A mathematical model based analysis for designing demo scale fuel processor

Abstract

The aim of this study is to construct a FLUENT-based mathematical model of a Demo-scale fuel processor, which will be used as the base model to obtain the optimum operating parameters of a Demo-FP that produces sufficient amount of PEM-grade H2, having CO concentration below 100 ppm, from methane in amount enough to feed a 1 kW PEMFC. In the first part, the power law type kinetic expressions obtained from kinetic studies for the FP reactions (OSR-WGS-PROX) were corrected through minimizing the difference between experimentally obtained performance test results and the results obtained from the mathematical model formed in the current study for the same reaction conditions. In the second part, the fuel processor prototype (FPP) was modeled and its performance was simulated through the use of corrected kinetic models. 16 FPP simulations of the OSR reactor were performed by using the feed composition, temperature and W/F used in the first part. First, FP reactors having ¼ inch-OD were modeled in series. Then, the same simulations were performed for 1 inch-OD of the reactors, which is the OD of the reactors has been planned to be used in Demo-FP, while the catalyst bed height of each reactor were kept fixed as in the case of ¼ inch reactors; in those simulations, the catalyst amount and the flow rate of the OSR feed was increased such as to keep W/F of the OSR reactor the same as that of the ¼ inch reactor case. Finally, the reaction conditions yielding the best performance in terms of H2 and CO level at the PROX outlet (the simulations with 400 oC OSR reactor temperature) were selected. For the selected sets, the catalyst amounts in the reactors increased while keeping the W/F fixed such as to satisfy the H2 flow of 0.00272 moles/s and CO concentration of 100 ppm. In the last part, the operation of individual OSR reactor was further simulated for granule-size technical catalyst via introducing several levels of effectiveness factor to the power-law type OSR kinetic expression. The required catalyst amounts and the pressure drop values for the particle diameters and effectiveness factors studied were calculated. The bed density change with the change in particle size was almost insignificant, and consequently almost the same bed lengths were found. On the other hand, as the particle diameter was increased, the pressure drop was reduced sharply.