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488 Lawerence K. Wang et al.

Table 8
Percent RE Range of APCD for Point-Source PM Controls
Fly ash Acid gases <10 µm >10 µm Metals
Baghouses — — 99+ a 99+ a 90–95 b
Wet scrubbers — 95–99+ Low — 40–50 b
Venturi scrubbers — 99 80–95 80–95 Variable
Dry scrubbers — 95–99 99+ 99+ 95–99 b
ESP 99+ — 99 c 99 c 85–99+ b
Quench chambers — 50% — — —
HEPA filters — — 99.9+ d 99.9+ d —
a Except for “sticky” particles.
b Lower removal efficiency for mercury.
c For resistive particles.
d With high-pressure drop.
Source: US EPA.

Table 9
Percent of RE /APCD for Toxic Metals Controls
Pollutant

Air pollution control device Ba, Be Ag Cr As, Sb, Cd, Pb, Ti Hg*
WS a 50 50 50 40 30
VS-20 a 90 90 90 20 20
VS-60 a 98 98 98 40 40
ESP-1 95 95 95 80 0
ESP-2 97 97 97 85 0
ESP-4 99 99 99 90 0
WESP a 97 97 98 95 60
a
FF : FF/WS a 95 95 95 90 50
PS a 95 95 95 95 80
SD/FF; SD/C/FF 99 99 99 95 90
DS/FF 98 98 98 98 60
ESP-1/WS; ESP-1/PS 96 96 96 90 80
ESP-4/WS; ESP-4/PS 99 99 99 95 85
VS-20/WS a 97 97 97 96 80
WS/IWS a 95 95 95 95 85
WESP/VS-20/WS 99 99 98 97 9
C/DS/ESP/FF; C/DS/C/ESP/FF 99 99 99 99 98
SD/C/ESP-1 99 99 98 95 85

*Note: Flue gasses are assumed to have been precooled (usually in a quench).If gases are not cooled
adequately, mercury recoveries will diminish, as will cadmium and arsenic recoveries to a lesser extent.
a APCD codes:
C = Cyclone
WS = Wet scrubber, including sleve tray tower, packed tower, bubbles cap tower
PS = Proprietary wet scrubber design (high-efficiency PM and gas collection)
VS-20 = Venturi scrubber,approx 2630 in W.G. p WESP = Wet electrostatic precipitator
VS-60 = Venturi scrubber, approx >60 in W.G. p IWS = Ionizing wet scrubber
ESP-1 = Electrostatic precipitator: 1 stage DS = Dry scrubber
ESP-2 = Electrostatic precipitator: 2 stages FF = Fabric filter (baghouse)
ESP-4 = Electrostatic precipitator: 4 stages SD = Spray dryer (wet/dry scrubber)