JACAN ACM air classifying mills can consistently produce powder with D97 <10 μm by combining high-energy impact grinding, precise dynamic air classification, optimised airflow control and system parameter matching. The whole process relies on tight interaction between grinding rotor, classifier wheel and circulating process air.
1. High peripheral speed for fine impact comminution
The grinding rotor with hardened hammers runs at high tip speed. When raw particles strike hammers, chamber liners and collide with one another, coarse grains break into fine fragments. Higher rotor speed increases impact energy, generating enough submicron and fine micron particles to feed the classification zone.
- Hammer tip speed is typically adjusted between 80–120 m/s for D97＜10μm products.
- The grinding gap between hammer tips and chamber liner is kept small and stable to limit oversize particle escape from the grinding zone.
2. High-speed dynamic classifier wheel (core element)
The classifier wheel is the key to cutting D97 below 10 μm. It creates a centrifugal force field opposing the inward drag of process air.
- Fine particles: air drag overcomes centrifugal force, pass through classifier wheel vanes and exit as finished product.
- Oversized particles: stronger centrifugal effect throws them back into the grinding chamber for re-grinding.
To hit D97＜10μm, the classifier wheel rotates at higher speed. Higher wheel speed raises the cut point and rejects more borderline coarse particles. Wheel geometry, vane quantity and vane gap are optimised to minimise particle bypass and prevent coarse powder leakage.
3. Precise airflow management
The inlet scroll supplies stable, uniform tangential air into the grinding chamber. Air volume directly controls particle residence time:
- Reduced process air extends particle residence time inside the grinding zone for repeated impact.
- Too much air carries coarse material prematurely into the classifier and increases D97; too little air causes powder accumulation and agglomeration.
Negative pressure is maintained steadily across the mill, avoiding air leakage which would disrupt classification cut size.
4. System supporting conditions
- Feed control: Low, stable feed rate. Overfeeding overloads the grinding zone, raises particle concentration and worsens classification efficiency, making D97 larger.
- Material pre-treatment: Feed size must be controlled; very coarse feed increases grinding load and makes it harder to reach D97 under 10 micron.
- Anti-agglomeration: Surface moisture and static can create soft agglomerates that falsely increase PSD. Optional inert gas or low-humidity air prevents agglomeration for fine powders.
- Wear part integrity: Worn hammers, liners or classifier vanes change grinding gap and flow pattern, so regular inspection and replacement are required to maintain consistent PSD.
5. Limitations
D97 <10 μm is material-dependent. Hard, dense minerals demand higher rotor/classifier speeds and lower throughput. Soft, elastic materials are harder to mill to D97 under 10 μm because particles deform rather than fracture. ACM achieves D97 under 10 micron by high-speed hammer impact grinding, fine cut-point tuning via high-speed classifier wheel, matched process airflow and controlled feeding. The classifier wheel sets the sharp separation threshold, returning oversize particles for regrinding. Stable negative pressure, intact wear components and proper feed rate are mandatory to maintain the target particle size distribution.
