Reverse air collectors use a traveling manifold to distribute low-pressure cleaning air—3–7 pounds-force per square inch gauge (psig)—to the filter bags for reconditioning. They have no compressed air requirements and involve no freezing of air lines. On the negative side, they have larger footprints than conventional collectors and maintaining their cleaning mechanisms is difficult. They also perform poorly in corrosive environments.
Reverse air collectors employ tubular bags fastened onto a cell plate on the bottom and suspended from the top of the collector. The collectors must be compartmentalized for continuous service. Dust-laden air enters the collector and deposits dust on the outside of the bags. Before a cleaning cycle begins, filtration in the compartment to be cleaned is suspended. Bags are cleaned by blowing low-pressure air into the compartment in the reverse direction to normal airflow. This causes the bags to partially collapse and release the dust cake. The bags have rings located at various intervals to prevent total collapse so that the dust cake can escape and fall into the hopper.
Reverse air collectors were originally developed primarily with fragile glass cloth for use in high-temperature operations. These collectors have declined in popularity with the use of new materials that can withstand high temperatures and greater physical action. Air to cloth ratios for reverse air collectors are similar to those for shakers due to the low bag cleaning efficiency of the reverse air.
Reference
NIOSH Mining Program Report of Investigations, « Dust Control Handbook for Industrial Minerals Mining and Processing», Second Edition
