Method for adding sulfur to a fuel cell stack system for improved fuel cell stability

Abstract

A method is provided for adding sulfur to a solid oxide fuel cell (SOFC) stack having a Ni—YSZ anode to prolong the life of the SOFC stack. The method includes the steps of providing a reformate stream essentially free of sulfur compounds, feeding the reformate stream to the SOFC stack, and adding a predetermined amount of a sulfur compound into the reformate stream upstream of the SOFC stack. The predetermined amount of the sulfur compound is effective to prolong the life of the Ni—YSZ anode by retarding the formation of carbon onto the Ni—YSZ anode and the coarsening of the granular microstructure of the Ni—YSZ anode, while minimizing the degradation of power output of the SOFC stack within a predetermined limit.

Having described the invention, it is claimed: 
     
         1 . A method for adding sulfur to a solid oxide fuel cell (SOFC) stack having a Ni—YSZ anode, comprising:
 providing a reformate stream essentially free of sulfur compounds; 
 feeding said reformate stream to said SOFC stack; and 
 adding a predetermined amount of a sulfur compound into said reformate stream upstream of said SOFC stack, 
 wherein said predetermined amount of said sulfur compound is effective to prolong the life of said Ni—YSZ anode, while minimizing the degradation of power output of the SOFC stack within a predetermined limit. 
 
     
     
         2 . The method of  claim 1 , wherein said predetermined amount of said sulfur compound is effective to retard either the formation of carbon onto the Ni—YSZ anode or the coarsening of the granular microstructure of the Ni—YSZ anode. 
     
     
         3 . The method of  claim 1 , wherein said predetermined amount of said sulfur compound is effective to retard both the formation of carbon onto the Ni—YSZ anode and the coarsening of the granular microstructure of the Ni—YSZ anode. 
     
     
         4 . The method of  claim 1 , wherein said step of adding a predetermined amount of a sulfur compound into said reformate stream is performed during the initial start-up of said SOFC stack. 
     
     
         5 . The method of  claim 1 , wherein said step of adding a predetermined amount of a sulfur compound into said reformate stream is performed continuously during the operational life of the SOFC stack. 
     
     
         6 . The method of  claim 1 , wherein said step of adding a predetermined amount of said sulfur compound into said reformate stream is performed during the initial start-up of said SOFC stack and periodically during the operational life of the SOFC stack. 
     
     
         7 . The method of  claim 1 , wherein said sulfur compound comprises H 2   5 . 
     
     
         8 . The method of  claim 7 , wherein said H 2   5  is added into said reformate stream to provide a sulfur concentration of 0.01 to 2.50 ppmv. 
     
     
         9 . The method of  claim 7 , wherein said H 2   5  is added into said reformate stream to provide a sulfur concentration of 0.1 to 2.50 ppmv 
     
     
         10 . A method for adding sulfur to a solid oxide fuel cell (SOFC) stack having a Ni—YSZ anode, comprising:
 feeding a hydrocarbon fuel containing sulfur to a reformer configured to catalyze said hydrocarbon fuel containing sulfur into a reformate stream comprising H 2   5 ; 
 removing or adding H 2   5  into said reformation stream to provide a predetermined concentration of H 2   5  in said reformate stream to prolong the life of said Ni—YSZ anode, while minimizing the degradation of power output of the SOFC stack within a predetermined limit. 
 
     
     
         11 . The method of  claim 10 , wherein said step removing or adding H 2   5  into said reformate stream is performed during the initial start-up of said SOFC stack. 
     
     
         12 . The method of  claim 11 , wherein said step removing or adding H 2   5  into said reformate stream is performed periodically during the operational life of the SOFC stack. 
     
     
         13 . The method of  claim 11 , wherein said step removing or adding H 2   5  into said reformate stream is performed continuously during the operational life of the SOFC stack. 
     
     
         14 . The method of  claim 10 , wherein predetermined concentration of H 2   5  is 0.01 to 2.50 ppmv in said reformate stream. 
     
     
         15 . The method of  claim 10 , wherein predetermined concentration of H 2   5  is 0.1 to 2.50 ppmv in said reformate stream.