www.saVRee.com Deaerators Explained pg.
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What are deaerators?
Deaerators are pressurised feedwater tanks also referred to as open feedwater
heaters. Deaerators are critical components of many steam systems and have several
functions:
•
Remove non-condensable gases from boiler feedwater.
•
Increase the temperature of makeup water as it enters the system.
•
Increase the temperature of condensate prior to it entering the boiler.
•
Provide a storage capacity of treated feedwater.
There are two common deaerator designs, the spray type and tray type (also known as
the spray-tray type). A variation of the spray type is the spray-scrubber type.
Deaerator
All medium to large steam systems require a deaerator to reduce the levels of dissolved
oxygen (O2) and carbon dioxide (CO2) in the boiler feedwater, both of which will cause
corrosion to boiler system components if not removed.
Deaerators achieve deaeration by raising the temperature of the feedwater, which reduces
the solubility of the non-condensable gases i.e. the gases are released from the water.
Once the dissolved gases have been released, the likelihood of corrosion is drastically
reduced and the feedwater can be fed to the boiler.
The Deaeration Process
The process of deaeration may occur mechanically or chemically. Deaerators provide
the mechanical solution whilst chemicals provide the chemical solution.
A typical deaerator will remove almost all dissolved oxygen and CO2, with the remainder
being removed by oxygen scavengers (sodium sulphite, hydrazine etc.) and CO2
scavengers (neutralising amines, bicarbonate etc.).