All Free Chemical Engineering MCQs with Answers
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6,983 questions · page 269 of 350
- A. 0.02 to 0.05 d
- B. 0.08 to 0.12 d
- C. 0.2 to 0.5 d
- D. 0.5 to 0.6 d
Explanation: Dryer flights are typically shallow lifting elements, with a height of roughly 0.08 to 0.12 times the drum diameter.
Correct answer: 0.08 to 0.12 d5362. The function of manholes provided in the shell of a distillation column is to __________________?
- A. Keep a check on the liquid gradient over the plate by direct visual observation
- B. Guard against foaming & entrainment by dumping antifoaming agent through it
- C. Give access to the individual trays for cleaning, maintenance and installation
- D. All A., B. and C.
Explanation: Manholes provide physical access to trays and internal parts for inspection, cleaning, maintenance and installation.
Correct answer: Give access to the individual trays for cleaning, maintenance and installation5363. Pick out the wrong statement about the design of sieve plate column and the bubble cap column ?
- A. The downcomer design and the residence time in the downcomer is almost same for sieve
- B. plate and bubble cap columns
- C. Weir height for a bubble cap plate column is the same as that for a sieve plate column
- D. Weir length for a bubble cap plate is the same as that for the sieve plate
- E. Weir height in case of a bubble cap plate ranges from 50 to 150 mm and is higher than the
- F. sieve plate
Explanation: The downcomer arrangement and weir length are broadly comparable for sieve and bubble-cap trays, but bubble-cap trays normally use a…
Correct answer: Weir height for a bubble cap plate column is the same as that for a sieve plate column- A. Low gas velocity
- B. High gas velocity
- C. Low reflux ratio
- D. Excessive liquid gradient over the tray
Explanation: Back-trapping occurs when an excessive liquid-level gradient develops across the tray, causing liquid to move backward toward the inlet.
Correct answer: Excessive liquid gradient over the tray- A. Minimum and infinity
- B. Zero and one
- C. Zero and infinity
- D. None of these
Explanation: For a feasible distillation separation, the operating reflux ratio must be at least the minimum reflux ratio; at total reflux, it…
Correct answer: Minimum and infinity- A. 1.6 to 2
- B. 1.1 to 1.5
- C. 2.2 to 2.6
- D. 2.7 to 3
Explanation: Operating reflux is commonly selected at about 1.1 to 1.5 times the minimum reflux ratio, balancing equipment size against energy…
Correct answer: 1.1 to 1.5- A. 8 to 15
- B. 5 to 7
- C. 3 to 8
- D. 0.1 to 2
Explanation: A rotary vacuum filter drum rotates slowly so that cake formation, washing, drying and discharge can occur during each cycle.
Correct answer: 0.1 to 2- A. Cross flow
- B. Radial flow
- C. Split flow
- D. Cascade
Explanation: Cross-flow trays are the normal arrangement for smaller distillation columns, including columns up to about 4 ft in diameter.
Correct answer: Cross flow- A. 25
- B. 50
- C. 75
- D. 150
Explanation: Packings larger than about 75 mm are normally stacked by hand rather than dumped.
Correct answer: 75- A. 1/10th
- B. 1/20th
- C. 1/30th
- D. 1/50th
Explanation: Raschig rings should not be excessively large relative to the tower because poor liquid distribution and wall effects result.
Correct answer: 1/30th- A. All A., B. and C.
- B. Plate spacing
- C. Diameter of the column
- D. Allowable gas velocity through the slots
Explanation: The number of caps is selected so the vapour passes through the available slots at an acceptable velocity without excessive pressure drop…
Correct answer: Allowable gas velocity through the slots- A. 0.4-0.9
- B. 0.2-0.5
- C. 0.1-0.2
- D. 1.2-1.5
Explanation: For commercial tray and packing operations, practical HETP values commonly fall around 0.4 to 0.9 m.
Correct answer: 0.4-0.9- A. 6
- B. 18
- C. 24
- D. 34
Explanation: Small-diameter distillation columns can use closely spaced trays, with about 6 inches generally taken as the practical minimum.
Correct answer: 6- A. 2.5
- B. 7.5
- C. 15
- D. 20
Explanation: A clearance of about 7.5 cm between the overflow weir and the last row of caps is maintained so liquid can flow properly along the tray…
Correct answer: 7.55375. Maximum allowable vapour velocity in a bubble cap tower is determined by the ____________________?
- A. Entrainment considerations
- B. Vapour density
- C. Diameter of the column
- D. None of these
Explanation: The upper vapour-velocity limit in a bubble-cap tower is normally set by entrainment, where fast vapour carries liquid droplets to the…
Correct answer: Entrainment considerations- A. 0.4-0.6
- B. 0.1-0.2
- C. 0.35-0.75
- D. 0.55-0.85
Explanation: In large bubble-cap towers, the combined riser area is typically only about 10 to 20 percent of the tower cross-sectional area.
Correct answer: 0.1-0.2- A. Maldistribution of gas
- B. Back trapping
- C. All A., B. and C.
- D. Gas blowing beneath cap skit
Explanation: A large liquid gradient creates uneven liquid depth across the tray, causing gas maldistribution, back-trapping, and gas blowing under cap…
Correct answer: All A., B. and C.- A. 5
- B. 15
- C. 7.5
- D. 50
Explanation: For large industrial distillation columns of about 3 to 6 m diameter, round bubble caps are commonly sized near 15 cm.
Correct answer: 15- A. 2-3
- B. 20-25
- C. 10-15
- D. 5-8
Explanation: Liquid redistributors in packed towers are commonly installed after about 5 to 8 column diameters, with 6 m used as the maximum spacing…
Correct answer: 5-8- A. 0.1 to 0.3
- B. 0.6 to 0.7
- C. 0.85 to 0.95
- D. 1.5 to 2
Explanation: Distillation columns normally operate below flooding, commonly at about 60 to 70% of the flooding vapor velocity for non-foaming systems.
Correct answer: 0.6 to 0.7