JP2005134079A - Condensation method and condenser for polystyrene pyrolysis gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently remove the contamination of in cooling tubes of in a condenser for condensing polystyrene pyrolysis gas. <P>SOLUTION: The cooling tubes 8 are arranged within the condenser 6 to pass a coolant therein. The polystyrene pyrolysis gas from a thermal decomposition device 1 is supplied to the condenser 6, in which it is cooled by the heat-exchange with the coolant in the cooling tubes 8, and a high boiling-point component containing styrene is condensed as an oil. When the surfaces of the cooling tubes 8 are contaminated, the oil obtained by the condensation is sprayed onto the surface of the cooling tubes 8 by a spray means 22, and the contamination is removed by the cleaning effect by spraying. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of supplying a pyrolysis gas generated by pyrolysis of polystyrene to a condenser and bringing it into contact with the surface of a cooling pipe disposed inside the condenser to condense, and the condenser.

  A large amount of plastics is discharged from factories and households as waste, and among these waste plastics, polystyrene is extremely large. Polystyrene includes foamed polystyrene used as food trays, packing materials and cushioning materials, and non-foamed polystyrene such as injection molded products such as home appliances and blow molded products. Such polystyrene includes homopolymers and copolymers such as AS resin and ABS resin. In the present invention, these are all handled as polystyrene.

  Most polystyrene is thermally decomposed into low molecules in the absence of oxygen by a thermal decomposition apparatus and recovered as fuel or styrene monomer. The pyrolyzer has a tank-type pyrolyzer (pyrolysis tank) or a tube-type pyrolyzer (reaction tube), and the tank-type pyrolyzer has a cylindrical tank whose bottom is formed in a conical shape. The main body is provided with a scraper for stirring and scraping off residues, and is suitable for thermally decomposing polystyrene in a batch manner with a certain residence time. The tube-type pyrolyzer decomposes while passing polystyrene inside, and is suitable for continuous operation.

  Polystyrene can be thermally decomposed in either a normal pressure state or a reduced pressure state. However, when recovering a styrene monomer in a high yield, it is desirable to thermally decompose in a reduced pressure state of about 2 kPa to 10 kPa. Pyrolysis under reduced pressure can suppress the formation of undesirable by-products such as low-boiling components such as ethylbenzene and toluene and heavy components such as styrene trimer and dimer. A method for thermally decomposing polystyrene in a reduced pressure state is described in Patent Document 1.

  However, for example, when polystyrene is pyrolyzed in a tube-type pyrolyzer under reduced pressure, the flow rate of the internal pyrolysis gas increases, and impurities such as undecomposed polystyrene, carbide and inorganic powder flow out from the piping on the outlet side. Become more. The condenser on the outlet side of the pyrolyzer is installed with a condenser that cools and condenses the pyrolysis gas, but when these impurities flow into the condenser, they adhere to the surface of the cooling pipe placed inside as dirt, The cooling efficiency is reduced.

  On the other hand, the higher the thermal decomposition temperature of polystyrene, the higher the thermal decomposition efficiency. For example, when polystyrene is thermally decomposed at a high temperature of about 600 ° C. to 800 ° C., the yield of styrene monomer can be increased to about 70%. However, for example, when polystyrene is pyrolyzed with a tubular pyrolyzer maintained at a high pyrolysis temperature, the flow rate of the internal pyrolysis gas increases as described above, and the amount of impurities flowing out from the piping on the outlet side is large. This increases the contamination of the cooling pipe surface in the condenser.

  In order to suppress as much as possible the impurities flowing out from the pyrolyzer from flowing into the condenser, Patent Document 2 proposes a method of providing a cooler that is directly connected to the outlet side of the pyrolyzer. In this method, the pyrolysis gas flowing out from the pyrolyzer is cooled by a cooler, and impurities that are likely to condense are returned into the pyrolyzer, thereby suppressing the inflow of impurities into the condenser.

Japanese Patent Laid-Open No. 11-199875 Japanese Patent Application No. 2003-64420

  When the cooler described in Patent Document 2 is installed, the amount of impurities flowing into the condenser is greatly suppressed. However, it is difficult to completely capture the impurities with the cooler, and the impurities that could not be trapped flow into the condenser installed downstream. For this reason, when the condenser is operated for a long time, impurities gradually adhere to the surface of the cooling pipe as dirt, which inhibits heat transfer and lowers the condensation efficiency.

  In order to recover the condensation efficiency, it is necessary to periodically discontinue the operation of the thermal decomposition system, disassemble the condenser, and remove the dirt adhering to the internal cooling pipe surface by cleaning or the like. However, since a tube-type pyrolyzer is often installed for the purpose of continuous operation, it is not preferable to periodically stop the condenser connected thereto. As a method of avoiding this, it is conceivable to install a plurality of condensers in parallel and switch them to operate continuously.

  SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to solve the above-mentioned problems in the conventional pyrolysis apparatus, and a first object is to provide a new condensation method therefor. The second object of the present invention is to provide a condenser having a structure suitable for the condensation method.

  The first invention according to the present invention that solves the above-mentioned problems is that the pyrolysis gas generated by the thermal decomposition of polystyrene is supplied to the condenser, and is condensed by bringing it into contact with the surface of the cooling pipe disposed inside the condenser. Is the method. And when this method adheres dirt on the surface of a cooling pipe, the oil content obtained by condensation is sprinkled on the surface of a cooling pipe, and the dirt is removed (claim 1).

  Further, the second invention according to the present invention for solving the above-mentioned problem is that the pyrolysis gas generated by the thermal decomposition of polystyrene is supplied to the condenser and condensed by bringing it into contact with the surface of the cooling pipe arranged inside the condenser. It is a method to do. And when this method adheres dirt on the surface of a cooling pipe, the dirt is scraped off and removed by a scraping means (claim 2).

  A third invention according to the present invention for solving the above-mentioned problems is a condenser for pyrolysis gas produced by thermal decomposition of polystyrene. And this condenser is equipped with the tank main body which has arrange | positioned the cooling pipe inside, and the oil dispersion | distribution cloth means which spreads the oil component obtained by condensation on the surface of the said cooling pipe (Claim 3).

  A fourth invention according to the present invention for solving the problem is a condenser for pyrolysis gas produced by thermal decomposition of polystyrene. And this condenser is equipped with the tank main body which has arrange | positioned the cooling pipe inside, and the scraping means which scrapes off the dirt of the surface of a cooling pipe (Claim 4).

  In the condenser according to the fourth aspect of the present invention, the scraping means includes a scraping portion disposed so as to be capable of reciprocating along the surface of the cooling pipe, a driven magnet provided in the scraping portion, and a tank body. A drive magnet provided on the outside can be provided.

  In the condenser according to the fourth aspect of the invention, the scraping means includes a scraping portion that is reciprocally movable along the surface of the cooling pipe, and a drive that extends from the scraping portion to the outside of the tank body. A shaft and a reciprocating drive unit connected to an extension of the drive shaft can be provided.

  In the condensation method according to the first aspect of the present invention, when dirt adheres to the surface of the cooling pipe, the oil obtained by condensation is sprayed on the surface of the cooling pipe to remove the dirt. The dirt can be removed while continuing. According to the experiment, the adhesion force of the impurities attached to the surface of the cooling pipe is relatively weak and can be easily separated and separated by spraying the oil without the spraying pressure being so high. Moreover, since a part of undecomposed polystyrene contained in the impurities is easily dissolved by the oil mainly composed of styrene obtained by the condensation, the impurities can be easily separated and separated from the surface.

  Furthermore, since the cleaning liquid to be sprayed is obtained by condensation, it is not necessary to provide a device for supplying a special cleaning liquid, and the oil content after cleaning can be returned to the original state and reused, so the operating cost is low. This method is particularly effective when polystyrene is pyrolyzed using a tubular heat exchanger.

  In the condensation method according to the second aspect of the present invention, when dirt adheres to the surface of the cooling pipe, the dirt is scraped off and removed by the scraping means, so that the dirt is removed while the operation of the condenser is continued. be able to. In addition, this method can shorten the time required for removing the dirt. Furthermore, the present method is particularly effective when pyrolyzing polystyrene using a tubular heat exchanger.

  The condenser according to the third aspect of the present invention includes oil dispersion cloth means for spraying the oil discharged from the oil discharge section onto the surface of the cooling pipe, so that the condensation according to the first aspect of the present invention is achieved by using this condenser. The method can be suitably carried out.

  Since the condenser according to the fourth invention is provided with scraping means for scraping off the dirt on the surface of the cooling pipe, the condensation method according to the second invention is preferably carried out by using this condenser. Can do.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a process flow diagram of a pyrolysis system for carrying out the condensation method of the present invention. In the figure, 1 is a thermal decomposition apparatus, 2 is a tubular thermal decomposition apparatus, 3 is a residue retention tank, 4 is a polystyrene supply apparatus, 5 is a heated gas generator, 6 is a condenser, 7 is an oil storage tank, and 8 is a storage tank. Cooling pipe, 9 is the first distillation apparatus, 10 is the second distillation apparatus, 11 is the hopper, 11a is the melting section, 12 is the extrusion section, 12a is the cylinder, 12b is the rotating screw, 12c is the motor, 13 is the residue Ejector, 14-17 is a pump, 18 is a decompressor such as a vacuum pump, 19 is a motor, 20 is a heating unit, 21 is a discharge valve, 22 is a spraying means, 23 is a spray nozzle, 24 is a pyrolysis gas cooler , 25 is a tank body, 26 is a pyrolysis gas supply unit, 27 is an oil content discharge unit, 28 is an uncondensed gas discharge unit, a to k are pipes, and l and m are ducts.

  The supply device 4 can be constituted by an extruder generally used for plastic injection molding or an extruder having a similar structure. The supply device 4 shown in the figure is constituted by such an extruder, and is supplied from a hopper 11 that receives polystyrene pieces finely pulverized by a pulverizer (not shown) or the like and conveyed by an air conveyor or a belt conveyor. A melting part 11a for heating and melting the polystyrene piece with a heater and an extrusion part 12 for extruding the molten polystyrene obtained in the melting part are provided. The hopper 11 is provided with a bridge breaker (not shown) as desired.

  The extrusion unit 12 has a cylindrical body 12a and a rotary screw 12b provided therein, and the rotary screw 12b is driven to rotate by a motor 12c. And the molten polystyrene about 200 to 250 degreeC extruded from the extrusion part 12 by rotation of the rotating screw 12b is supplied to the thermal decomposition apparatus 1 through the piping a coat | covered with the heat insulation layer.

  The pyrolysis apparatus 1 has a tubular pyrolyzer 2 for pyrolyzing polystyrene, a pyrolysis residence tank 3 communicated with the outlet side thereof, and a heating unit 20 surrounding them. The pyrolyzer 2 is composed of an elongated stainless steel tube or the like, and its dimensions vary depending on the desired processing capacity and the like, but are usually selected from a range of a tube diameter of about 50A to 200A and a length of about 5m to several tens of meters.

  The heating unit 20 surrounding the pyrolyzer 2 and the residue retention tank 3 is formed by walls insulated with ceramic fibers or castable, and the heating unit 20 is heated with a heating gas flowing inside. The heated gas flowing through the heating unit 20 is supplied from the heated gas generator 5 through the duct l, and the exhaust gas after heat exchange with the thermal decomposer 2 is discharged from the duct m. The heated gas generator 5 burns liquid fuel or gaseous fuel with a burner, and supplies the generated high-temperature combustion gas of about 800 ° C. to 1000 ° C. to the heating unit 20 as a heated gas.

  The molten polystyrene supplied from the supply unit 12 to the thermal decomposition apparatus 1 is heated from the surrounding heating unit 20 while moving inside the thermal decomposer 2 and is pyrolyzed at a thermal decomposition temperature of about 600 ° C. to 800 ° C. Is done. When pyrolyzing, a residue is generated, and this residue is discharged together with the generated pyrolysis gas to a residue retaining tank 3 communicating downstream.

  The residue retention tank 3 separates the residue from the pyrolysis gas flowing out from the outlet side of the pyrolyzer 2 and temporarily stores it inside. The residue retention tank 3 is composed of a vertical tank having an inner diameter of about 3 to 5 times that of the thermal cracker 2, and a residue discharge device 13 comprising a stirrer for stirring the residue and a residue discharge port therebelow. Provided. And the residue stored in the residue retention tank 3 is collect | recovered by the residue collection tank which is not illustrated from the piping k by opening the discharge valve 21 at any time. In addition, the residue residence tank 3 can also be comprised with a horizontal tank.

  The pyrolysis gas separated in the residue retention tank 3 flows out from the gas outflow part at the upper part thereof to the pipe b. The pyrolysis gas that has flowed out is cooled by a cooler 24 provided in the middle of the pipe b, and a part of the accompanying impurities is cooled and condensed and separated, and flows down the rising part of the pipe b and returns to the residue retaining part 3. A pyrolysis gas containing a small amount of impurities that could not be separated flows out from the outlet side of the cooler 24 and flows into the condenser 6 on the downstream side.

  The condenser 6 includes a tank body 25 having a pyrolysis gas supply unit 26, an oil component discharge unit 27 and an uncondensed gas discharge unit 28, a cooling pipe 8 disposed inside the tank body 25, and an oil component discharged from the oil component discharge unit 27. Is provided on the surface of the cooling pipe 8 with oil dispersion cloth means 22. Cooling water and cooling air circulate inside the cooling pipe 8 to cool the pyrolysis gas in contact with the surface by heat exchange. The pyrolysis gas supply unit 26 communicates with the piping b, the oil discharge unit 27 communicates with the piping d, and the tip of the piping d communicates with the oil storage tank 7. Further, the uncondensed gas discharge unit 28 communicates with the pipe f, and a decompression device 18 such as a vacuum pump is provided in the middle of the pipe f. The uncondensed gas flowing out from the pipe f is used as fuel for the heated gas generator 5, for example.

  The cooling pipe 8 is configured by connecting a plurality of cooling pipe elements formed in a straight line in parallel, and the whole is arranged horizontally below the tank body 25. The oil dispersion cloth means 22 includes a spray nozzle 23 disposed in the upper part of the tank body 25, a pipe c for supplying the oil stored in the oil storage tank 7 to the spray nozzle 23, and a pump 14 provided in the pipe c. The spray nozzle 23 is provided with a large number of jet holes in a header to which oil is supplied, so that fine oil droplets can be sprayed uniformly from above on the entire cooling pipe 8 and sprayed.

  The pyrolysis gas flowing into the condenser 6 from the pyrolysis gas supply unit 26 is cooled by the cooling pipe 8. The high-boiling components mainly composed of styrene are condensed by cooling, and the obtained oil is discharged from the oil discharge unit 27 to the oil storage tank 7 through the pipe d, and low-boiling components such as ethylbenzene and toluene are not condensed. It flows out from the discharge part 28 to the pipe f. Although the internal pressure of the condenser 6 can be changed by adjusting the suction force of the decompression device 18, the internal pressure of the pyrolyzer 2 is also linked to the adjusted decompression level.

  The oil mainly composed of styrene condensed in the condenser 6 is temporarily stored in the oil storage tank 7 from the pipe d, and a part thereof is supplied to the middle stage of the first distillation column 9 by operating the pump 15. The The oil is distilled in the first distillation column 9, and the separated low-boiling components such as benzene and toluene flow out to the pipe h from the top of the column. The low boiling point component that has flowed out to the pipe h is supplied as fuel for the heating gas generator 5, for example.

  A high boiling point component mainly composed of styrene is separated at the bottom of the first distillation column 9. The high boiling point component at the bottom of the column is supplied to the middle stage of the second distillation column 10 by operating the pump 16. The high boiling point components are distilled in the second distillation column 10, and the separated styrene flows out from the top of the column to the pipe j and is recovered in a styrene recovery tank (not shown). Further, heavy oil is separated and stays at the bottom of the tower, but this heavy oil is recovered from the pipe i to a heavy oil recovery tank (not shown) by operating the pump 17. The heavy oil stored in the heavy oil recovery tank can also be supplied as fuel for the heated gas generator 5.

  When the system from these pyrolyzers to distillation units is used and the pyrolysis operation of polystyrene is carried out continuously at the above-mentioned pyrolysis temperature and reduced pressure, for example, styrene having a purity of 99.7% or more is the polystyrene input 55. To 60% by weight.

  When the condenser 6 is operated for a long time, impurities gradually adhere as dirt on the surface of the cooling pipe 8 arranged inside as described above. Therefore, the oil dispersion cloth means 22 is periodically operated, and the dirt is removed by spraying oil on the surface of the cooling pipe 8. That is, when the pump 14 is operated, the oil part stored in the oil storage tank 7 is supplied from the pipe c to the spray nozzle 23, and the oil part is sprayed from the spray nozzle 23 to the cooling pipe 8 to clean the dirt. The operating time of the oil dispersion cloth means 22 may be either during the operation of the condenser 6 or when it is stopped. Further, the spraying can be performed continuously or intermittently (or intermittently).

  In order to remove the dirt from the cooling pipe 8, a method of physically scraping the dirt by the scraping means 30 may be employed. This scraping method can be used in place of or in combination with the cleaning method using the oil dispersion cloth means 22 described above.

  2A is a transverse sectional view of the scraping means 30 installed in the tank body 25 of the condenser 6, and FIG. 2B is a sectional view taken along the line AA. The scraping means 30 includes a scraping portion 32 composed of a disc having a plurality of insertion holes 31 arranged at predetermined intervals, and four driven magnets 33 fixed to the peripheral portion of the scraping portion 32 at intervals of 90 degrees. And four drive magnets 34 arranged outside the tank body 25 corresponding to the driven magnets.

  By inserting a plurality of cooling pipes 8 formed in a straight line in parallel through the insertion holes 31, the scraping portion 32 is attached to the cooling pipe 8. The four drive magnets 34 are connected to each other by a connection ring (not shown), and the connection ring is connected to a reciprocating drive means such as a manual handle or a cylinder (not shown). In that case, a guide means can be provided in order to prevent rattling of the connecting ring. The gap between the inner surface of the insertion hole 31 and the outer peripheral surface of the cooling pipe 8 is preferably set to about 1 to 2 mm.

  When connected to the manual handle, the four drive magnets 34 can be manually driven to reciprocate in synchronization with the length direction of the cooling pipe 8. When each drive magnet 34 is driven to reciprocate, each driven magnet 33 magnetically coupled thereto follows and is driven to reciprocate. Then, the scraping unit 32 is driven to reciprocate, and the surface of each cooling pipe 8 can be scraped off by the inner surface of each insertion hole 31 provided therein. When connected to the reciprocating drive means, the surface of each cooling pipe 8 is scraped off from the inner surface of each insertion hole 31 as in the case of the manual operation by remotely operating the reciprocating drive means from an operation panel or the like. Can do. The drive timing of the scraping means 30 may be either during operation or stop of the condenser 6. Further, the driving form can be either continuous or intermittent (or intermittent).

  The scraping means 30 scrapes off the dirt on the surface of each cooling pipe 8 on the inner surface of the insertion hole 31 of the scraping portion 32. For the purpose of improving the scraping effect and reducing the frictional resistance during reciprocating driving. A special contact portion can also be provided inside the insertion hole 31. In addition, when providing a contact part, the internal diameter of the insertion hole 31 is set large correspondingly.

  FIG. 3 shows an example in which a thin plate material 36 processed with metal or resin is attached as the contact portion 35 inside the insertion hole 31 by welding or adhesion. The thickness of the plate member 36 is set to be smaller than that of the scraping portion 32, and the dirt adhered to the surface of the cooling pipe 8 can be efficiently scraped by the sharp inner peripheral surface formed thereby. Further, since the contact area between the plate member 36 and the surface of the cooling pipe 8 is small, the frictional resistance in the reciprocating drive is reduced.

  FIG. 4 shows an example in which an annular brush 37 is attached to the inside of the insertion hole 31 as a contact portion 35 by adhesion or the like. The brush 37 can be formed by bundling hard plastic thin wires, metal wires, and the like, and dirt attached to the surface of the cooling pipe 8 is efficiently removed by the scraping action of the hair tips. Further, since the contact area between the tip of the brush 37 and the surface of the cooling pipe 8 is small, the frictional resistance in the reciprocating drive is reduced.

  FIG. 5 shows an example in which a large number of protrusions 38 having relatively sharp tips are continuously provided along the inside of the insertion hole 31 as the contact portion 35. The protrusion 38 can be formed integrally with the scraping portion 32, but a band provided with a large number of protrusions can be attached to the inner peripheral surface of the insertion hole 31 of the scraping portion 32 by adhesion or welding. When the scraping portion 32 is driven to reciprocate, dirt attached to the surface of the cooling pipe 8 can be efficiently scraped by the protrusions 38. Further, since the contact area between the tip of the protrusion 38 and the surface of the cooling pipe 8 is small, the frictional resistance in the reciprocating drive is reduced.

  FIG. 6 is a cross-sectional view showing another embodiment of the scraping means 30. This scraping means 30 is a scraping portion 32 constituted by a disc having a plurality of insertion holes 31 arranged at predetermined intervals, a drive shaft 39 extending vertically from the scraping portion 32 to the outside of the tank body 25, and An extension part of the drive shaft 39, that is, a reciprocating drive part 40 such as a cylinder connected to the outside of the tank body 25 is provided. And the part which the drive shaft 39 penetrates the tank main body 25 is pivotally supported by the slide bearing 41 provided with seal parts, such as a gland packing and an oil seal.

  Also in this embodiment, when the reciprocating drive unit 40 is reciprocated, the scraping unit 32 connected thereto reciprocates along the surface of the cooling pipe 8, and each inner surface of each insertion hole 31 provided in the scraping unit 32 Dirt on the surface of the cooling pipe 8 is scraped off. The driving timing and driving mode of the scraping means 30 in FIG. 6 are the same as in the example of FIG. Further, the scraping means 30 of FIG. 6 is also provided with a contact portion 35 as shown in FIGS. 3 to 5 on the inner surface of each insertion hole 31 for the purpose of improving the scraping effect and reducing the frictional resistance during reciprocating driving. it can.

  In the above embodiment, as a method for removing dirt adhering to the surface of the cooling pipe 8, a cleaning method by spraying oil or a physical scraping method is adopted, but in some cases, both may be used in combination. .

  The condensing method and the condenser of the present invention can be used for condensing pyrolysis gas in a waste polystyrene pyrolysis apparatus.

The process flow figure of the thermal decomposition system which enforces the condensation method of this invention. The figure which shows an example of the scraping means 30 installed in the tank main body 25 of the condenser 6. FIG. The figure which shows an example of the contact part 35 provided in the scraping means 30 shown in FIG. The figure which shows the other example of the contact part 35 provided in the scraping means 30 shown in FIG. The figure which shows the further another example of the contact part 35 provided in the scraping means 30 shown in FIG. The figure which shows other embodiment of the scraping means 30 shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermal decomposition apparatus 2 Thermal decomposition apparatus 3 Residue residence tank 4 Supply apparatus 5 Heated gas generator 6 Condenser 7 Oil storage tank 8 Cooling pipe 9 1st distillation apparatus

DESCRIPTION OF SYMBOLS 10 2nd distillation apparatus 11 Hopper 11a Melting part 12 Extrusion part 12a Cylindrical body 12b Rotating screw 12c Motor 13 Residue discharging apparatus 14-17 Pump 18 Pressure reducing apparatus 19 Motor

DESCRIPTION OF SYMBOLS 20 Heating part 21 Discharge valve 22 Spreading means 23 Spray nozzle 24 Cooler 25 Tank body 26 Pyrolysis gas supply part 27 Oil discharge part 28 Uncondensed gas discharge part

30 scraping means 31 insertion hole 32 scraping portion 33 driven magnet 34 drive magnet 35 contact portion 36 plate material 37 brush 38 projection body 39 drive shaft 40 reciprocating drive portion 41 slide bearing a to k piping l, m duct

Claims (6)

  In the method in which pyrolysis gas generated by pyrolysis of polystyrene is supplied to the condenser 6 and brought into contact with the surface of the cooling pipe 8 disposed inside the condenser 6 to condense, the surface of the cooling pipe 8 is contaminated. Then, a method for condensing polystyrene pyrolysis gas, characterized in that oil obtained by condensation is sprayed on the surface of the cooling pipe 8 to remove dirt.   In a method in which pyrolysis gas generated by the thermal decomposition of polystyrene is supplied to the condenser 6 and brought into contact with the surface of the cooling pipe 8 disposed inside the condenser 6 to condense, the surface of the cooling pipe 8 is contaminated. Then, a method for condensing polystyrene pyrolysis gas, wherein the dirt is scraped off by the scraping means 30 and removed.   In the condenser 6 of the pyrolysis gas generated by the thermal decomposition of polystyrene, a tank body 25 having a cooling pipe 8 disposed therein, and an oil dispersion cloth means 22 for spraying the oil obtained by the condensation on the surface of the cooling pipe 8 are provided. A polystyrene pyrolysis gas condenser characterized by comprising:   The condenser 6 for pyrolysis gas generated by the thermal decomposition of polystyrene is provided with a tank body 25 having a cooling pipe 8 disposed therein, and a scraping means 30 for scraping off dirt on the surface of the cooling pipe 8. Polystyrene pyrolysis gas condenser.   5. The scraping means 30 according to claim 4, wherein the scraping means 30 is disposed so as to be able to reciprocate along the surface of the cooling pipe 8, a driven magnet 33 provided on the scraping section 32, and the outside of the tank body 25. A polystyrene pyrolysis gas condenser having a drive magnet 34 provided in the apparatus. In Claim 4, the said scraping means 30 is the scraping part 32 arrange | positioned so that a reciprocation is possible along the surface of the said cooling pipe 8, and the drive shaft 39 extended to the outer side of the tank main body 25 from the scraping part 32. A polystyrene pyrolysis gas condenser having a reciprocating drive unit 40 connected to an extension of the drive shaft 39.

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