Prof. Dr. Marco Mazzotti - Institut f

1
Nonisothermal case temperature profile in the
column
Prof. Dr. Marco Mazzotti - Institut für
Verfahrenstechnik
2
The Absorption Scheme
This is a simple diagram showing the notation we
will use later. The liquid enters the column at
its top flowing by gravity trough the column. The
gas enters at the bottom. With this
configuration, work is not required for the flow
transport. The heat of absorption of solute
(gas) increases the temperature of the solution.
When the gas (G) enters the column at about 10 to
20C under the liquid temperature going out (L),
and the liquid is volatile, evaporation will cool
down the liquid at the bottom of the column. This
means that the temperature profile in the column
will present a maximum near its bottom. You may
print this out to have in mind the notation.
3
h
L
1
This diagram represents the temperature of the
Liquid across the column. When the heat of
absorption is not significant and the effect of
liquid evaporation can be neglected, the
adiabatic absorption column has a constant
temperature along the height.
Absorption Column
Liquid temperature
T
2
T2 T1
4
h
L
1
Along the column, the absorption of gas increases
the temperature. Gas and liquid temperatures are
similar at the bottom, and the gas entering the
column is already saturated. The changes in
temperature are only due to the heat of
absorption of solute gas. This is why
temperature only increases along the column.
Absorption Column
Liquid temperature
T
2
T1
T2
5
h
L
1
Along the column, the absorption of gas increases
the temperature. The gas enters the column at a
lower temperature than the liquid and thus, at
the bottom the evaporation of liquid is
important. This is why the temperature
decreases at the bottom.
Absorption Column
Liquid temperature
T
2
T1
Tmax
T2