Kinetics, simulation and optimization of methanol steam reformer for fuel cell applications

To evaluate reaction rates for making hydrogen from methanol, kinetic studies of methanol decomposition, methanol steam reforming, the water gas shift reaction, and CO selective oxidation have been performed. These reactions were studied in a microreactor testing unit using a commercial Cu-ZnO/Al2O3 catalyst for the first three reactions and Pt-Fe/gamma-alumina catalyst for the last reaction. The activity tests were performed between 120 and 325 degrees C at atmospheric pressure with a range of feed rates and compositions. For methanol decomposition, a simplified reaction network of five elementary reactions was proposed and parameters for all five rate expressions were obtained using non-linear least squares optimization, numerical integration of a one-dimensional PFR model, and extensive experimental data. Similar numerical analysis was carried out to obtain the rate expressions for methanol steam reaction, the water gas shift reaction, and CO selective oxidation. Combining the three reactors with several heat exchange options, an integrated methanol reformer system was designed and simulated using MATLAB. Using this simulation, the product distribution, the effects of reactor volume and temperature, and the options of water and air injection rates were studied. Also, a series of optimization tests were conducted to give maximum hydrogen yield and/or maximum economic profit. (c) 2004 Elsevier B.V. All rights reserved.