Accelerated carbonation of steel slags using CO2diluted sources: CO2uptakes and energy requirements

This work presents the results of carbonation experiments performed on Basic Oxygen Furnace (BOF) steel slag samples employing gas mixtures containing 40 and 10% CO2vol. simulating the gaseous effluents of gasification and combustion processes respectively, as well as 100% CO2for comparison purposes. Two routes were tested, the slurry-phase (L/S = 5 l/kg, T = 100°C and Ptot = 10 bar) and the thin-film (L/S = 0.3-0.4 l kg, T = 50°C and Ptot = 7-10 bar) routes. For each one, the CO2uptake achieved as a function of the reaction time was analyzed and on this basis, the energy requirements associated with each carbonation route and gas mixture composition were estimated considering to store the CO2emissions of a medium size natural gas fired power plant (20 MW). For the slurry-phase route, maximum CO2uptakes ranged from around 8% at 10% CO2, to 21.1% (BOF-a) and 29.2% (BOF-b) at 40% CO2and 32.5% (BOF-a) and 40.3% (BOF-b) at 100% CO2. For the thin-film route, maximum uptakes of 13% (BOF-c) and 19.5% (BOF-d) at 40% CO2, and 17.8% (BOF-c) and 20.2% (BOF-d) at 100% were attained. The energy requirements of the two analyzed process routes appeared to depend chiefly on the CO2uptake of the slag. For both process route, the minimum overall energy requirements were found for the tests with 40% CO2flows (i.e., 1400-1600 MJ/tCO2for the slurry-phase and 2220 - 2550 MJ/tCO2for the thin-film route).