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rapid liberation of dissolved gases. The deaerated water then collects in the feedwater tank
and is ready for use as boiler feedwater.
Spray Scrubber Deaerator
Design Considerations
The type of deaerator chosen for a steam system is heavily dependent upon the system.
Some systems are effectively closed-loop systems which require very low amounts of
makeup water (1-3%); other systems require large amounts of makeup water. The
temperature of the returned condensate is also a factor that must be accounted for.
Steam System Comparison
A power plant steam system providing steam to steam turbines has the following
characteristics:
•
Operates within a closed system and so requires little makeup water.
•
Is not exposed to atmosphere, so there is little chance of gas entrainment.
•
Returns condensate at a temperature near the saturation point of the water and
thus contains low amounts of oxygen and carbon dioxide.
A paper pulp plant steam system has the following characteristics:
•
Operates within an open system with condensate returns typically less than 50%.
Consequently, makeup water requirements for the system are typically 50% or
more.
•
Is exposed to atmosphere, so gases will become entrained in the condensate.
•
The reduction in pressure and temperature is large, which increases the solubility of
gases in the water.
Deaerator Entry Point