CO_2 mineral sequestration(in ultrabasic or basaltic rocks) has been considered as a promising long-term and stable approach to reduce CO_2 in the atmosphere and would counteract the effect of global warming.Meanwhile...CO_2 mineral sequestration(in ultrabasic or basaltic rocks) has been considered as a promising long-term and stable approach to reduce CO_2 in the atmosphere and would counteract the effect of global warming.Meanwhile, clays are widely found in ultrabasic reservoirs. In our study, clays were observed in natural olivine samples, which were used for laboratory experiments in a supercritical CO_2 system at 140C and15 MPa. Initial olivine samples were crushed into two sizes which were large grains of w850-1000 mm and powder particles of w75-150 mm, with the durations of 400 and 1000 h for the powder and grains,respectively. The results showed amorphous silica was newly formed and this passivating layer could mitigate the water-rock interaction to some extent, but it would not play a long-term prohibited effect on secondary mineral carbonate formation as it is a Fe(III) free silica coating. More interestingly, the secondary carbonates were observed to form near the surface sites where locates more clays. Our findings provide insights into the reaction mechanisms of olivine-scCO_2-water interaction process in natural ultrabasic rocks.展开更多
Carbon dioxide mineral sequestration with steelmaking slag is a promising method for reducing carbon dioxide in a large- scale setting. Existing calcium oxide or calcium hydroxide in steelmaking slag can be easily lea...Carbon dioxide mineral sequestration with steelmaking slag is a promising method for reducing carbon dioxide in a large- scale setting. Existing calcium oxide or calcium hydroxide in steelmaking slag can be easily leached by water, and the formed calcium carbonate can be easily wrapped on the surface of unreacted steelmaking slag particles. Thus, further increase in the carbonation reaction rate can be prevented. Enhanced carbon dioxide mineral sequestration with steel- making slag in dilute alkali solution was analysed in this study through experiments and process evaluation. Operating conditions, namely alkali concentration, reaction temperature and time, and liquid-to-solid ratio, were initially investigated. Then, the material and energy balance of the entire process was calculated, and the net carbon dioxide sequestration efficiency at different reaction times was evaluated. Results showed that dilute alkali solution participated in slowing down the leaching of active calcium in the steelmaking slag and in significantly improving carbonation conversion rate. The highest carbonation conversion rate of approximately 50% can be obtained at the optimal conditions of 20 g/L alkali concentration, 2 mL/L liquid-to-solid ratio, and 70 ℃ reaction temperature. Carbonation reaction time significantly influences the net carbon dioxide sequestration efficiency. According to calculation, carbon dioxide emission of 52.6 kg/t- slag was avoided at a relatively long time of 120 min.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.41272061,41472232)National Innovation Experiment Program for university students(Grant No.201411415002)
文摘CO_2 mineral sequestration(in ultrabasic or basaltic rocks) has been considered as a promising long-term and stable approach to reduce CO_2 in the atmosphere and would counteract the effect of global warming.Meanwhile, clays are widely found in ultrabasic reservoirs. In our study, clays were observed in natural olivine samples, which were used for laboratory experiments in a supercritical CO_2 system at 140C and15 MPa. Initial olivine samples were crushed into two sizes which were large grains of w850-1000 mm and powder particles of w75-150 mm, with the durations of 400 and 1000 h for the powder and grains,respectively. The results showed amorphous silica was newly formed and this passivating layer could mitigate the water-rock interaction to some extent, but it would not play a long-term prohibited effect on secondary mineral carbonate formation as it is a Fe(III) free silica coating. More interestingly, the secondary carbonates were observed to form near the surface sites where locates more clays. Our findings provide insights into the reaction mechanisms of olivine-scCO_2-water interaction process in natural ultrabasic rocks.
基金financially supported by the National Natural Science Foundation of China (No. 21300212)
文摘Carbon dioxide mineral sequestration with steelmaking slag is a promising method for reducing carbon dioxide in a large- scale setting. Existing calcium oxide or calcium hydroxide in steelmaking slag can be easily leached by water, and the formed calcium carbonate can be easily wrapped on the surface of unreacted steelmaking slag particles. Thus, further increase in the carbonation reaction rate can be prevented. Enhanced carbon dioxide mineral sequestration with steel- making slag in dilute alkali solution was analysed in this study through experiments and process evaluation. Operating conditions, namely alkali concentration, reaction temperature and time, and liquid-to-solid ratio, were initially investigated. Then, the material and energy balance of the entire process was calculated, and the net carbon dioxide sequestration efficiency at different reaction times was evaluated. Results showed that dilute alkali solution participated in slowing down the leaching of active calcium in the steelmaking slag and in significantly improving carbonation conversion rate. The highest carbonation conversion rate of approximately 50% can be obtained at the optimal conditions of 20 g/L alkali concentration, 2 mL/L liquid-to-solid ratio, and 70 ℃ reaction temperature. Carbonation reaction time significantly influences the net carbon dioxide sequestration efficiency. According to calculation, carbon dioxide emission of 52.6 kg/t- slag was avoided at a relatively long time of 120 min.
