Geoscience Reference
In-Depth Information
100
90
80
70
60
50
40
30
20
10
0
0
20
40
60
80
100
120
Particle Size, Microns
FIGURE 17.4
Size efficiency curve for settling chamber. (Adapted from USEPA,
Control
of
Gaseous
and
Particulate
Emissions: Self-Instructional Problem Workbook
, EPA 450/2-84-007, U.S. Environmental
Protection Agency Air Pollution Training Institute, Research Triangle Park, NC, 1984.)
TABLE 17.3
Data for Calculation of Overall
Collection Efficiency
d
p
(µm)
Weight Fraction (
w
i
)
η
i
10
0.027
1.1
25
0.069
7.1
35
0.094
14
45
0.105
23
55
0.105
34
65
0.095
48
75
0.07
64
85
0.095
83
94
0.34
100.11
Total
1
wall and fall to the bottom of the cone, where they are removed. The cleaned gas flows out the top of
the cyclone (see Figure 17.5). Cyclones have low construction costs and have relatively small space
requirements for installation. Cyclones are much more efficient in particulate removal than that of
settling chambers. However, note that the cyclone's overall particulate collection efficiency is low,
especially on particles below 10 µm in size, and they do not handle sticky materials well. The most
serious problems encountered with cyclones are with airflow equalization and their tendency to plug
(Spellman, 1999). They are often installed as precleaners before more efficient devices such as elec-
trostatic precipitators and baghouses (USEPA, 1984a, p. 6-1). Cyclones have been used successfully
at feed and grain mills, cement plants, fertilizer plants, petroleum refineries, and other applications
involving large quantities of gas containing relatively large particles.
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