Pd-based packed bed membrane reactors (PBMRs) have many advantages for high purity hydrogen generation as compared to conventional packed bed reactors (PBRs). Membrane reactors can be especially beneficial for on-board reforming of fuels for fuel-cell vehicles. Our previous studies have focused on methanol steam reforming and ammonia decomposition in Pd-based membrane reactors [1, 2]. We have carried out single-fiber PBMR studies for these reaction systems. For methanol steam reforming we have also developed a multi-site adsorption model which successfully predicts the drop in trans-membrane hydrogen flux due to adsorption of non-H2 reaction species on the membrane surface . Using this model we have developed 2-dimensional models which have successfully predicted the performance of the single-fiber PBMRs.
In the current study we have used these previous results to develop a 3-dimensional model for large-scale multi-fiber PBMRs. This 3-D model has been used to study the effect of various design (reactor diameter, no. of Pd-alloy fibers, spacing between fibers etc.) and operating parameters (temperature, pressure, residence time, inlet composition etc.) on the productivity and utilization of hydrogen. These results will be presented along with proposed optimized designs for commercial membrane reactors. Rate limiting steps and general design principles will also be discussed.
1. Israni, S.H., Nair, B., and Harold, M.P., “Hydrogen Generation and Purification in a Composite Pd Hollow Fiber Membrane Reactor: Experiments and Modeling,” Catalysis Today,139, 299-311 (2008) 2. Israni, S.H., and Harold, M. P., ‘Methanol steam reforming in Pd-Ag membrane reactors: Experiments and modeling of single-fiber packed bed membrane reactor', In preparation 3. Israni, S.H., and Harold, M.P., ‘Methanol steam reforming in Pd-based membrane reactors: Effects of reaction system species on hydrogen flux through a Pd-Ag¬ membrane', accepted Ind. Eng. Chem. Res.