A fabric filter is also known as a dust collector. The current technology utilizes compressed air to pulse the filter bags or cartridges clean. These are relatively low pressure drop devices and can meet most emission standards. The typical unit uses compressed air to clean the filters, but there is comparable technology available that uses low-pressure air from a positive displacement blower to clean the filters. An older technology still available is the reverse air unit that backflow’s the unit with airflow to push the particles off the filter.
There are several filter medias available, with the most popular bag material being felted polyester. For higher temperature and more aggressive applications, there are fabrics such as aramid (NOMEX), P 84, polypropylene, Ryton and available with PTFE membrane coatings. There are also cartridge filters available using polyester spun bonded fibers, nanofiber media, cellulose and paper combinations, and with options to apply a PTFE membrane or flame retardant coatings.
Cyclones are another way to remove particulate from an airstream as a low maintenance device. The removal efficiency of a cyclone can come close to a fabric filter dust collector, depending on particle size, particle geometry and specific gravity. Cyclone efficiency is related to the cyclone geometry as well as the static pressure through the cyclone. Typically the higher the static pressure, the more efficient a cyclone can be. However, by breaking a cyclone into multiple parallel cyclones, an application can run at a higher efficiency with lower static pressure requirements. Another advantage of cyclone technology is the higher temperature capability. Whereas a fabric filter is limited to 500-550°F, a cyclone can operate at temperatures of 800-1000°F.