In modern industrial production, decanter centrifuges are widely used in many fields such as petrochemicals, environmental protection, municipal sewage, food processing, pharmaceuticals, mineral separation, etc. due to their high efficiency, high degree of automation, and stable operation. However, many users often overlook a key factor in practical applications: the huge influence of the physical properties of the processed materials on the centrifugal separation performance. This article will analyze the physical properties and deeply explore the key physical properties that affect the separation performance of decanter centrifuges, including solid particle size and distribution, density difference, viscosity, concentration, temperature, oil content, etc., combined with typical cases, data analysis and application scenarios, to provide users with a reference for scientific selection and process optimization.
Brief description of the separation principle of the decanter centrifuge
The decanter centrifuge mainly relies on the centrifugal force generated by high-speed rotation to continuously separate the solid phase and liquid phase in the mixed liquid. Its core working structure includes a drum, a screw propeller, a motor, a differential, a feeding system and a slag discharge system.
In the high-speed rotating drum, the mixed material is subjected to a huge centrifugal force, the dense solid phase is thrown to the outer wall, and the lighter liquid phase moves toward the center. The screw propeller rotates at a certain differential speed, continuously pushing out the deposited solids to achieve continuous solid-liquid separation.
The separation effect of the decanter centrifuge is affected by many factors. In addition to the parameters of the equipment itself (such as drum diameter, speed, aspect ratio, differential speed, spiral structure, etc.), the physical properties of the processed material are also one of the decisive factors.
Main physical parameters affecting separation performance
1. Solid-liquid density differenc
The solid-liquid density difference is one of the “driving forces” of centrifugal separation. The greater the density difference, the easier it is to separate the solid phase from the liquid phase.
Impact description:
When the density difference is small (such as sludge, emulsion, etc.), the centrifuge separation efficiency decreases significantly, and liquid turbidity and solid entrainment are prone to occur;
When the density difference is large (such as ore pulp, sand and water), the solid settles quickly and the separation is clear.
Countermeasures and suggestions:
For materials with too small density difference, appropriate heating or pH adjustment can be used to change the relative density;
In process selection, for low density difference systems, a higher speed or a special drum type (such as a drum with a small cone angle) needs to be used to enhance the separation ability.
2. Liquid viscosity
Liquid viscosity is a physical quantity that measures the resistance to liquid flow and has a significant inhibitory effect on the particle settling rate.
Impact description:
The higher the viscosity, the greater the particle settling resistance and the lower the separation effect;
Especially in low temperature or high concentration organic matter systems (such as sludge, fermentation broth), the increase in viscosity significantly reduces the separation efficiency;
Viscosity also affects the liquid distribution, reflux flow pattern, solid transportation, etc. inside the centrifuge.
Countermeasures and suggestions:
Appropriately increasing the processing temperature (such as heating to 40~60℃) can significantly reduce the viscosity;
Design a reasonable feeding system to avoid excessive adhesion caused by shearing;
Pre-dehydration, pre-precipitation, chemical conditioning and other means can be used to reduce viscosity.
3. Solid content and concentration
Solid content is an important indicator to measure the proportion of solids in raw materials, which has a direct impact on the processing capacity and slag discharge effect of the centrifuge.
Impact description:
When the solid content is low (<1%), there is less deposition, high energy consumption, and low unit efficiency;
When the solid content is high (>10%), the equipment load increases, the drum or spiral is easily blocked, and a strong discharge system is required;
High solid content will also accelerate the wear of the drum and spiral, shortening the maintenance cycle.
Countermeasures and suggestions:
Reasonably design the feed concentration to match the equipment throughput and slag discharge capacity;
Use two-stage dehydration or configure a double-spiral high torque structure for high-concentration materials;
The variable frequency control system can be configured to adjust the differential speed in real time to cope with concentration fluctuations.
4. Temperature
Temperature indirectly affects the viscosity, density, particle state, etc. of the material, thus causing a comprehensive impact on the separation performance.
Impact description:
Appropriate temperature increase can reduce the viscosity of the liquid phase, promote particle desorption, and improve separation efficiency;
However, excessive temperature may cause problems such as loss of volatile components and aging of equipment seals.
Countermeasures and suggestions:
For high viscosity systems, it is recommended to heat to 30~50℃;
Use explosion-proof seals and high-temperature resistant materials to ensure safe operation;
The horizontal screw centrifuge should have a thermal balance design to prevent condensation or scaling due to temperature differences.
5. Oil content or emulsification characteristics
For oily sludge, oil-water mixtures, etc., the adhesion and emulsification stability of oil molecules will greatly interfere with the solid-liquid separation process.
Impact description:
The oil phase is adsorbed on the surface of the particles to form an oil-in-particle or particle-in-oil structure;
It makes it difficult for solids to settle and the liquid phase oil content exceeds the standard;
It is easy to form foam and adhere to the drum, affecting the stable operation of the equipment.
Countermeasures and suggestions:
Add demulsifier for chemical conditioning;
Increase the drum speed to enhance separation force;
Optimize the drum cone angle and sedimentation zone length to enhance oil removal capacity.
Optimize the configuration of the decanter centrifuge
To adapt to the differences in the physical properties of different materials, modern decanter centrifuges have a variety of optional structures and intelligent control solutions:
Variable frequency speed regulation system: can adjust the drum speed and differential speed to achieve dynamic adaptation;
Automatic dosing system: can be used with flocculants to improve particle sedimentation;
Optimize the structure of the conical drum: choose different cone angles, pitches, and compression ratios to adapt to different concentrations;
Material customization: select duplex steel, tungsten carbide coating, etc. for highly corrosive and highly abrasive materials;
Intelligent control system: real-time monitoring of concentration, torque, current, etc., and precise adjustment of operating parameters.
