(385c) Carbon Capture and Storage Directly From Flue Gas: The Effects of Chemical and Biological Catalysts On Magnesium Carbonate Formation

The direct adsorption of CO₂ from flue gas and precipitation of mineral carbonates presents a transformative alternative to carbon capture and storage (CCS) schemes involving conventional post-combustion capture of CO₂ and its geologic storage. CO₂ capture processes generally involve energy intensive solvent regeneration and CO2 compression steps. Absorbing the carbon into an aqueous system and precipitating it as a thermodynamically stable solid carbonate in a single technology avoids both of these energy intensive steps in CO2 capture, while providing inherent storage of CO2. However, in order for this novel CCS technology to be viable, the kinetics of both CO2 absorption and mineral dissolution need to be sufficiently fast, particularly at the low partial pressure of CO2 commonly found in flue gas. In this study, both chemical (i.e., catechol and oxalate) and biological (i.e., carbonic anhydrase) catalysts were used to enhance the rates of CO2 hydration and serpentine dissolution. While these catalysts showed significant improvement over natural carbon mineralization kinetics, it was also important to investigate the effect of this catalytic system on the final formation of magnesium carbonate in terms of its chemistry and morphology. Experiments were performed in a lab-scale three-phase fluidized bed reactor, and optimum reaction conditions for carbonate precipitation were investigated.