Separation of hydrogen from 10 % hydrogen + methane mixtures using double-stage Vacuum Swing Adsorption (VSA)
Leila Dehdari, Jianing Yang, Penny Xiao, Gang Kevin Li, Paul A. Webley, Ranjeet Singh
Abstract
Transportation of hydrogen by blending it to the existing natural gas infrastructure is one of the economical ways of having a green future. After co-transportation of hydrogen this way, hydrogen deblending from natural gas is needed at various locations for different end-users. Hydrogen content in pipelines at the primary injection phases will be low (<20 %) which makes the separation challenging. The goal of current study is to investigate the production of high purity hydrogen from a 10 % hydrogen + natural gas mixture using VSA. A four-bed VSA plant filled with activated carbon was used to conduct the experiments in the lab using binary mixture of 10 % H2 + CH4 (% mol/mol). High purity hydrogen (99 %) was achieved at 102 kPa feed pressure in the lab. After validation of simulation tool with experimental results, Aspen Adsorption software was used to assess the performance of producing 99 % hydrogen purity using double-stage VSA process at small scale. Results revealed that achieving high-purity hydrogen using a double-stage VSA, by upgrading H2 from 10 % to 50 % in the first stage and then to 99 % H2 in the second stage leads to better separation performance and less energy consumption than a single stage VSA for the same separation target. Afterwards, a five-bed double VSA system in industrial scale was developed using Aspen Adsorption to produce high hydrogen purity from a representative 10 % hydrogen + natural gas mixture. High purity hydrogen (>99 %) along with high recovery (>82 %) were achieved at a feed pressure of 110 kPa.