Combustion and Gasification Behaviors of Plastics Injected into Raceway of Blast Furnace

The combustion and gasification behaviors of plastics have been investigated with the drop tube furnace, raceway hot model and scrap melting shaft 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, in the raceway hot model and scrap melting shaft furnace with the plastics injection, the combustion efficiency of plastics was much higher than that of pulverized coal in spite of coarse particle. Moreover, the gas composition and temperature distribution in the raceway during the plastics injection were similar to those of all coke operation. Thus, it was concluded that the combustion mechanism of coarse plastics was different from that of pulverized coal. On the basis of these results, it was estimated that the residence time of coarse plastics in the raceway was longer than that of pulverized coal or fine particle. The circulation model of coarse plastic particle in the raceway was newly investigated, and the combustion efficiency of plastics was theoretically evaluated. The results calculated by the circulation model agreed with those of the hot model experiments.