Single stage H2 production, purification and heat supply by means of sorption-enhanced steam reforming of glycerol. A thermodynamic analysis

Abstract

The effect of CO2 removal with CaO in the production and purification of fuel cell-grade H2 by glycerol steam reforming is studied from a thermodynamic point of view. Results obtained with the non-stoichiometric method show that CaO enables some improvements to the conventional steam reforming since four simultaneous processes take place at the same stage: H2 production, CO2 separation, CO elimination and heat supply: by separating the CO2 from the gaseous mixture, CaO also shifts the equilibrium towards the production of H2 compared to conventional reforming, and the operating temperature is lowered with respect to conventional steam reforming. The removal of CO2 not only enables higher H2 purity (close to 100% on dry basis) but reduces the amounts of CO as well. For temperatures below ca. 750K, a level lower than 20ppm (on dry basis) can be reached, thus avoiding the need of a purification stage. Since the reaction of CaO with CO2 is exothermic, the heat is supplied within the reactor. Finally, it was found that the system behavior was strongly dependent on the presence of Ca(OH)2.This four-in-one process can be a way of enhancing the efficiency of the overall system of production-purification of H2.