Regenerating Membrane Contactors for Solvent Absorption

Abstract

Membrane contactors are a hybrid technology that incorporates the advantages of both solvent absorption and membrane separation. Porous and asymmetric composite membrane contactors have been studied for CO2 absorption, and both configurations are susceptible to pore wetting. This results in a significant reduction in the mass transfer efficiency. As such, regeneration methods to remove entrained liquids from the contactors are of interest. In this work, four regeneration protocols are trialled for a porous poly tetrafluoroethylene (PTFE) contactor and a thin film composite poly(1-trimethylsilyl)-1-propyne (PTMSP) contactor. It was found that air and vacuum drying at elevated temperatures increased the overall mass transfer coefficient of both contactors compared to the wetted state, but did not return either to their original performance. In addition, both contactors experienced rapid rewetting of the pores. Prewashing with methanol before air drying at elevated temperature produced the greatest improvement in overall mass transfer for the regenerated contactors. This was attributed to methanol miscibility with the water in the pores reducing the capillary pressure experienced during drying, as well as methanol swelling the PTMSP layer. However, original functionality was not achieved for either contactors and both continued to experience wetting over time, though at a slower rate than with non-methanol wash regeneration protocols.