Title : Mathematical model of a solar irradiated monolithic reactor
Abstract:
Solar-aided hydrogen production seems an interesting solution in the transition towards a carbon-free energy future. In this context, redox materials are employed to directly dissociate water in extremely high temperature processes (T>1000oC), where the required energy is provided via concentrated solar energy. Depending on the redox material and out of the variety of the possible routes, solar thermochemical hydrogen production using non-stoichiometric, non-volatile redox materials in a two-step process is of paramount interest. The material undergoes consecutive cycling between its reduced and oxidized state, thus hydrogen and oxygen are separately produced.
The current computational work investigates the performance of a solar irradiated monolithic reactor. The model considers nickel ferrite as the active material but is capable of describing any non-stoichiometric, non-volatile redox material. Due to the symmetry of the geometry, the simulation of single channel of the monolith is representative of the entire reactor. Furthermore, taking advantage of the characteristics of the honeycomb monolithic structures, low-dimensional modelling suffice to assess the flow regime inside the reactor. The developed model incorporates the energy conservation equations for the gas and the solid phase, the surface coverage evolution and the species conservation equations. The system of the coupled differential equations is solved using finite difference numerical methods, under steady state and dynamic conditions. Furthermore, the algorithm takes into account an in-house kinetic model that has already been developed [1] and is capable of accurately describing the evolution curves of the products under various operational conditions. The parametric study investigates the impact of the critical parameters on the performance of the process, while different scenarios (both thermal and chemical) are simulated in order to increase the productivity of the product yield.
