JP2004292629A - Method for dechlorinating waste plastic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for dechlorinating waste plastics capable of removing chlorine from the chlorine-containing waste plastics in high removing efficiency and easy to treat the thus removed chlorine. <P>SOLUTION: This method for dechlorinating the waste plastics comprises heating the chlorine-containing waste plastics together with iron or an iron compound in a coal tar-based oil to form an iron chloride and then separating the iron chloride from the resultant waste plastics or a decomposed product thereof. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a chemical recycling method for waste plastic. More specifically, the present invention relates to a method for fixing and removing chlorine from waste plastic containing chlorine and recovering a chlorine-free compound.
[0002]
[Prior art]
In recent years, waste plastics have been actively recycled, for example, by blowing waste plastics into a blast furnace for the purpose of a reducing agent of iron ore and a heat source for a reduction reaction, or by recycling coal into a coke oven. Formulation has been implemented. However, waste plastic collected as municipal solid waste contains a considerable amount of chlorine, and if put into a blast furnace or a coke oven as it is, hydrogen chloride and the like are generated, causing various problems including corrosion of equipment.
[0003]
Therefore, pretreatment for removing chlorine has been performed. At this time, chlorine is generally present as a plastic such as vinyl chloride and vinylidene chloride, and therefore, with the currently employed technology, hydrocarbons, that is, a part of waste plastics, are also removed together with chlorine. Since waste plastics containing a large amount of chlorine have no use, they are usually landfilled, and there are problems such as a decrease in the recycling rate and a tight landfill.
[0004]
On the other hand, technologies for removing chlorine from chlorine-containing waste plastics are being developed. For example, petroleum-based heavy oil, coal-based heavy oil are used as waste plastics and alkali metal compounds or alkaline earth metal compounds as chlorine fixing agents ( There is a method of mixing calcium hydroxide or the like and performing heat treatment at 350 to 460 ° C. in a non-oxidizing atmosphere (see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-10-72587 [0006]
In addition, chlorine-containing waste plastic is immersed in coal tar heavy oil, etc., and heated to 200 to 400 ° C. to dechlorinate the waste plastic, thereby gasifying and removing chlorine in the form of hydrogen chloride or the like. Is also known (see Patent Document 2).
[0007]
[Patent Document 2]
JP-A-11-199874 [0008]
[Problems to be solved by the invention]
However, in the method using calcium hydroxide or the like as a chlorine fixing agent, separation of generated calcium chloride from waste plastic is not easy, and a large amount of waste plastic or heavy oil adheres to the separated calcium chloride. Therefore, the processing was a problem. In addition, even if this separated calcium chloride was used as a fuel, the chlorine concentration of the incinerated ash was high because calcium chloride was stable, and this could not be used as a raw material for cement or the like.
[0009]
On the other hand, the method of gasifying and removing chlorine by heating has a problem that the chlorine removal rate is not sufficient and the amount of chlorine remaining in the treated waste plastic is considerable.
[0010]
An object of the present invention is to provide a method for dechlorinating waste plastics, which can remove chlorine from chlorine-containing waste plastics at a high removal rate and can easily treat the removed chlorines.
[0011]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, by using iron or an iron compound as a chlorine fixing agent and heating the chlorine-containing waste plastic together with it in coal tar oil, the waste plastic It has been found that chlorine can be removed at a high removal rate from iron and iron chloride produced thereby has good separability and can be separated with little adhesion of waste plastic or coal tar oil. This iron chloride can be easily separated into iron and hydrochloric acid by roasting, so that the treatment was also easy.
[0012]
The present invention has been made on the basis of these findings, and heats chlorine-containing waste plastic with iron or an iron compound in coal tar-based oil to produce iron chloride, and then converts the iron chloride to waste plastic. Alternatively, the present invention relates to a method for dechlorinating waste plastics, which is separated from its decomposition products.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Although the type of chlorine-containing waste plastic to which the present invention can be applied is not limited, for example, waste automobiles, waste home appliances, PVC-containing building waste, gas pipes and other waste, waste OA equipment, resin-coated wire, and the like are applicable. is there. The chlorine-containing plastics contained therein are typically vinyl chloride resins. In addition, there are vinylidene chloride resins, chlorinated polyethylenes, chlorinated polypropylenes, and the like, and foamed resins are also included. In addition to chlorine-containing synthetic resin, various types of plastics, various steel plates, steel pipes, steel bars such as steel bars, and other metals such as aluminum, copper, zinc, lead, etc. I have. In the present invention, recovery of these metals is also possible.
[0014]
The form of the waste plastic can be selected according to the size of the processing furnace to be used. Although it is possible to treat the waste as it is, it is also possible to crush and cut it to an appropriate size, for example, about 1 to 100 mm × 1 to 100 mm. It is also applicable that the waste plastic is cut to about 5 to 100 mm of the resin-coated wire rod, and the one that is wound in a coil shape can be treated by continuously immersing it in the molten liquid and washing it. is there.
[0015]
The coal tar oil may be a coal distillate or a fraction obtained by distilling the coal tar. In addition to the above, oil produced in petroleum refining can also be used. The amount of the coal tar oil used may be about 50 to 1000 parts by weight, preferably about 100 to 200 parts by weight, based on 100 parts by weight of the waste plastic.
[0016]
The iron or iron compound used in the present invention has a chlorine fixing action, that is, it can react with chlorine, particularly hydrogen chloride, to be converted to iron chloride.For example, in the case of iron oxide, ferrous oxide, oxide Examples thereof include ferric iron and triiron tetroxide, and any one of them may be used, or a mixture thereof may be used. The iron compound containing iron oxide as a main component is not particularly limited, and examples of the iron compound that can be used at low cost include converter dust or iron ore released during blowing in a converter of an ironworks.
[0017]
Considering the catalytic action of lightening waste plastics, iron oxide obtained by calcining an iron compound having a sulfate group is particularly preferable. Examples of the iron compound having a sulfate group include FeSO ₄ , Fe ₂ (SO ₄ ) ₃ , and Fe (NH ₄ ) (SO ₄ ) ₂ . Further, two types of iron compounds having a chlorine fixing effect and calcined products of a sulfate group-containing iron compound having a remarkable catalytic effect (iron oxide main component) may be added.
[0018]
As a condition for producing iron oxide from an iron compound having a sulfate group, heating may be performed at 750 to 1000 ° C. for about 1 to 10 hours in an oxygen-containing atmosphere, usually air.
[0019]
Further, the iron oxide of the present invention may be a precursor generated by heating in coal tar oil. Examples of such a precursor include iron hydroxide, iron nitrate, and iron sulfate.
[0020]
The particle size of the iron oxide is not particularly limited, but is preferably a fine one, for example, an average particle size of 500 μm or less, particularly preferably 50 μm or less. Although the lower limit of the average particle size is not particularly limited, it is 0.5 μm or more, preferably 5 μm or more from a practical viewpoint.
[0021]
The amount of iron or iron compound to be added is suitably about 0.5 to 100, preferably about 1 to 10 as an atomic ratio of iron in the iron or iron compound to chlorine in the chlorine-containing waste plastic.
[0022]
After the chlorine-containing waste plastic is immersed in coal tar oil and iron oxide is added, it is heated to perform dechlorination of the chlorine-containing waste plastic. The temperature and time of this heat treatment are determined so that the dechlorination proceeds sufficiently, and this depends on the type and amount of plastic used, but is about 200 to 400 ° C, preferably about 250 to 350 ° C, more preferably 280. At about 320 ° C., about 0.1 to 1.0 hour, preferably about 0.3 to 0.6 hour is appropriate. At this time, the decomposition behavior differs depending on the type of the plastic, but it generally melts and dehydrochlorination occurs.
[0023]
In the present invention, the dechlorinated waste plastic can be separated as it is and used as a fuel or the like, but it is preferable to lighten the waste plastic in order to enhance the separation from iron chloride. This lightening is preferably carried out in the presence of a catalyst. Examples of the catalyst having a lightening effect include iron oxide having the chlorine fixing effect, in particular, iron oxide obtained by calcining an iron compound having a sulfate group, a Co-Mo-based catalyst, and a Ni-W-based catalyst. it can. For this lightening, it is essential to use a hydrogen gas atmosphere.
[0024]
The lightening reaction may proceed at the same time as the dechlorination, or any of them may precede. For example, an atmosphere such as a hydrogen gas or a gas containing hydrogen, for example, a coke oven gas (containing about 54% by volume of hydrogen) may be used from the beginning, or the heating process may be performed in a plurality of stages and hydrogen gas may be introduced into the second and subsequent stages. May be. Regarding the type of the reactor, either a batch type or a continuous type may be used. In the continuous type, a slurry bed is particularly suitable.
[0025]
The mixture of waste plastic and oil that has undergone the heating step with hydrogen gas introduced is lightened, which reduces its viscosity and easily separates and removes iron compounds containing high-concentration iron chloride using a high-temperature centrifuge. it can. Because of its high concentration, it is not bulky, so it can be landfilled (reduced in volume compared to the original waste plastic), or it can be roasted and separated into iron and hydrochloric acid for recycling.
[0026]
On the other hand, the obtained lightened hydrocarbons are chlorine-free and therefore can be used as good fuels and also used as chemical raw materials.
[0027]
【Example】
Using a 300 ml electromagnetic induction stirring type autoclave, 12 g of waste plastic containing chlorine (analytical value of 4.1% by weight) derived from municipal waste, 18 g of coal-based tar, and discharged from a steelmaking converter as a chlorine fixing agent. 5.5 g of dust (iron oxide content 70%) was charged and heated at 250 ° C. for 1 hour. After cooling, the addition of _{Co-Mo / SiO 2 -Al 2} O 3 catalyst 1.8g opens the lid, the hydrogen gas was introduced 3 wt% relative to the total amount of chlorine-containing waste plastics and coal tar, 430 ° C., The reaction was performed at 5 MPa for 1 hour.
[0028]
The contents were recovered, and dust containing iron chloride was separated by a centrifugal separator while heating to 200 ° C. The burning loss corresponding to the content of organic substances (hydrocarbons) in the separated dust was 3.1% by weight, and 23.6 g of a lightened waste plastic / tar mixture (hydrocarbons) was obtained. As a result of analysis, it was 10 ppm or less.
[0029]
It can be seen that a large amount of hydrocarbons having extremely low chlorine content was obtained, and most of the added chlorine fixing agent and generated iron chloride were recovered.
[0030]
【The invention's effect】
As described above, according to the present invention, there is an effect that an extremely good dechlorination technique can be provided.
[Brief description of the drawings]
FIG. 1 is an explanatory view schematically showing one embodiment of a dechlorination technique of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Mixing process 2 ... Heating process 3 ... Heating process 4 ... Separation process 11 ... Waste plastic 12 ... Oil 31 ... Hydrogen containing gas 41 ... Iron chloride 42 ... Lightening waste plastic / oil mixture

Claims (2)

The waste plastic containing chlorine is heated by heating the waste plastic containing chlorine together with iron or an iron compound in a coal tar oil to produce iron chloride, and then separating the iron chloride from the waste plastic or a decomposition product thereof. Chlorine method 2. The method for dechlorinating waste plastic according to claim 1, wherein the iron or iron compound is iron oxide and obtained by calcining an iron compound having a sulfate group.

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