Process Equipment and Plant Design

221. Pick out the wrong statement pertaining to the design of a long tube vertical evaporator.

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

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222. Pick out the wrong statement pertaining to the design of the distillation column.

1. Generally, a skirt clearance of 0.5" to 1.5' is recommended to prevent plugging of the slots by residue build up
2. The purpose of the slot is to disperse the gas into the liquid in the form of small bubbles
3. If sufficient slot area is not provided, the gas may pass through the skirt clearance
4. None of these

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223. Pick out the wrong statement pertaining to the use of valve tray, seive tray and bubble cap trays in continuous distillation column.

1. Bubble cap trays though most expensive are the best in situations, where low vapour rates is to be handled and a positive liquid seal is essential at all flow rates
2. Murphree efficiency of all the three trays are nearly equal, however the peak efficiency is generally higher for sieve and valve trays than the bubble cap
3. Maintenance cost for valve and sieve trays are comparatively more than bubble cap tray due to their relatively complicated construction features
4. Valve trays have the highest turn down ratio (i.e. the ratio of the highest to the lowest vapour flow rates) and thus provide the maximum flexible operating range

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224. Pick out the wrong statement.

1. If sufficient residence time (around 8 seconds) is not provided to the downcoming liquid in the downcomer, it may entrain some vapour
2. The liquid head in the downcomer should not be greater than one half the plate spacing to avoid flooding
3. The discharge end of the downcomer must project far enough into the tray liquid so that no gas bubbles can enter the open end and by pass the bubble caps
4. None of these

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225. Pick out the wrong statement. In an agitated vertical cylindrical reaction vessel, the

1. Ratio of liquid depth to tank diameter (i.e. the filling ratio) recommended for most purposes is 1
2. Filling ratio for dispersing gas in a liquid is 2 for sufficiently long contact period
3. Flat bottom and conical bottom vessels have low agitation efficiency for agitation of heavy solids in liquids
4. Dished bottom vessel has very high power consumption

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226. Pick out the wrong statement:

1. The tensile strength of a brittle material is less than its compressive strength
2. The compressive strength of a ductile material is less than its tensile strength
3. In a thick cylindrical shell, the hoop stress is maximum at the inner radius
4. The value of crushing load is more than that of buckling load for long columns

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227. Poisson's ratio of a material is the ratio of unit lateral strain to the unit axial elongation within its elastic limit. The value of Poisson's ratio for structural and pressure vessel steel may be taken as

1. 0.01
2. 0.3
3. 0.75
4. 0.95

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228. Ponchon Savarit method is based on the use of enthalpy concentration diagram, which contains the bubble point curve (saturated liquid curve), dew point curve (saturated vapour curve) and equilibrium tie lines. As compared to McCabe-Thiele's method, this method

1. is more accurate in finding the number of equilibrium stages
2. accounts for the enthalpy changes in the process
3. Facilitates direct calculation of heat load on reboiler & condenser from, the diagram used in this method
4. All 'a', 'b' & 'c'

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229. Power required for agitation depends upon the

1. Height & properties of the liquid
2. Agitator type & speed of agitation
3. Size of agitator & the tank
4. All (A), (B) and (C)

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230. Practical dividing line between a ductile and brittle materials is suggested, when the ultimate elongation is about 5%. Generally, larger the knuckle radius, stronger is the corner torus section of a head. The knuckle radius provided should be less than _________ of the head.

1. 6% of I.D.
2. 3 times the thickness
3. Either (A) or (B), whichever is larger
4. Either (A) or (B), whichever is smaller

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