# Question: countercurrent absorption tray columns 3 calculating theoretical number of...

###### Question details

(Counter-Current Absorption – Tray Columns)

3) Calculating Theoretical Number of Stages in Counter-Current
Absorption: (35

points)

It is desired to recover atleast 95% of ethanol from a mixture of
ethanol and carbon

dioxide (containing 98 % CO2 and 2 % ethanol) by scrubbing the
vapor mixture with pure

water. Assume equilibrium relation Y = 0.57 X. The gas stream
enters the absorption

column at 180 kmol/hour (V’) at 120 kPa (P) and 27 °C (T).

The carrier gas may be considered insoluble in the solvent and
the solvent may be

considered nonvolatile. Assume dilute species with constant flow
rates and isothermal

and isobaric trays/stages.

(a) Calculate minimum water flow rate (L’min) to perform the operation.

(b) If the actual liquid rate is 1.5 times the minimum value,
solve for the actual number

of trays using graphical methods/EXCEL/MATLAB/MATHCAD etc.
Calculate

and show the concentrations after each stage.

(c) If the actual liquid rate is 1.5 times the minimum value,
solve for the actual number

of trays using the Kremser relationship.