Hole diameter of the seive trays in the distillation column ranges from __________ mm.

Statements : All the bottles are boxes. All the boxes are bags. Some bags are trays.

Conclusions :
I. Some bottles are trays.
II. Some trays are boxes.
III. All the bottles are bags.
IV. Some trays are bags.

A

Only (III) and (IV)

B

Only (I) and (II)

C

Only (II) and (III)

D

Only (I) and (IV)

In seive plate column, holes are drilled or punched in sizes ranging from 2.5 to 12 mm (5 mm being widely used). The hole pitch is normally __________ times the hole diameter to give the required hole area.

A

0.5 to 1.5

B

2.5 to 4.0

C

5 to 10

D

10 to 15

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 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

A high vapour velocity is required for high plate efficiency in a seive plate coloumn. The satisfactory value of operating vapor velocity for design purpose in seive plate column is about __________ percent of the flooding velocity.

A

45

B

60

C

80

D

95

In a distillation column, bubble caps are located on trays with a pitch of __________ times the outside diameter of the caps.

A

1.3 to 2

B

1.6 to 2

C

2.5

D

1.5 to 3

Pick out the wrong statement about the design of seive plate column and the bubble cap column.

A

The downcomer design and the residence time in the downcomer is almost same for seive plate and bubble cap columns

B

Weir length for a bubble cap plate is the same as that for the seive plate

C

Weir height for a bubble cap plate column is the same as that for a seive plate column

D

Weir height in case of a bubble cap plate ranges from 50 to 150 mm and is higher than the seive plate

Diameter of the seive tray column is determined by the

A

Lower limit of vapour velocity

B

Upper limit of the vapour velocity

C

Hole diameter of the seive tray

D

Height of the plate spacing

If the ideal trays are 7.7 and the efficiency of each one is 0.5, then real number of trays are

A

15.4

B

14.1

C

15.0

D

18.5

Acetone is to be removed from air in an isothermal dilute absorber using pure water as solvent. The incoming air contains 5 mole% of acetone (y_in = 0.05). The design equation to be used for obtaining the number of trays (N) of the absorber is: N + 2 = 6 log $$\left( {\frac{{{{\text{y}}_{{\text{in}}}}}}{{{{\text{y}}_{{\text{out}}}}}}} \right).$$
For 98% recovery of acetone, the number of trays required is/are

A

1

B

8

C

9

D

10

Larger depth of liquid on the trays of a distillation column

A

Leads to high tray efficiency

B

Results in higher pressure drop per tray

C

Both A & B

D

Neither A nor B

Hole diameter of the seive trays in the distillation column ranges from __________ mm.

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