Page 30 - dust collection systems

that woven fabrics used with pulse jet filters leak a great deal
of dust after they are cleaned.

An off-line pulse jet bag filter is used when the dust in the gas

is very light and/or fine. The dust may remain in suspended

condition because the upward/reverse gas flow will not allow

the dust to settle in the hopper. This phenomenon is called

fluidization of dust. The fluidization of dust results in high

differential pressure across the bag filter, and ultimately

choking of bags.

When bags are cleaned on-line, the order in which the bag

rows are cleaned is very important. If bag rows are cleaned in

a sequential order, material from one row of filter bags

simply gets moved to the row previously cleaned. This not

only results in poor cleaning but tends to retain very fine

particles on the filter bags and can lead to premature

blinding. Cleaning in a random or non-sequential order

distances rows from each other and greatly reduces both

reentrainment and potential premature blinding of bags.

Typically bag life in a pulse jet filter is 3 to 6 years.

In case of traditional pulse jet system with venturis, there is

clearly a limit to the length of filter bag that can be