Synergistic Utilization of Gaseous SO2 and Solid Granulated Slag Derived from a Blast Furnace Ironmaking System

The desulfurization of sulfur dioxide (SO2) in a cost-effective manner has become a significant challenge for the iron and steelmaking industry. In this work, an alternative desulfurization process combining the comprehensive treatment of granulated slag from blast furnaces and flue gas from hot blast stoves is proposed according to the chemical reaction where SO2 and moisture in the flue gas react with free calcium in the granulated slag powder to form calcium sulfite (CaSO3). To verify the feasibility of the process, a fluidized experimental reacting system was constructed, and the influence of reacting temperature, reacting time and granulated slag powder size on the desulfurization process was investigated. The experimental results demonstrated that the reaction of free CaO with SO2 to form CaSO3 requires the participation of H2O. At 150 °C, increasing the granulated slag particle size from 0.065 mm to 1 mm reduced the free CaO content from 0.2411 wt.% to 0.12 wt.%. For the 0.065 mm granulated slag, the free CaO content first decreased from 0.22 wt.% to 0.12 wt.% and then increased to 0.23 wt.% as the temperature increased from 100 °C to 250 °C. Under the conditions of 150 °C and a particle size of 0.065 mm, 50 g of granulated slag containing 0.7 wt.% free CaO could desulfurize flue gas of hot blast furnace with the SO2 content of 150 mg/m3. The findings of this study suggest a potential pathway for the comprehensive treatment of gaseous and solid wastes in the steel industry.