Geoscience Reference
In-Depth Information
TABLE 17.5
Size Efficiency Table
d
p
(µm)
w
i
d
p
/[
d
p
]
cut
η
i
(%)
w
i
η
i
(%)
1
0.03
0.1
0
0
5
0.20
0.5
20
4
10
0.15
1
50
7.5
20
0.20
2
80
16
30
0.16
3
90
14.4
40
0.10
4
93
9.3
50
0.06
5
95
5.7
60
0.03
6
98
2.94
>60
0.07
—
100
7
(
)
×
05
.
−
4
90
×
.02
×
67210
.
×
2 5
.
9
µ
B
c
−
5
d
=
=
=
3
.26
×
10
ft
=
9.94 µm
(
)
p
cut
2
π
nv
pp
−
2550
π
×× ×
180 96
.
ti
p
g
Complete size efficiency table (Table 17.5) using Lapple's method (Lapple, 1951), which provides the
collection efficiency as a function of the ratio of particle diameter to cut diameter. Use the equation
110
−
(.)
η=
2
d
p
10
.
+
d
p
cut
to determine overall collection efficiency.
∑
w
i
n
i
(%) = 0 + 4 + 7.5 + 16 + 14.4 + 9.3 + 5.7 + 2.94 + 7 = 66.84%
■
EX AMPLE 17.7
Problem:
An air pollution control officer has been asked to evaluate a permit application to operate
a cyclone as the only device on the ABC Stoneworks plant's gravel drier (USEPA, 1984b, p. 68).
Given (design and operating data from permit application):
Average particle diameter = 7.5 µm
Total inlet loading to cyclone = 0.5 grains/ft
3
Cyclone diameter = 2.0 ft
Inlet velocity = 50 ft/s
Specific gravity of the particle = 2.75
Number of turns = 4.5 turns
Operating temperature = 70°F
Viscosity of air at operating temperature = 1.21 × 10
-5
lb/ft-s
Conventional cyclone
Air Pollution Control Agency criteria:
Maximum total outlet loading = 0.1 grains/ft
3
Cyclone efficiency as a function of particle size ratio is provided in Figure 17.6 (Lapple's
cur ve)
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