JP3682115B2 - Waste plastic processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating waste plastics, wherein polyethylene, polypropylene and polystyrene (hereinafter referred to as 3P) are separated from waste plastics in general waste and used as a clean fuel together with the extraction solvent.
[0002]
[Prior art]
Waste plastic is about 70% plastic, about 20% foreign matter such as metal, porcelain, paper, etc., and about 10% moisture. The waste plastic contains polyethylene (PE), polystyrene (PS), polypropylene ( PP) is about 60 to 80%, vinyl chloride and others are about 15%, and in addition, thermosetting resins and the like are included.
For example, in Japanese Patent Laid-Open No. 7-18114, it is proposed to generate and recover oil such as gasoline, kerosene, and light oil by using an oiling facility that melts and decomposes the waste plastics for thermal decomposition and distillation. ing.
[0003]
[Problems to be solved by the invention]
However, recovering oil such as gasoline, kerosene, and light oil from waste plastic using the above-mentioned oil production equipment is relatively expensive due to the complexity of the equipment. There is a problem that the manufacturing price is higher than gasoline, kerosene and light oil.
On the other hand, a large amount of waste oil such as waste engine oil, waste lubricant oil, waste cleaning oil, waste solvent, etc. is generated, and these are subjected to combustion treatment in a rotary kiln equipped with a post-combustion furnace, or combustion treatment by spraying. This is the current situation.
The present invention has been made in view of such circumstances, and uses 3P contained in waste plastic as a solvent by using a non-valued oil such as waste oil or a relatively inexpensive hydrocarbon oil as an extraction solvent. It aims at providing the processing method of the waste plastic utilized as a fuel.
[0004]
[Means for Solving the Problems]
The method for treating waste plastic according to claim 1, which meets the above-mentioned object, mixes and heats an extraction solvent comprising waste plastic and hydrocarbon, and selectively extracts 3P contained in the waste plastic into the solvent. After the solid-liquid separation is performed, the solid component is separated, and the mixed solution composed of the remaining extraction solvent and 3P is used as the fuel.
Further, the method for treating waste plastic according to claim 2 uses waste oil such as waste engine oil, waste lubricating oil, waste cleaning oil, waste solvent, etc. as the extraction solvent in the method according to claim 1.
[0005]
In the method for treating waste plastic according to claims 1 and 2, 3P contained in the waste plastic dissolves when the waste plastic is put in an extraction solvent and heated at an appropriate temperature (about 100 to 200 ° C.). On the other hand, metals, earth and sand, thermosetting resin, polyvinyl chloride, etc. contained in the waste plastic do not dissolve in the extraction solvent made of hydrocarbon.
Then, if solid content is removed using a solid-liquid separator such as a centrifuge, a screen, a screw press, or a filter press, a mixed solution of 3P and the extraction solvent is obtained. If this is used as a liquid fuel as it is, it can be used as a clean fuel that is easy to handle. Here, examples of the use of the fuel include boiler fuel, power generation fuel, blast furnace blowing fuel, and the like.
In particular, in the method for treating waste plastic according to claim 2, since waste oil is used as the extraction solvent, waste oil can also be treated and used as fuel, so that waste plastic and waste oil are recovered as a heat source. it can.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
FIG. 1 is a flowchart showing a waste plastic processing method according to an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between temperature and 3P recovery rate.
[0007]
As shown in FIG. 1, waste oil consisting of waste plastic and waste engine oil or waste lubricant oil is prepared. Waste plastic is cut into 5-60 mm square fluffs in advance. About 70% by weight of 3P is mixed in the waste plastic, and this waste plastic and waste oil are put into the dissolution tank 10. The dissolution tank 10 is provided with a stirring blade and a heating means so as to be uniformly heated in a range of 100 to 200 ° C. while mixing waste oil and waste plastic inside.
[0008]
The ratio of waste plastic to waste oil is preferably about 1 to 30 (more preferably about 3 to 10) of waste oil by weight with respect to waste plastic 1. When the ratio of waste oil is less than 1, this increases the viscosity in the dissolution tank 10 and requires a large stirring force, which is not efficient. There is no particular upper limit, and the larger the liquid, the easier it is to handle the mixed liquid as a pure liquid.
[0009]
As described above, when waste oil and waste plastic are put into the dissolution tank 10 and stirred, 3P in the waste plastic is dissolved in the waste oil mainly composed of hydrocarbons. This state is shown in FIG. 2, and the water in the waste plastic evaporates by heating at about 100 ° C., and 3P dissolves in the waste oil. When the temperature exceeds 170 ° C., hydrogen chloride begins to be generated, but the temperature is low in the low temperature range. As a temperature for dissolving 3P in waste oil, heating to 160 to 180 ° C. is more preferable because the oil contains little chlorine.
[0010]
By the above processing, a mixed liquid of 3P in waste plastic and waste oil and a solid content (extraction residue) in the waste plastic can be formed, and this is put into the separation tank 11 to perform solid-liquid separation. As the solid-liquid separation means, it is most efficient and preferable to use a centrifuge, but in some cases, a screen using a fine screen, gravity sedimentation, a filter press or the like may be used.
Through the above treatment, a mixed liquid of 3P in waste plastic and waste oil, that is, fuel oil, is produced, and the solid content is disposed of or gasified and reused as energy in the system to further reduce the volume.
[0011]
In the above embodiment, waste oil is used as the extraction solvent. However, for example, the present invention can be applied to the case where relatively inexpensive oil such as A, B, C heavy oil is used as the extraction solvent.
Moreover, in the said embodiment, although the waste plastic was made into the fluff at 5-60 mm square, rod shape and round shape may be sufficient and this invention is not limited to the shape and magnitude | size. Furthermore, as what is extracted by this invention, the thermoplastic resin except organic chlorine compounds, such as PVC and PVDC, may be contained besides 3P.
In addition, if the liquid mixture manufactured by the above embodiment is burned, it has a calorific value of about 8000 to 10,000 Kcal / liter and can be used as fuel instead of heavy oil.
[0012]
【The invention's effect】
As is apparent from the above description, the methods for treating waste plastics according to claims 1 and 2 can use polyethylene, polypropylene, and polystyrene contained in the waste plastic as a fuel together with an extraction solvent made of hydrocarbons.
In addition, since the fuel oil produced by the method of the present invention is obtained by dissolving polyethylene, polypropylene, and polystyrene in the extraction solvent, it becomes a clean fuel that does not contain excess materials. Therefore, boiler fuel, fuel for blast furnace injection Can be used effectively. For this reason, depending on the case, the amount of fuel used, for example, A, B, C heavy oil, etc. used as fuel can be reduced, and waste plastic can be recycled at the same time.
Furthermore, the solid content separated by the above treatment is disposed of in landfill if it is not treated in the system. However, since the volume of waste plastic is greatly reduced compared to landfill disposal, the life of the landfill site can be extended. it can.
In particular, since the waste plastic processing method according to claim 2 uses waste oil as the extraction solvent, the waste oil can be effectively used.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a waste plastic processing method according to an embodiment of the present invention.
FIG. 2 is a graph showing the relationship between temperature and 3P recovery rate.
[Explanation of symbols]
10 Dissolution tank 11 Separation tank

Claims (2)

After mixing and heating the extraction solvent consisting of waste plastic and hydrocarbon, extracting polyethylene, polypropylene and polystyrene contained in the waste plastic, solid-liquid separation is performed to separate the solids, and the remaining polyethylene, polypropylene and Waste plastic treatment method using a mixture of polystyrene and extraction solvent as fuel. The waste plastic processing method according to claim 1, wherein waste oil containing one or more of waste engine oil, waste lubricant oil, waste cleaning oil, and waste solvent is used as the extraction solvent.

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