Process Equipment and Plant Design MCQs

12. Pick out the wrong statement about distillation operation

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Distillation under vacuum is a substitute for steam distillation.
In differential (simple) distillation, the vapour is removed as soon as it is formed without appreciable condensation.
In flash (equilibrium) distillation, a definite fraction of liquid is vaporised in such a way that the evolved vapour & residual liquids are in equilibrium with each other.
Flash distillation, differential distillation & steam distillation are all continuous distillation processes.
✅ The correct answer is option D.

13. Bubble cap tray is the most commonly used tray in large distillation column, because

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of its flexibility and nearly constant efficiency under varying conditions of operation.
it incurs less pressure drop as compared to any other try designed for the same duty.
it eliminates the foaming and entrain-ment tendency during operation.
none of these.
✅ The correct answer is option A.

17. For turbulent flow (NRe > 2100) of low viscosity fluid (μ > 20cp) in steel pipes, the optimum inside pipe diameter is given by(where, Q = fluid flow rate, ft3/sec.ρ = fluid density, lb/ft3 μ = fluid viscosity, centipoise Di = optimum inside pipe diameter, inches)

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Di, opt = 3.9 Q0.45 ρ0.13
Di, opt = 3.9 Q0.45 . μ0.95
Di, opt = 4.7 Q0.36 . μ3.2ρ0.13
Di, opt = 3 Q0.36 . μ0.88
✅ The correct answer is option A.

20. An increase in the liquid resistance to interphase mass transfer and a resultant reduction in plate efficiency is caused by

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an increase in liquid viscosity.
an increase in relatived volatility for rectification columns.
decrease in gas solubility for absorbers.
all (a), (b) and (c).
✅ The correct answer is option D.