Minimum porosity for fluidisation is(A) That corresponding to static bed (B) That corresponding to completely fluidised bed (C) The porosity of the bed when true fluidisation begins (D) Less than that of the' static bed

Minimum porosity for fluidisation is
(A) That corresponding to static bed
(B) That corresponding to completely fluidised bed
(C) The porosity of the bed when true fluidisation begins
(D) Less than that of the' static bed
by

1 Answer

Answer :

(C) The porosity of the bed when true fluidisation begins
by

Related questions

A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle system (in SI units) is given below : Δ P/L = 375 × 10 3 VOM + 10.94 × 10 6 V2 OM (SI units) If water is to be used as the fluidising medium, the minimum fluidisation velocity, VOM is (A) 12 mm/s (B) 16 mm/s (C) 24 mm/s (D) 28 mm/s

Description : A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle ... fluidisation velocity, VOM is (A) 12 mm/s (B) 16 mm/s (C) 24 mm/s (D) 28 mm/s

Last Answer : (B) 16 mm/s

. A 0.5 m high bed made up of a 1 mm dia glass sphere (density 2500 kg/m3 ) is to be fluidised by water (density 1000 kg/m3 ). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is (A) 4.4 KPa (B) 2.94 KPa (C) 3.7 KPa (D) None of these

Description : . A 0.5 m high bed made up of a 1 mm dia glass sphere (density 2500 kg/m3 ) is to be fluidised by water (density 1000 kg/m3 ). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is (A) 4.4 KPa (B) 2.94 KPa (C) 3.7 KPa (D) None of these

Last Answer : (A) 4.4 KPa

When larger particles e.g., grains are subjected to fluidisation, the corresponding bed produced is termed as the __________ bed. (A) Spouted (B) Sluggish (C) Boiling (D) Teeter

Description : When larger particles e.g., grains are subjected to fluidisation, the corresponding bed produced is termed as the __________ bed. (A) Spouted (B) Sluggish (C) Boiling (D) Teeter

Last Answer : (A) Spouted

Bed pressure drop in an air fluidised bed of catalyst particles (ρp = 200 kg/m3, Dp = 0.05 cm) of 60 cm bed depth and bed porosity of 0.5 expressed in cm of water (manometer) is (A) 90 (B) 60 (C) 45 (D) 30

Description : Bed pressure drop in an air fluidised bed of catalyst particles (ρp = 200 kg/m3, Dp = 0.05 cm) of 60 cm bed depth and bed porosity of 0.5 expressed in cm of water (manometer) is (A) 90 (B) 60 (C) 45 (D) 30

Last Answer : (B) 60

A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle system (in SI units) is given below: Δ P/L = 375 × 10 3 VOM + 10.94 × 10 6 V2 OM (SI units) If water is to be used as the fluidising medium, in actual operation, the above bed has a height = 1 m. What is the porosity of the fluidised bed? (A) 0.2 (B) 0.5 (C) 0.7 (D) 0.8

Description : A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle system ... What is the porosity of the fluidised bed? (A) 0.2 (B) 0.5 (C) 0.7 (D) 0.8

Last Answer : (C) 0.7

With decrease in particle size to be fluidised by a particular fluid, the operating range of fluidisation velocity (A) Widens (B) Squeezes (C) Does not change (D) Unpredictable from the data

Description : With decrease in particle size to be fluidised by a particular fluid, the operating range of fluidisation velocity (A) Widens (B) Squeezes (C) Does not change (D) Unpredictable from the data

Last Answer : (C) Does not change

Umf is the minimum fluidisation velocity for a bed of particles. An increase in the superficial gas velocity from 2 Umf to 2.5 Umf results in (all velocities are smaller than the entrainment velocity of the particles) nochange in the(A) Drag on particles(B) Drag on column walls(C) Bed height(D) Bed voidage

Description : Umf is the minimum fluidisation velocity for a bed of particles. An increase in the superficial gas velocity from 2 Umf to 2.5 Umf results in (all velocities are smaller than the entrainment velocity of the particles ... (A) Drag on particles (B) Drag on column walls (C) Bed height (D) Bed voidage

Last Answer : (C) Bed height

In continuous fluidisation (A) Solids are completely entrained (B) The pressure drop is less than that for batch fluidisation (C) There is no entrainment of solids (D) Velocity of the fluid is very small

Description : In continuous fluidisation (A) Solids are completely entrained (B) The pressure drop is less than that for batch fluidisation (C) There is no entrainment of solids (D) Velocity of the fluid is very small

Last Answer : (A) Solids are completely entrained

Pressure drop in a fluidised bed reactor is __________ that in a similar packed bed reactor. (A) Less than (B) Greater than (C) Same as (D) None of these

Description : Pressure drop in a fluidised bed reactor is __________ that in a similar packed bed reactor. (A) Less than (B) Greater than (C) Same as (D) None of these

Last Answer : (B) Greater than

Which of the following is not applicable to fluidised bed combustion of coal? (A) It cannot burn low grade coal (B) It achieves higher fuel combustion efficiency (C) Less heat transfer surface area is required in boilers (D) None of these

Description : Which of the following is not applicable to fluidised bed combustion of coal? (A) It cannot burn low grade coal (B) It achieves higher fuel combustion efficiency (C) Less heat transfer surface area is required in boilers (D) None of these

Last Answer : (A) It cannot burn low grade coal

In a fluidised bed reactor (A) Temperature gradients are very high (B) Temperature is more or less uniform (C) Hot spots are formed (D) Segregation of the solids occurs

Description : In a fluidised bed reactor (A) Temperature gradients are very high (B) Temperature is more or less uniform (C) Hot spots are formed (D) Segregation of the solids occurs

Last Answer : (B) Temperature is more or less uniform

Minimum fluidisation velocity for a specific system depends upon the (A) Particle size (B) Fluid viscosity (C) Density of both the particle & the fluid (D) All (A), (B) and (C)

Description : Minimum fluidisation velocity for a specific system depends upon the (A) Particle size (B) Fluid viscosity (C) Density of both the particle & the fluid (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

For liquid flow through a packed bed, the superficial velocity as compared to average velocity through the channel in the bed is (A) More (B) Less (C) Equal (D) Independent of porosity

Description : For liquid flow through a packed bed, the superficial velocity as compared to average velocity through the channel in the bed is (A) More (B) Less (C) Equal (D) Independent of porosity

Last Answer : (B) Less

. Which of the following is used as a catalyst in fluidised bed catalytic cracking? (A) Silica-magnesia (B) Silica-alumina (C) Bentonite clays (D) All (A), (B) and (C

Description : . Which of the following is used as a catalyst in fluidised bed catalytic cracking? (A) Silica-magnesia (B) Silica-alumina (C) Bentonite clays (D) All (A), (B) and (C

Last Answer : (D) All (A), (B) and (C

. The most widely used crude topping column in refineries is the__________ column.(A) Bubble-cap(B) Packed bed(C) Fluidised bed(D) Perforated plate

Description : . The most widely used crude topping column in refineries is the__________ column. (A) Bubble-cap (B) Packed bed (C) Fluidised bed (D) Perforated plate

Last Answer : (A) Bubble-cap

Thermofor catalytic cracking process is a __________ process. (A) Fixed bed (B) Moving bed (C) Fluidised bed (D) Non-catalytic

Description : Thermofor catalytic cracking process is a __________ process. (A) Fixed bed (B) Moving bed (C) Fluidised bed (D) Non-catalytic

Last Answer : (D) Non-catalytic

Platforming is a __________ process. (A) Moving bed (B) Fluidised bed (C) Non-regenerative & fixed bed (D) Regenerative

Description : Platforming is a __________ process. (A) Moving bed (B) Fluidised bed (C) Non-regenerative & fixed bed (D) Regenerative

Last Answer : (C) Non-regenerative & fixed bed

Which of the following is the most widely used cracking process in oil refineries? (A) Dubbs process (B) T.C.C. moving bed process (C) Fluidised bed catalytic cracking process (D) Houdry's fixed bed process

Description : Which of the following is the most widely used cracking process in oil refineries? (A) Dubbs process (B) T.C.C. moving bed process (C) Fluidised bed catalytic cracking process (D) Houdry's fixed bed process

Last Answer : (C) Fluidised bed catalytic cracking process

Sticky material can be dried in a __________ dryer. (A) Tray (B) Rotary (C) Fluidised bed (D) None of these

Description : Sticky material can be dried in a __________ dryer. (A) Tray (B) Rotary (C) Fluidised bed (D) None of these

Last Answer : (A) Tray

Sand is dried in foundries in a _________drier. (A) Rotary (B) Fluidised bed (C) Vacuum (D) Spray

Description : Sand is dried in foundries in a _________drier. (A) Rotary (B) Fluidised bed (C) Vacuum (D) Spray

Last Answer : (B) Fluidised bed

Which of the following is not a batch drier? (A) Truck drier (B) Agitated pan drier (C) Fluidised bed drier (D) Vacuum shelf drier

Description : Which of the following is not a batch drier? (A) Truck drier (B) Agitated pan drier (C) Fluidised bed drier (D) Vacuum shelf drier

Last Answer : (C) Fluidised bed drier

Paper industry employs __________ driers.(A) Cylinder (B) Rotary (C) Spray (D) Fluidised bed

Description : Paper industry employs __________ driers. (A) Cylinder (B) Rotary (C) Spray (D) Fluidised bed

Last Answer : (A) Cylinder

Large scale drying of wheat is done in a __________ dryer. (A) Fluidised bed (B) Spouted bed (C) Tray (D) Vacuum rotary

Description : Large scale drying of wheat is done in a __________ dryer. (A) Fluidised bed (B) Spouted bed (C) Tray (D) Vacuum rotary

Last Answer : (B) Spouted bed

Kopper-Totzek coal gasifier (installed in a coal based nitrogeneous fertiliser plant) employs a/an __________ bed gasifier. (A) Entrained (B) Moving (C) Fixed (D) Fluidised

Description : Kopper-Totzek coal gasifier (installed in a coal based nitrogeneous fertiliser plant) employs a/an __________ bed gasifier. (A) Entrained (B) Moving (C) Fixed (D) Fluidised

Last Answer : (A) Entrained

Lurgi coal gasifier is a pressurised __________ bed reactor. (A) Moving (B) Fixed (C) Fluidised (D) Entrained

Description : Lurgi coal gasifier is a pressurised __________ bed reactor. (A) Moving (B) Fixed (C) Fluidised (D) Entrained

Last Answer : (A) Moving

Advantages of fluidised bed combustion are (A) Reduced NOx formation in flue gas (B) Lower furnace operating temperature (C) High heat transfer rate (D) All (A), (B) & (C)

Description : Advantages of fluidised bed combustion are (A) Reduced NOx formation in flue gas (B) Lower furnace operating temperature (C) High heat transfer rate (D) All (A), (B) & (C)

Last Answer : (D) All (A), (B) & (C)

Slugging in a fluidised bed can be avoided by using (A) Tall narrow vessel (B) Deep bed of solids (C) Shallow beds of solids and proper choice of particle size (D) Very large particles

Description : Slugging in a fluidised bed can be avoided by using (A) Tall narrow vessel (B) Deep bed of solids (C) Shallow beds of solids and proper choice of particle size (D) Very large particles

Last Answer : (C) Shallow beds of solids and proper choice of particle size

The uniformity of a gas fluidised bed depends upon the __________ of the solid particles. (A) Size (B) Surface properties (C) Both (A) and (B) (D) Neither (A) nor (B)

Description : The uniformity of a gas fluidised bed depends upon the __________ of the solid particles. (A) Size (B) Surface properties (C) Both (A) and (B) (D) Neither (A) nor (B)

Last Answer : (C) Both (A) and (B)

Slugging occurs in a fluidised bed, if the bed is (A) Narrow (B) Deep (C) Both (A) & (B) (D) Neither (A) nor (B)

Description : Slugging occurs in a fluidised bed, if the bed is (A) Narrow (B) Deep (C) Both (A) & (B) (D) Neither (A) nor (B)

Last Answer : (C) Both (A) & (B)

For a fluidised bed reactor, the most suitable/relevant model is a __________ model. (A) Tank in series (B) Bubbling bed (C) Plug flow (D) None of these

Description : For a fluidised bed reactor, the most suitable/relevant model is a __________ model. (A) Tank in series (B) Bubbling bed (C) Plug flow (D) None of these

Last Answer : (B) Bubbling bed

For high conversion in a highly exothermic solid catalysed reaction, use a __________ bed reactor. (A) Fixed (B) Fluidised bed reactor followed by a fixed (C) Fixed bed reactor followed by a fluidised (D) Fluidised

Description : For high conversion in a highly exothermic solid catalysed reaction, use a __________ bed reactor. (A) Fixed (B) Fluidised bed reactor followed by a fixed (C) Fixed bed reactor followed by a fluidised (D) Fluidised

Last Answer : (B) Fluidised bed reactor followed by a fixed

Which of the following is the most suitable for very high pressure gas phase reaction? (A) Batch reactor (B) Tubular flow reactor (C) Stirred tank reactor (D) Fluidised bed reactor

Description : Which of the following is the most suitable for very high pressure gas phase reaction? (A) Batch reactor (B) Tubular flow reactor (C) Stirred tank reactor (D) Fluidised bed reactor

Last Answer : (B) Tubular flow reactor

Which of the following will give maximum gas conversion? (A) Fixed bed reactor (B) Fluidised bed reactor (C) Semi-fluidised bed reactor (D) Plug-flow catalytic reactor

Description : Which of the following will give maximum gas conversion? (A) Fixed bed reactor (B) Fluidised bed reactor (C) Semi-fluidised bed reactor (D) Plug-flow catalytic reactor

Last Answer : (C) Semi-fluidised bed reactor

Fluidised bed reactor is characterised by (A) Uniformity of temperature (B) Comparatively smaller equipment (C) Very small pressure drop (D) Absence of continuous catalyst regeneration facility

Description : Fluidised bed reactor is characterised by (A) Uniformity of temperature (B) Comparatively smaller equipment (C) Very small pressure drop (D) Absence of continuous catalyst regeneration facility

Last Answer : (A) Uniformity of temperature

Which of the following is used for calcination of limestone and dolomite in industrial practice? (A) Fluidised bed reactor (B) Moving bed reactor (C) Fixed bed reactor (D) None of these

Description : Which of the following is used for calcination of limestone and dolomite in industrial practice? (A) Fluidised bed reactor (B) Moving bed reactor (C) Fixed bed reactor (D) None of these

Last Answer : (B) Moving bed reactor

Oil is hydrogenated using nickel catalyst in a __________ reactor. (A) Batch (B) Slurry (C) Fluidised bed (D) Fixed bed

Description : Oil is hydrogenated using nickel catalyst in a __________ reactor. (A) Batch (B) Slurry (C) Fluidised bed (D) Fixed bed

Last Answer : (B) Slurry

Commercial scale production of hydrogen from iron-steam reaction represented by, 3Fe + 3H2O = Fe3O4 + 4H2 , is not practised, as it is (A) A slow reaction (B) A discontinuous reaction (requiring regeneration of iron by water gas intermittently) (C) Still in development stage (by employing fluidised bed technique) (D) All (A), (B) and (C)

Description : Commercial scale production of hydrogen from iron-steam reaction represented by, 3Fe + 3H2O = Fe3O4 + 4H2 , is not practised, as it is (A) A slow reaction (B) A discontinuous reaction (requiring regeneration of ... in development stage (by employing fluidised bed technique) (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

. Lurgi coal gasifier is a pressurised __________ bed reactor. (A) Moving (B) Fixed (C) Fluidised (D) Entrained

Description : . Lurgi coal gasifier is a pressurised __________ bed reactor. (A) Moving (B) Fixed (C) Fluidised (D) Entrained

Last Answer : (A) Moving

Calcination of limestone is not done in a __________ kiln for producing lime. (A) Vertical shaft (B) Rotary (C) Fluidised bed (D) Fixed bed

Description : Calcination of limestone is not done in a __________ kiln for producing lime. (A) Vertical shaft (B) Rotary (C) Fluidised bed (D) Fixed bed

Last Answer : (D) Fixed bed

Heat transfer by __________ is almost absent in case of fluidised bed drying operation. (A) Radiation (B) Conduction (C) Convection (D) Both (B) & (C)

Description : Heat transfer by __________ is almost absent in case of fluidised bed drying operation. (A) Radiation (B) Conduction (C) Convection (D) Both (B) & (C)

Last Answer : A) Radiation

Explain the difference between AFBC, BFBC, PFBC and PCFB in regard to fluidised bed technologies.

Description : Explain the difference between AFBC, BFBC, PFBC and PCFB in regard to fluidised bed technologies.

Last Answer : AFBC (Atmospheric fluidised bed combustion) process consists of forming a bed of inert materials like finely sized ash or ash mixed with sand, limestone (for sulphur removal), and solid fuel particles in ... the bed as bubbles (fluidised bed) and gives the bed the appearance of a boiling liquid.

State some advantages of fluidised bed boilers?

Description : State some advantages of fluidised bed boilers?

Last Answer : Any type of fuel - solid, liquid (or) gaseous fuel (or) domestic and industrial waste can be used in FBC system. Any type- of combustible matter can be burned by adjusting the factors ... possible. High combustion efficiency. The solid fuel need not be pulverised in fluidised bed boilers.

Write about fluidised bed boilers?

Description : Write about fluidised bed boilers?

Last Answer : When the high velocity gas is passed through a packed bed of finely divided solid particles, the particles become suspended in the gas stream and the packed bed becomes a fluidised bed. When ... Bed Combustion. The boiler plant using this fluidised bed combustion is known as fluidised bed boilers.

Give the principle and working of Fluidised bed dryer.

Description : Give the principle and working of Fluidised bed dryer.

Last Answer : Principle: In FBD, good contact between hot air and particles to be dried is obtained which cause rapid drying. Working of Fluidised bed dryer: Two types of FBD are used in pharmaceutical industry. There are ... ranging from 5 kg to 200 kg with an average drying time of about 20-40 min.

Write the advantages and disadvantages of fluidised bed dryer.

Description : Write the advantages and disadvantages of fluidised bed dryer. 

Last Answer : Advantages: i. It give high drying rate. ii. Suitable for thermolabile material. iii. Drying takes place of individual particles. iv. Temperature can be controlled. v. Prevent the ... : i. Turbulence produces cause attrition of particles. ii. Movement can generate electrical charges. 

Pick out the wrong statement about cavitation. (A) Sudden reduction of pressure in a fluid flow system caused by flow separation, vortex formation or abrupt closing of valve leads to cavitation (B) Cavitation may be caused due to boiling of liquid by decreasing the pressure resulting in formation & collapse of vapor cavities (C) Cavitation begins at higher static pressure and lower velocity in larger diameter pipelines resulting in audible noise(D) Large scale cavitation cannot damage pipeline, restrict fluid flow anddamage steam turbine blades

Description : Pick out the wrong statement about cavitation. (A) Sudden reduction of pressure in a fluid flow system caused by flow separation, vortex formation or abrupt closing of valve leads to cavitation ... (D) Large scale cavitation cannot damage pipeline, restrict fluid flow and damage steam turbine blades

Last Answer : (D) Large scale cavitation cannot damage pipeline, restrict fluid flow and damage steam turbine blades

A coalescer in a mixer-settler liquid-liquid extraction column (A) Comprises of thin bed of substances of extended surface having high porosity (B) Helps in increasing the bubble size entering the settler (C) Helps in increasing the settling rate of the bubbles (D) All 'a', 'b', & 'c'

Description :  A coalescer in a mixer-settler liquid-liquid extraction column (A) Comprises of thin bed of substances of extended surface having high porosity (B) Helps in increasing the bubble size entering the settler ... increasing the settling rate of the bubbles (D) All 'a', 'b', & 'c'

Last Answer : (D) All 'a', 'b', & 'c'

A bed consists of particles of density 2000 kg/m3 . If the height of the bed is 1.5 metres and its porosity 0.6, the pressure drop required to fluidise the bed by air is (A) 25.61 kPa (B) 11.77 kPa (C) 14.86 kPa (D) 21.13 kPa

Description : A bed consists of particles of density 2000 kg/m3 . If the height of the bed is 1.5 metres and its porosity 0.6, the pressure drop required to fluidise the bed by air is (A) 25.61 kPa (B) 11.77 kPa (C) 14.86 kPa (D) 21.13 kPa

Last Answer : (B) 11.77 kPa

A gas (density = 1.5 kg/m3 , viscosity = 2 × 10 ‒5 kg/m.s) flowing through a packed bed (particle size = 0.5 cm, porosity = 0.5) at a superficial velocity of 2 m/s causes a pressure drop of 8400 Pa/m. The pressure drop for another gas, with density of 1.5 kg/m3and viscosity of 3 × 10 ‒5kg/m.s flowing at 3 m/s will be (A) 8400 Pa/m (B) 12600 Pa/m (C) 18900 Pa/m (D) 16800 Pa/m

Description : A gas (density = 1.5 kg/m3 , viscosity = 2 10 -5 kg/m.s) flowing through a packed bed (particle size = 0.5 cm, porosity = 0.5) at a superficial velocity of 2 m/s causes a pressure drop of 8400 Pa/m. The ... flowing at 3 m/s will be (A) 8400 Pa/m (B) 12600 Pa/m (C) 18900 Pa/m (D) 16800 Pa/m

Last Answer : (B) 12600 Pa/m

BET apparatus is used to determine the (A) Specific surface of a porous catalyst (B) Pore size distribution (C) Pore diameter (D) Porosity of the catalyst bed

Description : BET apparatus is used to determine the (A) Specific surface of a porous catalyst (B) Pore size distribution (C) Pore diameter (D) Porosity of the catalyst bed

Last Answer : (A) Specific surface of a porous catalyst