The paper industry requires different calcium carbonate mills based on whether the product is for filler (inside the paper sheet) or coating (surface application), with critical distinctions in particle size, distribution, and production method (dry vs wet). Below is a structured guide to the most suitable mills and their applications.
Key Paper Industry Requirements for Calcium Carbonate
| Application | Target Particle Size | Critical Properties |
|---|---|---|
| Paper Filler | D50: 2-5 μm, D97 ≤ 10 μm | Narrow PSD, high whiteness, low abrasion |
| Paper Coating | D50: 0.7-2 μm, D90 ≤ 2 μm | Ultra-fine, tight PSD, excellent dispersion |
1. Dry Grinding Mills (Filler & General Applications)
Dry mills are ideal for producing filler-grade GCC (Ground Calcium Carbonate) and pre-grinding for wet processes. They offer lower investment, shorter setup, and lower operating costs.
Vertical Roller Mill (VRM) / Ultrafine Vertical Mill
- Best for: High-volume filler production (325-3000 mesh, D97 ≤ 5 μm) and premium coating pre-grinding
- Advantages:
- Integrated crushing, drying, grinding, and classifying
- Precise particle control with dynamic classifiers (99.9% efficiency)
- Energy-efficient (30% lower consumption than jet mills)
- Low iron contamination (critical for paper whiteness)
- High single-machine capacity (1-50 t/h)
- Recommended models: HLMX, CRLMX, SCM Ultrafine Mill
Air Classifier Mill (ACM)
- Best for: Filler-grade GCC with controlled PSD and high whiteness
- Advantages:
- “Integrated grinding and classification” design removes oversized particles
- Produces narrow PSD with high dispersibility
- Suitable for upgrading Raymond mill output to paper-quality standards
- Low maintenance and stable operation
Raymond Mill / Trapezium Mill (MTW Series)
- Best for: Standard filler production (30-325 mesh) and high-capacity pre-grinding
- Advantages:
- Robust design for continuous industrial operation
- Curved air duct reduces resistance and improves efficiency
- Cost-effective for medium-fineness requirements
- Low investment for small-to-medium production lines
2. Wet Grinding Mills (High-End Coating Applications)
Wet mills are essential for producing ultra-fine GCC slurry for premium paper coatings (D90 ≤ 2 μm, D97 ≤ 2 μm), as they prevent particle agglomeration and achieve superior fineness.
Wet Stirred Mill / Attritor
- Best for: Ultra-fine coating-grade GCC slurry (d90 ≤ 2 μm)
- Advantages:
- High shear force from zirconia/ceramic beads for micro-refinement
- One/two-stage continuous grinding for precise PSD control
- Excellent particle dispersion (critical for coating performance)
- Low iron contamination with ceramic media
- Common configuration: Paired with storage tanks, pumps, and screening systems
Horizontal Bead Mill / Sand Mill
- Best for: High-performance paper coating pigments
- Advantages:
- Closed-vessel design for intense media collisions
- Ideal for producing sub-micron particles (0.2-1 μm)
- High throughput for large-scale paper mills
- Consistent particle size distribution batch-to-batch
3. Selection Guide: Which Mill to Choose?
| Paper Application | Recommended Mill Type | Particle Size Target | Key Benefits |
|---|---|---|---|
| Standard Paper Filler | Raymond Mill / Trapezium Mill | D97 ≤ 10 μm | Low cost, high volume, reliable |
| Premium Paper Filler | Vertical Roller Mill | D50: 2-5 μm, D97 ≤ 5 μm | Energy-efficient, low iron, precise control |
| Coated Paper (General) | Air Classifier Mill | D97 ≤ 3 μm | Narrow PSD, high whiteness |
| High-Gloss Coated Paper | Wet Stirred Mill + Bead Mill | D90 ≤ 2 μm | Ultra-fine, excellent dispersion, smooth coating |
| Stone Paper Production | SCM Ultrafine Mill | 325-2500 mesh | Industry benchmark for ultra-fine GCC |
4. Critical Selection Factors for Paper Mills
- Particle Size Precision: Coating applications demand tighter control (D90 ≤ 2 μm) requiring wet mills or advanced dry ultrafine mills
- Iron Contamination: Paper requires high whiteness—choose mills with ceramic/zirconia components to avoid iron pickup
- Production Scale:
- Small-to-medium: Raymond Mill or ACM
- Large-scale: Vertical Roller Mill (dry) or Wet Stirred Mill (coating)
- Cost Considerations:
- Dry mills: Lower investment and operating costs
- Wet mills: Higher upfront cost but necessary for premium coatings
- Energy Efficiency: Vertical Roller Mills and ACMs outperform traditional ball mills by 30%+
For filler applications, prioritize Vertical Roller Mills (high efficiency, low iron) or Raymond Mills (cost-effective for standard grades)
For coating applications, use wet grinding systems (stirred mills + bead mills) to achieve the required ultra-fine particle size and dispersion
For dual-purpose plants (filler + coating), consider a combination of dry pre-grinding with wet finishing for optimal flexibility and quality
