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Pneumatic Conveying Design

Nov 08 2010 01:00 PM | Chris Haslego in Bulk Solids ----- Share this topic:
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Nomenclature

VgGas velocity [ft/s]
rgGas density [lbs/ft3]
WSolids mass velocity [lbs/s ft2]
VpParticle velocity [ft/s]
fFanning friction factor
LEquivalent length of pipeline [ft]
DPipe inside diameter [ft]
gAcceleration due to gravity [32.2 ft/s2]
gcConstant [32.174 ft-lb/lb s2]
KFriction multiplier for the solids conveyed
RSolids to gas mass flow ration [lb/lb]
ZElevation change in pipe line [ft]


Early is their work, Zenz and Othmer used the following equations to described the pressure losses in horizontal and vertical pipes:

convey1

convey2

It was later concluded that the term (fp Vp/f Vg) should be replaced by the constant K (friction multiplier for the solids conveyed) because the term was dependent upon the physical properties of the solids being conveyed. The value for K must be back-calculated from actual pressure drop data from an existing system or it must be determined experimentally in plant tests. This lead to the following equation for the pressure drop for the solids in the system.

convey3

Thus, the equation used for the total system pressure loss (Base Equation) is:

convey4

where:

DPTTotal pressure loss in the system
DPaccPressure loss due to acceleration of the solids from their "at rest" condition at the pick up point.
DPgFrictional pressure loss of the gas
DPsFrictional pressure loss of the solids
DHgElevation pressure loss of the gas
DHsElevation pressure loss of the solids
DPmiscPressure losses from miscellaneous equipment





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