Environmental Engineering Reference
In-Depth Information
When
n
=
N
,
x
n
=
x
D
:
ln
x
D
(1
−
x
B
)
x
B
(1
−
x
D
)
N
=
Fenske equation;
ln
α
for H
2
O
16
and H
2
O
18
;
α
=
1
.
006
and water contains 0.002 mole fraction H
2
O
18
. Therefore:
x
D
=
0
.
998
x
B
=
0
.
9746
=
N
430 stages
(from Fenske equation)
x
F
/
x
B
=
=
3920;
N
503 stages
(from Smoker equation).
D.3
Problems
D.1 Derive the Kremser equation for the case where
E
mV
=
1.
D.2 Steam distillation is used to remove ethanol from water. The water enters with an
ethanol mole fraction equal to 0.02 and the exit requirement is a mole fraction equal
to 10
−
4
. The equilibrium relation is
y
V
ratio equal to 5, what is the
exit ethanol vapor mole fraction? How many equilibrium stages are needed?
D.3 The flowsheet below is a liquid-liquid extraction process for uranyl nitrate (UN)
extraction using tributyl phosphate (TBP). For this problem, the flowrates and equi-
librium relation are in lb
m
instead of moles. The quantities
x
and
y
are the mass
=
9
x
. For an
L
/
V
,
y
0
n
2
1
3
L
,
x
1
fraction of UN in the
L
(H
2
O) and
V
(TBP) phase respectively. For conditions
where
L
=
90 lb
m
/
hr and
V
=
150 lb
m
/
hr, derive an equation for
y
n
in terms of
n
,
10
−
3
and
y
n
=
5.5x
n
.
D.4 Redo Example 5.1 cross-flow cascade, using the finite difference approach.
given:
x
1
=
1.2
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