Determining the Performance of an Efficient Nonaqueous CO₂ Capture Process at Desorption Temperatures below 373 K

Efficient CO₂ capture by chemical absorption is currently gaining interests for the control greenhouse gas emissions. In this work, a nonaqueous process was developed to regenerate CO₂ below 373 K by removing methanol first after the hybrid solvent of monoethanolamine (MEA) and methanol had absorbed CO₂. A model was accordingly developed to analyze the performance of the desorption process. Experiments were performed to determine the missing reaction kinetics of nonaqueous solvent regeneration of CO₂ to help develop the model. The predicted gas concentration, axial velocity, energy consumption, and desorption efficiency agreed well with the stripper experimental data. A parametric analysis was conducted to investigate the effects of temperature, pressure, lean solvent loading, gas/liquid ratio, packing, and internals on the energy consumption and desorption efficiency. All analyses were performed under three defined desorption conditions: N₂, methanol vapor, and steam as purge gases. Major energy savings were clearly identified because of feasible desorption temperatures below 373 K under nonaqueous desorption conditions. N₂ purge gas desorption conditions offered the minimum energy consumption of 2.28 GJ/t, being 24% below the typical value of 3.0 GJ/t. Additionally, it was found that the nonaqueous environment improved the desorption efficiency by 10% compared to that obtained by typical aqueous solution regeneration.