Extraction of Hydrogen from Water Using CeO₂ in a Solar Reactor Using a Concentrated Flux of Solar Radiation

Abstract

In this article, the thermophysical parameters of a cylindrical reactor with inner radius R_i = 32.5 mm, outer radius R_o = 42.5 mm, and length L = 100 mm was evaluated, and the thermochemical process based on CeO₂/CH₄ proceeding in it was considered. Various materials were considered for the construction of the reactor, and the most suitable one was chosen. In this case 304 stainless steel was selected for the reactor. It is determined that the values of heat transfer and heat return of the reactor depend on temperature. In this case, the thermal conductivity varies from 91.5 to 64.8 W/(m² K) at a temperature of 300–650 K and from 64.8 to 85 W/(m² K) at a temperature of 650–1400 K. It has been established that the value of heat transfer varies within 686.5–962.3 W/(m K) in the temperature range 300–1400 K. It is established that this reactor consumes energy from 17.5 to 70 kW, depending on the temperature change during operation. In the temperature range of 700–1400 K, the efficiency of absorption of solar radiation by the reactor decreases from 99.6 to 92.8%. The method of hydrogen production using CH₄ and CeO₂ thermochemical cycles was analyzed. Heat balance equations for endothermic and exothermic processes of the thermochemical cycle have been studied. It was determined that Q_min = 373 kJ/mol and Q_max = 400 kJ/mol and energy is required for this thermochemical process in the temperature range of 700–1400 K. In this case, the optimum for a good separation of hydrogen is a temperature in the range of 1000–1250 K. In this temperature range, the maximum separation of products occurs in a mixture of methane and cerium oxide.