Particulate Emission Control - Mathematics and Statistics for the Environment - page 514

where
η = Overall collection efficiency.
w i = Weight fraction of the i ith particle size.
η i = Collection efficiency of the i ith particle size.

Is the overall collection efficiency greater than 98%? Yes.
Now determine whether the outlet loading meets the USEPA standard. First calculate the outlet
loading in grains/ft 3 :

Outlet loading = (1.0 - η) × (inlet loading)

where η is the fractional efficiency for the above equation.

Outlet loading = (1.0 - 0.9861) × 14 = 0.195 grains/ft 3

Is the outlet loading less than 0.2 grains/ft 3 ? Yes. Is the vendor's claim verified? Yes.

17.4.4 b aghouses (F abriC F filters) )
“The term baghouse encompasses an entire family of collectors with several types of filter bag
shapes, cleaning mechanisms, and body shapes” (Heumann, 1997). Baghouse filters (or fabric fil-
ters or more properly called tube filters) are the most commonly used air pollution control filtration
system. In much the same manner as the common vacuum cleaner, fabric filter material, capable
of removing most particles as small as 0.5 µm and substantial quantities of particles as small as 0.1
µm, is formed into cylindrical or envelope bags and suspended in the baghouse (see Figure 17.8).
The particulate-laden gas stream is forced through the fabric filter, and as the air passes through the
fabric, particulates accumulate on the cloth, providing a cleaned airstream. As particulates build up
on the inside surfaces of the bags, the pressure drop increases. Before the pressure drop becomes too
severe, the bags must be relieved of some of the particulate layer. The particulates are periodically
removed from the cloth by shaking or by reversing the airflow.

Mechanism for shaking,
rapping, or vibrating bags

Tubular
lter
bags

Clean
air out

Clean
air out

Dirty
air in

Collected
dust out

Dirty
air in

FIGURE 17.8 Typical simple fabric baghouse design. (From USEPA, Control Techniques for Gases and
Particulates , U.S. Environmental Protection Agency, Washington, DC, 1971.)