Study of ammonia decomposition system for hydrogen production driven by medium–low temperature solar energy

Abstract

Ammonia decomposition for hydrogen production powered by medium–low temperature solar energy is an effective way to enhance the utilization of solar energy and alleviate the energy crisis. To improve the ammonia conversion rate and study the effect of each parameter on the reactor’s performance, a multi-physics coupled model of a fixed-bed ammonia decomposition reactor driven by medium–low temperature solar energy is established. The thermochemical performance of the reactor and the influence of the non-uniform distribution of solar heat flux in the circumferential direction on the ammonia decomposition reaction is analyzed. The results indicated that the temperature difference at the catalytic bed cross-section will increase, but the ammonia conversion rate and the solar thermochemical efficiency are less affected. After that, direct normal irradiation, the ammonia inlet mass flow rate, and the outer radius of the reactor are studied in relation to the ammonia decomposition reaction. The ammonia conversion rate can be enhanced by increasing direct normal irradiation and the reactor’s outer radius, reducing the ammonia inlet mass flow rate. The optimal reaction conditions are obtained: the direct normal irradiation is 600 W/m², the ammonia inlet mass flow rate is 12 kg/h, and the reactor’s outer radius is 35 mm. Based on the method by which solar-driven ammonia decomposition for hydrogen production can convert low-quality solar thermal energy into high-quality chemical energy, a combined cooling, heating and power system with integrated solar-driven ammonia decomposition for hydrogen production is proposed. And its thermodynamic performance is analyzed. The results show that the fuel saving rate of the system is 28.83 % when ammonia conversion rate is 87.12 %, which is beneficial for the efficient utilization of energy.