Device for staged carbon monoxide oxidation

In a method of operating a H.sub.2 -O.sub.2 fuel cell system comprising the principal steps (1) providing a hydrogen-rich fuel gas having a carbon-monoxide content sufficient to poison the fuel cell's catalyst, (2) subjecting said fuel gas to a CO+H.sub.2 O shift reaction to produce a feed stream consisting essentially of hydrogen, carbon dioxide, water and less than about one percent by volume carbon monoxide, and (3) introducing said feed stream into said fuel cell, the improvement comprising after said shift reaction and before introducing said feed stream into said fuel cell:

• adjusting the temperature of said feed stream to a first temperature selected to promote adsorption of said carbon monoxide onto a first catalyst selected to preferentially adsorb carbon monoxide rather than hydrogen from said feed stream at said first temperature;
• introducing a first quantity of oxygen into said feed stream, said quantity being in stoichiometric excess to said carbon-monoxide and selected to promote preferential oxidation of said carbon monoxide on said first catalyst in the presence of said H.sub.2 ;
• absorbing the carbon monoxide in the feed stream onto said first catalyst and thereon preferential oxidizing it with said first quantity of oxygen at said first temperature in a first oxidation stage to form a process stream consisting essentially of hydrogen, carbon dioxide, water and carbon monoxide wherein the carbon monoxide content is at least about one order of magnitude less than the carbon-monoxide content of said feed stream;
• removing the process stream from said first catalyst;
• introducing a second quantity of oxygen into said process stream, said second quantity being less than said first quantity, in stoichiometric excess to the carbon monoxide in the process stream, and selected to promote preferential oxidation of said carbon monoxide on a second catalyst selected to promote more rapid oxidation of carbon monoxide than hydrogen at a second temperature which is higher than said first temperature and selected to promote said rapid oxidation;
• adjusting the temperature of the process stream to said second temperature;
• and
• reacting the carbon monoxide in the process stream with said second quantity of oxygen on said second catalyst at said second temperature in a second reaction stage to form a product stream for introduction into said fuel cell consisting essentially of hydrogen, carbon dioxide, water and carbon monoxide wherein the carbon monoxide content is less than about 0.01% by volume.