Decanter Centrifuge Working Principle
Decanter centrifuge is a kind of sedimentation equipment with horizontal screw discharged and continuous operation. It is mainly composed of a feed port, a decanter bowl, a decanter screw conveyor, a solid phase discharged outlet, and a liquid phase outlet.
First, the raw material is pumped into the decanter centrifuge through the feed port, and then into a horizontal bowl (also called a rotating drum) composed of a cylindrical and a conical part. Then, the bowl and the screw (the screw conveyor of decanter centrifuge) rotate at a high speed in the same direction at a certain differential speed. Due to the higher density, the solids contained in the product settled on the inner wall of the bowl under the action of centrifugal force. The conveying screw continuously pushes the solid phase deposited on the bowl to the cone end of the bowl, then solids is discharged out of the machine. The clarified lighter liquid phase forms an inner liquid ring, which continuously overflows the bowl from the overflow port at the large end of the bowl, and is discharged out of the machine through the liquid discharge port. Eventually to achieve the purpose of separating the solid phase from one or two liquid phases.
Decanter centrifuge is a very important and necessary industrial equipment. Therefore, it is very important and necessary to understand how the centrifuge works.
One of the commonly used industrial machines for separating solids from the liquid is a decanter centrifuge through the high-speed rotation. It has main components such as bowl and screw conveyor.
As you can see from your house washing machine, it uses centrifugal force to dewater the clothes effectively. Also, you can feel a bit unbalanced when you are driving and taking turns. It is also due to centrifugal force.
Centrifugal force causes an object to move in a circular or curved path to move away from the center of this circle or arc path.
Imaging you can a pond filled with muddy sand and water, the sand will eventually accumulated at the bottom of the pond in time.
This is due to sand is heavier than water and by the force of the gravity there will finally be two distinct layers in this pond: water layer in the top and sand layer in the bottom.
Decanting Using Centrifugal Force
To accelerate the decanter time, centrifugal force has brought in to generate as high as 4000 times of the gravity force, Thus reducing the separation time from hours to seconds.
Decanter Centrifuge Design
Decanter centrifuge has both horizontal and vertical types, in this article we only discuss the most used one: horizontal decanter centrifuge.
As shown below, the main components of a centrifuge is:
* 1. Bowl – a rotation assembly where the feeding is processed here. Normally it has a horizontal section and a conical section, the angle of the conical section, also known as beach angle will be adjusted due to different feeding and process requirement.
* 2. Screw conveyor – a helix with spiral flights, its speed is controlled by gearbox and drives.
* 3. Gearbox – mechanism to generate a differential speed. this can be cyclo or planetary gearbox.
* 4. Drive – this can be hydraulical drive or electrical motor.
* 5. Weir plates – adjusting plates for control the performance of the separation.
* 6. Control panels – centrifuge is installed with many electrical sensors, so the control panel can monitor the running operation in terms of feeding capacity, temperature and vibration alarm as well as adjust the parameters such as bowl speed, and differential speed. Also it adapts the PLC programming, where certain level of automation can be achieved, such as auto stop when alarming occurs, increase or decrease of the torque force accordingly.
* 7. Cover, stand and Pipes: some cleaning pipe allowing CIP function while operation.
When in operation, the feed is put into the main chamber of the bowl to achieve separation in the following steps:
* 1. Feeding slurry is sprayed into the main chamber of the bowl.
* 2. High speed rotation of the bowl will generate centrifugal force, this will force the heavier solids move to the wall of the bowl (as the sand decants towards the bottom of the muddy water pond). While the lighter liquid will move to the center layer of the bowl.
* 3. Screw conveyor rotates at a different speed from the bowl by using gearbox and motor drives. This will push the solids to one end of the decanter. At this end, the conical section bowl forms a “beach”, where the solids can be pushed out and discharged. And the liquid is discharged n by overflowing to the exit of the other end of the bowl.
* 4. The outcome performance of the separation, in terms of dryness of the solid and purification of liquid, can be adjusted by weir plates in the bowl end.
Additionally, three phase, liquid /liquid/solid separation can be achieved, this is implemented by letting the light liquid phase to be overflowed from the heavier liquid phase. Moreover solid/solid/liquid separation can also be achieved for the decanter centrifuge.
Through this complete basic guide that introduces the working principle of a decanter centrifuge, I believe you have a very good idea of how the centrifuge works.
Yes, the decanter centrifuge uses the centrifugal force generated by the high-speed rotation, and then realizes the pollution-free sedimentation and separation according to the weight difference between different solid and liquid substances.
The decanter centrifuge of SZ Separation is also developed using this principle. It can not only realize the two-phase separation of solid and liquid, but also realize the liquid/liquid/solid three-phase separation.