Raw material supply system

Abstract

To provide a raw material supply system capable of improving efficiency of chemical recycling and preventing fouling and corrosion of equipment by appropriately treating PVC and PET contained in waste plastic before sending the waste plastic to a pyrolysis furnace.SOLUTION: The raw material feed system comprises a slaked lime feeder 12 for charging slaked lime into waste plastics, a melting demineralizer 18 for demineralizing PVC and hydrolyzing PET by mixing waste plastics and slaked lime while heating them, a degassing hopper 20 connected to the melting demineralizer 18, a raw material feeder 22 for feeding molten waste plastics in the degassing hopper 20 to the pyrolysis furnace 6, and a level sensor 31 for detecting the liquid level of molten waste plastics accumulated in the degassing hopper 20.SELECTED DRAWING: Figure 1

Description

[TECHNICAL FIELD]

[0001] The present invention relates to a raw material supply system for pyrolyzing waste plastics containing polyvinyl chloride (PVC) and polyethylene terephthalate (PET), and particularly to a raw material supply system that supplies waste plastics to a pyrolysis furnace while treating PVC and PET contained in the waste plastics. [BACKGROUND ART]

[0002] Waste plastics contain PVC (polyvinyl chloride) and PET (polyethylene terephthalate) in addition to PS (polystyrene), PP (polypropylene), and PE (polyethylene). Development of material recycling and chemical recycling for treating and reusing such waste plastics containing various resin components is in progress. In particular, chemical recycling, which recovers oil and gas from waste plastics, has attracted growing attention.

[0003] However, for chemical recycling of waste plastics, treatment of PVC and PET is necessary for the following reasons. When polyvinyl chloride (PVC) is pyrolyzed, it generates HCl (hydrogen chloride), which corrodes downstream equipment, and also degrades the quality of product oil by causing chlorine-containing compounds to mix into the cracked oil recovered from waste plastics. When polyethylene terephthalate (PET) is pyrolyzed in a pyrolysis furnace, it generates benzoic acid and terephthalic acid. All of these acids have sublimability, and they deposit on the downstream side, causing fouling and corrosion of downstream equipment, as well as quality degradation caused by acid mixing (crystal precipitation) into the cracked oil. [PRIOR ART DOCUMENTS] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2001-107058 [Summary of the Invention] [Problems that the invention aims to solve]

[0005] Patent Document 1 describes supplying slaked lime and waste plastic to a rotary kiln and desalting the waste plastic while removing chlorine derived from PVC in the waste plastic. However, waste plastic often contains not only PVC but also PET, and when processing waste plastic, it is necessary to process both PVC and PET together. In particular, phthalate esters (the main component of PET) are added to PVC as plasticizers to give it flexibility, and processing that targets either PVC or PET will not achieve the intended chemical recycling.

[0006] Therefore, the present invention provides a raw material supply system that can improve the efficiency of chemical recycling and prevent equipment fouling and corrosion by properly treating the PVC and PET contained in waste plastics before sending them to a pyrolysis furnace. [Means for solving the problem]

[0007] In one embodiment, a raw material supply system for thermally decomposing waste plastics containing polyvinyl chloride and polyethylene terephthalate is provided, comprising: a slaked lime supply device for adding slaked lime to the waste plastics; a melting desalination device for desalinizing the polyvinyl chloride and hydrolyzing the polyethylene terephthalate by mixing the waste plastics and slaked lime while heating the waste plastics and slaked lime; a deaeration hopper connected to the melting desalination device for storing the waste plastics melted by the melting desalination device; a raw material supply machine for sending the molten waste plastics in the deaeration hopper to a thermal decomposition furnace; and a level sensor for detecting the liquid level of the molten waste plastics accumulated in the deaeration hopper.

[0008] In one embodiment, a raw material supply system for thermally decomposing waste plastics containing polyvinyl chloride and polyethylene terephthalate is provided, comprising: a slaked lime supply device for adding slaked lime to the waste plastics; an operation control unit that commands the slaked lime supply device to add 1 to 4 times the total number of moles of polyvinyl chloride and polyethylene terephthalate in the waste plastics to the waste plastics; a melting desalination device that desalinates the polyvinyl chloride and hydrolyzes the polyethylene terephthalate by mixing the waste plastics and slaked lime while heating the waste plastics and slaked lime; a deaeration hopper connected to the melting desalination device for storing the waste plastics melted by the melting desalination device; a raw material supply machine for sending the melted waste plastics in the deaeration hopper to a thermal decomposition furnace; and a level sensor for detecting the liquid level of the melted waste plastics accumulated in the deaeration hopper.

[0009] In one embodiment, a raw material supply system for thermally decomposing waste plastics containing polyvinyl chloride and polyethylene terephthalate is provided, comprising: a slaked lime supply device for adding slaked lime to the waste plastics; an operation control unit that issues a command to the slaked lime supply device to add 1 to 4 times the total number of moles of polyvinyl chloride and polyethylene terephthalate in the waste plastics to the waste plastics; a melting desalination device that desalinates the polyvinyl chloride and hydrolyzes the polyethylene terephthalate by mixing the waste plastics and slaked lime while heating the waste plastics and slaked lime; a deaeration hopper connected to the melting desalination device for storing the waste plastics melted by the melting desalination device; and a raw material supply machine for sending the molten waste plastics in the deaeration hopper to a thermal decomposition furnace.

[0010] In one embodiment, the raw material supply system further includes a weight measuring device for measuring the weight of the waste plastic before the slaked lime is added, and the operation control unit is configured to adjust the amount of slaked lime to be added to the waste plastic based on the measured weight of the waste plastic. In one embodiment, the raw material supply system further includes a cracked oil properties measuring instrument for measuring the properties of cracked oil recovered from pyrolysis gas discharged from the pyrolysis furnace, and the operation control unit is configured to adjust the amount of slaked lime to be added to the waste plastic based on the measured values ​​of the properties of the cracked oil. In one embodiment, the decomposed oil properties measuring instrument is at least one of the following: a chlorine concentration measuring instrument for measuring the chlorine concentration in the decomposed oil; an acid concentration measuring instrument for measuring the acid concentration in the decomposed oil; a pH measuring instrument for measuring the pH of the decomposed oil; and a pH measuring instrument for measuring the pH of water separated from the decomposed oil. In one embodiment, the raw material supply system further comprises a water scrubber that condenses gaseous hydrocarbons generated from the heated waste plastic to recover decomposed oil, and the water scrubber is connected to the degassing hopper. In one embodiment, the pyrolysis furnace is a fluidized bed furnace, the fluidized bed furnace has a pyrolysis furnace and a fluid regeneration furnace through which a fluidized medium circulates, and the raw material supply system further includes a fluidized medium transfer line that sends a portion of the fluidized medium from the fluid regeneration furnace to the melting desalination device, the portion of the fluidized medium constitutes a heat source for the melting desalination device.

[0011] In one embodiment, a raw material supply method is provided for thermally decomposing waste plastics containing polyvinyl chloride and polyethylene terephthalate, wherein the raw material supply method is provided, which involves adding 1 to 4 times the total number of moles of polyvinyl chloride and polyethylene terephthalate in the waste plastics to the waste plastics, mixing the waste plastics and slaked lime while heating the waste plastics and slaked lime, thereby desalting the polyvinyl chloride and hydrolyzing the polyethylene terephthalate, and sending the waste plastics, which have been melted by heating, to a thermal decomposition furnace.

[0012] In one embodiment, the raw material supply method further includes a step of measuring the weight of the waste plastic before the slaked lime is added, and the amount of slaked lime to be added to the waste plastic is adjusted based on the measured weight of the waste plastic. In one embodiment, the raw material supply method further includes a step of measuring the properties of the decomposition oil recovered from the pyrolysis gas discharged from the pyrolysis furnace, and the amount of slaked lime to be added to the waste plastic is adjusted based on the measured properties of the decomposition oil. In one embodiment, the properties of the decomposed oil are at least one of the following: the concentration of chlorine in the decomposed oil, the concentration of acid in the decomposed oil, the pH of the decomposed oil, and the pH of water separated from the decomposed oil. In one embodiment, the process further includes a step of recovering decomposed oil by condensing gaseous hydrocarbons generated from the heated waste plastic using a water scrubber. In one embodiment, the pyrolysis furnace is a fluidized bed furnace, and the fluidized bed furnace has a pyrolysis furnace and a fluid regeneration furnace through which a fluidized medium circulates, and a portion of the fluidized medium is sent from the fluid regeneration furnace to the melting desalination device, and a portion of the fluidized medium is used as a heat source for the melting desalination device. [Effects of the Invention]

[0013] According to the present invention, the following effects can be obtained. Before sending waste plastics to the pyrolysis furnace, slaked lime is added to the waste plastics, ensuring proper desalination of PVC and proper hydrolysis of PET. As a result, proper chemical recycling of waste plastics can be achieved in the subsequent pyrolysis furnace. Furthermore, equipment corrosion and fouling can be suppressed (improving reliability), and an improvement in the yield of decomposed oil (mainly benzene) can be expected.

[0014] The amount of slaked lime added to waste plastics is automatically adjusted based on the weight of the waste plastics to be treated or the properties of cracked oil recovered from pyrolysis gas generated by pyrolysis of the waste plastics in a pyrolysis furnace. The weight of PVC and PET relative to the weight of the waste plastics can be determined by investigating the composition of the waste plastics in advance. Furthermore, the properties (e.g., pH) of the cracked oil recovered from the pyrolysis gas can vary depending on the amount of slaked lime added. Therefore, an appropriate amount of slaked lime can be added to the waste plastics based on this information. Gaseous hydrocarbons generated from heated waste plastics are condensed by a water scrubber and recovered as cracked oil. Accordingly, the yield of cracked oil is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] [Figure 1] It is a schematic diagram showing one embodiment of a treatment system for treating waste plastics. [Figure 2] It is a schematic diagram showing another embodiment of the treatment system. [Figure 3] It is a schematic diagram showing still another embodiment of the treatment system. [Figure 4] It is a schematic diagram showing yet another embodiment of the treatment system. [Figure 5] It is a schematic diagram showing one embodiment of a fluidized bed treatment system for treating waste plastics. [Figure 6] It is a schematic diagram showing another embodiment of a fluidized bed treatment system for treating waste plastics. MODES FOR CARRYING OUT THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing one embodiment of a treatment system for treating waste plastics. The waste plastics to be treated include at least PVC (polyvinyl chloride) and PET (polyethylene terephthalate). The waste plastics may further include at least one of PS (polystyrene), PP (polypropylene), and PE (polyethylene).

[0017] As shown in FIG. 1, the treatment system includes a pyrolysis furnace 6 that pyrolyzes waste plastics to generate pyrolysis gas containing pyrolysis products such as hydrocarbons, and a raw material supply system 2 that supplies waste plastics to the pyrolysis furnace 6. The type of the pyrolysis furnace 6 is not particularly limited, and may be, for example, a fluidized bed pyrolysis furnace described later, or may be a kiln-type pyrolysis furnace.

[0018] The raw material supply system 2 has not only a function of supplying waste plastics to the pyrolysis furnace 6, but also a function of treating PVC and PET contained in the waste plastics before being supplied to the pyrolysis furnace 6. More specifically, the raw material supply system 2 includes: a slaked lime feeder 12 that charges slaked lime into the waste plastics; an operation control unit 15 that issues a command to the slaked lime feeder 12 to charge the waste plastics with slaked lime in an amount of 1 to 4 times the total number of moles of PVC (polyvinyl chloride) and PET (polyethylene terephthalate) contained in the waste plastics; a molten desalination apparatus 18 that mixes the waste plastics and slaked lime while heating them, thereby desalinating PVC and hydrolyzing PET; a degassing hopper 20 connected to the molten desalination apparatus 18 and storing the waste plastics molten by the molten desalination apparatus 18; and a raw material feeder 22 that feeds the molten waste plastics in the degassing hopper 20 to the pyrolysis furnace 6.

[0019] The raw material supply system 2 further includes a weighing instrument 25 that measures the weight of the waste plastic before slaked lime is added. After the weight of the raw material waste plastic is measured by the weighing instrument 25, it is fed into the raw material hopper 27 of the melting and desalination device 18. The weighing instrument 25 is, for example, a weighing conveyor that can transport the waste plastic while weighing it. The weighing instrument 25 is connected to the operation control unit 15, and the measured weight of the waste plastic is sent to the operation control unit 15. The operation control unit 15 is configured to adjust (or determine) the amount of slaked lime to be added to the waste plastic based on the measured weight of the waste plastic. The slaked lime supply device 12 is connected to the raw material hopper 27 of the melting and desalination device 18 and feeds the amount of slaked lime determined by the operation control unit 15 into the raw material hopper 27 of the melting and desalination device 18. Thus, the raw material waste plastic and slaked lime are fed into the raw material hopper 27 of the melting and desalination device 18. The location where slaked lime is added to the waste plastic is not limited to the raw material hopper 27; for example, slaked lime may be added to the waste plastic storage or transport section.

[0020] The operation control unit 15 includes a storage device 15a in which a program is stored, and an arithmetic unit 15b that performs calculations according to the instructions contained in the program. The storage device 15a includes a main memory such as random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or solid state drive (SSD). Examples of arithmetic units 15b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the operation control unit 15 is not limited to this embodiment.

[0021] The melting and desalination apparatus 18 includes a raw material hopper 27, a first raw material feeder 29 connected to the raw material hopper 27, and a heater 30 for heating the first raw material feeder 29. The waste plastic and slaked lime introduced into the raw material hopper 27 are heated by the heater 30, mixed by the first raw material feeder 29, and then sent to the deaerating hopper 20. In one embodiment, the heater 30 is configured to heat the waste plastic and slaked lime within a range of 250°C to 350°C. The structure and arrangement of the heater 30 are not particularly limited as long as they can heat the mixture of waste plastic and slaked lime within a range of 250°C to 350°C. Specific examples of the heater 30 include steam heaters, electric heaters, and heaters that use heated inert gas (e.g., nitrogen gas) as a heat source. The heating method may be direct heating, indirect heating, or a combination of both.

[0022] The melting desalination apparatus 18 desalinates the PVC contained in the waste plastic by heating a mixture of waste plastic and slaked lime with a heater 30. More specifically, the chlorine contained in the PVC is thermally separated as HCl (hydrogen chloride) by heating at 250°C to 350°C. The generated HCl is dry-treated with slaked lime, and the chlorine in the HCl is fixed to the slaked lime as a calcium salt (CaCl2). As a result, contact and reaction between the decomposition oil in the pyrolysis gas generated in the subsequent pyrolysis furnace 6 and chlorine can be avoided, and the generation of organochlorine compounds can be reduced.

[0023] Furthermore, the melting desalination apparatus 18 hydrolyzes the PET contained in the waste plastic by heating a mixture of waste plastic and slaked lime with a heater 30. More specifically, calcium terephthalate is produced by heating the PET together with slaked lime to 250°C to 350°C. Since this calcium terephthalate is thermally decomposed in the pyrolysis furnace 6, the production of sublimable benzoic acid and terephthalic acid is suppressed, and the yield of decomposed oil (especially benzene) is improved.

[0024] According to this embodiment, since slaked lime in an amount equal to 1 to 4 times the total number of moles of PVC (polyvinyl chloride) and PET (polyethylene terephthalate) in the waste plastic is supplied to the waste plastic, appropriate desalination of PVC and appropriate hydrolysis of PET are achieved simultaneously. As a result, appropriate chemical recycling of the waste plastic can be achieved in the subsequent pyrolysis furnace 6.

[0025] In this embodiment, the amount of slaked lime added to the waste plastic is automatically adjusted by the operation control unit 15 based on the weight of the waste plastic to be processed. The weight of PVC and PET in the waste plastic can be determined by examining the composition of the waste plastic in advance. Therefore, based on commands from the operation control unit 15, the slaked lime supply device 12 can add an amount of slaked lime to the waste plastic that is sufficient to properly process both PVC and PET in the waste plastic.

[0026] The weight of PVC and PET in waste plastic is, more specifically, the weight of chlorine and acid in the waste plastic. Therefore, the amount of slaked lime added to waste plastic is the amount necessary to treat the chlorine and acid contained in the waste plastic. Examples of the amount of slaked lime supplied to waste plastic are shown below.

[0027] (1) When the amount of PVC and PET mixed in the waste plastic is known If the weight measurement of waste plastic is W (kg / H), the proportion of PVC is x (wt%), and the proportion of PET is y (wt%), then the amount of slaked lime w (kg / H) per molar is given by the following formula. w=(W×x / 100×0.57×74 / 35.5 / 2)+(W×y / 100×0.33×74 / 16 / 4) (2) When the amount of PVC and PET mixed in the waste plastic is unknown. If the weight measurement of waste plastic is W (kg / H), the chlorine content based on elemental analysis is α (wt%), and the oxygen content is β (wt%), then the amount of slaked lime w (kg / H) per molar is given by the following formula. w=(W×α / 100×74 / 35.5 / 2)+(W×β / 100×74 / 16 / 4)

[0028] The molecular weight of each compound and the atomic weight of each element are as follows: PVC (backbone): (C2H3Cl)n, Molecular weight = 62.5, Chlorine content in PVC = 57 wt% PET (skeleton): (C 10 H8O4)n, Molecular weight = 192, Oxygen content in PET = 33 wt% Slaked lime: Ca(OH)2, molecular weight=74 Atomic weight of chlorine: 35.5 Atomic weight of oxygen: 16

[0029] For example, if 1 mole of PVC is converted to 1 mole of HCl by thermal decomposition, then 0.5 moles of slaked lime (Ca(OH)2) are needed for neutralization. Also, if 1 mole of PET is converted to 2 moles of -COOH by hydrolysis, then 1 mole of slaked lime (Ca(OH)2) is needed for neutralization.

[0030] The waste plastic is melted by heating it to 250°C to 350°C in the melting and desalination device 18. By melting the waste plastic, it is uniformly mixed with slaked lime, improving the efficiency of PVC dechlorination and PET hydrolysis.

[0031] The molten waste plastic is transferred to the deaerating hopper 20 by the first raw material feeder 29. The measurement value from the weight measuring instrument 25 is sent to the drive unit of the first raw material feeder 29, and the first raw material feeder 29 operates according to the measurement value from the weight measuring instrument 25. In the deaerating hopper 20, air present in the gaps of the waste plastic, gaseous HCl that was not fixed in the slaked lime as Ca salt, and gaseous hydrocarbons are separated from the molten waste plastic. By melting the waste plastic, the air in the waste plastic is separated, preventing the supply of air from the raw material supply system 2 to the pyrolysis furnace 6. As a result, combustion of the waste plastic in the pyrolysis furnace 6 is prevented, and the pyrolysis of the waste plastic can proceed. Combustion of waste plastic in the pyrolysis furnace 6 may also be prevented by introducing an inert gas such as nitrogen or steam into the deaerating hopper 20.

[0032] The raw material supply system 2 is equipped with a level sensor 31 that detects the liquid level of the waste plastic accumulated in the deaeration hopper 20. The measured liquid level of the waste plastic is sent to the drive unit of the first raw material feeder 29. The first raw material feeder 29 operates so that the liquid level of the waste plastic in the deaeration hopper 20 is within a predetermined range. Here, the predetermined range means a level that is above the level at which a seal is ensured between the pyrolysis furnace 6 and the deaeration hopper 20, taking into account pressure fluctuations in the pyrolysis furnace 6, and below the level at which there is no risk of exceeding the volume of the deaeration hopper 20.

[0033] The raw material feeder 22 includes a second raw material feeder 32 that sends the molten waste plastic in the degassing hopper 20 to the pyrolysis furnace 6. The second raw material feeder 32 is configured to continuously or intermittently feed the waste plastic to the pyrolysis furnace 6. The waste plastic processed by the raw material supply system 2 is pyrolyzed in the pyrolysis chamber 6 to generate pyrolysis gas.

[0034] The raw material supply system 2 further includes a water scrubber 35 that recovers decomposition oil by condensing gaseous hydrocarbons (HC) generated from waste plastic heated by the melting and desalination device 18. The water scrubber 35 is connected to the deaerating hopper 20. Gaseous hydrocarbons (HC) generated from the molten waste plastic in the deaerating hopper 20, and hydrogen chloride that was not fixed in the slaked lime, are sent to the water scrubber 35. The water scrubber 35 sprays water (alkaline water in this embodiment) onto the gaseous hydrocarbons (HC) and hydrogen chloride passing through it. The hydrocarbons (HC) and hydrogen chloride in the water scrubber 35 come into contact with the water, and as a result, the hydrogen chloride (HCl) is neutralized and the gaseous hydrocarbons (HC) condense to form decomposition oil.

[0035] The mixture of cracked oil and water is discharged from the water scrubber 35 and sent to the oil-water separator 37. The oil-water separator 37 is configured to separate the cracked oil from the water. The specific configuration of the oil-water separator 37 is not particularly limited, but for example, a coalescer or a sedimentation tank can be used as the oil-water separator 37. The cracked oil separated by the oil-water separator 37 is sent to the cracked oil storage tank 38 and stored in the cracked oil storage tank 38. The water separated from the cracked oil by the oil-water separator 37 is sent through the separated water discharge line 41 to a wastewater treatment device (not shown).

[0036] Thus, according to this embodiment, gaseous hydrocarbons (HC) generated from waste plastics heated by the melting desalination device 18 are recovered as decomposed oil by the water scrubber 35, thereby improving the overall yield of the decomposed oil. The specific configuration of the water scrubber 35 used is not particularly limited, and any known water scrubber can be used. For example, a washing tower equipped with a gas passage formed inside and a spray nozzle for spraying water onto the gas flowing through the passage can be used as the water scrubber 35.

[0037] In one embodiment, hydrocarbon gas containing HCl (hydrogen chloride) generated in the deaeration hopper 20 and not fixed in the slaked lime may be introduced into a combustion furnace (not shown), and the hydrocarbon gas containing HCl may be burned in the combustion furnace.

[0038] The water scrubber 35 is located downstream of the oil scrubber 40, which is described below. The oil scrubber 40 is connected to the pyrolysis furnace 6. The pyrolysis gas generated in the pyrolysis furnace 6 is first sent to the oil scrubber 40, and then to the water scrubber 35. The oil scrubber 40 cools the pyrolysis gas and condenses the gaseous pyrolysis oil (hydrocarbons) in the pyrolysis gas by spraying it with cracked oil already recovered from the pyrolysis gas or oil separately procured from an external source. Both the condensed cracked oil and the sprayed oil are discharged from the oil scrubber 40 and stored in the cracked oil storage tank 38.

[0039] The pyrolysis gas exiting the oil scrubber 40 is sent to the water scrubber 35, where it is further cooled, and any remaining cracked oil in the pyrolysis gas is recovered. Thus, in this embodiment, the pyrolysis gas discharged from the pyrolysis furnace 6 is cooled in two stages: in the oil scrubber 40 and the water scrubber 35. The oils obtained from the oil scrubber 40 and the water scrubber 35 have different distillation characteristics because they are cooled at different temperatures. For this reason, the oils obtained from the oil scrubber 40 and the water scrubber 35 may be stored separately.

[0040] The specific configuration of the oil scrubber 40 used is not particularly limited, and any known oil scrubber can be used. For example, a scrubbing tower equipped with a gas passage formed inside and a spray nozzle for spraying oil onto the gas flowing through the passage can be used as the oil scrubber 40.

[0041] Figure 2 is a schematic diagram showing another embodiment of a processing system for processing waste plastics. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to Figure 1, so redundant descriptions are omitted. In the embodiment shown in Figure 2, the raw material supply system 2 is equipped with a cracked oil properties measuring instrument 45 for measuring the properties of the cracked oil recovered from the pyrolysis gas discharged from the pyrolysis furnace 6.

[0042] The decomposed oil properties measuring instrument 45 is located downstream of the water scrubber 35 and is configured to measure the properties of the decomposed oil discharged from the water scrubber 35. More specifically, as shown in Figure 2, the decomposed oil properties measuring instrument 45 is located downstream of the oil-water separator 37, which separates the oil-water mixture discharged from the water scrubber 35 into decomposed oil and water, and is connected to piping extending from the oil-water separator 37 to the decomposed oil storage tank 38. In one embodiment, as shown in Figure 3, the decomposed oil properties measuring instrument 45 may be located downstream of the oil scrubber 40 and may measure the properties of the decomposed oil discharged from the oil scrubber 40.

[0043] Specific examples of the properties of the decomposed oil include the chlorine concentration in the decomposed oil, the acid concentration in the decomposed oil, the pH of the decomposed oil, and the pH of the water separated from the decomposed oil. These properties of the decomposed oil can vary depending on the amount of slaked lime put into the raw material hopper 27 of the melting desalination unit 18. For example, if the amount of slaked lime is too much relative to the amount of PVC and PET in the waste plastic, the pH of the decomposed oil recovered from the pyrolysis gas will be high. Therefore, based on the measured properties of the decomposed oil, an appropriate amount of slaked lime can be added to the waste plastic. The properties of the decomposed oil may be at least one or a combination of two or more of the chlorine concentration in the decomposed oil, the acid concentration in the decomposed oil, the pH of the decomposed oil, and the pH of the water separated from the decomposed oil.

[0044] Specific examples of the decomposed oil properties measuring instrument 45 include a chlorine concentration measuring instrument for measuring the chlorine concentration in the decomposed oil, an acid concentration measuring instrument for measuring the acid concentration in the decomposed oil, a pH measuring instrument for measuring the pH of the decomposed oil, and a pH measuring instrument for measuring the pH of the water separated from the decomposed oil. If the decomposed oil properties measuring instrument 45 is a pH measuring instrument for measuring the pH of the water separated from the decomposed oil, then, as shown in Figure 4, the decomposed oil properties measuring instrument 45 is connected to a separated water discharge line 41 that discharges the water separated from the decomposed oil by the oil-water separator 37. This separated water discharge line 41 is connected to the oil-water separator 37.

[0045] The decomposed oil properties measuring instrument 45 may be at least one or a combination of two or more of the following: a chlorine concentration measuring instrument for measuring the chlorine concentration in the decomposed oil, an acid concentration measuring instrument for measuring the acid concentration in the decomposed oil, a pH measuring instrument for measuring the pH of the decomposed oil, and a pH measuring instrument for measuring the pH of water separated from the decomposed oil.

[0046] The decomposition oil properties measuring instrument 45 is connected to the operation control unit 15, and the measured values ​​of the properties of the decomposition oil are sent to the operation control unit 15. The operation control unit 15 is configured to adjust (or determine) the amount of slaked lime to be added to the waste plastic based on the measured values ​​of the properties of the decomposition oil, instead of the measured values ​​of the weight of the waste plastic. If the properties (composition) of the waste plastic change significantly, ratio control may be performed based on the weight measurement value of the waste plastic, and during normal operation, the control may be switched to feedback control based on the measured values ​​from the decomposition oil properties measuring instrument 45 to adjust the amount of slaked lime supplied.

[0047] Thus, in this embodiment, the amount of slaked lime added to the waste plastic is automatically adjusted by the operation control unit 15 based on the properties of the decomposition oil contained in the pyrolysis gas discharged from the pyrolysis furnace 6 (e.g., acid concentration, chlorine concentration, pH). Therefore, the slaked lime supply device 12 can add an amount of slaked lime to the waste plastic that is sufficient to properly process both PVC and PET in the waste plastic, based on commands from the operation control unit 15.

[0048] Figure 5 is a schematic diagram showing one embodiment of a waste plastic processing system using a fluidized bed furnace. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to Figure 1, so redundant explanations are omitted.

[0049] In the embodiment shown in Figure 5, a fluidized bed furnace 1 equipped with a pyrolysis furnace 6 and a media recycling furnace 7 is incorporated into the processing system. That is, the processing system of this embodiment comprises a fluidized bed furnace 1 and a raw material supply system 2 that supplies waste plastic to the pyrolysis furnace 6 of the fluidized bed furnace 1. The pyrolysis furnace 6 in the embodiment shown in Figure 5 corresponds to the pyrolysis furnace 6 in the embodiment shown in Figure 1.

[0050] The fluidized bed furnace 1 comprises a pyrolysis furnace 6 that pyrolyzes waste plastics and generates pyrolysis gas containing pyrolysis products such as hydrocarbons, and a media regeneration furnace 7 that burns the residue of the pyrolyzed waste plastics. The interior of the fluidized bed furnace 1 is divided into the pyrolysis furnace 6 and the media regeneration furnace 7 by a partition wall 10.

[0051] The overall shape of the fluidized bed furnace 1 is not particularly limited, but for example, it may be cylindrical or rectangular. A fluidized medium (e.g., silica sand) is contained within the pyrolysis furnace 6 and the medium regeneration furnace 7. Fluidizing gas G is supplied to the pyrolysis furnace 6 and the medium regeneration furnace 7 to fluidize the fluidized medium. The raw material supply system 2 is connected to the pyrolysis furnace 6, and waste plastics are supplied into the pyrolysis furnace 6 by the raw material supply system 2. The configuration of the raw material supply system 2 is the same as that of the embodiment described with reference to Figure 1.

[0052] The fluidized medium circulates between the pyrolysis furnace 6 and the medium regeneration furnace 7, while waste plastics are fed into the pyrolysis furnace 6 by the raw material supply system 2. The waste plastics are heated by the fluidized medium in the pyrolysis furnace 6 and, after pyrolysis, become pyrolysis gas. The residue of the waste plastics is transported by the fluidized medium to the medium regeneration furnace 7, where it is incinerated. The residue of the waste plastics burns in the medium regeneration furnace 7, heating the fluidized medium. The exhaust gas generated in the medium regeneration furnace 7 is sent to an exhaust gas treatment device (not shown). The fluidized medium heated in the medium regeneration furnace 7 moves into the pyrolysis furnace 6 and functions as a heat source in the pyrolysis furnace 6. A fluidized bed furnace 1 in which the fluidized medium circulates within the furnace in this manner is called an internal circulating fluidized bed gasification system.

[0053] The slaked lime, which is fed into the waste plastic by the raw material supply system 2, is discharged from the medium recycling furnace 7 after the following chemical reaction. PVC(HCl) + Ca(OH)2 → CaCl2 + H2O PET+Ca(OH)2→TPA+CaO→TP-Ca→CaCO3+Benzene In the above, PVC(HCl) refers to hydrogen chloride derived from chlorine in PVC, TPA refers to terephthalic acid, and TP-Ca refers to calcium terephthalate.

[0054] In one embodiment, hydrocarbon gas containing HCl (hydrogen chloride) generated in the degassing hopper 20 and not fixed in the slaked lime may be guided to the media regeneration furnace 7 through the hydrocarbon gas transfer line 50. The hydrocarbon gas containing HCl is combusted in the media regeneration furnace 7, and desalination and neutralization treatment of HCl (hydrogen chloride) is performed in the exhaust gas treatment facility downstream of the media regeneration furnace 7.

[0055] Typically, equimolar or greater amounts of slaked lime are supplied to the melting desalination apparatus 18. In addition, in the media recycling furnace 7, some of the Ca salt (CaCl2) produced by the neutralization reaction is thermally decomposed. Therefore, the fluidized medium heated in the media recycling furnace 7 may be used as the heat source for the melting desalination apparatus 18. More specifically, as shown in Figure 6, a portion of the fluidized medium is sent from the media recycling furnace 7 to the melting desalination apparatus 18 via the fluidized medium transfer line 51, and the fluidized medium itself may be used as a heat source by mixing the waste plastic, slaked lime, and fluidized medium in the melting desalination apparatus 18. According to this embodiment, the thermally decomposed Ca salt and unreacted slaked lime contained in the fluidized medium can be reused, and the amount of slaked lime supplied can be reduced.

[0056] The embodiments described with reference to Figures 2 to 4 (including the arrangement and configuration of the decomposed oil properties measuring instrument 45) can also be applied to the embodiments in Figures 5 and 6, so their redundant explanations and illustrations are omitted.

[0057] The embodiments described above are intended to enable persons with ordinary skill in the art to carry out the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but is to be interpreted in the broadest sense according to the technical idea defined by the claims. [Explanation of symbols]

[0058] 1 Fluidized bed furnace 2. Raw material supply system 6 Pyrolysis furnace 7 Media regeneration furnace 10 Partition walls 12. Slaked lime supply device 15. Operation Control Unit 18. Melt-desalination apparatus 20 Vacuum hopper 22 Raw material feeder 25 Weight measuring instruments 27 Raw material hopper 29. First raw material feeder 30 Heater 31 Level Sensor 32. Second raw material feeder 35 Water Scrubber 37 Oil-water separator 38 Cracking oil storage tank 40 Oil Scrubber 41 Separate water discharge line 45. Decomposition Oil Properties Measuring Instrument 50. Hydrocarbon gas transfer line 51 Fluidized Media Transfer Line

Claims

1. A raw material supply system for thermally decomposing waste plastics, including polyvinyl chloride and polyethylene terephthalate, A slaked lime supply device for adding slaked lime to the aforementioned waste plastic, A melt desalination apparatus for desalination of polyvinyl chloride and hydrolyzes polyethylene terephthalate by heating the waste plastic and slaked lime and mixing them together, A deaeration hopper connected to the melting and desalination apparatus, which stores the waste plastic melted by the melting and desalination apparatus, A raw material supply machine that sends the molten waste plastic in the degassing hopper to a pyrolysis furnace, A raw material supply system equipped with a level sensor for detecting the liquid level of the molten waste plastic accumulated in the degassing hopper.

2. The raw material supply system further includes a water scrubber that condenses gaseous hydrocarbons generated from the heated waste plastic to recover the decomposed oil. The raw material supply system according to claim 1, wherein the water scrubber is connected to the upper part of the degassing hopper.

3. The melting and desalination apparatus further includes a raw material feeder for transferring the molten waste plastic to the deaeration hopper. The raw material supply system according to claim 1, wherein the raw material feeder operates so that the liquid level of the molten waste plastic in the degassing hopper is within a predetermined range.

4. The raw material supply system according to claim 3, wherein the predetermined range is a range that is above a level that ensures a seal between the pyrolysis furnace and the degassing hopper, and is below a level that does not exceed the volume of the degassing hopper.

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