Pick out the wrong statement pertaining to the use of valve tray, seive tray and

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Question
Pick out the wrong statement pertaining to the use of valve tray, seive tray and bubble cap trays in continuous distillation column.
Options
A. 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.
B. Murphree efficiency of all the three trays are nearly equal, however the peak efficiency is generally higher for seive and valve trays than the bubble cap.
C. Maintenance cost for valve and seive 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 vapour flow rates) and thus provides the maximum flexible operating range.

Correct Answer

Maintenance cost for valve and seive trays are comparatively more than bubble cap tray due to their relatively complicated construction features.

4. Smaller sized packings are generally dumped to the packed columns, and the large ones of size greater than __________ mm are stacked individually, which provides better control over bed porosity and offers lower gas pressure drop.
Options
A. 25
B. 50
C. 75
D. 150

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

6. Correct use of 'factor of safety' is very important in equipment design. It is defined as the ratio of the
Options
A. ultimate stress to breaking stress.
B. ultimate stress to working stress.
C. working stress to ultimate stress.
D. none of these.

7. Pick out the wrong statement pertaining to the design of the bubble cap tray of a distillation column to give stable operation and even vapour distribution.
Options
A. The pressure drop due to the caps & slots and the static submergence should be as high as practicable for reasonable operation.
B. Tendency towards stable operation is increased by increasing the skirt clearance of the caps, lowering the rate of liquid flow per unit plate width or increasing the spacing between the caps.
C. The dimensionless ratio of liquid gradient to pressure drop head caused by the bubble cap assembly should be less than 0.4.
D. none of these.

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