Fluidised beds are formed, when the__________________?

Related Mcqs:

1. 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

2. 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

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

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

4. 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 ?

   A. 0.2
   B. 0.5
   C. 0.7
   D. 0.8

5. The main factor on which the behaviour of a mass of fluidised solid depends mainly is the___________________?

   A. Fluid characteristics
   B. Particle size
   C. Both A. and B.
   D. Neither A. nor B.

6. 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

7. 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.

8. 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

9. 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

10. 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