For mineral closed grinding systems (CaCO₃, graphite, etc.), process gas is reused via a closed-loop circulation system to save energy, lower emissions and stabilize grinding conditions.
1. Typical Closed-Loop Flow
Mill → Classifier → Dust removal → Cooling / heat recovery → Circulation fan → Back to mill
2. Key Processes & Equipment
- Full Enclosure & Gas CollectionUse sealed ducts, mills and collectors to capture all exhaust gas with almost no leakage.
- Dust Purification (essential)
- Primary: Cyclone (separate coarse particles)
- Secondary: Baghouse / pulse filter (remove fine dust)Only clean gas can be stably recycled.
- Temperature & Heat ManagementInstall a heat exchanger to:
- Cool recycled gas (avoid overheating product/equipment)
- Recover waste heat for preheating raw material.
- Gas RecirculationA high-efficiency centrifugal fan maintains flow and pressure.Typical recirculation rate: 85–95%.
- Atmosphere & Makeup Gas
- Small makeup gas (air or N₂ for inert conditions) compensates leakage.
- For combustible powders (e.g., graphite), monitor and control O₂ level for safety.
3. Advantages
- Fan energy consumption reduced by 30–50%
- Near-zero dust emission
- Stable grinding atmosphere (temperature, humidity, oxygen)
- Lower operating cost
4. Operation Notes
- Keep slight positive pressure to reduce outside air intrusion.
- Regularly clean filters to avoid high pressure drop.
- Automate monitoring of O₂, temperature and flow.