Evaluation of heat transfer coefficient between a reacting steam-methane mixture and preheated Ni-based catalyst

This work is devoted to the investigation of a heat transfer inside a steam methane reformer filled with pre-heated Ni-based catalyst pellets of various shapes. Various particle shapes were tested: spheres, cylinders and Raschig ring under various inlet steam-to-methane ratios. The chemical kinetics model is based on experimentally derived reaction rate expressions taken from the literature. The distinguishing feature of the developed model is unsteady flow (transient) of reacting mixture over pre-heated Ni-based catalysts for the following initial parameters: inlet velocity - 0.5-1.7 m/s, inlet gas temperature - 400-450 degrees C, temperature of the preheated catalysts - 927 degrees C. This model allowed us to investigate the effect of endothermic chemical reactions on heat transfer between the catalysts and gas flow. Moreover, two cases were tested to understand the heat transfer in the reformer: the chemical reaction was switched on and switched off in the model. It was established that the heat transfer coefficient for a reacting flow (approximate to 90W/(m2K)) is about twice higher than the heat transfer coefficient for a non-reacting flow.

Automated summary

This study investigates the heat transfer inside a steam methane reformer with different shapes of pre-heated Ni-based catalyst pellets. A chemical kinetics model based on experimentally derived reaction rate expressions is developed. The model considers the unsteady flow of reacting mixture over pre-heated Ni-based catalysts under specific initial parameters. It is found that the heat transfer coefficient for a reacting flow is approximately twice higher than that for a non-reacting flow.