Effect of pCO₂ on direct flue gas mineral carbonation at pilot scale

Concerns about global warming phenomena induced the development of research about the control of anthropogenic greenhouse gases emissions. The current work studies on the scaling up of aqueous mineral carbonation route to reduce the CO₂ emissions at the chimney of industrial emitters. The reactivity of serpentinite in a stirred tank reactor was studied for several partial pressures of CO₂ (pCO₂) (0.4, 0.7, 1.3 and 1.6 bar). Prior to carbonation, the feedstock was finely grinded and dehydroxyled at 650 °C by a thermal treatment. The major content of magnetite was removed (7.5 wt% · total weight^-1). Experiments were carried out under batch mode at room temperature using real cement plant flue gas (14-18 vol% CO₂) and open pit drainage water. The effect of the raw water and the pCO₂ on the carbonation efficiency was measured. First, the main results showed a positive effect of the quarry water as a slight enhancement of the Mg leaching in comparison with distilled water. Secondly, a pCO₂ of 1.3 bar was the optimal working pressure which provided the highest efficiency of the carbonation reaction (0.8 gCO₂ · g residue^-1). Precipitation rates of dissolved CO₂ ranged from 7% to 33%. Pure precipitate was obtained and essentially composed of Nesquehonite. At a pCO₂ of 1.3 bar, additional physical retreatment of the solid material after being contacted with 6 batches of gas enhanced considerably mineral carbonation efficiency (0.17 gCO₂ · g residue^-1.).