Process Equipment and Plant Design

211. Pick out the wrong statement about distillation operation

1. Distillation under vacuum is a substitute for steam distillation
2. In differential (simple) distillation, the vapour is removed as soon as it is formed without appreciable condensation
3. 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
4. Flash distillation, differential distillation & steam distillation are all continuous distillation processes

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212. Pick out the wrong statement about routing of fluids in a shell and tube heat exchanger.

1. The corrosive and fouling fluid should be preferably routed through the tubes
2. The viscous fluid should be routed through the shell side
3. Lower flow rate fluid should be routed through the shell side
4. Higher pressure fluid stream should be routed through the shell side

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213. Pick out the wrong statement about the design of a sieve plate column.

1. 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
2. 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
3. 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
4. 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

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214. Pick out the wrong statement about the design of sieve plate column and the bubble cap column.

1. The downcomer design and the residence time in the downcomer is almost same for sieve plate and bubble cap columns
2. Weir length for a bubble cap plate is the same as that for the sieve plate
3. Weir height for a bubble cap plate column is the same as that for a sieve plate column
4. Weir height in case of a bubble cap plate ranges from 50 to 150 mm and is higher than the sieve plate

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215. Pick out the wrong statement pertaining to 'Horton sphere' used for the storage of liquid ammonia.

1. Diameter of Horton sphere is normally 6 to 25 metres and it is supported by 6 to 12 nos. tubular or rolled section column
2. Thickness of spherical shell is half that of the cylindrical vessel under same operating pressure condition. Besides, the ratio of surface area to volume is less for sphere than any other shape; hence insulation required is less
3. Horton sphere is used for the storage of gases and volatile liquid at a moderate pressure of 1 to 10 kg/cm²
4. Horton sphere is used for the storage of liquid at sub-zero temperature at very high pressure upto 200 kg/cm²

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216. Pick out the wrong statement pertaining to a shell and tube heat exchanger.

1. The minimum value of baffle spacing is 50 mm
2. The maximum value of baffle spacing is equal to the I.D. of the shell
3. The maximum unsupported tube span is generally about 75 times tube diameter, but is reduced to about 60 times for aluminium, copper & alloys of these
4. Disk and doughnut baffle is the most commonly used baffle

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217. Pick out the wrong statement pertaining to shell and tube heat exchanger.

1. Clearance between shell & baffles and between tube & baffles should be minimum to avoid by-passing of the fluid, but it should be enough to permit the removal of tube bundle
2. Baffles are supported independently of the tubes by tie rods and positioned by spacers
3. Tie rods are fixed at one end in the tube sheet by making blind holes and the minimum number of tie rods is 4 with at least 10 mm diameter
4. Bracket supports are used for horizontal shell, while saddle support is used for vertical shell

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218. Pick out the wrong statement pertaining to the comparative evaluation of performance of the packed tower and the plate tower.

1. Plate tower is preferred, if interstage cooling is required to remove heats of reaction or solution
2. Plate tower is preferred over packed tower, if the operation involves liquids containing dispersed solids
3. The total weight of a dry plate tower is usually much more than that of a dry packed tower designed for the same duty
4. In operations involving large temperature changes. (e.g. distillation), plate towers are preferred over packed towers as the packing may be crushed due to large temperature changes

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219. Pick out the wrong statement pertaining to the design of a basket type evaporator.

1. It is used for high viscosity liquor having large rate of scaling
2. The tube bundle is suspended on bracket
3. There is no central downtake
4. Downtake is formed by the annular space between the bundle and the shell

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220. Pick out the wrong statement pertaining to the design of a horizontal tube evaporator.

1. It is unsuitable for concentrating those liquids, which form a scale or deposit salt
2. It is suitable for process, in which the final product is a liquor instead of solid
3. Its usual dimensions are: tube dia = 2-3 cms; evaporator body dia = 1-4 metres and evaporator height = 2.5-4 metres
4. Liquor flows inside the tube, while the steam is outside submerging the tube

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