Enhanced solid oxide fuel cell systems

Abstract

Enhanced high temperature fuel cell systems, such as solid oxide fuel cell systems and molten carbonate fuel cell systems are disclosed. Embodiments of the disclosure include solid oxide and molten carbonate fuel cell systems incorporating gas separation apparati facilitating the recycle of hydrogen fuel from fuel cell anode exhaust for supply to the fuel cell anode inlet. Further embodiments of the disclosure include solid oxide and molten carbonate fuel cell systems incorporating inventive combinations of anode materials conducive to combination with enriched hydrogen fuel. Other embodiments of the disclosure include gas separation apparati for providing enriched oxygen feed to the cathode inlet of solid oxide and molten carbonate fuel cells.

1 . A high temperature fuel cell system comprising an anode channel having an anode inlet and outlet, a cathode channel having a cathode inlet and outlet, a gas separation means operable to produce a first product gas enriched in oxygen from the air, and a catalytic partial oxidation means, wherein 
 the gas separation means is fluidly connected to supply at least a portion of the first oxygen-enriched product gas to the cathode inlet;    the catalytic partial oxidation means is fluidly connected to receive at least a portion of an exhaust gas from the cathode outlet for reaction with a hydrocarbon fuel mixture to produce a second product gas comprising syngas; and    at least a portion of the second product gas is provided as a portion of a fuel gas mixture which is supplied to the anode inlet.    
     
     
         2 . The high temperature fuel cell system of  claim 1 , additionally comprising a second gas separation means operable to enrich a first gas component of an anode exhaust gas exiting the anode outlet to produce a third product gas enriched in the first gas component and wherein at least a portion of the third product gas enriched in the first gas component is provided as a portion of the fuel gas mixture which is supplied to the anode inlet.  
     
     
         3 . The high temperature fuel cell system of  claim 1  wherein the anode and cathode channels are arranged such that flow of the fuel gas mixture in the anode channel is in a direction countercurrent to flow of the oxygen-enriched gas in the cathode channel.  
     
     
         4 . The high temperature fuel cell system of  claim 1  wherein the high temperature fuel cell is a solid oxide fuel cell.  
     
     
         5 . A high temperature fuel cell system comprising an anode channel, an anode inlet, an anode outlet, a first anode channel portion proximal to the anode inlet, a second anode channel portion proximal to the anode outlet, a gas separation means operable to enrich a hydrogen gas component of an anode exhaust gas exiting the anode outlet to produce a first product gas enriched in the hydrogen gas component such that at least a portion of the first product gas enriched in the hydrogen gas component can be provided as a portion of a fuel mixture supplied to the anode inlet, and a pre-reformer for pre-reforming fresh or make-up fuel together with anode exhaust gas recycled from the anode outlet fuel, the pre-reformer being provided between the anode outlet and the gas separation means, wherein: 
 the first anode channel portion comprises an anode material that is resistant to carbon deposition and active for direct oxidation of hydrogen, at least one hydrocarbon fuel or mixtures thereof;    the second anode channel portion comprises an anode material that is catalytically active for steam reforming of at least one hydrocarbon; and    the fuel mixture comprises steam, hydrogen and optionally at least one hydrocarbon fuel, wherein steam and hydrogen are present in proportions of no more than 1.5 moles of steam per mole of hydrogen or the molar ratio of steam to hydrocarbon fuel in the mixture is no greater than 1.5 to 1.    
     
     
         6 . The high temperature fuel cell system according to  claim 5  wherein a water gas shift reactor is provided between the pre-reformer and the gas separation means.  
     
     
         7 . The high temperature fuel cell system according to  claim 6  wherein all anode exhaust gas is admitted to the pre-reformer.  
     
     
         8 . The high temperature fuel cell system according to  claim 5  wherein the pre-reformer is a hydrogasification reformer.  
     
     
         9 . A high temperature fuel cell system comprising an anode channel, an anode inlet, an anode outlet, a pre-reformer for pre-reforming fuel together with anode exhaust gas recycled from the anode outlet, and a gas separation means operable to enrich a hydrogen gas component from gas exiting the pre-reformer to produce a first product gas enriched in the hydrogen gas component such that at least a portion of the first product gas can be provided as a fuel mixture supplied to the anode inlet.  
     
     
         10 . The high temperature fuel cell system according to  claim 9  wherein a water gas shift reactor is provided between the pre-reformer and the gas separation means.  
     
     
         11 . The high temperature fuel cell system according to  claim 9  wherein the pre-reformer is a hydrogasification reformer or hydrogasifier.  
     
     
         12 . The high temperature fuel cell system according to  claim 9  wherein: 
 the anode channel includes a first channel portion proximal to the anode inlet and a second anode channel portion proximal to the anode outlet;    the first anode channel portion comprises an anode material that is resistant to carbon deposition and active for direct oxidation of hydrogen, at least one hydrocarbon fuel or mixtures thereof; and    the second anode channel portion comprises an anode material that is catalytically active for steam reforming of at least one hydrocarbon.    
     
     
         13 . The high temperature fuel cell system according to  claim 12  wherein the fuel mixture contains no more than 1.5 moles of steam per mole of hydrogen or carbon.  
     
     
         14 . A method of operating a fuel cell system, the fuel cell system comprising an anode channel, an anode inlet, an anode outlet, a first anode channel portion proximal to the anode inlet, a second anode channel portion proximal to the anode outlet, a gas separation means, a pre-reforming or hydrogasification means, optionally a water gas shift reactor, and wherein the first anode channel portion comprises an anode material that is resistant to carbon deposition and active for direct oxidation of hydrogen, at least one hydrocarbon fuel or mixtures thereof, and the second anode channel portion comprises an anode material that is catalytically active for steam reforming of at least one hydrocarbon, the method comprising: 
 introducing an anode exhaust gas exiting the anode outlet into the gas separation means to produce a first product gas enriched in the a hydrogen gas component;    introducing the first product gas enriched in the hydrogen gas component as a portion of a fuel mixture supplied to the anode inlet, wherein the fuel mixture comprises steam, hydrogen and optionally at least one hydrocarbon fuel, wherein steam and hydrogen are present in proportions of no more than 1.5 moles of steam per mole of hydrogen or the molar ratio of steam to hydrocarbon fuel in the mixture is no greater than 1.5 to 1;    introducing fresh or make-up fuel to the pre-reformer or hydrogasification means together with the anode exhaust gas;    optionally performing a water gas shift reaction;    performing gas separation to enrich hydrogen in the first product gas, while removing CO 2 , H 2 S and excess steam from the first product gas; and    introducing the first product gas to the anode inlet.    
     
     
         15 . The method of operating a fuel cell system according to  claim 14 , wherein the entire anode exhaust gas is introduced with the fresh or make-up fuel to the pre-reformer or hydrogasification means, and the first product gas is the entire fuel mixture introduced to the anode inlet.  
     
     
         16 . A method of operating a fuel cell system, the fuel cell system comprising an anode channel with an anode inlet and an anode outlet, a gas separation means, and a pre-reforming or hydrogasification means and optionally a water gas shift reactor, the method further comprising the sequential steps of: 
 a) introducing fresh or make-up fuel to the pre-reformer or hydrogasification means together with an anode exhaust gas;    b) optionally performing a water gas shift reaction;    c) performing gas separation to enrich hydrogen in a first product gas, while removing CO 2 , H 2 S and excess steam from the first product gas; and    d) introducing the first product gas to the anode inlet.    
     
     
         17 . The method of operating a fuel cell system according to  claim 16 , wherein: 
 the anode channel includes a first channel portion proximal to the anode inlet and a second anode channel portion proximal to the anode outlet;    the first anode channel portion comprises an anode material that is resistant to carbon deposition and active for direct oxidation of hydrogen, at least one hydrocarbon fuel or mixtures thereof;    the second anode channel portion comprises an anode material that is catalytically active for steam reforming of at least one hydrocarbon; and    the fuel gas mixture contains less than 1.5 moles of steam per mole of hydrogen or carbon, so as to achieve high voltage efficiency while avoiding carbon deposition in the anode channel.