Operation of a PEM stack with high impurity anode feeds in a recycle mode

A Ballard PEM stack (Nexa™ power module) was utilized in this work, providing 1200 watts of unregulated DC power at a nominal output voltage of 26 VDC. In deference to normal operational procedures, high levels of inert gases were deliberately added to the anode feed. Fuel exhaust management in the Nexa™ system was carried out by adding a manual exhaust line into the exterior fuel exhaust purge line. This exhaust management system provided the opportunity to optimize the exhaust flow rate and increase system efficiency in a recycle mode. This type of operation provides a dual use of membranes in the MEAs as both gas purifier and as solid electrolytes. The PEM stack was successfully operated with up to 7.5% nitrogen in the absence of a palladium-based hydrogen separator. In further experiments, a hydrocarbon reformate containing high levels of CO ₂ and H ₂O was also used in the Nexa™ stack after troublesome CO and H ₂S poisons were removed. Both fuels successfully ran the Nexa™ stack. Recycle operation may be used to reduce the size and complexity of the fuel processing system at a specified power level.