5-9-B Cyclone Separators

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5-9-B Cyclone Separators

• Cyclone separators are gas cleaning devices that
  ? employ a centrifugal force generated by a
  spinning gas stream
• to separate the particulate matter (solid or
  liquid) from the gas carrier.
• The operation depends upon the tendency (inertia)
  of particles to move in a straight line when the
  direction of stream is changed.

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Two major classes of cyclone separators

• See overhead.

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How particles separated from gas?

• A high rate of spin
• Spinning gas
• Centrifugal force fling the dust particles to the
  walls of cylinder and cone
• The particle then slide down the wall and into
  the storage hopper
• The cleaned gas gradually spiral downward
• The downward cleaned gas gradually reversed its
  downward and forms a smaller ascending spiral
• A vortex finder tube extending downward into the
  cylinder aids in directing the inner vortex out
  of the device

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Efficiency of cyclone separators

• Figure 5-16
• Table 5-5

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The difference in theoretical prediction and
experimnental data

• See discussions on 4 points
• Reason
• This is caused by the fact that cyclone, like the
  settling chamber, has a turbulent flow, although
  the large friction losses along the wall tend to
  dampen out the turbulence.

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A more realistic approach to avoid a sharp cutoff
as predicted in the previously derived theory
(equation) to correlate data from cyclones with
similar proportions (in size) and with respect to
a cutoff size dp,50

• Find out the cutoff size dp that gives 50 of
  efficiency ? dp,50
• dp,50

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Significance of Figure 5-17
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Example 5-8

• A cyclone is designed with an inlet width of 12.0
  cm and four effective turns. The inlet gas
  velocity is to be 15.0 m/s, and the particle
  density is 1.70 g/cm3. Estimate the particle size
  that will be with 50 percent efficiency, if the
  gas is air and its temperature 350K.

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In review Cyclones collection efficiency

• ?col
• Why small particles are not captured efficiently?

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Other factors that can improve cyclones
efficiency