Aqueous mineral carbonation for CO2 sequestration: From laboratory to pilot scale

In the actual context of the greenhouse gases (GHGs) control, the industrial sector must find efficient and practical solutions to reduce their emissions. The feasibility of an aqueous mineral carbonation (MC) process was demonstrated at the laboratory scale under original mild conditions. In the continuity of this research, the process was tested at a pilot scale using a cement plant flue gas comprising of 12% to 20% CO2. Experiments were performed in an 18.7 L Parr reactor. Two different magnesium (Mg) rich tailings were used during the MC reactions with a solid/liquid ratio of 150 g/L, gas/liquid ratio of 3, room temperature (22 ± 3 °C) and a stirring speed of 600 rpm. The total pressure ranged between 2 and 10 atm. Each experiment comprised of six batches of gas with a residence time of 15 min to 30 min each for the liquid and 90 min for the solid. The results demonstrated that at low pressure (2 and 4 atm), between 90% and 96% of the CO2 in the flue gas can be removed under dissolved form. The rate decreased to 64-74% at 10 atm. The cumulative quantity of dissolved CO2 after six batches of treated gas increased with CO2 partial pressure and from 0.08 to 0.25 g CO2/g of residue. The magnesium (Mg) leaching followed the same trend as the captured CO2 quantity. The higher cumulative leaching rate for the magnesium was 19%. These results were lower than those expected compared to the laboratory scale. The results showed that 25% to 33% of the total dissolved CO2 was captured as nesquehonite (MgCO3·3H2O) of a high purity.