The Basic Structure and Principle of Horizontal Spiral Centrifuge

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The structure of the horizontal spiral centrifuge is horizontal, which is a settlement equipment that can be continuously operated and uses screws for unloading. It belongs to the spiral unloading settlement centrifuge, abbreviated as the horizontal spiral centrifuge.

Generally speaking, horizontal screw centrifuges have the characteristics of compact structure, continuous operation, stable operation, and strong adaptability. They also have large production capacity, convenient maintenance, and good dehydration effect. Therefore, their application in the field of environmental protection is becoming increasingly widespread.

Although different specifications or models of horizontal screws from different manufacturers have different equipment structures, equipment materials, specifications, and operation adjustment mechanisms, their basic equipment principles are similar. Therefore, I will take the Alfa Laval equipment, which is widely used in the industry, as an example to give you a brief introduction, in order to facilitate better use and adjustment by on-site users.

Working principle of horizontal screw centrifuge

The horizontal spiral centrifuge mainly consists of a drum, a screw, a differential, etc. The drum rotates at high speed, and the screw and drum rotate in the same direction but at a slightly lower speed.


Drum – Utilizing high-speed rotation to achieve ideal settling separation;Spiral – conveying and compressing sludge;

Differential – creates a speed difference between the drum and the screw;

Clear liquid outlet – recover the liquid phase through overflow, i.e. clear liquid;

Slag discharge port – solid phase, i.e. sludge, is recovered by gravity.


The horizontal spiral centrifuge utilizes the solid-liquid specific gravity difference and centrifugal force to achieve solid-liquid separation, and its working process is as follows:

The suspension continuously enters the drum through the feed pipe (hollow shaft) and is then thrown into the drum cavity. The high-speed rotation of the drum generates a very strong centrifugal force, and the solid particles (sludge) adhere to the inner wall of the drum due to the centrifugal force and continuously accumulate. The solid layer formed is a circular layer, also known as a solid ring layer;

The liquid phase water also forms a liquid layer due to the centrifugal force, but due to its density being smaller than that of solid particles, the centrifugal force acting on it is also smaller than that of solid particles. It is located on the inner side of the solid ring layer and is called the liquid ring layer.

By utilizing the relative motion generated by the difference in rotational speed between the drum and the screw, the solid ring layer is pushed to the cone end of the drum, and the sludge is continuously discharged from the slag discharge port distributed at the cone end; The liquid ring layer turns to the large end of the drum, and there is an overflow port distributed at the large end of the drum. The liquid overflows from the overflow port and is discharged through the discharge port, forming a separated liquid (i.e. clear liquid).

Factors affecting the separation effect of horizontal spiral centrifuge

To understand the separation effect of a horizontal spiral centrifuge, one must first understand its working principle, so that it can be effectively controlled during use.

The speed of the centrifuge drum

The adjustment of drum speed is usually achieved through variable frequency motors or hydraulic motors. The increase in drum speed will improve the separation effect. The higher the speed, the greater the centrifugal force, which helps to improve the solid content of the mud cake.

Increasing the speed difference between the spiral and the drum increases the processing capacity, but too fast a speed can cause the destruction of the sludge flocculent, which in turn reduces the dewatering effect. The higher the rotational speed, the higher the solid dryness may not necessarily be.


In addition, higher rotational speeds can cause machine vibration, increase wear on the machine, and correspondingly increase power consumption, vibration, and level, reducing the service life of the equipment.

Therefore, it is necessary to choose a reasonable speed to meet the separation requirements.

Feed flow rate (processing capacity)

The feed flow rate affects the retention time of materials in the equipment, which in turn affects the separation effect.

A smaller processing capacity results in a smaller axial flow rate of the feed liquid, longer residence time in the drum, and better separation effect; On the contrary, excessive feed flow rate will reduce the separation effect.

In addition, the feed flow rate is also related to the solid content of the feed liquid and the slag removal ability of the centrifuge screw. Excessive feed flow rate may cause blockage of the drum and affect the separation effect.

Therefore, it is necessary to reasonably select the feed flow rate to match the solid content and separation requirements of the feed liquid.

Overflow plate diameter

The large end of the drum is equipped with an overflow plate, which can control the liquid depth of the liquid ring layer by adjusting the diameter of the overflow plate.

A small diameter overflow plate can increase the depth of the liquid ring layer, resulting in high clarity of the separated liquid; On the contrary, increasing the diameter of the overflow plate results in low clarity of the separation solution and poor separation effect.

Differential speed between drum and spiral

The differential speed directly affects the slag discharge capacity, mud biscuit degree, and filtrate quality, and is one of the important parameters that need to be adjusted according to the operating situation in the operation of the horizontal screw centrifuge.

A smaller differential speed has better separation effect, but due to the longer residence time of solid particles in the drum, it is easy to cause blockage; A large differential speed results in poor separation effect due to the large disturbance of the spiral on the liquid layer, but has good slag removal ability.

Therefore, the differential speed can be determined based on material properties, processing capacity, processing requirements, and centrifuge structural parameters. Small solid content matches small differential speed, while large solid content matches large differential speed.

Aspect ratio

The larger the aspect ratio of a horizontal spiral centrifuge, the stronger its processing capacity and the better the separation effect.

Characteristics of suspension

The separation effect varies depending on the size of solid particles in the material and the centrifugal force applied.

The larger the particle, the easier it is to separate; Particles that are too small are easily mixed in the separation solution and overflow with the separation solution.

In addition, the specific gravity difference between the solid and liquid phases and the viscosity of the suspension also affect the separation effect. The larger the weight difference between the solid and liquid phases, the easier it is to separate, while the smaller the viscosity of the suspension, the easier it is to separate.

Of course, in addition to the above factors, there are many factors that affect the separation effect of the horizontal spiral centrifuge, such as the thickness of the liquid ring layer and process factors, and these factors also affect each other. The treatment effect is the result of the comprehensive effect of the above factors.

I believe that upon seeing this, everyone has a certain understanding of the basic structure of the horizontal spiral centrifuge. However, due to space limitations, many knowledge has not yet been introduced. If you want to further grasp the structural principles and separation and adjustment methods of the horizontal spiral centrifuge, please contact us!

Tags :
centrifuge,Horizontal Decanter Centrifuge,horizontal screw centrifuge,horizontal spiral centrifuge,sludge treatment,solid-liquid separation
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