DYNAMIC MODELING OF MEMBRANE REACTOR PRODUCING HYDROGEN FROM STEAM REFORMING

Abstract

A mathematical model for reformer reactor with membrane reactor that is composed of two channels separated by membrane is developed for methane steam reforming. Steam reforming takes place in reformer on a Ni/MgO–Al2O3 catalyst layer and required product, hydrogen, passes through the membrane layer. The combination of highly endothermic reforming reaction and mildly exothermic shift reaction takes place in main body of reactor which leads to continuous temperature drop through the length of reactor. To maintain the temperature of reactor, feed is preheated. Selective permeation of hydrogen through the palladium membrane is achieved by co-current flow of sweep gas through the second channel. The mass and energy balance equations for the thermally coupled membrane reactor form a set of 13 coupled partial differential equations. With the application of appropriate boundary conditions, the distributed dynamic reactor model is solved as a boundary value problem. The model equations are discretized using forward difference method on finite elements. The discretized nonlinear modeling equations, along with the boundary conditions, form a system of algebraic equations that are solved in C++. The performance of the reactor is numerically investigated for various key operating variables such as inlet fuel concentration, inlet steam/methane ratio, inlet reformer gas temperature and inlet reformer gas velocity. For each case, the reactor performance is analyzed based on methane conversion and hydrogen recovery yield.