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Paste Thickener Design and Operation Selected to Achieve
Downstream Requirements
J. S. Slottee PasteThick Associates, USAJ. Johnson PasteThick
Associates, USA
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Introduction
Paste thickener design is determined by requirements for
1. Deposition 2. Pumping3. Process feed rate and
characteristics
This paper describes experience supporting the design of a paste
tailings system as a system
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Paste Stacking Flowsheet
Paste Thickener
TransferPump
UnderflowPump
Stack
TailingsFeed
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Considerations Downstream of the Paste Thickener
Disposal foot print, capacity Dam construction to contain
thickened
tailings Distribution of paste to optimize capacity Site
environmental requirements (i.e.
deposit permeability to groundwater)
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Surface Stacking
5% slope
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Flume Tests to Determine SlopeIron ore tailings
Deposition Profiles
0
5
10
15
20
25
0 1 2 3 4
Distance from leading edge, m
Mud
hei
ght,
cm
~ 20 Pa yield stress~ 55 Pa yield stress~ 280 Pa yield
stress
280 Pa20 Pa
55 Pa
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Pumping Paste & Thickened Tailings
Pumping requirements of paste from plant to impoundments
site
Potential for gravity flow Customer preference pump choice
(i.e.
centrifugal only)
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Inside thickener150 Pa 35%
Thickenerdischarge
80 Pa 35% Deposition50 Pa 35%
Shear Frequently Affects Rheology
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Pumped Paste: Same wt% solids, Different Yield Stress
% solids
Yie
ld S
tress
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Paste Thickener DesignBased on Yield Stress
Curve
% solids
Yie
ld S
tress
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Inside thickener150 Pa 35%
Shear Frequently Affects Rheology
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Same Yield Stress, Different % SolidsSpecific Gravity of
Solid
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Example #1
Pilot Testing Demonstrated
Potential
iron ore tailings80 wt% solids
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A low yield stress selected Lower pumping costs Area available
for
lower stacking angle
Example #1
Plant Requirements
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Example #1
Design
450 tph design throughput Varying feed t/hr 18 m dia, 12 m
sidewall
height paste thickener 3 centrifugal pumps in
series for transportation
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Example #2
Glass Sands Tailings
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Example #2Deposit Slope
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Example #2
Pilot Shear Loop Tests
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Example #2Varying Feed Particle Size and Rheology
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Example #2Design
High Density Recommended
Deep Bed High Density
Diameter, m (ft) 18 (59) 15 (49) 18 (59) Sidewall ht, m (ft) 7.2
(24) 15 (59) 7.2 (24) Floor Slope, degree 20 30 20 K-Factor 300 300
150
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The Paste System Design Process
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Summary
Downstream requirements determine underflow target and therefore
type of paste thickener.
Installed paste projects repeatedly demonstrate the correct
approach of a team of the thickener supplier, pumping/pipeline and
geotechnical consultants.
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Conclusions
Sharing rheology data between the team is essential
Rheology is greatly influenced by particle size all parties need
the same awareness of particle size range
Design to a target yield stress, not wt% solids
Paste Thickener Design and Operation Selected to Achieve Downstream
RequirementsIntroductionPaste Stacking FlowsheetConsiderations
Downstream of the Paste ThickenerSurface StackingFlume Tests to
Determine SlopeIron ore tailingsPumping Paste & Thickened
TailingsShear Frequently Affects Rheology Pumped Paste: Same wt%
solids, Different Yield StressPaste Thickener DesignBased on Yield
Stress CurveShear Frequently Affects Rheology Same Yield Stress,
Different % SolidsExample #1Pilot Testing Demonstrated
PotentialExample #1Plant RequirementsExample #1 Design Example
#2Glass Sands TailingsExample #2Deposit SlopeExample #2Pilot Shear
Loop TestsExample #2Varying Feed Particle Size and RheologyExample
#2DesignThe Paste System Design ProcessSummaryConclusions
