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Wash Coat Selective CO Methanation Catalyst onto a Two Phase-Heat Exchanger to Replace Both PrOx1 and PrOx2 Reactors For CO Clean up in a PEM Fuel Cell Power Plant

IP.com Disclosure Number: IPCOM000206124D
Publication Date: 2011-Apr-13
Document File: 2 page(s) / 61K

Publishing Venue

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Abstract

A 2-phase heat exchangers (HEX) methanation reactor has a wash-coated catalyst and replaces a number of components in current fuel processing systems.

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Title:

Wash Coat Selective CO Methanation Catalyst onto a Two Phase-Heat Exchanger to Replace Both PrOx1 and PrOx2 Reactors For CO Clean up in a PEM Fuel Cell Power Plant

Abstract:

A 2-phase heat exchangers (HEX) methanation reactor has a wash-coated catalyst and replaces a number of components in current fuel processing systems.

 

Discussion:

The preferential oxidation (PrOx) reactor system (including mixers and HEXs) accounts for more than half of the volume of current fuel processing systems. In addition to the coolant control loop (valves and pumps), a mixer and air flow controller before PrOx1 and 2 are needed for introducing air and controlling the inlet T. Signals that control the PrOx temperature, especially during turndown, are a challenge for the current fuel cell power plants for both commercial and transportation programs. Another problem of current Fuel Processing System is that the steam/carbon ratio of reformer is limited, and can not go higher without adding another steam generator. Thus, it will be of great value to develop a more compact and efficient CO clean-up system with passive control and meanwhile generating additional steam for the reformer. The following disclosure provides a new 2-phase HEX methanation reactor to simplify and reduce the cost of a fuel processing system (FPS).

It is well known that both CO and CO2 can react with H2 to form CH4 in Pt-Ru type of catalyst.  CO is more reactive than CO2, and thus there is 20~50ºC temperature window for selectively methanizing CO without CO2 methanation. The reason one does not use methanation to clean-up the last bit of CO in the current FPS is because the methanation reaction is a strong exothermic reaction, and once the CO methanation starts, the temperature of the catalyst bed can easily heat-up 20~50 ºC, and light-off the CO2 methanation reaction as well. Since there is a lot more CO2 than CO after the shift reaction, once the CO2 methanation starts, it will become a run-away reaction due to the exothermic nature of the methanation reaction.

Catalyst companies have tried to develop a catalyst that has a wider temperature window of selective CO methanation. Major progress has been made in recent years.  However, since the CO amount coming out of the shift reactor can fluctuate a lot during a transient of the power plants, other engineering measures have to be in place to prevent the run-away reaction.

The solution is to washcoat the Selective CO Methanation Catalyst onto a Two Phase-Heat Exchanger to replace both PrOx1 and PrOx2 Reactors For CO clean up in a PEM Fuel Cell Power Plant.  The huge latent heat of vaporization is used to tightly control the methanation catalyst temperature in the range of CO methanation without light...