Standard high‑speed hammer mill can grind aluminum hydroxide (ATH), but it has significant limitations for producing quality ultrafine filler‑grade ATH. It works well for coarse grinding and pre‑crushing, yet is rarely used as the main finishing mill for LSZH cable‑grade ultrafine ATH.
Working principle difference
Conventional hammer mill relies on high‑speed hammer impact, beating and shear to break particles. Most basic hammer mills do not integrate an internal dynamic air classifier. Fineness is controlled mainly by screen aperture size.
Acceptable application scenarios for ATH
- Pre‑crushing / de‑agglomeration step
Break large lumps, agglomerated filter‑cake ATH before feeding into ACM mill, ring‑roller mill or jet mill. Output D97 ~ 100‑250 μm. This is its most common practical use in ATH lines. - Low‑end coarse ATH products
Produce coarse ATH for filler applications with low fineness requirements, D97 > 40 μm, no strict electrical‑property or low‑over‑size requirements.
Major disadvantages when using hammer mill as final fine grinding mill for ATH
1. Difficult to achieve ultrafine particle‑size
Screen‑type hammer mill has physical limits. Even with fine mesh screens, it cannot stably reach D97 3‑10 μm cable‑grade ATH. Screen blinding frequently occurs: fine, somewhat sticky ATH powder blocks screen holes, throughput collapses and temperature rises.
Note: The ACM air‑classifier mill evolves from hammer‑mill principle, but it removes the screen and adds a high‑speed dynamic turbine classifier. ACM ≠ conventional screen hammer mill. Many people confuse them.
2. High heat generation risk
Repeated high‑speed hammer‑particle impact generates substantial frictional heat. Without dedicated water‑jacket cooling, material temperature easily exceeds 110 °C, triggering thermal decomposition of gibbsite ATH, loss of crystal water and drop of LOI value.
3. Iron contamination risk
Metal hammers and liners suffer continuous impact abrasion. Unmodified standard hammer mill introduces high iron content, bad for high‑whiteness, electrical‑grade ATH. Upgrading to ceramic hammers and liners is possible but expensive; screen itself remains a metal wear component.
4. Poor particle‑size distribution
Without dynamic classification, PSD is broad. Plenty of over‑size coarse particles and excess super‑fine fractions. Cannot meet strict LSZH requirements for low oversized residue.
5. Sensitivity to moisture
Even small residual moisture in ATH feed causes powder sticking on hammers, housing and screen. Screen clogging leads to surging temperature, vibration and unstable output.
Comparison: Conventional hammer mill vs ACM air‑classifier mill for ATH
| Item | Screen‑type Hammer Mill | ACM Air Classifier Mill |
|---|---|---|
| Fineness control | By screen mesh | By dynamic turbine classifier |
| Typical finished D97 for ATH | 40‑200 μm | 3‑12 μm |
| Suitability for cable‑grade ATH | Not suitable | Suitable after cooling & ceramic upgrade |
| Heat risk | High | High, requires water‑jacket cooling |
| Main role | Pre‑crushing | Main fine finishing grinding |
Practical conclusion
- ✅ Yes: Use standard hammer mill for ATH lump breaking and pre‑crushing upstream of main grinding equipment.
- ❌ No: Do not use screen‑type hammer mill as final fine grinding equipment for filler‑grade especially cable‑grade ATH.
- If you want hammer‑style fine grinding for ATH, select ACM air‑classifier mill (screen‑less, with dynamic classifier), equipped with water‑jacket cooling and ceramic wear‑parts.
