Environmental Engineering Reference
In-Depth Information
If we assume chemical equilibrium we have:
[
]
BCO
BCO
2
K
=
eq
[][
]
2
We can combine this expression with the equilibrium of CO 2 in the gas
phase and in solution, as given by Henry's law:
(CO 2 ) g
CO 2
or,
[
]
CO
2
K
=
CO
2
(
)
CO
2
g
The solubility of CO 2 is now given by the sum of CO 2 in the liquid
phase and converted to BCO 2 :
(
) [
[
]
[
]
[ ]
]
,
CO
+
BCO
=
1
+
k
B
CO
2
2
eq
2
which we can relate to the partial pressure by introducing an effective
solubility:
(
)
[]
(
)
CO
+
BCO
=
1
+
k
B
K
CO
=
K
p
2
2
eq
CO
2
CO
g
2
2
We see that by increasing the concentration of component B in our solu-
tion we can enhance the solubility of CO 2 .
Rate limitations
As CO 2 moves from the gas to the liquid phase within an absorber,
the reaction rate can limit the rate at which equilibrium is reached.
Unfortunately, this complicates the way we think about mass
transfer within our absorbers. The process is shown schematically in
Figure 5.4.4 .
 
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