Hybrid Autothermal Steam Reformer for Fuel Cell Systems

Abstract

A reactant processing module with a hybrid autothermal reformer (HASR) can allow for control of both the amount of cathode recirculation and the amount of water sent to the HASR. At the beginning of life of the fuel cell, reactant processing module can operate on full cathode recirculation. As the fuel cell begins to age and become less efficient, the amount of nitrogen-heavy, vitiated air from the fuel cell cathode can be monitored by a control system and restricted using a valve. In order to compensate for the aforementioned restriction, the rate of input of the external air supply is increased to the HASR and the deficit in water is supplied in liquid form from a water reservoir and turned to steam within the HASR. The amount of liquid water input from the water reservoir that meets the need for continued efficient operation is relatively small.

What is claimed is: 
     
         1 . A hybrid autothermal steam reformer (HASR) included within a reactant processing module having a variable cathode air recirculation system and a water delivery system, the reactant processing module providing a reformate stream to a power generation module, the HASR comprising:
 an enclosure including:
 an autothermal reformer; 
 a water inlet fluidly coupled to the water delivery system; 
 an air inlet in fluidly coupled to the variable cathode air recirculation system; and 
 a reformate stream exit fluidly coupled to the power generation module, 
   wherein said autothermal reformer receives a refined fuel and a quantity of air, said quantity of air received from the power generation module via the variable cathode air recirculation system when said autothermal reformer is operated in full cathode recirculation, and wherein said autothermal reformer receives said refined fuel, a quantity of external air via the variable cathode air recirculation system, and a quantity of water received from the water delivery system when said quantity of air received from the power generation module becomes nitrogen-heavy.   
     
     
         2 . An HASR according to  claim 1 , wherein said autothermal reformer monitors the quality of said quantity of air received from the power generation module via the variable cathode air recirculation system. 
     
     
         3 . An HASR according to  claim 2 , wherein said autothermal reformer includes a control system for monitoring the quality of said quantity of air received from the power generation module via the variable cathode air recirculation system. 
     
     
         4 . An HASR according to  claim 2 , wherein said control system restricts said quantity of air when said quantity of air has a nitrogen content greater than about 48%. 
     
     
         5 . An HASR according to  claim 1 , wherein said air inlet is fluidly coupled to a controllable valve, said controllable valve being adjustable to allow for decreases in said quantity of air received from the power generation module via the variable cathode air recirculation system and increases in said quantity of external air. 
     
     
         6 . An HASR according to  claim 5 , wherein said controllable valve is a three-way valve. 
     
     
         7 . A power generation system comprising:
 a FAWD module capable of producing a refined fuel stream;   a reactant processing module capable of receiving said refined fuel stream and producing a reformate stream;   a power generation module capable of receiving said reformate stream and providing to said reactant processing module a quantity of air; and   a control system in communication with said reactant processing module and said power generation module,   wherein said control system monitors said quantity of air and determines whether said reactant processing module can operate in a full cathode recirculation mode or if an external air and/or water supply is necessary for efficient operation of said power generation module.   
     
     
         8 . A power generation system according to  claim 7 , wherein said reactant processing module includes a variable cathode recirculation system. 
     
     
         9 . A power generation system according to  claim 8 , wherein said variable cathode recirculation system is fluidly coupled to said power generation module and receives said quantity of air and is fluidly coupled to an external air source. 
     
     
         10 . A power generation system according to  claim 8 , wherein said variable cathode recirculation system includes a multi-port valve. 
     
     
         11 . A power generation system according to  claim 10 , wherein said multi-port valve is a three-way valve. 
     
     
         12 . A power generation system according to  claim 8 , wherein said reactant processing module includes a water delivery system. 
     
     
         13 . A power generation system according to  claim 12 , wherein said water delivery system includes at least one of a water reservoir, a potable water input line, and a condensate input line in fluid communication with power generation module. 
     
     
         14 . A power generation system according to  claim 13 , further including a burner module and wherein said water delivery system recovers water from said burner module. 
     
     
         15 . A power generation system according to  claim 7 , wherein said power generation module is a fuel cell. 
     
     
         16 . A power generation system according to  claim 15 , wherein said fuel cell is a high temperature polymer electrolyte membrane fuel cell. 
     
     
         17 . A method of improving the efficiency of a fuel cell system comprising:
 monitoring an air stream from a fuel cell cathode;   determining the degree of vitiation of the air stream;   increasing a rate of input of an external air supply to a reactant processing module based upon said determining; and   increasing a rate of input of an external water supply to the reactant processing module based upon said determining.   
     
     
         18 . A method according to  claim 17 , wherein the external water supply is a water reservoir in fluid communication a hybrid autothermal steam reformer included within the reactant processing module. 
     
     
         19 . A method according to  claim 17 , wherein the fuel cell system includes a variable cathode recirculation system and wherein said variable cathode recirculation system performs said monitoring and said increasing a rate of input of an external air supply. 
     
     
         20 . A method according to  claim 17 , wherein said increasing a rate of input of an external water supply reaches a maximum of about 0.66 liters per day per kilowatt.