Ternary gas separation using two different membranes

Ternary gas mixture separation can be achieved using two different membranes inversely selective to two different fast components of the feed. The separation can be carried out using a single module two-membrane permeator, or using two single-membrane permeators in series. Depending on the sequence of the membranes, there can be two series schemes. Experimental and theoretical investigations were carried out on the separation behavior of these three possible configurations using cellulose acetate hollow fibers and silicone rubber capillaries for He-CO₂-N₂ mixtures. The effects of operating conditions and system parameters have been studied. Important performance features have been analyzed and highlighted, and behavioral patterns have been identified. Unusual separation performances, observed sometimes for series schemes, have been explained satisfactorily. This analysis is expected to facilitate understanding of various ternary gas separation schemes using membranes, and selecting the optimum one.