Waste plastic oil conversion device

Abstract

To provide a waste plastic oil conversion device that can operate continuously and reduce heat energy consumption.SOLUTION: An oil conversion device 1 comprises: a melting tank 10 that heats and melts a waste plastic P0; a waste plastic supply device 23 that can continuously feed the waste plastic P0 into the melting tank 10 while heating and melting thereof; a first decomposition tank 11 that introduces a molten plastic P1 into the melting tank 10 to generate thermal decomposition gas G1, and introduces the thermal decomposition gas G1 into the melting tank 10; and a first oil storage tank that stores a produced oil obtained by condensing the thermal decomposition gas G1 after heat exchange with the waste plastic P0 in the melting tank 10. In the melting tank 10, the waste plastic P0 is melted by the thermal decomposition gas G1 generated in the first decomposition tank 11, the waste plastic P0 mixed with the molten plastic P1 supplied from the waste plastic supply device 23, and a thermal energy supplied from a heating tube 14.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a waste plastic oil conversion device.

Background Art

[0002] There is a waste plastic oil conversion device that heats and melts waste plastics mainly composed of plastics such as plastic products discarded after use and plastic residues generated during the manufacturing process of plastic products, further thermally decomposes the melted waste plastics to generate pyrolysis gas, and condenses this pyrolysis gas to recover it as a produced oil such as fuel oil. However, a large amount of heat energy is required for the heating and melting and thermal decomposition of waste plastics, and reduction of this consumed heat energy has been an issue.

[0003] Patent Document 1 discloses a waste plastic oil conversion device that heats and melts waste plastics in a heating furnace, condenses the generated decomposition gas, and recovers it as a produced oil. The heating furnace is heated by burning fuel oil or gas with an oil burner or a gas burner. The gas burner uses the undecomposed decomposition gas after passing through the condenser as fuel. Further, this oil conversion device once stops the operation of the oil conversion device after the oil conversion of the waste plastics in the heating furnace is completed, and reintroduces the waste plastics into the heating furnace to start heating and melting.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the above-mentioned Patent Document 1, undecomposed gas that is not condensed in the condenser is burned and used as thermal energy for the heating furnace. However, the amount of this undecomposed gas is not sufficient to melt the waste plastic in the heating furnace and generate decomposition gas, so in practice, it is necessary to rely on an oil burner, and it is difficult to reduce the amount of thermal energy consumed. Furthermore, since this liquefaction device cannot operate continuously, heating of the heating furnace must be started when waste plastic is reintroduced, which presents a problem of significant energy loss.

[0006] Therefore, the present invention was made to solve these problems and aims to realize a waste plastic oil conversion device that can achieve continuous operation and reduce thermal energy consumption. [Means for solving the problem]

[0007] [1] The waste plastic oil conversion apparatus of the present invention is characterized by comprising: a melting tank for heating and melting waste plastic; a waste plastic supply device capable of continuously feeding the waste plastic into the melting tank while heating and melting it; a first decomposition tank for introducing the molten plastic in the melting tank to generate pyrolysis gas and introducing the pyrolysis gas into the melting tank; and an oil storage tank for storing the generated oil obtained by condensing the pyrolysis gas after heat exchange with the waste plastic in the melting tank.

[0008] [2] In the waste plastic oil conversion apparatus of the present invention, it is preferable that the first decomposition tank has a heavy oil supply port that can supply heavy oil before the introduction of the molten plastic or during the generation of the pyrolysis gas.

[0009] [3] In the waste plastic liquefaction apparatus of the present invention, the waste plastic supply device has a screw feeder, the first decomposition tank is connected to the melting tank by a connecting pipe through which the screw feeder is inserted, and the connecting pipe is preferably configured to allow the pyrolysis gas generated in the first decomposition tank to flow around the screw feeder.

[0010] [4] In the waste plastic liquefaction apparatus of the present invention, the melting tank is preferably configured to be heated by the thermal decomposition gas sent from the first decomposition tank passing through the space and the bottom plate, the heated and molten waste plastic supplied by the waste plastic supply device, and the thermal energy supplied from the heating tank, wherein the melting tank is preferably configured to be heated by the thermal decomposition gas sent from the first decomposition tank passing through the space and the bottom plate, the heated and molten waste plastic supplied by the waste plastic supply device, and the thermal energy supplied from the heating tank.

[0011] [5] In the waste plastic oil conversion apparatus of the present invention, a catalyst is supported on the inner wall surface of the first decomposition tank, Preferably, the device further includes a gas agitator that rotates along the inner wall surface and blows the decomposition gas generated in the first decomposition tank onto the catalyst.

[0012] [6] In the waste plastic oil conversion apparatus of the present invention, it is preferable that a terephthalic acid removal unit is further provided between the melting tank and the oil storage tank, which is capable of introducing a decomposition gas cooled to the sublimation temperature of terephthalic acid, and crystallizing and discharging the terephthalic acid, and that the terephthalic acid removal unit has at least two detachable terephthalic acid separation cylinders.

[0013] [7] In the waste plastic oil conversion apparatus of the present invention, it is preferable that a water seal tank is further provided downstream of the oil storage tank for introducing separated gas that does not liquefy in the oil storage tank, and that the water seal tank is connected to a neutralization tank through which a neutralizing liquid circulates for neutralizing the chlorine component of the separated gas.

[0014] [8] The waste plastic liquefaction apparatus of the present invention further comprises a second decomposition tank that introduces the molten plastic overflowing from the first decomposition tank and generates the pyrolysis gas, wherein the pyrolysis gas generated in the second decomposition tank is connected so as to be able to merge with the pyrolysis gas sent out from the melting tank, or is connected to the melting tank via the waste plastic supply device. [Effects of the Invention]

[0015] The waste plastic liquefaction apparatus introduces molten plastic, melted in a melting tank, into a first decomposition tank, and then introduces the pyrolysis gas generated by the decomposition into the melting tank. The waste plastic is melted by the thermal energy of the pyrolysis gas generated in the first decomposition tank, the thermal energy of the molten plastic including the waste plastic introduced from the screw feeder, and the thermal energy supplied to the melting tank from the heating cylinder. Therefore, the supply of external thermal energy necessary for melting the waste plastic can be reduced, and the amount of thermal energy consumed can be reduced.

[0016] Furthermore, by supplying heavy oil (e.g., heavy fuel oil) to the first decomposition tank in advance and heating it, the latent heat required for melting is eliminated, allowing for the generation of pyrolysis gas in a short time. By recirculating this pyrolysis gas to the melting tank, it can be used as thermal energy to melt the waste plastic in the melting tank, thereby accelerating the melting of the waste plastic within the melting tank.

[0017] Furthermore, since the waste plastic liquefaction device continuously feeds waste plastic into the melting tank while heating and melting it using a waste plastic supply device, it is not necessary to reheat the melting tank each time waste plastic is added. This allows for continuous operation and increases the operating rate.

[0018] The waste plastic oil conversion apparatus of the present invention, as described above, can increase operating efficiency and reduce thermal energy consumption. [Brief explanation of the drawing]

[0019] [Figure 1] It is a configuration explanatory diagram showing the configuration of the waste plastic oilification device 1. [Figure 2] It is an explanatory diagram schematically showing an example of the configuration of the terephthalic acid removal unit 49.

Embodiments for Carrying out the Invention

[0020] Hereinafter, the waste plastic oilification device 1 according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. In the following description, the waste plastic oilification device 1 may be briefly described as the oilification device 1. Here, the waste plastic P0 to be oilified is a plastic product discarded after use, plastic scraps generated in the manufacturing process of plastic products, etc., and is a thermoplastic such as polystyrene, polypropylene, polyethylene, styrofoam (expanded polystyrene), polyethylene terephthalate (PET), vinyl chloride, etc.

[0021] FIG. 1 is a configuration explanatory diagram showing the configuration of the oilification device 1. The arrows shown in each of the figures described below indicate the flow direction of each generated decomposition gas. The oilification device 1 has a melting tank 10 for heating and melting the waste plastic P0, and a first decomposition tank 11 for introducing and heating the melted waste plastic P0 (referred to as the melted plastic P1) in the melting tank 10 to generate a pyrolysis gas G1, and introducing this pyrolysis gas G1 into the melting tank 10. The pyrolysis gas G1 becomes a decomposition gas G2 whose temperature has decreased by heat exchange with the waste plastic P0 in the melting tank 10, and the decomposition gas G2 changes into a decomposition gas G3 controlled to a predetermined temperature via a temperature controller 42. The oilification device 1 has a first oil storage tank 12 for condensing and storing this decomposition gas G3, and a second oil storage tank 19 for condensing and storing the separation gas G4 that does not liquefy in the first oil storage tank 12. The melting tank 10 is connected to a waste plastic supply device 23 for charging while melting the waste plastic P0.

[0022] The melting tank 10 has a double structure including a bottomed melting cylinder 13 that accommodates and melts the waste plastic P0 input from the waste plastic supply device 23, and a heating cylinder 14 that accommodates the melting cylinder 13 and heats the melting cylinder 13 from the outer peripheral side. The waste plastic supply device 23 is a device that inputs the waste plastic P0 into the melting tank 10 while melting it. In the waste plastic supply device 23, since the waste plastic P0 has a mixture of molten and solid components, in the melting tank 10, solid waste plastic P0, molten plastic P1 with fluidity, and high-boiling-point pyrolysis gas G1 are mixed. A space 22 is formed between the melting cylinder 13 and the heating cylinder 14. At the bottom of the melting cylinder 13, a bottom plate 15 is provided that partitions a region for melting the waste plastic P0 and a region for the molten plastic P1 to flow, and has a large number of small holes through which the molten plastic P1 and the pyrolysis gas G1 can pass. The heating cylinder 14 is a cylinder with a conical bottom, and heaters 16 are arranged on the outer periphery of the bottom and the side surface, and indirectly heats the melting cylinder 13 to a temperature at which the waste plastic P0 can melt and flow.

[0023] The bottom plate 15 has a large number of small holes through which the molten plastic P1 can naturally fall, and may be, for example, a mesh steel plate. That is, the number, size, and arrangement of the small holes of the bottom plate 15 are set so that the molten plastic P1 with fluidity can fall below the heating cylinder 14 and the pyrolysis gas G1 generated in the first decomposition tank 11 can be sent into the melting cylinder 13.

[0024] At the top of the melting cylinder 13, a catalyst inlet 17 for injecting a catalyst (for example, synthetic zeolite, etc.) is provided, and a connecting pipe 18 for sending out the pyrolysis gas G1 is connected. Inside the melting cylinder 13, a stirring blade 20 is provided, and the stirring blade 20 is rotated by a motor 21. The stirring blade 20 stirs the waste plastic P0, molten plastic P1, and pyrolysis gas G1 introduced from the first decomposition tank 11 that are mixed in the melting cylinder 13, and promotes the melting of the waste plastic P0.

[0025] The waste plastic supply device 23 consists of a hopper 25 that supplies waste plastic P0 to a screw feeder 24, and a motor 26 that drives the screw feeder 24. The screw feeder 24 is connected to the upper side of the melting tank 10 and feeds the waste plastic P0 into the melting tank 10 while melting it. Although not shown in the diagram, a crusher, washing device, dewatering device, etc. are placed in front of the hopper 25 to crush, wash, and dewater the waste plastic raw material so that it can be supplied to the screw feeder 24 before being fed into the hopper 25. The screw feeder 24 is filled with an inert gas (for example, nitrogen gas N2) to prevent oxygen from entering the melting tank 10 and burning the waste plastic P0 and molten plastic P1. Since the waste plastic P0 fed into the waste plastic supply device 23 includes, for example, packaging bags from households, it is preferable to provide the waste plastic supply device 23 with a feeding device that can feed in these packaging bags.

[0026] The melting tank 10 and the first decomposition tank 11 are connected by a connecting pipe 30. The connecting pipe 30 is connected to the lower end of the heating cylinder 14 and to the upper side of the first decomposition tank 11. That is, the first decomposition tank 11 is positioned below the melting tank 10 so that the molten plastic P1 flows naturally from the melting tank 10 to the first decomposition tank 11. The molten plastic P1 introduced from the melting tank 10 falls along the inner circumferential wall of the first decomposition tank 11. A heater 31 is provided on the outer circumference of the first decomposition tank 11 to heat the molten plastic P1 to 400°C to 500°C. Since the molten plastic P1 introduced from the melting tank 10 into the first decomposition tank 11 is at 200°C to 300°C, the heat energy consumed when heating it to 400°C to 500°C can be reduced compared to heating from room temperature to 400°C to 500°C.

[0027] A heavy oil supply port 32 is provided at the top of the first decomposition tank 11. Heavy oil KH and a catalyst can be supplied from the heavy oil supply port 32. The heavy oil KH (e.g., heavy fuel oil) is added in advance before the melting tank 10 starts operation. Alternatively, if there is a delay in the supply of molten plastic P1 from the melting tank 10 to the first decomposition tank 11, additional heavy oil KH is added to the first decomposition tank 11. By supplying heavy oil KH into the first decomposition tank 11 in this way, the generation of pyrolysis gas G1 in the first decomposition tank 11 is promoted, and it becomes possible to supply pyrolysis gas G1 at a sufficiently high temperature to the melting tank 10. In other words, it becomes possible to supply the thermal energy necessary for melting the waste plastic P0 in the melting tank 10. However, it is also possible to supply granular waste plastic P0 from the heavy oil supply port 32, and it is also possible to mix granular waste plastic P0 with the heavy oil KH before adding it.

[0028] An agitator 33 is provided inside the first decomposition tank 11. The agitator 33 rotates along the bottom surface of the first decomposition tank 11 and has an agitator blade 34 for agitating the heavy oil KH and molten plastic P1, and a gas agitator blade 35 for agitating the pyrolysis gas G1. The agitator blade 34 and the gas agitator blade 35 are fixed to a shaft member 36 and rotated by a motor 37. The agitator blade 34 has the function of agitating the molten plastic P1, heavy oil KH and catalyst to equalize the temperature and promote the generation of pyrolysis gas G1 from the molten plastic P1. The agitator blade 34 also has the function of scraping off residue adhering to the bottom of the first decomposition tank 11. The gas agitator blade 35 agitates the generated pyrolysis gas G1. A metal plate (not shown in the figure) on which a catalyst is supported is fixed to the inner surface of the first decomposition tank 11, and by rotating the gas stirring blade 35, the pyrolysis gas G1 is brought into contact with the catalyst as if being blown onto it, thereby arranging the molecular structure of the pyrolysis gas G1.

[0029] The pyrolysis gas G1 generated in the first decomposition tank 11 is introduced into the space 22 between the melting cylinder 13 and the heating cylinder 14 through connecting pipes 38 and 39. A screw feeder 24 is inserted through connecting pipe 39, and the outer circumference of the screw feeder 24 is heated by the pyrolysis gas G1. In other words, the waste plastic P0 sent by the screw feeder 24 is heated to 400°C to 500°C and is introduced into the melting tank 10 while melting. However, the melting tank 10 contains a mixture of molten plastic P1 and waste plastic P0 that has not been melted.

[0030] Furthermore, the connecting pipes 30, 38, and 39 and the molten tank 10 are covered with insulating material 40. By providing insulating material 40, the temperature of the pyrolysis gas G1 from the first decomposition tank 11 to the molten tank 10, the temperature of the molten plastic P1 from the molten tank 10 to the first decomposition tank 11, and the molten tank 10 itself are prevented from decreasing.

[0031] Next, the melting of waste plastic P0 in the melting tank 10 will be explained with reference to Figure 1. Inside the melting cylinder 13, thermal decomposition gas G1 is supplied from the first decomposition tank 11 through the space 22 between the melting cylinder 13 and the heating cylinder 14, through small holes in the bottom plate 15, heated waste plastic P0 and molten plastic P1 are supplied from the waste plastic supply device 23, and thermal energy is supplied from the heating cylinder 14. The thermal energy supplied from these three sources is first used to melt the waste plastic P0. In other words, this thermal energy is consumed as latent heat during the melting process of the waste plastic P0. Therefore, the thermal decomposition gas G1 becomes decomposition gas G2, whose temperature has decreased through heat exchange with the waste plastic P0 in the melting tank 10, and is sent to the first oil storage tank 12.

[0032] The pyrolysis gas G1 introduced from the first decomposition tank 11 cools down through heat exchange with the waste plastic P0, becoming decomposition gas G2. The decomposition gas G2 sent from the melting tank 10 passes through connecting pipe 18, temperature controller 42, and connecting pipe 47 to the terephthalic acid removal section 49. At this time, the decomposition gas G2 is cooled or heated in the temperature controller 42 and sent to the terephthalic acid removal section 49 as decomposition gas G3 at the sublimation temperature of terephthalic acid (approximately 300°C). The configuration of the terephthalic acid removal section 49 will be explained with reference to Figure 2. The terephthalic acid contained in the decomposition gas G3 crystallizes in the terephthalic acid removal section 49 and is stored in the first oil storage tank 12 together with the low-boiling point light oil KL that has condensed at 300°C in the terephthalic acid removal section 49. The first oil storage tank 12 is cooled to room temperature by cooling water W.

[0033] The first oil storage tank 12 has an overflow wall 43. The light oil KL is initially stored in one of the storage sections 12A, which is separated by the overflow wall 43. When it reaches a certain amount, the supernatant moves to storage section 12B through a hole 43a in the overflow wall 43. In the light oil KL stored in storage section 12A, some of the crystallized terephthalic acid and fine particles contained in the cracking gas G3 settle to the bottom due to the difference in specific gravity with the light oil KL and can be recovered. The light oil KL accumulated in storage section 12B can be recovered as a useful product oil, so-called diesel fuel, which does not contain terephthalic acid or fine particles.

[0034] In the first oil storage tank 12, the low-boiling-point separation gas G4, which does not liquefy at room temperature, is condensed in the cooler 53 and stored in the second oil storage tank 19 as light oil KL0 such as gasoline. In the second oil storage tank 19, the low-boiling-point separation gas G5, which does not liquefy, is introduced into the water seal tank 57 (also called a water sealer) through the connecting pipe 56. The separation gas G5 is a volatile combustible gas such as ethane or methane with 5 or fewer carbon atoms. The water seal tank 57 is filled with neutralizing liquid Q. The tip of the connecting pipe 56 is always submerged in the neutralizing liquid Q, and the separation gas G5 does not dissolve in the neutralizing liquid Q but floats to the space above the liquid surface and is discharged from the discharge pipe 58. The liquid level in the water seal tank 57 is kept constant. The primary role of the water seal tank 57 is to create a positive pressure in the system leading to the melting tank 10 and the first decomposition tank 11, thereby preventing oxygen from entering the system.

[0035] A neutralization tank 59 is connected to the water seal tank 57. In this example, the neutralization tank 59 stores a neutralizing solution Q, such as an aqueous solution of caustic soda. By circulating the aqueous solution of caustic soda between the water seal tank 57 and the neutralization tank 59, the chlorine contained in the separated gas G5 is neutralized. In other words, the water seal tank 57 has the above-mentioned original function as well as a dechlorination function. The separated gas G6 that does not liquefy in the water seal tank 57 is introduced to the exhaust gas treatment device 60 through the discharge pipe 58. The exhaust gas treatment device 60 uses a catalyst to decompose the separated gas G6 into carbon dioxide and water (water vapor) and discharges it to the outside as exhaust gas GE. It is also possible to incinerate the separated gas G6 in an incinerator or the like before discharge. When incinerated, the generation of dioxins can be prevented because the chlorine has been removed from the separated gas G6.

[0036] The oil conversion apparatus 1 circulates the thermal energy of molten plastic P1 and pyrolysis gas G1 between the melting tank 10 and the first decomposition tank 11, melting the waste plastic P0 in the melting tank 10. The oil conversion apparatus 1 can be equipped with a second decomposition tank 45 connected to the first decomposition tank 11. The second decomposition tank 45 has almost the same configuration as the first decomposition tank 11, and contains the molten plastic P1 that overflows from the first decomposition tank 11 and heats it at 400°C to 500°C to generate pyrolysis gas G1. A catalyst inlet 46 is provided at the top of the second decomposition tank 45. A catalyst such as synthetic zeolite is introduced from the catalyst inlet 46. The catalyst is stirred together with the molten plastic P1 by the stirring blade 34, and the catalyst promotes the generation of pyrolysis gas G1 from the molten plastic P1. Heavy oil KH can be introduced from the catalyst inlet 46 to promote the generation of pyrolysis gas G1.

[0037] A stirrer 33 similar to that in the first decomposition tank 11 is installed inside the second decomposition tank 45. The stirrer 33 rotates along the bottom surface of the second decomposition tank 45 and has a stirring blade 34 for stirring the molten plastic P1 and a gas stirring blade 35 for stirring the pyrolysis gas G1. The stirring blade 34 and the gas stirring blade 35 are fixed to a shaft member 36 and rotated by a motor 37. The stirring blade 34 has the function of stirring the molten plastic P1 to make the temperature uniform and scraping off residue adhering to the bottom of the second decomposition tank 45. The gas stirring blade 35 stirs the generated pyrolysis gas G1. A metal plate (not shown) on which a catalyst is supported is fixed to the inner circumferential surface of the second decomposition tank 45. By rotating the gas stirring blade 35, the pyrolysis gas G1 is blown onto the catalyst and brought into contact with it. A high-boiling-point pyrolysis gas G1 is generated from the molten plastic P1, and the catalyst is used to arrange the molecular structure of the pyrolysis gas G1. It is also possible to introduce heavy oil KH (e.g., heavy fuel oil) through the catalyst inlet 46. Mixing the heavy oil KH with the molten plastic P1 and heating it promotes the generation of pyrolysis gas G1. The second decomposition tank 45 is provided to supplement the first decomposition tank 11 when the amount of pyrolysis gas G1 generated in the first decomposition tank 11 is less than expected.

[0038] The decomposition gas G2 generated in the second decomposition tank 45 is cooled to the sublimation temperature of terephthalic acid (300°C) in the cooler 48, merges with the decomposition gas G3 sent from the melting tank 10 in the connecting pipe 47, and is sent to the terephthalic acid removal section 49.

[0039] Although not shown in the diagram, the pyrolysis gas G1 generated in the second decomposition tank 45 may be introduced into the melting tank 10 by joining it with the connecting pipe 38. Alternatively, the decomposition gas G2 generated in the second decomposition tank 45 may be introduced directly into the melting tank 10. In this way, the pyrolysis gas G1 generated in the second decomposition tank 45 can be used in the melting tank 10 as thermal energy for melting the waste plastic P0. The pyrolysis gas G1 generated in the melting tank 10 and cooled to 300°C in the cooler 48 is separated into decomposition gas G3 of light oil components with a boiling point of 300°C and heavy oil components with a boiling point of 300°C or higher, and the heavy oil components liquefy and fall into the melting tank 10.

[0040] At the bottom of the melting tank 10, the first decomposition tank 11, and the second decomposition tank 45, there are outlets 50, 51, and 52, respectively, for removing the residue and impurities of the molten plastic P1 that has settled in each tank.

[0041] Figure 2 is a schematic diagram illustrating one example of the configuration of the terephthalic acid removal unit 49. Figure 2(a) is a plan view of the terephthalic acid removal unit 49 viewed from above, and Figure 2(b) is a cross-sectional view taken along the AA cutting line in Figure 2(a). As shown in Figure 2(a), the connecting pipe 47 is branched horizontally into connecting pipes 47a and 47b, and on-off valves V1 and V2 are provided in each of the connecting pipes 47a and 47b. Decomposition gas G3 is introduced into the connecting pipes 47a and 47b. Terephthalic acid condensing cylinders 61A and 61B are provided at the ends of the branched connecting pipes 47a and 47b, respectively. Since the terephthalic acid condensing cylinders 61A and 61B have the same configuration, the detailed configuration will be explained by referring to Figure 2(b) with the terephthalic acid condensing cylinder 61A as a representative example.

[0042] The terephthalic acid condensate cylinder 61A consists of a terephthalic acid separation cylinder 63 having a lateral hole 62 communicating with the connecting pipe 47a, and a cooling cylinder 64 into which the terephthalic acid separation cylinder 63 is inserted. A space 65 through which the decomposition gas G3 can flow is provided between the terephthalic acid separation cylinder 63 and the cooling cylinder 64. The cooling cylinder 64 is fixed perpendicularly to the connecting pipe 47a, and the terephthalic acid separation cylinder 61A is detachably fixed to the connecting pipe 47a by a flange 66. The terephthalic acid separation cylinder 63 is a bottomed cylindrical member with numerous lateral holes 67 formed on its side. The decomposition gas G3 that has passed through the connecting pipe 47a is blown out from the lateral holes 67 into the space 65 between the terephthalic acid separation cylinder 63 and the cooling cylinder 64 while passing through the terephthalic acid separation cylinder 63.

[0043] The cooling cylinder 64 is equipped with an on / off valve V3 on the lower side of the terephthalic acid separation cylinder 63. The cooling cylinder 64 is also cooled in a cooling tank 68 through which cooling water W circulates. The decomposition gas G3 passes through the connecting pipe 47a, the terephthalic acid separation cylinder 63, and the lateral hole 67 before condensing in the cooling cylinder 64, and the resulting light oil KL (diesel fuel) is temporarily stored in the storage section 12A (see Figure 1) of the first oil storage tank 12. Since the decomposition gas G3 is cooled to 300°C, the sublimation temperature of terephthalic acid, the terephthalic acid contained in the decomposition gas G3 crystallizes in the terephthalic acid separation cylinder 63, and the crystallized terephthalic acid remains in the terephthalic acid separation cylinder 63 without passing through the lateral hole 67. The decomposition gas G3 from which terephthalic acid has been removed is cooled in the cooling cylinder 64 and condensed in the first oil storage tank 12.

[0044] As previously described, the terephthalic acid removal unit 49 has two sets of terephthalic acid condensing cylinders 61A and 61B, configured to be used alternately. This will be explained with reference to Figures 2(a) and 2(b). When operating the oil conversion device 1, first, the on-off valves V1 and V3 are opened, and on-off valve V2 is closed. Then, the decomposition gas G3 flows to the terephthalic acid condensing cylinder 61A side and is condensed, but eventually, crystallized terephthalic acid accumulates in the terephthalic acid condensing cylinder 61A, obstructing the flow of decomposition gas G3. Therefore, after opening on-off valve V2, on-off valve V1 is closed. Then, the decomposition gas G3 flows to the terephthalic acid condensing cylinder 61B side. Since no decomposition gas G3 is flowing to the terephthalic acid condensing cylinder 61A side, the terephthalic acid condensing cylinder 61A can be pulled out from the cooling cylinder 64 by removing the flange 66, and it can be reused by washing away the terephthalic acid crystals and attaching it to the connecting pipe 47a.

[0045] In other words, even while the oil conversion device 1 is in operation, either the terephthalic acid condensing cylinder 61A or 61B can be removed for cleaning or replacement. However, both on-off valves V1 and V2 may be opened, and after a predetermined time has elapsed, for example, on-off valve V1 may be closed to remove the terephthalic acid separation cylinder 63 of the terephthalic acid condensing cylinder 61A for cleaning, or vice versa. The lateral holes 67 may be circular, elliptical, oblong, or a combination thereof, with a diameter of approximately 2 mm to 5 mm, and can be set appropriately depending on the size of the terephthalic acid crystals. The number and arrangement of the lateral holes 67 can also be set as appropriate.

[0046] The oil conversion apparatus 1 introduces molten plastic P1, obtained by melting waste plastic P in the melting tank 10, into the first decomposition tank 11. In the first decomposition tank 11, the molten plastic P1 is heated and decomposed to generate pyrolysis gas G1, which is then recirculated back into the melting tank 10. The pyrolysis gas G1 generated in the first decomposition tank 11 is sent to the melting tank 10 at 400°C to 500°C and used as thermal energy for melting the waste plastic P0 in the melting tank 10. The waste plastic supply device 23 can also continuously supply waste plastic P0 to the melting tank 10 while heating and melting it. In the melting tank 10, the waste plastic P0 is melted by the thermal energy of the pyrolysis gas G1 generated in the first decomposition tank 11, the thermal energy of the molten plastic P1 including the waste plastic P0 introduced from the waste plastic supply device 23, and the thermal energy supplied to the melting tank 10 from the heating cylinder 14. As a result, the oil conversion apparatus 1 can increase its operating rate and reduce thermal energy consumption through continuous operation.

[0047] The first decomposition tank 11 can be supplied with heavy oil KH, such as heavy fuel oil, before the introduction of molten plastic P1 melted in the melting tank 10, or during the generation of pyrolysis gas G1. By supplying heavy oil KH to the first decomposition tank 11, thermal energy is not required to melt the waste plastic P0, and the generation of pyrolysis gas G1 can be quickly started from the molten plastic P1 and the heavy oil KH that has obtained thermal energy from the molten plastic P1. In other words, since pyrolysis gas G1 is generated by thermally decomposing liquid heavy oil KH and molten plastic P1 that is already at a high temperature, it is possible to reduce the amount of thermal energy consumed.

[0048] The waste plastic supply device 23 has a screw feeder 24 that sends waste plastic P0 to the melting tank 10, and the screw feeder 24 is heated by the pyrolysis gas G1 generated in the first decomposition tank 11. In other words, the waste plastic P0 in the screw feeder 24 can be melted by the thermal energy of the pyrolysis gas G1, making it possible to reduce the amount of heat energy consumed. Furthermore, the waste plastic supply device 23 can continuously feed waste plastic P0 into the melting tank 10 even when the oil conversion device 1 is in operation, making it possible to increase the operating rate.

[0049] The molten cylinder 13 itself is heated by the heating cylinder 14. However, the pyrolysis gas G1 generated in the first decomposition tank 11 heats the waste plastic P0 inside the molten cylinder 13 through the space 22 between the molten cylinder 13 and the heating cylinder 14, and further through the bottom plate 15. The waste plastic supply device 23 supplies the waste plastic P0, which contains molten plastic P1 heated and melted by the pyrolysis gas G1, to the molten tank 10. In this way, it is possible to melt the waste plastic P0 with low energy consumption.

[0050] Furthermore, the first decomposition tank 11 has a gas stirring blade 35. The gas stirring blade 35 blows the pyrolysis gas G1 generated in the first decomposition tank 11 onto the catalyst supported on the inner wall surface of the first decomposition tank 11. In the first decomposition tank 11, high-boiling-point gas components are generated because the molten plastic P1 is pyrolyzed at 400°C to 500°C. The catalyst decomposes the high-boiling-point gas components into low-boiling-point pyrolysis gas G1. Therefore, the first decomposition tank 11 can send the low-boiling-point pyrolysis gas G1 to the melting tank 10 while it is still at a high temperature.

[0051] The oil purifier 1 has a terephthalic acid removal unit 49 that introduces decomposition gas G3 cooled to the sublimation temperature of terephthalic acid (300°C) between the melting tank 10 and the first oil storage tank 12, crystallizes the terephthalic acid contained in the decomposition gas G3, and discharges it. The terephthalic acid removal unit 49 has at least two terephthalic acid separation cylinders 63 that are independently detachable from the connecting pipe 47 through which the decomposition gas G3 is sent. The terephthalic acid separation cylinders 63 cool the decomposition gas G3 passing through them, crystallizing and accumulating terephthalic acid. Since the terephthalic acid separation cylinders 63 can be removed one by one, one of the terephthalic acid separation cylinders 63 that has accumulated terephthalic acid crystals can be removed and cleaned while the other is left in place. This configuration allows the oil purifier 1 to continue operating and increases its operating rate.

[0052] The oil conversion apparatus 1 has a water seal tank 57 downstream of the second oil storage tank 19 into which separation gas G5 that does not liquefy in the second oil storage tank 19 is introduced. The water seal tank 57 is connected to a neutralization tank 59 that circulates a caustic soda aqueous solution as a neutralizing liquid Q. Separation gas G5 may contain plastics that contain chlorine components in waste plastics P0. Therefore, the oil conversion apparatus 1 is configured to introduce separation gas G5 into the water seal tank 57, neutralize the chlorine components with the caustic soda aqueous solution, and then discharge it. The water seal tank 57 has the original function of making the pressure in the system leading to the melting tank 10, the first decomposition tank 11, and the second decomposition tank 45 positive pressure and preventing oxygen from entering this system, and it is also possible to neutralize the chlorine components contained in separation gas G5.

[0053] The oil conversion apparatus 1 can be fitted with a second decomposition tank 45 that heat-decomposes the molten plastic P1 that overflows from the first decomposition tank 11 to generate pyrolysis gas G1. The second decomposition tank 45 has almost the same configuration as the first decomposition tank 11, and heat-decomposes the molten plastic P1 at 400°C to 500°C to generate pyrolysis gas G1, which is cooled in a cooler 48 and merges with the decomposition gas G3 sent from the melting tank 10 via a connecting pipe 47. Alternatively, the pyrolysis gas G1 generated in the second decomposition tank 45 can be introduced into the melting tank 10 or the first decomposition tank 11, thereby reducing the heat energy consumption of the melting tank 10 and the first decomposition tank 11. In addition, heavy oil KH can be introduced from the catalyst inlet 46 in the second decomposition tank 45 to promote the generation of pyrolysis gas G1.

[0054] Although the oil conversion apparatus 1 has been described using examples where it consists of one melting tank 10 and one first decomposition tank 11, or one melting tank 10, one first decomposition tank 11, and one second decomposition tank 45, it is possible to configure it with multiple units. Although not shown in the figures, for example, it is possible to have two melting tanks 10 equipped with a waste plastic supply device 23, and to place the first decomposition tank 11 between the two melting tanks 10. In such a configuration, molten plastic P1 and pyrolysis gas G1 are circulated between the two melting tanks 10 and the first decomposition tank 11. With such a configuration, it is possible to continuously convert a large amount of waste plastic P0 into oil. In such a configuration, it is preferable that the capacity of the first decomposition tank 11 be sufficient to accommodate the two melting tanks 10. [Explanation of Symbols]

[0055] 1... Oil conversion device (waste plastic oil conversion device), 10... Melting tank, 11... First decomposition tank, 12... First oil storage tank, 12A, 12B... Storage section, 13... Melting cylinder, 14... Heating cylinder, 15... Bottom plate, 18, 30, 38, 39, 47, 47a, 47b, 55, 56... Connecting pipes, 19... Second oil storage tank, 20, 34... Stirring blades, 23... Waste plastic supply device, 24... Screw feeder, 32... Heavy oil inlet, 33, 34... Agitator, 35... Gas stirring blades, 40... Insulation material, 42... Temperature controller, 45... Second decomposition tank, 47, 47a, 47b... Connecting pipes, 48, 53 ...Cooler, 49...Terephthalic acid removal section, 57...Water seal tank, 58...Discharge pipe, 59...Neutralization tank, 60...Exhaust gas treatment device, 61A, 61B...Terephthalic acid condenser, 62, 67...Side hole, 63...Terephthalic acid separation cylinder, 64...Cooler cylinder, 65...Space, G1...Pyrolysis gas, G2, G3...Decomposition gas, G4, G5, G6...Separated gas, GE...Exhaust gas, KH...Heavy oil, KL...Light oil, KL0...Light oil (gasoline), P0...Waste plastic, P1...Molten plastic, Q...Neutralizing liquid, V1, V2, V3...On / off valve, W...Cooling water

Claims

1. A melting tank for heating and melting waste plastic, A waste plastic supply device capable of continuously feeding the aforementioned waste plastic into the melting tank while heating and melting it, A first decomposition tank that introduces molten plastic from the melting tank to generate a pyrolysis gas and introduces the pyrolysis gas into the melting tank, A waste plastic liquefaction apparatus having a storage tank for storing the generated oil obtained by condensing the pyrolysis gas after heat exchange with the waste plastic in the melting tank, The aforementioned waste plastic supply device has a screw feeder, The first decomposition tank is connected to the melting tank by a connecting pipe through which the screw feeder is inserted. The connecting pipe is configured to allow the pyrolysis gas generated in the first decomposition tank to flow around the screw feeder. A waste plastic oil conversion apparatus characterized by the following features.

2. A melting tank for heating and melting waste plastic, A waste plastic supply device capable of continuously feeding the aforementioned waste plastic into the melting tank while heating and melting it, A first decomposition tank that introduces molten plastic from the melting tank to generate a pyrolysis gas and introduces the pyrolysis gas into the melting tank, A waste plastic liquefaction apparatus having a storage tank for storing the generated oil obtained by condensing the pyrolysis gas after heat exchange with the waste plastic in the melting tank, The melting tank comprises a melting cylinder for containing the waste plastic, a heating cylinder positioned with a space between it and the outer circumference of the melting cylinder for heating the melting cylinder, and a bottom plate that divides the melting cylinder into a region for melting the waste plastic and a region for the molten plastic to flow, and has a number of small holes through which the molten plastic and the pyrolysis gas can pass. The melting tank is configured to be heated by the pyrolysis gas sent from the first decomposition tank passing through the space and the bottom plate, the heated and molten waste plastic supplied by the waste plastic supply device, and the thermal energy supplied from the heating cylinder. A waste plastic oil conversion apparatus characterized by the following features.

3. In the waste plastic oil conversion apparatus according to claim 1 or 2, The first decomposition tank has a heavy oil supply port that allows for the supply of heavy oil before the introduction of the molten plastic or during the generation of the pyrolysis gas. A waste plastic oil conversion apparatus characterized by the following features.

4. In the waste plastic oil conversion apparatus according to claim 1 or 2, A catalyst is supported on the inner wall surface of the first decomposition tank. The vessel further comprises a gas agitator that rotates along the inner wall surface and blows the decomposition gas generated in the first decomposition tank onto the catalyst. A waste plastic oil conversion device characterized by the following.

5. In the waste plastic oil conversion apparatus according to claim 1 or 2, The system further includes a terephthalic acid removal section between the melting tank and the oil storage tank, which is capable of introducing decomposition gas cooled to the sublimation temperature of terephthalic acid, thereby crystallizing and discharging the terephthalic acid. The terephthalic acid removal unit has at least two detachable terephthalic acid separation cylinders. A waste plastic oil conversion apparatus characterized by the following features.

6. In the waste plastic oil conversion apparatus according to claim 1 or 2, The downstream side of the oil storage tank further includes a water seal tank into which separated gas that does not liquefy in the oil storage tank is introduced. The water seal tank is connected to a neutralization tank through which a neutralizing solution circulates to neutralize the chlorine component of the separated gas. A waste plastic oil conversion apparatus characterized by the following features.

7. In the waste plastic oil conversion apparatus according to claim 1 or 2, The system further includes a second decomposition tank into which the molten plastic overflowing from the first decomposition tank is introduced to generate the pyrolysis gas, The pyrolysis gas generated in the second decomposition tank is connected in such a way that it can be combined with the pyrolysis gas sent from the melting tank, or it is connected to the melting tank via the waste plastic supply device. A waste plastic oil conversion apparatus characterized by the following features.

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