Integrated high temperature PEM fuel cell system

Abstract

A simplified PEM fuel cell system is integrated with a fuel processor and an exhaust gas oxidizer to ensure clean emissions. The fuel cell can have an operating temperature of 120-200° C. Cathode exhaust of a PEM fuel cell is used to provide steam and oxygen to a fuel processing reactor to convert a hydrocarbon fuel to hydrogen, wherein the hydrogen is provided to a fuel cell.

What is claimed is:  
     
         1 . A fuel cell system, comprising: 
 a PEM fuel cell having an operating temperature of at least 120° C., the fuel cell having a cathode inlet and a cathode outlet;    a cathode blower having an electrical connection to a controller, the cathode blower being adapted to vary a flow of air through the fuel cell from the cathode inlet to the cathode outlet according to a first control signal from the controller;    a fuel processing reactor having an inlet and an outlet, the inlet and outlet being in fluid communication with a catalyst suitable for converting a hydrocarbon into a gas containing hydrogen and carbon monoxide, the outlet being in fluid communication with an anode chamber of the fuel cell;    a fuel blower having an electrical connection to the controller, the fuel blower being adapted to vary a flow of fuel through the reactor according to a second control signal form the controller; and    wherein the cathode outlet is in fluid communication with the fuel processor reactor inlet.    
     
     
         2 . The fuel cell system of  claim 1 , wherein the fuel cell operating temperature is in the range 120-200° C.  
     
     
         3 . The fuel cell system of  claim 1 , wherein the fuel cell operating temperature is in the range 160-180° C.  
     
     
         4 . The fuel cell system of  claim 1 , wherein the fuel cell comprises a polybenzimidazole PEM.  
     
     
         5 . The fuel cell system of  claim 1 , wherein the cathode blower is adapted to flow ambient air directly through the fuel cell.  
     
     
         6 . The fuel cell system of  claim 1 , wherein the controller is adapted to modulate the first control signal to maintain a molar ratio of oxygen to methane in the reactor inlet, the ratio being in the range 0.4-0.7.  
     
     
         7 . The fuel cell system of  claim 1 , wherein the controller is adapted to modulate the second control signal to prevent hydrogen starvation in the fuel cell.  
     
     
         8 . The fuel cell system of  claim 7 , wherein the controller is adapted to measure a voltage of the fuel cell stack and modulate the second control signal in response to the voltage measurement.  
     
     
         9 . The fuel cell system of  claim 1 , further comprising a mixing vessel having a first inlet adapted to receive an air flow from the cathode outlet, a second inlet adapted to receive a fuel flow from the fuel blower, and an outlet adapted to flow a mixture of the air flow and fuel flow into the fuel processing reactor.  
     
     
         10 . The fuel cell system of  claim 8 , wherein the mixing vessel further comprises a third inlet adapted to receive a flow of ambient air.  
     
     
         11 . The fuel cell system of  claim 8 , wherein the mixing vessel further comprises a fourth inlet adapted to receive a flow of steam.  
     
     
         12 . The fuel cell system of  claim 1 , wherein the carbon monoxide flowed from the fuel processing reactor to the fuel cell has a concentration of at least 1000 parts per million.  
     
     
         13 . The fuel cell system of  claim 1 , wherein cathode exhaust is flowed from the cathode outlet to the reactor inlet, and wherein the cathode exhaust is maintained at a temperature over 100° C.  
     
     
         14 . The fuel cell system of  claim 1 , wherein the cathode outlet is connected to a conduit that is connected to the reactor inlet, and wherein the conduit comprises a by-pass vent.  
     
     
         15 . A method of operating a fuel cell system, comprising: 
 operating a first blower according to a first control signal to vary a flow of air through a cathode chamber of a PEM fuel cell;    reacting a portion of the air in the fuel cell to produce electricity;    exhausting a remaining portion of the air from the fuel cell, wherein the remaining portion of air contains water vapor;    mixing a portion of the exhausted air with a hydrocarbon gas to form a feed mixture;    modulating the first control signal to maintain a predetermined amount of oxygen in the feed mixture;    operating a second blower according to a second control signal to flow the feed mixture into a reactor where the feed mixture is contacted with a catalyst suitable for converting a portion of the hydrocarbon gas into a fuel gas containing hydrogen and carbon monoxide;    flowing the fuel gas into an anode chamber of the fuel cell; and    modulating the second control signal to maintain a predetermined amount of hydrogen in the fuel cell.    
     
     
         16 . The method of  claim 15 , further comprising: 
 maintaining an operating temperature of the fuel cell in the range 120-200° C.    
     
     
         17 . The method of  claim 15 , further comprising: 
 maintaining an operating temperature of the fuel cell in the range 160-180° C.    
     
     
         18 . The method of  claim 16 , wherein the fuel cell comprises a polybenzimidazole PEM.  
     
     
         19 . The method of  claim 15 , wherein the first blower is adapted to flow ambient air directly through the fuel cell.  
     
     
         20 . The method of  claim 15 , wherein the hydrocarbon gas comprises methane, and further comprising: 
 modulating the first control signal to maintain a molar ratio of oxygen to methane in the reactor inlet, the ratio being in the range 0.4-0.7.    
     
     
         21 . The method of  claim 20 , further comprising: 
 flowing ambient air into the reactor.    
     
     
         22 . The method of  claim 20 , further comprising: 
 flowing steam into the reactor to maintain a molar ratio of water to methane in an atmosphere of the reactor, the ratio being in the range 2.0-5.0.    
     
     
         23 . The method of  claim 15 , further comprising: 
 modulating the second control signal to prevent hydrogen starvation in the fuel cell.    
     
     
         24 . The method of  claim 15 , further comprising: 
 measuring a voltage of the fuel cell stack; and    modulating the second control signal in response to the voltage measurement.    
     
     
         25 . The method of  claim 15 , wherein the carbon monoxide in the fuel gas flowed into the anode chamber of the fuel cell has a concentration of at least 1,000 parts per million.  
     
     
         26 . The method of  claim 15 , wherein the carbon monoxide in the fuel gas flowed into the anode chamber of the fuel cell has a concentration in the range of 3,000-10,000 parts per million.  
     
     
         27 . A method of operating a fuel cell system, comprising: 
 operating a first blower according to a first control signal to vary a flow of ambient air through a cathode chamber of a PEM fuel cell;    reacting a portion of the air in the fuel cell to produce electricity;    exhausting a remaining portion of the air from the fuel cell, wherein the remaining portion of air contains water vapor;    mixing a portion of the exhausted air with methane to form a feed mixture;    modulating the first control signal to maintain a molar ratio of oxygen to methane in the feed mixture, the ratio being in the range 0.4-0.7;    operating a second blower according to a second control signal to flow the hydrocarbon gas into a reactor where the feed mixture is contacted with a catalyst suitable for converting a portion of the hydrocarbon gas into a fuel gas containing hydrogen and carbon monoxide;    flowing the fuel gas into an anode chamber of the fuel cell; and    modulating the second control signal to prevent hydrogen starvation in the fuel cell.    
     
     
         28 . The method of  claim 27 , wherein the fuel cell comprises a polybenzimidazole PEM, further comprising: 
 maintaining an operating temperature of the fuel cell in the range 120-200° C.    
     
     
         29 . The method of  claim 27 , wherein the hydrocarbon gas comprises methane, and further comprising: 
 modulating the first control signal to maintain a molar ratio of oxygen to methane in the reactor inlet, the ratio being in the range 0.4-0.7.    maintaining a molar ratio of water to methane in the feed mixture, the ratio being in the range 2.0-5.0.    
     
     
         30 . The method of  claim 27 , further comprising: 
 measuring a voltage of the fuel cell stack; and    modulating the second control signal in response to the voltage measurement.    
     
     
         31 . The method of  claim 27 , wherein the carbon monoxide in the fuel gas flowed into the anode chamber of the fuel cell has a concentration in the range of 3,000-10,000 parts per million.