Turbo air classifier is the core dynamic grading equipment matched with ultrafine kaolin grinding lines. Its classification efficiency refers to the recovery rate of qualified fine particles from the feed material, which is a key index to evaluate the performance of closed-loop kaolin milling systems. It is not a fixed value and changes significantly with material properties, target cut size, system airflow and equipment design.
Working principle brief
The turbo air classifier separates powder by balancing centrifugal force from the high-speed turbine rotor and air drag force. Qualified fine particles pass through turbine blade gaps and are collected as finished products; coarse particles are thrown outward, fall down and return to the mill for regrinding. Secondary air inside the chamber washes agglomerated powder, stripping fine particles sticking to coarse fractions and boosting overall classification efficiency.
Typical efficiency range for kaolin processing
For ultrafine kaolin (D97=5–10 μm, paper coating and filler grade), the JACAN turbo air classifier delivers:
- Stable operating efficiency: 75% – 88% under normal continuous production conditions
- Ideal optimized conditions: up to 90%+, when feed powder is well dispersed, low agglomeration, proper solid-gas ratio and stable airflow
- Lower limit: 65%–75%, appears when target fineness is extremely fine, kaolin has high moisture, severe particle agglomeration or overloaded feeding
Note: Classification efficiency here means fine particle extraction rate, different from classification sharpness. Even at high extraction efficiency, cut sharpness determines how few oversized particles remain in final kaolin powder.
Main factors affecting turbo air classifier efficiency
- Target cut size
Finer cut point (smaller D97) reduces efficiency. Producing D97=3–5 μm ultrafine kaolin is harder to separate, so efficiency drops obviously compared with 10–20 μm grades. - Kaolin powder dispersion status
Kaolin is easy to form soft agglomerates. Undispersed clusters carry fine particles into coarse return material and directly reduce recovery. Pre-dispersion and secondary air washing are critical. - Solid-gas ratio (feed concentration)
Overfeeding increases powder concentration inside the classification chamber, causes particle collision and re-agglomeration, and lowers classification efficiency. Too low feed reduces throughput and raises unit energy consumption. - Rotor speed & airflow matching
Turbine speed sets the cut point; main fan airflow controls material conveying. Mismatched speed and airflow will deteriorate separation performance. - Equipment condition
Worn turbine blades, accumulated powder buildup on the chamber wall and blocked air channels disrupt the flow field, reducing classification efficiency and broadening particle size distribution.
How to improve classification efficiency for kaolin lines
- Adjust secondary air volume to fully deagglomerate clustered kaolin powder.
- Stabilize feeding rate and control solid-gas ratio within the design range.
- Match rotor speed and induced draft fan airflow according to target PSD.
- Keep classifier rotor and inner chamber clean, regularly inspect blade wear.
- Install pre-dispersion device before classification for sticky kaolin raw material.
For industrial kaolin ultrafine grinding, the practical classification efficiency of JACAN turbo air classifier mainly falls in 75%–88%. It can reach above 90% under ideal material and operating parameters. Finer product requirements, high moisture and particle agglomeration will drag efficiency down. Operators should optimize airflow, rotor speed and feed concentration together to balance classification efficiency, product particle size sharpness and production capacity.
