Process Equipment and Plant Design problems
- 1. In a distillation column, the minimum residence time for liquid in the downspout is about __________ seconds.
Options- A. 1
- B. 8
- C. 80
- D. 180 Discuss
Correct Answer: 8
- 2. Pick out the wrong statement about the design of a sieve plate column.
Options- A. 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.
- B. 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.
- C. 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.
- D. 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. Discuss
Correct Answer: 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.
- 3. The circumferential (hoop) stress in a thin walled cylinderical vessel under internal pressure is
Options- A. pd/2t
- B. pd/4t
- C. pd/t
- D. pd/3t Discuss
Correct Answer: pd/2t
- 4. In case of a continuous distillation column, increase in reflux ratio may result in the
Options- A. lower fixed charges for the column.
- B. greater cost for the reboiler heat supply.
- C. greater cost for the condenser coolant.
- D. all (a), (b) and (c). Discuss
Correct Answer: all (a), (b) and (c).
- 5. Floating head heat exchangers are used for the
Options- A. heat transfer between corrosive fluids.
- B. cases where temperature difference between the shell and the tubes is more (>50°C).
- C. co-current heat transfer systems.
- D. counter-current heat transfer systems. Discuss
Correct Answer: cases where temperature difference between the shell and the tubes is more (>50°C).
- 6. In a shell and tube heat exchanger, tube side __________ of the mass velocity.
Options- A. heat transfer co-efficient is proportional to 0.8th power
- B. pressure drop is proportional to the square
- C. both 'a' & 'b'
- D. neither 'a' nor 'b' Discuss
Correct Answer: both 'a' & 'b'
- 7. In packed towers provided with saddle packing, liquid redistributors are positioned at every __________ times column diameter or 6 metres whichever is less.
Options- A. 2-3
- B. 5-8
- C. 10-15
- D. 20-25 Discuss
Correct Answer: 5-8
- 8. Thin spherical shells subjected to internal pressure, develop __________ stresses.
Options- A. radial
- B. circumferential
- C. both (a) & (b)
- D. neither (a) nor (b) Discuss
Correct Answer: radial
- 9. The maximum liquid gradient over a tray must not exceed
Options- A. 0.5" -1.25".
- B. 2"-3.5".
- C. 5".
- D. half the tray spacing. Discuss
Correct Answer: 0.5" -1.25".
- 10. Overall tray efficiency of a distillation column is the ratio of the number of
Options- A. overall gas transfer units to the number of ideal trays required.
- B. ideal trays required to the number of real trays required.
- C. real trays required to the number of ideal trays required.
- D. none of these. Discuss
Correct Answer: ideal trays required to the number of real trays required.
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