A: Dwayne Sanders, Sly, says:
When handling dust and particulate, it’s imperative to mitigate the risk of a dust explosion as much as possible. Dust explosions can pose a major threat to the safety of your facility, and failing to prepare properly for them can land you in regulatory trouble.
This isn’t a niche issue because many processes can create combustible dust. According to the National Fire Protection Association (NFPA), combustible dust is defined as solid material that’s composed of distinct particles or fragments smaller than 500 microns that are a fire hazard when suspended in an oxidizing medium, such as air. Many solid, noncombustible materials can create combustible dusts during manufacturing processes, including food preparation (grinding or mixing), machining (sawing or drilling), and finishing (buffing, polishing, or abrasive blasting). Examples of common combustible dusts include everything from powdered milk and flours to metallic or chemical dusts.
Combustible dust becomes a problem when that “fuel” encounters certain conditions, such as adequate dust dispersion, free oxygen, enclosed spaces, and an ignition source. Even just a spark from friction or static electricity can create a dust explosion in the confined quarters of a dust collection system baghouse.
To help prevent dust explosions across industrial applications, the NFPA has recently mandated that applicable facilities perform a dust hazards analysis (DHA) with updates every 5 years. This analysis will identify any possible dust explosion risks throughout your processes, allowing you to modify your dust collection equipment accordingly.
If you have a baghouse or dry dust collector, there are steps you can take to create an explosion-proof air quality control system. One step is to equip your baghouse or cartridge filter collector with explosion venting, which exhausts flames and relieves the pressure buildup commonly associated with a dust explosion. For more active risk mitigation, consider using a chemical suppression system. Other solutions include flameless venting or quench tubes, grounded filter bags, and electrical enclosures.
A wet scrubber is a useful option to handle combustible dust. Instead of using filters or cartridges, wet scrubbers use a scrubbing fluid to remove pollutants from the airstreams. The wet scrubber method inherently mitigates the risk of an explosion by removing heat sources and friction, reducing dust dispersion, and preventing direct contact between the dust and free oxygen. Without these risk factors, dust explosions are nearly impossible within the scrubber itself.
Whether you’re using a baghouse or a wet scrubber, you’ll still need to consider your system’s upstream and downstream processes in relation to the dust collector. For updated regulations on using baghouses and dry dust collectors to handle combustible dust, refer to NFPA 652: Standard on the Fundamentals of Combustible Dust. If you plan to use a wet scrubber, refer to NFPA 484: Standard for Combustible Metals for more detailed information.
Sly, Strongsville, OH, manufactures and supplies air pollution control systems, including dust collectors, scrubbers, and related equipment.