Purification of Hydrogen-Methane Mixtures Using PSA Technology

Abstract

Mixtures of hydrogen-methane (hydromethane), composed of 20-30 % vol. hydrogen, are considerably interesting, especially in the field of sustainable mobility, because their energy content is higher than that of pure methane; moreover, the carbon dioxide emissions due to the combustion are reduced. The production of such mixture can be effectively carried out by means of steam reforming of natural gas (97 % methane and 3 % carbon dioxide) at 500-550 °C. However, the reformed gas must be purified in order to reduce the carbon dioxide concentration (lower than 3 %). The pressure swing adsorption technology, which uses activated carbon as adsorbent material, may be employed to remove carbon dioxide and to obtain a high recovery of hydrogen and methane. To improve the recovery of methane, a second pressure swing adsorption unit, which uses carbon molecular sieve as an adsorbent, can be introduced.