Design of bench-scale methane processing reactors for hydrogen-driven PEM fuel cells

Abstract

The steady state behaviour of conversion of methane to hydrogen in the fuel processor system is investigated using computer-based modeling/simulation techniques for use in small scale fuel cell applications. The fuel processor system is consisted of a catalytic indirect partial oxidation reactor, (combined of total oxidation, steam reforming and water gas shift reactions), a water-gas shift converter, and a preferential oxidation reactor. Steady-state simulation and sizing of packed-bed tubular type reactors are carried out for six different feed ratio configurations: ((methane/oxygen, steam/methane) = (2.24, 1.17), (1.89, 1.56))/PEMFC power output (10, 50, 100 W). Material balance calculations have been carried out to obtain boundary conditions used in the reactor simulations which have been carried out using one-dimensional pesudohomogeneous reactor model. The model equations give the size of reactors in terms of catalyst weight. Reactor dimensions and catalyst particle diameter are then estimated by using a set of criteria to quantify intraparticle mass and interfacial heat transfer resistances and flow behaviour in packed beds. Total pressure change along the reactor tube is also checked such that the dimensions do not lead to excessive pressure drop. At both feed compositions, catalyst quantity in each reactor is found to increase linearly with respect to power output size of PEMFC. Consequently, lengths and diameters for IPOX, WGS and PROX reactors are also observed to increase with growing PEMFC output. Total reactor volumes to operate 10, 50, 100 W of PEM fuel cell, are estimated to be 7.36 cm3, 38.05 cm3, 83.52 cm3 respectively. In addition, a bench scale laboratory prototype to operate 10W PEMFC has been proposed using simulation results.