Modeling of a Packed-Bed Reactor in a Sodium Borohydride Hydrogen Storage System

Sodium borohydride hydrogen storage systems offer great promise in meeting the challenges of hydrogen storage for automotive applications. The physical processes inside a NaBH₄ packed-bed reactor are complicated, involving multi-component, multi-phase, multi-mode heat and mass transfer. All of these processes are closely coupled with chemical reaction kinetics. To design and optimize the reactor, a detailed reactor model is needed. This study addressed this problem using a one-dimensional homogeneous model. The diffusion coefficient inside the catalyst and the water vapor mass transfer coefficient were obtained by fitting experimental data at a moderate flow rate and were used to predict reactor behaviors at other flow rates. The predicted temperature, conversion and relative humidity profiles match experimental data well although the pressure drops are underpredicted.