Using Rheology to Predict Unstable Flow for Laterite Slurry

1. UBC Mining Engineering Using Rheology to Predict Unstable Flow for Laterite Slurry Don Hallbom P.Eng. Ph.D. Candidate Advisor: Dr. Bern Klein

2. UBC Mining Engineering Overview What is �Unstable Flow�? Problems Predicting Unstable Flow Rheometry Unstable Flow Diagrams

3. UBC Mining Engineering Unstable Flow of Laterite Slurry 3 new pressure acid leach nickel plants recently opened in Australia Unstable flow problems were encountered at each plant Operating solids content limited by problems at various �choke points�

4. UBC Mining Engineering What is Unstable Flow? Yield Stress Related Unstable Flow: Rat-holing Plugging Pulsing (build-up and break down) Other Types of Unstable Flow: Turbulence Settling Transients (water hammer)

5. UBC Mining Engineering What is Unstable Flow?

6. UBC Mining Engineering Why Does it Matter? Slurry needs to be handled at a low solids content to obtain stable flow More water required Chemical additives may be required More acid for leaching More limestone for neutralization More tailings to dispose of

7. UBC Mining Engineering How Can Unstable Flow Conditions Be Predicted? Experience Pilot Plants Loop Tests Analytically (Design Equations)

8. UBC Mining Engineering Variables Affecting Slurry Flow Mineral types Particle sizes Solids content Pipe diameter Flow rate Temperature pH Pipe roughness Impurities Water hardness Salt content Flocculants Surfactants Shear history Heterogeneity Clay content

9. UBC Mining Engineering Rheometry Basics

10. UBC Mining Engineering Simple Rheometer in Action!

11. UBC Mining Engineering Flow Curves for Laterite Slurry Shear Stress Shear Rate

12. UBC Mining Engineering Unstable Flow of Wood Slurry Similar unstable flow problems occur in pulp & paper mills Bodenheimer (unstable flow) diagrams have been used for ~30 years in mill design and operation Operating solids have been increased from ~3% to ~15% w/w

13. UBC Mining Engineering Wood Slurry Flow Curve

14. UBC Mining Engineering Research Objectives To derive methods to create/modify Unstable Flow Diagrams for laterite slurry based on bench scale experiments (i.e., rheometry) To confirm the validity of the methods by flow loop testing

15. UBC Mining Engineering Rheometry and Analysis APPROACH: Model the flow curves of laterite slurry based on rheometry Use the model to predict unstable flow in pipe Relate the model parameters to physical parameters

16. UBC Mining Engineering Rheometry and Analysis ASSUMPTIONS: A large number of physical parameters can be reduced to a small number of model parameters Slurries with similar flow curves (models) will behave similarly Unstable flow regions can be related to the slurry flow curves

17. UBC Mining Engineering Time Dependency and Instability Shear Stress Shear Rate

18. UBC Mining Engineering Time Dependency and Instability Shear Stress Shear Rate

19. UBC Mining Engineering Low Shear Flow Regimes �NORMAL� FLOW Slurry flows as a stable �fluid� Annular flow (unyielded core) PLUG FLOW Slurry flows as a semi-solid mass Shears at the wall UNSTABLE FLOW

20. UBC Mining Engineering Unstable Flow Diagram (Flow in a Pipe)

21. UBC Mining Engineering Summary Some mineral slurries can exhibit unstable flow at low shear rates Unstable Flow Diagrams can be used to predict whether flow will be stable UFDs can aid plant design, trouble shooting, and operation

22. UBC Mining Engineering Summary Bench scale rheometry and analysis can be used to construct UFDs quickly and at a fraction of the cost of loop testing or pilot plants A similar approach may be used in the design of other slurry system components (e.g. tanks)

23. UBC Mining Engineering Acknowlegements SPONSORS: CERM3 NSERC Kvaerner Fluor Daniel Wright Highlands Pacific Lakefield Research

24. UBC Mining Engineering Using Rheology to Predict Unstable Flow for Laterite Slurry