Oxygen enrichment of air: Performance guidelines for membranes based on techno-economic assessment

The use of oxygen-enriched air (OEA) is an important strategy for reducing process cost and CO2 emissions in several industrial processes. Membrane-based processes, attributing to their high energy efficiency, are promising alternatives to cryogenic distillation and pressure-swing adsorption (PSA) at small to medium scales. However, so far, the techno-economic assessment of membrane processes has been focused on the production of low-purity O-2. This study assesses O-2 enrichment by membrane-based processes in a large purity range (30-95%), and reports significant energy and cost savings when high-performance membranes, marked by O-2 permeance of 500-1000 GPU and O-2/N-2 selectivity in the range of 2-20, are developed. The analysis identifies that O-2/N-2 selectivities of 2-4, 6-15, and 20 are optimal for target purity of 30-40%, 50-65%, and >70%, respectively, leading to specific costs in the range of 20-50 $/ton(EPO2) when blending with air is not considered. Purity target below 75% can be achieved by the single-stage process while double-stage processes are needed for higher purity targets. If highly-selective membranes are available, the cost of lower purity OEA can be further reduced by blending higher purity OEA with air.