Carbon Dioxide Sequestration with Flue Gas Desulfurization (FGD) Gypsum

Carbonation of industrial alkaline residues can be used as a CO₂ sequestration technology to reduce carbon dioxide emissions. In this study, alkaline Ca-rich flue gas desulfurization (FGD) gypsum samples were carbonated to a varying extent. These materials are cheap, available near large point sources of CO₂ (power plant), and tend to react relatively rapidly with CO₂ due to their chemical instability. FGD gypsum was carbonated in aqueous suspensions to study its reaction mechanisms. Process variables, such as L/S ratio and reaction time, were systematically varied, and their influence on the carbonation rate was investigated. The carbonation reaction was found that the carbonation of Ca took place in two subsequent steps (i.e. dissolution and precipitation) rather than by solid-state conversion. The diffusion of Ca toward the surface of FGD gypsum particles probably determines the overall reaction. Research on further enhancement of the reaction rate, which would contribute to the development of a cost-effective CO₂ sequestration process, should focus particularly on this mechanism.