Fuel Cell System

Abstract

A fuel cell system is disclosed in which the oxidative degradation of an anode of a fuel cell during an operation stop period is restrained. The fuel cell system ( 39 ) of the invention comprises a fuel cell ( 1 ) configured to generate electric power by use of hydrogen contained in a fuel gas supplied to an anode ( 1 a ) and oxygen contained in an oxidizing gas supplied to a cathode ( 1 c ); and a combustor ( 4 ) configured to combust flammable gas, and is formed such that after stopping the power generation, the flammable gas is introduced into and kept in the cathode ( 1 c ) and when discharging the flammable gas from the cathode ( 1 c ), the flammable gas is combusted by the combustor ( 4 )

1 . A fuel cell system comprising: 
 a fuel cell configured to generate electric power by use of hydrogen contained in a fuel gas supplied to an anode and oxygen contained in an oxidizing gas supplied to a cathode; and    a combustor configured to combust flammable gas,    wherein after stopping the power generation, a flammable gas is introduced into and kept in the cathode and when discharging the flammable gas from the cathode, the flammable gas is combusted by said combustor.    
     
     
         2 . The fuel cell system according to  claim 1 , comprising: 
 combustion gas feeding device configured to supply a combustion gas to said combustor; and    a combustion air feeder configured to supply a combustion air to said combustor;    wherein said combustion air feeder supplies the combustion air in such an amount that an air-fuel ratio within said combustor becomes 1 or more, with respect to flammable gas comprised of at least one of the flammable gas supplied to said combustor and the combustion gas.    
     
     
         3 . The fuel cell system according to  claim 2 , 
 wherein the gas discharged from the cathode of said fuel cell is supplied to a passage through which the combustion gas is supplied to said combustor.    
     
     
         4 . The fuel cell system according to  claim 2 , 
 wherein the gas discharged from the cathode of said fuel cell is supplied to a passage through which the combustion air is supplied to said combustor.    
     
     
         5 . The fuel cell system according to  claim 3 , 
 wherein, at least during the period of an operation in which the oxidizing gas in the cathode of said fuel cell is replaced with the flammable gas or the flammable gas in the cathode is replaced with the oxidizing gas, the amount of gas supplied to the cathode or the supply amount of the combustion gas is controlled such that the ratio of the flow rate of flammable gas contained in the combustion gas to the sum of the flow rate of oxygen contained in the gas discharged from the cathode and the flow rate of flammable gas is below the lower combustible limit of flammable gas or exceeds the upper combustible limit of flammable gas based on a mixture of flammable gas and oxygen.    
     
     
         6 . The fuel cell system according to  claim 3 , 
 wherein, in cases where air is used as the oxidizing gas, at least during the period of an operation in which air in the cathode of said fuel cell is replaced with the flammable gas or the flammable gas in the cathode is replaced with air, the amount of gas supplied to the cathode or the supply amount of the combustion gas is controlled such that the ratio of the flow rate of flammable gas contained in the combustion gas to the sum of the flow rate of air discharged from the cathode and the flow rate of flammable gas is below the lower combustible limit of flammable gas or exceeds the upper combustible limit of flammable gas based on a mixture of the flammable gas and air.    
     
     
         7 . The fuel cell system according to  claim 5 , wherein the flammable gas is hydrogen gas.  
     
     
         8 . The fuel cell system according to  claim 3 , 
 wherein, at least during the period of an operation in which the oxidizing gas in the cathode of said fuel cell is replaced with the flammable gas or the flammable gas in the cathode is replaced with the oxidizing gas, the amount of gas supplied to the cathode or the supply amount of the combustion gas is controlled such that the ratio of the flow rate of the combustion gas to the sum of the flow rate of oxygen contained in the gas discharged from the cathode and the flow rate of the combustion gas is below the lower combustible limit of the combustion gas or exceeds the upper combustible limit of the combustion gas based on a mixture of the combustion gas and oxygen.    
     
     
         9 . The fuel cell system according to  claim 3 , 
 wherein, in cases where air is used as the oxidizing gas, at least during the period of an operation in which air in the cathode of said fuel cell is replaced with the flammable gas or the flammable gas in the cathode is replaced with air, the amount of gas supplied to the cathode or the supply amount of the combustion gas is controlled such that the ratio of the flow rate of the combustion gas to the sum of the flow rate of air discharged from the cathode and the flow rate of the combustion gas is below the lower combustible limit of the combustion gas or exceeds the upper combustible limit of the combustion gas based on a mixture of the combustion gas and air.    
     
     
         10 . The fuel cell system according to  claim 4 , 
 wherein, at least during the period of an operation in which the oxidizing gas in the cathode of said fuel cell is replaced with the flammable gas or the flammable gas in the cathode is replaced with the oxidizing gas, the amount of gas supplied to the cathode or the supply amount of the combustion air is controlled such that the ratio of the flow rate of the flammable gas discharged from the cathode to the sum of the flow rate of the flammable gas and the flow rate of the combustion air is below the lower combustible limit of flammable gas or exceeds the upper combustible limit of the flammable gas based on a mixture of flammable gas and air.    
     
     
         11 . The fuel cell system according to  claim 4 , 
 wherein, at least during the period of an operation in which the oxidizing gas in the cathode of said fuel cell is replaced with the flammable gas or the flammable gas in the cathode is replaced with the oxidizing gas, the amount of gas supplied to the cathode or the supply amount of the combustion air is controlled such that the ratio of the flow rate of the gas discharged from the cathode to the sum of the flow rate of the gas and the flow rate of the combustion air is below the lower combustible limit of the gas discharged from the cathode or exceeds the upper combustible limit of the gas based on a mixture of the gas and air.    
     
     
         12 . The fuel cell system according to  claim 5 , 
 wherein at a start of the power generation, the oxidizing gas is supplied to the cathode, thereby discharging the flammable gas.    
     
     
         13 . The fuel cell system according to  claim 5 , comprising: 
 a fuel processor having a reformer for generating the fuel gas containing hydrogen from a power generation material,    wherein said combustor is a fuel processing burner for heating said reformer.    
     
     
         14 . The fuel cell system according to  claim 5 , comprising: 
 a hydrogen feeder capable of supplying hydrogen gas as the fuel gas for said fuel cell.    
     
     
         15 . The fuel cell system according to  claim 13 , wherein the combustion gas is the fuel gas discharged from said fuel processor or remaining fuel gas discharged from said fuel cell.  
     
     
         16 . The fuel cell system according to  claim 14 , wherein the combustion gas is the hydrogen gas discharged from said hydrogen feeder or remaining hydrogen gas discharged from said fuel cell.  
     
     
         17 . The fuel cell system according to  claim 15 , wherein during the period of the operation in which the oxidizing gas in the cathode of said fuel cell is replaced with the flammable gas or the flammable gas in the cathode is replaced with the oxidizing gas, said combustion air feeder supplies air in such an amount that an air-fuel ratio within said combustor as the fuel processing burner becomes 1 or more, with respect to flammable gas and the combustion gas.  
     
     
         18 . The fuel cell system according to  claim 15 , wherein before the operation in which the oxidizing gas in the cathode of said fuel cell is replaced with the flammable gas or the flammable gas in the cathode is replaced with the oxidizing gas, the temperature of said reformer is controlled so as to be lower than a specified target temperature for normal operation.  
     
     
         19 . The fuel cell system according to  claim 10 , 
 wherein at a start of the power generation, the oxidizing gas is supplied to the cathode, thereby discharging the flammable gas.    
     
     
         20 . The fuel cell system according to  claim 10 , comprising: 
 a fuel processor having a reformer for generating the fuel gas containing hydrogen from a power generation material,    wherein said combustor is a fuel processing burner for heating said reformer.    
     
     
         21 . The fuel cell system according to  claim 10 , comprising: 
 a hydrogen feeder capable of supplying hydrogen gas as the fuel gas for said fuel cell.    
     
     
         22 . The fuel cell system according to  claim 16 , wherein during the period of the operation in which the oxidizing gas in the cathode of said fuel cell is replaced with the flammable gas or the flammable gas in the cathode is replaced with the oxidizing gas, said combustion air feeder supplies air in such an amount that an air-fuel ratio within said combustor as a fuel processing burner becomes 1 or more, with respect to flammable gas and the combustion gas.