Author(s)

M. C. Annesini, R. Augelletti, M. De Falco, S. Frattari, F. Gironi, M. A. Murmura

Abstract

Blends of hydrogen and methane (hythane) with 20–25% of H₂ can be used in internal combustion engines in order to reduce the CO₂ and unburned hydrocarbon emissions and greenhouse effect. In this paper we show that solar steam reforming of natural gas at 500–550°C is a suitable process to produce such a mixture, but the reformed gas must be purified to reduce the CO₂ concentration to less than 3%. To this aim, a first Pressure Swing Adsorption (PSA) unit, which uses activated carbon as adsorbent material, is proposed to remove carbon dioxide, with H₂ and CH₄ recovery of about 99 and 43%, respectively; to enhance CH₄ recovery, a second PSA unit, using carbon molecular sieve (CMS) as adsorbent, can be introduced. The whole suggested process produces an enriched methane mixture with a hydrogen content of 25%, with an energy consumption of about 270 kJ/kg of hydro-methane, mainly due to the electrical energy required for gas compression and vacuum pumps.

Keywords

hydrogen methane mixtures, solar steam reforming, pressure swing adsorption