Purification of hydrogen from natural gas/hydrogen pipeline mixtures

Leila Dehdari, Iris Burgers, Penny Xiao, Kevin Gang Li, Ranjeet Singh, Paul A. Webley

Research output: Contribution to journalArticleResearchpeer-review

2 Citations (Scopus)

Abstract

There is an increasing global attention toward hydrogen as a green energy carrier, primarily because of the environmental concerns associated with global warming issues. It is expected that the produced hydrogen from various sources may be injected to the natural gas grid for economical transportation and use. One interesting option is to evaluate technologies for extracting the hydrogen from the natural gas pipeline for applications using high purity hydrogen. However, natural gas is a complex mixture including CH4, C2H6, CO2, N2 and trace amounts of C3-C6 hydrocarbons. This function requires a natural gas/hydrogen separation technology which must not only operate with low capital and energy cost, but must also provide hydrogen of sufficient purity. The goal of current work therefore was to take a mixture of hydrogen/natural gas of representative concentrations and produce high purity hydrogen using a bespoke pressure swing adsorption (PSA) cycle. A six-bed PSA system with 12 steps was developed and simulated in Aspen Adsorption software to this end. A three-layered adsorption column was designed to capture different groups of components of the mixture selectively within each layer. Informed by measured and literature equilibrium isotherm data, silica gel was chosen as the pre-layer to remove heavy hydrocarbon components and most of the CO2; activated carbon in the main-layer to mainly adsorb methane, and LiLSX zeolite in the top-layer to remove trace nitrogen which had eluted from the earlier layers, for obtaining pure hydrogen product. High purity hydrogen product (>99%) with high recovery (>85%) was achieved with the PSA system for different hydrogen concentrations (5–30%) in the 30 bar feed stream. We also compared the PSA system against an electrolyzer generating hydrogen onsite. Our analysis suggests that the PSA competes favorably, even at a low hydrogen recovery of 40% in cases where the PSA plant is built at a pressure reduction station.

Original languageEnglish
Article number120094
Number of pages15
JournalSeparation and Purification Technology
Volume282
DOIs
Publication statusPublished - 1 Feb 2022

Keywords

  • Energy efficiency
  • Equilibrium isotherm
  • Hydrogen separation
  • Natural gas infrastructure
  • PSA

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