Process and apparatus for removing carbon monoxide from a gas stream

Abstract

Apparatus and process for removing carbon monoxide from a gas stream comprising a major portion of an inert gas and a minor portion of carbon monoxide are provided. The process involves contacting a feed gas stream with at least a primary metal oxide in a reaction zone of a reactor vessel at conditions effective to convert substantially all of the carbon monoxide to carbon dioxide, thus producing a purified gas stream consisting essentially of the inert gas and carbon dioxide and substantially free of carbon monoxide. This process has (inter alia) a particular application as a tertiary purification process for producing a more highly purified source of gaseous nitrogen from a source of nitrogen originally produced from a conventional membrane air separation system, wherein the oxygen concentration in the nitrogen stream my vary around a setpoint value, and then further (or secondarily) purified by converting excess oxygen in the nitrogen to carbon monoxide and carbon dioxide using a fuel gas/combustion process, wherein the carbon monoxide concentration varies due to varying oxygen concentration in the feed stream to the combustion process.

What is claimed is:  
     
         1 . A process for removing carbon monoxide from a feed gas stream comprising a major portion of an inert gas and a minor portion of carbon monoxide, said process comprising contacting said feed gas stream with a metal oxide in a reaction zone of a reactor vessel at conditions effective to convert substantially all of said carbon monoxide to carbon dioxide and produce a purified gas stream comprising said inert gas and carbon dioxide and substantially no carbon monoxide.  
     
     
         2 . The process according to  claim 1 , wherein said feed gas stream comprises not less than about 50 ppm carbon monoxide.  
     
     
         3 . The process according to  claim 2 , wherein said feed gas stream comprises from about 50 to 30,000 ppm carbon monoxide.  
     
     
         4 . The process according to  claim 1 , wherein said feed gas stream comprises carbon monoxide varying in concentration.  
     
     
         5 . The process according to  claim 1 , wherein said purified gas stream comprises less than about 1.0 ppm carbon monoxide.  
     
     
         6 . The process according to  claim 1 , wherein substantially all of said metal oxide is reduced during contacting with said feed gas stream to form a reduced metal, and wherein said reduced metal is regenerated by contacting said reduced metal with an oxygen-containing regeneration gas stream at conditions effective to oxidize substantially all of said reduced metal to form said metal oxide.  
     
     
         7 . The process according to  claim 1 , wherein said feed gas stream is split to form a plurality of feed gas streams, each of said feed gas streams passing through a corresponding plurality of reaction zones of a corresponding plurality of reactor vessels.  
     
     
         8 . The process according to  claim 1 , wherein at least one reactor bed comprises said metal oxide and is contacted with said feed gas stream to convert said carbon monoxide to said carbon dioxide, and at least one other reactor bed comprises said reduced metal and is contacted with an oxygen-containing regeneration gas stream to regenerate substantially all of said reduced metal to form oxidized metal.  
     
     
         9 . The process according to  claim 1 , wherein said inert gas is nitrogen.  
     
     
         10 . The process according to  claim 6 , wherein said oxygen-containing regeneration gas stream is passed through said reaction zone along with said feed gas stream to regenerate said reduced metal in situ.  
     
     
         11 . The process according to  claim 1 , wherein said reaction zone is operated at a temperature ranging from ambient to about 350° C.  
     
     
         12 . The process according to  claim 11 , wherein said reaction zone is operated at a temperature of about 100 to about 300° C.  
     
     
         13 . The process according to  claim 1 , wherein said metal oxide comprises a major portion of a primary metal oxide selected from the group consisting of palladium oxides, platinum oxides, nickel oxides, and mixtures thereof, and a minor portion of a promoter metal oxide selected from the group consisting of copper oxides, silver oxides, cadmium oxides or any suitable mixture thereof.  
     
     
         14 . The process according to  claim 13 , wherein said primary metal oxide is a palladium oxide.  
     
     
         15 . The process according to  claim 14 , wherein said palladium oxide is supported on alumina or on another suitable inert support material.  
     
     
         16 . The process according to  claim 15 , wherein said palladium (in a reduced condition) comprises between about 0.01 and 10.0 percent by weight of a total weight of said palladium plus alumina or other inert support material.  
     
     
         17 . The process according to  claim 16 , wherein said palladium (reduced) comprises about 0.1 to about 1.0 percent by weight of the total weight of said palladium plus alumina or other inert support material.  
     
     
         18 . The process according to  claim 1  wherein said inert gas is selected from the group consisting of nitrogen, helium, neon, argon, xenon, krypton, and mixtures thereof  
     
     
         19 . A process for removing carbon monoxide from a feed gas stream comprising a major portion of nitrogen and a minor portion of carbon monoxide, said process comprising the steps of: 
 (a) contacting said feed gas stream with a metal oxide by passing the feed gas stream through a reaction zone of a reactor vessel at conditions effective to react said carbon monoxide with said metal oxide to convert substantially all of said carbon monoxide to carbon dioxide and produce a reduced metal and a purified gas stream, the purified gas stream comprising nitrogen and carbon dioxide but substantially devoid of carbon monoxide, with said conditions including a temperature ranging from ambient to about 350° C.; and    (b) regenerating said reduced metal by contacting said reduced metal with an oxygen-containing regeneration gas stream at conditions effective to oxidize said reduced metal to form said oxidized metal.    
     
     
         20 . The process in accordance with  claim 19  wherein the carbon monoxide concentration in said feed gas stream varies from about 30 to about 50,000 ppm.  
     
     
         21 . An apparatus for removing carbon monoxide from a gas stream comprising a major amount of an inert gas and a minor amount of carbon monoxide, the apparatus comprising a reactor vessel, a reactor vessel gas inlet and a reactor vessel gas outlet, the reactor vessel having an internal reaction zone space at least partially filled with a metal oxide, the metal oxide present in sufficient volume for contacting the gas stream with the metal oxide at conditions effective to convert substantially all of the carbon monoxide to carbon dioxide and thus produce a purified gas stream substantially free of carbon monoxide.  
     
     
         22 . Apparatus in accordance with  claim 21  wherein the reactor vessel includes an oxidizing gas inlet and an oxidizing gas outlet, allowing the reduced metal which was formerly oxidized to be regenerated and form anew the metal oxide.  
     
     
         23 . Apparatus in accordance with  claim 21  which further includes a plurality of reactor vessels have a corresponding plurality of reaction zones, the reactor vessels arranged in parallel flow relationship with respect to the feed gas stream from which carbon monoxide is to be removed.  
     
     
         24 . Apparatus in accordance with  claim 23  wherein at least one of said plurality of reactor vessels is adapted to function in a carbon monoxide removal mode, while one or more reactor vessels are adapted to operate simultaneously in a regeneration mode.  
     
     
         25 . Apparatus in accordance with  claim 23  wherein all of said plurality of reactor vessels are adapted to function simultaneously in a carbon monoxide removal mode, and then simultaneously in a regeneration mode.  
     
     
         26 . The apparatus according to  claim 21  wherein said metal oxide comprises a major portion of a primary metal oxide selected from the group consisting of palladium oxides, platinum oxides, nickel oxides, and mixtures thereof, and a minor portion of a promoter metal oxide selected from the group consisting of copper oxides, silver oxides, cadmium oxides or any suitable mixture thereof.