ABSTRACT
Membrane contactors are devices where the membrane provides a physical barrier between two fluid streams. In the case of gas filled membrane pores, the membrane provides a physical separation between two liquid phases. There are many examples of this type of membrane contactor: membrane distillation, osmotic distillation, and so called ‘gas membranes’, which combine gas absorption and stripping into one-unit operation. In all cases it is a difference in vapor pressure across the gas filled membrane pores that leads to mass transfer. A single or multiple components from the feed stream must vaporize, pass through the gas filled membrane pores, and condense on the other side (distillate/strip) of the membrane. In membrane distillation it is a thermal gradient that leads to the vapor pressure gradient across the membrane. In osmotic distillation and combined gas absorption and stripping it is a difference in activity of a given species in the liquid phase (at essentially isothermal conditions) on either side of the membrane that leads to the vapor pressure gradient. This chapter will focus on essentially isothermal processes (i.e., osmotic distillation and combined gas absorption and stripping).
