Parameter and Process Optimization for Low-Concentration CO2 Capture Using Mixed Alkanolamine Solutions

To reduce the high energy consumption of conventional alkanolamine-based CO2 capture, a rate-based CO2 capture model was developed in Aspen Plus using a DETA/AEP mixed amine absorbent identified through preliminary screening experiments. The effects of key operating parameters of the absorber and stripper on system performance were systematically investigated, and the energy-saving potentials of interstage cooling, rich-solvent splitting, and their combined process were explored. The results show that the optimal operating parameters are as follows: lean-solvent temperature of 40 °C, flow rate of 150 m3/h, concentration of 35 wt.%, absorber packing height of 10 m, stripper operating pressure of 2 bar, rich-solvent feed stage at the fifth stage, and feed temperature of 105 °C. Under these optimized conditions, the model-predicted specific regeneration energy consumption of the conventional process was 6.08 GJ/t CO2. Introducing interstage cooling at the ninth stage reduced the specific regeneration energy consumption to 5.42 GJ/t CO2. Rich-solvent splitting, with a split ratio of 15% and hot rich-solvent feeding at the sixth stage, further reduced the value to 3.45 GJ t−1 CO2. When the two strategies were integrated, the specific regeneration energy consumption decreased to 3.38 GJ/t CO2, corresponding to a 44.41% reduction compared with the conventional process.