Mineral carbonation of flue gas desulfurization gypsum for CO_2 sequestration

摘要

In this study, the technical feasibility of the mineral carbonation of flue gas desulfurization (FGD) gypsum to sequester CO_2 was assessed by considering various reaction parameters. Unlike other natural and industrial materials, FGD gypsum showed very high carbonation reactivity at room temperature and atmospheric pressure. Under optimum conditions, calcium carbonate with a purity exceeding 90% could be obtained within 10 min at a carbonation rate of approximately 95%. Thus, mineral carbonation of FGD gypsum was found to be technically feasible. The use of excess ammonia (110-120%) was found to be desirable for enhancing the stability of the reaction and for obtaining high-purity CaCO_3. An increase in the CO_2 flow rate accelerated the carbonation reaction significantly but decreased the CO_2 sequestration efficiency. Therefore, the flow rate should be optimized by considering the reaction rate and CO_2 sequestration efficiency. While an increase in the solid-to-solution ratio increased the extent of temperature rise in the slurry, it did not affect the carbonation rate, which remained high at 95% for s/s ratios up to 50%. The use of a CO_2/N_2 gas mixture only slowed the carbonation reaction, and did not affect the CaCO_3 purity and carbonation rate.