Particulate Emission Control - Mathematics and Statistics for the Environment - page 519

Volumetric flow rate of contaminated gas = 50,000 acfm
Number of compartments = 6
Number of bags per compartment = 100
Bag diameter = 6 inches
Pressure drop across the system = 6 in. H 2 O
Number of broken bags = 2 bags

Assume that all the contaminated gas emitted through the broken bags is the same as that passing
through the tube sheet thimble.

Solution: Calculate the collection efficiency and penetration before the bag failures. Collection
efficiency is a measure of degree of performance of a control device; it specifically refers to degree
of removal of pollutants. Loading refers to the concentration of pollutants, usually in grains of
pollutants per cubic feet of contaminated gas streams. Mathematically, the collection efficiency is
defined as

Inletloading Outletloading
Inletloading

−

×100

η=

From the preceding equation, the collected amount of pollutants by a control unit is the product of
collection efficiency η and inlet loading. The inlet loading minus the amount collected gives the
amount discharged to the atmosphere.
Another term used to describe the performance or collection efficiency of control devices is
penetration ( P t ):

P t = 1 - η/100 (fractional basis)

P t = 100 - η (percent basis)

The effect of bag failure on baghouse efficiency is described by the following:

P t 1 = P t 2 + P tc

P tc = 0.582(∆ p ) 0.5 /ϕ

ϕ = Q /( LD 2 [ T + 460) 0.5 ]

where
P t 1 = Penetration after bag failure.
P t 2 = Penetration before bag failure.
P tc = Penetration correction term, contribution of broken bags to P t 1 .
∆ p = Pressure drop (in. H 2 O).
ϕ = Dimensionless parameter.
Q = Volumetric flow rate of contaminated gas (acfm).
L = Number of broken bags.
D = Bag diameter (in.).
T = Temperature (°F).

Calculate collection efficiency η:

η = (Inlet loading - Outlet loading)/(Inlet loading) = (4.0 - 0.02)/(4.0) = 0.005 = 99.5%