Double Slag Operating Standard for Mitigation of CO2 Emissions in Basic Oxygen Steelmaking

Abstract

Basic oxygen furnace (BOF) steelmaking uses a double slag process (DSP) to produce low-phosphorus steel. Many studies have been performed based on the general hot metal ratio (HMR) and the optimal conditions of the DSP. To reduce carbon emissions in a BOF, which is a challenge for all steel mills, the HMR must be lowered. In general, dephosphorization of hot metal can be facilitated by a low temperature, a high oxygen potential, i.e., a high-FeO slag and a high slag basicity. The present article describes the optimal conditions for DSP operations under low-HMR conditions: temperature of 1360 ± 5°C, total Fe content of 10 ± 2 wt%, basicity (=CaO/SiO₂ mass ratio) of 1.6 ± 0.2, and MgO content of 5 ± 1 wt% at the end of primary blowing. Under these conditions, CO₂ emissions from steel mills can be decreased from 2.20 to 2.05 ton-CO₂ per ton-steel, i.e., approx. 7% mitigation.