Design Approach to Dilute Phase Pneumatic Conveying - PowerPoint PPT Presentation

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Design Approach to Dilute Phase Pneumatic Conveying

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Material and Gas properties (density, size shape, viscosity, etc. ... density in lbm/ft3. 7. Bends. Major source of ... Bulk density. Void fraction of gas phase ... – PowerPoint PPT presentation

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Title: Design Approach to Dilute Phase Pneumatic Conveying


1
Design Approach to Dilute Phase Pneumatic
Conveying
2
Steps in Dilute Phase Conveying Design
  • Material and Gas properties (density, size shape,
    viscosity, etc.)
  • Specify desired conveying rate
  • Estimate pipe diameter (with a little practice
    you get a feel for what works)
  • Calculate saltation velocity
  • Check loading (mass solids/mass gas)
  • If gt 10 to 15 then need larger diameter pipe
  • If lt 1 then need smaller diameter pipe

3
Steps Continued
  • Calculate pressure drop
  • May require iteration
  • If too large, may need to gradually increase pipe
    sizes (telescoping)
  • Do not let velocity drop below saltation velocity
  • Size blower

4
Components sum to total pressure drop
Hopper
Blower
Filter
4.
2.
3.
1.
5.
  • Blower, silencer, inlet filter
  • Acceleration
  • Horizontal pipe section
  • Pipe bends
  • Vertical pipe section

Other Components Cyclone Dust collector Filter Va
lves
5
Acceleration
  • Gas (outside of blower) and particles must
    accelerate up to operating velocity
  • Conveying gas velocity
  • Gas density
  • Particle velocity
  • Pipe cross sectional area
  • Conveying rate (mass/time)
  • Solids loading

6
Must relate Vp and Vg
  • Vg Vp slip velocity
  • Empirical relation by Hinkle (1954)
  • dp particle diameter (meters)
  • Particle density in kg/m3
  • In English units
  • dp in feet
  • density in lbm/ft3

7
Bends
  • Major source of wear/attrition
  • Pressure loss associated with re-acceleration of
    gas and solids
  • Bends usually specified by a ratio of the bend
    radius to pipe diameter R/D
  • Typical in conveying R/D 6 to 12

R
D
8
Bends
  • Chambers and Marcus (1986)
  • R/D gt 6, B 0.5
  • R/D 4, B 0.75
  • R/D 2, B 1.5

9
Horizontal Pipe
  • Pressure loss associated with frictional losses
    by gas and solids
  • L length of horizontal section
  • solids friction factor
  • Use experimental data if available

10
Solids Friction Factor
  • For dp gt 500 microns
  • For dp lt 500 microns
  • where

Terminal Velocity
11
Vertical
  • Pressure loss accounts for frictional losses plus
    static head (gravity)

Bulk density
Void fraction of gas phase (recall for fluidized
beds voidage is typically 0.4 to 0.7)
12
Example
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