JPH10130658A - Continuous method for converting plastic waste into oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous method for converting plastic wastes into an oil, whereby the formation of carbon can be effectively prevented, and the decomposition can effectively be controlled to efficiently recover an oil product of desirable quality. SOLUTION: This method comprises heating and melting plastic wastes to form a liquid-phase polymer and decomposing and vaporizing the liquid-phase polymer to recover the formed oil. In this method, the decomposition and vaporization of the liquid-phase polymer is performed while a film F is being formed on one surface of a heating plate 2 heated by applying thereto heat energy from the other side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for thermally decomposing waste plastics to convert the waste plastics into oil, and more particularly to an oil conversion technique for efficiently obtaining an oily product having a composition highly suitable as fuel oil for industrial burners and the like. .

[0002]

2. Description of the Related Art A variety of ideas and apparatus configurations have already been proposed for liquefying waste plastics. However, the fact is that there is still nothing that enables practical operation.

[0003] One of the major factors that prevents conventional oil-forming technology from being put into practical use is the large amount of carbides generated during the decomposition process. In other words, when a large amount of carbon is generated, it adheres to the inner wall of the decomposition reactor and inhibits heat conduction, making it difficult to stably control the decomposition reaction,
As a result, it is not possible to efficiently obtain a recovered material having a desired composition, requires a great deal of labor and time for maintenance of the apparatus, and further increases the risk of the reaction process, thus requiring a large number of monitoring personnel. Become. As a result, the economy is poor, and it cannot be linked to the operation as a practical machine.

[0004] Further, the inability to control the composition of the obtained recovered material sufficiently is a factor that hinders practical operation. That is, it is practically most desirable that the recovered material has a component composition suitable as a fuel oil for an industrial burner or the like. However, in the prior art, the recovered product is degraded due to the incorporation of undecomposed polymer or carbon, or conversely, excessive cracking increases the gasoline yield, thereby deteriorating its suitability as a fuel oil. However, it is not possible to increase the added value of the collected material, which is indispensable for the practical operation of the system, for example, and it cannot be linked to the operation as a practical system.

[0005] As described above, in order to make the waste plastic oil liquefaction technology a practical system, it is essential to prevent the generation of carbon and control the oil quality of the recovered material. For this purpose, it is necessary to have accurate knowledge of the mechanism of polymer decomposition and carbon generation and appropriate measures based on this, but none of the conventional technologies are inadequate in these respects. It is considered that the generation of carbon could not be effectively prevented, and the control of oil quality of the recovered material could not be effectively performed.

[0006] From such a viewpoint, the inventor of the present application has conducted deeper research and analysis on the mechanism of polymer decomposition and carbon generation, and has obtained the following findings. The first is the liquefaction of the polymer, which involves melting the solid polymer of the waste plastic into a liquid-phase polymer, and then further heating the liquid-phase polymer to break the higher-order structure of the polymer into a lower-order structure. In this state, decomposition occurs for the first time in this state, and when decomposition occurs, products with various molecular weight distributions according to the decomposition temperature etc. are generated, and by cooling this, recovery with a certain oil quality It comes through a series of processes of obtaining things. The most important factor affecting the oil quality of the recovered product is the control of the secondary cracking reaction of the light oil component of the cracked product. Control is the most important factor for recovered oil quality.

[0007] Next, most of carbon is generated when a vapor generated by decomposition, particularly a low molecular weight vaporized material is further heated excessively. However, all of the conventional techniques carry out the treatment under such a condition that the vaporized material cannot escape the excessive heating, and this is the largest cause of the mass generation of carbon. Therefore, it is most important that the vapor generated from the liquid phase polymer is quickly separated from the liquid phase polymer or the like to eliminate the state of being exposed to excessive heating, and that the gradient of the heating temperature in the liquid phase polymer is made as small as possible.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made based on the above-mentioned findings, and effectively prevents the generation of carbon in the liquefaction of waste plastics and recovers desirable oil quality. It is an object of the present invention to effectively perform decomposition control for efficiently obtaining a product.

[0009]

According to the present invention for achieving the above objects, waste plastics are heated and melted to form a liquid phase polymer, and oily substances are recovered by decomposition and vaporization of the liquid phase polymer. Regarding the continuous plasticization method of waste plastic, the liquid phase polymer is decomposed and vaporized while forming a thin film on the other side of the heating plate being heated by applying heating energy from one side. ing.

The feature of this continuous oiling method is that a thin film of preferably 1 mm or less is formed on the liquid-phase polymer on the heating surface of the heating plate having a two-dimensional spread, and the thinned liquid-phase polymer is heated. Is decomposed and vaporized by the supply of heating energy from one side. For this reason, the liquid-phase polymer which is going to decompose and vaporize comes into close contact with the heating source in a thin film, and the whole can always be kept at a uniform temperature. That is, the temperature gradient in the liquid-phase polymer can be made very small to the extent that it is substantially absent. In addition, vaporized substances generated from the liquid-phase polymer can be quickly released from the liquid-phase polymer to eliminate the state in which the vaporized substance is exposed to excessive heating,
The generation of carbon can be effectively prevented. Furthermore, the heating efficiency for the liquid phase polymer for decomposition and vaporization is significantly increased, and the decomposition efficiency can be greatly improved. As a result, it becomes possible to effectively control the decomposition reaction of the polymer, and it is possible to efficiently recover a high-quality oily product having a desirable oily quality. In addition, the burden on maintenance of the oiling device can be greatly reduced, and furthermore, the monitoring of the reaction process is substantially unnecessary, and unmanned operation can be performed.

[0011] The heating plate used in the above continuous oiling method can have various shapes, and typical shapes include a cylindrical shape, a conical shape, an inverted conical shape, and a flat plate shape. In the case of a cylindrical shape, the lower part of the cylindrical heating plate is immersed in the pool of the liquid-phase polymer, and in this state, the thin film of the liquid-phase polymer is heated on the heating surface of the heating plate by rotating the cylindrical heating plate. Is formed. The heating energy is supplied from inside the cylindrical heating plate. This method is a cyclic process in which the liquid phase polymer thin film that has not been completely decomposed is returned to the liquid phase polymer pool again. Therefore, the heating plate can be used efficiently and is particularly suitable when the processing amount is large. However, this method requires a movable structure, which complicates the apparatus. The method using a conical or inverted conical heating plate is less efficient than a cylindrical heating plate, but can obtain a relatively large heating surface and does not require a movable structure, thus simplifying the apparatus. . This is suitable for moderate throughput. The method using a flat heating plate is possible with the simplest apparatus and is suitable for small-scale processing.

As described above, in the present invention, it is the most important requirement that the liquid phase polymer forms a “thin film” on the heating plate, but this “thin film” is directly formed by the liquid phase polymer itself. It means a film formed thinly on a heating plate.
Therefore, the "thin film" of the liquid phase polymer in the present invention is:
For example, as known in JP-A-8-41464,
This is different from a state in which a granular heating medium is used for heating and dispersing the polymer, and the liquid phase polymer mixed with the granular heating medium is moved on a heating plate.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. In the first embodiment, an oiling reactor as shown in FIGS. 1 and 2 is used. This oiling reactor has a structure in which an outer cylinder 1 and a cylindrical heating plate 2 are combined so as to form a reaction chamber 3 therebetween. The cylindrical heating plate 2 has conveying blades 4 on its outer periphery and gears 5 and 5,
It is designed to be rotated by a drive source 6 via the gears 5, 5. Further, the inside of the cylindrical heating plate 2 forms a hot air path 7, and the hot energy is blown into the cylindrical heating plate 2 by a burner 8 to receive heating energy. A receiving port 9 is provided in the outer cylinder 1, and waste plastic is supplied to the reaction chamber 3 from the receiving port 9 in the form of a solid polymer or a liquid polymer melted by a pretreatment device (not shown). The polymer supplied to the reaction chamber 3 is continuously conveyed in the direction of the arrow X in the reaction chamber by the rotation of the cylindrical heating plate 2, and is heated and decomposed and vaporized during the conveyance, and the vaporized substance is transported. It is sent out from the outlet 10 and is cooled by a collecting device (not shown) and collected as oil. The non-decomposable components contained in the liquid phase polymer are taken out from the outlet 11 and collected as solids.

In the reaction chamber 3, as shown in FIG.
Is formed in a state where the lower part of the cylindrical heating plate 2 is immersed therein. Then, the cylindrical heating plate 2 scrapes up the liquid-phase polymer with its rotation, and forms a thin film F of the liquid-phase polymer having a thickness of about 0.5 mm on the outer peripheral heating surface 2s. The thin film F is heated by receiving the heating energy from the hot air passage 7 and is decomposed and vaporized. The vapor generated by this is sequentially discharged from the vapor discharge port 10 in FIG. 1 while filling the entire reaction chamber 3 except for the shallow liquid-phase polymer pool L.

In the second embodiment, an oiling reactor as shown in FIG. 3 is used. This oiling reactor has a gently inclined conical heating plate 22 inside a tank housing 21 formed in a closed shape. A cylindrical heating chamber 23 is provided below the conical heating plate 22, and by heating a burner 24 in the heating chamber 23, heating energy is supplied to the conical heating plate 22. A supply port 25 is provided in the tank housing 21. From this supply port 25, a liquid phase polymer is supplied to the apex of the conical heating plate 22 as shown by a thick arrow, and this liquid phase polymer is seen in FIG. The heating surface 22 s of the conical heating plate 22 is, for example, 0.5 m
It flows down while forming a thin film F having a thickness of about m. Then, it is heated and decomposed and vaporized in this flow, and this vaporized substance is sent out from a vaporized substance outlet 26 provided in the tank housing 21 as shown by an arrow, and is cooled by a recovery device (not shown) and collected as oily substance. Is done. On the other hand, the non-decomposable components contained in the liquid-phase polymer are sent out from a take-out port 27 provided below the tank housing 21 to a screw conveyor 28 for conveyance, and are collected as solids.

In the third embodiment, an oiling reactor as shown in FIG. 5 is used. The oiling reactor has an inverted conical heating plate 31, and a liquid phase polymer supplied from a supply port 33 provided in a tank housing 32 as indicated by a thick arrow heats the inverted conical heating plate 31. It flows down while forming a thin film similar to that described in the second embodiment on the surface 31s. Then, the liquid phase polymer of the thin film is heated and decomposed and vaporized by the heating energy supplied by the burner 34 of the heating chamber 33, and the vaporized substance is sent out from a vaporized substance outlet 35 provided in the tank housing 32, and is not shown. And collected as oil. A take-out cylinder 36 is connected to the center of the inverted conical heating plate 31, and a non-decomposable component or undecomposed polymer contained in the liquid phase polymer is transferred from the take-out cylinder 36 to a screw conveyor 38 for conveyance. To be sent out. The undecomposed polymer can be decomposed by heating the screw conveyor 38 as needed.

In the fourth embodiment, an oiling reactor as shown in FIG. 6 is used. The oiling reactor has a flat heating plate 42 that is gently inclined inside a tank housing 41 that is formed in a closed state. The liquid-phase polymer is supplied to the heating surface 42s of the flat heating plate 42 from a supply port 43 provided in the tank housing 41 as indicated by a thick arrow. This liquid-phase polymer forms a thin film similar to that described in the second embodiment on the heating surface 42s, and is heated and decomposed and vaporized by the heating energy supplied by the burner 45 of the heating chamber 44. The gas is sent out from a vaporized material outlet 45 provided in the tank housing 41, cooled by a collecting device (not shown), and collected as oily material. On the other hand, the non-decomposable components contained in the liquid phase polymer are sent out from a take-out port 46 provided below the tank housing 41 to a screw conveyor 47 for conveyance, and are collected as solids.

FIG. 7 shows an oiling reactor of the same type as the oiling reactor of FIG. 3 used in the second embodiment. In this oiling reactor, an exhaust pipe 52 is provided at the top of a conical heating plate 51, and the exhaust pipe 52 allows the heating chamber 2 to be heated.
3. It is designed to be able to collect high-temperature exhaust gas from the fuel cell. By collecting the exhaust gas from the top of the conical heating plate 51 in this manner, the pressure loss of the exhaust gas can be reduced, and the heat energy of the exhaust gas, that is, the waste heat can be reused more efficiently. The waste heat is used, for example, as a heating source when reducing the volume of waste plastic prior to treatment in the oiling reactor. Since the other structure is the same as that of the oiling reactor shown in FIG. 3, common portions are denoted by the same reference numerals and description thereof will be omitted.

[0019]

As described above, according to the present invention, the generation of carbon can be effectively prevented, and at the same time, the decomposition reaction can be effectively controlled, so that a high-quality oily product having a desirable oil quality can be efficiently produced. Can be recovered.

[Brief description of the drawings]

FIG. 1 is a simplified cross-sectional view of a reactor for oil conversion used in a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line SA-SA in FIG.

FIG. 3 is a simplified cross-sectional view of a reactor for oil conversion used in a second embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional view of a heating plate in the oil conversion reactor of FIG. 3;

FIG. 5 is a simplified cross-sectional view of a reactor for oil conversion used in a third embodiment of the present invention.

FIG. 6 is a simplified cross-sectional view of a reactor for oil conversion used in a fourth embodiment of the present invention.

FIG. 7 is a simplified cross-sectional view of an oiling reactor of the same type as the oiling reactor of FIG.

[Explanation of symbols]

 2,22,31,42 …… Heating plate F …… Liquid phase polymer thin film

Claims (4)

[Claims] 1. A continuous plasticizer for waste plastics in which waste plastics are heated and melted to form a liquid-phase polymer, and an oil is recovered by decomposition and vaporization of the liquid-phase polymer. A method for continuously oiling waste plastics, wherein decomposition and vaporization are caused while forming a thin film on a liquid phase polymer on the other surface of the heating plate being applied and heated. 2. The continuous oil-forming method according to claim 1, wherein a cylindrical heating plate is used as the heating plate. 3. The continuous oiling method according to claim 1, wherein a conical or inverted conical heating plate is used as the heating plate. 4. The continuous oiling method according to claim 1, wherein a flat heating plate is used as the heating plate.