PURPOSE: To prolong the lifetime of an ion exchange resin and reduce the maintenance/management costs by furnishing a composite deaerator device between a condenser and an ion exchange type water processing device, wherein the deaerator device includes an aeration type deaeration part and a heating type deaeration part which are constructed in a single piece structure.
CONSTITUTION: Mixture water sprinkled over the fill layer 22A of an aeration type deaerator device 22 makes encounter touch directly with the air fed from below by a blower 24 to cause partial deaeration of the dissolved gas. Further the mixture water drips into a heating type deaeration part 23 of single piece construction, is heated by a thermo-medium flowing through a heat exchanger 23A, and undergoes a convection touching with the air sent to the water surface from the blower 24. Thereby coal dioxide gas, HCl gas, etc., in the mixture water are released to the air, and a mixture water 28 whose included ion quantity is reduced, is stored in the deaeration part 23. If this is sent to an ion exchange type water processing device 15 via a pump 13 and a cooler 14 to undergo purification, the lifetime of the ion exchange resin can be prolonged greatly, and the running cost of the device be reduced.