JPH10183137A - Decomposing device for waste plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively eliminate various factors preventing practical implementation of a decomposing treatment technology of waste plastics. SOLUTION: This decomposing device has a melting section M and reacting section Ra and Rb. The melting section M has a function for melting and liquefying waste plastics charged one by one by heating. The reacting sections Ra and Rb have functions for allowing the liquid phase polymer formed by the melting section M to cause decomposition reaction by heating. Each of the reacting sections Ra and Rb has a structure combining plural reaction units 7 having liquid-receiving channels 5 and conveying strews 6 so as to be connected as steps. The liquid polymer is allowed to serially flow down from the reaction unit 7 at the upper step to the reaction unit 7 at the lower step one by one and further allowed to perform the decomposition reaction caused by heating at each reaction unit while flowing down.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing technique for decomposing waste plastic and recovering it as fuel oil or fuel gas.

[0002]

2. Description of the Related Art Waste plastics, such as polyethylene and polystyrene, which can be oiled or gasified, are melted by heating to form a liquid-phase polymer, which is decomposed in this liquid-phase polymer to form a fuel. Oil and fuel gas can be used as well as those that are difficult to oil or gasify, such as polyvinyl chloride and polyethylene terephthalate. There are some that occur, but the former account for a much larger proportion. Therefore, waste plastic is converted into oil or gas at a reasonable cost, and collected and recovered as fuel oil or fuel gas.
Recycling is the most desirable method of treating waste plastic.

In view of the above, regarding the decomposition treatment of waste plastic, for example, JP-A-49-115157, JP-A-59-111815, and JP-A-4-18.
Various techniques have been proposed, for example, in JP-A-0878, JP-A-5-237467 and JP-A-5-263079. However, these technologies have not yet reached the stage of full-scale practical application. There are various reasons. For example, a large amount of carbon is generated during the decomposition, so that the control of the decomposition, particularly the control of the decomposition temperature, cannot be performed effectively, and the recovered material having a desired composition cannot be efficiently generated. One of them. In addition, one of the reasons is that the processing efficiency and the heating efficiency are insufficient, so that the apparatus is increased in size, and the cost of the apparatus becomes excessively large.

[0004] Further, there is another problem in the case of treating a mixed waste plastic mixed with polyvinyl chloride or the like. For example, polyvinyl chloride releases hydrogen chloride upon heating, and if this hydrogen chloride is added to the product generated by dissolving and decomposing plastics, it is difficult to separate it, and as a result, the product is cooled and cooled. If hydrogen chloride is contained in the final recycle product obtained by the process, the usefulness of the recovered material will be greatly reduced. There is also a problem that the life of the reactor, which is a factor and accounts for a large proportion of the cost of the entire apparatus, becomes extremely short, and the cost of the decomposition treatment is greatly increased.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and effectively eliminates various factors that hinder the full-scale practical use of waste plastic decomposition processing technology. The purpose of the present invention is to provide a disassembly device capable of causing the disassembly.

[0006]

SUMMARY OF THE INVENTION An apparatus for decomposing waste plastic according to the present invention includes a melting section and a reaction section. The melting section functions to melt and liquefy the sequentially supplied waste plastic by heating. On the other hand, the reaction section functions to cause a decomposition reaction by heating of the liquid-phase polymer generated by melting and liquefaction in the melting section. For this purpose, the reaction section has a structure in which a plurality of reaction units each having a liquid receiving groove and a transport screw provided in the liquid receiving groove are combined so that each liquid receiving groove is connected in a stepwise manner. ing.

[0007] The liquid-phase polymer generated by melting and liquefaction in the melting section is continuously received from the uppermost reaction unit into the reaction section. In the reaction section, the liquid-phase polymer is conveyed into the liquid receiving groove for each reaction unit in the liquid receiving groove. While being transported from one side to the other side, it is caused to sequentially flow down from the upper reaction unit to the lower reaction unit, and during this time, the liquid phase polymer in each reaction unit causes a decomposition reaction by heating. I have.

One of the features of such a decomposition apparatus according to the present invention is that the reaction section has a stepped structure composed of a plurality of reaction units, and the liquid phase polymer is caused to flow down sequentially from the upper reaction unit to the lower reaction unit. That is, a decomposition reaction occurs between them. As a result, the effective reaction area can be significantly increased without increasing the size of the entire apparatus, and the heating efficiency can be greatly increased. Therefore, the processing capacity per unit volume of the apparatus can be greatly improved. it can.

Another feature of the decomposition apparatus according to the present invention is that each reaction unit is a combination of a liquid receiving groove and a conveying screw, and the liquid phase polymer is conveyed from one side to the other side by a conveying screw in the liquid receiving groove. To cause a decomposition reaction. According to this structure,
The decomposition reaction can be caused in the liquid-phase polymer by setting the liquid-phase polymer to a shallow state in the liquid-receiving groove. As a result, the entire liquid phase polymer can be maintained at a uniform temperature at all times, and decomposition products generated from the liquid phase polymer (to be cooled down to about room temperature to become fuel oil or fuel gas) can be quickly removed from the liquid phase polymer. It is possible to eliminate the state in which the product is subjected to excessive heating and carbonized by being released.
That is, generation of carbon during decomposition can be suppressed as much as possible.

Still another feature of the decomposition apparatus according to the present invention is that a melting section is provided separately from the reaction section, and the liquid-phase polymer melted and liquefied in the melting section is decomposed in the reaction section. .
For this reason, when decomposing plastic waste mixed with non-melting plastics such as polyvinyl chloride and polyacrylonitrile, the non-melting plastics undergo dehydrochlorination during processing in the melting section. The liquid-phase polymerization of the meltable plastic can be advanced while performing the above-mentioned processes. In particular, by providing a conveying screw in the melting section, this conveying screw melts and liquefies while conveying waste plastic from one side to the other side, so that liquid phase polymer and solid residue can be efficiently separated. Can do it. As a result, it is possible to carry out the treatment without mixing hydrogen chloride and the like generated from the non-meltable plastic into the final decomposition product, and to collect solid residue from the non-meltable plastic as a solid fuel or the like. Also becomes easier.

The melting section functioning in this way can be provided in a mechanically separated form or can be provided integrally.

[0012]

Embodiments of the present invention will be described below. The decomposition apparatus according to one embodiment of the present invention has a structure in which a melting section and a reaction section are mechanically integrated as shown in FIGS. 1 and 2, and is symmetrical left and right with respect to a central melting section M. The reaction section R (Ra,
Rb).

The melting section M is formed in a screw conveyor structure. Specifically, a structure is adopted in which the conveying screws 1 having the spiral blades 1w are provided in two rows, and these are covered with the cover cylinder 2. The cover tube 2 is provided with a supply port 3 and a recovery port 4 (FIG. 2). The lower part of the cover cylinder 2 is provided with a large number of small holes, for example, so that the liquid-phase polymer generated by melting and liquefaction of the waste plastic can be naturally supplied to the left and right reaction sections R. To form.

The reaction section R includes a reaction unit 7 (7a, 7b, 7c, 7c) having a structure in which a liquid receiving groove 5 formed in a gutter shape and a transport screw 6 having a spiral blade 6w are combined.
d, 7e) are formed by combining several stations, in this example, five stations. The reaction units 7 are combined so that the respective liquid receiving grooves 5 are connected in a stepwise manner.

The melting section M and the reaction section R are hermetically covered with a common housing 8, so that
A heating zone 10 is formed below the melting section M and the reaction section R, and a vaporization zone 11 is formed above each reaction section R. The housing 8 is provided with a recovery port 12 communicating with the vaporization zone 11.

The treatment of waste plastic by such a decomposition apparatus is performed as follows. Waste plastic is continuously supplied to the melting section M through a supply port 3 from a supply hopper (not shown). The waste plastic supplied to the melting section M is transported by the transport screw 1 in the direction of the arrow (indicated by a corresponding position in FIG. 2), and is gradually melted by the supply of heating energy from the heating zone 10 during that time. -Liquefies to form a liquid phase polymer. When a non-melting plastic such as polyvinyl chloride is mixed in the waste plastic, the dehydrochlorination reaction of the polyvinyl chloride occurs simultaneously with the melting and liquefaction of the melting plastic. Note that hot air is sent into the heating zone 10 by a burner (not shown).

The hydrogen chloride generated by the dehydrochlorination reaction is recovered through a recovery port 4 by a recovery device (not shown). If necessary, a metal chloride such as aluminum chloride can be produced by using the hydrogen chloride, and the metal chloride can be used as a catalyst for a decomposition reaction in a reaction section R described later. On the other hand, the non-melting residue generated in the melting section M is transported by the transport screw 1 to the tip of the melting section M, and is recovered therefrom as a solid fuel or the like by the recovery device S.

The liquid-phase polymer produced in the melting section M flows naturally from the lower part of the cover cylinder 2 and is supplied to the reaction units 7a at the upper ends of the left and right reaction sections Ra and Rb. In the reaction unit 7a at the upper end, the liquid phase polymer is transported in the direction of the arrow (corresponding to the corresponding position in FIG. 2). During this time, the liquid phase polymer L is heated in the heating zone 1 while forming a shallow liquid depth in the liquid receiving groove 5 as shown in FIG.
Decomposition reaction occurs while receiving heating energy from zero. The liquid-phase polymer that has not been completely decomposed in the reaction unit 7a is supplied to a second-stage reaction unit 7b from a communicating portion (not shown) provided at the left end of the reaction unit 7a. In the second-stage reaction unit 7b, the liquid-phase polymer is similarly decomposed while being transported in the direction of the arrow (indicated by the corresponding position in FIG. 2), and the liquid-phase polymer that has not been completely decomposed is reacted. The communication unit (not shown) provided at the right end of the unit 7b supplies the reaction unit 7c to the third-stage reaction unit 7c.
The process is repeated up to the reaction unit 7e at the stage. During this time, substantially all of the decomposable components of the liquid phase polymer are decomposed, and the vapors generated by this decomposition are sent to a recovery device (not shown) through a recovery port 12 which fills the vaporization zone 11 and is cooled there. After that, it is recovered as oil or fuel gas. On the other hand, components that have not been finally decomposed are recovered from the fifth-stage reaction unit 7e.

The decomposition apparatus according to another embodiment of the present invention has a structure in which the melting section and the reaction section are separated mechanically. The reaction section utilizes the basic structure in the above embodiment, as shown in FIG. That is, the same reaction unit 7 as in the above embodiment
Are symmetrical left and right to form a reaction section having a structure in which each of the five sections is combined in a stepwise manner. The melting section (not shown) in this embodiment can also have the same screw conveyor structure as in the above embodiment, and the liquid phase polymer generated in this melting section is supplied from the supply port 13 to the reaction section. Will do.

[0020]

As described above, according to the present invention, the problem of the processing capacity accompanying the decomposition treatment of waste plastic, the problem of generating a large amount of carbon, and the problem of hydrogen chloride when polyvinyl chloride is mixed are effective. This can greatly advance the full-scale practical use of waste plastic recycling processing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a disassembly apparatus according to an embodiment.

FIG. 2 is a side view of the internal structure viewed from the direction of arrow DA in FIG. 1;

FIG. 3 is an explanatory diagram of a liquid phase polymer in a reaction unit.

FIG. 4 is a simplified cross-sectional view showing a main part of a decomposition apparatus according to another embodiment.

[Explanation of symbols]

 5 Liquid receiving groove 6 Transport screw 7 Reaction unit M Melting section R Reaction section

Claims (4)

[Claims] A decomposing apparatus for decomposing waste plastic to recover it as fuel oil, fuel gas, or the like, comprising a melting section for melting and liquefying sequentially supplied waste plastic by heating, and a liquid receiving groove for each. And a reaction section comprising a plurality of reaction units each having a conveying screw provided in the liquid receiving groove so that each liquid receiving groove is connected in a stepwise manner, and produced by melting and liquefaction in the melting section. Liquid phase polymer is continuously received from the uppermost reaction unit to the reaction section, and in the reaction section, the liquid phase polymer is transported from one side to the other side by the transport screw in the liquid receiving groove for each reaction unit. ,
A decomposition apparatus characterized in that the liquid phase polymer in each of the reaction units is caused to undergo a decomposition reaction by heating while the liquid phase polymer is caused to sequentially flow down from the upper reaction unit to the lower reaction unit. 2. The decomposition apparatus according to claim 1, wherein the melting section is provided integrally with the reaction section mechanically. 3. The disassembling apparatus according to claim 2, wherein the melting section includes a conveying screw, and the conveying screw melts and liquefies the waste plastic while conveying the waste plastic from one side to the other side. apparatus. 4. The decomposition apparatus according to claim 1, wherein the melting section is provided mechanically separated from the reaction section.