Performance analysis of Dual Mixed Refrigerant System in Cryogenic Distillation Column as carbon capture at Acid Gas Removal Unit

In natural gas processing, the presence of acid gas by-products such as hydrogen sulfide (H2S) and carbon dioxide (CO2) poses significant environmental concerns, necessitating effective mitigation strategies. This study investigates the reduction efficiency of acid gases through cryogenic distillation integrated with a Dual Mixed Refrigerant (DMR) cooling process, using a simulation-based approach. The simulation models the performance of various combinations of natural gas (NG) and amine solutions (MDEA) in the Acid Gas Removal Unit, designated as Process 1 (NG A & MDEA A), Process 2 (NG A & MDEA B), Process 3 (NG B & MDEA A), and Process 4 (NG B & MDEA B). The findings reveal that Process 3 achieves the most effective separation of CO2 and H2S, with maximum molar fraction separations of 28.06% and 67.15%, respectively. Moreover, H2S removal reaches its peak efficiency in Process 3, with a reduction rate of 92.91%, indicating the potential of the cryogenic distillation column system when combined with MDEA. Despite these promising results, CO2 removal remains limited, with the highest reduction of only 40.94% also observed in Process 3, suggesting the need for further optimization. Additionally, the DMR system successfully reduces the temperature and pressure of natural gas to -163°C and 110 kPa, respectively. Process 3 exhibits a notable molar fraction decrease of 0.88%, underscoring its superior performance among the configurations studied.