Numerical investigation of hydrogen production from methane for small scale stationary PEM fuel cell applications

Abstract

The steady-state behaviour of the fuel processor system consisting of a catalytic indirect partial oxidation reactor (combined total oxidation/steam reforming), a water-gas shift converter and a preferential carbon monoxide oxidation reactor for conversion of methane to hydrogen for use in small scale fuel cell applications is investigated using computer-based modeling/simulation techniques. Steady-state simulation and sizing of reactors, which are considered to be packed-bed tubular type, are carried out for six different feed ratio ((methane/oxygen, steam/methane) = (2.24, 1.17), (1.89, 1.56)) /PEMFC power output (500, 1000, 1500 W) configurations. Material balance calculations are executed to obtain the flow rates of each species at each stream. These results are then used in reactor modeling and simulation studies as boundary conditions to estimate the size of the reactors in terms of catalyst weight. A one-dimensional pseudohomogeneous reactor model is used for modeling and simulation purposes. Reactor dimensions and catalyst particle diameter are then estimated by using a set of criteria to quantify interfacial heat and intraparticle mass 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. Catalyst quantity in each reactor is found to increase almost linearly with the power output of the PEMFC at both feed compositions. Lengths and diameters estimated for IPOX, WGS and PROX reactors are also found to increase with increasing PEMFC power output. Total system volume, excluding the piping, pumping and heat exchange units, is estimated to be 0.49, 0.98 and 1.51 liters for 500, 1000 and 1500 W of PEMFC power outputs, respectively.