Abstract

The fuel cell stack is a phosphoric acid fuel cell stack which can operate at higher pressures because it does not use steam in the operation of the reformer portion. By being able to operate at higher pressures, the stack displays very low system heat rates and thus higher operating efficiency. The higher operating pressure also results in improved fuel cell power density and reduced cost. The stack is cooled by a coolant mixture of air and entrained water droplets comprising cathode exhaust and injected water fog. During the cooling operation, the water droplets in the coolant mixture are vaporized in the cooling passages of the stack. The exhaust from the cooling system after being heated is then delivered to an autothermal reformer where it reacts with a raw fuel reactant to produce hydrogen for operating the fuel cells in the stack. The reformer does not require a separate burner to operate properly.