Separation of hydrogen from methane by vacuum swing adsorption

One option for economical storage and transportation of hydrogen in near future is to add it to the existing natural gas pipelines. Hydrogen co-transported in this way can be extracted from the natural gas to produce either pure hydrogen or natural gas for different applications. The goal of this study is to assess experimentally the production of high purity hydrogen and/or natural gas products from hydrogen/natural gas mixtures using a vacuum swing adsorption (VSA) process at low pressure terminals. A four-bed VSA apparatus filled with Norit RB4 activated carbon was used in the lab for the experiments. High purity hydrogen (> 99%) was achieved with the VSA process for hydrogen feed concentrations of 30% and 50% at 102 kPa feed pressure. After the experi-mental results were used to validate the simulations, a six-bed three-layered pressure vacuum swing adsorption (PVSA) system was developed in Aspen Adsorption software to separate hydrogen from a representative natural gas mixture. High purity hydrogen (> 99%) and high purity natural gas (> 98%) were simultaneously achieved with the PVSA system for different hydrogen concentrations (10 to 50%) in the feed at a feed pressure of 4 bar. We also demonstrate that hydrogen can be replaced with helium for safer process operations in laboratory. The required power to produce hydrogen purity above 99% decreased as the H2 feed concentration and desorption vacuum pressure increased, and bed productivity increased as H2 feed concentration increased. This study suggests it is viable to produce high purity H2/natural gas at low pressure terminal users.