An integrated approach for the production of hydrogen and methane by catalytic hydrothermal glycerol reforming coupled with parabolic trough solar thermal collectors

An integrated catalytic hydrothermal reforming process for the production of hydrogen and methane from wet biomass feedstock is proposed where the process heat is provided by molten salts previously heated by solar energy. The simulated reactor consists of double tubes in which the reactants and the heat transfer fluid (i.e. molten salts) are concurrently pumped through the inner and the outer tubes, respectively. The first section of the reactor essentially serves as a preheater to increase the feed temperature to 20 K below the desired reaction temperature (i.e. 773 K), while the second section is comprised of a catalyst appropriate for the reforming of glycerol and water-gas shift reaction (e.g. Ru and Ni catalysts). The required energy for heating up the reactants to the final reaction temperature in the preheating section as well as the heat of reaction needed throughout the catalyst bed is provided by a co-currently fed molten salts mixture previously heated to 823 K in parabolic trough solar collectors. After heat recovery, the product mixture is cooled down to ambient temperature and depressurized to form liquid and gas phases. The gas products are subsequently separated into hydrogen, methane, and carbon dioxide or can be alternatively used for electricity generation using solid oxide fuel cells (SOFC). Glycerol was considered as a biomass model compound throughout this study, but the same methodology with minor changes can be applied to other oxygenated biomass compounds such as carbohydrates. The simulation results indicated that the degree of heat recovery has considerable effects on the process efficiency, the required parabolic mirror area, and the corresponding molten salt flow rate. Also, the higher the extent of the heat recovery, the smaller the dependence of the overall efficiency to the feed concentration.