Influence of Reaction Parameters on Solid Outputs in CO2 Mineralization of Desulfurized Gypsum

Abstract

Flue gas desulfurization gypsum is the main solid byproduct generated during the limestonegypsum wet desulfurization process in coal-fired power plants. This byproduct is produced in large quantities annually, and ineffective management or disposal can lead to significant environmental damage and land resource wastage. This study investigates how reaction conditions affect CO2 mineralization of desulfurization gypsum, focusing on the purity of the resultant solid minerals, the rate of carbonation of CaSO4·2H2O, and the proportion of vaterite in the produced calcium carbonate. The experimental findings suggest that an increase in ammonia solution concentration enhances the purity and carbonation rate of calcium carbonate from CaSO4·2H2O. Additionally, a higher CO2 flow rate speeds up the mineralization process but may decrease CO2 capture efficiency; however, an optimal increase in CO2 flow can reduce the Ca2+ to CO32- ratio, facilitating the formation of vaterite calcium carbonate. The solid-to-liquid ratio in the reaction does not generally impact the purity or carbonation rate of calcium carbonate but increasing this ratio leads to higher supersaturation of the solution, slowing the conversion of vaterite to calcite and increasing the vaterite content. However, this effect diminishes past a certain point. This research serves as a basis for refining the direct mineralization conditions for CO2 in desulfurization gypsum processes, aiming to optimize the conditions for producing high-quality vaterite-type calcium carbonate.