STUDY OF METHANE STEAM REFORMING IN A THERMALLY COUPLED PALLADIUM MEMBRANE REACTOR

Abstract

In the present work, process intensification principles are applied to steam reforming process used for production of hydrogen. Three different processes are combined in a single unit. Steam reforming of methane is coupled with methane combustion to provide necessary heat for endothermic reforming reaction. Also, the reforming reaction equilibrium is tilted towards higher hydrogen production using Pd and Fe membranes in sweep gas channel to facilitate continuous removal of hydrogen. It results in higher conversion of methane and higher hydrogen yield. A mathematical model for autothermal reformer coupled with membrane reactor that is composed of three channels is developed for steady state operation of methane steam reforming unit. The mass and energy balance equations for the thermally coupled membrane reactor system form a set of 22 coupled ordinary differential equations including 6 second order differential equations. Applying appropriate boundary conditions, the distributed reactor model for steady-state operation is solved as a boundary value problem (BVP). The model equations are discretized using orthogonal collocation after dividing reactor length in five parts. The discretized nonlinear modeling equations, along with the boundary conditions, form a system of algebraic equations that are solved using the LSQNONLIN method in MATLAB. The performance of the reactor is numerically analyzed for different key operating variables such as inlet fuel concentration, inlet steam/methane ratio, and inlet reformer gas temperature and inlet reformer gas velocity. For each case, the reactor performance is studied based on methane conversion and hydrogen recovery yield.