Forced draft degasifiers are used to strip objectionable gases from water. This is done by passing the water over a media that will cause the water to form a film over the media.  This makes it easier for the entrained gases to be released.  A counter current airflow is introduced at the bottom of the tower and travels up through the descending flow of water.  The gases are stripped as the air passes over the surface area of the water covering the packing.

Forced Draft Degasifier installed at Alcorn (tank on the very top of the picture)

Forced draft degasifiers are used in demineralizer applications to strip CO₂ following a strong acid cation exchanger or softening applications following a weak acid cation exchanger.  They can also be used as an economical way to strip hydrogen sulfide or volatile organic compounds (VOC).

Several different sizes and types of packing are available for different applications.  The smaller sized packing is more efficient due to the greater surface area per cubic foot, but is generally more expensive than the less efficient larger packing.

Materials of construction for the tower also vary depending on the application. The most common construction is FRP.  Since the tower operates at atmospheric pressure, FRP is the most cost effective and corrosion resistant material that can be used. For retro fits where access is limited, a wood stave construction can be used.  The tower can be constructed on site in an area that would not allow access to install a one-piece FRP or steel tower.