Transcript Effects of polymer dosage and mixing time on initial

“Effects of polymer dosage on
rheology / spread-ability of polymeramended MFT
Civil and Environmental Department, Carleton University
17 June 2013
Shabnam Mizani
3 years experience
with AMEC
Bereket Fisseha
(at U of A)
Team manager
Sahar Soleimani
5 years experience with
Golder in Mining
Geotechnical Services
PhD Environmental Engineering
3 years experience in Civil Engineering
Projects
Expertise in numerical modelling
Tariq Bajwa
5 years in Civil and Hydropower
Engineering
Project Background
► Part of a larger project funded by COSIA looking at
optimization of polymer-amended mature fine tailings
► Optimization includes:
► i) Short-term dewatering due to action of polymer
and consolidation under self-weight in a thin (< 1 m )
lift
► ii) Dewatering due to desiccation
► Iii) Dewatering and geotechnical behaviour after
consolidation under addition of new lifts
► Iv) Spread-ability (rheological behaviour after
material emerges from the pipe)
3
Objective – Improve understanding of
“out of pipe” rheology
 Objective
Controlling stack geometry (slope and lift heights)
Introduction
- Designing deposition cells
Methodology
- Trade off between deposition and dewaterability
Results
Conclusion
Topography
Future Work Operational
Parameters
Flow Behaviour of the Amended Oil Sand Tailings upon Deposition
Rheology
4
16
Introduction
Introduction
Methodology
Results
Conclusion
Future Work
Flocculation: Aggregation Process
12
10
8
6
4
2
0
0
20
40
60
80
100 120 140 160 180 200
Shear Rate(s-1)
0.7
0.6
Viscosity(Pa.s)
 Objective
Shear Stress(Pa)
14
0.5
0.4
0.3
0.2
0.1
0
0
20
40
60
80
100
120
140
160
180
200
Shear Rate (s-1)
Alters the Rheology significantly (Yield Stress, Viscosity)
Mixing intensity and duration (shear caused during
transportation can disintegrate the flocs)
5
Rheological Behaviour
 Objective
► Tailings show Non-Newtonian behaviour
Introduction ► Polymer amended MFT especially sensitive to aging and
shearing
Methodology
Results
Conclusion
Future Work
Rheology
??
6
Methodology
 Objective
Introduction
Methodology
Results
Conclusion
Future Work
► Slump Tests
► Back analysis of bench /field scale deposition
► Rheometer (Anton Paar Physica MCR301)
A.Stress growth (Rate control mode)
B. Stress relaxation
C.
Creep (Stress controlled mode)
Application of constant stress
Application of constant stress rate
7
Some pictures captured
from
video
In Line Mixing
 Objective
In Field
Introduction ► rapid mixing of polymer occurs in a 17 ft pipeline
Methodology
Results
In Laboratory
Conclusion
First a four blade impeller with radius of 8.5 cm was immersed in 1,800 g of MFT.
Future Work I.
II.
The mixing was then started at a fixed speed of 250 rpm.
III.
The flocculant solution was then added but was mainly directed near the impeller during
mixing.
IV.
After adding the 0.4% flocculant solution the mixing was continued for another 10 seconds
9
Mixing Time & Dewaterbility
80
70
Highest water
release
60
Release Water(mL)
70
60
50
40
24 Hr
50
48 Hr
72 Hr
40
96Hr
144Hr
30
312Hr
30
20
20
600
800
10
1000
5
Dose (gr/ton)
0.2
24 Hr
0.15
48 Hr
0.1
72 Hr
96Hr
0.05
10
0
0.25
Solids in Release Water(g/ml)
Release Water(Ml)
80
1200
1400
10
0
600
Mixing Time(s)
312Hr
80015
1,000
Dosage (g/ton)
20
1,200
10
Results
1200
1200
1000
1000
600 g/ton
725 g/ton
Shear Stress(Pa)
Introduction
Methodology
Results
-Rheology
-Flume Test
Conclusion
Future Work
► Stress Growth
Shear Stress(Pa)
 Objective
800
800
850 g/ton
1,000 g/ton
600
400
200
600
1,200 g/ton
600 g/ton
725 g/ton
850 g/ton
1,000 g/ton
400
1,200 g/ton
200
0
0
0
0
Shear Rate=0.1s-1
50
50
100
100
150
200
150
200
Time(s)
Time(s)
250
250
300
350
300
Shear Rate=1s-1
11
Constant stress test (Decreasing)-850gr/ton
10min each step (250-30Pa)
30s each step (800-5Pa)
200000
700000
180000
600000
160000
500000
100000
16
800Pa
80000
500 Pa
250 Pa
700Pa
50 Pa
60000
14
Viscosity (Pa.s)
700Pa
500 Pa
40000
12
10
0
100 Pa-10min
Raw MFT-4 Dec
16
75 Pa-10min
50 Pa-10min
250 Pa -10min
5 Pa
30 Pa-10 min
100000 12
8
50 Pa
20
40
5 Pa
6
Raw MFT- 4 Dec
0
300000
18
200000 14
250 Pa
20000
400000
250Pa-10min
60
80
100
Time (S)
120
140
160
Viscosity (Pa.s)
18
20
800Pa
120000
Strain (%)
Strain (%)
20 140000
150 Pa-10 min
0 10
0
8
180
500
4
2
2
2000
2500
3000
50 Pa-10 min
6
4
75 Pa
-10 min 1500
1000
Time (S)
0
0
0
20
40
60
80
100
Time (S)
120
140
160
180
0
500
1000
1500
Time (S)
2000
2500
3000
12
Flume / 3-D bench deposition tests
Introduction
Methodology
Results
-Rheology
-Spreadibility
Conclusion
Future Work
► Using Funnel-9L of flocculated Tailings
10
9
600 gr/ton
8
725gr/ton
850gr/ton
7
Height(cm)
 Objective
1000gr/ton
6
Predicted
5
4
Yield stress from best fits of
lubrication theory – JNNFM 2013
3
2
1
0
0
10
20
30
Run-out(cm)
Dosage (g/ton)
600
Yield stress (Pa)
60
725
850
1,000
95
104
110
40
50
60
13
Comparison With Field Data (Pilot scale Test
Oct2012)
► Stress Growth Shear rate=0.1s-1
1200
Yield Stress (Pa)
1000
Field Data
800
Lab Data
600
400
200
0
700
750
800
850
900
Floc Dose (g/ton)
950
1,000
mixing time and intensity used to prepare the flocculated
MFT in the laboratory was representative of field mixing
conditions
14
•
Shell Atmospheric Drying cell during the autumn 2010
•
Total volume of tailings deposited in this cell was 7953 m3
•
average slope of 2.1%.
293.00
Deposited Tails
292.00
Topography
LT prediction, 100 Pa yield stress
LT prediction 240 Pa yield stress
Height(m)
291.00
290.00
289.00
288.00
287.00
0
50
100
Run-Out( m)
150
200
250
15
Summary & Conclusion
 Objective
Method of Measurement
Introduction
Methodology
Results
-Rheology
-Spreadibility
Conclusion
Future Work
Stress growth
Dosage
(g/ton)
Slump (Pa)
From Lubrication
Theory
(Pa)
MFT
-
-
600
92
60
725
125
95
850
154
104
1,000
163
110
1,200
187
-
Shear rate
Max stress
(S-1)
(Pa)
0.1
1
0.1
1
0.1
1
28.8
28.0
169
207
255
323
0.1
1
333
510
0.1
1
0.1
988
1,020
1,000
1
1,180
Decreasing shear stress
Stress
Relaxation
Starting
shear stress
(Pa)
Interpreted
yield stress
(Pa)
Ave Stress
100
10
5.52
250
200
50-100
50-100
450
50-100
700
50-100
1,000
250
1,300
-*
(Pa)
16.7
16
Microstructure SEM
► Scanning electron microscopy (Vega-II XMU VPSEM, Tescan)
 Objective
Introduction
Methodology
Results
Conclusion
Future Work
► speed of 148 µs/pixel and a working distance of 6-8 mm.
► acceleration voltage of 20 kV using a cold stage to freeze the samples(prevent
excessive water withdrawal during the observation under the vacuum condition
of the SEM chamber)
Raw MFT
1000 g/ton
17
Microstructure: MIP
Incremental pore volume (ml/g)
0.02
0.018
0.016
0.014
0.012
0.01
MFT
1500 ppm
700 ppm
0.008
0.006
0.004
0.002
0
0.01
0.1
1
Pore diameter (microns)
10
18
Summary & Conclusion
► Laboratory prepared samples could mimic field samples in the
stress growth tests
► Yield stress calculated from the flume and other tests employing
lubrication theory was in best agreement with slump and
controlled decreasing shear stress test.
► Lift thickness control likely needs to consider increase in
effective yield stress of the deposit over deposition time
► Even high sheared polymer amended MFT still manifests a
significant yield stress
19
Future/Ongoing Work
Rheology
 Objective

Rate of
shear
Characterise the dependence of spreadability on both aging and shearing (i.e.
.
Coussot Model d  1     )
Introduction
dt 
Methodology Spreadibility
Characteri
 finite element non-Newtonian stic
flow
codes such as ANYS Polyflow or ANSYS CFX 14
Results
time
(Finite Volume)
-Rheology
 SPH – smooth particle hydrodynamics
-Spreadibility
Conclusion
 Future Work
20
SPH flume simulation compared to
lubrication theory
21
Acknowledgements
► COSIA and NSERC
► Shell Canada and Barr Engineering
22