BOF Steel Slag: Critical Assessment and Integrated Approach for Utilization

During steel production, the impurities in the hot metal react with the fluxes forming the steel slag. Chemical constituents of this steel slag (SS) are relevant to iron/steelmaking or blended cement manufacture. Harmful impurities present in it, however, limit its recycling to these applications. Japan, Europe, and the US consume a significant amount of their SS, but more than 50% end up in low-end applications such as aggregates, etc. Massive generation and limited usage have resulted in huge SS accumulation in China and India (the top two steel-producing countries). This paper takes a critical look at the developments toward steel slag recycling and utilization, leading to resource conservation and greenhouse emission control. Various approaches toward eliminating the inhibiting factors for recycling the SS in iron/steelmaking and blended cement manufacture are critically analyzed. Based on the analysis, the authors present a holistic approach toward steel slag utilization beyond the conventional application areas like aggregates, landfilling, etc. This approach involves heat recovery from the molten slag, optimal, and efficient materials recovery/recycling, and carbon capture. Energy recovery conserves fossil fuel consumption (with a consequent reduction in CO2 emission). The energy recovery processes inching toward commercial application yield a granulated glassy slag suitable for further recycling. Indirect benefits from these include a reduction in the environmental and ecological impacts of mining and related activities. Such endeavors will enable the steel industry to circumvent stringent environmental regulations and achieve energy efficiency.