Encyclopedia of Environmental Science and Engineering, Volume I and II

834 PARTICULATE REMOVAL

cyclone testing. Studies of the effect of loading on grade effi-

ciency have shown 24,25 that cyclone efficiency is very sen-

sitive to dust loadings, and for this reason a correction to

equation (1) is necessary for other concentrations:

d

D

L

L

50

50

°^02

=

°

⎛

⎝⎜

⎞

⎠⎟

.

, (2)

where the reference loading L  is 5 grains/ft^3. Using Eq. (2)

for d 50 , efficiency for other particle diameters d can be found

from Figure 3.

Equation (1) can give directional effects for many geo-

metric changes in design; but if data are available on the actual

geometry of interest, it is much more satisfactory to use such

data to modify the numerical constant in the equation. It is

especially important to note that modifications to outlet pipe

diameter to not enter into Eq. (1), and the numerical constant

is for cyclones with normal ratios of outlet to inlet area of 1.3

to 1.5. For certain applications area ratios well below 1.0 are

now being offered. Such cyclones have higher pressure drop.

Unfortunately, suitable published data are not available on this

effect to permit quantitative prediction of effect on efficiency.

Although some reviews have compiled “consensus”

dimensions for cyclone design, quite a range of relative

dimensions exists within the bounds of good design practice.

Design is a compromise among efficiency, cyclone through-

put, and pressure drop, and improvement in one factor will

Clean Gas

Collected Dust

Dirty Gas

FIGURE 2 Conventional cyclone opera-

tion (The Ducon Co.).

99.9

99.8

99.5

99

98

95

90

80

70

60

50

40

30

20

10

5

2

1

0.5

0.2

0.1

0.1 0.2 0.5 0.8 1 2 5 8 10 20

RELATIVE PARTICLE SIZE,

COLLECTION EFFICIENCY, %

d

d 50

FIGURE 3 Generalized cyclone grade efficiency.

C016_002_r03.indd 834C016_002_r03.indd 834 11/18/2005 1:06:45 PM11/18/2005 1:06:45 P