A three-phase decanter is a centrifugal separator that separates two immiscible liquids while simultaneously separating the solids. The liquid phases discharge through discrete outlets, and the solids eject out of the decanter’s sludge nozzles.
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The 3-phase separation occurs in the horizontally rotating bowl of the decanter centrifuge. A fixed inlet tube feeds the slurry into the bowl, where the fluids are gently accelerated.
The high centrifugal force causes the heavier solids to accumulate on the bowl wall. The screw conveyor rotates within the bowl at a differential speed to the bowl. The relative rotation between the bowl and the screw pushed the solids to the bowl's conical section.
The centrifugal force drains the liquid from the solids as they move up the conical bowl wall. The conveyor pushes the dry solids through the sludge outlet ports. The ejected solids fall out of the casing vessel.
The entire cylindrical bowl section is the separation surface. The heavy and light liquid phases exit the bowl into individual chambers for each liquid phase in the decanter vessel.
Three-phase decanters are available in 2 design variants. The difference is in the discharge of the separated liquid phases.
In the standard configuration, the heavy and light liquid phases exist the bowl under gravity. In other words, the liquid phases fall into the casing.
A second variation of the decanter has paring disc pump(s) on the separated liquid phases. These centripetal pumps discharge the separated liquid under pressure. As an added benefit, applying back pressure on the liquid phases helps centrifuge efficiency.
Read more about regular or standard 2-phase decanter centrifuges here.
The three-phase decanter centrifuge can adapt to specific process requirements by:
- Changing the bowl rotational speed to exert the best G-force for separation.
- Adjust the scroll differential rotation to balance liquid clarity and sludge handling capacity.
- Calibrate the pond depth to adjust liquid clarity versus solid dryness.
- Interphase adjustment between the heavy and light liquid phases.
- Changing the feed flow rate. These 3-phase decanters can handle a wide range of feed rates.
The benefits of three-phase decanters include:
- The simultaneous separation of two liquids and solids
- The ability to handle a wide range of solids concentrations
- The adjustment of the centrifuge during the process
- Low operating cost for high processing volume
- Compact size to process capacity ratio
- Reduced operator exposure to process fluids by sealed design
- Long service life due to absence of replaceable media
|Three Phase Decanter Model ->||Alfa Laval UVNX-314||Alfa Laval UVNX 418|
|Bowl Diameter||353 mm||353 mm|
|Max. G-Force||3,150 Gs||3,150 Gs|
|Light Phase Liquid Discharge||Gravity||Gravity|
|Heavy Phase Liquid Discharge||Gravity||Gravity|
|Max. Bowl Speed||4,000 RPM||4,000 RPM|
|Bowl Length||860 mm||1,460 mm|
|Net Weight||4,200 Lbs||5,500 Lbs|
|Drive Motor||15 HP||25 HP|
|Noise Level||~ 80 dB(A)||~ 82 dB(A)|
The food and other process industries use the 3-phase decanter extensively. The primary application is to separate a feed slurry of two immiscible liquids and a solid phase.
A typical example would be separating an oil phase from the water and solids phase.
Other specific examples include:
by Sanjay Prabhu MSME
Engineering Manager, Dolphin Centrifuge