Carbon monoxide clean-up in a pem fuel cell system

Abstract

A fuel processor system contains an autothermal reactor (ATR) that produces a hydrogen-rich first gas stream containing carbon monoxide. Downstream of the ATR, a pressure swing adsorber produces a second hydrogen-rich gas stream containing 5 ppm carbon monoxide or more. Downstream of the PSA, there is a methanation reactor sized to reduce the CO level of the second stream below 5 ppm. A method of operating of proton exchange membrane fuel cell stack involves cooling the methanator output and feeding it into the stack as an anode fuel.

1 - 18 . (canceled) 
     
     
         19 . A method for reducing the carbon monoxide concentration of a hydrogen-containing gas stream comprising:
 generating a first hydrogen-rich gas stream containing a first carbon monoxide level;   generating a second hydrogen-rich gas stream by passing the first stream through an adsorbent apparatus comprising a material that adsorbs carbon monoxide, wherein the second stream has a lower carbon monoxide level than the first stream; and   passing the second stream through a methanation reactor to produce a third stream with lower carbon monoxide content than the second stream.   
     
     
         20 . A method according to  claim 19 , wherein the carbon monoxide content of the third stream is less than 5 ppm. 
     
     
         21 . A method according to  claim 19 , wherein the carbon monoxide content of the third stream is less than 1 ppm. 
     
     
         22 . A method according to  claim 19 , wherein the carbon monoxide content of the third stream meets requirements of a fuel cell stack. 
     
     
         23 . A method according to  claim 19 , wherein the carbon monoxide content of the first stream is greater than 400 ppm and the carbon monoxide content of the second stream is less than 400 ppm. 
     
     
         24 . A method according to  claim 23 , wherein the carbon monoxide content of the second stream is less than 100 ppm. 
     
     
         25 . A method according to  claim 19 , wherein generating the first stream is accomplished in an autothermal reactor. 
     
     
         26 . A method according to  claim 19 , wherein the adsorbent apparatus comprises a pressure swing adsorber. 
     
     
         27 . A method according to  claim 26 , wherein the pressure swing adsorber comprises multiple fixed adsorbent-containing beds. 
     
     
         28 . A method according to  claim 19 , wherein the adsorbent apparatus removes carbon dioxide form the first gas stream 
     
     
         29 . A method of operating a fuel cell, the fuel cell comprising an anode, a cathode, and a proton exchange membrane, the method comprising supplying the anode with a hydrogen-containing gas stream generated according to the method of  claim 19 . 
     
     
         30 . A method according to  claim 29 , wherein the hydrogen-containing gas stream has less than 5 ppm carbon monoxide. 
     
     
         31 . A method according to  claim 29 , wherein the hydrogen-containing gas stream has less than 1 ppm carbon monoxide. 
     
     
         32 . A method of operating a fuel cell stack comprising an anode, cathode and a proton exchange membrane, the method comprising:
 reacting a hydrocarbon fuel in an autothermal reactor to produce a hydrogen-rich first stream containing carbon monoxide;   passing the first stream through a pressure swing adsorber to produce a second stream lower in carbon monoxide than the first stream;   passing the second stream through a methanation reactor to produce a third stream lower in carbon monoxide than the second stream; and   supplying the anode of the fuel cell stack with the hydrogen-containing third stream.   
     
     
         33 . A method according to  claim 32 , wherein the hydrogen-containing third stream has 5 ppm carbon monoxide or less. 
     
     
         34 . A method according to  claim 32 , wherein the hydrogen-containing third stream has a carbon monoxide level of 1 ppm or less. 
     
     
         35 . A method according to  claim 32 , wherein the second stream is free of carbon dioxide.