Development of shaft-type scrap melting process characterized by massive coal and plastics injection

Abstract

A shaft-type scrap melting process in which a large amount of pulverized coal and waste plastics are used as a heat source has been newly proposed. To confirm the characteristics of this process, an experimental furnace with 2 m3 inner volume was continuously operated. The main results are as follows: (1) Pulverized coal and plastics could be effectively used to melt steel scrap, and a newly designed oxygen burner enabled massive injection of such fuels. (2) Combustion efficiency of coarse plastics was higher than pulverized coal due to the its accumulation effect in the raceway. Hydrogen chloride during Polyvinylchloride injection was about 5 ppm in the gas cleaning system. (3) Top charge of plastics generated tar derived from decomposition of plastics in the shaft with low temperature. (4) Zinc charged with scrap was carried over as zinc oxide with dust in the upward gas, and no adhesion was recognized within the furnace. (5) Maximum productivity was estimated to be 14 t/dm3 from the viewpoints of flooding and melting rate of scrap. On the basis of the above operation results of the experimental furnace, the operating condition of the commercial process was investigated.