Technology for treating waste plastics using coking processes

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1. Technical principle: Existing mature coking processes and equipment are utilized to process waste plastics on a large scale. Under high temperatures, in a fully enclosed environment with a reducing atmosphere, the waste plastics are converted into coke, tar, and gas. The harmful element chlorine present in the waste plastics enters the ammonia used in coking in the form of soluble ammonium chloride salts. This approach prevents the formation of highly toxic dioxins as well as corrosive gases, and it also avoids the generation of conventional combustion pollutants such as sulfur dioxide, nitrogen oxides, and dust. Thus, it enables complete, harmless treatment of waste plastics and their sustainable utilization. 2. Main Equipment The main equipment for this technology includes: special feeders for waste plastic waste, special belt conveyors for waste plastic waste, specialized vibrating screens, magnetizers, special crushers for waste plastic waste, special shredders for waste plastic waste, special breakers for waste plastic waste, equipment for quantitative mixing, specialized heat melting machines, and specialized machines for shaping heat-melted materials. 3. Key technical and economic indicators: The technology developed by Shougang has the following advantages compared to that of Nippon Steel in Japan. Shougang’s process omits the fine crushing and dechlorination steps present in the Japanese process; it requires low standards regarding the waste plastic raw materials – any type of mixed waste plastic can be used. Only simple crushing is required. By adding 2% waste plastic, the strength of the coke after reaction can be increased by 3%–8%, and the coke production can also be enhanced. 4. Application of technology: The technology for processing waste plastics using the coking process is an innovative one. Among foreign steel companies, only Nippon Steel in Japan has succeeded in developing and applying this technology. In Nippon Steel’s process, the proportion of waste plastics used is generally kept below 1%. Complex preprocessing steps such as manual sorting, multi-stage crushing, dechlorination, extrusion molding, and granulation are employed to treat the waste plastics; this approach requires significant investment. Compared to Shougang’s technology, it is more suitable for China’s conditions and offers comprehensive benefits. 5. The technology user, Shougang Technology Development, has completed the laboratory research, pilot-scale studies, pilot plant studies, and industrial-scale trials for the project, and has established a small-scale demonstration facility with an annual production capacity of 10,000 tons. Through prior research and technological development, Shougang is now able to independently provide the full set of technical parameters and key equipment specifications. A patented technology titled “Treatment of waste plastics using coking processes,” with independent intellectual property rights in China, has been developed and passed the technical achievement evaluation by the Beijing Science and Technology Commission. 6. Suggestions for technology promotion: Waste plastics can be used as raw materials for coking and as feedstock for blast furnaces, replacing part of the high-quality coking coal and blast furnace injection coal powder. The technology of processing waste plastics through coal coking is primarily applied in coking production; taking advantage of the high temperatures generated during this process, it is possible to handle large amounts of urban solid waste on a large scale. This reflects the principles of a circular economy and shows that the steel industry can contribute better to urban development. China generates approximately 5-6 million tons of waste plastics each year, and a significant amount of this waste plastic has not yet been properly disposed of; the market potential in this area is around 12.5-15 billion yuan. If this technology is applied to carry out harmless treatment and resource utilization of waste plastics, it can reduce the area required for landfilling by 45–54 million square meters, save 5–6 million tons of coal used in coking, and at the same time reduce the environmental pollution resulting therefrom. Therefore, the promotion of this technology holds very broad market prospects, bringing considerable social and environmental benefits as well as certain economic benefits. This technology still needs further improvement. During its implementation, full consideration should be given to local policies regarding resource utilization and waste disposal; it is necessary to ensure a relatively stable source and quality of waste plastics. Additionally, it should first be applied in coke ovens that already possess dry quenching technology. This post was last edited by ryn on 2009-1-18 09:35]