PURPOSE: To prevent the oxidation degradation of ion exchanger resin by providing a condensate demineralization device with a regeneration water tank for supplying water to regenerate and preserve positive ion and negative ion exchanger resin in a condensate demineralization tower.
CONSTITUTION: The steam having driven a turbine 103 is condensed in a condenser 105 to be condensate and it is pressurized with a low pressure condensate pump 106 to flow through an air extractor 107 and a ground steam condenser 108. The condensate purified with a condensate filtering device 109 and a condensate demineralization device 110 is reserved in a regeneration water tank 118 through a regeneration water sending pump 119 which are provided downstream of the condensate demineralization device 110. The condensate water in the regeneration water tank 118 is supplied through the regeneration water sending pump 119 to the condensate demineralization device 110 and a regeneration device 115 when it is used for regenerating the ion exchanger resin in the regeneration device 115 or preserving the ion exchanger resin in the condensate demineralization device 110 until the start up of the plant. Thus, low oxygen content water degassed by providing the regeneration water tank 118 can be supplied to the condensate demineralization device 110 and the regeneration device 115 and so the oxidation degradation of the ion exchanger resin is prevented.