Membrane gas–solvent contactor trials of CO2 absorption from syngas

Membrane gas–solvent contactors incorporate the advantages of both solvent absorption and membrane gas separation technologies. Here, gas–solvent contactors are applied to the separation of carbon dioxide from syngas in a coal fired pilot plant. Two contactors, based on polypropylene (PP) and polytetrafluoroethylene (PTFE), are trialed with two solvents, 30 wt.% monoethanolamine (MEA) and 30 wt.% potassium carbonate (K2CO3) solutions. To validate performance, results were also obtained with a mixture of 10% CO2 in N2 in the laboratory. All contactor–solvent systems tested in the laboratory behaved in accordance with membrane contactor models with only minor pore wetting observed. Mass transfer coefficients were improved when solvent flowed on the shell side of the contactor due to increased turbulence and reduced pore wetting relative to the lumen side. In contrast, for the pilot plant trials with syngas, only the PP–K2CO3 and PTFE–MEA systems provided mass transfer coefficients similar to those determined in the laboratory. For the PTFE–K2CO3 system, additional pore wetting resulted in reduced overall mass transfer coefficients. The PTFE–MEA system retained the best overall mass transfer performance, due to reduced pore wetting and greater reaction enhancement.

► Membrane gas absorption tested with PP and PTFE membranes using carbonate and amine solvents. ► Solvent in shell side led to higher overall mass transfer coefficients than solvent in lumen. ► Pilot scale trials with syngas showed reduced performance due to membrane wetting.