SEPARATION CHARACTERISTICS OF AIR BY POLYSULFONE HOLLOW-FIBER MEMBRANES IN SERIES

Characteristics of air separation are determined in a serial configura tion of hollow liber polysulfone membranes. One, two, and three separa tion cells in series are used in the measurements. All systems are ope rated in the counter-current flow mode and effects of the reject flow rate and feed pressure are considered in the measurements. The plug fl ow model is used to simulate and analyze the system. Results include v ariations in species permeance, stage cut, permeate enrichment, reject depletion, and recovery of oxygen and nitrogen gases. Most of the plu g flow model predictions are found to closely match the measured data, with deviations less than 10%. However, deviations in N-2 recoveries are found to be larger than other system parameters, with deviations c lose to 30%. increase of the number of separation cells results in hig her stage cuts and in turn to higher species recovery in the permeate stream. Simultaneously, the purity of the reject is increased and that of the permeate stream is decreased. At constant reject flow rate, th e highest permeate enrichment is found in the permeate stream of the f irst cell in the two- and three-cell systems. This is caused by the in crease in the feed flow rate, which results in reduction of the gas re sidence time and in turn the gas permeation is highly selective and is dominated by the fast permeating species O-2. (C) 1998 Elsevier Scien ce B.V. All rights reserved.