Abstract
In the present study, a two-dimensional (2D), nonlinear, and pseudo-homogeneous mathematical model of a fixed-bed catalytic reactor with an integrated membrane for the methane steam reforming over a nickel- based catalyst is developed. A permselective Pd based membrane is used in order to remove hydrogen from the reaction zone and shift the equilibrium towards hydrogen production thus enabling the achievement of a high methane conversion. The nickel-based catalyst allows for significantly low operating temperatures (less than 550 °C) than conventional methane reforming. The necessary heat for the initiation and preservation of the reactions is supplied to the reactor through an external source. Themathematical model is based on rigorous mass, energy, and momentum balances, where both axial and radial gradients of mass and temperature are fully considered. Hydrogen flux through the membrane is calculated by Sieverts law where the driving force is the hydrogen partial pressure difference between the two sides of the membrane. Results referring to the distribution of species and methane conversion along the reactor and temperature and hydrogen flow rate along the reactor for different radial positions are obtained and analyzed. Furthermore, sensitivity analysis on the effect of different wall temperatures (500 °C, and 550 °C) and operating pressures (1, 5, and 10 atm) show that in a membrane reactor methane conversion (60.24 % at 10 atm) can reach similar values to that in a traditional reactor (61.21 % at 10 atm and 700 °C) at significantly lower temperatures (550 °C).
