How Does a Ring Roller Mill Work for ATH

Ring‑roller mill (ultrafine roller mill) is a medium‑to‑high‑capacity mechanical grinding equipment widely used for aluminum hydroxide (ATH). It relies on multi‑layer grinding rollers and grinding rings to deliver compression, rolling and shear size‑reduction, paired with an integrated dynamic turbo air classifier, running in full closed‑circuit circulation. It suits general‑grade and artificial‑stone‑grade ATH, and can also produce cable‑grade ultrafine ATH when properly modified for low‑temperature and anti‑iron‑pollution requirements.

Core Structure

• Main grinding host: multi‑layer grinding rollers, stationary grinding ring, main drive shaft, material throwing disc
• Top‑mounted dynamic air classifier wheel
• Airflow system: fan, cyclone collector, pulse bag‑house dust collector
• Feeding unit, negative‑pressure closed pipelines
• Optional water‑jacket cooling, ceramic‑lined wear parts for high‑purity ATH production

Step‑by‑Step Working Principle for ATH

1. Material feeding and dispersion
   Pre‑dried, deagglomerated ATH raw material is fed into the center of the mill’s rotating turntable. High‑speed centrifugal force throws ATH particles outward into the annular grinding gap between rollers and grinding ring.
2. Multi‑stage rolling‑shear grinding
   Grinding rollers perform both revolution around main shaft and self‑rotation. Centrifugal force presses rollers tightly against the inner surface of grinding ring. ATH particles are squeezed, rolled and sheared in the gap. Multiple stacked roller‑ring layers realize progressive multi‑pass grinding, breaking particles without high‑velocity impact collision typical of ACM mills.

Difference from impact‑type ACM mill: ring‑roller mill mainly uses compression‑shear force instead of high‑speed particle impact, which generates relatively less instant local heat.

3. Air transportation to classification zone
   Ground ATH powder falls onto the bottom throwing disc, which flings powder into the annular airflow channel. System negative‑pressure airflow carries powder upward to the top‑mounted dynamic classifier chamber.
4. Dynamic air classification & closed‑circuit recirculation
   Inside the classifier, centrifugal force from rotating wheel competes with air drag force:

• Qualified fine ATH powder: air drag dominates, passes through classifier‑wheel gaps and flows to cyclone + bag‑house collectors as finished product.
• Oversized coarse particles: centrifugal force dominates, rejected by classifier wheel, fall back down to grinding chamber for re‑grinding together with new feed material, forming closed‑circuit loop.

Fineness adjustment: change classifier wheel rotation speed and system air volume. Higher rotor speed produces finer ATH powder.

5. Powder collection
   Qualified fine ATH is collected by cyclone separator and pulse dust collector. Cleaned air returns to fan to maintain negative‑pressure closed‑loop operation.

Special Requirements When Milling Heat‑Sensitive ATH

ATH decomposes above 150 °C and loses crystal water, so ring‑roller mill must be adapted for ATH processing; standard mineral‑processing configuration cannot be directly used.

1. Cooling configuration
   Add water‑cooling jacket on mill housing and grinding chamber. Control material temperature consistently ≤110 °C. Although compression‑shear grinding produces lower instant heat than high‑speed impact mills, continuous friction heat still accumulates during long‑time running. Without cooling, ATH will dehydrate and lose flame‑retardant performance.
2. Anti‑iron‑pollution upgrade for cable‑grade ATH
   For LSZH cable‑grade ATH, grinding rollers, grinding ring and inner liners need ceramic lining. Unprotected metal‑on‑material wear brings iron contamination, reduces whiteness and degrades electrical performance. General‑purpose ATH for artificial‑stone may use standard alloy wear‑resistant parts.
3. Control feed condition
   Feed ATH must be pre‑deagglomerated and low‑free‑moisture. High‑moisture filter‑cake feed causes material sticking on rollers and ring surfaces, forms material caking, destabilizes grinding efficiency and D97 consistency.

Typical Performance for ATH Production

• Fineness range: D97 5 μm ~ 25 μm
• Capacity: single‑line capacity 1‑6 t/h, depends on target fineness
• For D97 6‑12 μm general‑purpose ATH: ring‑roller mill shows good energy‑efficiency advantage.
• For very fine cable‑grade ATH (D97 2‑4 μm): capacity drops obviously; in this scenario ACM air‑classifier mill is more commonly selected.

Advantages of Ring Roller Mill for ATH

1. Medium‑high throughput, lower specific energy consumption for medium‑fine ATH powder.
2. Lower local hot‑spot risk compared with high‑speed impact mills, when cooling‑jacket works properly.
3. Stable closed‑circuit classification, easy operation for large‑scale continuous production.
4. Robust mechanical structure, lower maintenance frequency for medium‑fineness ATH grades.

Limitations for ATH Application

1. Hard to reach ultra‑fine D97 < 4 μm with high output.
2. Roller‑ring wear will gradually degrade PSD sharpness; regular inspection and replacement of wear‑resistant liners are required.
3. Without ceramic lining, iron contamination restricts its use for high‑end cable‑grade ATH.
4. Sensitive to feed moisture; wet agglomerated filter‑cake will cause sticking inside grinding chamber.

Ring‑roller mill grinds ATH mainly by compression and shear between multi‑layer rollers and grinding ring, cooperating with top dynamic air classifier for closed‑circuit production. It is an economical choice for medium‑fine general‑purpose and artificial‑stone‑grade ATH. To produce qualified ATH filler, water‑jacket cooling and anti‑wear‑pollution lining modification are mandatory to protect ATH crystal‑water and finished‑product purity.