CONTINUOUS VAPOR-GAS SEPARATION WITH A POROUS MEMBRANE PERMEATION SYSTEM

In contrast to adsorption processes in which the absorbent must be regenerated periodically, a thin porous membrane can be used to separate gaseous mixtures in an efficient and continuous manner. A Continuous Porous Membrane Permeator (CPMP) was constructed that allowed the condensible vapor in the feed stream to permeate preferentially through the membrane under the driving force of a pressure difference across the membrane. A mathematical model has been developed to describe and predict the CPMP performance under various design and operating conditions. The validity of the model simulation was verified by comparing the model prediction with the experimental results. A porous Vycor glass membrane was used to recover acetone and ethanol vapors from their mixtures with nitrogen gas. The separation performance, in terms of the apparent solvent permeability, separation factor, and solvent recovery, was evaluated systematically in a parametric study. A large solvent permeability and a high separation factor were obtained simultaneously when the feed solvent vapor pressure approached the capillary condensation vapor pressure. A semipermeable membrane system is also realized when the entire length of the membrane column is saturated with the solvent condensate. The results indicate that the CPMP is a potentially high performance membrane system for industrial application of solvent recovery from waste air emission and volatile organic compound pollution control.