Effects of Filtering Velocity and Dust Concentration on Pressure Drop Parameters in a Bag Filter

Abstract

The effects of filtering velocity u and dust concentration c on pressure drop parameters, i.e., specific resistance of dust cake α and specific resistance of filter cloth with residual dust ζ_d, were examined for three kinds of dust in a bag filter.
The measured specific resistance α for a dust cake with a void fraction larger than 0.5 was almost proportional to the 1/2 power of the filtering velocity and to the −1/3 power of the dust concentration. Comparing the model equation of the filter cloth with dust to the Kozeny-Carman equation, the value of (1−ε)/ε³was obtained from the measured value of α and correlated empirically with the operating conditions and the physical properties of dust. The resultant correlation gave rise to the following correlation of α,
α=1.15×10¹¹(D_v/D_s)³D_v^-3/4ρ_s^-2/3c^-1/3u^1/2μ^1/2
The estimated values of α from the correlation coincided well with the measured ones within the experimental error of ±25%.
The measured specific resistance of filter cloth with residual dust ζ_d was almost independent of the filtering velocity and the dust concentration.
The dependency of α on the variation of the filtering velocity u with time during a filtering operation in a multi-compartment bag filter gave a slightly larger value of the pressure drop than that at the constant value of α through the operation, but did not affect the time-dependent behavior of the pressure drop.