tb= breakthrough time
(min)
We = equilibrium
adsorption capacity (g/g carbon)
W = weight of carbon
adsorbent
rb = bulk density of the packed bed (g/cm3)
Q = volumetric flow rate
(cm3/min)
Co = inlet concentration
(g/cm3)
Cx = exit concentration
(g/cm3)
Wood, Gerry O., Estimating Service Lives of
Organic Vapor Cartridges, American Industrial Hygiene Association Journal, (1994,
January), pages 11-15.
How
do the results of Wood's Equation compare with Experimental Tests? See the Comparison.
Supporting Data:
The parameter We
can be estimated using the following equation:
W
o = carbon micropore
volume (cm3/g)
dL = liquid density of
adsorbate (g/cm3)
T = absolute temperature
(°K = °C + 273)
r = partial pressure corresponding to
concentration Cx
rsat = saturation vapor
pressure at temperature T
Pe = molar polarization
R = ideal gas constant
(1.987)
b' = an empirical
coefficient with value 3.56 x 10-5.
The parameter Pe can be estimated using
the following equation:
Mw
= molecular weight
nD = refractive index
The parameter kv has been estimated by Wood from
experimental data to be equivalent to the following equation:
I
= calculated to be
0.000825
S = 0.036 for 1%
breakthrough
VL = linear airflow
velocity (cm/sec)
Wood uses an example of hexane with the following information:
T
= 22 °C (295 °K).
Pair of cartridges with a work rate of 53.3 L/min.
Wo = 0.454 [determined
from experimental data]
dL = 0.6603 [available
from scientific handbooks]
Pe = 29.877 [calculated from available
data]
rsat = 121 torr [available
from scientific handbooks]
r = .38 torr (500 ppm challenge
concentration) [calculated from available data]
VL = 11.22 cm/s
[calculated from available data]
W = 70.6 g [calculated
from available data]
Co = .00178 g/cm3
[calculated from available data]
kv = 4242 min-1