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 × 103 VOM + 10.94 × 106 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 ?

Related Mcqs:

1. 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 × 103 VOM + 10.94 × 106 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

2. 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

3. 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

4. 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

5. Hydraulic mean radius for flow through packed bed of spherical particle of size, ‘Dp, with porosity ‘ε’ is________________?

   A. (Dp/6) (ε/1- ε)
   B. (Dp/6) (1- ε/ε)
   C. ⅔Dp (1- ε/ε)
   D. ⅔Dp (ε/1- ε)

6. 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

7. 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

8. Slugging occurs in a fluidised bed, if the bed is___________________?

   A. Narrow
   B. Deep
   C. Both A. & B.
   D. Neither A. nor B.

9. 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

10. 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