Ideal Separation Factor

The separation factor, SF, is a measure of the efficiency of the separation process and is determined from the ratio of the concentrations of the more permeable gas species i and the less permeable gas species j in the permeate divided by the ratio of the same gases i and j in the feed stream: SF = (xi,p/xj,p)/(xi,f/xj,f) (1) where x i,p and x j,p are the fractions of components i and j in the permeate and x i,f and x j,f are the fractions of components i and j in the feed. The separation factor is not a material property, but it also depends on the conditions of the separation process. It depends both on the membrane properties and on the driving force, which in turn depends on the pressure and on, for instance, the presence of concentration polarization phenomena, nonideal behaviour such as plasticization, coupling effect, etc. Analogously, the ideal separation factor is the separation factor under ideal conditions. It can be calculated from the pure gas permeabilities.