Formulation of CO₂ Sorption/Release Behaviors Using Alkali Carbonate-on-Activated Carbon

Abstract

Alkali carbonates supported on activated carbon (AC) for CO₂ sorption from moist flue gases by a temperature-swing operation have been proposed. The temperature dependence of CO₂ uptake by the sorbent was investigated to understand the CO₂ sorption/release behavior. The CO₂ sorption behaviors of alkali carbonates-on-AC at various temperatures were well explained based on CO₂ gas-sorbent equilibria. However, the reverse reaction of thermal decomposition of alkali hydrogencarbonates, which were the reaction products after CO₂ sorption, did not explain the sorption behaviors. The CO₂ gas-sorbent equilibrium constants were used to determine the effect of CO₂ partial pressure in the feed gas on the CO₂ sorption capacities. The results showed that the pressure-swing operation was appropriate for sorption using alkali carbonates-on-AC. At low CO₂ partial pressures in the feed gas, the CO₂ sorption capacities achieved using alkali carbonates-on-AC were higher than that achieved using K₂CO₃ solution (i.e., the Benfield process).