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 in particular to a raw material supply system that supplies waste plastics to a pyrolysis furnace while processing the PVC and PET contained in the waste plastics. [Background technology]

[0002] Waste plastics include PS (polystyrene), PP (polypropylene), PE (polyethylene), as well as PVC (polyvinyl chloride) and PET (polyethylene terephthalate). Development of material recycling and chemical recycling, which process and reuse waste plastics containing these various resin components, is underway. In particular, chemical recycling, which recovers oil, gas, and other substances from waste plastics, is attracting increasing attention.

[0003] However, in order to chemically recycle waste plastics, it is necessary to process PVC and PET for the following reasons. When PVC (polyvinyl chloride) is thermally decomposed, it generates HCl (hydrogen chloride), which corrodes downstream equipment and can contaminate the decomposition oil recovered from waste plastic, resulting in a deterioration in the quality of the resulting oil. When PET (polyethylene terephthalate) is thermally decomposed in a pyrolysis furnace, it generates benzoic acid and terephthalic acid. Both of these acids sublimate and accumulate downstream, causing fouling and corrosion of downstream equipment and deterioration of quality due to acid contamination (crystal precipitation) in the decomposition oil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-107058 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 describes a method of supplying slaked lime and waste plastic to a rotary kiln, thermally decomposing the waste plastic, and desalinizing the chlorine derived from PVC in the waste plastic. However, waste plastic often contains not only PVC but also PET, and therefore, when processing waste plastic, it is necessary to process not only PVC but also PET. In particular, phthalate esters (the main component of PET) are added to PVC as plasticizers to impart flexibility, and processing aimed at either PVC or PET does 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 fouling and corrosion of equipment 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 aspect, a raw material supply system for thermally decomposing waste plastics containing polyvinyl chloride and polyethylene terephthalate is provided, the raw material supply system including: a slaked lime supplying device that adds slaked lime to the waste plastics; a melting desalination device that heats the waste plastics and the slaked lime while mixing them, thereby desalting the polyvinyl chloride and hydrolyzing the polyethylene terephthalate; a degassing hopper connected to the melting desalination device that stores the waste plastics melted by the melting desalination device; a raw material supplying machine that sends the molten waste plastics in the degassing hopper to a pyrolysis furnace; and a level sensor that detects the liquid level of the molten waste plastics accumulated in the degassing hopper.

[0008] In one aspect, a raw material supply system for thermally decomposing waste plastics containing polyvinyl chloride and polyethylene terephthalate is provided, the raw material supply system including: a slaked lime supply device that adds slaked lime to the waste plastic; 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 slaked lime to the waste plastic as the total number of moles of polyvinyl chloride and polyethylene terephthalate in the waste plastic; a melting desalination device that heats the waste plastic and the slaked lime while mixing the waste plastic with the slaked lime to desalt the polyvinyl chloride and hydrolyze the polyethylene terephthalate; a degassing hopper connected to the melting desalination device and stores the waste plastic melted by the melting desalination device; a raw material supply machine that sends the molten waste plastic in the degassing hopper to a pyrolysis furnace; and a level sensor that detects the liquid level of the molten waste plastic accumulated in the degassing hopper.

[0009] In one aspect, a raw material supply system for thermally decomposing waste plastics containing polyvinyl chloride and polyethylene terephthalate is provided, the raw material supply system comprising: a slaked lime supplying device that adds slaked lime to the waste plastic; an operation control unit that issues a command to the slaked lime supplying device to add 1 to 4 times the total number of moles of slaked lime to the waste plastic as the total number of moles of polyvinyl chloride and polyethylene terephthalate in the waste plastic; a melting desalination device that heats the waste plastic and the slaked lime while mixing the waste plastic with the slaked lime to desalt the polyvinyl chloride and hydrolyze the polyethylene terephthalate; a degassing hopper connected to the melting desalination device that stores the waste plastic melted by the melting desalination device; and a raw material supplying machine that sends the melted waste plastic in the degassing hopper to a pyrolysis furnace.

[0010] In one aspect, the raw material supply system further includes a weight measuring device that measures 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 aspect, the raw material supply system further includes a cracked oil property measuring instrument that measures the properties of the cracked oil recovered from the 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 cracked oil property measuring instrument is at least one of a chlorine concentration measuring instrument that measures the concentration of chlorine in the cracked oil, an acid concentration measuring instrument that measures the concentration of acid in the cracked oil, a pH measuring instrument that measures the pH of the cracked oil, and a pH measuring instrument that measures the pH of water separated from the cracked oil. In one aspect, the raw material supply system further includes a water scrubber that condenses gaseous hydrocarbons generated from the heated waste plastic to recover cracked oil, and the water scrubber is connected to the degassing hopper. In one aspect, the pyrolysis furnace is a fluidized bed furnace, and the fluidized bed furnace has the pyrolysis furnace and a media 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 media regeneration furnace to the melting desalination apparatus, and the portion of the fluidized medium constitutes a heat source for the melting desalination apparatus.

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

[0012] In one aspect, 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 cracked 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 values ​​of the properties of the cracked oil. In one embodiment, the properties of the cracked oil are at least one of the chlorine concentration in the cracked oil, the acid concentration in the cracked oil, the pH of the cracked oil, and the pH of water separated from the cracked oil. In one embodiment, the method further comprises a step of condensing gaseous hydrocarbons generated from the heated waste plastics using a water scrubber to recover cracked oil. In one aspect, the pyrolysis furnace is a fluidized bed furnace, which has the pyrolysis furnace and a medium regeneration furnace through which a fluidized medium circulates, and a portion of the fluidized medium is sent from the medium regeneration furnace to the melting desalination apparatus, and a portion of the fluidized medium is used as a heat source for the melting desalination apparatus. [Effects of the Invention]

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

[0014] The amount of hydrated lime added to the waste plastic is automatically adjusted based on the weight of the waste plastic to be treated or the properties of the decomposition oil recovered from the pyrolysis gas generated by the thermal decomposition of the waste plastic in the pyrolysis furnace. The weight of PVC and PET in the weight of the waste plastic can be determined by examining the composition of the waste plastic in advance. In addition, the properties (e.g., pH) of the decomposition oil recovered from the pyrolysis gas can change depending on the amount of hydrated lime added. Therefore, based on this information, the appropriate amount of hydrated lime can be added to the waste plastic. The gaseous hydrocarbons generated from the heated waste plastics are condensed in a water scrubber and recovered as cracked oil, thereby improving the yield of cracked oil. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram illustrating one embodiment of a processing system for processing waste plastics. [Figure 2] FIG. 1 is a schematic diagram illustrating another embodiment of a processing system. [Figure 3] FIG. 10 is a schematic diagram illustrating yet another embodiment of a processing system. [Figure 4] FIG. 10 is a schematic diagram illustrating yet another embodiment of a processing system. [Figure 5] FIG. 1 is a schematic diagram illustrating one embodiment of a fluidized bed type processing system for processing waste plastics. [Figure 6] FIG. 1 is a schematic diagram showing another embodiment of a fluidized bed type processing system for processing waste plastics. DETAILED DESCRIPTION OF THE INVENTION

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

[0017] As shown in Figure 1, the treatment system includes a pyrolysis furnace 6 that thermally decomposes 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. There are no particular limitations on the type of pyrolysis furnace 6, and it may be, for example, a fluidized bed pyrolysis furnace, which will be described later, or a kiln pyrolysis furnace.

[0018] The raw material supply system 2 not only has the function of supplying waste plastic to the pyrolysis furnace 6, but also has the function of processing the PVC and PET contained in the waste plastic before it is supplied to the pyrolysis furnace 6. More specifically, the raw material supply system 2 includes a slaked lime supply device 12 that adds slaked lime to the waste plastic, an operation control unit 15 that issues a command to the slaked lime supply device 12 to add to the waste plastic an amount of slaked lime that is 1 to 4 times the total number of moles of PVC (polyvinyl chloride) and PET (polyethylene terephthalate) in the waste plastic, a melting demineralizer 18 that mixes the waste plastic with the slaked lime while heating them, thereby desalting the PVC and hydrolyzing the PET, a degassing hopper 20 that is connected to the melting demineralizer 18 and stores the waste plastic melted by the melting demineralizer 18, and a raw material supply machine 22 that sends the melted waste plastic in the degassing hopper 20 to the pyrolysis furnace 6.

[0019] The raw material supply system 2 further includes a weight measuring device 25 that measures the weight of the waste plastic before the slaked lime is added. The weight of the raw material waste plastic is measured by the weight measuring device 25 and then fed into a raw material hopper 27 of the melting desalination apparatus 18. The weight measuring device 25 is, for example, a weighing conveyor that can transport the waste plastic while measuring its weight. The weight measuring device 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 desalination apparatus 18, and feeds an amount of slaked lime determined by the operation control unit 15 into the raw material hopper 27 of the melting desalination apparatus 18. Therefore, the raw material waste plastic and slaked lime are fed into the raw material hopper 27 of the melting desalination apparatus 18. The location where the slaked lime is added to the waste plastic is not limited to the raw material hopper 27, and for example, the slaked lime may be added to a storage section or a transport section for the waste plastic.

[0020] The operation control unit 15 includes a storage device 15a storing a program and a calculation device 15b that executes calculations according to instructions included in the program. The storage device 15a includes a main storage device such as a random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). Examples of the calculation device 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 the 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 plastics and slaked lime fed into the raw material hopper 27 are heated by the heater 30, mixed by the first raw material feeder 29, and sent to the degassing hopper 20. In one embodiment, the heater 30 is configured to heat the waste plastics and slaked lime to a temperature in the range of 250°C to 350°C. The structure and arrangement of the heater 30 are not particularly limited as long as it can heat the mixture of waste plastics and slaked lime to a temperature in the range of 250°C to 350°C. Specific examples of the heater 30 include a steam heater, an electric heater, and a heater that uses a heated inert gas (e.g., nitrogen gas) as a heat source. The heating method may be direct heating, indirect heating, or a combination of these.

[0022] The melting and demineralizing unit 18 heats a mixture of waste plastic and slaked lime using a heater 30 to demineralize the PVC contained in the waste plastic. 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 Ca salt (CaCl2). As a result, contact and reaction between the cracked oil in the pyrolysis gas generated in the downstream pyrolysis furnace 6 and chlorine can be avoided, reducing the generation of organic chlorine compounds.

[0023] Furthermore, the melting and demineralizing unit 18 heats the mixture of waste plastic and slaked lime with a heater 30 to hydrolyze the PET contained in the waste plastic. More specifically, the PET is heated together with slaked lime to 250°C to 350°C to produce calcium terephthalate. This calcium terephthalate is thermally decomposed in the pyrolysis furnace 6, which suppresses the production of sublimable benzoic acid and terephthalic acid, thereby improving the yield of cracked oil (particularly benzene).

[0024] According to this embodiment, 1 to 4 times the total number of moles of slaked lime as the total number of moles of PVC (polyvinyl chloride) and PET (polyethylene terephthalate) in the waste plastic is supplied to the waste plastic, thereby achieving appropriate desalination of the PVC and appropriate hydrolysis of the PET simultaneously. As a result, appropriate chemical recycling of the waste plastic can be achieved in the downstream 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 treated. The weight of PVC and PET in the weight of 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 supplying device 12 can add an amount of slaked lime to the waste plastic that will allow both the PVC and PET in the waste plastic to be properly treated.

[0026] The weight of PVC and PET in the weight of waste plastic is, more specifically, the weight of chlorine and acid in the weight of waste plastic. Therefore, the amount of slaked lime added to the waste plastic is the amount necessary to treat the chlorine and acid contained in the waste plastic. Below is an example of the amount of slaked lime to be added to the waste plastic.

[0027] (1) When the amount of PVC and PET mixed in the waste plastic is known If the weight measurement value of the waste plastic is W (kg / H), the proportion of PVC is x (wt%), and the proportion of PET is y (wt%), the amount of 1 mole of slaked lime w (kg / H) can be calculated using 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 measured weight of the waste plastic is W (kg / H), the chlorine percentage from the elemental analysis is α (wt%), and the oxygen percentage is β (wt%), the amount of 1 mole of slaked lime w (kg / H) can be calculated using 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 (skeleton): (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 HCl is produced by thermal decomposition of 1 mole of PVC, then 0.5 moles of slaked lime Ca(OH)2 are required for neutralization. Also, if 2 moles of -COOH are produced by hydrolysis of 1 mole of PET, then 1 mole of slaked lime Ca(OH)2 is required for neutralization.

[0030] The waste plastic is melted by being heated to 250°C to 350°C in the melting and demineralizing device 18. By melting the waste plastic, the waste plastic is uniformly mixed with the hydrated lime, improving the efficiency of dechlorinating PVC and hydrolyzing PET.

[0031] The melted waste plastic is transported to the degassing hopper 20 by the first raw material feeder 29. The weight measurement value of the weight measuring device 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 weight measurement value of the weight measuring device 25. In the degassing hopper 20, air present in the gaps between the waste plastic, gaseous HCl that was not fixed to the slaked lime as Ca salt, and gaseous hydrocarbons are separated from the melted waste plastic. Melting the waste plastic separates the air from the waste plastic, preventing air from being supplied 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 be promoted. Combustion of the waste plastic in the pyrolysis furnace 6 may be prevented by introducing an inert gas such as nitrogen or water vapor into the degassing hopper 20.

[0032] The raw material supply system 2 is equipped with a level sensor 31 that detects the liquid level of the liquid waste plastic accumulated in the degassing hopper 20. The measured value of the 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 degassing hopper 20 is within a predetermined range. Here, the predetermined range means a level that is equal to or higher than the level at which the sealing between the pyrolysis furnace 6 and the degassing hopper 20 is ensured, taking into account pressure fluctuations in the pyrolysis furnace 6, and is equal to or lower than the level at which the volume of the degassing hopper 20 is not exceeded.

[0033] The raw material supply machine 22 is equipped with a second raw material feeder 32 that sends the melted waste plastic in the degassing hopper 20 to the pyrolysis furnace 6. The second raw material feeder 32 is configured to continuously or intermittently send 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 condenses gaseous hydrocarbons (HC) generated from the waste plastics heated by the melting and demineralizing unit 18 to recover cracked oil. The water scrubber 35 is connected to the degassing hopper 20. The gaseous hydrocarbons (HC) generated from the melted waste plastics in the degassing hopper 20 and the hydrogen chloride not fixed to the hydrated 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 its interior. The hydrocarbons (HC) and hydrogen chloride in the water scrubber 35 come into contact with the water, resulting in neutralization of the hydrogen chloride (HCl) and condensation of the gaseous hydrocarbons (HC) to form cracked oil.

[0035] The mixture of cracked oil and water is discharged from the water scrubber 35 and sent to an 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 a 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 to a wastewater treatment device (not shown) through a separated water discharge line 41.

[0036] As described above, according to this embodiment, gaseous hydrocarbons (HC) generated from waste plastics heated by the melting and desalination unit 18 are recovered as cracked oil by the water scrubber 35, thereby improving the overall yield of cracked 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 having a gas passage formed therein and spray nozzles that spray water onto the gas flowing through the passage can be used as the water scrubber 35.

[0037] In one embodiment, the hydrocarbon gas containing HCl (hydrogen chloride) that is generated in the degassing hopper 20 and that has not been fixed in the hydrated lime may be introduced into a combustion furnace (not shown), and the hydrocarbon gas containing HCl may be combusted in the combustion furnace.

[0038] The water scrubber 35 is located downstream of the oil scrubber 40, which will be 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 sent to the water scrubber 35. The oil scrubber 40 sprays cracked oil that has already been recovered from the pyrolysis gas or oil separately procured from outside into the pyrolysis gas, thereby cooling the pyrolysis gas and condensing the gaseous cracked oil (hydrocarbons) in the pyrolysis gas. 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 leaving the oil scrubber 40 is sent to the water scrubber 35, where it is further cooled and the cracked oil remaining in the pyrolysis gas is recovered. In this way, in this embodiment, the pyrolysis gas discharged from the pyrolysis furnace 6 is cooled in two stages, the oil scrubber 40 and the water scrubber 35. The oils obtained in the oil scrubber 40 and the water scrubber 35 have different cooling temperatures and therefore different distillation characteristics. For this reason, the oils obtained from the oil scrubber 40 and the water scrubber 35 may be stored separately.

[0040] There are no particular limitations on the specific configuration of the oil scrubber 40 used, and any known oil scrubber can be used. For example, the oil scrubber 40 can be a washing tower having a gas passage formed therein and spray nozzles for spraying oil into the gas flowing through the passage.

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

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

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

[0044] Specific examples of the cracked oil property measuring instrument 45 include a chlorine concentration measuring instrument that measures the concentration of chlorine in the cracked oil, an acid concentration measuring instrument that measures the concentration of acid in the cracked oil, a pH measuring instrument that measures the pH of the cracked oil, and a pH measuring instrument that measures the pH of the water separated from the cracked oil. When the cracked oil property measuring instrument 45 is a pH measuring instrument that measures the pH of the water separated from the cracked oil, as shown in FIG. 4, the cracked oil property measuring instrument 45 is connected to a separated water discharge line 41 that discharges the water separated from the cracked oil by the oil-water separator 37. This separated water discharge line 41 is connected to the oil-water separator 37.

[0045] The cracked oil property measuring instrument 45 may be at least one of, or a combination of two or more of, a chlorine concentration measuring instrument that measures the concentration of chlorine in the cracked oil, an acid concentration measuring instrument that measures the concentration of acid in the cracked oil, a pH measuring instrument that measures the pH of the cracked oil, and a pH measuring instrument that measures the pH of the water separated from the cracked oil.

[0046] The cracked oil property measuring instrument 45 is connected to the operation control unit 15, and the measured values ​​of the cracked oil properties 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 cracked oil properties instead of the measured values ​​of the weight of the waste plastic. When the properties (composition) of the waste plastic change significantly, ratio control is performed based on the measured weight value of the waste plastic, and during normal operation, it is possible to switch to feedback control based on the measured values ​​from the cracked oil property measuring instrument 45 and adjust the amount of slaked lime supplied.

[0047] As described above, 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 (e.g., acid concentration, chlorine concentration, pH) of the cracked oil contained in the pyrolysis gas discharged from the pyrolysis furnace 6. Therefore, based on a command from the operation control unit 15, the slaked lime supplying device 12 can add an amount of slaked lime to the waste plastic that is sufficient to properly treat both the PVC and PET in the waste plastic.

[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 duplicated explanations will be omitted.

[0049] In the embodiment shown in Fig. 5, a fluidized bed furnace 1 equipped with a pyrolysis furnace 6 and a media regeneration furnace 7 is incorporated into the treatment system. That is, the treatment system of this embodiment includes the 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 Fig. 5 corresponds to the pyrolysis furnace 6 in the embodiment shown in Fig. 1.

[0050] The fluidized-bed furnace 1 has a pyrolysis furnace 6 that pyrolyzes waste plastics to produce 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 separated 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 may be cylindrical or rectangular, for example. A fluidized medium (e.g., silica sand) is contained in the pyrolysis furnace 6 and the medium regeneration furnace 7. A fluidizing gas G is supplied to the pyrolysis furnace 6 and the medium regeneration furnace 7 to fluidize the fluidized medium. A raw material supply system 2 is connected to the pyrolysis furnace 6, and waste plastic is 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 FIG. 1.

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

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

[0054] In one embodiment, the hydrocarbon gas containing HCl (hydrogen chloride) that is generated in the degassing hopper 20 and not fixed in the hydrated lime may be introduced into the media regeneration furnace 7 through a hydrocarbon gas transfer line 50. The hydrocarbon gas containing HCl is combusted in the media regeneration furnace 7, and the HCl (hydrogen chloride) is desalination-neutralized in an exhaust gas treatment facility downstream of the media regeneration furnace 7.

[0055] The melting demineralizer 18 is usually supplied with equimolar or more slaked lime. Furthermore, in the media regeneration furnace 7, a portion of the Ca salt (CaCl) produced by the neutralization reaction is thermally decomposed. Therefore, the fluidized medium heated in the media regeneration furnace 7 may be used as the heat source for the melting demineralizer 18. More specifically, as shown in FIG. 6, a portion of the fluidized medium may be sent from the media regeneration furnace 7 to the melting demineralizer 18 via a fluidized medium transfer line 51, and the melting demineralizer 18 may mix the waste plastic, slaked lime, and fluidized medium, thereby using the fluidized medium itself as the heat source. According to this embodiment, the thermally decomposed Ca salt and unreacted slaked lime contained in the fluidized medium can be reused, thereby reducing the amount of slaked lime supplied.

[0056] In addition, the embodiment described with reference to Figures 2 to 4 (including the arrangement and configuration of the decomposed oil property measuring instrument 45) can also be applied to the embodiment of Figures 5 and 6, so duplicate explanations and illustrations will be omitted.

[0057] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would be obvious to a person skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept 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 Wall 12 Slaked lime supply device 15 Operation control section 18 Melting desalination plant 20 Degassing hopper 22 Raw material feeder 25 Weight measuring instrument 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 Separated water discharge line 45 Decomposition oil property measuring instrument 50 Hydrocarbon gas transfer line 51 Bed media transfer line

Claims

1. A raw material supply system for pyrolyzing waste plastics including polyvinyl chloride and polyethylene terephthalate, comprising: A slaked lime supplying device that adds slaked lime to the waste plastic; a melting and desalination apparatus for mixing the waste plastics and the slaked lime while heating them, thereby desalting the polyvinyl chloride and hydrolyzing the polyethylene terephthalate; a degassing hopper connected to the melting and desalination apparatus and configured to store the waste plastics melted by the melting and desalination apparatus; a raw material feeder that sends the molten waste plastic in the degassing hopper to a pyrolysis furnace; A raw material supply system comprising 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 cracked oil, 2. The raw material feeding system of claim 1, wherein the water scrubber is connected to the top of the degassing hopper.

3. The melting and desalination apparatus further includes a raw material feeder that transfers the melted waste plastic to the degassing hopper, 2. 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. 4. The raw material supply system according to claim 3, wherein the predetermined range is equal to or greater than a level at which sealing between the pyrolysis furnace and the degassing hopper is ensured, and is equal to or less than a level at which the volume of the degassing hopper is exceeded.

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