A CFD-based parametric study on the effect of burner position and reformer tube numbers in a steam methane reforming reactor for hydrogen production is presented in this work. Three different burner configurations such as single co-axial inside burner (SCIB), single top burner (STB), and multiple top burner (MTB) arrangements were considered. The number of reformer tubes inside the reactor varies with the four, six, and eight tubes arrangement. A three-dimensional CFD model was build and a symmetric model is considered for analysis. For simplifying the analysis, the catalyst medium in which the steam methane reaction occurs was modeled as a porous medium with appropriate surface area to volume ratio of the catalyst from the literature. The reaction rate in the porous medium inside the reformer tube was defined by Xu and Forment model and these reaction rate equations were coupled to the CFD governing equations through user-defined functions. Commercial CFD software, ANSYS FLUENT is used to solve the equations. The temperature of the reactant gases to the reformer tube inlet was given as 650 K and the steam to methane mole ratio was set as 3. The operating pressure was chosen as 2 bar. Three different reactants reformer inlet velocities of 1 m/s, 2 m/s, and 3m/s were analyzed in this work. The final solution from the different CFD models were evaluated in terms of temperature distribution inside the combustion space and the mole fraction of hydrogen generation. The results from the CFD study revealed that there was a large significant temperature gradient exists in the steam methane reforming reactor. This temperature gradient along the reformer tube length results in the reaction rate variation and finally the hydrogen production. When compared with the STB, and MTB arrangements, the temperature gradient was observed to be significantly larger for SCIB arrangement. The supplied heat from the combustion gases were not completely utilized in the hydrogen production for the case of SCIB configuration. The standard deviation values of the temperature in the central cross plane of the combustion domain were observed to be lower for the STB arrangement when compared to the other two arrangements. The reformer inlet velocity also found to have a huge influence on H2 mole fraction and temperature distribution along the reformer tube. The increase in the reactant gas inlet reformer velocity beyond 3 m/s impacts the H2 mole fraction greatly due to the low resident time of the reactant gases inside the catalyst layer for the specified operating conditions. The number of installed reforming tubes found to have a negligible influence on the H2 mole fraction at the catalyst layer’s exit. But increase in the number of reformer tubes leads to better performance with effective utilization of heat in hydrogen production from the catalyst layers.

Numerical Study of the Effect of Burner Position and Reformer Tubes on the Design of an Annular Steam Methane-Reforming Reactor for Hydrogen Production

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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