Modeling and Experimental Study of Gas-Liquid Membrane Contactor

Background

Membrane gas absorption offers significant advantages compared to conventional absorption towers. Membrane contactors for gas separation have been drawing the attention of many researchers as a substitute technology (Ghasem et al., 2011; 2012; 2013). Due to the separation of the phases by a microporous membrane the contactor may be operated without limitations caused by flooding, foaming, channeling and liquid entrainment. Extremely compact hollow fiber membrane units can be made; resulting in significant savings in weight and required space. Membrane structure and performance depend upon different factors such as polymer choice, composition, temperature of coagulant and dope solution; in addition, spinning factors such as dope extrusion rate, take-up speed, bore fluid type and flow rate have to be optimized at the best conditions to manufacture the high performance membrane. Membrane pores must be small to prevent the penetration of absorbents into the pores and hence membrane wetting, on the other hand, the smaller the pore radius, the larger the liquid entry pressure (Figure 1). Completely wetted pores lead to low absorption rate since the diffusivity of pollutant gas in the liquid phase is very much smaller than that in the gas. Membrane porosity must be large so that a large gas–liquid interface is available for gas absorption.

Figure 1.

Hollow fiber membrane contactor for gas absorption