A. Maldistribution of gas
B. Back trapping
C. Gas blowing beneath cap skit
D. All A., B. and C.
Related Mcqs:
- Liquid gradient over the tray results due to the___________________?
A. Resistance offered to flow of liquids by caps & risers and the flow of gas
B. Low gas velocity
C. Large plate spacing
D. Large reflux ratio - The maximum liquid gradient over a tray must not exceed__________________?
A. 0.5″ -1.25″
B. 2″-3.5″
C. 5″
D. Half the tray spacing - Maximum acceptable total liquid gradient over a tray is about _______________ mm?
A. 5.5
B. 12.5
C. 30.5
D. 45.5 - Liquid gradient over a tray can be minimised by________________?
A. Providing a higher skirt clearance or a higher weir
B. Decreasing the number of rows of caps through which the liquid flows or by decreasing the
velocity of liquid flow past the caps or by reducing the distance along the tray through which
the liquid must flow
C. Using split flow, radial flow or cascade flow for column diameter large than 4 ft
D. All A., B. and C. - Bubble cap tray is the most commonly used tray in large distillation column, because______________?
A. Of its flexibility and nearly constant efficiency under varying conditions of operation
B. It incurs less pressure drop as compared to any other try designed for the same duty
C. It eliminates the foaming and entrainment tendency during operation
D. None of these - 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 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 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 vapour flow rates) and thus provide the maximum flexible operating range - Generally, as the length of the liquid path on a tray is increased beyond 5 ft, the overall column efficiency___________________?
A. Increases
B. Decreases
C. Remain same
D. May increase or decrease depending upon the plate spacing - Power required for agitation depends upon the______________________?
A. Height & properties of the liquid
B. Agitator type & speed of agitation
C. Size of agitator & the tank
D. All A., B. and C. - Overall tray efficiency of a distillation column is the ratio of the number of ___________________?
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 - An adequate clearance between the tray and the shell wall of a distillation column is provided to_____________________?
A. Drain the liquid from the tray when the unit is not in operation
B. Allow for thermal expansion and facilitate installation
C. Avoid back-trapping
D. None of these
