National Research and Development Institute for Cryogenics and Isotopic Technologies - ICSI Rm. Valcea, Uzinei Street no. 4, P.O. Box Râureni 7, 240050, Râmnicu Vâlcea, Romania

ABSTRACT

A numerical analysis regarding the hydrogen generation from sodium borohydride (NaBH₄) by hydrolysis is presented in this paper. The hydrolysis of NaBH₄ allows a high-purity hydrogen generation, making it the ideal candidate for refuelling a PEM fuel cell stack of a portable energy system. There are many factors that can influence the hydrolysis process, such as catalyst usage, reaction temperature, NaBH₄ concentration, pH of the solution, excess of water. The paper was intended to give an insight into kinetics mechanism of NaBH₄ hydrolysis and to set up the mathematical model required to analyse the factors that can influence and maximize the hydrogen generation. Therefore, COMSOL MULTIPHYSICS software was used to implement the one dimensional mathematical model and to identify the effects of reaction mixture temperature on the hydrogen generation and on the NaBH₄ depletion. It was found that at room temperature (293 ºK) the complete depletion of NaBH₄ (maximum H₂ generation) occurs almost 7 times slower than at 323ºK.

Keywords: NaBH₄ hydrolysis, H₂ generation, mathematical modelling, batch reactor.