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Advanced Course in Fluidized Bed Combustion
1986, Dubrovnik, Yugoslavia

DOI: 10.1615/ICHMT.1986.AdvCourseFluidBedComb


ISBN Print: 978-0-89116-409-8

Fundamentals of Fluidization

pages 87-125
DOI: 10.1615/ICHMT.1986.AdvCourseFluidBedComb.50
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ABSTRACT

  • Introduction
    • In fluidization it is attempted to overcome the problems in handling granular solids and to improve the heat transport properties. A simple experiment is used here to illustrate the principle. A gas is passed through a packed bed of particles supported by a gas distributor e.g. a porous plate. A pressure drop over the bed height can be observed due to the loss of mechanical energy by the friction of the flowing gas with the particles. At increasing gas flow rate this pressure drop rises, until at a certain point it just equals the net weight of the particles per unit cross sectional area; the bed is said to be incipiently fluidized and from this point the bed can in principle be lifted by the gas flow. The system starts to behave in many respects similar to a liquid due to a reduction of internal friction forces and cohesion. Beyond the point of Incipient fluidization two different phenomena may occur. If at higher gas velocities the bed maintains the balance between the average drag force on the particles by increasing their average inter distance (bed expansion) It Is said to be homogeneously fluidized. On the other hand this balance may be maintained at Increasing gas velocities by creating gas bubbles while leaving the inter particle distance essentially unaffected; this is called heterogeneous fluidization.

  • Minimum and Maximum Fluidization Velocity
  • Fluidization Regimes
  • The Nature of Bubbles in a Fluid Bed
  • Reactor Models
  • Application to Fluid Bed Combustion

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