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# Multiple choice question for engineering

## Set 1

1. In the packed bed, at relatively low flow rates pressure drop is approximately proportional to gas velocity, true or false?
a) True
b) False

Answer: a [Reason:] From Umf expression, this relation has peen taken.

2. Before the pressure drop stabilizes after the bed gets fluidized, what is the position of pressure drop before reaching minimum fluidization?
a) Above the constant
b) Below the constant
c) Equal
d) Hard to tell

Answer: a [Reason:] Since it requires extra pressure during the particles are lifted in air.

3. How the gas behave across the fluidized bed, when the velocity is more than minimum fluidization?
a) Bubbles formation
b) Slugs formation
c) Smooth flow
d) None of the mentioned

Answer: a [Reason:] Since we have voids formed, the gas try to form bubbles while passing through the bed.

4. How the liquid behave across the fluidized bed, when the velocity is more than minimum fluidization?
a) Bubbles formation
b) Slugs formation
c) No bubbles
d) None of the mentioned

Answer: c [Reason:] Since we have no voids formed, the liquid forms smooth flow in the bed.

5. What happens if we continuously increase the velocity after attaining the constant pressure drop?
a) Remains constant
b) Pressure drop decreases to zero
c) Slight reduction in pressure drop
d) Slight increase in pressure drop

Answer: b [Reason:] Increasing velocity further makes the particles lift off completely and hence the pressure drop reduces completely to zero.

6. When the velocity of fluid is infinity, the pressure drop goes to zero, give example of its physical application?
a) Pneumatic conveyors
b) Dilution of solids
c) Transportation
d) All of the mentioned

Answer: d [Reason:] Since the velocity of fluid is high, the particles are carried away and used for mostly transportation purpose.

7. During the increase of velocity of fluid in the bed, how does the graph of pressure drop follows?
a) Linear
b) Exponential
c) Non-linear
d) None of the mentioned

Answer: a [Reason:] Till the velocity of gas balances the weight of the particles the growth is linear.

8. When does the initiation of entrainment start in the fluidized bed?
a) Before the pressure drop goes to zero
b) Point when pressure drop becomes constant
c) Start of the fluidization process
d) None of the mentioned

Answer: a [Reason:] When the velocity goes high the particles start lifting up, it is the point when the entrainment has started.

9. What is one of the reason for poor fluidization beds in terms of pressure drop?
a) Slugging
b) Low velocity
c) Light particles
d) All of the mentioned

Answer: a [Reason:] Slug formation leads to irregular distribution of pressure drop in the bed.

10. What does the minimum fluidization velocity in the bed depends on?
a) Size distribution of solids
b) Pumping power
c) Diameter of bed
d) All of the mentioned

Answer: d [Reason:] Solids size, power and diameter are considered while calculating the minimum fluidization velocity.

## Set 2

1. Fluidization occurs when: Drag force by the upward moving gas ________
a) Weight of the particle
b) Weight of the fluid
c) Volume of the bed
d) Pressure drop across bed

Answer: a [Reason:] Drag force by the upward moving gas = Weight of the particle.

2. What is the range of Reynolds number(Re) for small particles in the fluidization bed?
a) Re < 20
b) Re > 20
c) 20 < Re > 1000
d) 20 > Re < 1000

Answer: a [Reason:] Since smaller particles require less velocity of gas to lift the particles, hence the Re is low.

3. What is the range of Reynolds number(Re) for small particles in the fluidization bed?
a) Re < 20
b) Re > 20
c) Re > 1000
d) 20 > Re < 1000

Answer: c [Reason:] Since larger particles require large velocity of gas to lift the particles, hence the Re is large.

4. Fluidization expression is compared with which equation from fluid mechanics?
a) Euler’s equation
b) Bernoulli’s equation
c) Buoyancy equation
d) Navierâ€“Stokes equation

Answer: a [Reason:] Because the Euler’s equation is analogous to Fluidization equation.

5. Minimum Fluidizing equation can be expressed in terms of which physical quantity?
a) Pressure drop
b) Temperature
c) Velocity
d) Volume

Answer: a [Reason:] Since pressure drop is required to find the exact velocity of gas required to keep the particles floating.

6. What is the sphericity of sharp sand particles?
a) 0.67
b) 0.86
c) 0.63
d) 0.58

Answer: a [Reason:] Based on the data from the Voidage table at Minimum fluidizing conditions.

7. What is the sphericity of round sand particles?
a) 0.67
b) 0.86
c) 0.63
d) 0.58

Answer: b [Reason:] Based on the data from the Voidage table at Minimum fluidizing conditions.

8. What is the sphericity of anthracite coal particles?
a) 0.67
b) 0.86
c) 0.63
d) 0.58

Answer: c [Reason:] Based on the data from the Voidage table at Minimum fluidizing conditions.

9. What is the sphericity of Fisher-catalyst particles?
a) 0.67
b) 0.86
c) 0.63
d) 0.58

Answer: d [Reason:] Based on the data from the Voidage table at Minimum fluidizing conditions.

10. On comparison with Fluidized bed and Packed bed, which has the highest voidage?
a) Fluidized bed
b) Packed bed
c) Pressure drop
d) All of the mentioned

Answer: a [Reason:] Fluidized bed has little larger voids compared to packed bed.

## Set 3

1. North America has vast deposits of oil-bearing rock, called shale, true of false?
a) True
b) False

Answer: a [Reason:] These rocks which provide them with oil.

2. What kind of designs were proposed for extracting oil from rocks?
a) In situ extraction
b) Moving bed processes
c) Fluidized bed
d) All of the mentioned

Answer: d [Reason:] They are suggested in order to provide oil economically.

3. What is the main reason for suggesting fluidized bed for oil extraction?
a) Low oil content
b) High oil content
c) Presence of impurities
d) None of the mentioned

Answer: a [Reason:] Since is oil content is low, fluidization is the cheapest method for extracting the most oil.

4. At what temperature is the retort maintained in the fluidized bed for oil recovery?
a) 370-530 C
b) 120-250 C
c) 700-900 C
d) None of the mentioned

Answer: a [Reason:] It is optimum temperature for evaporation of oil.

5. How is oil shale recovered from the fluidized plant?
a) Cooling the steam
b) Heating the oil
c) Filtration of steam
d) All of the mentioned

Answer: a [Reason:] On condensation, the shale gets separated from the steam and then collected at the bottom.

6. What is the important factor in the overall economics of recovery of shale?
a) Efficient heat recovery
b) Efficient oil recovery
c) Efficient coal recovery
d) All of the mentioned

Answer: d [Reason:] They are important for best overall economics.

7. How much % does the inorganic material constitute in the solid feed?
a) 22
b) 44
c) 66
d) 88

Answer: d [Reason:] To get efficient heat recovery.

8. Temperature of coal after heating to higher temperatures, still maintained below coking temperature, true or false?
a) True
b) False

Answer: a [Reason:] In order to get high yield of oil.

9. How many beds does the recovery of oil from oil shale consists of?
a) 1
b) 2
c) 3
d) 4

Answer: c [Reason:] To have three systems, one for cracking, other as heating, last as condenser.

10. A four-stage pilot plant was developed having _______ capacity of feed in order to get high yields of oil?
a) 45 kg/hr
b) 65 kg/hr
c) 20 kg/hr
d) 50 kg/hr

Answer: a [Reason:] Optimum feed for best oil yield.

## Set 4

1. Researchers have been trying to replace Blast furnace with fluidized bed, true or false?
a) True
b) False

Answer: a [Reason:] In order to develop iron and steel from fines, fluidized bed was considered.

2. In order to prevent the sticking of ore, what conditions were developed in the reactor bed?
a) High pressure
b) Low temperature
c) Moderate reaction rate
d) All of the mentioned

Answer: d [Reason:] High temperature leads to sticking of ore, hence reducing temperature, thereby increasing pressure leading to moderate reaction rates were incorporated.

3. Which gas is used to develop pressure in the reactor bed?
a) Hydrogen
b) Nitrogen
c) Oxygen
d) Steam

Answer: a [Reason:] Hydrogen provides sufficient high pressure conditions.

4. What are the percentage of reduced ore taken out starting from bottom?
a) 98, 87, 47%
b) 47, 78, 98%
c) 74, 87, 89%
d) 74, 87, 98%

Answer: a [Reason:] At the bottom of bed, the conversion is the most, as we go above the conversion percentage decreases.

5. How much hydrogen is being converted on reaction with iron?
a) 1%
b) 5%
c) 10%
d) 15%

Answer: b [Reason:] On evaluation, 5% of hydrogen was reacting with iron to liberate water vapour.

6. What is the main reason for usage of blast furnace over hydrogen reduction process?
a) Unavailability
b) High cost of production
c) Costlier than Blast furnace
d) All of the mentioned

Answer: d [Reason:] Because of low availability and high cost of production, it is blast furnace is prefered.

7. Process developed by Cronan, consists of two-stage continuous reactor, true or false?
a) True
b) False

Answer: a [Reason:] This process contains two-stage continuous reactor at 3.5 atm.

8. What is the conversion rate in two-stage continuous reactor?
a) 80-85%
b) 90-95%
c) 70-75%
d) 75-80%

Answer: b [Reason:] Process conditions selected such that the conversion was found to be 90-95%.

9. What is the diameter of reactor developed by Bethlehem steel company?
a) 1.7m ID
b) 2.1m ID
c) 1.5m ID
d) 1.2m ID

Answer: a [Reason:] From the literature, it was found that reactor diameter is 1.7m ID.

10. What is the height of reactor developed by Bethlehem steel company?
a) 29m
b) 30m
c) 31m
d) 32m

Answer: a [Reason:] From the literature, it was found that reactor height is 29m.

## Set 5

1. What is the main reason for using solid catalyst gas phase reactions in fluidized bed?
a) Temperature control
b) Increase desired product to side product
c) Reduction in hotspots of catalyst
d) All of the mentioned

Answer: d [Reason:] They are therefore useful for temperature control and other reasons.

2. Which kind of flow is preferred in the fluidized reactor for production of ethylene oxide?
a) Plug flow
b) Batch reactor
c) Mixed flow
d) Cross flow

Answer: a [Reason:] Because this allow maximum yield of the reaction intermediate.

3. Why is the boiling downtherm used to surround the long narrow tubes, in the fluidized bed for production of ethylene oxide?
a) Give good temperature control
b) Help in temperature fluctuations
c) Fasten the reaction process
d) None of the mentioned

Answer: a [Reason:] Because it acts as a coolant which helps in temperature control.

4. What happens if we use a heater for eg. steam instead of a downtherm, in the fluidized bed for production of ethylene oxide?
a) Reactor may explode
b) Helps in better temperature control
c) Nothing will happen
d) Reaction might change

Answer: a [Reason:] Since the reaction is already highly exothermic, addition of heat will worsen the situation.

5. What happens if there is no narrow tubes in the fluidized bed for the production of ethylene oxide?
a) Leads to less intermediate yield
b) Leads to maximum yield of reaction intermediate
c) No effect on the reaction
d) None of the mentioned

Answer: a [Reason:] Since the reaction is exothermic, it need to be controlled which is only possible in plug flow with the help of downtherm.

6. In the HCl oxidation process, a slurry of catalyst fines in aqueous HCl is injected into the bed as?
a) Feed
b) Coolant
c) For temperature control
d) All of the mentioned

Answer: d [Reason:] Slurry is therefore used as feed, as coolant and for proper temperature control.

7. What will happen if the concentration of naphthaquinone builds up in the fluidized bed for phthalic anhydride production?
a) Reaction will explode
b) Helps in temperature control
c) Acts as coolant
d) None of the mentioned

Answer: a [Reason:] Since the reaction is highly exothermic.

8. Why is the liquid naphthalene fed through nozzles directly to the bottom of the reactor, in the fluidized bed for phthalic anhydride production?
a) Liquid is immediately vaporized
b) Liquid is immediately cooled
c) Liquid is immediately solidified
d) None of the mentioned

Answer: a [Reason:] According to Graham and Way, the liquid vaporizes on injecting through nozzle.

9. In the reaction of naphthalene to phthalic anhydride, what is the intermediate formed?
a) Naphthaquinone
b) Nascent oxygen
c) Naphtha-quinine
d) None of the mentioned

Answer: a [Reason:] Based on the analysis, it was found that naphthaquinone is the reaction intermediate.

10. What are the by-products present in the HCl oxidation process?
a) Chlorine gas, water vapour
b) Ammonia gas
c) Chloroform
d) None of the mentioned