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Abstract: Sorption enhanced methane reforming (SER), employing a CaO-based solid as a high temperature CO2 sorbent, is generally considered to be a promising route for H2 production. In this paper we present a dynamic pseudo-homogeneous model to describe the operation of a packed bed reactor in which the SER reaction is carried out under adiabatic conditions. This reactor can be implemented according to several process schemes, including a novel Ca/Cu looping process for hydrogen generation with inherent CO2 capture. The proposed SER model is based on the well-established principles of gas–solid contact and heat transfer in fixed-bed reactors and on the kinetic expressions published in the literature that describe the main reactions involved in the process. The resulting model describes the transient performance of the SER reaction and confirms the theoretical viability of this critical reaction stage in a large scale H2 production facility. It is demonstrated that the SER process can yield a CH4 conversion and H2 purity of up to 85% and 95%, respectively, under operating conditions of 923K, 3.5MPa, a steam/carbon ratio of 5 and a space velocity of 3.5kg/m2 s. [Copyright &y& Elsevier]

Abstract: The paper presents a model-based investigation of a metal hydride reactor applied as a solid state hydrogen storage device. The elements of a metal hydride reactor are hydrogen supply duct, internal hydrogen distribution, hydride bed, reactor shell and the flow domain of the heat transfer fluid. Internal hydrogen distribution and hydride bed are porous media. Therefore, hydrogen flows through non-porous and porous regions during its reversible exothermic absorption and endothermic desorption, respectively. The interface between porous and non-porous regions is a discontinuity with respect to energy transport mechanisms. Hence, Danckwerts-type boundary conditions for the energy balance equation are introduced. Application of the first and second law of thermodynamics to the interface reveals that temperature jumps may occur at the hydrogen inlet but are not allowed at the hydrogen outlet. Exemplarily the loading behavior of a metal hydride storage tank based on sodium alanate is analyzed. It is demonstrated and experimentally validated that only Danckwerts-type boundary conditions predict the important cooling effect of the inlet hydrogen on the exothermic absorption process correctly. [Copyright &y& Elsevier]