A NEW EVALUATION OF MEMBRANE PROCESSES FOR THE OXYGEN-ENRICHMENT OF AIR .1. IDENTIFICATION OF OPTIMUM OPERATING-CONDITIONS AND PROCESS CONFIGURATION

The economics of membrane separation processes for producing oxygen-enriched air at a concentration of at least 30 mole% O2 have been examined. Six different process configurations and three different types of polymer membranes were considered in the first part of this study. The membranes were silicone rubber, poly(phenylene oxide), and cellulose triacetate. The performance of the process configurations was compared on the basis of new operating variables. The operating conditions were optimized for all process configurations and types of membranes to yield the lowest production cost of "equivalent" pure oxygen (EPO2). It was confirmed that a single permeation stage without product recycle, and with vacuum pumping the permeate, is the optimum process configuration for the oxygen-enrichment of air (30 mole% O2 minimum). The lowest cost of producing 10 tons per day (TPD) of EPO2 was obtained for silicone rubber membranes (about $57/ton of EPO2); this cost includes a return on investment of 12%/year. A following publication will consider the effects of variations in a number of economic parameters, in plant size, and in membrane properties on the production cost of EPO2.