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

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(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.

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