Carbon dioxide sequestration by mechanical activation of Linz-Donawitz steel slag; the effect of water on CO2 capture

Abstract

Mineral carbonation, a process of carbon-dioxide (CO2) captured from the atmosphere or flue gases, is a way to sequestrate CO2 safely and permanently. In this technology, CO2 is chemically reacted with calcium, magnesium, sodium, and iron-containing materials. The procedure is analogous to natural weathering processes, to form thermodynamically stable and environmentally harmless carbonate minerals. Our research was focused on simultaneous mechanical activation and CO2 capture and storage (CCS) on Linz-Donawitz steel slag dominantly composed of Ca-silicate and oxide phases. The experiments were carried out in a planetary ball mill under 5 bar CO2 pressure in dry and wet (deionized H2O) conditions. The primary objective of the experiments was to observe the role of H2O in the reactions. The presence of H2O in the system leads to a finer particle size distribution but, at the same time, reduces the number of active sites·H2O also acts as a carbonate reaction promoter, it is expected to initialize silicate (Windt et al. 2010) surface protonation and enhancing Ca leaching. The latter of the two processes was predominant so that in wet condition (0,246 kgCO2/kg), almost three times as much calcite is produced as in dry condition (0,083 kgCO2/kg). The combination of nano milling and wet media carbonation is a promising process to reduce energy requirement through increasing the reaction rate and promotes the use of Ca-silicate wastes otherwise underperforming in CCS.