Reformer With Bypass For Internal Fuel Cell Reforming

Abstract

A fuel cell system having a fuel cell stack, comprising an anode portion and a cathode portion, a source of hydrocarbon fuel, and a reformer unit having one or more cold-side, reforming passages, a fuel supply conduit, a reformate exhaust conduit, one or more hot-side channels, a cathode exhaust conduit, a cathode inlet conduit, one or more bypass channels having non-reforming passages for fuel to bypass the cold-side channels, and a flow controller for controlling the flowrate in the bypass channels, and methods for operating the same, is provided.

We claim: 
     
         1 . In a fuel cell system comprising:
 a source of a hydrocarbon fuel;   a reformer for receiving the hydrocarbon fuel and converting the hydrocarbon fuel to reformate; and   a fuel cell stack having an anode inlet for receiving a mixture of the reformate and the hydrocarbon fuel,   a method of controlling the volumetric ratio of the reformate and hydrocarbon fuel in the mixture comprising:   providing a flow path for fuel to bypass the reformer;   controlling the flow rate of fuel within the flow path; and   combining the fuel flowing through the bypass flow path with the reformate.   
     
     
         2 . The method of  claim 1  further comprising:
 removing higher hydrocarbons from the hydrocarbon fuel 
 
     
     
         3 . The method of  claim 1  further comprising:
 heating the fuel bypassing the reformer prior to combining the fuel. 
 
     
     
         4 . The method of  claim 3 , wherein the heating results from a transfer of heat from a cathode exhaust gas. 
     
     
         5 . The method of  claim 1 , wherein at least a portion of the fuel comprises an anode exhaust gas. 
     
     
         6 . In a fuel cell system configured for internal reforming of a hydrocarbon fuel in the fuel cell stack, a method of operation comprising:
 supplying a hydrocarbon fuel to the system;   feeding a portion of the hydrocarbon fuel to a reformer to thereby convert the fuel to reformate;   bypassing a second portion of the hydrocarbon fuel around the reformer;   combining the bypassed hydrocarbon fuel with the reformate at a selected feed rate;   supplying the combined reformate and hydrocarbon fuel to an anode inlet of the fuel cell stack; and   controlling the volumetric ratio of the combined reformate and hydrocarbon fuel supplied to the anode inlet of the fuel cell stack by selecting the feed rate of the bypassed hydrocarbon fuel.   
     
     
         7 . The method of  claim 6  further comprising heating the reformate and the bypassed fuel by transferring heat from a gas supplied from a cathode exhaust of the fuel cell stack. 
     
     
         8 . The method of  claim 7  further comprising coating at least a portion of the surfaces exposed to the bypassed fuel with a ceramic material to thereby inhibit carbon formation on the coated surfaces. 
     
     
         9 . A fuel cell system comprising:
 a fuel cell stack configured for internal reforming of a hydrocarbon fuel, said fuel cell stack comprising:
 an anode portion in fluid communication with an anode inlet and an anode exhaust; 
 a cathode portion in fluid communication with a cathode inlet and a cathode exhaust; 
   a source of hydrocarbon fuel;   a reformer unit for converting hydrocarbon fuel to reformate, said reformer unit comprising:
 one or more cold-side channels for providing a reforming passage for fuel through said reformer unit; 
 a fuel supply conduit in fluid communication with said fuel source and said cold-side channels; 
 a reformate exhaust conduit in fluid communication with said cold-side channels and said anode inlet; 
 one or more hot-side channels for providing a passage for a cathode exhaust gas through said reforming unit, said hot-side channels being in sufficient proximity to said cold-side channels to effect heat transfer between the fluids flowing through the respective channels; 
 a cathode exhaust conduit in fluid communication with said cathode exhaust and said hot-side channels; 
 a cathode inlet conduit in fluid communication with said hot-side channels and said cathode inlet; 
 one or more bypass channels for providing a non-reforming passage for fuel through said reformer unit, said bypass channels being in fluid communication with said fuel supply conduit and said reformate exhaust conduit to thereby combine the non-reformed fuel with the reformate; and 
 a flow controller for controlling the flow rate of fuel flowing through said bypass channels. 
   
     
     
         10 . The system of  claim 9 , wherein said bypass channels is in sufficient proximity to said hot-side channels to effect heat transfer between the fluids flowing through the respective channel. 
     
     
         11 . The system of  claim 9 , wherein said bypass channels is in sufficient proximity to said cathode inlet conduit to effect heat transfer between the fluids flowing through the respective channel. 
     
     
         12 . The system of  claim 11 , wherein said bypass channel is a line which passes through said cathode inlet conduit, wherein said amount of heat transferred from the fluid in the cathode inlet conduit to the non-reformed fuel in the bypass channel is determined at least in part by the length of the bypass channel line disposed in the cathode inlet conduit. 
     
     
         13 . The system of  claim 9 , wherein said bypass channel is lined with a ceramic coating to inhibit carbon formation. 
     
     
         14 . The system of  claim 9 , further comprising a higher hydrocarbon reduction unit. 
     
     
         15 . The system of  claim 9 , further comprising a combustor. 
     
     
         16 . The system of  claim 9 , wherein the reformer unit is a steam reformer. 
     
     
         17 . The system of  claim 16 , wherein said reformer unit comprises a catalyst containing at least one Group VIII metal. 
     
     
         18 . The system of  claim 17 , wherein the at least one Group VIII metal comprises 0.1 to 40 wt % of said catalyst. 
     
     
         19 . The system of  claim 17 , wherein said catalyst further comprises one or more promoter elements selected from a group containing elements from Groups IIa-VIIa, elements Groups Ib-Vb, lanthanide series, and actinide series. 
     
     
         20 . The system of  claim 17 , wherein said promoter element comprises 0.01 to 10 wt % of the catalyst.