Semi-batch absorption and regeneration studies for CO2 capture by aqueous ammonia

Abstract Carbon dioxide transfer capacities of aqueous ammonia solution and monoethanolamine (MEA) solution were compared. The ammonia process for CO 2 capture was simulated using a semibatch reactor, where the flow of gas is continuous. The CO 2 carrying capacity in g CO 2 per g of NH 3 solution (8 wt.%) circulated is 0.07 as compared with 0.036 g CO 2 per g MEA solution (20 wt.%). The energy requirement for liquid mass circulation of ammonia solution is approximately 50% of MEA solution for equal weight of CO 2 carried. In another comparison, the thermal energy required to regenerate CO 2 from the rich solution is substantially less as compared to the MEA process. A 3-cycle absorption–regeneration test was conducted in the semibatch reactor to simulate an approach-to-steady state in a flow system. pH values of the absorbent solution was found to oscillate between 9.6 (CO 2 -lean) and 8.8 (CO 2 -rich) under the test conditions. Thermodynamics study shows that ammonium bicarbonate required the least thermal energy among the ammonium compounds for CO 2 regeneration.