Multiple choice question for engineering
1. When the liquid becomes dispersed and gas becomes continuous, such process is called?
a) Spray regime
b) Emulsion regime
c) Pray Regime
d) Camp regime
Answer: a [Reason:] At low liquid rates and higher vapor velocities the vapor starts disintegrating into liquid this is called as spray regime.
2. The performance diagram is drawn between?
a) Entrainment and Velocity
b) Gas and flooding velocity
c) Vapor and liquid rate
d) Tray height and Diameter
Answer: c [Reason:] The operable limits of tray in respect of gas and liquid flow rates depend at tray design, thus the performance diagram is drawn between Vapor and liquid rate.
3. The turndown ratio is defined as the ratio of?
a) Design vapor to operable throughput
b) Entrainment to Velocity
c) Tray height to Diameter
d) Gas to flooding velocity
Answer: a [Reason:] The turndown ratio is defined as the ratio of Design vapor to operable throughput, sieve trays have a low turn down ratio.
4. The distance between two consecutive trays in a column is ______
a) Baffle spacing
b) Tray spacing
c) Sieve spacing
d) Cart Spacing
Answer: b [Reason:] Tray spacing varies between ranges of 8 to 36 inches for a given column not vary from each other.
5. The fractional hole area Fh, is defined as?
a) (Hole diameter/hole pitch)2
b) K’ (hole pitch)2
c) K’ (hole diameter/hole pitch)2
d) (Hole diameter) 2
Answer: c [Reason:] The fractional whole area on a sieve tray ranges from 0.05 to 0.15, this is given by K’ (hole diameter/hole pitch)2 and does not vary.
6. Find the fractional hole? If K’= 0.905, Hd=10 m2 and pitch is 5 m2
Answer: b [Reason:] As K’ (Hd/pitch)2 m2 = 0.905(10/5) 2 m2 = 3.62.
7. For the down comer backup, the quantity HW + HOW is called?
a) Kinematic liquid seal
b) Dynamic liquid seal
c) Static liquid seal
d) Tray liquid seal
Answer: c [Reason:] Where HW = is height of liquid over weir and HOW = sum of weir heights, down comer is also essential at a point of time.
8. The square root of kinetic energy is defined as?
Answer: a [Reason:] FH = u√p This factor is called as F-factor, this parameter is based on the hole velocity and the K’ value.
9. The C-Factor is defined as the ratio of?
Answer: c [Reason:] The C factor is related to VLOAD and the F factor as VLOAD/A where A is the area of the bubbling plate.
10. VLOAD, represents the
a) Virtual load
b) Visual load
c) Vector load
d) Vapor load
Answer: d [Reason:] VLOAD=CFS Where this term is inconvenient because it is based on vapor not on vapor velocity.
1. The expansion of liquid due to passage of vapor or gas is referred as?
Answer: d [Reason:] 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
Answer: d [Reason:] 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 [Reason:] 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 [Reason:] 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 [Reason:] 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.
Answer: a [Reason:] 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 [Reason:] 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 [Reason:] 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 [Reason:] 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 [Reason:] Weeping is indicated by a sharp pressure drop in the column and reduced separation efficiency, when liquid starts to leak through perforations.
1. Pressure drops per theoretical stage of Mellapak packing’s are?
a) 1.0 to 2.1 mbar
b) 0.3 to 1.0 mbar
c) 2.3 to 1.2 mbar
d) 5.6 to 7.3 mbar
Answer: b [Reason:] Pressure drop per theoretical stage is 0.3‑1.0 mbar and the pressure drop at 70‑80% flooding about 2 mbar/m while Minimum liquid load approx. is 0.2 m3/m2h.
2. Gauze packing’s have an F-factor of?
b) 5 √Pa
c) 1-2.5 √Pa
Answer: c [Reason:] Gauze packing’s have an F-factor of 1‑ 2.5 √Pa with pressure drop per theoretical stage as 0.1 – 0.5 mbar.
3. Mellacarbon packing have a surface area of nearly _______
a) 500 – 600 m2/m3
b) 800 – 1000 m2/m3
c) 125 – 700 m2/m3
d) 300 – 900 m2/m3
Answer: c [Reason:] Mellacarbon packing have a surface area of 125 – 700 m2/m3 and a high thermal stability of 400o C also excellent wettability in aqueous systems.
4. The phenomena of the flowing of liquid towards the wall of tower and dispersed in lateral direction is called as?
b) Flow casting
Answer: a [Reason:] This is called as channeling of liquid, such misdistribution is determined to a good gas liquid contact, therefore necessary to collect liquid from wall and give it to bed again.
5. The first structured packing was called as?
Answer: a [Reason:] Panapak was made from thin metal strips to form a honeycomb like structure did not gain much popularity because of severe maldistribution of liquid.
6. The abbreviation IMTP represents?
a) Intermediate Metal Thrus Packing
b) Inverse Metal Tertiary Packing
c) Intalox Metal Tower Packing
d) Indian Metal Tower Packing
Answer: c [Reason:] The Inverse Metal Tertiary Packing, a random packing developed of surface area of a pall ring and the aerodynamic shape of the Intalox saddle.
7. The Height to Diameter ratio of CMR is?
Answer: b [Reason:] CMR is similar to the pall ring but has a height to diameter ratio this is sometimes called the ‘aspect ratio’ of 1:3 compared to 1:1 latter.
8. The corrugation angle of sheets varies from
a) 28 to 45o
b) 30 to 45o
c) 90 to 120o
d) 55 to 67o
Answer: a [Reason:] The corrugation angle of sheets varies from 28 to 45o. Perforations are sometimes between the two surfaces of channels of communication between the two surfaces.
9. Sluzer supply are of which three types?
a) AX,CX and CV
b) AY,BX and CX
c) AY,CX and BX
d) AX,BX and CY
Answer: d [Reason:] Sluzer supply are of three types marked as AX,BX and CY, the packing elements are made of corrugated layers of mesh.
10. For Raschig rings, redistribution becomes necessary after a depth bed of
a) 3 to 6 inches
b) 1 to 3 inches
c) 7 to 8 inches
d) 5 to 9 inches
Answer: a [Reason:] For Raschig rings, redistribution is after 3 to 6 inches and for saddle packed tower it is 5 to 10 ft per section.
1. Which of the following shows the correct Gibbs phase rule equation?
Answer: a [Reason:] According to Gibb’s F=C-P+2 for any system, where F is degree of freedom, C is number of components and P is the number of phases.
2. The higher the concentration of volatile species, the distillation
a) The higher the rate of liquid flow
b) The lower the rate of Separation
c) The higher the rate of separation
d) Cannot be specified
Answer: c [Reason:] Volatility is directly proportional to the ease of separation (α) while it is inversely proportional to difficulty of separation.
3. VLE data once obtained is represented on which scale?
a) Binary Scale (0<x<1)
b) Pressure Scales (0<Pa<1)
c) Temperature Ranges (T1<x<T2)
d) Not specific
Answer: a [Reason:] Binary scales are most suitable as they represent mole fractions of the both species x* and y* at all conditions.
4. When the boiling temperature is plotted against the liquid composition, then it is called
a) Cooling Curve
b) Heating Curve
c) Bubble point curve
d) Volatility Phase Diagram
Answer: c [Reason:] The (T-x) curve is called as Bubble point Curve, Where T is boiling temperature and x is the mole fraction of the liquid.
5. When the temperature is plotted against the equilibrium vapor, then it is called
a) Condensing Curve
b) Dew Point curve
c) Equilibrium Curve
d) Bubble Curve
Answer: b [Reason:] The (T-y*) curve is called as Dew point Curve, Where T is boiling temperature, and y is the equilibrium moles of the gaseous components.
6. The K value can be expressed as
Answer: d [Reason:] The ratio of mole fraction of components in vapor and liquid phase is called as K value.
7. The Relative Volatility of components i and j can be defined as
Answer: a [Reason:] The ratio of K values is defined as the relative volatility, Where Ki is the gaseous components and Kj is the fluid components.
8. Given that αAB=2.0, Then equilibrium ratio of B is KB=0.7, Estimate αBA ?
Answer: c [Reason:] As α=KB/KA, 2.0= 0.7/KA, KA = 0.35 and αAB =KA/KB =0.35/0.7 = 0.5.
9. Which system can be said as an Ideal system that obeys?
a) Henrys Law
b) Daltons Law
c) Phase Rule
d) Cremer’s rule
Answer: d [Reason:] The system that obeys Henry’s and Dalton’s Law is called an ideal system, as they are derived from the ideal gas relation PV=Nrt.
10. Which of the below is the Dalton’s Law?
a) pi = yi/P
b) x = yi/ pi
c) pi = yi/x
d) pi = xi/y
Answer: a [Reason:] According to Dalton’s law the partial pressure of component is solution is equal to product of its mole fraction and vapor pressure of pure components.
1. The method of construction of an x-y diagram was explained by
a) Richardson and Coulson
b) Robinson and Gilliland
c) Murphree and Fenske
d) Cremer and Pullong
Answer: b [Reason:] Pseudo properties were given by Robinson and Gilliland, while Murphree and Fenske gave equations to calculate trays and efficiency respectively.
2. Consider the following data, L’ = 363 and slope of section is 1.55. Estimate Vapor flow rate on either side
Answer: a [Reason:] The slope is given by L’/V’=1.55, V’ = 363/1.55 = 234.
3. The point where equilibrium curve and component balance meets is called as
a) Murphree point.
b) Intersection point
c) Junction point
d) Pinch point
Answer: d [Reason:] At infinite stages the where equilibrium curve and component balance meets is called as pinch point.
4. HETP is defined?
a) Height equivalent to theoretical plate
b) High efficiency tower plate
c) High energy temperature point
d) Homotomy Engineer Temperature Point
Answer: a [Reason:] HETP is Height equivalent to theoretical plate, also defined as ratio of HTU (height of transfer units) and NTU.
5. The condition where reflux and stripping ratio approaches to infinity is called as
a) Minimum reflux
b) Total reflux
c) Optimum ratio
d) Feed ratio
Answer: b [Reason:] Both balance lines approaches to coincide such a condition is called Total reflux, the slope of rectifying and stripping line matches each other.
6. Which of following is an important assumption of McCabe Thiele method?
a) Heat loss is maximum
b) Heat loss is negligible
c) Heat loss is infinite
d) Can’t be specified
Answer: b [Reason:] The major assumption of McCabe Thiele method is Heat loss is negligible and also an overhead reboiler and condenser are used to recover heat loss.
7. In which case Constant Molar overflow is true?
a) Equimolar counter diffusion
b) Equimolar co-current diffusion
c) Distinct overflow
d) Not Sure of Diffusion
Answer: a [Reason:] CMO is totally based on the assumption of equal-molar counter diffusion, mainly used in the calculation of trays in the McCabe Thiele method.
8) In McCabe Thiele method, equilibrium line is drawn between
c) x*- y
Answer: a [Reason:] The equilibrium is always drawn between x-y mole ratios, where x is mole of liquid feed and y is the mole of gas at equilibrium conditions.
9. The equilibrium line is plotted on the graph at
a) Middle of both sections
b) 900 from stripping section
c) 450 from axis meet up
d) At meetup of axis
Answer: c [Reason:] Equilibrium line is always plotted between axes at 450, while the 90 0 perpendicular is used to find the feed point on x-y graph.
10. The tray by tray approach method was given by
Answer: a [Reason:] The oldest method of calculation was given by Sorel in 1893, Murphree gave equations for efficiency, Fenske for the minimum trays.