Process Equipment and Plant Design
Which of the following is not a valid assumption in continuous binary distillation for calculating the number of equilibrium stages by Mc-Cabe-Thiele's method?

Sensible heat changes for vapour & liquid are negligibly small
Heat of mixing of normal liquid is assumed to be zero
Reflux is not a saturated liquid
Molar latent heat of the two components are equal

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Process Equipment and Plant Design
Overall distillation column efficiency for most of the refinery columns can be given by (for μ = 0.07 - 1.4 cp and relative volatility < 4) (where η = overall column efficiency, % μ = molal average viscosity of feed at average column temperature and pressure, cp Δp = pressure drop per tray, psi)

Η = 17 - 61.1 log μ
Η = 0.25 log μ - 1.67
Η = 1.66 - 0.25 log μ
Η = 24.6 (Δp/μ)

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Process Equipment and Plant Design
Pick out the wrong statement pertaining to the design of a long tube vertical evaporator.

None of these
Steam is fed to the shell, whereas the liquor is filled inside the tube
Tube dia is 3-6 cms, while tube length in 3-6 metres
Liquor level is maintained at l/3rd to 1/2 of the height of the tube

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Process Equipment and Plant Design
A forced circulation long tube vertical evaporator as compared to the natural circulation evaporator

Both B & C
Employs high velocity, high heat transfer rate and less heating surface requirement
Employs a centrifugal pump placed between external downtake from vapor drum and inlet to tube bundle
Is economical in operation

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