Gas Emission Control - Mathematics and Statistics for the Environment - page 474

100

77°F

10

212°F

1

0.01 0.001 0.01 0.1 1

Partial Pressure, psia

FIGURE 16.16 Adsorption isotherm for toluene. (Adapted from USEPA, APTI Course 415: Control
of Gaseous Emissions , EPA 450/2-81-005, U.S. Environmental Protection Agency Air Pollution Training
Institute, Washington, DC, 1981.)

Given:
LEL for toluene = 1.2%
Molecular weight of toluene = 92.1 kg/kg-mol
Carbon density = 480 kg/m 3 (30 lb/ft 3 )

Solution : First calculate the toluene flow rate:

3.78 m 3 /s × 50% × 1.2% = 0.023 m 3 /s toluene

To determine the saturation capacity of the carbon, calculate the partial pressure of toluene at the
adsorption conditions:

pY ==

3

0 023 m/s

3.78 m/s

.

( 14.7 psia ) = 0 .089 psia

3

From Figure 16.16, the saturation capacity of the carbon is 40% or 40-kg toluene per 100kg of car-
bon. The flow rate of toluene is

=

kg-mol
22.4 m

273 K
350 K

92.1 kg
kg-mol

( )

3

0.023 m/s 0.074 kg/s

3

The amount of carbon at saturation for a 4-hour cycle is

100 kg carbon
40 kg tolu

3600 s
hr

( )

(

) =

0.074 kg/stoluene 4hr 2664 kg of c arbon

ene