Utilization of Waste HDPE for Sustainable EAF Steelmaking: Carbon Dissolution into Liquid Steel

Abstract

Carbon dissolution from blends of metallurgical coke with high-density polyethylene (HDPE) into liquid steel at 1823 K is investigated in-depth. HDPE is blended with metallurgical coke into three different ratios (blends H1, H2, and H3) and used as a carburizer. Compared to coke, a significant improvement in carbon dissolution is observed in the case of blend H3 with the carbon picked up by liquid steel after 60 min of reaction and the dissolution rate (K) is 4.5 wt% and 15.2 × 10−3 s−1, respectively. For coke alone, the melt carbon content is 0.8 wt% and the dissolution rate of 0.3 × 10−3 s−1. SEM micrographs and corresponding off-gas analysis reveal that the gasification of HDPE/coke blends slow down the coverage of ash oxides at the Fe–C interface and modify morphology of the ash layer. The associated reactions of volatiles generated during the thermal degradation of the polymer can aid the carburization of liquid steel to some extent. However, the amount of gas generated must be high enough to overcome the effect of ash oxides at the Fe–C interface. This study has strong implications in enhancing the potential of recycling waste polymers for sustainable steelmaking.