Purging water with reactant air pump powered by operational fuel cell system during shutdown

Abstract

The air blower ( 18 ) of a fuel cell power plant ( 9 ) is used to force water out of the coolant flow fields ( 27 ) of a fuel cell stack ( 10 ), a coolant pump ( 35 ) and a heat exchanger ( 40 ) through a valve ( 46 ) which is closed during normal operation. The water removal occurs as part of a shutdown procedure in which the fuel cell stack continues to operate so that it provides the power for the air pump and to assist in water removal (such as retaining low vapor pressure). The water flow to an accumulator ( 33 ) is blocked by a valve ( 29 ) during the shutdown procedure.

1 . A fuel cell power plant comprising: 
 a plurality of fuel cells arranged in a stack including coolant flow fields, said fuel cells including oxidant reactant gas flow fields;    an air pump that provides, during normal operation, air to said oxidant reactant gas flow fields; and    means operable as part of a procedure of shutting down the operation of said stack of fuel cells, while said stack of fuel cells is still producing electrical power, for connecting said air pump to water passages comprising at least one of (a) the coolant flow fields in said fuel cell stack, (b) a coolant pump that during normal operation causes coolant to flow through said coolant flow fields, and (c) the primary flow passage of a coolant heat exchanger interconnected with said coolant flow fields, said air pump utilizing at least a portion of said electrical power to operate during said shutdown procedure.    
   
   
       2 . A fuel cell power plant comprising: 
 a plurality of fuel cells arranged in a stack including coolant flow fields, said fuel cells including oxidant reactant gas flow fields;    an air pump that provides, during normal operation, oxidant reactant gas to said oxidant reactant gas flow fields, and, as part of a procedure of shutting down the operation of said stack of fuel cells, while said stack of fuel cells is still producing electrical power, is powered by at least a portion of said electrical power;    a coolant pump that during normal operation causes coolant to flow through said coolant flow fields;    a heat exchanger having a primary flow passage interconnected with said coolant pump and said coolant flow fields; and    means operable during said procedure for connecting said air pump to water passages comprising at least one of (a) said coolant flow fields, (b) said coolant pump, and (c) said heat exchanger.    
   
   
       3 . A method of operating a fuel cell power plant having a plurality of fuel cells arranged in a stack including coolant flow fields, said fuel cells including oxidant reactant gas flow fields which are provided air by an air pump during normal operation, a coolant pump that during normal operation causes coolant to flow through said coolant flow fields, and a heat exchanger having a primary flow passage interconnected with said coolant pump and said coolant flow fields, 
 said method comprising:    as part of a procedure of shutting down the operation of said stack of fuel cells, while said stack of fuel cells is still producing electrical power, connecting said air pump to water passages comprising at least one of (a) said coolant flow fields, (b) said coolant pump, and (c) said heat exchanger, and using at least a portion of said electrical power to operate said air pump.