JP2002212571A - Method for thermal cracking of waste plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal cracking method to convert a mixed waste plastic smeared with stain into a high-quality oil in high efficiency without increasing the cost. SOLUTION: Expanded polystyrene is subjected to volume reducing treatment in a volume-reducing, washing and dehydrating machine 10 using water W1 and a thermally cracked light or medium oil of polyethylene or polypropylene heated at about 60 deg.C with a heater 12 or a paraffin-rich mineral oil, the crushed pieces P of the mixed waste plastic are washed to transfer the salt component in the stain into water and waste plastic suitable for oil conversion is recovered from the crushed pieces of the waste plastic by using a gravity selection liquid 17 having a specific gravity of 1.05-1.06. The recovered waste plastic and optionally a waste lubricating oil is thermally cracked in two stages. The waste plastic and the waste lubricating oil are thermally cracked to improve the quality of the thermally cracked oil and the medium to heavy oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for thermally decomposing waste plastics, and more particularly to a method for efficiently and highly oily mixed dirt-containing waste plastics without increasing costs in the future. .

[0002]

2. Description of the Related Art When converting mixed waste plastic containing vinyl chloride to oil, pretreatment including crushing and foreign matter separation, melting,
The treatment is carried out through the steps of dehydrochlorination, thermal decomposition and reforming distillation, and these are generally treated continuously. The heat required for such melting, dehydrochlorination and thermal decomposition has been supplied by the following method. 1. Heat required for melting and dehydrochlorination is provided by an extruder and a heating medium heating unit, by introducing a heating medium oil and by indirect heating. 2. The heat required for melting and pyrolysis is supplied by directly heating the outer wall of the vessel with an electric heater or combustion gas. 3. The heat required for pyrolysis is obtained by extracting a certain amount of residual oil from the pyrolysis tank from the pyrolysis tank with a pump, circulating it through the heating section to the pyrolysis tank, and providing the heating section with the heat required for pyrolysis. Supply. 4. Heat is supplied by heating a fraction containing the pyrolysis oil at a high temperature in a heating furnace and directly blowing it into a pyrolysis tank.

[0003] When pyrolysis of mixed waste plastics, the rate of thermal decomposition of each plastic varies depending on the temperature. Particularly, vinyl chloride, polystyrene and polypropylene decompose at a lower temperature than polyethylene. In order to increase the processing speed, the processing temperature is set to a temperature corresponding to the thermal decomposition rate of polyethylene, which takes the longest time to decompose.

[0004]

However, the conventional waste plastic pyrolysis method has the following problems. 1. In the method of heating with a heat transfer oil, the limit temperature of a commercially available heat transfer oil is as low as about 300 ° C., which can be used only for melting waste plastic, while the temperature of dehydrochlorination is 300 ° C.
C to 320 ° C., and the temperature difference ΔT is small. Therefore, heating cannot be performed efficiently. When the temperature of the heat transfer oil is raised to a temperature equal to or higher than the limit temperature, thermal deterioration is caused and the life is shortened. In particular, mixed waste plastics often contain polystyrene resin, and the polystyrene resin is partially decomposed during the dehydrochlorination treatment, and light oil distills out with hydrogen chloride. Contains many organic chlorine compounds and does not become a product. 2. In the method of heating by circulating the pyrolysis residual oil, coking in the pipe occurs. 3. When heat is supplied only by heating the pyrolysis oil at a high temperature and blowing it into the tank, the heating furnace becomes large. 4. In a method in which the outer wall of the tank is directly heated by an electric heater or a high-temperature combustion gas, coking is easily generated on the inner wall of the tank. 5. In particular, if heat is kept in each tank or each device by a heat medium device or the like at the time of batch processing, the cost increases.

Furthermore, in the conventional waste plastic pyrolysis method, the pyrolysis temperature is set high in order to improve the processing speed. Particularly, when pyrolysis of mixed waste plastic, the pyrolysis temperature and reaction temperature of polyethylene which is the least decomposable. Because the time is set, plastics that are easier to decompose than polyethylene decompose and vaporize early, and the generated residue is exposed to a high-temperature atmosphere within the polyethylene reaction time, so it is transformed into asphalt, pitch, and even coke. Would.

[0006] Further, in the conventional waste plastic pyrolysis method, there is the following problem when the mixed waste plastic containing vinyl chloride is continuously liquefied. 1. Since the dehydrochlorination treatment is performed continuously in an extruder,
Pretreatment equipment such as crushing, sorting, and drying increases costs. 2. Since the raw material is waste, clogging is likely to occur in equipment, piping, and the like. In the continuous method, it is difficult to cope with the occurrence of the blockage, and the number of devices is increased to complicate the operation. 3. Since dehydrochlorination is performed continuously, a short path is likely to occur, and the dehydrochlorination rate is not stable, resulting in an adverse effect on product properties.

[0007] On the other hand, the present inventor has found that waste plastics containing vinyl chloride are melted and dehydrochlorinated in batches in a pyrolysis tank and then thermally decomposed to convert the waste plastics into oil. Mild pyrolysis of waste plastic is performed at a low temperature within the temperature range where waste plastic can be thermally decomposed in the tank, and half of waste plastic is turned into oil. The oil is left in the pyrolysis tank, and the remaining heat of the semi-pyrolyzed oil supplies the heat necessary for melting and dehydrochlorinating the next waste plastic, while the residue of the mild pyrolysis is converted to the pyrolysis tank. Extracted from waste plastics, hard residue pyrolysis is performed at a high temperature within the temperature range where waste plastic can be thermally decomposed, the residue is turned into oil, and melting, dehydrochlorination, and thermal decomposition are performed batchwise. Waste plastics containing vinyl chloride efficiently, yet developed a thermal decomposition method of waste plastics to allow Yuka high quality has led to the application (1999 Patent Application No. 232,106).

By the way, in carrying out the above-mentioned thermal decomposition method, it is necessary to crush the mixed waste plastics and separate them by type as a pretreatment. Such separation work has been performed using various methods such as specific gravity, wind power, static electricity, X-rays, and near infrared rays. However, when separating plastics that are not suitable for oiling from mixed waste plastics having different forms, specific gravity of 1 is used. The mainstream was separation using water as a medium.

In addition, mixed waste plastics collected as household waste or industrial waste often have dirt attached thereto, and need to be cleaned before thermal decomposition. Such a washing operation sometimes used simply water, but sometimes used hot water or added a detergent or a neutralizing agent.

[0010] Furthermore, carbon residues are generated in the thermal decomposition reaction of organic substances. Therefore, in carrying out the above-mentioned pyrolysis method, it is important how to efficiently discharge carbon out of the system. A severe coke is formed, which results in inoperability. Therefore, as measures against pyrolysis coking, (1) a method using sand as a medium, (2) a catalyst fluidized bed method, (3) a method in which the residue is concentrated and discharged outside the system, and (4) a mechanical discharge Method, etc. are adopted.

Further, pyrolysis oil of waste plastic and waste lubricating oil contains a large amount of olefin and is very unstable, and when exposed to air, precipitates such as gum and tar are formed in a short time,
Moreover, the smell and color also worsen. In addition, waste plastics and waste lubricating oils contain a large amount of sulfur, nitrogen, and chlorine due to additives, etc., and when performing the above-mentioned pyrolysis method, in large-scale treatment, hydrogen is removed at high temperature and high pressure in the presence of a catalyst. By adding it, and on a small scale, activated clay is used.

Further, foamed polystyrene may be contained in the waste plastic in some cases. If such expanded polystyrene is washed as it is and the specific gravity is separated, the bulk specific gravity is very small, which is not preferable in terms of processing. Therefore, foamed polystyrene is converted to (1). Oil, (2). Gasification, (3). Heat (combustion gas, electric heat, frictional heat) or solvent (citrus such as limonene, special mineral oil), Pelletization has been carried out, but recently, a method of ingot formation or pelletization by heat is mainly used.

However, the above-described processing method has the following problems, and has been found to be a technical problem to be solved in implementing the above-described pyrolysis method. 1. When washing dirty mixed waste plastics, treatment with water or hot water is the mainstream, but a large amount of wastewater treatment is required. In particular, in the case of agricultural plastics, care must be taken because fertilizers and the like are attached. Also, the effect of cleaning the film with water is small.
Cleaning agents and neutralizers must be used. 2. Dirt is often caused by soy sauce, sauces, mayonnaise, etc., but they contain salt, and water used as a cleaning medium becomes salt water when used for a long time, salt adheres to plastic, and if the plastic is burned as it is There is a concern about the dioxin problem. In addition, the specific gravity of water increases, which adversely affects the cleaning ability. 3. The method of reducing the volume of expanded polystyrene by hot air requires a considerable amount of heat energy, and when plastics overlap, heat may not be distributed enough to reduce the volume. Conversely, if too much heat is applied, other plastics may be melted. 4. When performing specific gravity separation, the specific gravity of a general-purpose plastic is, for example, 0.90 for polypropylene and 0. 0 for low-density polyethylene.
92, medium-density polyethylene 0.94 to 0.96, polystyrene 1.05 to 1.06, ABS resin 1.03, polyvinyl chloride 1.22 to 1.38, PET resin 1.60
When water having a specific gravity of 1 is used as a medium for specific gravity separation, polystyrene, ABS resin, polyvinyl chloride, P
The ET resin will settle and other plastics will float, but it is undesirable for the polystyrene and ABS resins suitable for oiling to settle. 5. In order to efficiently and safely discharge the carbon generated during thermal decomposition out of the system, sand or catalyst is used as a medium, and fluidized beds and continuous regeneration equipment are adopted. It is difficult to adopt when constructing an oil conversion system. 6. In the method of mechanically discharging carbon, clogging and the like often occur, which is not preferable in terms of operation safety at high temperatures. 7. The main method of converting waste plastics and pyrolysis oil from waste lubricating oil into high-quality products is to carry out hydrogenation under high temperature and pressure under a catalyst. While it is difficult to adopt, the activated clay treatment improves the oxidation stability, but has no effect on removing nitrogen, chlorine, sulfur and the like. In particular, waste activated clay treatment is expensive and not economical.

The present invention has been made in view of the above-mentioned circumstances, and has made it possible to efficiently and efficiently convert waste dirt-mixed waste plastic and, if necessary, waste lubricating oil without increasing the cost. An object of the present invention is to provide a method for pyrolyzing plastics.

[0015]

Accordingly, a method for thermally decomposing waste plastic according to the present invention comprises a step of melting and dehydrochlorinating mixed waste plastic to which dirt containing salt is adhered in a batch in a pyrolysis tank. When the waste plastic is turned into oil by decomposing it, metals and pottery (meaning foreign matters other than metal such as pottery pieces and glass pieces) are separated from the mixed waste plastic, and the mixed waste plastic is separated by 20 m.
volume of expanded polystyrene using a predetermined amount of water and a pyrolyzed light and medium oil of polyethylene and / or polypropylene or a paraffin-rich mineral oil heated to approximately 60 ° C. At the same time, the mixed waste plastic is washed, the salt contained in the dirt is transferred to water, and dewatering is performed.
A plastic piece suitable for oiling is floated by a specific gravity separation liquid of 5 to 1.06, and a plastic piece suitable for oiling is collected by sedimenting a plastic piece not suitable for oiling, and the collected waste plastic is heated. After melting in a cracking tank and dehydrochlorinating, mild plasticization of waste plastic is performed at a low temperature within the temperature range that can be thermally decomposed, half of the waste plastic is turned into oil, and the residue is pyrolyzed. It is characterized in that the residue is subjected to hard pyrolysis at a high temperature within a temperature range in which waste plastics can be extracted from the tank and thermally decomposed, and the residue is turned into oil.

One of the features of the present invention is that, as a precondition for separating oily raw materials from contaminated mixed waste plastic, metal and ceramics are removed from the mixed waste plastic and crushed to a particle size of 20 mm or less. The point is that the foamed polystyrene is reduced in volume by using oil heated to 60 ° C. and the mixed waste plastic is washed.

The main causes of contamination of the mixed waste plastic are soy sauce, sauce, food oil, mayonnaise, sand, fertilizer, and the like attached to the surface of the waste plastic. When these are washed with water, the whole washing water becomes dirty, and the oil quality cannot be dissolved. The use of oil instead of water greatly ameliorates these problems.

[0018] Further, since soy sauce and the like contain salt, if waste plastic is burned while soy sauce is adhered, dioxin may be generated, and a predetermined amount of water is added to transfer the salt to the water side. It is important that Furthermore, in order to increase the processing speed of the specific gravity separation of the mixed waste plastic, it is necessary to reduce the volume of the expanded polystyrene having a very low bulk specific gravity.

Therefore, in the present invention, oil is used for volume reduction and washing, and this oil is a pyrolyzed light and medium oil of polyethylene and / or polypropylene or a paraffin-rich mineral oil (for example, paraffin kerosene). Is valid. By heating this oil to about 60 ° C and bringing it into contact with the contaminated mixed waste plastic for a short period of time, only the volume of the expanded polystyrene is reduced, and the quality of other waste plastics is not affected. The dirt is separated by oil and washed.

Dirty liquid and salt water settle out in a short time and are separated from oil. The volume-reduced expanded polystyrene and other waste plastics are taken out of the system, removed from the oil, and sent to a specific gravity separation tank. Sewage is sedimented and concentrated and can be taken out from the tank bottom.

The oil used for volume reduction and washing is preferably pulled out from the bottom of the tank with a pump, filtered, heated to a temperature of about 60 ° C. by a heater, and then sent again to a volume reduction / washing / dehydrating machine. . It is important that the temperature of the oil is always uniform, and if the temperature rises locally, a part of the mixed waste plastic will be dissolved, which will adversely affect the specific gravity separation performance. Oil heating is avoided in the jacket, and external heat exchange is preferred.

Foamed plastics other than polystyrene foam, for example, foamed polyethylene, cannot be reduced in volume under the above conditions and floats at the inlet liquid level. It is desirable to have a structure that allows for

Further, an apparatus used for the above-mentioned volume reduction, washing and dehydration is also novel. That is, according to the present invention, a volume reduction / washing / dehydrating machine used for volume reduction of foamed polystyrene and washing / dehydration of mixed waste plastic, wherein the main body is supplied with waste plastic from its upper end and has a certain amount It has a tank shape into which water is injected, and the inside of the tank-like body is made of a pyrolytic light and medium oil of polyethylene and / or polypropylene heated to about 60 ° C. or a paraffin-rich mineral oil and mixed waste plastic. A region where the crushed pieces come into contact with each other is provided, and at the bottom of the tank-shaped body, there is provided a first transfer conveyor for sending out the crushed pieces of mixed waste plastic, oil and sewage while stirring and mixing. At the end of the conveyer, a second piece of crushed waste plastic is transferred to the specific gravity separation tank.
A transfer conveyor is connected, and a separation plate for separating crushed pieces of mixed waste plastic from oil and sewage is interposed at a connection portion of the first and second transfer conveyors, and a specific gravity separation of sewage and oil is performed. The present invention can provide a mixed waste plastic volume reducing / washing / dehydrating machine characterized by having a stagnant region.

As the specific gravity separation liquid, a liquid obtained by mixing ethylene glycol and water at a volume ratio of about 60:40 is preferably used at room temperature. At that time, the specific gravity is 1.05, and polystyrene or ABS resin that cannot be floated with water can be floated. However, other liquids having a specific gravity of 1.05 to 1.06 can be used, and other liquids can be used, and plastics suitable for oiling are floated, and plastics not suitable for oiling are settled to form oil. Waste plastics suitable for waste can be recovered.

The crushed pieces of mixed waste plastic that have been reduced in volume, washed, and dewatered are cut into oil and then sent to a specific gravity separation tank. The structure of the specific gravity separation tank may be a conventional type. However, when the hydrocyclone method is adopted to increase the processing capacity, the size of the waste plastic crushed pieces is preferably crushed to a particle size of 10 mm or less.

Polyethylene, polypropylene,
The polystyrene and the ABS resin are separated by centrifugation to separate a specific gravity separation liquid, dried and used as a raw material for an oiling apparatus and the like. The recovered liquid is preferably sent back to the specific gravity separation tank.

Although the heat source of the first pyrolysis tank is not particularly limited, similar to the prior application of the present inventors, mild pyrolysis is performed at a low temperature within a temperature range in which waste plastic can be pyrolyzed. However, a part of the semi-pyrolyzed oil may be left in the pyrolysis tank, and the amount of heat may be supplied by the retained heat of the remaining semi-pyrolyzed oil.

Further, when organic matter is thermally decomposed, carbon is generated. If this is not discharged to the outside of the system, it becomes a strong coke on the inner surface side, hinders heat transfer, blocks pipes and the like, and becomes inoperable. In the pyrolysis method of the present invention, only the mild pyrolysis reaction is performed in the first pyrolysis tank, and the hard pyrolysis reaction is performed in the second pyrolysis tank. Occurs in the pyrolysis tank.

Therefore, a vertical or horizontal jacketed cylindrical tank, for example, a cylindrical tank is used in the second pyrolysis tank, and a stirrer having hollow blades and a shaft is provided in the tank, and the hollow shaft is provided. In addition, it is preferable to adopt a structure in which steam is flown through the blades and steam is blown out from the hole at the blade tip to the inner wall of the tank.

In the second pyrolysis tank, the hard pyrolysis is performed intermittently, so that steam is not blown during the hard pyrolysis.
After the hard pyrolysis is completed, steam is introduced for cooling and discharging the residue in the tank and cleaning the inner wall. The residue and steam can be sent to a residue receiving tank, and the steam can be separated in the tank, condensed in a cooler, and sent to an oil / water separation tank.

The waste lubricating oil can also be converted to oil by utilizing the waste plastic pyrolysis method of this embodiment. That is, after the waste lubricating oil is dehydrated, it can be heated to approximately 400 ° C., introduced into the thermal decomposition tank together with the mixed waste plastic, and thermally decomposed.

By the way, products obtained from the thermal decomposition of organic substances are rich in olefins, have poor oxidative stability, and when they come into contact with air, gum and tar are generated over time, and the odor also worsens. Also, waste plastic and waste lubricating oil contain many additives, and when pyrolyzed,
Chlorine, nitrogen, and sulfur compounds are contained in the product, which is not preferable.

Therefore, of the waste plastic or the pyrolysis oil obtained by pyrolysis of waste plastic and waste lubricating oil, the fraction having a distillation temperature of about 170 ° C. or more is brought into contact with a methanol solvent at room temperature, When impurities contained in the fraction are transferred to a methanol solvent for separation, sediment (gum, tar content) and bad odor hardly occur even after 2 months, and chlorine, nitrogen, sulfur compounds, etc. It has been confirmed that impurities of can be greatly reduced. This high quality treatment is disclosed in US Pat.
855768 (Staniculescu, eta)
l. ) Technology can be adopted.

Clean mineral oils have little polarity, but impurities (chlorine, nitrogen, sulfur, gum-forming substances, etc.) have a high polarity. In the present invention, these impurities are extracted with a methanol solvent utilizing such a difference in polarity. When these impurities are separated, it is preferable to carry out the separation in combination with the thermal decomposition and the distillation. In particular, since the polarity of nitrogen is high, the removal rate of nitrogen compounds is 85 wt% or more. Processing conditions are room temperature,
The extraction is preferably performed by a continuous / multistage extraction method at normal pressure, and the methanol solvent can be recovered and reused. The recovery is over 98%. The raffinate can be mixed and reused in asphalt.

In the thermal decomposition method of waste plastic according to the prior application of the present inventors (Japanese Patent Application No. 232106), it is assumed that melting, dehydrochlorination and thermal decomposition are processed in one factory. According to the concept of the present invention, the mixed waste plastic collected separately is first crushed in a pretreatment plant, separated into specific gravity, and then can be converted into high bulk specific gravity dehydrogenated plastic in a dehydrochlorination step. It is collected in a large-scale factory that performs pyrolysis, distillation, and if necessary, high quality, and can be safely made into high quality oil by skilled workers. Pretreatment plants should be dispersed in various places. Also, after dehydrating waste lubricating oil,
It can be processed by the pyrolysis method of this example.

That is, the waste plastic to be treated is brought into contact with pyrolysis light oil (solvent) in a roughly crushed state,
When heated to C, it is dissolved and introduced into a pressurized dehydrochlorination reaction tank, so that the dehydrochlorination treatment can be performed with high efficiency in a step separate from the thermal decomposition step. Sample polypropylene (90wt%) / vinyl chloride (10w) in autoclave
t%), the temperature was 320 °
C. A dehydrochlorination rate of 99% was obtained with a residence time of 2 hours. The pressure can be up to 50.0 × 10 ⁴ Pa (5.
1 kgf / cm ² ). Since the dehydrochlorination rate increases as the hydrogen chloride partial pressure increases, the pressure (3 to 5 kgf / c
m ² ) method is adopted. In addition, when dehydrochlorinating, in order to prevent light oil distilling of the polystyrene resin, the operating temperature and pressure of the dehydrochlorination reaction tank are adjusted so that the light oil does not evaporate. Further, in order to prevent a short path of chlorine in the reaction tank, it is preferable that at least two reaction tanks are provided and a switching system is used.

The waste plastic pyrolysis method according to the present invention comprises the steps of melting and dehydrochlorinating mixed waste plastic to which dirt containing salt is adhered, followed by thermal decomposition.
In converting waste plastic to oil, metal and ceramics are separated from the mixed waste plastic, and the mixed waste plastic is crushed to a particle size of 20 mm or less, and polyethylene and / or heated to approximately 60 ° C. with a predetermined amount of water. Or using pyrolyzed light-medium oil of polypropylene or mineral oil rich in paraffin to reduce the volume of expanded polystyrene,
After washing the mixed waste plastic to transfer the salt contained in the dirt to water and performing dehydration, a crushed piece of the mixed waste plastic is converted into a plastic piece suitable for oiling by a specific gravity separation liquid having a specific gravity of 1.05 to 1.06. Is recovered, and waste plastics suitable for oiling are recovered by sedimenting plastic pieces unsuitable for oiling, and the recovered waste plastics are dissolved using pyrolysis light oil heated to approximately 150 ° C. as a solvent. And the waste plastic thus dissolved and reduced in volume together with the above-mentioned pyrolyzed light oil at a temperature of about 300 ° C.
C, 29.4 × 10 ⁴ P under the condition of a residence time of about 1 hour
a to 49.0 × 10 ⁴ Pa (3 to 5 kgf / cm ² ), pressurized to a pressure range to carry out a dehydrochlorination reaction, and heat the molten and dehydrochlorinated waste plastic in a pyrolysis tank. Mild pyrolysis of waste plastic at a low temperature within the decomposable temperature range to liquefy half of waste plastic,
The residue is extracted from the pyrolysis tank, and the residue is hardened at a high temperature within a temperature range in which the waste plastic can be thermally decomposed, so that the residue is turned into oil.

Except for the melting and dehydrochlorination treatment, the present invention is substantially the same as the first invention (claim 1), and the description thereof is also applied as it is, so that the detailed description is omitted.

As a method for treating expanded polystyrene, instead of dissolving with a solvent or the like, pyrolyzed light and medium oil of polyethylene and / or polypropylene (distillation range: 100 to 250)
° C) or paraffinic oil (kerosene fraction) and temperature about 60 °
By contacting with C, defoaming and volume reduction are performed in a short time (about 30 seconds), and a cake of resin is obtained at the bottom of the tank. About 3 kg of polystyrene foam can be reduced with one liter of oil.
Since oil adheres to the surface of the resin mass, a recycled resin can be obtained by separating the mass by vacuum heating or the like.

According to the present invention, the boiling point is from 100 ° C. to 250 ° C.
Of pyrolyzed light and medium oils of polyethylene and / or polypropylene or paraffin-rich mineral oil at about 60 ° C
, Foamed light-medium oil or mineral oil is brought into contact with styrofoam to defoam and reduce the volume, and the reduced volume is melt-vacuum degassed to obtain a regenerated polystyrene resin. And a method for regenerating a polystyrene resin characterized by the following.

The volume reduction of the expanded polystyrene is performed at a low temperature of about 60 ° C., the thermal energy is small, and the regenerated resin is not thermally degraded at all. The liquid used is inexpensive (50-80
About 95% or more can be collected and reused in (yen / liter).
The cost of recycling from rice cake-like resin is economical because the equipment is simpler than the dissolution method of limonene and the like.

According to the present invention, the waste plastic mixed with dirt containing salt is thermally decomposed,
To convert waste plastic into oil, use pyrolyzed light oil heated to about 150 ° C as a solvent to dissolve and reduce the volume of polyethylene, polystyrene, and polypropylene resin. Then, mix waste plastic containing pyrolyzed light oil and vinyl chloride. And 29.4 × 10 ⁴ Pa to 49.0 under the condition of a temperature of about 300 ° C. and a residence time of about 1 hour.
A method for dehydrochlorinating waste plastics, characterized in that a dehydrochlorination reaction is performed by applying pressure to a pressure range of × 10 ⁴ Pa (3 to 5 kgf / cm ² ).

In this case as well, after dissolving and reducing the volume of the mixed waste plastic by a dissolving and volume reducing machine, the mixed waste plastic is alternately or sequentially introduced into at least two pressurized dehydrochlorination reactors provided in parallel to form a solvent. -It is advisable to carry out a dehydrochlorination reaction under pressure.

When the pyrolyzed light oil (solvent) is heated to a temperature of about 150 ° C., polyethylene, polypropylene and polystyrene dissolve, so that the film or foam may be roughly crushed. It is safe because it can be supplied to the dehydrochlorination reactor in a slurry state. Further, since dehydrochlorination is performed in a pressurized state, high efficiency can be obtained.

Since the pyrolyzed light oil (solvent) is liquid up to the processing temperature of dehydrochlorination, the heat transfer coefficient at the time of raising the temperature of the waste plastic is high. In addition, pyrolyzed light oil (solvent) can be recycled, and if the pressure in the reaction tank is reduced, light oil decomposed during dehydrochlorination can be secured. If only startup is prepared, only a small amount of replenishment is required.

In the present dehydrochlorination method, dissolution / dehydrochlorination
It can be processed up to volume reduction and can be applied to uses other than oiling. Since at least two reaction tanks are provided, there is no short path for chlorine, and stable operation is possible.

During dehydrochlorination, considerable bubbles are generated on the liquid surface of the reaction tank, making it difficult to control the liquid surface. However, by performing the reaction under a pressurized state, the generation of bubbles is suppressed, and a stable operation becomes possible. . In addition, the discharge is facilitated by increasing the differential pressure between the pressure adjusting valve and the tank bottom discharge valve.

The decomposition reaction of the PVC resin in the solvent is as follows:
Nitrobenzene, tricresyl phosphate, diacryl phthalate and the like are used as solvents. The generation rate of the generated amount of hydrogen chloride was measured, and it was found that hydrogen chloride acts as an autocatalyst to promote the dehydrochlorination reaction. Further, the pyrolyzed light oil (mainly polystyrene pyrolyzed light oil) easily dissolves in the polyolefin resin by heating to about 130 ° C. In particular, polyethylene, polypropylene, and PVC resins have lower decomposition onset temperatures due to the inclusion of polystyrene. Pyrolyzed light oil (mainly polystyrene pyrolyzed light oil)
In addition, diacryl phthalate contained in the PVC resin is also used as a solvent, and 29.4 × 10 ⁴ Pa to 49.0 × 10 ⁴ P
By increasing the pressure to a (3 to 5 kgf / cm ² ), the concentration of hydrogen chloride can be increased to promote the dehydrochlorination reaction.

Further, since the pyrolyzed light oil dissolves polyethylene, polypropylene and polystyrene to form a slurry, it can be smoothly introduced into the reaction tank, and is heated in a relatively low viscosity liquid under pressure in the reaction tank. The heat transfer is also significantly improved compared to 100% resin.

When dehydrochlorination (about 300 ° C.) of mixed waste plastic containing PVC resin is carried out at normal pressure, the polystyrene resin partially decomposes and distills out together with hydrogen chloride, which makes post-treatment difficult. The reaction tank is pressurized, and a dehydrochlorination reaction is performed in a state where light oil such as decomposed polystyrene resin is liquefied,
After the hydrogen chloride is discharged from the reaction tank, it is preferable to send the decomposed light oil to the condenser and the light oil receiving tank while sequentially reducing the pressure in the tank. The dehydrochlorinated molten resin is introduced into a pyrolysis tank.

According to the present invention, the following effects can be obtained. Separation of mixed waste plastic In the case of mixed waste plastic containing styrofoam, soy sauce, sauce, mayonnaise and other dirt and moisture attached, only the expanded polystyrene can be reduced in volume to improve bulk specific gravity and specific gravity separation efficiency, and dirt can be washed and dewatered at the same time. It is possible to do. In addition, since the foamed polystyrene is brought into contact with the oil, the contact is made uniformly and the volume can be surely reduced. 2. Since a specific gravity separation liquid having a specific gravity of 1.05 to 1.06 is used, polystyrene or A which has not been able to be recovered conventionally can be used.
The BS resin can be recovered, and the yield can be greatly improved. 3. Since it is possible to separate a PVC resin, a PET resin, and a thermosetting resin that are not suitable for oiling, the economics, stability, and product properties of the oiling device can be significantly improved. 4. The use of the pyrolysis method of the present invention is wide, and it is possible to separate and wash and dehydrate agricultural vinyl and polyvinyl chloride, which is more economical than the conventional method. In addition, it can be applied to the conversion of blast furnace reducing materials and cement to fuel. 5. The use of oil cleaning makes it easier to remove dirt components and greatly reduces wastewater treatment.

Countermeasures against carbon in the second pyrolysis tank Since the second pyrolysis tank performs the pyrolysis reaction at approximately 460 ° C., hard pyrolysis can be performed in a short time, and the processing speed can be greatly improved. For example, 1 near 400 ° C
If the temperature is increased by 0 ° C., the reaction rate is twice as high. Even if carbon adheres to the inner wall of the pyrolysis tank, it can be removed while washing with steam in an early stage, and a decrease in heat transfer coefficient can be prevented. 3. The steam can cool the carbon residue and discharge it out of the system, and the work can be done safely without blocking the discharge valve. 4. The residue yield of the oiling unit is greatly reduced.

Improvement in Quality of Pyrolysis Oil The quality of kerosene and gas oil fractions, which are main products among pyrolysis oils, can be greatly improved. That is, a) Oxidation stability is on par with petroleum products. B) Organic chlorine compounds, nitrogen compounds, sulfur compounds, and bromine compounds, which are impurities, are reduced.
% Or more. C) It can be stored for a long time, and can be used with confidence as a boiler fuel as well as a private power generation fuel.

Pressurized dehydrochlorination treatment The dehydrochlorination efficiency can be improved by the pressure treatment. 2. The polystyrene resin is partially thermally decomposed during dehydrochlorination, but light oil can be recovered by pressurization, and the oil conversion can be improved. 3. The capacity of the hydrogen chloride absorption tower is reduced, and the operation is stabilized. 4. Since at least two pressurized dehydrochlorination reactors are provided to perform the processing alternately or sequentially, a short path of chlorine can be prevented, and the dehydrochlorination rate is stabilized. 5. Pre-treatment plants can be dispersed in various places,
Transportation costs can be reduced. 6. Responsibility for waste in each region increases cost awareness and leads to weight reduction. 7. The pretreatment facility is a crushing, specific gravity separation and dehydrochlorination process, and does not require advanced technology and can be processed with confidence. 8. Since the pyrolysis / distillation operation requires advanced technology, safety, quality, and economic efficiency can be significantly improved by performing a large-scale treatment by a skilled operator. 9. The waste lubricating oil and the waste plastic can be mixed and treated, and the properties of the recycled product become paraffin-rich, and the flammability is improved.

[0055]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to specific examples shown in the drawings. 1 to 6 show a preferred embodiment of the waste plastic pyrolysis method according to the present invention. The processing raw material is obtained by separating and collecting waste plastics from general wastes, and the foreign substances include thermosetting resins such as metal materials including aluminum, PET bottles, bottles, and pottery. Dirt and moisture such as soy sauce, mayonnaise, and sauce adhere to the foreign matter and the mixed waste plastic.

As shown in FIG. 1, the separated and collected processing raw materials were separated from iron-based materials by a magnetic separator and aluminum cans and the like by an aluminum separator after the bag was broken. The mixed waste plastic is separated by a crushing machine into a diameter of about 20 mm or less, and when the hydrocyclone method is used to increase the processing capacity of the specific gravity separation, it is crushed to a diameter of 10 mm or less. A known device can be used as a pretreatment device to be used.

Next, in the volume reduction / washing / dehydrating machine, the main body 10
The waste plastic is put in from the upper end, and a tank-like shape into which a certain amount of water is poured is formed. Inside the main body 10, a pyrolyzed light medium oil of polyethylene resin or polypropylene resin is heated to about 60 ° by the heater 12. C and is circulated by the circulation pump 11. The crushed pieces P of the crushed mixed waste plastic are reduced in volume, washed and dewatered by the main body 10
Is continuously charged from the upper end into contact with the pyrolyzed light and medium oil at about 60 ° C., and thus the crushed pieces P of the mixed waste plastic are stirred and washed, and dirt such as soy sauce, sauce, mayonnaise and the like is removed. Or the expanded polystyrene resin is reduced in volume. Further, a small amount of water w1 is injected into the main body 10 of the volume reduction / washing / dehydrating machine from the upper end, and the salt in the washed dirt is transferred to the water w1.

The mixed waste plastic crushed pieces P washed and reduced in volume and the pyrolyzed light and medium oil and water are transferred to the vertical second transfer conveyor 14 while being stirred by the first transfer conveyor 13. Then, the pyrolyzed light and medium oil containing dirt and the salt water w2 are easily separated from the waste plastic by the separation plate 21 at the lower end of the vertical conveyor 14.

The contaminated salt water w2 and the pyrolyzed light medium oil containing dirt are easily separated in the tank below the separation plate 21 due to the difference in specific gravity, and the contaminated salt water w2 is discharged from the bottom of the tank, and The quality oil is drawn out of the tank by the circulation pump 11, filtered by the filter 16, heated to about 60 ° C. by the heater 12, and circulated to the main body 10 of the volume reduction / washing / dehydrating machine. The quality of sewage is comparable to domestic wastewater.

The crushed pieces P of the mixed waste plastic that have been washed and reduced in volume are lifted by a vertical conveyor 14 to be oiled, and are continuously sent to a specific gravity separation tank 15 via a disperser 23. A specific gravity separation liquid 17 in which ethylene glycol and water are mixed and dissolved at a volume ratio of approximately 6: 4 at room temperature is circulated in the specific gravity separation tank 15. Among the crushed pieces P of the mixed waste plastic introduced into the specific gravity separation tank 15, polyethylene, polypropylene, polystyrene, and ABS resin float due to a specific gravity difference from the specific gravity separation liquid 17, and PVC resin,
PET resin and thermosetting resin settle. Shower equipment 18 is provided to efficiently settle the latter resin,
The shower liquid is sprayed on the floating plastic, and the specific gravity separation liquid 17 is given a flow at a constant speed.

The floating plastic P1 and the sedimented plastic P2 are transferred to the respective centrifuges 20, 19, and are drained and dried. The liquid is removed by centrifugal separator 20, 1
After being collected from the receiving tank of the separator 9 and the separation plate 22 by the collection pump 24 and filtered by the filter 25, it is circulated to the specific gravity separation tank 15.

Next, as shown in FIGS. 2 to 4,
Plastic (polyethylene, polypropylene, polystyrene and ABS resin) suitable for oiling P1 and almost 1 wt.
% Vinyl chloride is introduced into the melting and volume reducing machine 30. The melting / reducing device 30 has a structure provided with a jacket 31. The melting / reducing device 30 is supplied with a pyrolysis light oil (solvent) O heated to approximately 150 ° C. The polypropylene and polystyrene films and foams are dissolved in contact with pyrolytic light oil (solvent) O at approximately 150 ° C. to form a slurry.

The amount of the PVC resin mixed in the specific gravity separation tank 15 has been reduced to about 1 wt%, but in order to make this 1 wt% PVC resin as close to zero as possible, two pressurized dehydrochlorination tanks 32 are used. 32 are provided in parallel and operated in a switching system.

The pressurized dehydrochlorination tank (pressurized dehydrochlorination reactor) 32 has a structure provided with a jacket 33, and a stirring transfer device 41 is provided inside. The slurry-like plastic fed into the pressurized dehydrochlorination tank 32 together with the pyrolyzed light oil is 29.4 × 10 ⁴ Pa to 49.0 ×.
It is pressurized to a pressure range of 10 ⁴ Pa (3 to 5 kgf / cm ² ), heated up to a temperature of about 320 ° C., kept for about 1 hour, and subjected to a dehydrochlorination treatment.

When the dehydrochlorination reaction is completed, the pressure in the system is reduced by the pressure regulating valve 36, the pyrolysis light oil (solvent) O is recovered in the receiving tank 40, and then the tank bottom valve 35 is opened to dehydrogenate. The waste plastic is put into a first pyrolysis tank 4
Put into 2. The dehydrochlorinated gas is recovered or neutralized by hydrochloric acid in the absorption tower 37. Two pressurized dehydrochlorination tanks 32, 3
2 are operated alternately.

The liquefaction system of the present example assumes continuous operation. The plastic charged in the first pyrolysis tank 42 stays at a temperature of approximately 400 ° C. and a normal pressure for approximately 1.5 hours, and is subjected to semi-pyrolysis (mild pyrolysis). The first pyrolysis tank 42 employs a system having a jacket 43 (or a kettle system), and heat is supplied at a temperature of approximately 700 ° C. or less.

The decomposition vapor by the semi-pyrolysis is sent from the first pyrolysis tank 42 to the distillation column 44, and the residue of the semi-pyrolysis is removed by the screw 45 from the bottom of the first pyrolysis tank 42 to the second pyrolysis tank 42. It is intermittently fed into the tank 46.

The temperature of the second pyrolysis tank 46 is approximately 460 °
C, stays at normal pressure for about 30 minutes, and undergoes high-temperature hard pyrolysis while being stirred by the stirrer 47. The second pyrolysis tank 46 has a jacket 48 (or a pot type).
And heat for hard pyrolysis is almost 700 ° C
It is supplied at the following temperatures: The pyrolysis vapor is sent from the second pyrolysis tank 46 to the first pyrolysis tank 30.

In the second pyrolysis tank 46, as shown in FIG. 5, the shaft of the stirrer 47 and the blades are hollow, and low-pressure steam S is supplied from the outside.
The carbon residue generated during the hard pyrolysis is attached to the inner wall of the second pyrolysis tank 46, but after the hard pyrolysis is completed, the tank bottom valve 49 is opened, and low-pressure steam is discharged from the hole at the tip of the blade. It is ejected and cooled while removing carbon attached to the inner wall of the second pyrolysis tank 46, and the residue can be discharged to the residue receiving tank (outside the system) 50 by steam pressure.

The low-pressure steam in the residue receiving tank 50 is separated by evaporation and condensed by the cooler 51, and then separated by oil and water in the drain water tank 52. The residue is discharged out of the system after cooling. The pyrolysis paper generated from the first and second pyrolysis tanks 30 and 46 is introduced into the distillation tower 44.
After being quenched from 400 ° C. to 300 ° C. with the bottom liquid of No. 4, it is introduced into the distillation column 44 and separated into cracked gas, light oil and medium heavy oil. Part of the cracked gas and light oil is used as fuel for the high-temperature gas generating furnace 53. Medium heavy oil cooler 5
At 6, it is cooled down to approximately 40 ° C. and sent to the high quality device 54.

The medium heavy oil is mixed and contacted with the methanol medium at a predetermined ratio at normal pressure for a certain period of time in the high-quality equipment 54, and impurities contained in the medium heavy oil are dissolved into the methanol medium side and dissolved. Separated from heavy oil. The medium heavy oil from which the impurities have been removed is recycled into the product, the liquid containing the impurities is recycled by evaporating the methanol medium in an evaporator, and the remaining liquid is discharged out of the system.

Since the decomposition gas of the ABS resin pyrolysis contains cyan gas and bromine gas, the decomposition gas is sent to the combustion furnace at about 100 ° C. without cooling, and is cooled to 1100 ° C. or more under excess oxygen. Burns at high temperatures.

In the system of this embodiment, waste lubricating oil can be treated at the same time.
C and the same first pyrolysis tank 42 as waste plastic
Should be introduced.

FIG. 6 shows a preferred embodiment of an apparatus for reducing, washing and recycling waste expanded polystyrene used for the regeneration of polystyrene according to the present invention. Basically, the reduced volume of the mixed waste plastic shown in FIG. 1 is shown.・ Has the same configuration as the washing / dehydrating machine. That is, the apparatus main body 62 has a tank shape into which waste foamed polystyrene 60 is injected from the upper end and a certain amount of water 61 is injected. The oil is heated to about 60 ° C. by a heater 64 and a circulation pump 65
Has been circulated by

The waste expanded polystyrene 60 is continuously introduced into the apparatus main body 62 from the upper end, and comes into contact with the pyrolysis light and medium oil at about 60 ° C., and the waste expanded polystyrene is stirred and washed, soy sauce, sauce, Dirt such as mayonnaise is removed and the volume is reduced at the same time. In addition, water 6
A small amount of 1 is injected, and the salt in the washed soil is transferred to the water side.

The washed and reduced volume waste polystyrene, pyrolyzed light and medium oil and water are transferred to the vertical second transfer conveyor 68 while being stirred by the first transfer conveyor 63, and contain dirt. The pyrolyzed light-medium oil and the salt water are easily separated from the waste polystyrene by the separation plate 67 at the lower end of the vertical conveyor 68 and stored in the receiving tank 69.

The dirty salt water and the pyrolyzed light-medium oil containing dirt are easily separated in the receiving tank 69 due to the specific gravity difference, and the dirty salt water 70 is discharged from the bottom of the receiving tank 69, and the pyrolyzed light-medium oil is discharged. Is drawn out of the receiving tank 69 by the circulation pump 65, filtered by the filter 66, heated to about 60 ° C. by the heater 64, and circulated to the apparatus main body 62.

The waste polystyrene that has been washed and reduced in volume is lifted by a vertical conveyor 68 to be drained, continuously fed into a deaerator-type melting machine 71, and heated while being heated to a predetermined melting temperature by a heat medium 72 to be removed. It becomes a slurry state. The polystyrene in a slurry state is sent from the deaeration type melter 71 to the cooling water tank 14 by the screw 78 and cooled, and is pelletized by the pelletizer 77 to be a regenerated product.

On the other hand, the thermally decomposed light medium oil adhering to the waste polystyrene evaporates from the degassing type melter 71, is condensed by the condenser 74, and is sucked into the oil receiving tank 75 by the vacuum pump 76.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structural example of a mixed waste plastic volume reducing / washing / dehydrating machine in a preferred embodiment of a waste plastic pyrolysis method according to the present invention.

FIG. 2 is a diagram illustrating an example of a system configuration of a thermal decomposition process in the embodiment.

FIG. 3 is a diagram showing a system configuration example of a dehydrochlorination step in the thermal decomposition step.

FIG. 4 is a diagram showing an example of the overall configuration of a system for the dehydrochlorination step.

FIG. 5 is a diagram showing a structural example of a second pyrolysis tank in the pyrolysis step.

FIG. 6 is a diagram showing an example of a system configuration used for a method for regenerating polystyrene according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Main body of volume reduction / washing / dehydrating machine 13 1st transfer conveyor 14 2nd transfer conveyor 15 Specific gravity separation tank 16 Specific gravity separation liquid 21 Separation plate 30 Melting / volume reduction machine 32 Pressure dehydrochlorination tank (Pressure dehydration) Hydrogen chloride reactor) 42 First pyrolysis tank 46 Second pyrolysis tank

Claims (11)

[Claims] 1. Mixed waste plastic to which dirt containing salt is adhered is melted and dehydrochlorinated in batches in a pyrolysis tank and then thermally decomposed to convert the waste plastic to oil. Separates waste plastics and crushes waste plastics to a particle size of 20 mm or less, and heats a predetermined amount of water and heated to approximately 60 ° C. The volume of foamed polystyrene was reduced using a mineral oil, and the mixed waste plastic was washed to transfer the salt contained in the dirt to water and dewatered. ~ 1.06
The plastic pieces suitable for oiling are floated by the specific gravity separation liquid of the above, and the plastic pieces not suitable for oiling are settled to collect waste plastic suitable for oiling, and the collected waste plastic is melted in a pyrolysis tank. After dehydrochlorination, the waste plastic is subjected to mild pyrolysis at a low temperature within the temperature range that can be thermally decomposed to liquefy half of the waste plastic, and the residue is extracted from the pyrolysis tank, A method for thermally decomposing waste plastics, comprising performing hard pyrolysis of residues at a high temperature within a temperature range in which waste plastics can be thermally decomposed to convert the residues into oil. 2. Melting and dehydrochlorinating mixed waste plastic to which dirt containing salt has adhered and then thermally decomposing the waste plastic into oil so as to separate metals and pottery from the mixed waste plastic. Crushing the mixed waste plastic to a particle size of 20 mm or less, using a predetermined amount of water and pyrolyzed light and medium oil of polyethylene and / or polypropylene heated to approximately 60 ° C., or paraffin-rich mineral oil, After reducing the volume of the expanded polystyrene, washing the mixed waste plastic to transfer the salt contained in the dirt to water, and performing dehydration, the crushed pieces of the mixed waste plastic are subjected to a specific gravity of 1.05 to 1.06.
Pyrolysis plastic oil suitable for oiling is floated by the specific gravity separation liquid, and waste plastic suitable for oiling is collected by sedimentation of the non-oiling plastic pieces, and pyrolyzed light oil heated to approximately 150 ° C Is used as a solvent to dissolve and reduce the volume of the recovered waste plastic, and then dissolve and reduce the volume of the waste plastic together with the pyrolyzed light oil under the conditions of a temperature of approximately 300 ° C. and a residence time of approximately 1 hour. 4 × 10 ⁴ Pa to 49.0 × 10 ⁴ Pa
(3 to 5 kgf / cm ² ), a dehydrochlorination reaction is performed, and the molten and dehydrochlorinated waste plastic is decomposed in a pyrolysis tank. Mild pyrolysis of waste plastics at a temperature to liquefy half of the waste plastics, extract the residue from the pyrolysis tank, and hard heat the residue at a high temperature within the temperature range where the waste plastics can be pyrolyzed A method for thermally decomposing waste plastics, which comprises decomposing the residue to oil. 3. A mild pyrolysis is performed at a low temperature within a temperature range in which the waste plastic can be thermally decomposed, and a part of the semi-pyrolyzed oil is left in the pyrolysis tank, 3. The method for pyrolyzing waste plastic according to claim 1, wherein the heat is supplied by the heat retained in the waste plastic. 4. Ethylene glycol and water are mixed at about 6: 4.
The method for thermally decomposing waste plastic according to any one of claims 1 to 3, wherein a specific gravity separation of the crushed pieces of the mixed waste plastic is performed at room temperature using a specific gravity separation liquid mixed at a volume ratio of: 5. After the completion of the hard pyrolysis of the waste plastic, steam is blown out from the tip of the blade through a hollow shaft and a blade of a stirrer provided in the pyrolysis tank, and carbon adhered to the inner wall of the pyrolysis tank. 5. The method for thermally decomposing waste plastic according to claim 1, wherein cooling is performed while removing the waste, and the residue is discharged out of the system by steam pressure. 6. After the waste lubricating oil is dewatered, it is heated to approximately 400 ° C.
6. A method for thermally decomposing waste plastics according to claim 1, wherein the waste plastics are heated together with the mixed waste plastics and introduced into a thermal decomposition tank for thermal decomposition. 7. A mixed waste plastic or a pyrolysis oil obtained by pyrolysis of a mixed waste plastic and a waste lubricating oil, a fraction having a distillation temperature of about 170 ° C. or higher is brought into contact with a methanol solvent, 7. The method for thermally decomposing waste plastic according to claim 1, wherein impurities contained in the waste plastics are transferred to a methanol solvent and separated. 8. In melting and dehydrochlorinating the mixed waste plastic containing vinyl chloride, the mixed waste plastic containing vinyl chloride was dissolved and reduced in volume using a pyrolysis light oil heated to approximately 150 ° C. as a solvent. Then, the waste plastic whose volume has been dissolved is reduced together with the pyrolyzed light oil to a temperature of approximately 300 ° C. and a residence time of approximately 1 ° C.
Under the condition of time, 29.4 × 10 ⁴ Pa to 49.0 × 10 ⁴
Pressurized to a pressure range of Pa (3 to 5 kgf / cm ² )
A dehydrochlorination method for waste plastics, wherein a dehydrochlorination reaction is performed. 9. The mixed waste plastic is dissolved and reduced in volume by a dissolving / volume reducing machine, and then alternately or sequentially introduced into at least two pressurized dehydrochlorination reactors provided in parallel. 9. The method for dehydrochlorinating waste plastic according to claim 8, wherein the dehydrochlorination reaction is performed under pressure. 10. Heating a pyrolyzed light and medium oil of polyethylene and / or polypropylene having a boiling point of 100 ° C. to 250 ° C. or a paraffin-rich mineral oil to approximately 60 ° C.,
After defoaming by reducing the volume of expanded polystyrene by contacting the pyrolyzed light or medium oil or mineral oil with expanded polystyrene,
A method for regenerating a polystyrene resin, further comprising degassing by melting and vacuum to obtain a regenerated polystyrene resin. 11. A volume reduction / washing / dehydrating machine used for volume reduction of expanded polystyrene and washing / dehydration of mixed waste plastics, wherein a main body is supplied with waste plastics from an upper end thereof and a predetermined amount of water is injected. Crushed pieces of polyethylene and / or polypropylene pyrolyzed light-medium oil or paraffin-rich mineral oil mixed with paraffin-rich mineral oil heated to about 60 ° C. A first transfer conveyor is provided at the bottom of the tank-shaped main body, while agitating and mixing crushed pieces of mixed waste plastic, oil and sewage while terminating the first transfer conveyor. Is connected to a second transfer conveyor for transferring the crushed pieces of the mixed waste plastic to the specific gravity separation tank, and the connection portion of the first and second transfer conveyors is used to crush the mixed waste plastic. And together with the separation plate for separating the oil and sewage is interposed, volume reduction, washing and dewatering of the mixed plastic waste, characterized in that the retention region to gravity separate the wastewater and oil are provided.