Regeneration of CO2 absorbent with membrane contactor via pressure swing

Abstract

A new method to regenerate high pressure CO2 absorbent is presented in this paper, where PTFE hollow fiber membrane contactor was used as a gas–liquid separator in pressure swing process. CO2 desorption happened in the membrane contactor at the same time. The two mass transfer mechanisms were analysed through calculation of viscous flux and mass transfer coefficients. Experimental results showed that CO2 loading in regenerated absorbent increased with absorbent flow rate. This was due to decrease in membrane area available for CO2 desorption, as most of the membrane area was utilized for gas-liquid separation. Co-current configuration exhibited higher CO2 desorption driving force compared to counter-current configuration, hence its CO2 loading in regenerated absorbent was lower. When integrated with membrane contactor for CO2 absorption, stable and consistent performance was observed. Unlike conventional flash drum, membrane contactor did not have requirement on flashed gas velocity, because the membrane itself functioned as a screen to prevent fine liquid droplets from escaping the system along with flashed gas. Results from this study show that vessel size reduction up to 2.5 times could be achieved when PTFE membrane contactor was used, with absorbent regeneration energy as low as 0.94 GJ/ton CO2.