Environmental Engineering Reference
In-Depth Information
2.11 List the four ways in which separating agents generate selectivity. Which of these
applies to (i) distillation, (ii) membrane separations, and (iii) adsorption?
2.12 Explain how an MSA used in reversible chemical complexation differs from that
used in adsorption. What is the advantage of reversible chemical complexation over
non-complexing separation processes?
2.14
Problems
2.1 Imagine that the height of an absorption column varies directly as the natural logarithm
of the ratio of the exiting and entering contaminant concentration:
height
=
f [ ln( C exit /
C enter )]
.
To reduce a contaminant to 10% of its initial concentration, a column 3 meters tall is
needed. For a similar separation, how tall must the column be to reduce the contaminant
to 5% of its initial concentration?
2.2 The diameter of a distillation column operating at a specified gas velocity varies with
the square root of the volumetric throughput (ft 3
/
s):
f (throughput 1 / 2 )
diameter
=
.
If the throughput triples and the velocity remains the same, by what factor must the
column diameter increase or decrease? For a column with a throughput of 100 ft 3
/
min,
the diameter is 3.6 feet. A new column with a throughput of 260 ft 3
/
min is to be built
for a similar separation. What must the diameter be?
2.3 A Langmuir isotherm for an adsorption experiment shows that X , the amount of solute
sorbed per weight sorbate, is 0.085 when the solute concentration in the fluid phase
is 0.05. If the Langmuir constant K for the experimental conditions is 1.3, apply the
concept of a unit operation to determine the value of X when the solute concentration
is 0.1. Plot the Langmuir isotherm for C values of 2, 4, 6, 8, and 10. What does the
plot tell you about the amount of solute absorbed vs the fluid phase concentration?
2.4 The list (a) to (r) on the facing page is a set of separation items and issues where a
problem is identified and a solution implemented. For the chosen item:
(i) State the separation objective.
(ii) Using the criteria for choosing a separation process, explain why this solution
was chosen.
(iii) Describe the separation method(s) used to achieve this objective.
(iv) Provide data, calculations, flow diagrams, schematics, etc., to determine the
ability of the separation method to achieve its objective.
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