Fabric Filtration: An Overview of Baghouse Contaminant Removal
The baghouse uses fabric material to deposit the particles and can collect small micrometer and sub-micrometer particles due to the accumulated dust cake. This article will delve deeper into how a baghouse removes contaminants and the different methods of cleaning the filter material.
Types of Fabric Filters:
There are three types of fabric filters, each of which differs in the method used to clean the filter material: shaker fabric filter collectors, reverse air fabric filter collectors, and reverse pulse or pulse jet collectors.
Shaker Fabric Filter Collectors:
Shaker fabric filter collectors use a tube sheet between the vertical casing and the hopper. The contaminated gas stream flows through the holes in the tube sheet and into the inside of the vertical bags, leaving a dust cake on the inside. Periodically, the gas flow through the collector is stopped, and the bags are gently shaken to clean them, with the dislodged dust cake falling into the hopper and removed from the collector.
Reverse Air Fabric Filter Collectors:
Similar to shaker collectors, reverse air fabric filter collectors have a tube sheet between the casing and the hopper. However, the closed tops of the bags are attached to a support structure in the top of the casing, and the bags are held under tension. The contaminated gas stream flows into and through the bags, leaving a dust cake on the inside. Cleaning is accomplished by introducing another gas flow that flows in the reverse direction, with rigid rings sewn into the bags to keep them from fully collapsing during the reverse airflow. The dust cake dislodged by the reverse airflow falls into the hopper and is removed from the collector.
Reverse Pulse or Pulse Jet Collectors:
Reverse pulse or pulse jet collectors use compressed air pulses to clean the bags. The bags hang from holes in the tube sheet, with a wire-mesh cage located inside to keep them from collapsing. The contaminated gas stream flows into the bags and up through the tube sheet, leaving the dust cake on the outside of the bags. Cleaning is accomplished by directing the compressed air pulse to one or a few rows of bags, while the other bags continue to provide filtration. The collector is not shut down or isolated from flow during cleaning, and the dust cake dislodged by the compressed air pulse falls into the hopper and is removed from the collector.
Conclusion:
Fabric filters, or baghouses, are an effective method for removing contaminants from gas streams. They use fabric material to deposit the particles, and the accumulated dust cake can collect small micrometer and sub-micrometer particles. There are three types of fabric filters: shaker fabric filter collectors, reverse air fabric filter collectors, and reverse pulse or pulse jet collectors. Each type differs in the method used to clean the filter material, but all ensure high collection efficiencies greater than 99 percent.