Vacuum dessification, a process for removing dissolved gases from water, is a unit
operation in which the pressure in the space above the water is sufficiently reduced
so that solubility of the gas is decreased to below the desired level. The dissolved
gases are released from the water and removed by the evacuating system. Sufficient
packing must be present so that enough surface area between the gas and water is
available to allow the gas present in the water to reach the gas interface and finally
be carried out by the evacuating system.
Two stage Operation
A possible means of reducing both capital and operating costs is the use of a two-stage
vacuum deaerator (I.E. two vacuum deaerator operating in series). Each vacuum deaerator
has its own evacuating system.
Forced draft deaerator in series with vacuum deaerator
When Carbon-dioxide removal is required, a forced draft deaerator is used prior to a
vacuum deaerator. Normally the carbon-dioxide effluent from the force draft deaerator
should be about 10 ppm.