Accelerated carbonation of steel slags using CO2 diluted sources: CO2 uptakes 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% CO2 vol. 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 wet (L/S =0.3-0.4 l/kg, T=50 °C and Ptot=7-10 bar) routes. For each, the CO2 uptake achieved as a function of the reaction time was analyzed and on this basis the energy requirements associated to each carbonation route and gas mixture composition were estimated considering to store the CO2 emissions of a medium size power plant (20 MW). For the slurry-phase route, CO2 uptakes after 24 h ranged from around 8% at 10% CO2, to 21-29% at 40% CO2 and 32.5-40% at 100% CO2. For the wet route, uptakes of 13-19.5% at 40% CO2and 17.8-20.2% at 100% CO2 were attained. The energy requirements of the two analyzed process routes appeared to depend chiefly on the CO2 uptake of the slag. The minimum overall energy requirements were found for the tests with 40% CO2 flows (i.e. 1400-1600 MJ/t CO2 for the slurry and 2220-2550 MJ/t CO2 for the wet route). © 2015 The Authors.