A dynamic study of steam-methane reforming

Experiments have been performed on the catalysed steam reforming of methane in a computer-controlled micro-reactor over the temperature range 600-840 degrees C and the pressure range 2.5-9 aims. gauge. The principal operating method was dynamic in nature in which operating conditions were changed by computer program from the initial conditions to a second and sometimes a third or fourth set. The reactor inputs were continuously measured by flow micro -controllers, and effluent flows were analysed by chromatography recorded at 15 min intervals over the period of an experiment. The total reaction period for more than 100 experiments was 600 h. Differential equations were set up to describe the axial composition profiles. Estimates of the kinetic constants were obtained from the entrance flows and exit reactor concentrations for each experiment. A variability in the catalyst activity was found at temperatures less than 800 degrees C apparently due to activation of the catalyst at lower temperatures when there was an earlier period of operation at higher temperatures. Once the experiments affected by temperature activation had been excluded the experiments were found to be consistent in reproducing the effect of temperature, pressure, and composition. Rate equations for the two dominant reactions were then obtained by functional analysis and non-linear parameter estimation from the flows and compositions for each consistent experiment. (c) 2006 Elsevier Ltd. All rights reserved.