Distillation Design Multiple Choice Questions & Answers (MCQs) on “Tray Flooding Mechanism”.
1. The expansion of liquid due to passage of vapor or gas is referred as?
a) Weeping
b) Drying
c) Cramping
d) Foaming
Answer: d
Clarification: It provides high interfacial liquid-vapor contact, excessive foaming often leads to liquid buildup on trays.
2. H/D Ratio, for a random packed bed is limited to
a) 9
b) 10
c) 7
d) 8
Answer: d
Clarification: Often bed height is restricted to 6 m. Higher packed height per bed is permitted for structure packing.
3. The value of HETP for most packing is?
a) 100 mm to 600 mm
b) 300 mm to 800 mm
c) 200 mm to 900 mm
d) 500 mm to 600 mm
Answer: b
Clarification: The corresponding value for structural packing is somewhat lower. Smaller the packing, lower the HETP value.
4. Each bed may have height equivalent of theoretical trays?
a) 4 to 8
b) 5 to 10
c) 6 to 15
d) 10 to 20
Answer: c
Clarification: Each bed may have height equivalent (HETP) to 6 to 15 theoretical trays for random packing and this is fixes as per standards.
5. Flooding determines?
a) Maximum vapor flow allowed
b) Maximum pressure allowed
c) Minimum vapor flow
d) Minimum pressure allowed
Answer: b
Clarification: Flooding determines the maximum vapor flow allowed, hence column capacity, Thus, if the column diameter is not sized properly, the column will not perform well.
6. Most distillation columns are open to the atmosphere.
a) True
b) False
Answer: a
Clarification: Although many of the columns are insulated, changing weather conditions can still affect column operation.
7. Tray efficiency vary from?
a) 10 to 5%
b) 30 to 100%
c) 40 to 60%
d) 60 to 100%
Answer: b
Clarification: Tray efficiency vary from 30% to 100%, but most hydrocarbon service, it is in the range of 60% to 80%.
8. Weeping determines?
a) Maximum vapor flow allowed
b) Maximum pressure allowed
c) Minimum vapor flow
d) Minimum pressure allowed
Answer: c
Clarification: Vapor flow velocity is dependent on column diameter, Weeping determines the minimum vapor flow required.
9. Most hydrocarbon services use tray spacing of
a) 150 mm to 700 mm
b) 350 mm to 400 mm
c) 450 mm to 600 mm
d) 500 mm to 600 mm
Answer: c
Clarification: Tray diameter calculation depends on tray spacing. Therefore, some optimization calculation may be required.
10. Weeping is indicated by
a) Sharp pressure drop
b) Reduced separation efficiency
c) Both a and b
d) No relation
Answer: c
Clarification: Weeping is indicated by a sharp pressure drop in the column and reduced separation efficiency, when liquid starts to leak through perforations.