Kinetic Behavior of Solid K2CO3 under Postcombustion CO2 Capture Conditions

Trends in CO 2 and H 2 O uptakes by solid K 2 CO 3 were studied at different carbonation temperatures and flue gas compositions over 50 consecutive regeneration–carbonation cycles. Differences in carbonation behavior between the initial and final cycles evidence changes in the phase composition of K 2 CO 3 during cycling, which stabilize in accordance with the operating conditions. Rates of carbonation and hydration were observed to decrease at higher temperatures, indicating that the forward reactions are limited by adsorption, not chemical reaction. Multiple regression analysis of the uptake data yielded negative apparent activation energies for both forward reactions modeled as simple chemical reactions, thus proving the assumption invalid. A proposed Langmuir–Hinshelwood model yielded consistent apparent activation energies for the forward reactions, showing that adsorption limitations are significant in this chemisorption process. Important process design considerations, for realizing high carbonation rates and selecting promising support materials to enhance the CO 2 capture capacity of K 2 CO 3, are also discussed.