The report gives results of a pilot-scale study of pulse-jet filter cleaning, a process that is ineffective to the extent that collected dust redeposits, rather than falling to the hopper. Dust tracer techniques were used to measure the amount of redeposition. A mathematical model based on experimental results was developed to describe dust transfer from bag to bag, redeposition on the pulsed bag, and migration to the hopper. At conventional filtration velocities (5 cm/s), most of the dust freed from the bag by the cleaning pulse was found to redeposit (38% on the cleaned bag and 50% on the two neighboring bags) rather than fall to the hopper. At high velocities (15 cm/s), redeposition was more pronounced, 83% on the cleaned bag and 16% on the neighboring bags. At a sufficiently high velocity, redeposition may become total: no dust will fall into the hopper, the dust cake will continue increasing in thickness, and the pressure drop will increase without limit as long as constant velocity is maintained. The study indicates that reasonable pressure drop can be achieved at high velocity only when there is a reduction in filter cake redeposition. Although filter performance depends on more parameters than were examined, the trend of increasing redeposition with increasing velocity may persist regardless of the dust, fabric, or filter configuration.

Grant no. R801399, program element no. EHE624. Issued Mar. 1977. Includes bibliographical references (p. 27).