Prediction of Levels of CO Contamination in Methanol-Steam Reformate Gas for PEM Fuel Cell Power Systems 1999-01-2571

Initially simple first-order rate equations that predicted the rate of disappearance of methanol were used. The firstorder rate constant, however, depended on pressure and steam-to-methanol molar feed ratio (S/M) indicating the inadequacy of this approach. An attempt was made to improve on the simple first-order expression by including the reverse (synthesis) reaction and proposing an empirical expression for the concentration of CO in the product gas as a function of S/M and the methanol fractional conversion. A comprehensive kinetic model consisting of three rate expressions for each of three separate overall reactions has been developed. This model is able to predict the production rate of CO₂, CO and H₂ and is also reversible so that the equilibrium at high pressure is taken into account. The rate expressions have been utilised in reactor design and analysis studies and have been used to predict methanol conversion and product composition over a wide range of pressures (1-35 bar) and space velocities. These mechanistic kinetic equations have been shown to be effective for system modelling and design as well as trouble-shooting operational problems.