Thermodynamic Possibilities of Pure Hydrogen Production by Chromium, Nickel and Manganese-based Chemical Looping Process at Lower Temperatures

Hydrogen is expected to become an important energy carrier for sustainable energy production, transformation and consumption with reduced impacts on the local and global environment. Development of hydrogen based energy and transport systems needs reliable and inexpensive methods of relatively pure hydrogen production, storage and supply. Iron as a common metal was suggested for hydrogen production by reaction with steam at higher temperatures [1]. The basic principle of the cyclic iron sponge process is to reduce iron oxides with the reducing gases (H2, CO, CH4 etc.) utilizing metallurgic knowledge of iron oxides reduction and to oxidize the iron by steam for hydrogen supply. In this process a syngas (e.g. from biomass gasification [2]) or a gas mixture from steam reforming of hydrocarbon fuels can be converted into relatively pure hydrogen [3]. The main disadvantage of iron in the redox cyclic process of hydrogen production is, however, the possibility of soot , Fe3C and FeCO3 formation in the reduction process by CO and CO2 containing gases. Such carbon precursors lead to the production of hydrogen with carbon containing impurities in the steam oxidation step. Relatively cheap and common alloying elements Cr, Ni and Mn have been chosen for the basic thermodynamic study with respect to compatibility with iron and lower tendency for carbide and carbonate formation.JRC.F.2-Cleaner energie