Membrane Evaporation for Energy Saving in CO₂ Chemical Absorption Process Using a Polybenzimidazole Film: Mass and Heat Transfer

Intensive energy consumption remains a major challenge for the commercial application of CO₂ chemical absorption. In this study, a membrane evaporation system based on PBI film was proposed for recovering latent heat from the hot lean CO₂ solution in order to reduce the energy penalty during CO₂ capture process. The effects of key operational parameters (i.e., evaporation temperature, sweeping gas flow rate, and liquid flow rate) were systematically investigated. It was found that both vapor flux and recovered heat flux had exponential increases when the evaporation temperature increased. Sweeping gas flow rate and liquid flow rate had limited effects on both mass and heat transfer in the membrane evaporation process. The PBI film showed good stability during a 14 days' duration experiment. Reducing the membrane thickness can significantly improve the membrane evaporation performance. From the viewpoint of energy evaluation, when the evaporation mass reached 10 g/kg solution, the regeneration energy consumption could be reduced by 0.47 MJ/kg CO₂, which demonstrates a great potential to save energy consumption in large-scale CO₂ chemical absorption processes.