Computational fluid dynamics modeling of reactive multiphase flow for suspended photocatalytic water splitting of hydrogen production system

Suspended photocatalytic water splitting for hydrogen production is one of the most promising method for large-scale utilization of renewable energy in the future, and it is a complex reactive multiphase flow system involving radiation field. In this study, a computational fluid dynamics model of reactive multiphase flow for the photocatalytic tubular reactor with solar concentrator used for hydrogen production was developed. This model integrated multiphase flow, radiation field and reaction kinetics in an Eulerian framework using Cd_0.5Zn_0.5S as photocatalyst, in which the numerical results agreed well with the experimental data. The hydrogen production rate had been developed by the experimental results and expressed in term of a modified Langmuir-Hinshelwood type equation. The intrinsic photocatalytic hydrogen production rate constant independent of radiation intensity, reaction temperature and reactant concentration was obtained, which was 0.328 m²·W⁻¹·min⁻¹. The radiation field inside the reactor was solved by a discrete method combined with the optical properties of the reaction solution. The distribution characteristics of the radiation and multiphase flow inside the reactor were obtained and analyzed. The catalyst particles had different degrees of precipitation in the flow path, especially in the range of −18.04 ~ −20.25 mm along the height direction. The radiation in the reactor was mainly concentrated at the small ranges of 180° ± 30° and 0° ± 30° along the circumference. The establishment of the integrated model provides possibilities for the design improvement of photocatalytic reactor and the optimal operation of system in the future.