Development of waste plastics injection process in blast furnace

At Keihin No. 1 Blast Furnace, waste plastics recycling system was installe d in Oct. 1996. Before the installation of that system, the behavior of was te plastics injected into the blast furnace has been studied with the racew ay hot model and the commercial blast furnace so as to investigate the poss ibility of effective waste plastics utilization in the blast furnace. From the observation of plastics particle injected into the raceway of blast fur nace, it was estimated that combustibility of coarse plastics was much diff erent from that of pulverized coal. The combustion point of coarse plastics located to deep domain in raceway compared with that of pulverized coal. A lthough C-1-C-4 hydrocarbons due to the decomposition of plastics was detec ted in in-furnace, the decomposition products of plastics in the blast furn ace top gas and dust were the same as that of pulverized coal injection. Th e preparation method of plastics had an influence on the combustion and gas ification behavior in the raceway. The coarse plastics gave high combustion and gasification efficiency compared with fine plastics and pulverized coa l, and CO2 gasification rate of unburnt char derived from waste plastics wa s much higher than that of pulverized coal. Thus, it was concluded that coa rse waste plastics could be effectively utilized as a reducing agent in the blast furnace. On the basis of above results, the waste plastics recycling system was designed.