A three-dimensional simulation of a mid-and-low temperature solar receiver/reactor for hydrogen production

• A thermochemical solar reactor/receiver with a porous catalyst bed is investigated.
• A three-dimensional model is proposed to study the thermochemical performances.
• Influence laws of key operating parameters on thermal performances are revealed.
• Effects of the solar flux distribution on thermochemical process is expounded.

The solar receiver/reactor is a key component that influences the conversion efficiency in the solar thermochemical process. A thermochemical solar reactor/receiver consisting of a porous Cu/ZnO/Al2O3 catalyst bed is studied in this paper. A three-dimensional thermochemical coupling model that incorporates the fluid flowing through the porous catalyst bed and energy conservation equations coupling the radiation/convection/conduction heat transfer with the reaction kinetics is proposed to investigate the performances of the receiver/reactor. The factors of influencing the hydrogen production and the temperature distribution, including the mole ratio of water/methanol, the solar radiation and the inlet temperature, are numerically investigated. Numerical simulation results indicate that the deactivation of the catalyst may appear near the receiver/reactor tube wall. The methanol conversion decreases with the increase of the methanol feeding rate, and the low inlet methanol feeding rate should be avoided for the protection of the catalyst bed. A new solar receiver/reactor is proposed by changing the aperture width along the flow direction to make the concentrated solar energy level match the chemical reaction. Compared with traditional solar receivers/reactors, the thermochemical efficiency can be increased by 3% points. The research findings will pave the way for the future development of the mid-and-low temperature solar receiver/reactor.