Ammonia-based post-combustion CO2 and SO2 integrating capture using multi-stage solvent circulation process

Amidst growing environmental concerns stemming from fossil fuel combustion, which releases a considerable amount of pollutants and greenhouse gas. In an effort to mitigate the costs of existing combustion flue gas desulfurization and CO2 capture systems, a new multi -stage circulation (MSC) process for integrating capture of CO2 and SO2 using ammonia-based absorbents was proposed. Different functional zones were interconnected using ammonia (NH3) and potassium carbonate (K2CO3) blended solution as the absorbent, enabling efficient SO2 capture in the 1st stage, CO2 enrichment in the 2nd stage, CO2 capture enhancement in the 3rd stage and recovery of escaped NH3 in the 4th stage. Experimental results demonstrated the effectiveness of NH3/K2CO3 solution in enhancing CO2 capture efficiency. The overall CO2 capture efficiency varied between 95.4 % and 84.1 % at inlet CO2 concentrations ranging from 5 % to 30 %. Under typical combustion flue gas conditions of 622 ppm SO2 and 15 vol% CO2 , the process exhibited a SO2 removal efficiency exceeding 99.5 %, with CO2 capture efficiency surpassing 70 %. Furthermore, the CO2 desorption duty was determined to be 2.48 GJ/t CO2. 13C NMR results confirmed that simultaneous absorption of CO2 and SO2 led to the accumulation of SO2 in the liquid phase, reducing the CO2 loading in rich solvent. To address these challenges, coupled optimization strategies was proposed, ensuring high capture efficiency and low CO2 desorption duty under the complex and variable conditions of flue gas parameters, SO2 concentration, and CO2 concentration.