Chemical Plant Design Online Quiz Questions - Set 21 - ObjectiveBooks

# Practice Test: Question Set - 21

1. Normally, the ratio of the total riser area to the tower cross sectional area (for bubble cap towers of diameter more than 3 ft) is around
(A) 0.4-0.6
(B) 0.35-0.75
(C) 0.1-0.2
(D) 0.55-0.85

2. Pick out the wrong statement pertaining to the use of valve tray, seive tray and bubble cap trays in continuous distillation column.
(A) Bubble cap trays though most expensive are the best in situations, where low vapor rates is to be handled and a positive liquid seal is essential at all flow rates
(B) 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
(C) Maintenance cost for valve and sieve trays are comparatively more than bubble cap tray due to their relatively complicated construction features
(D) Valve trays have the highest turn down ratio (i.e. the ratio of the highest to the lowest vapor flow rates) and thus provide the maximum flexible operating range

3. Maximum allowable vapor velocity in a bubble cap tower is determined by the
(A) Entrainment considerations
(B) Vapor density
(C) Diameter of the column
(D) None of these

4. Overall distillation column efficiency for most of the refinery columns can be given by (for Î¼ = 0.07 - 1.4 cp and relative volatility < 4) (where Î· = overall column efficiency, % Î¼ = molal average viscosity of feed at average column temperature and pressure, cp Î”p = pressure drop per tray, psi)
(A) Î· = 17 - 61.1 log Î¼
(B) Î· = 24.6 (∆p/Î¼)
(C) Î· = 1.66 - 0.25 log Î¼
(D) Î· = 0.25 log Î¼ - 1.67

5. In condenser, the cooling water is passed in the tube side in a pass arrangement, because
(A) It reduces heat transfer area
(B) More thinner tubes can be used
(C) Pressure drop is reduced
(D) It makes condenser compact

6. It is not desirable to design a heat exchanger for LMTD correction factor, FT, of less than
(A) 0.99
(B) 0.95
(C) 0.80
(D) 0.55

7. Joint efficiency (J) for a seamless pipe is
(A) 1
(B) 0.85
(C) 1.5
(D) < 0.5

8. Pick out the wrong statement
(A) For all the cylindrical process vessels operating above atmospheric pressure, formed heads are used for closing the vessel
(B) Fouling factor of river water is less than that of sea water
(C) Risers provided in bubble cap trays in the distillation column facilitate the flow of both liquid and vapor
(D) Both (b) and (c)

9. In a distillation column, minimum clearance to be maintained between the overflow weir and the last row of the bubble caps is __________ cms.
(A) 2.5
(B) 7.5
(C) 15
(D) 20

10. The operating velocity in the absorption tower is usually 40-50% of the flooding velocity. Packed absorption towers are normally designed for a pressure drop of about __________ mm of water column per meter height of packing.
(A) 1-5
(B) 20-40
(C) 100-150
(D) 1000-1500

11. For a cylindrical internally pressurized vessel, which of the following closure types would withstand highest pressure, if each closure is of the same material and thickness?
(A) Hemispherical
(B) Ellipsoidal (2 : 1)
(C) Conical
(D) Flat plate

12. Pick out the correct statement.
(A) When highly corrosive fluids are to be handled, the plate towers prove to be cheaper and easier to construct than packed tower
(B) Packed towers are generally preferred over plate towers, if the liquids have a foaming tendency
(C) The pressure drop through the packed towers is generally more than the pressure drop through plate towers designed for same duty
(D) None of these

13. The minimum tray spacing in distillation column of diameter less than 3 ft is normally __________ inches.
(A) 6
(B) 18
(C) 24
(D) 34

14. Pressure drop (Î”p) and the superficial gas mass velocity (G) in case of packed absorption tower operating in the preloading range are related as
(A) Î”p = G
(B) Î”p = G0.5
(C) Î”p = G2
(D) Î”p = 1/G0.6

15. The practical representative values of HETP for a number of commercial operations lies within a range of __________ meter.
(A) 0.1-0.2
(B) 0.2-0.5
(C) 0.4-0.9
(D) 1.2-1.5

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