Carbonation of Activated Serpentine for Direct Flue Gas Mineralization

AbstractResearch in mineral carbonation has moved towards process concepts that combine the capture of CO2 from flue gas with its conversion into stable carbonates. This requires highly reactive source materials that dissolve under lean CO2 pressures and temperatures. Activated serpentine has been used in this study, and its carbonation potential under flue gas conditions has been investigated. Single-step carbonation experiments were performed in stirred reactors with gas-dip tubes, at partial pressures of CO2 up to 1bar, temperatures between 30°C and 90°C, with and without concurrent grinding using a ball mill. The pH and solids were monitored in-situ, and the degree of carbonation of the products was quantified using thermogravimetric analysis. Given the low CO2 pressure, carbonation was successful, as confirmed by the formation of the two magnesium carbonates nesquehonite and hydromagnesite. However, under all conditions investigated, including grinding, the extent of carbonation did not exceed 20%. It was concluded that after the onset of precipitation, the reactor solution in single-step carbonation experiments reaches equilibrium conditions with respect to both serpentine dissolution and carbonate precipitation

Dissolution of Activated Serpentine for Direct Flue-Gas Mineralization

AbstractThe dissolution of thermally activated serpentine (75% dehydroxylated) by direct flue-gas mineralization was investigated at far-from-equilibrium (w.r.t mineral dissolution) flow-through operating conditions. Experiments were performed at moderate partial pressures of CO2 (0.1bar 2bar CO2) and temperatures (30°C 90°C). Thermal activation enabled the dissolution of serpentine at mildly acidic conditions. Both magnesium and silica were released upon dissolution. However, the silica conversion was under-stoichiometric with respect to magnesium. Fast initial dissolution rates were observed with magnesium conversions reaching 60% in 30min. Experiments were also performed in the absence of CO2 with identical pH conditions generated with mineral acid (HCl). The dissolution profiles were similar to those obtained under flue-gas atmosphere