Engineering

Coal in Dust Collection System Design and Dust Collector Manufacturing

Coal, being an explosive dust, must be handled with great care. An accumulation of as little as 1/32″ is enough to cause an area to be classified as hazardous, according to the National Electric Code. As a layer of coal dust thickens, the potential for self-heating and auto-ignition increases.

Critical Safety Requirement: Good housekeeping is essential. All areas in the vicinity must be kept clean, particularly checking ledges and flat roofs. No dust should be allowed to accumulate on hot surfaces, such as electric motors, to prevent self-heating to the ignition temperature.

Power Plant Dust Collection

In a power plant, areas where coal fines are produced, such as at the crushing station, are typically equipped with exhaust hoods and ductwork to convey the fugitive dust to a central dust collector. This dust collector should be fitted with explosion relief vents, designed and sized according to the rules of NFPA-68.

Equally important is to take as many precautions as reasonably possible to prevent an explosion from happening in the first place. The following measures should be implemented with a collector handling coal fines:

Use Grounded Filter Bags

Filter bags can accumulate static electricity, which, if not discharged, can be a source of ignition.

  • Basic solution: Bags with stainless steel ground wires attached to tubesheet studs
  • Intermediate solution: Epitropic bags embedded with conductive carbon fibers
  • High hazard solution: Bags with 5% stainless steel fibers for maximum conductivity

Prevent Build-up in Hoppers and on Surfaces

  • Ensure rotary valve is well-maintained, lubricated, and removes dust efficiently
  • Install level detectors on hoppers to sound alarms for high dust accumulation
  • Implement regular inspection and cleaning schedules

Control Sources of Ignition

  • Eliminate open flames from welding/burning operations near coal dust
  • Prevent sparks from grinding operations
  • Use non-sparking materials in rotating equipment
  • Remove hard objects and impurities from coal feed to prevent friction

Avoid Over-cleaning Filter Bags

  • Over-cleaning creates explosive dust clouds
  • Removes protective dust cake that provides filtration efficiency
  • Causes "puffing" - coal dust escaping immediately after cleaning
  • Maintain stable differential pressure of 2″ to 4″ W.G.

Check Ducts and Hoods

  • Maintain minimum conveying velocity of 4500 ft/min (NFPA-120)
  • Hoods should have four times the area of the duct
  • Use a minimal number of hoods for efficiency
  • Adjust dampers or hood elevation if fugitive dust isn't properly conveyed
  • Consult ASHRAE guidelines for complex ducting systems

BCE Safety Engineering: Our coal handling dust collection systems incorporate multiple layers of protection, including proper grounding, explosion venting, monitoring systems, and comprehensive safety protocols to ensure compliance with NFPA standards and protect your facility from coal dust explosion hazards.