FUEL CELL POWER GENERATING PLANT

PURPOSE:To keep oxygen concentration in an oxidizing agent or hydrogen concentration in fuel in a specified range to operate a plant by comparing a flow rate detected with a flow rate detector with a setting flow rate, and controlling the opening of a flow rate control valve. CONSTITUTION:When a load 26 varies, oxygen concentration in an oxidizing agent electrode outlet gas varies. In a control circuit 35, a converter 32 receives a load setting value signal (measured value signal) 26, and converts a load signal into a flow rate signal based on a function which specifies the relation of perviously set recycle flow rate and the load so that cell voltage is in a stable range. The deviation of the flow rate signal from an actual flow rate signal sent from a flow rate detector 28 is calculated with an adder 33, and the obtained signal is converted into an opening signal with an adjustor 24 and inputted into a flow rate control valve 27 to operate a valve. As a result, recycle flow rate is controlled in an optimum value. by controlling the flow rate in the recycling line, power generation is performed with steady cell performance retained, and exhaust gas in each electrode outlet is efficiently utilized.