Environmental Engineering FOURTH EDITION

388 ENVIRONMENTAL, ENGINEEFUNG

Escaped

collection

Inflow

or feed Collection

0 device

Collected or

recovered

+

Figure 20-3. Diagram of a collection device.

The effectiveness of a collection device is evaluated according to the recovery of

the pollutant, as in (see Fig. 20-3)

x1

xo

R = - x 100, (20.1)

where

R = recovery of pollutant,

x1 = mass flow of pollutant recovered (in kg/s), and

xo = mass flow of pollutant produced (in kg/s).

If the mass flow of pollutant that escapes capture is designated x2, then

xo = x1 +x2,

and

R=- x1 x 100. (20.2)

x1 +x2

If the concentration of the pollutants and the rate of air flow are known, the recovery

may be expressed as

RE- X loo,

Qoco

(20.3)

where Q = air flow rate (in m3/s) and C = concentration of pollutant (in kg/m3),

and the subscripts refer to inflow and captured pollutant (see Fig. 20-3). When air

flow rates are not known, and only concentrations are measured, the recovery may be

shown to be

(20.4)

In air pollution terms, since the pollutants generated are to be separated from the air,

the recovery is called separation eficiency or collection eflciency.