermediate material of waste plastic supplied to the first volume reduction extruder 12 differs in that it consists of a chlorine-based concentrated PET-removing intermediate material Pcq, which is further reduced from the PET-removing intermediate material Pq. The other configurations are substantially the same as in the first embodiment.

[0069] (Estimate of material balance in optical sorting in the second embodiment) In this embodiment, we will explain the results of a material balance calculation when sorting waste plastic (Po) using two optical sorting devices. Note that this embodiment is not limited to the calculation results described below.

[0070] The assumptions for the materials to be processed in this calculation are the same as in the first embodiment. Furthermore, the optical sorting device is used in the same way, but the setting for the target plastic is either chlorine-based polymer or PET. Therefore, the unsorted rate and missorted rate are also the same as in the first embodiment.

[0071] Table 4, like Table 3, summarizes the estimated results for each optical sorting device, including the hourly flow rate (processing volume), component concentration, etc., of the waste plastic to be sorted and the waste plastic after sorting, as well as data such as the destination processes for the sorted intermediate materials. Note that, as with Table 3, only the final results are shown in Table 4, omitting the intermediate calculations.

[0072] Table 4 shows that in this embodiment, the total amount of the chlorine-based concentrated PET removal intermediate material Pcq is 0.61 t / h, with a chlorine concentration of 16.3 mass% and a PET concentration of 1 mass%. Thus, in this second embodiment as well, the PET concentration is 1 mass%, which is less than 3 mass%, eliminating concerns about a decrease in the dechlorination rate in the dechlorination extruder 14, so the dechlorination treatment temperature can be set to 350°C or lower. Furthermore, the chlorine concentration of 16.3 mass% here is considered acceptable because the dechlorination extruder 14 has the dechlorination capacity to remove 95% of the chlorine content of the incoming waste plastic, and the chlorine concentration of the volume-reduced dechlorinated waste plastic Px can be reduced to 0.8 mass%.

[0073] Table 4 also shows that the total amount of chlorine-based removal intermediate material Pd and chlorine-based concentrated PET intermediate material Pcp supplied to the second volume reduction extruder 20 is 5.39 t / h, with a chlorine concentration of 0.4 mass% and a PET concentration of 17 mass%. Even when this PET concentrated intermediate material Pp is reduced in volume by the second volume reduction extruder 20 to become volume-reduced waste plastic Py, the chlorine concentration is sufficiently low and it can be used as a raw material for coke ovens as a chemical recycling destination or as solid fuel as a thermal recycling destination. The fact that the PET concentration of the volume-reduced waste plastic Py is high at 67 mass% is not a problem at all because it is used at temperatures where PET is completely thermally decomposed in all applications.

[0074] The effects of this embodiment on conventional technologies, such as energy intensity and total dechlorination rate, will be examined later, including in comparison with other embodiments.

[0075] [Table 4]

[0076] (Third embodiment) Figure 4 shows the equipment arrangement of the waste plastic volume reduction and dechlorination apparatus and the processing flow of the waste plastic volume reduction and dechlorination method according to the third embodiment. Specifically, in this third embodiment, while assuming the configuration of the second embodiment, the supply destination of the chlorine-based concentrated PET intermediate material Pcp sorted by the PET target optical sorting apparatus 10p is changed from the second volume reduction extruder 20 to the chlorine-based first optical sorting apparatus 10c1. This embodiment will be described below.

[0077] As shown in Figure 4, the waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method according to the third embodiment differ from the waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method according to the second embodiment in the following respects. In other words, the third embodiment differs significantly in that the chlorine-based concentrated PET intermediate material Pcp, which has been separated by the chlorine-based first optical sorting device 10c1 and the PET-based optical sorting device 10p, is returned to the chlorine-based first optical sorting device 10c1 for recycling. Consequently, the intermediate material of waste plastic supplied to the second volume reduction extruder 20 differs in that it changes from two types, chlorine-based removal intermediate material Pd and chlorine-based concentrated PET intermediate material Pcp, to one type, chlorine-based removal intermediate material Pd. The other configurations are almost the same as in the second embodiment.

[0078] (Estimate of material balance in optical sorting in the third embodiment) In this embodiment, we will explain the results of a material balance calculation when waste plastic Po is sorted using two optical sorting devices while a portion of the waste plastic intermediate material (chlorine-based concentrated PET concentrated intermediate material Pcp) is recycled. The assumptions for the materials to be processed and the optical sorting devices in this calculation are the same as in the second embodiment. Furthermore, this embodiment is not limited to the calculation results described below.

[0079] Table 5, like Table 4, summarizes the estimated results for each optical sorting device, including the hourly flow rate (processing volume), component concentration, etc., of waste plastic before sorting and waste plastic after sorting, as well as data such as the destination processes for sorting intermediate materials. Note that, as with Table 4, only the final results are shown in Table 5, omitting the intermediate calculations. In this embodiment, since the chlorine-based concentrated PET intermediate material Pcp is returned to the chlorine-based first optical sorting device 10c1 for circulation, there was concern as to whether the amount and composition of waste plastic supplied to the chlorine-based first optical sorting device 10c1 could be quantitatively evaluated. Upon detailed examination of this point, it was confirmed that although the amount and composition of waste plastic at the input side of the chlorine-based first optical sorting device 10c1 change according to the number of circulations in the initial stages of operation, they converge to a constant amount after only a few circulations. Based on this, Table 5 shows only the converged values ​​for the amount and composition of waste plastic at the input side of the chlorine-based first optical sorting device 10c1.

[0080] Table 5 shows that in this embodiment, the total amount of the chlorine-based concentrated PET removal intermediate material Pcq is 0.63 t / h, with a chlorine concentration of 17 mass% and a PET concentration of 1 mass%. Thus, in this third embodiment as well, the PET concentration is 1 mass%, which is less than 3 mass%, eliminating concerns about a decrease in the dechlorination rate in the dechlorination extruder 14, and therefore the dechlorination treatment temperature can be set to 350°C or lower. Furthermore, the chlorine concentration of 17 mass% here is considered acceptable because the dechlorination extruder 14 has the dechlorination capacity to remove 95% of the chlorine content of the incoming waste plastic, and the chlorine concentration of the volume-reduced dechlorinated waste plastic Px can be reduced to 0.9 mass%. Table 5 also shows that the total amount of chlorine-based removal intermediate material Pd supplied to the second volume reduction extruder 20 is 5.37 t / h, with a chlorine concentration of 0.2 mass% and a PET concentration of 17 mass%. Even after this chlorine-based removal intermediate material Pd is reduced in volume by the second volume reduction extruder 20 to become volume-reduced waste plastic Py, the chlorine concentration is sufficiently low, and it can be used as a raw material for coke ovens as a chemical recycling destination or as solid fuel as a thermal recycling destination. The fact that the PET concentration of the volume-reduced waste plastic Py is 17 mass% is not a problem at all, as it is used at temperatures where PET is completely thermally decomposed in all of these applications.

[0081] The effects of this embodiment on conventional technologies, such as energy intensity and total dechlorination rate, will be examined later, including in comparison with other embodiments.

[0082] [Table 5]

[0083] (Fourth embodiment) Figure 5 shows the equipment arrangement and processing flow of a waste plastic volume reduction and dechlorination apparatus according to the fourth embodiment, which, in addition to the configuration of the second embodiment, further includes a second optical sorting device 10c2 for chlorine-based targets within the transport path of the chlorine-based intermediate material Pd. Referring to Figure 5, the waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method according to the fourth embodiment will be described.

[0084] As shown in Figure 5, the waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method according to the fourth embodiment differ from the waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method according to the second embodiment in the following respects. In other words, the fourth embodiment differs significantly in that a sorting device 10c2 is added, and the intermediate material Pd is sorted into intermediate material Pdc and intermediate material Pdd. Consequently, the intermediate material of the waste plastic supplied to the second volume reduction extruder 20 differs in that the combination of intermediate material Pd and intermediate material Pcp is replaced with a combination of intermediate material Pdd and intermediate material Pcp. Furthermore, the intermediate material of the waste plastic supplied to the first volume reduction extruder 12 differs in that there are two types of intermediate material, intermediate material Pcq and intermediate material Pdc, instead of one type of intermediate material Pcq. The other configurations are almost the same as in the second embodiment.

[0085] (Estimate of material balance in optical sorting in the fourth embodiment) In this embodiment, we will explain the results of our calculation of the material balance when sorting waste plastic (Po) using three optical sorting devices. The assumptions regarding the material to be processed and the optical sorting devices used in this calculation are the same as in the second embodiment. Furthermore, this embodiment is not limited to the calculation results described below.

[0086] Table 6, like Table 4, summarizes the estimated results for each optical sorting device, including the hourly flow rate (processing rate), component concentration, etc., of the waste plastic to be sorted and the waste plastic after sorting, as well as data such as the destination processes for the sorted intermediate materials. Note that, as with Table 4, only the final results are shown in Table 6, omitting the intermediate calculations.

[0087] Table 6 shows that in this embodiment, the total amount of waste plastic intermediate material (Pdc + Pcq) supplied to the first volume reduction extruder 12 is 1.06 t / h, with a chlorine concentration of 10.4 mass% and a PET concentration of 7 mass%. Thus, in the fourth embodiment, since the PET concentration is 7 mass%, which is above 3 mass%, the level at which there is no concern about a decrease in the dechlorination rate in the dechlorination extruder 14, the dechlorination treatment temperature needs to be set relatively high, at 400°C or lower. Furthermore, the chlorine concentration of 10.4 mass% here is considered acceptable because the dechlorination extruder 14 has the dechlorination capacity to remove 95% of the chlorine content of the incoming waste plastic, and the chlorine concentration of the volume reduction dechlorination waste plastic Px can be reduced to 0.5 mass%.

[0088] Table 6 also shows that the total volume of the waste plastic intermediate material (Pdd+Pcp) supplied to the second volume reduction extruder 20 is 4.94 t / h, with a chlorine concentration of 0.2 mass% and a PET concentration of 17 mass%. Even when this PET-concentrated intermediate material Pp is reduced in volume by the second volume reduction extruder 20 to become volume-reduced waste plastic Py, the chlorine concentration remains sufficiently low, and it can be used as a raw material for coke ovens as a chemical recycling destination or as solid fuel as a thermal recycling destination. The fact that the PET concentration of the volume-reduced waste plastic Py is 17 mass% is not a problem at all, as it is used at temperatures where PET is completely thermally decomposed in all of these applications.

[0089] The effects of this embodiment on conventional technologies, such as energy intensity and total dechlorination rate, will be examined later, including in comparison with other embodiments.

[0090] [Table 6]

[0091] (Fifth embodiment) Figure 6 shows the equipment layout of the waste plastic volume reduction and dechlorination apparatus and the processing flow of the waste plastic volume reduction and dechlorination method according to the fifth embodiment. Specifically, in this fifth embodiment, while assuming the configuration of the fourth embodiment, the supply destination of the intermediate material Pcp and intermediate material Pdc is changed from the output side of the sorting device 10p and sorting device 10c2 in the fourth embodiment to the input side. This embodiment will be described below.

[0092] As shown in Figure 6, the waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method according to the fifth embodiment differ from the waste plastic volume reduction and dechlorination apparatus and waste plastic volume reduction and dechlorination method according to the fourth embodiment in the following respects. In other words, the fifth embodiment differs significantly in that the intermediate material of the waste plastic is circulated between the two sorting devices, with the intermediate material Pdc from the sorting device 10c2 being supplied to the sorting device 10p, and the intermediate material Pcp from the sorting device 10p being supplied to the sorting device 10c2. Consequently, the intermediate material of the waste plastic supplied to the first volume reduction extruder 12 differs in that it is reduced from two types, intermediate material Pcq and intermediate material Pdc, to just one type, intermediate material Pcq. Furthermore, the intermediate material of the waste plastic supplied to the second volume reduction extruder 20 also differs in that it is reduced from two types, intermediate material Pcp and intermediate material Pdd, to just one type, intermediate material Pdd. The other configurations are almost the same as those of the fourth embodiment.

[0093] (Estimate of material balance in optical sorting in the fifth embodiment) In this embodiment, we will describe the results of a material balance calculation when waste plastic Po is separated into two types of intermediate materials Pc and Pd by a sorting device 10c1, and then some of the intermediate materials (Pcp and Pdc) are circulated between two sorting devices (10c2 and 10p). The assumptions for the material to be processed and the optical sorting device in this calculation are the same as in the fourth embodiment. Furthermore, this embodiment is not limited to the calculation results described below.

[0094] Table 7, like Table 6, summarizes the estimated results for each optical sorting device, including the hourly flow rate (processing volume), component concentration, etc., of the waste plastic to be sorted and the waste plastic after sorting, as well as data such as the supply process for the sorting intermediate material. Note that, as with Table 6, only the final results are shown in Table 7, omitting the intermediate calculations. In this embodiment as well, since some of the intermediate materials (Pcp and Pdc) are circulated between two sorting devices (10c2 and 10p), there was concern as to whether it would be possible to quantitatively evaluate the flow rate and composition of the intermediate materials at the input and output sides of each sorting device (10c2 and 10p). However, upon detailed examination in this embodiment as well, it was confirmed that although the flow rate and composition of the intermediate materials at the input and output sides of each sorting device (10c2 and 10p) change according to the number of cycles in the initial stages of operation, they converge to a constant amount after only a few cycles. Based on this, it was decided to use the converged values ​​for the flow rate and composition of waste plastic at the input side of each sorting device (10c2 and 10p) in Table 7.

[0095] Table 7 shows that in this embodiment, the total amount of waste plastic intermediate material Pcq supplied to the first volume reduction extruder 12 is 0.99 t / h, with a chlorine concentration of 12 mass% and a PET concentration of 2 mass%. Thus, in the fifth embodiment as well, the PET concentration is 2 mass%, which is less than 3 mass%, eliminating concerns about a decrease in the dechlorination rate in the dechlorination extruder 14, so the dechlorination treatment temperature can be set to 350°C or lower. Furthermore, the chlorine concentration of 12 mass% here is considered acceptable because the dechlorination extruder 14 has the dechlorination capacity to remove 95% of the chlorine content of the incoming waste plastic, and the chlorine concentration of the volume reduction dechlorination waste plastic Px can be reduced to 0.6 mass%.

[0096] Table 7 also shows that the total amount of waste plastic intermediate material Pdd supplied to the second volume reduction extruder 20 is 5.01 t / h, with a chlorine concentration of 0 mass% and a PET concentration of 18 mass%. Even after this intermediate material Pdd is reduced in volume by the second volume reduction extruder 20 to become volume-reduced waste plastic Py, the chlorine concentration remains almost 0 mass%, and it can be used as a raw material for coke ovens as a chemical recycling destination or as solid fuel as a thermal recycling destination. The fact that the PET concentration of the volume-reduced waste plastic Py is 18 mass% is not a problem at all, as it is used at temperatures where PET is completely thermally decomposed in all of these applications.

[0097] The effects of this embodiment on conventional technologies, such as energy intensity and total dechlorination rate, will be examined later, including in comparison with other embodiments.

[0098] [Table 7]

[0099] (Estimation of energy intensity and total dechlorination rate according to the present invention) The following describes the results of calculations performed to confirm the effects of each embodiment of the present invention. However, the present invention is not limited to the calculation results described below.

[0100] The assumptions for the calculations here are as follows: (1) Material to be processed: Waste plastic Po • Items to be processed: Waste plastics discharged by local governments in accordance with the Container and Packaging Recycling Law. • Waste plastic processing capacity: 6 t / h • Chlorine-based polymer content in waste plastic: 5% by mass • Average chlorine concentration of the chlorine-based polymer: 40% by mass • Chlorine concentration in waste plastic: 2% by mass • PET content in waste plastics: 15% by mass • Average PET concentration of the PET-containing plastic: 100% by mass (PET alone) • PET concentration in waste plastic: 15% by mass • Initial temperature of waste plastic: 15℃

[0101] (2) Optical sorting process: Sorting devices 10c1, 10c2, 10p • Percentage of unsorted plastics per optical sorting pass: 10% • Misselection rate (over-sorting rate) of non-sorted plastics per optical sorting pass: 8% (3) Volume reduction process: First volume reduction extruder 12, second volume reduction extruder 20 • Maximum processing temperature: 180℃ • Total chlorine removal rate for all plastics: 0% • Melting rate of all plastics: 10% (4) Dechlorination process: Dechlorination extruder 14 • Maximum processing temperature in the dechlorination process: 400℃ • Total chlorine removal rate for all plastics: 95% • Melting rate of all plastics: 100%

[0102] (5) Energy parameters: • Items included in the calculation: Latent heat of vaporization of adhering moisture, sensible heat of heating of waste plastics, Latent heat of fusion of waste plastics, heat of dechlorination reaction of chlorine-based polymers • Moisture content of waste plastic: 10% by mass (external application) • Latent heat of vaporization of adhering water: 2300 kJ / kg • Average specific heat of all plastics in sensible heat calculations for heating: 2.1 kJ / kg·℃ • Average latent heat of all plastics calculated based on the latent heat of fusion: 83.5 kJ / kg • Latent heat of chlorine decomposition of chlorine-based polymers: 714 kJ / kg

[0103] Table 8 shows the results of calculating the energy intensity and total dechlorination rate for each comparative example and each embodiment of the present invention, while referring to the calculation results of the material balance of waste plastics before and after sorting by each sorting device in each embodiment shown in Tables 3 to 7, under the above preconditions.

[0104] [Table 8]

[0105] Comparative Example 1, shown in Table 8, is the result of calculations when the dechlorination extrusion process is not adopted, and Comparative Example 2 is the result of calculations when the optical sorting process is not adopted. Comparing Comparative Example 1 and Comparative Example 2, it can be seen that the energy intensity per unit is almost doubled by the dechlorination treatment, from 585 MJ / t-plastic to 1156 MJ / t-plastic.

[0106] In contrast, as in the first embodiment, by reducing the PET concentration of waste plastic to 2% by mass in the sorting device 10p and lowering the processing temperature to 350°C, it is possible to obtain 958 MJ / t-plastic, which is 17% lower in energy intensity than in Comparative Example 2. However, in this case, the total dechlorination rate decreases by 8% compared to Comparative Example 2, becoming 87%.

[0107] Furthermore, as in the second embodiment, by using sorting devices 10c1 and 10p to narrow down the waste plastic to be dechlorinated to 0.61 t / h, it can be seen that the energy intensity can be reduced by 44% compared to Comparative Example 2 to 652 MJ / t-plastic. However, in this case, the total dechlorination rate decreases by 16% compared to Comparative Example 2 to 79%.

[0108] In contrast, in the third embodiment, by returning the intermediate material Pcp to the sorting device 10c1 and circulating it, some of the chlorine-based polymers that were over-sorted in the intermediate material Pcp can be returned to the dechlorination treatment, thereby recovering the total dechlorination rate from 79% in the second embodiment to 85%. Furthermore, the second and third embodiments achieve the highest energy intensity levels among the five embodiments of the present invention, at 652 MJ / t-plastic and 657 MJ / t-plastic, respectively.

[0109] On the other hand, in the fourth embodiment, compared to the low total dechlorination rate of 79% in the second embodiment, the chlorine-based polymer remaining in the intermediate material Pd due to sorting failure in the sorting device 10c1 is returned to the dechlorination treatment in an additional sorting device 10c2, making it possible to recover the total dechlorination rate to 87%. However, in this case, the PET concentration rises to 7% by mass, and therefore the dechlorination treatment temperature needs to be raised to 400°C, so the energy intensity increases slightly to 708 MJ / t-plastic.

[0110] In contrast, in the fifth embodiment, the intermediate materials Pcp and Pdc are circulated between the sorting devices 10c2 and 10p, thereby lowering the PET concentration compared to the fourth embodiment and enabling a dechlorination treatment temperature of 350°C, improving the energy intensity to 689 MJ / t-plastic. Moreover, in the fifth embodiment, compared to the fourth embodiment, the total dechlorination rate can be increased from 87% to 93%, approaching the 95% of Comparative Example 2.

[0111] As described above, the calculation results shown in Table 8 show that, in each embodiment of the present invention, the energy intensity can be significantly improved while maintaining a high total dechlorination rate compared to Comparative Example 2. [Explanation of Symbols]

[0112] 1, 2, 3, 4, 5 Volume reduction and chlorine removal equipment for waste plastics 10 Optical sorting device 10c1 Chlorine-based first optical sorting device 10c2 Chlorine-based second optical sorting device 10p PET optical sorting device 12. First volume reduction extruder 14. Dechlorination extruder 20 Second volume reduction extrusion apparatus 30 Coke ovens 32 Carbonization Chamber 34 Coke 38 Furnace top space 40 Ascending tube 42 Bent pipes 44. Aquatic water flushing equipment 46 Dry Main 50. A device for converting waste plastics into solid fuel. 51 Weighing machine 52 Volume reduction extrusion apparatus 53 Heater (heating device) 54. Dechlorination extruder 55 Heater (heating device) 56. Hydrogen chloride treatment device (hydrogen chloride recovery device) 57 Granulation / cooling / dehydration equipment 58 Conveyor 59 Container 70 Optical sorting device 71 Control Unit 72 Conveyor 72a Laura 73 Near-infrared sensor 74 Gas supply unit 75 Gas injection unit 76a, 76b Separation and collection trays A. Gas (air, etc.) L Near-infrared Po waste plastic Pc Chlorine-based concentrated intermediate material PCP Chlorine-based concentrated PET intermediate material PCQ Chlorine-based concentrated PET removal intermediate material Pd Chlorine-based removal intermediate material Pdc Chlorine-based removal residual concentration intermediate material Pdd Chlorine-based removal repeatable intermediate material Pp PET concentrated intermediate material Pq PET removal intermediate material Pv volume reduction intermediate material Px Volume-reduced and chlorinated waste plastics Py volume reduction waste plastic Sa, Sb waste plastic

Claims

1. A waste plastic volume reduction and dechlorination apparatus that reduces the volume of waste plastic Po, which is made up of multiple types of materials including chlorine-based polymers and polyethylene terephthalate (PET), while dechlorinating it to obtain a mass of waste plastic that is substantially free of chlorine-based polymers, (a) A PET target optical sorting device that sorts the waste plastic Po supplied in a crushed state of a predetermined size into a PET concentrated intermediate material Pp, which is obtained by selectively concentrating PET based on the difference in wavelength absorption depending on the material, and a PET removed intermediate material Pq, which is obtained by selectively removing PET. (b) A first volume reduction extrusion apparatus that reduces the volume of the PET removal intermediate material Pq by raising the resin temperature to 120°C or higher and 200°C or lower, thereby removing moisture as water vapor and obtaining a volume reduction intermediate material Pv, (c) A dechlorination extruder that raises the temperature of the volume-reducing intermediate material Pv to 250°C or higher and 400°C or lower, separates chlorine mainly as hydrogen chloride gas and exhausts it, and discharges volume-reducing, dechlorinated waste plastic Px that is substantially free of chlorine-based polymers, (d) The PET concentrated intermediate material Pp is used when the resin temperature is between 120°C and 200°C. A waste plastic volume reduction and dechlorination apparatus comprising: a second volume reduction extrusion apparatus which reduces the volume of waste plastic Py by raising the temperature to remove moisture as steam; and a second volume reduction extrusion apparatus which reduces the volume of waste plastic Py.

2. (e) The PET optical sorting apparatus is further equipped with a first chlorine-based optical sorting apparatus that sorts the waste plastic Po into a chlorine-based concentrated intermediate material Pc, which is obtained by selectively concentrating chlorine-based polymers based on the difference in wavelength absorption depending on the material, and a chlorine-based removal intermediate material Pd, which is obtained by selectively removing chlorine-based polymers. (a1) The PET optical sorting apparatus receives the chlorine-based concentrated intermediate material Pc instead of the waste plastic Po, and sorts the chlorine-based concentrated intermediate material Pc into a chlorine-based concentrated PET intermediate material Pcp, which is obtained by selectively concentrating PET based on the difference in wavelength absorption depending on the material, and a chlorine-based concentrated PET removal intermediate material Pcq, which is obtained by selectively removing PET. (b1) The first volume reduction extrusion apparatus receives the chlorine-based concentrated PET removal intermediate material Pcq instead of the PET removal intermediate material Pq, (d1) The waste plastic volume reduction and dechlorination apparatus according to claim 1, wherein the second volume reduction extrusion apparatus receives the chlorine-based removal intermediate material Pd and the chlorine-based concentrated PET concentrated intermediate material Pcp instead of the PET concentrated intermediate material Pp.

3. (a2) The waste plastic volume reduction and dechlorination apparatus according to claim 2, wherein the supply destination of the chlorine-based concentrated PET intermediate material Pcp sorted by the PET target optical sorting apparatus is changed from the second volume reduction extrusion apparatus to the first chlorine-based target optical sorting apparatus.

4. (f) The transport path of the chlorine-removing intermediate material Pd sorted by the first optical sorting device for chlorine-removing materials is further provided with a second optical sorting device for chlorine-removing materials that sorts the chlorine-removing intermediate material Pd into a chlorine-removing residual concentrated intermediate material Pdc, which has been selectively concentrated with chlorine-removing polymers based on differences in wavelength absorption depending on the material, and a chlorine-removing repeated intermediate material Pdd, which has been selectively removed with chlorine-removing polymers. (b2) The first volume reduction extrusion apparatus receives the chlorine-based concentrated PET removal intermediate material Pdc in addition to the chlorine-based remaining concentrated intermediate material Pcq, (d2) The waste plastic volume reduction and dechlorination apparatus according to claim 2, wherein the second volume reduction extrusion apparatus receives the chlorine-based concentrated PET concentrated intermediate material Pcp in addition to the chlorine-based repeated removal intermediate material Pdd.

5. (a3) The supply destination of the chlorine-based concentrated PET intermediate material Pcp obtained by selectively concentrating PET in the PET target optical sorting device is changed from the second volume reduction extruder to the chlorine-based second optical sorting device, (f1) The waste plastic volume reduction and dechlorination apparatus according to claim 4, wherein the supply destination of the chlorine-based polymer-removed residual concentrated intermediate material Pdc, obtained by selectively concentrating chlorine-based polymers in the second optical sorting apparatus for chlorine-based materials, is changed from the first volume reduction extruder to an optical sorting apparatus for PET materials.

6. A method for reducing the volume and dechlorinating waste plastics, comprising dechlorinating waste plastics Po, which consists of multiple types of materials including chlorine-based polymers and polyethylene terephthalate (PET), while reducing its volume, to obtain aggregates of waste plastics that are substantially free of chlorine-based polymers, (a) A PET target optical sorting step in which the waste plastic Po supplied in a crushed state of a predetermined size is sorted using an optical sorting device into a PET concentrated intermediate material Pp, which is obtained by selectively concentrating PET based on the difference in wavelength absorption depending on the material, and a PET removed intermediate material Pq, which is obtained by selectively removing PET. (b) A first volume reduction extrusion step in which the PET removal intermediate material Pq is heated using an extruder to a resin temperature of 120°C or higher and 200°C or lower, thereby reducing its volume while removing moisture as water vapor, and obtaining a volume reduction intermediate material Pv. (c) A dechlorination extrusion process in which, using an extruder, the chlorine is separated from the volume-reduced intermediate material Pv while the resin temperature is raised to 250°C or higher and 400°C or lower, and the gas is exhausted, and a volume-reduced, dechlorinated waste plastic Px that is substantially free of chlorine-based polymers is discharged. (d) A method for reducing the volume of waste plastics by dechlorinating, comprising: a second volume reduction extrusion step, in which the PET concentrated intermediate material Pp is heated using an extruder to a resin temperature of 120°C or higher and 200°C or lower, thereby reducing its volume while removing moisture as water vapor to obtain a volume-reduced waste plastic Py.

7. (e) The process further includes a first optical sorting step for chlorine-based materials, preceding the optical sorting step for PET materials, in which the waste plastic Po is sorted into a chlorine-based concentrated intermediate material Pc, which is obtained by selectively concentrating chlorine-based polymers based on differences in wavelength absorption depending on the material, and a chlorine-based removal intermediate material Pd, which is obtained by selectively removing chlorine-based polymers. (a1) In the PET target optical sorting process, the chlorine-based concentrated intermediate material Pc is supplied instead of the waste plastic Po, and the chlorine-based concentrated intermediate material Pc is sorted into a chlorine-based concentrated PET intermediate material Pcp, which is obtained by selectively concentrating PET based on the difference in wavelength absorption depending on the material, and a chlorine-based concentrated PET removal intermediate material Pcq, which is obtained by selectively removing PET. (b1) In the first volume reduction extrusion step, the chlorine-based concentrated PET removal intermediate material Pcq is supplied instead of the PET removal intermediate material Pq, (d1) The method for reducing the volume of waste plastics by dechlorinating them according to claim 6, wherein in the second volume reduction extrusion step, the chlorine-based removal intermediate material Pd and the chlorine-based concentrated PET concentrated intermediate material Pcp are supplied instead of the PET concentrated intermediate material Pp.

8. (a2) The method for reducing the volume of waste plastics by dechlorinating them according to claim 7, wherein the supply destination of the chlorine-based concentrated PET intermediate material Pcp sorted in the PET target optical sorting step is changed from the second volume reduction extrusion step to the first chlorine-based target optical sorting step.

9. (f) The transport path of the chlorine-removing intermediate material Pd selected in the first optical sorting step for chlorine-removing materials further comprises a second optical sorting step for chlorine-removing materials, which sorts the chlorine-removing intermediate material Pd into a chlorine-removing residual concentrated intermediate material Pdc, which has been selectively concentrated with chlorine-removing polymers based on differences in wavelength absorption depending on the material, and a chlorine-removing repeated intermediate material Pdd, which has been selectively removed with chlorine-removing polymers. (b2) The first volume reduction extrusion step receives the chlorine-based concentrated PET removal intermediate material Pcq in addition to the chlorine-based remaining concentrated intermediate material Pdc, (d2) The method for reducing the volume of waste plastics by dechlorinating them according to claim 7, wherein the second volume reduction extrusion step is to receive the chlorine-based concentrated PET concentrated intermediate material Pcp in addition to the chlorine-based repeated removal intermediate material Pdd.

10. (a3) The supply destination of the chlorine-based concentrated PET intermediate material Pcp obtained by selectively concentrating PET in the PET target optical sorting process is changed from the second volume reduction extrusion process to the chlorine-based second optical sorting process, (f1) The method for reducing the volume of waste plastics by dechlorinating them according to claim 9, wherein the supply destination of the chlorine-based residual concentrated intermediate material Pdc obtained by selectively concentrating chlorine-based polymers in the second optical sorting step for chlorine-based materials is the PET-target optical sorting step instead of the first volume reduction extrusion step.

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