After new filter bags and cages have been installed, a meticulous startup procedure is essential to ensure optimal performance, prevent damage to the new media, and maintain compliance. Follow these steps carefully:
1. Prepare Dust Removal System
- Ensure the dust collection hoppers are empty.
- Verify that the dust discharge device (rotary airlock, screw conveyor, etc.) is operational and ready to receive collected dust. This system should be started before the main fan.
- Start Dust Discharge Systems: Activate the rotary airlock, screw conveyor, or other dust removal equipment at the bottom of the hoppers. This ensures that any dust collected during startup is immediately discharged and does not accumulate in the hoppers, which can lead to blinding or re-entrainment.
2. Disable Cleaning System:
Ensure the automatic bag cleaning system (pulse-jet, shaker, reverse-air) is OFF or in manual mode and not actively cycling. This is vital for the pre-coating process.
3. Preheat Baghouse (for High-Temperature Applications)
The typical preheat procedure of a baghouse is designed to bring the entire system, including filter bags, housing, and internal metalwork, above the acid dew point and moisture condensation temperature before introducing process gas. This prevents moisture condensation on the new, cool bags, which can lead to blinding by sticky dust or corrosion. No process dust should be introduced until this temperature is achieved.
Preheating methods include:
- Warm & Dry Air Circulation
- Start the main exhaust fan.
- Use a dedicated ambient air inlet damper (or a dedicated preheating air intake damper) to draw in warm, dry ambient air. If ambient air is cold or humid, consider using an auxiliary heater (see next point) or a dehumidifier to condition the air before it enters the baghouse.
- Ensure the main process gas inlet damper to the baghouse remains fully closed during this step.
- Gradually increase the air volume and temperature.
- Auxiliary Heater: If the baghouse system is equipped with a dedicated auxiliary heater (e.g., natural gas burner, electric heater), activate it to slowly raise the internal temperature of the baghouse. This is often the most reliable way to ensure warm and dry air.
- Hot Gas Recirculation: If the system has a recirculation loop, hot and clean air from downstream of the fan can be recirculated back to the baghouse inlet to raise its temperature gradually.
Monitoring during preheating:
- Continuously monitor the internal baghouse temperature using installed thermocouples or temperature gauges.
- Ensure the temperature rises slowly and evenly to prevent thermal stress on the bags and housing. A typical ramp rate might be 5-10°F per minute, but this can vary based on baghouse size and material.
- The target temperature should be at least 20-50°F above the dew point of the gas stream. Ideally, bring it up to near the normal operating temperature before introducing any dust.
The preheating duration will depend on the size of the baghouse, the ambient temperature, and the desired operating temperature. It could range from a few minutes to several hours.