Double Slag Operating Standard for Mitigation of CO ₂ Emissions in Basic Oxygen Steelmaking

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/SiO 2 mass ratio) of 1.6 ± 0.2, and MgO content of 5 ± 1 wt% at the end of primary blowing. Under these conditions, CO 2 emissions from steel mills can be decreased from 2.20 to 2.05 ton‐CO 2 per ton‐steel, i.e., approx. 7% mitigation.