PARTICULATE REMOVAL 833
approach can be based on the normalized grade efficiency
curve shown in Figure 3. A survey of many experiments on
efficiency 21 – 23 indicates that most cyclone grade efficiency
curves have approximately the same shape. Using the theo-
retical basis for calculating critical particle diameter but intro-
ducing an empirical constant, one can calculate , the particle
diameter at which collection efficiency is 50% at standard
dust loading:dWD(^50) U 2
°= 116 .,
m
r t
(1)
where
m gas viscosity
W cyclone inlet width
D cyclone barrel diameter
r particle density
U gas velocity at inlet
t average gas residence time.
Gas residence time is given by
t
V
hWU
= ,
where
V cyclone volume
h cyclone inlet height.
The above equation is applicable at dust concentrations
of about 5 grains/ft^3 which is a standard concentration for
99.9
99.8
99.5
99
98
95
90
80
70
60
50
40
30
20
10
(^110100)
PARTICLE DIAMETER, MICRONS
COLLECTION EFFICIENCY, %
1817
16
15 14
13
12
11
10
9
8
7
5
6
(^43)
21
1 Settling Chamber
2 Medium Eff.Cyclone
3 Cellular Cyclone
4 High Eff. Cyclone
5 Jet Impingement Scrubber
6 Moving Impeller Cyclone
7 Self Induced Spray Cleaner
8 Wet Cyclone
9 Spray Tower
10 Fluid Bed Scrubber
11 Electrostatic Precipitator
12 Irrigated Target Scrubber
13 Disintegrator
14 Irrigated Electrostatic Precipitator
15 Low Energy Annular Throat Scrubber
16 Medium Energy Annular Throat Or
Venturi Scrubber
17 High Energy Venturi Scrubber
18 Fabric Filter
FIGURE 1 Typical grade efficiency curves.
C016_002_r03.indd 833C016_002_r03.indd 833 11/18/2005 1:06:45 PM11/18/2005 1:06:45 P