1. Selecting the Ideal Filtration Velocity (Air-to-Cloth Ratio)
Filtration velocity should be dynamically balanced based on dust concentration and particle size:
- Dust Concentration & Size: High dust concentrations and finer particle sizes require lower filtration velocities to prevent premature clogging. Conversely, coarser particles and lower concentrations allow for higher velocities.
- Velocity Risks:
- Too High: Overloads the filter bags, escalates differential pressure (resistance), accelerates mechanical wear, and reduces collection efficiency.
- Too Low: Mandates a larger filtration area, unnecessarily inflating the physical footprint and capital cost of the dust collector.
2. Pre-Coating to Prevent Oil Adhesion
During boiler startup or low-load operations, fuel oil is often injected for extended periods. Unfiltered oil mist will cause irreversible blinding of the filter bags. To prevent this, a pre-coating process must be implemented:
- Application: Inject lime powder or fly ash to form a protective barrier on the bags before oil introduction.
- Verification: Pre-coating is considered successful when the differential pressure across the bags increases by 250 to 300 Pa.
- Inspection: Visually confirm even dust distribution by opening the clean air chamber access covers.
3. Optimizing Pulse Pressure and Pulse Width
Pulse-jet cleaning parameters must be carefully calibrated to avoid excessive mechanical stress on the fabric:
- New Filter Bags: Maintain a lower pulsing pressure of 0.20 to 0.25 MPa to protect the fresh media.
- Aged Filter Bags: As operational runtime increases and residual dust buildup elevates baseline resistance, gradually increase the pulsing pressure up to 0.35 MPa to maintain effective cleaning efficiency.
4. Managing Exhaust Gas Temperature
Strictly monitor and control flue gas temperatures to prevent thermal degradation or moisture condensation:
- High-Temperature Risks: Sudden temperature spikes or prolonged exposure to excessive heat will scorch or melt the filter bags.
- Low-Temperature Risks: Operating below the acid or moisture dew point causes condensation, leading to mud-coating, bag hardening, and chemical blinding. Both extremes cause irreversible damage and drastically shorten filter bag life.
5. Standard Operating Procedures for Shutdown & Maintenance
Proactive lifecycle management during shutdowns is critical to preserving bag integrity:
- Pre-Shutdown Cleaning: Before turning off the system, run the pulse-jet cleaning system through several offline cycles to minimize residual dust on the bags. Ensure all collected ash in the hoppers is completely evacuated to the storage silos.
- Winterization & Insulation: In cold climates, ensure the dust collector is thoroughly insulated. Regularly inspect the housing for air leaks, and utilize auxiliary heating devices where applicable to keep the internal environment dry and prevent moisture damage.