Deaerator Function

Why would it need to do anything else?

Deaerator - Wikipedia, the free encyclopedia

Dear Mr.hossein khosravi fard,

Removal of Oxygen in the feed water is the main function of De-Aerator.

In this process it is increasing the Temp. of the Feed Water entering the Boiler, thereby increasing the Boiler Efficiency.

In other words, the Heat to be Added to raise the Temp is to be totally done by your Boiler Heating Surface, if de-aerator is not put on-line

DHAYANANDHAN.S

By removing air (and especially oxygen) it also minimizes oxidation of susceptible materials and can vastly extend the life of your system- not the function, but definitely the purpose.

Its a long time since I have worked in a power station, but if my memory serves me correctly, yes there is an other purpose for the deaerator. It is used for head pressure into the feed pump, and its volume allows for variation in feed rates, and for making up feed water loses.

Regards JD.

What we are all talking about here is Thermal Deaerators, where the feed water is heated at the required pressure, thereby increasing its temperature over that of boiling water. However, due to this state, there is a need to raise the Deaerator to a height of about 12m above that of the Feed Water Pumps so as not to create cavitation due to collapsing gas bubbles. Nothing to do with Suction Head , but it is mandatory to alleviate the UPV. As correctly stated by Mr. Dhayananthan , the benefit of increased temperature is obvious - about 1% increase in boiler efficiency for every 11 F or 4 C increase in Feed Water temp. Also the main benefit is the excellent Dissolved Oxygen (DO) removal upto 0.007 ppm in outlet feed water to the pumps.

The other type is a Vacuum deaerator, where the opposite is done - lower the boiling point of water under vacuum and expel the oxygen via a live steam eductor to atmosphere. However, in this type we do not get the benefit of a higher feed water temperature and the maximum DO removal is only upto a maximum of 0.34 ppm.

DO causes pitting at the Steam and Mud Drums and therefore during an inspection of the Deaerator , it is imperative that one must see signs of pitting at the Deaerator to be certain that it is functioning. A Deaerator is a sacrificial vessel and is purely to prevent/ minimize pitting within the boiler.

Satish Menon.