On-board hydrogen production for fuel cell vehicles via a membrane separator and an externally-fired methanol reformer

Many options exist for on-board hydrogen production from liquid fuels for fuel cell powered vehicles. This paper reports on design and construction of an on-board system for hydrogen production from methanol. Methanol reforming is accomplished using an externally fired catalytic reactor. Carbon monoxide, separated from the reactor effluent by a membrane separator, is consumed with the reactor fuel. The reactor is operated at 1950 kPa to supply gas to the membrane separator at its maximum design pressure, and at a temperature of 500°C, to minimize the amount of methanol remaining the reactor product. The design methanol feed rate of 0.32 1/min used for the prototype should be sufficient to supply a 10 kW fuel cell package, but the design can easily be expanded to larger sizes.

The membrane separator is an off-the-shelf, polymer-based model, and it is not expected to reduce the carbon monoxide to below 10 ppm, required by proton exchange membrane fuel cells, being considered for vehicular power. For this reason it is necessary to include a selective oxidation reactor to remove the carbon monoxide as a contaminant. An adiabatic energy balance indicates that 30% excess energy is available from combustion of the separated carbon monoxide when used as fuel to the reformer. The thesis includes the design of methanol reformer system, calculation of heat transfer coefficients and heat transfer areas required for the heat exchange of the exhaust gases and the reaction mixture. It also includes the simulation of the entire process using ChemCAD as a chemical process simulator.