Encyclopedia of Environmental Science and Engineering, Volume I and II

ELECTROSTATIC PRECIPITATION 283

The fundamental efficiency formula for an electrostatic

precipitator is

E = 1
 e
w/30.48AV

where

E = Collection Efficiency

A = Collection Area

V = Rate of Gas Flow

w = migration velocity, factor which is related to useful

electrical power

Low sulphur coal ash is not easy to collect with electrostatic

precipitators because of its high resistivity. This was inferred

from Figure 3 which shows by tests the effect of lowering

the sulphur in the coal on collection efficiency.

The Ramsdell Equation based on bus sections is a variation

of the fundamental formula and is expressed as

E = 1
 e
RB

where

E = Collection Efficiency

B = Number of active bus sections which is related to

useful electrical power

R = Performance Constant

Using tests data with medium and low sulphur coals and infor-

mation volunteered by other utilities for high sulphur coals, a

family of curves may be drawn (see Figures 4 and 5).

BUS SECTIONS PER 100,000 CFM

50

60

70

80

90

95

96

97

98

99

99.5

21

3.0 2.5 2.0 1.5 1.0 0.5

35674

COLLECTION EFFICIENCY PERCENT

BUS SECTIONS-EFFICIENCY

300°F

% S. IN COAL

FIGURE 4

12345

BUS SECTIONS PER 100,000 CFM

COLLECTION EFFICIENCY PERCENT

50

60

70

80

90

95

96

97

98

99

99.5

TEST 1965

2% S.

TEST 1967

1% S.

FIGURE 3

100 200 300 400

50

60

70

80

90

95

96

97

98

99

99.5

COLLECTING AREA PER 1000 CFM

SQUARE FEET

COLLECTION EFFICIENCY PERCENT

RAVENSWOOD 30

(600°F)

ASTORIA 30

ASTORIA 40, 50

ARTHUR KILL 20

HUDSON AVE. 100

ASTORIA 10, 20

EAST RIVER 70

74 th ST 120,121,122

FIGURE 2 Collecting efficiency vs Collecting area per 1000

CFM. Using this efficiency test data and precipitator collect-

ing area we were able to plot the equation or the dotted curve

shown in Figure 2.

C005_005_r03.indd 283C005_005_r03.indd 283 11/18/2005 10:22:01 AM11/18/2005 10:22:01 AM