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00000CH303121901

For dilute mixtures, show that the number of transfer units based the gas phase

for a counter current gas absorption in a packed tower is given by Nigg = ‏سے سے‎ नज
LM

Acetone-Air mixture containing 5 % (mole) acetone is scrubbed with pure water
in a counter current packed column of diameter 1.5 m in order to remove 95 % of
acetone. The gas mixture enters at a rate 3000 kg/h and the liquid rate is 50 % in
excess of the minimum. Equilibrium data at the operating conditions are (are

mole fractions of acetone).

x

(a) The liquid rate in kg/h

Determine:

(b) The mole percentage of acetone in the exit liquid
Explain adsorption wave and break through curve.
Discuss the nature of adsorbents and applications.
An air—water vapour mixture is available at a DBT 35 °C and ೩ WBT 30 °C.
Estimate its % humidity, dew point, humid heat, absolute humidity and enthalpy.
Explain the principle of wet bulb thermometry and obtain an expression for wet
bulb depression.
Write short note on different type of cooling towers.
PART C

Answer any two full questions, each carries 15 marks.
Explain the classification of dryers giving examples and indicating their field of
application.
With a neat rate curve explain the various regimes of drying.
Obtain an expression to determine the drying time needed to dry a substance
possessing both constant and falling rate drying characteristics.
A crystallizer is charged with 7500 kg of aqueous solution at 104 °C containing
30 % by weight of 718280). The solution is then cooled to 20 °C. During this
operation 5 % of the original water is lost by evaporation. Glauber salt
crystallizes and the solubility at 20 °C is 19.4 gm of ೫೩5೦, / 100gm of water.
Find the weight of i) Water lost by evaporation ii) Crystals formed iii) Mother
liquor leaving.

Explain different methods of achieving super saturation.

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