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Effects of polymer dosage on rheology / spread-ability of polymer- amended MFT Civil and Environmental Department, Carleton University 17 June 2013.

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Presentation on theme: "Effects of polymer dosage on rheology / spread-ability of polymer- amended MFT Civil and Environmental Department, Carleton University 17 June 2013."— Presentation transcript:

1 Effects of polymer dosage on rheology / spread-ability of polymer- amended MFT Civil and Environmental Department, Carleton University 17 June 2013

2 Team manager Sahar Soleimani PhD Environmental Engineering 3 years experience in Civil Engineering Projects Expertise in numerical modelling Bereket Fisseha (at U of A) 5 years experience with Golder in Mining Geotechnical Services Shabnam Mizani 3 years experience with AMEC Tariq Bajwa 5 years in Civil and Hydropower Engineering

3 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

4 Objective – Improve understanding ofout of pipe rheology Controlling stack geometry (slope and lift heights) -Designing deposition cells -Trade off between deposition and dewaterability Flow Behaviour of the Amended Oil Sand Tailings upon Deposition 4 Objective Introduction Methodology Results Conclusion Future Work Rheology Topography Operational Parameters

5 Introduction 5 Flocculation: Aggregation Process Alters the Rheology significantly (Yield Stress, Viscosity) Mixing intensity and duration (shear caused during transportation can disintegrate the flocs) Objective Introduction Methodology Results Conclusion Future Work

6 Rheological Behaviour Tailings show Non-Newtonian behaviour Polymer amended MFT especially sensitive to aging and shearing 6 Rheology ?? Objective Introduction Methodology Results Conclusion Future Work

7 Methodology Slump Tests Back analysis of bench /field scale deposition Rheometer (Anton Paar Physica MCR301) 7 A.Stress growth (Rate control mode) B. Stress relaxation C. Creep (Stress controlled mode) Application of constant stress Application of constant stress rate Objective Introduction Methodology Results Conclusion Future Work

8 Some pictures captured from video

9 In Line Mixing In Field rapid mixing of polymer occurs in a 17 ft pipeline In Laboratory I. First a four blade impeller with radius of 8.5 cm was immersed in 1,800 g of MFT. 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 Objective Introduction Methodology Results Conclusion Future Work

10 Mixing Time & Dewaterbility 10 Highest water release

11 Results Stress Growth 11 Objective Introduction Methodology Results -Rheology -Flume Test Conclusion Future Work Shear Rate=0.1s -1 Shear Rate=1s -1

12 Constant stress test (Decreasing)-850gr/ton 30s each step (800-5Pa) 10min each step (250-30Pa) 12

13 Flume / 3-D bench deposition tests Using Funnel-9L of flocculated Tailings 13 Objective Introduction Methodology Results -Rheology -Spreadibility Conclusion Future Work Dosage (g/ton)Yield stress (Pa) , Yield stress from best fits of lubrication theory – JNNFM 2013

14 Comparison With Field Data (Pilot scale Test Oct2012) Stress Growth Shear rate=0.1s mixing time and intensity used to prepare the flocculated MFT in the laboratory was representative of field mixing conditions

15 Shell Atmospheric Drying cell during the autumn 2010 Total volume of tailings deposited in this cell was 7953 m 3 average slope of 2.1%. 15

16 Summary & Conclusion 16 Objective Introduction Methodology Results -Rheology -Spreadibility Conclusion Future Work Dosage (g/ton) Method of Measurement Slump (Pa) From Lubrication Theory (Pa) Stress growthDecreasing shear stress Stress Relaxation Shear rate (S -1 ) Max stress (Pa) Starting shear stress (Pa) Interpreted yield stress (Pa) Ave Stress (Pa) MFT , , ,020 1, ,000 1,300-* 1 1,180

17 Microstructure SEM Scanning electron microscopy (Vega-II XMU VPSEM, Tescan) 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 Objective Introduction Methodology Results Conclusion Future Work

18 Microstructure: MIP 18

19 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

20 Future/Ongoing Work Rheology Characterise the dependence of spreadability on both aging and shearing (i.e. Coussot Model ) Spreadibility finite element non-Newtonian flow codes such as ANYS Polyflow or ANSYS CFX 14 (Finite Volume) SPH – smooth particle hydrodynamics 20 Objective Introduction Methodology Results -Rheology -Spreadibility Conclusion Future Work Characteri stic time Rate of shear

21 SPH flume simulation compared to lubrication theory 21

22 Acknowledgements COSIA and NSERC Shell Canada and Barr Engineering 22


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