The Economics of Helium Separation and Purification by Gas Separation Membranes

Abstract

Membrane gas separation has the potential to recover and purify helium, either directly from natural gas or as part of the off gas produced from the nitrogen rejection unit in conventional natural gas processing. Process designs for achieving high helium recovery and purity have previously been published by the authors, based on permeability and selectivity performances already present in current polymeric membranes. Here, the application of polymeric gas separation membranes for helium recovery is extended further, and the economic viability of process designs has been investigated and evaluated against the commercial helium price. For direct recovery and purification of helium from natural gas, membrane gas separation is economically competitive when the natural gas field has a helium concentration of ?0.3 mol %. The final compression of the purified helium dominates the economics, accounting for 45% of the capital cost (CAPEX) of the process as well as 80% of the operating costs, because the membrane area is relatively small and the staggering of the high pressure of the feed through the membrane stages reduces the need for significant compression on the membranes' recycle streams. For the recovery and purification of helium from the nitrogen rejection unit off gas, a combined membrane-pressure swing adsorption process is more economical than conventional technologies. Again, the final compression of the purified helium dominates the process, accounting for almost 90% of the production price. Sensitivity analysis demonstrates that the compressors CAPEX and cost of electricity significantly affect the production price. Hence, to increase the economic viability of membranes for helium recovery and purification, reducing the costs of the compressors and improving their efficiency will have a much greater impact than reducing the costs associated with the membrane itself.