Fuel cell system and operating method

Abstract

A fuel cell system comprises a fuel cell main body containing a fuel cell having an anode side at which fuel is reacted, exhaust products arising at the anode side of the fuel cell as a result of the reaction at the anode side. A recirculation passage is located inside the fuel cell main body and recirculates a proportion of the exhaust products directly to the anode side of the fuel cell for reaction at the anode side. The recirculation passage may include an ejector arrangement for mixing fresh fuel with the recirculated exhaust products and may also include a reforming catalyst for partially reforming the mixture in the recirculation passage.

1 - 15 . (canceled) 
     
     
         16 . An operating method for a fuel cell system comprising a tubular fuel cell, the tubular fuel cell having a cathode side, an anode side and a recirculation passage inside the tubular fuel cell, the operating method comprising the steps of:
 (i) reacting fuel at the anode side of the fuel cell, exhaust products arising at the anode side of the fuel cell, during operation of the fuel cell system, as a result of the reaction at the anode side; and   (ii) recirculating a proportion of the exhaust products through the recirculation passage directly to the anode side of the fuel cell for reaction at the anode side.   
     
     
         17 . The operating method according to  claim 16 , wherein step (ii) includes supplying fresh fuel into the recirculation passage to provide a mixture of recirculated exhaust products and fresh fuel for recirculation directly to the anode side of the fuel cell. 
     
     
         18 . The operating method according to  claim 17 , further comprising partially reforming the mixture of recirculated exhaust products and fresh fuel inside the recirculation passage. 
     
     
         19 . The operating method according to  claim 17 , further comprising reforming the mixture of recirculated exhaust products and fresh fuel at the anode side of the fuel cell. 
     
     
         20 . The operating method according to  claim 16 , wherein the exhaust products arising at the anode side of the fuel cell during step (i) additionally contain unreacted fuel. 
     
     
         21 . The operating method according to  claim 16 , wherein the method comprises continuously repeating steps (i) and (ii) to provide an operating cycle for the fuel cell system. 
     
     
         22 . The operating method according to  claim 16 , wherein the recirculation passage comprises a recirculation tube having inlet and outlet ends located inside the tubular fuel cell. 
     
     
         23 . The operating method according to  claim 16 , wherein the recirculation passage includes a reforming catalyst. 
     
     
         24 . The operating method according to  claim 16 , wherein the recirculation passage includes an ejector arrangement for mixing fresh fuel with the recirculated exhaust products. 
     
     
         25 . The operating method according to  claim 16 , wherein the recirculation passage is located proximate the anode side of the fuel cell. 
     
     
         26 . The operating method according to  claim 16 , wherein the recirculation passage comprises a recirculation tube within the tubular fuel cell that extends between open and closed ends of the tubular fuel cell. 
     
     
         27 . The operating method according to  claim 26 , wherein the outlet end of the recirculation tube is located generally at or adjacent to the closed end of the tubular fuel cell. 
     
     
         28 . The operating method according to  claim 27 , wherein the inlet end of the recirculation tube is located generally at or adjacent to the open end of the tubular fuel cell such that the recirculation tube extends substantially along the entire length of the tubular fuel cell between the open and closed ends. 
     
     
         29 . The operating method according to  claim 26 , wherein the inlet end of the recirculation tube is spaced from the open end of the tubular fuel cell such that the recirculation tube extends only part way along the length of the tubular fuel cell. 
     
     
         30 . The operating method according to  claim 16 , wherein the tubular fuel cell is a single fuel cell. 
     
     
         31 . The operating method according to  claim 16 , wherein the tubular fuel cell is a fuel cell of a fuel cell stack comprising a plurality of fuel cells. 
     
     
         32 . The operating method according to  claim 26 , wherein an entirety of the recirculation passage is defined by a recirculation tube, the recirculation tube being entirely within the tubular fuel cell. 
     
     
         33 . The operating method according to  claim 32 , comprising:
 feeding fuel to the tubular fuel cell via at least one a fuel injector positioned adjacent to the recirculation passage to feed fuel into the recirculation passage.   
     
     
         34 . The operating method according to  claim 26 , wherein the recirculation passage has a reforming catalyst positioned on an inner surface of the recirculation tube, the method comprising:
 reforming fuel from a fuel injector in the recirculation passage prior to the fuel being ejected from the outlet end of the recirculation passage to react at the anode side of the fuel cell.   
     
     
         35 . The operating method according to  claim 34 , wherein the anode side has an anode surface, the cathode side is an external cathode surface of the tubular fuel cell that is opposite the anode surface, and an electrolyte is positioned between the anode surface and the external cathode surface, the method comprising:
 reacting the reformed fuel at the anode surface; and   recirculating the proportion of the exhaust products back into the recirculation passage via the inlet end of the recirculation passage by an ejector positioned adjacent to the open end of the tubular fuel cell; and   mixing the proportion of the exhaust products with fuel fed to the recirculation passage via the fuel injector, the mixing occurring within the recirculation passage.