Heat transfer and storage performance of steam methane reforming in tubular reactor with focused solar simulator

Abstract

Steam methane reforming is suitable for thermochemical energy storage because of its large reaction enthalpy and high hydrogen content in reaction products. In this paper, heat transfer and storage performance of steam methane reforming in a tubular reactor heated by focused solar simulator is experimental demonstrated and numerically analyzed. According to experimental results, methane conversion remarkably decreases with inlet flow rate rising, while thermochemical energy storage efficiency first increases for more reactants and then decreases with methane conversion dropping. As incident energy flux rises, methane conversion increases with bed temperature rising, and the thermochemical energy storage efficiency reaches its maximum of 11.3% with central heat flux of 285.6 kW/m2. Three-dimensional transport and volumetric reaction model with concentrated energy flux boundary condition is established and validated, and local and integral energy transport and storage performance are further analyzed. Along flow direction, the maximum reaction rate appears before the focal point with maximum energy flux. The tendencies of methane conversion and thermochemical energy storage efficiency are very similar under different inlet conditions, and higher inlet temperature and appropriate steam to methane ratio benefit thermochemical energy storage. The structures of catalyst bed and reactor are critical important for thermochemical energy storage process. As bed length increases, the methane conversion and thermochemical energy storage efficiency first increase with the increase of positive reaction and then decrease with the increase of reverse reaction, and the optimal length is a little larger than focal spot diameter. When bed porosity is increased, the methane conversion and thermochemical energy storage efficiency first increases with the flow resistance decreasing and then decreases with catalyst amount decreasing, and optimal porosity is 0.45. Heat loss in heating side of bed region play major role in heat storage, and the thermochemical energy storage efficiency can be improved to 34.8% by using insulation and coating.