Performance of a High Velocity Pulse Jet Filter in a Wool Carbonizing Process

Abstract

Experiments on a high velocity pulse jet filter used to control emissions from a wool carbonizing process have shown that it is necessary to use filter cloths with a surface skin to prevent premature blinding of the fabric. The skin partially prevents dust and wool fiber from penetrating into the depth of the fabric and, subsequently, the dust is more easily dislodged during cleaning. Although both Goretex® and a calendered needlefelt have given satisfactory performance at a filtration velocity of 65 mm/s, there is a gradual increase in the resistance to airflow through the fabrics with time. This is due to the accumulation of dust on the fabric, which is not removed by the normal cleaning pulse. After eight months service, 56% of the resistance of the Goretex cloth was due to dust that was not dislodged from the fabric during cleaning, 38% to dust which was dislodged during cleaning but immediately redeposited on the bag, and 6% to dust added during the filtration cycle and cleaned from the fabric by the cleaning pulse. The efficiency of the cleaning process can be improved by cleaning the filter off-line rather than the more normal on-line cleaning. Under these conditions the dust that is usually redeposited on the bag is allowed to reach the hopper.