Dust Control Handbook for Industrial Minerals Mining and Processing

Reverse Air CollectorsReverse air collectors use a traveling manifold to distribute low-pressure cleaning air (3–7 psig)to the filter bags for reconditioning. They have no compressed air requirements and involve nofreezing of air lines. On the negative side, they have larger footprints than conventionalcollectors and maintaining their cleaning mechanisms is difficult. They also perform poorly incorrosive environments.Reverse air collectors employ tubular bags fastened onto a cell plate on the bottom andsuspended from the top of the collector. The collectors must be compartmentalized forcontinuous service. Dust-laden air enters the collector and deposits dust on the outside of thebags. 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 tonormal airflow. This causes the bags to partially collapse and release the dust cake. The bagshave rings located at various intervals to prevent total collapse so that the dust cake can escapeand fall into the hopper (Figure 1.18).Reverse air collectors were originally developed primarily with fragile glass cloth for use inhigh-temperature operations. These collectors have declined in popularity with the use of newmaterials that can withstand high temperatures and greater physical action. Air to cloth ratios forreverse air collectors are similar to those for shakers due to the low bag cleaning efficiency of thereverse air.Figure 1.18. Typical design of a reverse air dust collector.36 Fundamentals of Dust Collection Systems