Waste Plastics Recycling in Blast Furnace

Abstract

For the purpose of utilization of waste plastics, waste plastics recycling system was installed in NKK Keihin No.1 Blast Furnace at Oct.1996.To investigate the optimum particle size of plastics injected into a blast furnace, the combustion and gasification behavior of waste plastics has been studied with the drop tube furnace, raceway hot model and the commercial blast furnace.From the observation of a single plastic combustion by the drop tube furnace experiments under around 1200°C, the burning rate of coarse plastic was slower than that of pulverized coal.On the contrary, from the results of plastics injection test with the raceway hot model and commercial blast furnace, it was estimated that combustibility of coarse plastics was much different from that of pulverized coal.The combustion point of coarse plastics located to deep domain in raceway compared with those of fine plastics and pulverized coal.The coarse plastics gave high combustion and gasification efficiency compared with fine plastics and pulverized coal.Moreover, the decomposition products of plastics in the blast furnace top gas and dust were the same as that of pulverized coal operation, although hydrocarbons due to the decomposition of plastics was detected in in-furnace.Thus, it was concluded that waste plastics was completely consumed in the blast furnace, and furthermore, coarse plastics particle was effectively utilized as a reducing agent.On the basis of above results, it is considered that waste plastics injection into the blast furnace is a favorable way to realize material recycling of waste plastics and to solve environmentalissue.