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Electrostatistic Precipitation 193

corrosion include the outer shell walls, the roof plate, the collecting plate surfaces, the
high-voltage system, the hoppers, the access doors, the expansion joints, and the test
ports. Good design and proper maintenance with an understanding of common corro-
sion processes and preventive measures as outlined in Hall and Katz (36) can provide
viable equipment with long life in service.
6. EXPECTED FUTURE DEVELOPMENTS

Among the candidates for upgrading conventional ESPs are advanced digital voltage
controls, flue gas conditioning, intermittent energization, temperature-controlled
precharging, wide plate spacing, and positive energizition of corona electrodes for
hot-side ESPs. For future developments, the following expected emphases in ESP
development are forecast over the next few years:

1. Use of computer models for precipitator design and performance analysis
2. Derivation of a valid theory whereby the relative importance of the different factors is
reflected directly in the precipitator equations
3. Reduction of the size and cost of a precipitator required for a specific duty
4. Use of wet precipitators in controlling fine particles
5. Design toward even higher efficiency, particularly in the collection of small particles,
which is generally the main justification for using an electrostatic precipitator
6. Use of the electrostatic precipitation process for newer industrial processes such as coal
gasification, gas turbine, and magneto-hydrodynamic (MHD) power generation

NOMENCLATURE

2
a Cross-sectional area normal to the current flow (cm )
a" Empirical constant
2
A Total collecting electrode surface area (m )
2
A Actual overall collecting plate surface area (m )
a
A Particle radius (m)
A' Constant for gas (V/m)
1/2
B' Constant for gas (V/m )
b Wire-to-plate spacing (m)
b" Empirical constant
C Cunningham correction factor (dimensionless)
3
C Inlet particulate concentration (kg/m )
in
3
C Outlet particulate concentration (kg/m )
out
3
C Particulate concentration (kg/m )
p
c Wire-to-plate spacing (m)
c" Empirical constant
d Electrode duct width (m)
d' Dimension variable, Eq. (13)
d'' Empirical constant
D Width of ducts
E Electric field (V/m)
E Activation energy
a
E Corona-starting field (V/m)
e