In the field of solid-liquid separation and sludge dewatering, decanter centrifuges are widely used in environmental protection, municipal administration, chemical industry, food, medicine and other industries due to their high separation efficiency, strong degree of automation and wide adaptability. In recent years, with the continuous expansion of the second-hand market for environmental protection equipment, the market demand for second-hand decanter centrifuges has shown a steady upward trend. So, what is a decanter centrifuge? What is its separation principle? Is there an essential difference between the principle and performance of second-hand equipment and new equipment? This article will comprehensively analyze the “principle of second-hand decanter centrifuge” from the aspects of the structural composition, working principle, technical points, common applications and precautions for the use of second-hand equipment.
Introduction to Decanter Centrifuge
Decanter centrifuge, full name “Decanter Centrifuge”, is a high-speed rotating machine that uses the principle of centrifugal sedimentation to achieve solid-liquid separation. Its core function is to separate the solid particles from the liquid in the mixture through density difference under high-speed rotation conditions, and discharge the deposited solid phase continuously through the screw pusher.
Depending on the working environment and the separated materials, the decanter centrifuge can be divided into single-phase separation (liquid-solid) and three-phase separation (oil-water-slag), and its application range covers:
Municipal sewage treatment
Industrial wastewater dehydration
Chemical material separation
Food processing (such as starch, vegetable protein, oil)
Pharmaceutical industry
Oilfield drilling mud treatment, etc.
Basic principle of Decanter Centrifuge
The separation process of Decanter Centrifuge is mainly based on the physical principle of “centrifugal sedimentation”. When the mixture enters the drum at a certain flow rate, the substances (solids, liquids) of different densities will be layered in the radial direction of the drum under the centrifugal force generated by high-speed rotation.
Its basic principle can be broken down into the following steps:
1. High-speed rotation generates strong centrifugal force
The core component of the horizontal screw centrifuge is the horizontally installed drum, which rotates at high speed driven by the main motor, and the speed is generally between 1500 and 4000 rpm. Because the centrifugal force is much greater than gravity, the solid particles are thrown to the inner wall of the drum in a very short time to form a solid phase layer, while the liquid with lower density is relatively close to the rotation axis to form a liquid phase layer.
2. Screw pusher realizes continuous slag discharge
The screw conveyor (pusher) coaxially installed in the drum has a certain speed difference with the drum (called differential speed, usually 5 to 50 rpm). The screw continuously pushes the solids deposited on the drum wall to the dehydration area or slag discharge port at the small end of the drum, realizing continuous and stable solid discharge.
3. Liquid is discharged through the overflow port
The clear liquid is discharged from the overflow port at the large end or both ends of the drum. Some horizontal screw centrifuges are also equipped with an adjustable weir plate, which can control the separation effect by adjusting the liquid level depth.
Decanter Centrifuge Structure
A standard decanter centrifuge is mainly composed of the following parts:
Drum: The “main battlefield” of the entire separation process, generally made of high-strength stainless steel, corrosion-resistant and wear-resistant.
Screw conveyor: Responsible for continuously conveying sedimentation materials, the surface can be sprayed with wear-resistant materials such as tungsten carbide.
Differential: It realizes precise differential control between the drum and the screw, and is one of the “hearts” of the decanter centrifuge.
Feeding system: Materials are usually introduced into the drum through a hollow shaft or a guide tube.
Frame and shockproof system: Carry the entire machine structure, while reducing vibration and noise during operation.
Electrical control system: Including PLC, human-machine interface, frequency converter, etc., used to achieve automatic control, fault alarm, etc.
Application value of used decanter centrifuge
Compared with buying new equipment, purchasing high-quality second-hand decanter centrifuge has the following advantages:
1. Significant cost savings
The price of second-hand equipment is usually 30%~60% of that of new equipment, which is suitable for start-up environmental protection projects, small enterprises or temporary processing needs.
2. Quick return on investment
Due to low procurement costs and short capital recovery cycle, the project can quickly achieve profitability.
3. Mature and reliable equipment
Many second-hand equipment comes from large-scale enterprise production line upgrades or outsourcing services, with good maintenance and stable performance.
4. Suitable for non-continuous production
For projects with low frequency of use, the input-output ratio of purchasing new machines is low, while second-hand equipment is more economical and practical.
At a time when environmental protection and resource recycling are becoming increasingly important, “second-hand” should no longer be synonymous with quality compromise. On the contrary, if the right equipment is selected and the risks are controlled, the second-hand decanter centrifuge can play a performance comparable to that of a new machine, while bringing higher economic returns. Whether it is a startup company that is launching a project or a large enterprise that is expanding its production capacity, as long as you fully understand the working principle and technical structure of the decanter centrifuge and scientifically select the model, production parameters and supplier according to your own needs, second-hand equipment can also become an important force in the efficient separation system.
If you are considering purchasing a second-hand decanter centrifuge, please contact us. As a professional decanter centrifuge manufacturer in China, we not only provide new equipment, but also provide equipment renovation, testing, commissioning and technical training services to help you achieve more efficient separation effects at a lower cost.
