Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
2001-01-26
2001-12-11
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
Reexamination Certificate
active
06329496
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
In recent years, so-called chlorine-containing resins such as polyvinyl chloride and polyvinylidene chloride, so-called chlorine-containing organic compounds such as polychlorinated biphenyls, and, further, resins such as polypropylene, polyethylene and polystyrene (the so-called 3Ps) are being annually discarded as industrial waste at the rate of about 4 million tons and as nonindustrial waste collected from households at the rate of about 4 million tons. These chlorine-containing resins, chlorine-containing organic compounds and other resins discarded as industrial waste and nonindustrial waste will hereinafter be called “waste plastics” for short.
The present invention relates to a processing method for recycling such waste plastics, particularly to a processing method recycling of chlorine-containing resins, chlorine-containing organic compounds or waste plastics containing these (chlorine-containing waste plastics) that is free of problems such as corrosion of processing equipment and degradation of product quality.
BACKGROUND ART
Most waste plastics have conventionally been disposed of by incineration and as landfill. Incineration involves damage to the incinerator owing to the large amount of heat generated, and, in the case of waste plastics containing chlorine, the issue of treating the chlorine in the exhaust gas. In addition, waste plastics are not decomposed by soil microorganisms or bacteria; there is a shortage of landfill sites and an environmental load has been stocked. In recent years, therefore, a call has arisen for adoption of environment-friendly recycling technologies to avoid incineration and landfill disposal. Current methods for recycling without incineration include methods for reuse as plastic raw material and for reuse of gas components and oil components obtained by thermal decomposition as fuel and chemical raw materials.
After being used as plastic products, polyvinyl chloride, polyvinylidene chloride and other chlorine-containing resins and the like are discarded along with other plastic products without being sorted out. Waste plastics therefore inevitably include a chlorine component carried in by chlorine-containing resins and the like. Sorted waste plastics recovered from households do in fact ordinarily contain polyvinyl chloride and polyvinylidene chloride, which, when calculated as chlorine, contain several wt % of chlorine. When thermally decomposed at high temperatures, polyvinyl chloride and other chlorine-containing resins generate chlorine-type gases such as hydrogen chloride gas and chlorine gas. When chlorine-containing resins or waste plastics containing them are processed for recycling at high temperature, therefore, the problem arises of the processing equipment and the like being corroded by the chlorine-type gases generated. Owing to this, conventional recycle-processing of waste plastics has been conducted by the method of, in advance, sorting out and removing chlorine-containing resins and other chlorine-containing waste plastics or removing only the chlorine component of the waste plastics and then reusing the gas components and oil components obtained by thermally decomposing the waste plastics as chemical raw materials and fuel.
Conventional methods known for recycle-processing waste plastics include, for example, the method of using a blast furnace, which is one process in iron- and steel-making, and utilizing waste plastics as an iron ore reducing agent (JP-B(examined published Japanese patent application)-51-33493). Various development efforts have recently been made in order to effectively implement this method (e.g., JP-A(unexamined published Japanese patent application)-9-170009, JP-A-9-137926, JP-A-9-178130, JP-A-9-202907, and Japanese Patent No. 2,765,535).
In the case of processing waste plastics with a blast furnace, decrease in blast furnace productivity and the effect of the chlorine component inevitably contained in the waste plastics must be taken into account.
Specifically, when the blast furnace is charged with an amount of waste plastics exceeding 10 kg per ton of pig iron produced, deactivation of the blast furnace core is induced to markedly degrade pig iron productivity. In the case of processing waste plastics with a blast furnace, therefore, the amount of waste plastics processed has conventionally been limited to 10 kg per ton of pig iron.
Moreover, waste plastics discarded as industrial waste and nonindustrial waste include so-called chlorine-containing resins, such as polyvinyl chloride and polyvinylidene chloride, and so-called chlorine-containing organic compounds such as polychlorinated biphenyls. Waste plastics, both industrial and nonindustrial, therefore on average include chlorine at about several wt % to several tens of wt % and, even after sorting, include chlorine at an average of several wt %. When waste plastics including such chlorine are charged into the blast furnace as they are, chlorine-type gases such as chlorine and hydrogen chloride are generated during thermal decomposition of the waste plastics, causing a problem of corrosion of the shell, stave coolers and the like of the blast furnace body and a problem of corrosion of furnace-top waste gas equipment and the furnace-top electrical equipment. In the case of processing waste plastics in the conventional blast furnace, therefore, there has been conducted pre-processing, such as in advance sorting out and removing chlorine-containing resins, chlorine-containing organic compounds and other chlorine-containing waste plastics or removing only the chlorine component of the waste plastics, and the waste plastics have been charged in the blast furnace after having their chlorine content reduced to 0.5 wt % or below.
Methods have also long been known for recycle-processing waste plastics by thermal decomposition using, instead of a blast furnace, a coke oven, which is one process in the same iron- and steel-making (JP-B-49-10321 and JP-A-59-120682). Recently, various development efforts have been made regarding methods for efficiently processing waste plastics, most notably waste plastic charging methods that take coke strength into account (e.g., JP-A-8-157834). In these cases, instead of coal, waste plastics, which are also hydrocarbons, are charged into the coke oven to obtain coke, tar, light oil and fuel gas by dry distillation. A coke oven can thus also be used as a waste plastic recycling facility.
However, in the case where a coke oven is used to process waste plastics, as in the case of processing in a blast furnace, it is necessary to give consideration to decrease in coke productivity caused by the charging of waste plastics, the effect on the equipment of the corrosion etc. by chlorine included in the waste plastics, and the effect on product quality.
Regarding product quality, when, for example, a blend of waste plastics and coal is charged into a coke oven, the amount of waste plastics charged into the coke oven is expected to be 10 kg per ton of coal, because the coke quality deteriorates sharply when the waste plastic charging amount exceeds 10 kg per ton of coal.
Regarding the effect of chlorine in the waste plastics, when waste plastics containing around several wt % of chlorine are charged into a coke oven as they are, a possibility exists of the chlorine component remaining in the coke after the waste plastics carbonize. Moreover, there is not only a danger that the chlorine-type gases produced by thermal decomposition of the waste plastics may mix into the tar, light oil and coke-oven gas that are byproducts at the time of coke production but also a danger that the generated chlorine-type gases will remain in the oven and/or corrode the oven body and the waste gas treatment system pipes. Conventionally, therefore, processes have bee effected for thermally decomposing only the chlorine component of the waste plastics before charging in the waste elastics in the coke oven, as taught by JP-A-7-216361, or for removing chlorine-system resins and other chlorine-containing waste plastics
Kato Kenji
Komaki Ikuo
Uematsu Hiroshi
Boykin Terressa M.
Kenyon & Kenyon
Nippon Steel Corporation
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