Simulation and Optimization of the Composite Alcohol Amine Method Used for the Low-Concentration CO2 Capture Process: Analysis for Capture Efficiency and Energy Saving

Research on low-concentration CO2 capture technology is of great significance for China to achieve “carbon peak and carbon neutrality”. However, there are currently two challenges in low-concentration CO2 capture technology: high energy consumption and significant methane loss. Therefore, in this study, a numerical simulation method is used to establish the reaction model of the piperazine-activated N-methyl diethanolamine (abbreviated as MDEA-PZ) system with CO2 using Aspen HYSYS industrial software, taking shale gas from a production area as the raw material gas. Single-factor sensitivity analysis is conducted to study the impact of N-methyl diethanolamine (abbreviated as MDEA) mass fraction, piperazine (abbreviated as PZ) mass fraction, CO2 absorption temperature, and amine liquid regeneration temperature on the process. The results show that when the N-methyl diethanolamine mass fraction is between 37% and 42% and the piperazine mass fraction is between 2.5% and 5%, the regeneration energy consumption is lower and methane loss is smaller. For the raw material gas in this study, the recommended optimal amine liquid mass ratio is 40% of N-methyl diethanolamine + 3% of piperazine. Under this condition, the preferred absorption temperature is 46 °C, the amine liquid circulation rate is 45 m3/h, and the regeneration temperature is 118 °C, resulting in a significant reduction in the total energy consumption by 8.9% compared with the initial value.