A Free water knock out skid gives the incoming mixture of oil and free water time to separate. The vessel is designed so that all liquid will move at an even rate through the vessel, and not channel (accelerate).
Free-Water-Knock-Outs (FWKO) should be placed near the beginning of the process flow. This ensures downstream equipment does not have to be sized with the large water volume.
The water being heavier than the oil will sink to the bottom. The oil will move over a weir to a separate part of the tank. The water is removed from the bottom of the vessel.
Free Water Knock out Features
The internal design allows the liquid to flow at an even rate through the vessel and not channel. Free Water Knock Outs are used where the oil and water exist separately are not in an emulsion, and easy to separate.
The degree of separation depends on:
- The available retention time.
- The density differential between the two fluids (larger differential means better separation)
- The operating temperature of the flowing fluids.
- The presence or absence of slugging flow.
- Interfacial area available for separation
