Fluidization in Gas-Fluidized Beds
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Questions and Answers

What occurs in gas-fluidized beds?

  • Large pockets of gas, free of particles, rise through the bed (correct)
  • The entire bed becomes a homogenous mixture
  • The bed void fraction decreases significantly
  • Particles settle at the bottom of the bed
  • What is the term used to describe the condition where successive bubbles move up the column?

  • Particulate fluidization
  • Incipient fluidization
  • Slugging (correct)
  • Bubbling fluidization
  • What happens to the pressure drop as the superficial fluid velocity is gradually increased from zero?

  • It suddenly spikes
  • It gradually increases (correct)
  • It gradually decreases
  • It remains constant
  • What is the point at which the pressure drop starts to decrease?

    <p>Minimum fluidization velocity</p> Signup and view all the answers

    What occurs when very dense particles are in a liquid?

    <p>Bubbling fluidization occurs</p> Signup and view all the answers

    What is the term used to describe the phenomenon where gases at high pressure flow through beds of fine particles?

    <p>Particulate fluidization</p> Signup and view all the answers

    What is the primary reason for fluidizing a bed of particles?

    <p>To obtain vigorous agitation of the solids in contact with the fluid</p> Signup and view all the answers

    What is the term for the minimum velocity of the fluid required to fluidize a bed of particles?

    <p>Minimum fluidization velocity</p> Signup and view all the answers

    What type of fluidization occurs in liquids?

    <p>Particulate fluidization</p> Signup and view all the answers

    What is the primary application of fluidized beds in the petroleum industry?

    <p>Catalytic cracking</p> Signup and view all the answers

    What is the benefit of using fluidized beds in highly exothermic reaction situations?

    <p>Nearly uniform temperatures</p> Signup and view all the answers

    What is the purpose of fluidizing a bed of catalytic particles?

    <p>To achieve intimate contact between the particles and the fluid</p> Signup and view all the answers

    What is the condition to prevent particles from being carried out with the fluid at the exit?

    <p>Superficial velocity is equal to the settling velocity of the particles</p> Signup and view all the answers

    What is the range of void fraction ε for nearly spherical particles?

    <p>0.40 - 0.45</p> Signup and view all the answers

    What equation should be used to determine the minimum fluidization velocity for large particles?

    <p>Ergun equation</p> Signup and view all the answers

    What is the result of combining Equations (11) and (12) and eliminating pressure drop?

    <p>Minimum fluidization velocity</p> Signup and view all the answers

    What is the state of the bed when the superficial velocity Vs is equal to Vf?

    <p>Incipient fluidization</p> Signup and view all the answers

    What is the ratio of the settling velocity to the minimum fluidization velocity for ε lying in the range 0.40 - 0.45?

    <p>78-50</p> Signup and view all the answers

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