Comprehensive study on novel parabolic trough solar receiver-reactors of gradually-varied porosity catalyst beds for hydrogen production

In this paper, novel parabolic trough solar receiver-reactors (PTSRR) of gradually-varied porosity catalyst beds are proposed for cost-efficient hydrogen production. A three-dimensional comprehensive model was developed for PTSRRs of the methanol-steam reforming reaction (MSRR) in porous Cu/ZnO/Al₂O₃ catalyst packed beds, by combining the finite volume method (FVM) and the Monte Carlo ray-tracing (MCRT) method with a MSRR comprehensive kinetic model. The validated model was applied to investigate different novel PTSRRs proposed, as well as the effects and mechanisms of different non-uniform porosity distributions, taking the methanol flow rate, the catalyst temperature limitation and the solar flux nonuniformity into account. It is revealed that the catalyst particles packed in the top part of the traditional absorber-reactor may not only have not fully played their roles but also influenced the multicomponent gas mixture fluid flow and heat transfer greatly. The non-uniform porosity catalyst bed gradually-increased from the bottom to the top better matches previously non-uniform temperature distributions and thus makes PTSRRs operated more safely, more efficiently yet lower cost of locally less packed catalyst mass. This comprehensive model and method offers a useful option of high potential for comprehensive analyses of the whole photo-thermal-chemical conversion process for different PTSRRs and realistic conditions.