Valorization of lignin biomass as a carbon feedstock in steel industry: Iron oxide reduction, steel carburizing and slag foaming

The heavy use of coal-derived coke (CDC) in steel industry makes it a major contributor to the greenhouse emissions. With the impact of global warming knocking our doors, the CDC has experienced supply shortages and increasing costs. Such scenario has raised the need to find a sustainable and renewable replacement to CDC. Hard-wood biomass has emerged as a promising alternative to the CDC. While such sources of virgin biomass remain at high cost, other types of agro-industrial residues constitute an opportunity for further sustainable utilization. In the current work, we have assessed the suitability of an abundant source of biomass waste, i.e., lignin-rich press mud (LPM), for steel industry. Hard carbons were obtained from LPM through a thermal treatment at a wide range of temperatures, and the chemical content (i.e., impurity) of all carbons was compatible with the steel making process. Before fitting the LPM-derived carbons (LPMCs) for such purpose, several carbon properties (e.g., chemical content and reactivity) and carbon-steel interactions (e.g., iron oxide/slag reduction, steel carburizing) were comprehensively studied and evaluated. The LPMC obtained at high temperature has particularly demonstrated an excellent reduction performance and desirable slag interactions compared to a typical metallurgical coke. The diffusion of S from LPMC into steel was an issue raised and discussed in this study. The reduction of S in LPMC was demonstrated and a subsequent enhanced C uptake in steel of 2.38% was achieved.