Optimization of helium extraction processes integrated with nitrogen removal units: A comparative study

Abstract

Helium is regarded as a vital gas to various industries such as medicine, aircraft manufacturing, electronics and fiber optics fabrication. Currently, natural gas reserves are considered the only viable resource for this rare element. When processing (helium-rich) natural gas, helium is generally recovered in the most downstream stage in conjunction with the nitrogen rejection unit (NRU). The feed to this unit is a nitrogen rich stream, and the product is either crude helium (50–70 mol% purity) or purified helium (99.99 mol% purity). Currently, the cryogenic distillation method is a common technology for a crude helium extraction unit (HeXU). The alternative method for this purpose is a membrane gas separation system, which is successfully used in other applications. This study aims to propose an energy-integrated scheme for each of the two helium separation technologies with a single-column NRU and to evaluate and compare them for different applications. Matlab programming has been used to model the membrane system and incorporate it into Aspen Hysys, which is used to simulate the rest of the process flowsheet. Next, the energy consumption of the systems was optimized using the particle swarm optimization method. An economic analysis was adopted to compare the two technologies for different applications in order to suggest a comprehensive map for HeXU technology selection.