Dry grinding of quartz sand (using vertical roller mill, ball mill or Raymond mill) generates heat from particle collision, friction between grinding media and liners, and mechanical energy conversion. Quartz has low thermal conductivity, so heat accumulates easily inside the mill. Excessively high temperature causes multiple issues: powder agglomeration, product PSD shift, accelerated wear of liners/media, thermal stress cracking of ceramic liners, and even dust explosion risks for fine quartz powder. This article introduces practical temperature control methods for dry quartz grinding lines for quartz-mill.com.
1. Main Sources of Heat in Dry Quartz Grinding
- Frictional heat from grinding action between quartz particles and wear parts
- Impact energy converted into heat during particle breakage
- Heat from the main motor, reducer and fan
- Compression heat from circulating air inside the closed grinding circuit
For quartz, harder grinding to finer mesh (200 mesh and below) will sharply increase heat generation.
2. Target Temperature Range
- Recommended mill outlet temperature: 70–95°C
- Upper limit: ≤110°C for standard alloy wear parts
- For ceramic liners / ceramic media: keep below 90°C to avoid thermal shock and cracking
If temperature exceeds 120°C, immediate adjustment is required.
3. Primary Temperature Control Methods
3.1 Cold Air Inlet Regulation (Most common method)
Adjust the volume and temperature of inlet process air to take away grinding heat.
- Increase cold ambient air intake to enhance heat removal when mill temperature rises.
- Reduce hot air supply: In VRM, hot air is normally for drying raw quartz. If feed moisture is already low (<1.5%), cut or stop hot air supply and use full cold air circulation.
- Maintain proper air velocity: airflow not only transports powder but also acts as the cooling medium. Too low air volume reduces heat dissipation.
Note: Do not add excessive cold air suddenly; rapid temperature change creates thermal shock for ceramic liners.
3.2 Stabilize Feed Rate and Reduce Over-Grinding
Over-grinding greatly increases heat output.
- Maintain continuous, stable feed. Underfeeding causes media-to-liner direct contact and spikes friction heat.
- Avoid over-grinding: tune classifier speed to prevent excessive re-circulation of fine particles back into the grinding zone. Repeated regrinding accumulates heat.
- Keep feed moisture at 0.5–1.5%. Minor surface moisture can slightly buffer friction heat; completely bone-dry quartz generates more friction heat. Do not exceed 2% moisture, otherwise powder agglomeration will occur.
3.3 Optimize Mill Operating Parameters
Vertical Roller Mill (VRM)
- Reduce excessive hydraulic roller pressure: higher pressure creates more bed friction and heat. Use the minimum pressure that meets target fineness.
- Maintain stable material bed thickness (20–40 mm). A too-thin bed causes metal contact and rapid heat rise.
Dry Ball Mill
- Lower mill speed slightly if temperature keeps rising, reduce violent impact friction.
- Optimize media filling rate and gradation: avoid excess small balls which increase particle collision and heat generation.
3.4 Auxiliary Cooling Systems for High Heat Load
For large-capacity dry circuits or fine powder (200 mesh+) production:
- Air cooler on inlet air: Install air heat exchanger to cool incoming process air in high-temperature seasons.
- Water jacket cooling: Water cooling jacket on mill cylinder/reducer, widely used on dry ball mills. Use circulating low-temperature soft water, strictly prevent water leakage into grinding chamber (water will cause quartz powder agglomeration).
- Reducer oil cooling: Maintain oil cooling system to control reducer temperature; high reducer oil temperature transfers heat into mill body.
4. Material & Wear Part Considerations
- Alloy metal liners and rollers can tolerate higher temperature, but high temperature accelerates abrasion and oxidation wear.
- Ceramic liners and ceramic media are sensitive to rapid temperature fluctuation. Avoid sudden cold air blast when mill is hot.
- Regularly inspect worn liners: worn profiles create unstable grinding and local hot spots.
5. Safety & Quality Side Effects of High Temperature
- Fine quartz powder agglomerates; agglomerated particles pass classifier and cause unstable PSD.
- Residual stress on liners increases risk of cracking.
- For dust collection: high air temperature reduces bag filter service life. Select high-temperature filter bags if outlet air >90°C.
- Dust explosion risk: high temperature raises ignition risk of fine silica dust; maintain proper inert protection if producing ultra-fine quartz powder.
6. Troubleshooting Table
| Symptom | Root Cause | Solution |
|---|---|---|
| Mill outlet temperature continuously over 110°C | Insufficient cooling air, too high grinding pressure, underfeeding | Increase cold air intake; reduce roller/grinding pressure; stabilize feed rate |
| Temperature fluctuates sharply | Unstable feed, sudden hot/cold air adjustment | Keep steady feed; adjust air volume slowly |
| Powder agglomeration with high temp | Local overheating + trace moisture | Reduce mill temperature; control feed moisture |
| Ceramic liner cracking | Thermal shock from sudden cold air | Gradually adjust inlet air; limit temperature change rate |
Temperature control for dry quartz grinding mainly relies on regulating process cold air, stabilizing feed and avoiding over-grinding. Keep mill outlet temperature between 70–95°C, below 110°C for alloy components and below 90°C for ceramic liners. Reduce grinding pressure and circulating load to cut heat generation. Add water jacket or air cooler for large high-fineness production lines. Always avoid rapid temperature variation to protect non-metallic wear parts and maintain stable quartz powder quality.
