The actual throughput of kaolin ultrafine grinding equipment is heavily determined by grinding principle, target fineness (D50/D98), processing mode (wet or dry), solid‑content of slurry, feed‑size and mineral characteristics. For kaolin, wet stirred mills dominate high‑end coating‑grade production; dry‑type mills (ring‑roller mill, vertical roller mill, ACM classifier mill) are mainly for dry filler‑grade and calcined kaolin powder. Capacity data below refers to dry‑basis output, which is the industry standard for kaolin processing.
1. Wet stirred mill (for delaminated coating‑grade kaolin, wet‑process only)
Target product: D90‑D98 < 2 μm paper‑coating kaolin; high‑aspect‑ratio platelets; slurry solid‑content 70‑75 %.
- Small‑size industrial stirred mill (75‑132 kW, single pass): 1.4‑1.8 t/h dry kaolin (D60 <2 μm)
- Two‑mill series configuration (to reach D95 < 2 μm for top‑coat kaolin): 0.6‑0.9 t/h dry output; finer requirement reduces throughput significantly
- Large‑scale industrial vertical stirred/tower mill (160‑355 kW): 3‑8 t/h dry material, for large kaolin wet‑processing plants
Key note: When tighter particle‑size specification (D95/D98 < 2 μm) is required, capacity drops sharply. Series installation is common for high‑grade coating kaolin, sacrificing output for product quality.
2. Dry ultrafine ring‑roller mill (HGM / GKH series, dry‑process kaolin)
Typical finished fineness: 800‑2500 mesh (5‑15 μm), mostly for dry filler‑grade kaolin and de‑agglomerated calcined kaolin, cannot produce high‑aspect‑ratio delaminated platelets.
- Medium‑size model: 0.7‑3 t/h at 1250 mesh; drops to 0.4‑1.2 t/h at 2000‑2500 mesh
- Large ring‑roller mill: 2‑9 t/h for 800‑1250 mesh kaolin; capacity decreases as target fineness increases
3. Vertical roller mill (VRM, dry grinding)
For large‑volume filler‑grade kaolin and calcined kaolin after calciner, fineness D97 10‑45 μm.
- Medium unit: 5‑22 t/h
- Large industrial unit: 20‑50 t/h, widely used for low‑to‑medium fineness bulk kaolin powder production
4. ACM air classifier mill (dry‑type impact grinding)
Suitable for medium‑fine dry kaolin powder; poor for ultra‑fine D97 < 5 μm production.
- Mid‑size ACM350‑500: 200‑1000 kg/h
- Large ACM700‑900: 1‑4 t/h for 400‑800 mesh kaolin; output falls greatly above 1000 mesh
5. Ball mill (wet or dry mode for kaolin)
- Wet ball mill (medium‑fine kaolin D50 2‑10 μm): 3‑15 t/h, used for pre‑grinding in wet kaolin lines; low efficiency for ultrafine below 2 μm.
- Dry ball‑mill plus air‑classifier circuit: 2‑12 t/h, for dry‑processed filler‑grade kaolin.
Key factors changing actual capacity
- Target particle‑size: The finer the product, the lower the throughput. For stirred mills, capacity may drop by more than 50 % when specification changes from D60<2 μm to D95<2 μm.
- Moisture of feed material: Dry‑type mills suffer capacity loss or blockage with high‑moisture sticky kaolin.
- Solid‑content for wet grinding: Higher slurry solid‑content improves plant throughput but increases slurry viscosity and media wear.
- Mineral hardness and clay plasticity: Plastic kaolin clay reduces effective grinding capacity.
Capacity comparison table for typical kaolin ultrafine mills
| Equipment Type | Processing Mode | Typical Target Kaolin | Typical Industrial Capacity (dry‑basis) |
|---|---|---|---|
| Stirred mill (single) | Wet | Coating‑grade kaolin D60<2 μm | 1.4‑1.8 t/h |
| Stirred mill (2‑stage series) | Wet | High‑grade top‑coat D95<2 μm | 0.6‑0.9 t/h |
| Large vertical stirred mill | Wet | General ultrafine wet kaolin | 3‑8 t/h |
| Ring‑roller ultrafine mill | Dry | Dry filler / calcined kaolin 800‑1250 mesh | 0.7‑9 t/h |
| Vertical roller mill | Dry | Bulk filler‑grade kaolin | 5‑50 t/h |
| ACM classifier mill | Dry | Medium‑fine dry kaolin 400‑800 mesh | 0.2‑4 t/h |
| Ball mill (wet) | Wet | Pre‑grinding / filler‑grade | 3‑15 t/h |
Practical process guidance
- High‑grade paper‑coating delaminated kaolin: adopt wet stirred mill, accept relatively low hourly capacity for platelet quality. Most plants run ball‑mill pre‑grinding + series stirred‑mill fine‑grinding workflow.
- Dry filler‑grade or calcined kaolin powder: choose ring‑roller mill or vertical roller mill for high‑throughput dry production.
- Do not simply compare nominal capacity from manufacturer datasheets; always confirm capacity under your target particle‑size index.
For high‑value wet‑processed coating‑grade kaolin, typical single stirred‑mill capacity ranges 0.6‑8 t/h dry basis, strongly dependent on particle‑size requirements. Dry‑type ultrafine mills deliver higher throughput (up to 50 t/h), but cannot produce high‑aspect‑ratio delaminated kaolin for top‑coat application. Fineness specification is the dominant factor determining real‑world output.
