Environmental Engineering Reference
In-Depth Information
7.12
Questions
7.1 Why would you want the mass transfer zone in an adsorption column to be as small
as possible?
7.2 What are the differences between breakthrough and exhaustion?
7.3 What are the important criteria for choosing an adsorbent?
7.4 How would a lower amount of dispersion in an adsorption column affect the break-
through curve?
7.5 Show that the limits described for Equation (7.17) are valid.
7.13
Problems
7.1 Show that a mass transfer zone that propagates as a stoichiometric front would corre-
spond to the shortest sorbent bed needed.
7.2 Chlorides are removed from water with a carbon adsorbent. The carbon particle diam-
eter is 0.2 cm, the viscosity and density of water are 0.8 cP and 1 g
cm 3 , respectively,
/
10 4 cm 2
and the diffusion coefficient of the chlorides in water is 2.37
×
/
s. Calculate
the mass transfer coefficient and bed diameter to treat 125,000 cm 3
/
s water for super-
ficial velocities of 5, 10, 25, 100, 250 cm
/
s. Explain the disadvantage of increasing
the superficial velocity.
7.3 For Problem 7.2, estimate the pressure drop for
v s =
10 cm
/
s and 25 cm
/
s. By
=
what factor does the pressure drop increase? Assume L
1 m and bed void fraction
=
0.5.
7.4 Aqueous effluent from a processing plant contains 300 mg
(
)
/
L toluene that is to be
reduced to 15 mg
L prior to discharge. 640,000 L of a 400 L/min stream need to
be treated prior to breakthrough. The rate constant, k 1 , is 5.56 L
/
/
kg
·
min and q 0 is
0.2 g
g based on small-scale studies. What mass of adsorbent is required in the design
adsorption column?
/
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