JPH1088148A - System for conversion of waste plastic into oil and system for conversion into oil and power generation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light oil useful as a fuel for diesel power generation, etc., by converting a waste plastic into an oil. SOLUTION: This system for conversion of a plastic into an oil comprises a pyrolytic vessel 1 for the waste plastic, gas-solid and liquid separators 2 and 12 for separating dust and a condensed heavy component in a pyrolyzed gas, a cooler 3 for condensing and liquefying the pyrolyzed gas, a reflux vessel 4 for separating a condensed heavy component and an uncondensed light component therefrom, a chlorine fixing vessel 5 for removing a chlorine component, a condenser 6 for condensing and liquefying the pyrolyzed light gas and converting the pyrolyzed light gas into the oil, a gas-liquid separator 7 for separating the uncondensed gas from the condensed and liquefied oil, a light oil storage tank 9, etc. The pyrolyzed oil of the waste plastic can be used as a fuel for a diesel engine to enable clean power generation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste plastic liquefaction system for recovering useful oil as a diesel power generation fuel from waste plastic.

[0002]

2. Description of the Related Art Recycling of garbage due to deterioration of the market of recycled products due to economic development, a large amount of copy paper discharge due to office automation in offices, and changes in lifestyle due to changes in lifestyle. Coarse waste such as goods is increasing year by year. In addition, with the increase in plastic production, the amount of waste is increasing year by year, and has become a social problem. Currently, most waste plastics are disposed of by landfill and incineration. However, there is a problem of shortage of landfill sites, and in the case of incineration, there is a problem of shortening the life of the incinerator and environmental pollution by exhaust gas. In order to solve these problems, methods of recycling waste plastics and recovering energy have been studied.

[0003] As one of the recycling methods for combustibles, especially plastics, there is a method in which waste plastics are thermally decomposed into oil. Melting and processing of thermoplastics
JP-A-49-17477 and JP-A-59-174689 disclose methods of converting oil into a fuel by thermal decomposition and recovering it. However, simply thermal decomposition of waste plastics results in a large amount of heavy components such as high molecular weight fractions and wax-like substances in the product oil, and a wide range of boiling points from light to heavy components such as gasoline. Due to the presence of the oil component, a fuel oil having difficulty in fluidity and ignitability is recovered as a fuel oil for diesel power generation or the like as compared with a commercially available fuel oil. JP-A-2-29492, JP-A-3-200892, and JP-A-2-29492 disclose a method of catalytically cracking heavy components such as high molecular weight fractions and wax-like substances in the thermally cracked oil to catalytically crack the resulting oil. No. 3-287694, and the like.

[0004]

Lightening waste plastic pyrolysis gas by catalytic cracking is effective as a means for recovering light oil, but gasification cracking is easily promoted and the amount of gas generated increases. There is a problem that the oil recovery rate is reduced. In this case, it would be advantageous in terms of energy if the generated gas is effectively used as a heating source during pyrolysis of waste plastic. As for the storability as a fuel, liquids are easier to store and transport. Therefore, it is desirable to suppress the gas generation rate as low as possible and to improve the recovery rate of oil suitable for fuel oil and the like. Further, in the case of the contact catalyst, there is a problem that carbon or the like precipitates on the catalyst with the lapse of time, the lightening characteristics are deteriorated, and it is necessary to regenerate and replace the catalyst, and maintenance is not easy. Furthermore, the recovered oil lightened by catalytic cracking contains a large amount of aromatic and olefinic hydrocarbons, which reduces the ignitability as a fuel and increases the concentration of hydrocarbons in flue gas. is there.

On the other hand, there is a problem that dust such as residue (carbide) is scattered and entrained in the pyrolysis gas, and this dust mixes with the recovered oil to lower the combustibility of diesel power generation or block the combustion nozzle. Further, if vinyl chloride is mixed in the waste plastic, the chlorine component is melted and contained in the recovered oil, and the harmful components from the exhaust gas such as the corrosion of engines such as diesel power generation and the combustion exhaust gas are discharged, resulting in human harm.

SUMMARY OF THE INVENTION An object of the present invention is to reduce the gas generation rate without using a catalyst to efficiently reflux and lighten heavy oil components to produce light oil useful for fuels such as diesel power generation and to improve the oil recovery rate. Plan. In addition, dust mixed into the pyrolysis gas is removed with high efficiency to improve the combustibility of diesel power generation or the like or prevent the combustion spray nozzle from being clogged. In addition, it prevented heavy components and dust from adhering to the chlorine fixing agent, improved the utilization of the chlorine fixing agent, efficiently removed the chlorine component in the pyrolysis gas, and reduced the chlorine content in the oil. The purpose is to recover high quality fuel oil.

[0007]

According to the present invention, dust and condensed heavy components scattered in a pyrolysis gas are separated by a first gas-solid separator, a reflux tank and a second gas-solid separator. The dust and the heavy component to be condensed and liquefied are retained in the first, second and third solid-liquid retaining tanks, and are returned to the thermal decomposition tank while being retained. Further, after the pyrolysis gas from the first gas-solid liquid separator is cooled to a predetermined temperature to condense and liquefy the heavy component, the liquefied heavy component and the uncondensed gas are separated by a reflux tank and refluxed. The liquefied heavy component is refluxed from the tank to the thermal decomposition tank to repeatedly promote thermal decomposition. By this operation, lightening of heavy oil is promoted, light oil useful for fuel is recovered, and the recovery rate of oil suitable for fuel oil is improved. In addition, the dust in the pyrolysis gas is returned to the reflux tank in order to reduce the mixing ratio of dust in the recovered oil and prevent the heavy components and dust from adhering to the chlorine fixing agent. The utilization rate is improved, and the uncondensed light gas components from the reflux tank are passed through a chlorine fixing tank to efficiently remove the chlorine components, thereby suppressing corrosiveness and reducing the emission of harmful components. Also,
The light gas component from which the chlorine component has been removed is condensed and liquefied by passing it through a chlorine immobilization tank to collect the light oil component, and to collect useful oil as a fuel by means of a condenser that condenses oil having a different boiling point.

According to the present invention, the dust scattered along with the pyrolysis gas and the heavy component condensed and liquefied are sequentially separated by the first and second gas-solid-liquid separators or the reflux tank.
And the second gas-solid-liquid separator, the dust and the liquefied heavy component separated in the reflux tank are sequentially returned to the thermal decomposition tank while being retained in the first, second, and third solid-liquid retention tanks. Dust can be removed with high efficiency and dust can be prevented from being mixed into the recovered oil. A heavy component is condensed and liquefied at a predetermined temperature by a cooler that cools the pyrolysis gas from the first gas-solid liquid separator,
Further, since the liquefied heavy component and the uncondensed light gas component are separated by the reflux tank and the liquefied heavy component from the reflux tank is repeatedly returned to the pyrolysis tank, the light component of the heavy component can be used without using a catalyst. And the recovery rate of oil can be improved. Further, since the heavy components and the dust are returned to the pyrolysis tank in the preceding stage of the chlorine fixing tank, the adhesion of the heavy components and the dust to the chlorine fixing agent can be prevented, and the utilization rate of the chlorine fixing agent can be improved. Thereby, since the chlorine component in the uncondensed gas from the second gas-solid liquid separator can be efficiently removed by the chlorine fixing tank, the corrosiveness can be suppressed and the emission of harmful chlorine component exhaust gas can be reduced. . Cooling the uncondensed light gas component after chlorine removal to light oil,
Since the oils having different boiling points are fractionally recovered from the lightened oil, useful oils such as fuel can be recovered.

On the other hand, since the recovered light oil is used as a fuel for a diesel engine connected to a generator, it is possible to suppress corrosion and reduce the emission of harmful chlorine components in the combustion exhaust gas, thereby achieving clean power generation.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a schematic diagram showing the basic configuration of a waste plastic oil-based power generation system according to the present invention. An embodiment according to FIG. 1 will be described. This system is composed of pyrolysis tank 1, first and second
Gas-solid-liquid separators 2, 12, cooler 3, reflux tank 4, chlorine immobilization 5, condenser 6, gas-liquid separator 7, combustor 8, oil storage tank 9, first, second and first 3 solid-liquid retention tanks 10, 11, 1
3, washing tower 14, compressor 15, uncondensed gas storage tank 16,
Oil pumps 17, 18, gas suction pump 19, suction blower 22, diesel generator 20, exhaust gas treatment device 2
1, a controller 23, valves 500 to 508, 514, regulating valves 509 to 513, 515 and the like.

First, the operation will be described. In FIG. 1, waste plastic is supplied to a pyrolysis tank 1. The waste plastic is gasified and decomposed by heating the pyrolysis tank 1 by gas burner combustion (not shown) using fuel from the uncondensed gas storage tank 16 or the oil storage tank 9. The cracked gas is introduced into the gas-solid separator 2 through the pipe 700,
The gas component is separated from the dust that is entrained in the cracked gas and the heavy component that condenses and liquefies part of the cracked gas.
Here, the separated dust and a part of the liquefied heavy component are retained in the first retention tank 10 via the pipe 702, and thereafter the valve 5
The mixture is refluxed to the pyrolysis tank 1 through the fuel cell 00. First detention tank 1
In the case of 0, everything is transferred from the first retention tank 10 to the pyrolysis tank 1
Some of the dust and liquefied heavy components are refluxed to the thermal decomposition tank 1 while staying at a certain level without being refluxed. The uncondensed decomposition gas from the gas-solid liquid separator 2 is introduced into the cooler 3 through the pipe 701, cooled to an arbitrary predetermined temperature by the cooling water 200, and the heavy components are condensed and liquefied, and then introduced into the reflux tank 4. Is done. The heavy component condensed in the reflux tank 4 is separated from the gas of the uncondensed light gas component together with the dust that cannot be removed in the previous stage, and the dust and the liquefied heavy component are retained in the second retention tank 11 via the pipe 705. Then, it is returned to the pyrolysis tank 1 via the valve 501.
In the second retention tank 11 as well as in the first retention tank 10, all of the dust and liquefied heavy components are retained at a certain level without being entirely refluxed from the second retention tank 11 to the pyrolysis tank. The heat is returned to the thermal decomposition tank 1. The light gas component is maintained at a constant temperature in the reflux tank 4,
In addition, while the mist in the light gas component is being removed, the dust that is introduced from the reflux tank 4 through the pipe 704 to the second gas-solid-liquid separator 12 and is not removed in the preceding stage and the heavy component that is condensed and liquefied are not yet removed. It is separated into condensed light gas components. The reflux tank 4 is appropriately filled with alumina balls and the like. The separated dust and liquefied heavy component are retained in the third retention tank 13 and then returned to the thermal decomposition tank 1 via the valve 506. In the third retention tank 13 as well, all the components are stored in the third retention tank 1.
From 3, some dust and liquefied heavy components are refluxed to the thermal decomposition tank 1 while staying at a certain level without returning to the thermal decomposition tank. The uncondensed light gas component from the second gas-solid liquid separator 12 is introduced into the chlorine fixing tank 5 through the valve 503. Valve 504 is in a closed state. The chlorine immobilization tank 5 is filled with calcium hydroxide (Ca (OH) ₂ ) as a chlorine immobilizing agent, and has the same temperature as that of the reflux tank 4 or the utilization rate of the chlorine immobilizing agent due to mist oil adhesion. It is heated to a temperature higher by 5 to 10 ° C. to prevent the drop. The chlorine component contained in the light gas component from the reflux tank 4 is fixed and removed in the chlorine fixing tank 5 and then introduced into the condenser 6 through the valve 505 and the pipe 706. The light gas component is cooled in the condenser 6 by the cooling means 2.
01, condensed and liquefied oil. The liquefied oil is introduced into the gas-liquid separator 7 via the pipe 707, and is separated into liquefied oil and uncondensed gas. The separated liquefied oil is supplied to pipe 7
08 and is collected in the oil storage tank 9 via the valve 502.
The uncondensed gas is introduced into the combustor 8 by the suction blower 22 via the valve 508 and the regulating valve 510, and the exhaust gas 300 after combustion is processed and discharged out of the system. The valve 507 is in a closed state. Alternatively, the compressed gas is collected by the compressor 15 into the non-condensed gas storage tank 16 while the valve 508 and the control valve 510 are closed and the valve 507 is opened. The uncondensed gas storage tank 16 is provided with a hot water pipe so that the condensed components are stored in a gaseous state. In the condenser 6, the condenser 6
Cooling means 20 such as hot water, air and cooling water while passing through
The liquid 1 is cooled and condensed, and liquefied oils having different boiling points are collected. In this case, the oil is collected by another oil receiving tank (not shown). Heating of the decomposition tank 1 is performed by burning a gas burner (not shown) from the uncondensed gas storage tank 16 through a regulating valve 512 by a gas suction pump 19. Alternatively, a part of the recovered oil is supplied from the oil storage tank 9 by the oil feed pump 17 and heated by the oil combustion burner. Components that are not decomposed and gasified in the pyrolysis tank 1 are taken out of the system as residues (carbides) 100 and disposed of. The liquefied heavy components refluxed to the pyrolysis tank 1 are almost recovered as oil by promoting lightening, but the liquefied heavy components remaining in the reflux tank 1 still have a high boiling point and cannot be easily lightened. Since it is a heavy component, it is cooled and collected by the condenser 6 without passing through the chlorine immobilization tank 5 by closing the valves 503 and 505 and opening the valve 504. This operation is performed in order to prevent a reduction in the utilization factor due to the attachment of heavy oil to the fixing agent filled in the chlorine fixing tank 5. On the other hand, in diesel power generation, the fuel oil
Is introduced into the fuel tank by the oil feed pump 18 via the valve 514, and is generated to generate electric power 800. The electric power 700 is used as power for a motor, pumps, and the like in the station. Further, the exhaust gas from the diesel generator 20 may be used as a heating source for the pyrolysis tank 1.

Next, the operation of the control system will be described. As for the heating temperature of the waste plastic put into the pyrolysis tank 1, the temperature of the exhaust gas is detected by a temperature detector 600 provided in the exhaust gas line 301. The detected temperature information is transmitted to the controller 2
The control valve 512 or 513 provided in the fuel supply line of the uncondensed gas storage tank 16 or the oil storage tank 9 is adjusted by the output signal from the control unit 3 so that the heating temperature of the pyrolysis tank 1 becomes constant. The fuel supply amount is controlled.
The gas is stored in the uncondensed gas storage tank 16 by a pressure detector 60.
It is monitored by 3 that the pressure does not exceed a predetermined pressure. When the pressure reaches the predetermined pressure, the compressor 15 is stopped and the supply of the uncondensed gas is stopped. The inside of the system is always a suction blower 2
2, the pressure in the pyrolysis tank 1 is detected by the pressure detector 602, and the control valve 510 is adjusted by the controller 23 to minimize the fluctuation range of the pressure in the pyrolysis tank 1. Is controlled so that The cooling of the decomposed gas in the cooler 3 is adjusted by a temperature detector 601 and a control valve 509 provided in the pipe 703. The temperature of the decomposed gas at the outlet of the cooler 3 set to an arbitrary temperature is detected by the temperature detector 601, and upon receiving this signal, the control valve 509 is adjusted by the controller 23 to control the amount of cooling water of the cooler 3. .
The pipes 700 to 706, the first and second gas / solid-liquid separators 2, 12, the reflux tank 4, the chlorine fixing tank 5, the first and second
The third solid-liquid stagnation tanks 10, 11, 13 are provided with heaters for heating and adjusting (not shown).

On the other hand, in the diesel power generation using the oil recovered by the waste plastic oiling process as fuel, the fuel oil recovered by the above operation is introduced into the fuel tank from the oil storage tank 9 via the valve 514 by the oil pump 18. Then, power is generated and electric power 800 is obtained. During this time, when the oil is fed into the fuel tank, the fuel consumption is detected by the level detector 615 provided in the fuel tank, and the control valve 514 is adjusted by the controller 23 so that the fuel oil is maintained at a predetermined level. Supplied and supplied.

Experimental Example 1 An experimental example using the waste plastic oiling system of FIG. 1 will be described. As a raw material for waste plastic, polypropylene 1
3.5 kg, polyethylene 6.6 kg, polystyrene 2.1 k
g, polyvinyl chloride 0.3kg, epoxy resin 5.4kg,
A mixture of 2.1 kg of a phenol resin was used. After crushing these raw materials to about 5 mm, they were put into the pyrolysis tank 1 and 150 kg were continuously processed by the above operation. The heating temperature of the waste plastic in the pyrolysis tank 1 is 420 to 430
° C, the temperature of the reflux tank 4 is 280 ° C, and the temperature of the chlorine fixing tank 5 is 290.
C. was maintained.

As a result, the yield of oil, uncondensed gas, and residue was 6% with respect to the weight of the input waste plastic.
It was 7.2 wt%, 17.7 wt%, and 15.1 wt%. The recovered oil was analyzed for hydrocarbon components using a gas chromatograph mass spectrometer. Each component was classified into paraffin, naphthene, olefin, and aromatic, and the proportion was 45% for aromatic, 36% for olefin, and 19% for paraffin.

Comparative Example 1 The chlorine content in the recovered oil of Experimental Example 1 was determined by ion chromatography to be 30 ppm or less. 1st, 2nd
In the case where the pyrolysis gas is cooled to 290 ° C. and then supplied directly to the chlorine fixing tank, regardless of the equipment configuration for returning heavy components and dust to the pyrolysis tank by the third solid-liquid storage tank and the reflux tank, Heavy components and dust adhered to the entire surface of the immobilizing agent, and the concentration of chlorine in the recovered oil was 1600 ppm.
From this, it can be seen that the equipment configuration of FIG. 1 can prevent heavy components and dust from adhering to the chlorine fixing agent, and improve the utilization rate of the fixing agent.

Comparative Example 2 As a comparative example, without using the reflux tank 4, the cracked gas generated by the thermal decomposition was directly introduced into the catalyst tank to reduce the weight. The gas component from the catalyst tank was cooled by the condenser 6 and recovered as condensed liquefied oil. The waste plastic raw material, the thermal decomposition method, and the conditions are the same as in Experimental Example 1 of the present invention. The catalyst is a zeolite-based ZSM-
5 was used which carried 5 wt% of Sn. The recovered oil was examined using a gas chromatograph mass spectrometer in the same manner as described above, and as a result, 89% was aromatic. The yields of oil, uncondensed gas, and residue were 59 wt%, 25.9 wt%, and 15.1 wt%, respectively, based on the weight of the input waste plastic.
wt%.

According to the present invention, since the amount of aromatic hydrocarbons is small according to the present invention as compared with the properties of the oil recovered by the catalytic contact method, oil having high ignitability and low hydrocarbon exhaust gas concentration during combustion is recovered. it can. In particular, knocking can be prevented when used in a diesel engine. In addition, it can be seen that the generation of gas is reduced and the oil yield can be improved.

Comparative Example 3 The dust in the oil recovered in Experimental Example 1 was examined by a filtration method and found to be 1.3% by weight based on the weight of the recovered oil. For comparison, here, the first, second, and third solid-liquid retention tanks 10,
The waste plastic was pyrolyzed to oil without using the eleventh, thirteenth, first and second gas / solid-liquid separation tanks 2,12. Waste plastic raw materials, pyrolysis method and conditions are the same as in the experimental example.

As a result of examining the dust in the collected oil by a filtration method, it was found to be 8.9% by weight based on the weight of the recovered oil. From this, it can be seen that the amount of dust mixed into the recovered oil can be reduced by the system of FIG.

Comparative Example 4 The chlorine content in the recovered oil of Experimental Example 1 was determined by ion chromatography to be 30 ppm or less. For comparison, here, the pyrolysis gas is not passed through the chlorine immobilization tank 5, the valves 503 and 505 are closed, the valve 504 is opened, and the decomposition gas is directly introduced into the condenser 6, where the liquefied oil is cooled and condensed. Collected. As a result of examining the chlorine content in the recovered oil by exhaust gas using a cylinder combustion method by ion chromatography, 850 pp
m. It can be seen that the system of FIG. 1 removes chlorine components contained in vinyl chloride and the like mixed in the raw material waste plastic.

Experimental Example 2 Next, diesel power generation using the oil recovered in Experimental Example 1 was performed. The diesel generator 20 used had a power output of 6 kW. Electric power 700 was collected by installing a heater with a load of 4 kW in water. Power generation was performed for about 2 hours.

As a result, the above operation made it possible to smoothly supply the oil from the oil storage tank 9 to the diesel generator 20, to continuously burn the oil, and to recover the electric power. Also, no blockage of the engine due to dust was observed. Further, a part of the exhaust gas is put into a gas washing bottle of a 0.04% aqueous solution of caustic soda, introduced at a flow rate of 2 liters / min and introduced and collected.
The chlorine component concentration was examined by ion chromatography.
As a result, the chlorine component concentration in the exhaust gas was 6.2 ppm when the chlorine component was fixed and removed, and 130 ppm when the chlorine component was not removed.
It can be seen that the use of the oil of Experimental Example 1 can reduce the emission of harmful chlorine component exhaust gas, thus enabling clean combustion power generation.

[0025]

According to the present invention, the cracked gas is cooled to an arbitrary predetermined temperature to condense and liquefy heavy components, and is refluxed from the reflux tank to the pyrolysis tank to promote lightening. This has the effect of improving the recovery rate. As a result, there is an effect that there is no need to perform maintenance such as replacement of the catalyst due to a decrease in the activity of the catalyst, and it is possible to prevent a decrease in the oil recovery rate due to an increase in the rate of gasification at the time of lightening. In addition, since heavy components and dust in the decomposition gas of waste plastic are sequentially returned to the pyrolysis tank, it is possible to prevent heavy components and dust from adhering to the chlorine fixing agent and improve the utilization rate of the chlorine fixing agent. There is an effect that can be achieved. As a result, dust and chlorine components can be prevented from being mixed into the recovered oil, and by using the obtained light oil as a fuel for a diesel engine, it is possible to suppress corrosion and discharge harmful chlorine components in the combustion exhaust gas. This has the effect of reducing power consumption and producing clean power.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a waste plastic oil-based power generation system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pyrolysis tank, 2 ... 1st gas-solid-liquid separator, 3 ... Cooler,
4 ... reflux tank, 5 ... chlorine immobilization, 6 ... condenser, 7 ... gas-liquid separator, 8 ... combustor, 9 ... oil storage tank, 10 ... first solid-liquid retention tank, 11 ... second solid-liquid retention Tank, 12: second gas / solid-liquid separator, 13: third solid-liquid storage tank, 14: washing tower, 15: compressor, 16: uncondensed gas storage tank, 17, 18: oil feed pump, 19 ... Gas suction pump, 20 ... Seesel generator,
21: exhaust gas treatment device, 22: suction blower, 23: controller, 500 to 508, 514: valve, 509 to 513 ...
tuning valve.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Norio Arashi 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Research Laboratory, Ltd. (72) Inventor Hisao Yamashita 7-1 Omikacho, Hitachi City, Ibaraki Prefecture No. 1 Inside Hitachi, Ltd.Hitachi Research Laboratory (72) Inventor Shigeru Azuhata 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Laboratory (72) Inventor Tomoyuki Saito Kanda, Chiyoda-ku, Tokyo 4-6, Surugadai Inside Hitachi, Ltd. (72) Inventor Masayoshi Kokubo 2-9-18 Misaki-cho, Chiyoda-ku, Tokyo Inside Hitachi System Technology Co., Ltd.

Claims (5)

[Claims] 1. A pyrolysis tank for converting waste plastic into a pyrolysis gas under heating, separating the obtained pyrolysis gas into a heavy component and a light component, and returning the heavy component to the pyrolysis tank. A reflux tank, a chlorine fixing tank for removing chlorine components in the separated light components, a condenser for cooling and condensing and liquefying the light components after chlorine removal stepwise to obtain oils having different boiling points, An oil liquefaction system for waste plastic, comprising: a gas-liquid separator for separating uncondensed gas that is not liquefied in a condenser; and an oil storage tank for storing light oil from the gas-liquid separator. 2. The method according to claim 1, wherein dust accompanying the pyrolysis gas obtained in the pyrolysis tank and heavy components condensed and liquefied while the pyrolysis gas is sent to the reflux tank are separated. An oil recycling system for waste plastics, comprising a means for refluxing a pyrolysis tank. 3. The waste plastics liquefaction system according to claim 1, further comprising means for adjusting the temperature of the pyrolysis gas introduced into the reflux tank. 4. The gas-liquid separation device according to claim 1, wherein a part of the light gas component from the reflux tank is directly supplied to the condenser by bypassing the chlorine fixing tank. A gas storage tank with a heating function for storing uncondensed gas from the vessel, and means for transporting the oil in the oil storage tank and the gas in the gas storage tank as a heat source for gasifying and cracking waste plastic in the pyrolysis tank. An oil recycling system for waste plastic, comprising: 5. An internal combustion engine using liquefied oil from the oil storage tank as a fuel in the waste plastic liquefaction system according to any one of claims 1 to 4, a power generation device associated with the internal combustion engine, and the power generation A waste plastic oil power generation system, comprising: an exhaust gas treatment device for treating combustion exhaust gas of the device.