Methanol Evaporator and Hydrogen Combustor

Tonkovich et al. [123] claimed a 90% size reduction due to the introduction of micro channel systems into their device, which made use of the hydrogen off-gas of the fuel cell anode burnt in monoliths at palladium catalyst to deliver the energy for the fuel evaporation. A metallic nickel foam 0.63 cm high was etched and impregnated with palladium to act as a reactor for the anode effluent It was attached to a micro structured device consisting of liquid feed supply channels and outlet channels for the vapor, the latter flowing counter-flow to the anode effluent 

A bench-scale evaporator was built first, consisting of the nickel foam monolith and heat exchanger plates 5.7 cm wide and 7 cm long. The stainless-steel channels fabricated by EDM were 254 pm deep and the vapor channel depth was varied from aspect ratios of 4 to 18, the latter being the optimum value determined by experiments. 

At Pd loadings of 5 wt.%, 80-90% hydrogen conversion was found for a synthetic anode effluent containing 6.7% hydrogen and 3.35% oxygen. The heat exchanging efficiency of the bench-scale evaporator increased linearly with the aspect ratio of the vapor channels and reached 92% at an aspect ratio of 18. 

The full-scale reactor/evaporator had a total size of 7.6 cm x 10.2 cm x 5.1 cm and was composed of four monoliths of 5 cm2 cross-sectional area and four heat exchangers with 7.2 cm3 cross-sectional area. This device was claimed to evaporate 

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