University of Dayton
eCommons
Stander Symposium Posters
Stander Symposium
4-18-2012
Suspension of Solid Mixtures by Mechanical
Agitation
Tianxin Bao
University of Dayton, [email protected]
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Recommended Citation
Bao, Tianxin, "Suspension of Solid Mixtures by Mechanical Agitation" (2012). Stander Symposium Posters. Book 20.
http://ecommons.udayton.edu/stander_posters/20
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Suspension of Solid Mixtures by Mechanical Agitation
Tianxin Bao
Advisor: Dr. Kevin Myers
Just-suspended condition, which is the
most commonly encountered level of
liquid-solid agitation, occurs when no
solid particles rest on the tank base for
longer than one to two seconds such that
all solids are suspended in liquid phase
and the maximum surface area is
accessible for desired process
requirement with the minimum power
consumption.
350
Experimental Procedure
• A fixed mass of solid 1 was first added in
test tank
• The various amounts of solid 2 masses
were progressively added in the test tank
• The sum of powers approach (design
rule) was applied to estimate the solids
mixture just-suspended speed (Njs,Pre)
• With the fixed mass of solid 1, mixture
speeds (Njs,Mea) were measured with
progressively increasing mass of solid 2
250
200
150
100
50
Measured Njs (rpm)
0
0
Motivation and Objective
Results
• Just-suspended speed (Njs) of uniform
solids has been extensively studied and
can be reasonably predicted by empirical
correlations
• There has been very little work on justsuspended behavior of solid mixtures
• Is the mixture suspension power equal
to the sum of powers required to
suspend the individual solids in a binary
system (Pmixture=Psolid 1 + Psolid 2)
• Design rule: Njs,m = (Njs,13 + Njs,23)1/3
• High-density systems: the combination of
two solids of density above 2.4 g/cm3
System Geometry
• 11.5-inch diameter flat-bottom tank
• Four 1-inch width straight baffles
• 4-inch diameter 45°pitch-blade turbine
• 2.875-inch off-bottom clearance
• Liquid level equal to tank diameter
•Water used as liquid phase
Observation:
 Njs,Pre > Njs,Mea
(for most of
systems)
 Njs,Pre = Njs,Mea
(for only one
system brown
cross)
300
Predicted Njs (rpm)
Introduction
50
100
150
200
250
300
• Mixed-density systems: the combination of a
low density solid and a high density solid
600
Observation:
 Njs,Pre > Njs,Mea
(for olivine sand
system red square)
 Njs,Pre = Njs,Mea
(for other systems)
Predicted Njs (rpm)
800
Olivine sand systems
Predicted Njs (rpm)
400
600
400
200
Measured Njs (rpm)
0
200
350
0
200
400
600
Conclusion
Measured Njs (rpm)
0
0
200
400
600
800
Observation:
 Njs,Pre > Njs,Mea (for olivine sand systems)
 Njs,Pre = Njs,Mea (for other systems)
• Low-density systems: the combination of
two solids of density below 1.5 g/cm3
The sum of powers approach can reasonably
predict the just-suspended speed of both highdensity and mixed-density systems except those
involving olivine sand while the predicted speeds
from the sum of powers approach are typically ten
to twenty percent greater than the measured
speeds of low-density systems. For those systems
with olivine sand, the sum of powers approach
always significantly over predicts the measured
mixture suspension speeds.