FILTRATION OF DUST-AND-GAS FLOWS
IN THE PRODUCTION OF BUILDING MATERIALS
S. V. Éntin,
N. M. Anzheurov,
Yu. V. Krasovitskii,
and S. Yu. Panov
Translated from Ogneupory i Tekhnicheskaya Keramika, No. 5, pp. 35 – 36, May, 2002.
The typical mass concentration of dust in the waste pro
cess gases or particulate emissions in the industry of building
materials is z
. The filtration of aerosols results in
the deposition of a dust layer on the surface of the filtering
material, which causes an increase in the hydraulic resistance
of the filter (assuming the filtration rate to be constant) .
Industrial dust filtration at high dust concentrations and
the efficiency of different mechanisms of deposition were
explored using diagrams showing the hydraulic resistance of
a ceramic metal filter and the dust breakthrough (evaluated
by counting the particle concentration) as a function of time.
They are given in Fig. 1. By convention, the process of filtra-
tion can be divided into stages I, II, and III.
At stage I, the filtration is granular in character and in-
volves a relatively high dust breakthrough and an insignifi-
cant increase in hydraulic resistance. In this stage, the dust-
collection efficiency is determined by the combined action of
three mechanisms: tangential, diffusional, and inertial .
This stage is of short duration: individual dust particles
become deposited on the grains to form branchings.
At stage II, an elementary filtering layer builds up. The
branchings of deposited particles join up to form a filtering
membrane on the surface of the granular bed that constitutes
the base of a dust bed, thus providing a high degree of arrest
ing of the finely dispersed dust.
The hydraulic resistance of filtration increases with de
crease in the free pore cross section of the filtering layer; the
breakthrough ratio decreases sharply. In this stage, the entan
glement effect comes into play. It was shown in [3, 4] that af
ter the first layer has deposited on the filter, the rough surface
thus formed develops increasingly adhesion sites, which pro
vides a better cohesion between dust particles and the surface.
The termination of stage II is difficult to establish; still,
the available experimental data show that the filtering layer
builds up completely after a dust layer of thickness
0.3 – 0.5 mm has deposited on the surface of the filter.
The duration of stage II is chiefly determined by the
mass concentration, dust dispersivity, and filtering rate.
At stage III, the “nonstationary” filtration through the
earlier formed dust self-filter layer occurs, which results in
further increase of the dust-layer thickness and, correspond
ingly, in a linear increase of hydraulic resistance at the virtu
ally constant dust breakthrough ratio. This constancy of
breakthrough ratio is due to the steady removal of particles
from the dust basis of the filtering layer and to the co-current
processes of particle redistribution within the layer.
One would expect that further increase in the dust-layer
thickness must result in a sharp decrease in the breakthrough
ratio and in an increase in the filtration efficiency; however,
these effects have never been observed in reality.
Our experience gained at the environmental control labo-
ratory of the Semiluki Plant for Refractory Materials lends
support to that observation. First, a uniform layer of the
model dust was deposited on a ceramic metal filter
=10mm, log s = 1.3); next, filtration was carried out on
Refractories and Industrial Ceramics Vol. 43, Nos.5–6, 2002
1083-4877/02/0506-0193$27.00 © 2002 Plenum Publishing Corporation
Semiluki Plant for Refractory Materials, Voronezh Region, Rus
sia; Voronezh State Technological Academy, Voronezh, Russia.
I II III
Filtration time , mint
Breakthrough ratio, 10´
Pressure drop , PaDP
Fig. 1. Hydraulic resistance of dust arresting (curve 1 ) and the
breakthrough ratio (curve 2 ) plotted as a function of the filtration
time (dust parameters: d
=10mm; log s = 0.6; z = 1.5 g/m
× min), where d
is the average median diameter for
dust particles and s is the standard deviation).