Process Equipment and Plant Design
Pick out the wrong statement about the design of a sieve plate column.

For segmental downcomers, the chord length is 60-80% of the column diameter. An initial value of downcomer area of 12% is taken in the design
Width of the calming section provided at the inlet and outlet sides of the plate is 75 mm for column diameter below 1.5 metres and 100 mm for larger diameter columns
Minimum recommended downcomer residence time for the disengagement of entrained vapour is the same for both foaming and non-foaming liquids, which is about 20 seconds
An increased weir height improves the tray efficiency at the cost of high plate pressure drop; optimum wear height being 40-90 mm for column pressure above atmospheric and 6-12 mm for vacuum columns

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Process Equipment and Plant Design
When one of the fluids is highly corrosive and has fouling tendency, it should

Preferably flow inside the tube for its easier internal cleaning
Perferably flow outside the tube
Flow at a very slow velocity
Flow outside the tube, when the flow is counter-current and inside the tube when the flow is co-current

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

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