Progress in industrial CO2 sequestration technologies by mineral carbonation of steel slag with particular reference to climate change - A South African perspective

摘要

Industrial mineral carbonation of wastes, an increasingly promising component of Carbon Capture and Storage, may play an important role as a CO_2 mitigation strategy in the South African context of climate change. Steelmaking slags are of particular interest owing to their high content of Ca. The cumulated 'effective' CO_2-specific sequestration capacity (calculated on the basis of Ca and Mg extracted to a 0.5M HNO3 solution) of three basic oxygen and one electric arc furnace slags generated at steel mills in South Africa was 253kt CO2 per annum, which was 25.2% lower than the 'theoretical' capacity (estimated on the basis of total Ca and Mg content in slags). The mineralogical composition and solubility characteristics of slags conferred very distinct leaching behaviours to the slags, such as differences in (i) the amount of heat generated during their dissolution, (ii) their buffering capacity, (iii) the rate and extent of Ca and Mg extraction from the slags, and (iv) the mineralogical composition of the non-dissolved residues. These findings suggest that separate leaching processes may need to be developed for slags with largely distinct mineralogical compositions and structural features. Differences in processes may include the use of various solvents, concentrations, temperature conditions, or leaching times.