Accelerated carbonation of steel slags using CO 2 diluted sources: CO 2 uptakes and energy requirements

Abstract

This work presents the results of carbonation experiments performed on Basic Oxygen Furnace (BOF) steel slag samples employing gas mixtures containing 40 and 10% CO 2 vol. simulating the gaseous effluents of gasification and combustion processes respectively, as well as 100% CO 2 for 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 CO 2 uptake 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 CO 2 emissions of a medium size natural gas fired power plant (20 MW). For the slurry-phase route, maximum CO 2 uptakes ranged from around 8% at 10% CO 2 , to 21.1% (BOF-a) and 29.2% (BOF-b) at 40% CO 2 and 32.5% (BOF-a) and 40.3% (BOF-b) at 100% CO 2 . For the thin-film route, maximum uptakes of 13% (BOF-c) and 19.5% (BOF-d) at 40% CO 2 , 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 CO 2 uptake of the slag. For both process route, the minimum overall energy requirements were found for the tests with 40% CO 2 flows (i.e., 1400-1600 MJ/t CO2 for the slurry-phase and 2220 - 2550 MJ/t CO2 for the thin-film route).