Investigation of High-Temperature CO2 Capture by CaO in CaCl2 Molten Salt

Modifications of CaO-based sorbents with various inorganic salts to overcome the degradation in the reactivity between the active material and CO2 in a carbon capture process have previously been evaluated. The present paper focuses on the performance of a novel CO2 capture technology, where CaCl2 is applied as the solvent for the dissolution/dispersion of CaO and CaCO3. CO2 capture by CaO was carried out with carbonation temperatures in the range of 770–830 °C by bubbling simulated flue gas through the melt, using a fully automated flow-through atmospheric pressure reactor. Subsequently, decomposition of the formed CaCO3 to CaO and CO2 was conducted at 910–950 °C using pure N2. Online gas analysis was performed using a Fourier transform infrared (FTIR) gas detector and gravimetric analysis. The results indicate that the CaO carbonation efficiency decreases at temperatures higher than 800 °C. Increasing the concentration of CaO enhances the carbonation reaction. The amount of CO2 uptake for 15 wt % CaO in calcium dichloride was 0.541 g of CO2/g of sorbent. Moreover, investigation of CO2 absorption/desorption by 5.32 wt % CaO in CaCl2 at 787 °C showed an increase in CaO reactivity, defined as the ratio between the real and theoretical CO2 sorption per unit of CaO, from 55.4 to 64.2% after 10 cycles. In all cases, the decarbonation process proceeded rapidly, reaching 100% efficiency.