Effects of Membrane Properties on CO2 Desorption from Chemical Absorbents Using a Membrane Flash Process

Abstract

Chemical absorption method is a major separation technique employed in CCS (Carbon dioxide Capture and Storage). In recent years, a novel process named a membrane flash process for regeneration of the absorbent was developed to realize an energy-saving technology. In this study, the effects of pore size and thickness of microporous hollow fiber membrane on the CO2 desorption rate in the membrane flash process were examined.CO2 desorption experiments were performed using the three purchased microfiltration (MF) membranes with different pore sizes, 0.2, 0.5 and 1.0μm, and the two microporous hollow fiber membranes made from alumina particles with different thicknesses. A 30 wt%-monoethanolamine (MEA) aqueous solution was used as the chemical absorbent. The MEA solution which absorbed CO2 in advance was fed into the tube side of the hollow fiber and was forced to permeate through the membrane by reducing the pressure on the shell side to 40 – 1kPa.The results indicated the CO2 desorption rate increased with decreasing pore size. Also, the thicker membrane showed the greater CO2 desorption rate. The results and observation implied that CO2 desorption occurred not only on the surface of the rich solution falling down along the outer surface of the hollow fiber after permeating through the membrane but inside the pores of the membrane wall. Also, the experimental results supported that the contact of the rich solution with the membrane played an important role in CO2 desorption.