Multiple choice question for engineering

Set 1

1. Why was fluidized bed not used commercially for production of gasoline from natural gas?
a) Conversion was below par
b) Scale-up was difficult
c) Back-mixing
d) All of the mentioned

Answer

Answer: d [Reason:] Fluidized bed was not possible because of less conversion, scale up problem.

2. Why was conversion in the production of gasoline in fluidized bed was less?
a) Back-mixing and by-passing
b) Recycling
c) Regeneration
d) None of the mentioned

Answer

Answer: a [Reason:] Back-mixing and by-passing are undesirable for gasoline production.

3. What is the main reason for lower efficiencies in the commercial operations of synthetic reactions through fluidized beds?
a) Gas bypassing
b) Backing mixing
c) Bubble behaviour
d) All of the mentioned

Answer

Answer: d [Reason:] Serious gas by-passing, back mixing and irregular bubble behaviour leads in lowering the efficiencies in fluidized beds.

4. Why are electrodes placed in resistance-heated fluidized bed?
a) Achieve high temperatures
b) Acts as heat transfer surface
c) Helps in magnetizing the metallic particles
d) None of the mentioned

Answer

Answer: a [Reason:] To maintain very high temperatures through passing high density current through electrically conductive material.

5. Operating conditions and feed ratios are different for all these processes, however, conversion of limiting reagent, acetic acid is roughly 50-70%, true or false?
a) True
b) False

Answer

Answer: a [Reason:] Based on experiments conducted by Du pont company.

6. In the dilute phase reacting system, reacting gases carry suspended catalyst through tubes of a vertical heat exchanger with velocity of?
a) 3 to 12 m/s
b) 12 to 24 m/s
c) 1 to 3 m/s
d) 0.1 to 10 m/s

Answer

Answer: a [Reason:] This range of velocity provides relevant driving force for smooth circulation of powdered catalyst.

7. What is the mesh range that the catalytic reactor for vinyl acetate developed by Du pont uses?
a) 30 to 150 mesh
b) 150 to 200 mesh
c) 10 to 50 mesh
d) 200 to 300 mesh

Answer

Answer: a [Reason:] Optimum range to prevent elutrition and avoiding bubble cap blockage.

8. Kellogg company developed a synthetic gasoline plant based on dilute phase transfer line, works on the principle of circulation system for the solids, true or false?
a) True
b) False

Answer

Answer: a [Reason:] They developed such fluidized bed which works on principle of circulation system for solids.

9. In Sohio process, after fluidized bed, instead of several separation units, why cant we use a single distillation column?
a) Difficult to separate
b) Economics
c) Space factor
d) None of the mentioned

Answer

Answer: a [Reason:] Since the boiling points of the end products are very close, distillation columns cannot be used to separate them.

10. What is the role of cone shaped structure in the Du pont catalytic reactor?
a) Gas distribution
b) To occupy empty space
c) To prevent attrition
d) For better fluidization

Answer

Answer: a [Reason:] Cone helps in gas distribution for better gas-solid contact and eliminate gas bypassing.

Set 2

1. What is the time required for complete coating to take place in the fluidized bed?
a) 2-3 sec
b) 5-10 sec
c) 1 sec
d) 20 sec

Answer

Answer: a [Reason:] It is optimum time, if more than that coating will be irregular and less than that incomplete coating will take place.

2. Which variety of plastic powders can be used for metal ware coating?
a) Polyvinyl
b) Polypropylene
c) Polyvinyl Chloride
d) All of the mentioned

Answer

Answer: d [Reason:] Any plastic material can be used.

3. For coating using plastic in fluidized bed, thermoplastic powders are always used, true or false?
a) True
b) False

Answer

Answer: a [Reason:] If there is any irregular coating, thermoplastics can be remoulded.

4. What will happen if the metal ware is kept for long time for coating of polymer in the fluidized bed?
a) Better coating
b) Irregular thickness
c) Time is independent of time
d) None of the mentioned

Answer

Answer: b [Reason:] More time it stays more irregular the coating.

5. What is the best method for application of plastic coating on the metal coating?
a) Fluidized bed
b) Spray
c) Electrostatic painting
d) Brush

Answer

Answer: a [Reason:] Best work possible with cheaper cost and less time required.

6. What should be the temperature of the metal ware for best coating to occur?
a) Little more than the melting point of the polymer
b) Same as melting point temperature of the polymer
c) Very high temperature
d) None of the mentioned

Answer

Answer: a [Reason:] Little more energy for melting the plastic and still remaining hot.

7. According to Gaynor, how is the thickness of the film varies with time?
a) Exponentially
b) Linearly
c) Independent
d) Sinusoidally

Answer

Answer: a [Reason:] Based on research done by Gaynor, he concluded relation is exponential.

8. Since the rate of deposition is proportional to the rate of heat transfer, thickness varies exponentially with film, true of false?
a) True
b) False

Answer

Answer: a [Reason:] Based on results provided by Gaynor.

9. In below fig, if the coolants are not present in the fluidized bed, how will it effect the film formation?

a) Molten plastic will drip down from the metal ware
b) No effect on the film formation
c) Increases the cooling the period
d) None of the mentioned

Answer

Answer: a [Reason:] Coolant is required to cool the plastic for film formation.

10. If the flow rate of coolants is increased in the fluidized bed, how will it effect the film formation?
a) Time duration of film formation will decreased
b) No effect
c) Time duration for film formation increases
d) None of the mentioned

Answer

Answer: a [Reason:] Duration for cooling will increase and hence for short duration for film formation.

Set 3

1. What are the methods for measuring large particles of size above 5mm?
a) Calliper
b) Micrometer
c) Sieves
d) All of the mentioned

Answer

Answer: d [Reason:] All are used for measuring solid particles based on different principles.

2. What are the methods used for measuring particles of size < 0.04mm?
a) Settling rate
b) Brownian movement
c) Sieve analysis
d) All of the mentioned

Answer

Answer: d [Reason:] All are used for measuring solid particles based on different principles.

3. What does ‘-‘ sign mean in the following expression: – 150 + 200 mesh particles?
a) Pass through 150
b) Doesnt pass through 150
c) Pass through 200
d) None of the mentioned

Answer

Answer: a [Reason:] It represents particles which pass through 150 mesh.

4. What does ‘+’ sign mean in the following expression: – 150 + 200 mesh particles?
a) Pass through 200
b) Retained on 200
c) Retained on 150
d) None of the mentioned

Answer

Answer: b [Reason:] It represents particles which are retained on 200 mesh.

5. What is the relationship between sphericity and voidage?
a) Sphericity=(6(1-voidage))/(a*dp)
b) Voidage=(6(1-sphericity))/(a*dp)
c) Sphericity=(6*voidage)/(a*dp)
d) Voidage=(6*sphericity)/(a*dp)

Answer

Answer: a [Reason:] From the literature and formula derivation, the relation has been developed.

6. According to Brown, fractional voids in the packed bed are related to ___________ of particles?
a) Shape
b) Size
c) Sphericity
d) None of the mentioned

Answer

Answer: c [Reason:] From the literature, fractional voids in the packed bed are related to sphericity of particles.

7. The pressure drop through the fixed beds of uniformly sized solids has been correlated by ________
a) Ergun equation
b) Poisson equation
c) Laplace equation
d) None of the mentioned

Answer

Answer: a [Reason:] The pressure drop through the fixed beds has been correlated by Ergun equation.

8. Which factor is considered in Ergun equation when the Reynolds number is less 20?
a) 150
b) 1.75
c) 2.75
d) 250

Answer

Answer: a [Reason:] Since viscous forces predominate, 150 factor is considered.

9. Which factor is considered in Ergun equation when the Reynolds number is greater than 1000?
a) 150
b) 1.75
c) 2.75
d) 250

Answer

Answer: b [Reason:] Since kinetic losses are considered, 150 factor is considered.

10. Which new term is utilized for measuring non spherical particles?
a) Sphericity
b) Volume displacement
c) Geometry
d) None of the mentioned

Answer

Answer: a [Reason:] This new term is used to express the sphericity of non-spherical particles.

Set 4

1. What is the low-temperature range maintained to activate charcoal?
a) 100-200 Celsius
b) 400-500 Celsius
c) 800-900 Celsius
d) None of the mentioned

Answer

Answer: c [Reason:] It is the optimum temperature required for activating charcoal.

2. In order to activate charcoal, what are the gases used?
a) Steam and carbon dioxide
b) Steam and oxygen
c) Oxygen and carbon dioxide
d) Steam and water vapour

Answer

Answer: a [Reason:] Steam and carbon dioxide help in maintaining the temperature and activating charcoal.

3. The fluidized bed utilized for this operation is multi-stage, true or false?
a) True
b) False

Answer

Answer: a [Reason:] Since it gives more residence time distribution for the solids.

4. In order to help recover heat for the endothermic gasification reaction by secondary combustion of CO and hydrogen, the fluidized bed must have?
a) Multiple stages
b) Single stage
c) Two fluidized beds in series
d) None of the mentioned

Answer

Answer: a [Reason:] Since it provides the sufficient time for recovery of heat.

5. How much percentage the density of solids drop during gasification?
a) 1 to 5%
b) 5 to 10%
c) 15 to 20%
d) 25 to 30%

Answer

Answer: c [Reason:] Gasification reduces their density about 15 to 20% without changing their size.

6. In place of two-stage fluidized bed, is there possibility of increasing its stages?
a) Yes
b) No
c) Depending on economy
d) None of the mentioned

Answer

Answer: c [Reason:] In order to maintain the economic budget and space provided, one can decide the number of stages to incorporated.

7. What is injected in the combustion chamber at the bottom of fluidized bed?
a) Steam
b) Air
c) Recycled steam
d) All of the mentioned

Answer

Answer: d [Reason:] Steam and air are utilized for combustion to take place and help in activating charcoal.

8. What are raw materials used for charcoal during its gasification?
a) Wood
b) Peanut shells
c) Pulverized coal
d) All of the mentioned

Answer

Answer: d [Reason:] All are the sources of charcoal, hence they are utilized for gasification process.

9. If the temperature for gasification is maintained about 500 degree Celsius, then activation of charcoal is not take place, true of false?
a) True
b) False

Answer

Answer: a [Reason:] It requires minimum temperature of 800-900 for its activation.

10. Which gas is used for fluidizing the material on the distributor?
a) Steam
b) Air
c) Carbon dioxide
d) None of the mentioned

Answer

Answer: a [Reason:] Since it helps maintain temperature as well as fluidize the material.

Set 5

1. What is the Reynolds number range when the drag coefficient formula is 24/(Rep)?
a) Rep < 0.4
b) 0.4 < Rep < 500
c) 500 < Rep < 200,000
d) None of the mentioned

Answer

Answer: a [Reason:] Range is taken based on the experimental values.

2. What is the Reynolds number range when the drag coefficient formula is 10/(Rep)^0.5?
a) Rep < 0.4
b) 0.4 < Rep < 500
c) 500 < Rep < 200,000
d) None of the mentioned

Answer

Answer: b [Reason:] Range is taken based on the experimental values.

3. What is the Reynolds number range when the drag coefficient formula is 0.43?
a) Rep < 0.4
b) 0.4 < Rep < 500
c) 500 < Rep < 200,000
d) None of the mentioned

Answer

Answer: c [Reason:] Range is taken based on the experimental values.

4. The velocity of fluid is operated between minimum fluidizing velocity(Umf) and Pneumatic velocity in fluidized bed, true or false?
a) True
b) False

Answer

Answer: b [Reason:] It is operated between minimum fluidizing velocity and terminal velocity(Ut) in fluidized bed.

5. What is the range of Ut/Umf for flexible operation of the fluidized bed?
a) 10:1 to 90:1
b) 5:1 to 10:1
c) 90:1 to 120:1
d) 120:1 to 200:1

Answer

Answer: a [Reason:] This range provides best conditions for fluidization without much entrainment.

6. When the bed is just fluidized the height attained is maximum, true or false?
a) True
b) False

Answer

Answer: a [Reason:] Because after that height, the further increase in velocity will definitely lead to entrainment of some particles.

7. For fine solids Reynolds number should be less than?
a) 0.4
b) 4
c) 40
d) 400

Answer

Answer: a [Reason:] Since the size of particles is small, the velocity will be comparatively small. Hence the range also reduces.

8. For large solid particles Reynolds number should be greater than?
a) 10
b) 100
c) 1000
d) 10000

Answer

Answer: c [Reason:] Since the size of particles is large, the velocity will be comparatively large. Hence the range also increases.

9. When the diameter is narrower of the bed, which kind of problem is most likely to occur in the bed?
a) Chanelling
b) Slugging
c) Entrainment
d) None of the mentioned

Answer

Answer: b [Reason:] Slugging occurs due to coagulation of air bubbles without breaking.

10. What can be done in order to prevent slugging in the fluidized bed?
a) Baffles
b) Increase diameter
c) Proper design of distributor
d) All of the mentioned

Answer

Answer: d [Reason:] Placing baffles will break the bubbles, increasing the diameter will reduce chances of slugging, distributor design also decides the slugging factor.