Production And Purification Of Hydrogen-methane Mixtures Utilized In Internal Combustion Engines
Free (open access)
535 - 545
M. C. Annesini, R. Augelletti, M. De Falco, S. Frattari, F. Gironi, M. A. Murmura
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.
hydrogen methane mixtures, solar steam reforming, pressure swing adsorption