Classification technology, as an important part of powder material preparation and processing, plays a vital role in powder production. In recent years, with the development of modern high-tech and new material industries, the fine powder industry has grown rapidly. Ultrafine powders have been widely applied in many fields, and the demand for finer particle size and higher output continues to rise. Achieving ultrafine classification of powders has become increasingly difficult. Traditional grinding alone can hardly produce qualified powders in a single step. Classification is therefore necessary to separate powders that meet the required particle size. Hence, classification technology has become the key to mechanical production of fine powders.
Powder Classification Technology Overview
Powder classification technology separates particle groups based on differences in physical properties (such as particle size, density, and shape) under specific force fields (centrifugal force, gravity, inertial force, etc.). The core objective is to avoid over-grinding and to improve product uniformity. It is widely used in industries such as chemicals, food, mineral processing, and pharmaceuticals. Based on the medium, classification can be divided into wet classification (water medium) and dry classification (air medium). Among them, dry classification has become the mainstream due to its high efficiency and convenient operation.
Wet Classification
In wet classification, water is used as the medium. The most obvious advantage is that it helps particle dispersion. Electrostatic and other interactions between particles are weakened in water, reducing agglomeration and improving classification performance. However, the main drawback is that after classification, powders are wetted by water. They require solid-liquid separation and drying, which may lead to re-agglomeration and increased costs.
Gravity Sedimentation Method: This relies on the balance between gravity and drag force. The feed enters the flowing water medium, disperses, and settles. Larger or heavier particles settle faster, while smaller particles settle more slowly. Due to lateral flow, different particles take different movement paths. At the bottom, particles distribute according to size and are separated into multiple grades by a multi-chamber structure.
Centrifugal Method: In this method, particles of different sizes experience different centrifugal forces. Slurry enters a hydrocyclone chamber tangentially. Larger, heavier particles are pushed outward by stronger centrifugal force, spiral down along the cone, and exit through the underflow. Smaller particles remain near the center and are discharged from the overflow. Thus, particles are separated according to size.
Dry Classification
Dry classification uses air as the medium. Since particles are not wetted, no post-treatment like drying or dispersion is needed. It has become the mainstream form of classification. Depending on the type of forces acting on the particles, dry classification methods include gravity, inertial, and centrifugal classification.
- Gravity & Inertial Classification: Both rely on differences in particle mass and motion paths under gravity or inertia. Heavier particles settle or move differently than lighter ones, achieving separation.
- Centrifugal Classification: In centrifugal classification, particles are subjected to aerodynamic drag and centrifugal force. Under these combined forces, particles of different sizes move in different directions and are separated. Depending on the way centrifugal force is generated, centrifugal classification equipment can be further subdivided into several structural types for different applications. At present, centrifugal classifiers are the most widely used and common type of dynamic classification equipment.
এপিক পাউডার
Epic Powder provides advanced powder classification equipment tailored for various industries. From wet and dry classification to dynamic centrifugal systems, our solutions ensure precise particle size control, improved product uniformity, and higher efficiency. With over 20 years of expertise in ultrafine powder processing, Epic Powder helps customers achieve reliable, scalable, and cost-effective classification for modern industrial applications.
