Abstract
In large semi-autogenous grinding (SAG) mills, the lining plates are subjected to extreme impact loads due to the use of large-diameter steel balls and high linear velocities. This leads to increased cracking risks and reduced service life of the lining plates. This study focuses on the structural evolution and performance optimization of shell lining plates in an φ11 m semi-autogenous grinding (SAG) mill at a copper mine. Key findings indicate that enhancing the lining plate lifespan primarily depends on structural design improvements and increased metal volume. Optimizing the lifting face angle significantly improves metal utilization, reduces fracture probability, and enhances mill efficiency during initial operation.
1. Introduction
Semi-autogenous grinding (SAG) mills are critical equipment in mineral processing plants, offering high ore throughput and cost efficiency. The lining plate, a core component, protects the mill body and lifts ore for grinding. However, under high-impact conditions, traditional lining plates often suffer from premature failure, including cracking and deformation, which disrupts opesemi-autogenous grinding (SAG) mills, emphasizing material efficiency and durability.
2. Methodology
2.1 Mill and Process Parameters
The φ11 m × 5.4 m semi-autogenous grinding (SAG) mill processes 45,000 t/d of copper ore. Key operational parameters are summarized in Table 1.
Table 1: Process Parameters of the Semi-Autogenous Grinding (SAG) Mill
| Parameter | Value |
|---|---|
| Mill speed (r/min) | 9.75 |
| Feed size (mm) | 70–80 |
| Product size (mm) | 8–12 |
| Steel ball diameter (mm) | 120–150 |
| Ball filling rate (%) | 11 |
Ore properties, including hardness and grindability, are listed in Table 2.
Table 2: Ore Property Parameters
| Parameter | Value Range |
|---|---|
| True density (t/m³) | 2.76 |
| Hardness coefficient (f) | 6–10 |
| JK Drop Weight Test (A×b) | 46.31–55.51 |
| Bond Ball Mill Work Index (kWh/m³) | 13.27–15.60 |
2.2 Structural Evolution of Lining Plates
Three structural designs were evaluated:
- Symmetric Design (Baseline)
- Lifting face angle: 28°
- Base plate thickness: 80 mm
- Lifting bar height: 290 mm (effective height = 210 mm)
- Issue: Insufficient lifting bar height (1.4× steel ball diameter) led to frequent cracking.
- Asymmetric Design (Optimized)
- Lifting face angle: 30° (non-lifting side: 15°)
- Base plate thickness: 110 mm (lifting side), 90 mm (non-lifting side)
- Lifting bar height: 340–350 mm (effective height = 1.92–2.00× steel ball diameter)
- Advantage: Reduced direct impact on plates and improved metal utilization.
- Variable-Angle Design (Advanced)
- Axially varying lifting angles (optimized for wear zones)
- Localized height adjustments for high-wear regions.
3. Results and Discussion
3.1 Impact of Lifting Face Angle
Increasing the lifting face angle from 28° to 30° shifted the steel ball trajectory, reducing direct impacts on the lining plate. Fracture rates dropped by 40%, and throughput increased from 200 Mt to 280–300 Mt.
3.2 Metal Utilization and Wear Analysis
3D scanning revealed uneven wear patterns. Central zones exhibited 20–30% higher wear rates, prompting localized structural reinforcements.
3.3 Performance Metrics
Key outcomes of structural optimizations are compared below:
Table 3: Performance Comparison of Lining Plate Designs
| Design | Throughput (Mt) | Fracture Rate (%) | Service Life (months) |
|---|---|---|---|
| Symmetric | 200 | 35 | 3–4 |
| Asymmetric | 280–300 | 21 | 5–6 |
| Variable-Angle | 349 | 12 | 7–8 |
4. Mathematical Model for Wear Rate
The wear rate (WW) of lining plates can be approximated by:W=k⋅(F⋅v2H)W=k⋅(HF⋅v2)
Where:
- kk: Material constant
- FF: Impact force (kN)
- vv: Linear velocity (m/s)
- HH: Hardness of lining plate (HB)
This model highlights the importance of optimizing HH (via material selection) and reducing FF (via structural design).
5. Conclusion
- Lining plate lifespan improves with structural enhancements and increased metal volume.
- Asymmetric designs reduce fracture rates by 40% while maintaining metal efficiency.
- Variable-angle configurations extend service life to 7–8 months, achieving a throughput of 349 Mt.
- 3D wear analysis enables targeted optimizations for high-stress zones.
Future work will focus on advanced materials (e.g., nano-structured alloys) to further enhance lining plate performance.