466622 The Development of Microchannel Reactors for Hydrogen Production: Experimentation and CFD Modelling

Tuesday, November 15, 2016: 4:05 PM
Taylor (Hilton San Francisco Union Square)
Raymond Everson, School of Chemical and Minerals Engineering, North-West University, Potchefstroom, Potchefstroom. 2520, South Africa, Hein Neomagus, North-West University, Potchefstroom Campus, South Africa, Potchefstroom, South Africa, Steven Chiuta, School of Chemical and Minerals Engineering, North-West University, Potchefstroom, South Africa and Dmitri Bessarabov, NWU, Natural Sciences, DST HySA Infrastructure Center of Competence, Potchefstroom, South Africa

A microchannel reactor for hydrogen production from ammonia is simulated with a three-dimensional (3D) CFD model using Comsol Multiphysics, in order to obtain a mathematical framework to understand the reaction-coupled transport phenomena associated with the microchannel reactor. The catalysts used consisted of commercial Ni-Pt/Al2O3 and Ru/Al2O3 catalysts in the form of a porous wash-coat deposited on the walls of the micro channels. The transport processes and reactor performance are elucidated in terms of velocity, temperature, and species concentration distributions, as well as local reaction rate and ammonia conversion profiles. The baseline case is first investigated to determine the behaviour of the microchannel reactor, then microstructural design and operating parameters are methodically altered around the baseline conditions to explore the optimum values. The simulation results show that an optimum ammonia space velocity (GHSV) yields 99.1% ammonia conversion and a power density of 32 kWe L-1 at the highest operating temperature of 973 K for the Ni-Pt based catalyst. It is shown that a 40-μm-thick porous wash coat is most desirable at these optimum conditions. Also a small channel hydraulic diameter (225 µm) is observed to contribute to high ammonia conversion. It is reported that the Ru/Al2O3 gives a superior yield than the Ni-Pt/Al2O3 at optimal conditions and that experimental and model results agree very well. The results obtained confirm that a catalytic microchannel reactor can be most desirable for small scale hydrogen production from ammonia, required especially for the operation of fuel cells.

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See more of this Session: Unconventionals: Hydrogen and Fuel Cells I
See more of this Group/Topical: Fuels and Petrochemicals Division