In this deaerator water will be heated to a temperature of 100 oC -105oC, temperature of water is initially 30 oC - 50 oC. After going through the process of preheating the feed water then flowed into the economizer to be heated back up to the level of temperature 150 oC - 160 oC in which the heating in the economizer using exhaust gases from combustion in the steam boiler or chain grate before the gas was discharged through a chimney or stack.
After to be heated up in economizer, water flowed into the drum boiler before the water is burned in water wall tubes boiler. Then the water inside the boiler to be burned at a temperature of 400 oC - 459 oC, at this form of water has been turned into full steam. But at this level the water can not be used to turn turbines, and therefore at this level after the water turns into steam, steam will be distributed into the superheater to raise the temperature of the steam itself to the level of 500 oC - 600 oC.
Steam at this level is ready to turn turbines and generators to produce electricity play. The remaining steam turbines were going to play back streamed to the deaerator in order to preheat the water in it, that's so deaerator and economizer cycles of use as a supporting instrument in warm water until it becomes steam. We know the function of deaerator is to remove the gases contained in the boiler feed water, after the purification process of water (water treatment).
In addition deaerator heater also serves as the initial water filling the boiler before it is inserted into the boiler. Deaerator works based on the nature of oxygen solubility in water decreases with an increase in temperature. If water from water treatment directly burned in a boiler, it will cause severe corrosion because the water still contains gases that can cause corrosion and so on.
Likewise, if the water is burned directly in steam boilers will not rule out going to use fuel that is not less, because water from water treatment temperature is 30 oC - 50 oC and burned in a boiler with a target temperature of the water into steam at 400 oC and above. From the small sample above shows clearly that the pre-heating the water is very useful for saving fuel.