1. Overview of the basic structure of the horizontal screw centrifuge
The horizontal screw centrifuge is mainly composed of the following key components:
Drum (Drum / Bowl)
Screw conveyor (Scroll)
Differential Speed System
Solids Discharge Mechanism
Drive system (main motor and auxiliary motor)
Bearing and sealing system
Casing and support frame
Control system (electrical control cabinet, frequency converter, PLC, etc.)
Drum system: the “separation engine” of the horizontal screw centrifuge
1.1 The role of the drum
The drum is the main working chamber for material separation, and all solid-liquid separation processes are completed here. When the drum rotates at high speed, the material is separated into layers under the action of centrifugal force: the solid particles with high density are thrown to the inner wall of the drum, and the liquid remains in the inner layer and is discharged through the overflow port.
1.2 Drum structure composition
Drum material: Commonly used are stainless steel (SS304, SS316L), duplex steel, etc., which have the characteristics of corrosion resistance, wear resistance, and high strength.
Drum design: The combined structure of the straight barrel section + the conical section helps to increase the residence time of the solid on the drum wall and improve the dehydration efficiency.
Liquid outlet design: By adjusting the position of the liquid weir plate, the residence time of the liquid in the drum can be controlled, affecting the separation accuracy.
1.3 Drum size and parameters
Drum diameter (D): directly affects the centrifugal
force. The larger the diameter, the stronger the separation capacity.
Drum length (L): determines the processing volume. The longer the drum, the greater the processing capacity.
Length-to-diameter ratio (L/D): usually between 2.5 and 4.2, reflecting the overall performance of the equipment.
Differential speed system: a “speed regulator” for precise control of solid propulsion
2.1 Definition of differential speed
Differential speed refers to the relative speed difference between the screw conveyor and the drum. Usually, the screw rotates at a slightly slower (or faster) speed than the drum, thereby pushing the solids deposited on the drum wall to move toward the slag outlet.
For example:
Drum speed: 3000 rpm
Screw speed: 2980 rpm
Differential speed: 20 rpm
2.2 The role of differential speed
Control solid residence time: large differential speed, fast propulsion, short solid residence time, low dryness;
Improve dehydration effect: small differential speed, slow propulsion, long solid residence time, more complete dehydration;
Avoid blockage and overload: dynamically adjust the differential speed according to the solid content of different materials to keep the system stable.
2.3 Composition of differential system
The horizontal screw centrifuge mainly realizes differential control through the following three methods:
① Planetary gear differential
Compact structure, high transmission efficiency;
Low cost, suitable for small and medium-sized equipment;
Fixed differential ratio, limited adjustment flexibility.
② Hydraulic differential
Control differential speed through hydraulic oil flow;
Fast response, suitable for complex working conditions;
High maintenance requirements.
③ Variable frequency dual motor differential control
The main motor drives the drum and the auxiliary motor drives the screw;
The differential speed is precisely adjusted by the controller and has strong adaptability;
It is the mainstream configuration of high-end equipment at present.
2.4 Differential speed adjustment strategy
High solid content material: appropriately reduce the differential speed and improve the dryness;
Easy to deposit or sticky material: increase the differential speed to avoid blockage;
Dynamic feedback adjustment: closed-loop control is achieved through the PLC system, and the differential speed is adjusted in real time to adapt to material fluctuations.
Pushing system: a key mechanism for continuous unloading and operation guarantee
3.1 Working principle of pushing system
In the horizontal screw centrifuge, the solids deposited on the drum wall cannot move by themselves, and must be slowly pushed along the axis of the drum by the screw conveyor, and finally discharged from the slag outlet.
3.2 Screw conveyor design
Blade shape: common types include equidistant spiral, variable pitch spiral, reinforced spiral, etc.;
Blade material: usually wear-resistant stainless steel or surfacing tungsten carbide;
Pitch design: determines the propulsion speed and shear strength;
Central shaft hollow design: used to discharge filtrate or coolant.
3.3 Pushing method
Continuous pushing: suitable for stable flow and homogeneous materials;
Intermittent pushing: used to handle highly volatile or high viscosity materials;
Auxiliary devices: such as vibrators and scrapers to assist in slag discharge and improve dry material conveying efficiency.
3.4 Factors affecting the quality of pushing materials
Is the differential speed reasonable?
Is the solid deposition thickness uniform?
Is the material easy to adhere?
Is the pushing blade seriously worn?
Is the slag outlet unobstructed?
