Material build-up and coating (especially for fine powders like calcium carbonate) are mainly caused by low airflow, moisture, static electricity, rough surfaces, dead zones, and unstable operation. Below are targeted, industrial-grade prevention solutions:
1. Optimize Duct & Cyclone Design
- Maintain sufficient conveying velocityKeep airspeed in ducts above the minimum saltation velocity (typically 18–28 m/s for fine mineral powders) to avoid particle settling. For cyclones, match inlet velocity to prevent low-speed recirculation zones.
- Eliminate dead cornersUse rounded transitions instead of sharp angles, reduce sudden expansions/contractions, and avoid long horizontal duct sections.
- Standardize cyclone geometryUse proper tangential inlets, reasonable cone angles, and smooth discharge outlets to avoid eddies and material retention.
2. Improve Surface Anti-Adhesion Performance
- Apply low-friction coatingsUse PTFE, polyurethane, or ceramic coatings on inner walls to reduce particle adhesion.
- Anti-static treatmentGround metal ducts/cyclones and use antistatic liners to prevent fine powder from sticking due to static charge.
- Use polished or smooth linersPolished stainless steel or smooth composite liners prevent powder from anchoring to rough surfaces.
3. Stabilize Operating Parameters
- Control moisture strictlyHigh humidity is the main cause of caking and coating. Keep material moisture below 0.5% (for CaCO₃ and similar minerals) and avoid condensation in cold duct sections.
- Stable air volume & pressureAvoid large fluctuations in fan speed or system pressure, which cause uneven flow and deposition.
- Uniform feedingPrevent overloading or intermittent feeding, which leads to local material accumulation.
4. Install Automatic Cleaning Devices
- Air cannons / air blastersInstall at elbows, hoppers, and cyclone cone sections for timed high-pressure purging.
- Pneumatic knockers or vibratorsMount on outer walls to shake off weakly adhered powder layers.
- Sonic horns / acoustic cleanersSuitable for fine powder systems to loosen coatings without damaging equipment.
- Internal scrapersInstall rotating or pneumatic scrapers for severe adhesion conditions.
5. Adjust Material & Process Conditions
- Add flow aids or anti-caking agentsUse small amounts of anti-caking additives for hygroscopic or ultra-fine powders.
- Optimize particle sizeReduce excessive ultra-fine content, as fine particles are more likely to coat surfaces.
- Insulate cold sectionsPrevent wall condensation that causes wet adhesion and hard scaling.
6. Regular Maintenance
- Purge ducts completely during shutdowns.
- Conduct periodic inspections to remove early-stage build-up before it hardens.
- Clean and recondition coated surfaces to restore smoothness.
