Associated Event

26th International Conference on Paste, Thickened and Filtered Tailings
16–18 April 2024 | Pullman Melbourne on the Park, Melbourne, Australia

Rheology Fundamentals for Slurries and Pastes Short Course

15 April 2024 | Stradbroke Room, Pullman Melbourne on the Park, Melbourne, Australia

Integral to process plant design is identification of the slurry system operating window that allows increased throughput and recovery while safely decreasing capital and operating costs. For any system involving thickening, filtration or paste production, understanding the material rheological and dewatering characteristics is prerequisite to identifying this window and optimal, reliable and safe operation.

An understanding of slurry and paste rheology or fluid flow, dewatering including thickening and filtration and surface chemistry/rheology interrelationships is fundamental to process system design, optimal operation and risk management.

Investment into an integrated understanding of slurry, dewatering and cake property fundamentals is often insufficient to mitigate against the risk of under or over design and poor operating performance.

The course will focus on identifying what information is required, how to interpret measured data and how to apply to new system design and existing operations.

Attendees will learn about slurry physical and chemical properties, how flow and dewatering properties or rheology are measured and how to meaningfully interpret rheological data for viscosity, yield stress, time dependence and dewatering information. The course will outline how to apply rheology, dewatering and surface chemistry knowledge to pipeline transport, and thickening and filtration equipment selection and optimal control and operation. 

Time Workshop Program
07:45 – 08:20
08:20 – 08:30

Welcome and introduction | Dr Fiona Sofrà, Rheological Consulting Services Pty Ltd

08:30 – 10:15

What is a slurry? The liquid-to-solid continuum | Dr Fiona Sofrà

How do we define a slurry/paste?

  • Solids concentration/density
  • Particle size distribution (PSD)
  • Particle morphology
  • Mineralogy/surface chemistry

Slurry rheology/flow properties | Dr Fiona Sofrà

Explanation of the following flow properties and an overview of what they mean in the 'real' world.

  • Yield stress
  • Viscosity
  • Shear rate dependence
  • Time dependence
  • The effect of solids concentration, PSD, morphology on the flow characteristics of slurries - examples
10:15 – 10:45
10:45 – 12:00

Slurry rheology measurement | Dr Fiona Sofrà

Yeild stress measurement

  • The vane method
  • The slump tests
  • Extrapolation
  • Online rheometer

Shear stress - shear rate (flow curve and viscosity) measurement

  • Rotational methods including the 'bucket' rheometer
  • Capillary/pipe loop testing
  • Laboratory versus pipe loop/online testing
  • Data extrapolations

Reading rheograms

Flow models - communicating data | Dr Fiona Sofrà

  • Types of flow models
  • How to use flow models
  • Slurry rheology measurement problems and pitfalls

Slurry rheology roadmap | Dr Fiona Sofrà

  • A systematic 'decision tree' aproach for rheology studies for slurry system design and optimisation

Slurry surface chemistry/rheology and dewatering relationshipsProfessor Peter Scales, Rheological
Consulting Services Pty Ltd

  • Clay chemistry, zeta potential and ionic strength explained
  • The clays that cause rheology and dewatering issues
  • Additives (including flocculants) and suspension rheology and dewatering
12:00 – 13:00
13:00 – 14:30

Dewatering | Professor Peter Scales

Characteristics of the dewatering of suspensions

  • Compressibility, permeability, settling, clarification and the role of flocculants
  • Saturated and desaturated suspensions

Thickening | Professor Peter Scales

  • Thickener types and selection criteria
  • Relationship of compressional and shear rheology in a thickener
  • Control of the thickener for optimal rheology
14:30 – 15:00
15:00 – 16:40

Filtration Dr Ross de Kretser, Acclarium Tailings and Solid-Liquid Separations Consulting

  • Filter types, selection criteria with specific relevance to tailings

Filtration and geotechnical considerations Dr Ross de Kretser

  • Cake handling and geotechnical considerations in system design and optimisation
  • Geotechnical parameters, dewatering and shear rheology relationships
  • Yield stress
  • Application of an integrated understanding of rheology, dewatering and cake behaviour to pressure filtration system design and control
16:40 – 17:00
Question and answer session

Course Presenters

Dr Fiona Sofrà
Managing Director
Rheological Consulting Services Pty Ltd

Fiona is co-founder and managing director of Rheological Consulting Services Pty Ltd and an honorary fellow of the University of Melbourne. Fiona is an internationally recognised expert in slurry handling and rheology, having consulted to many world leading minerals companies for over 20 years. Fiona’s approach is focused on understanding the complex interrelationships that contribute to rheological phenomena in slurries and pastes and translating these into relevant and valuable inputs for optimal and reliable plant operation.

Professor Peter Scales
Rheological Consulting Services Pty Ltd


Peter is an emeritus professor in the Department of Chemical and Biomolecular Engineering at the University of Melbourne. He is a founding director of Rheological Consulting Services Pty Ltd and has over 30 years of academic and industrial experience in particle processing, conducting research and consulting in the areas of slurry flow, particle dispersion, particle flocculation and separations technologies including thickening, filtration and centrifugation.

Dr Ross de Kretser
Technical Consultant
Acclarium Tailings and Solid-Liquid Separations Consulting

Ross has over 25 years’ experience with the mineral processing and water treatment industries in the areas of solid–liquid separations, slurry surface chemical modification and rheology. This experience has been both in collaborative industrial research at the University of Melbourne, as well as with Rio Tinto in their water, waste and tailings global technical expertise group. In 2016, he founded Acclarium Tailings and Solid-liquid Separation Consulting, focusing on delivering value to the mineral processing industry through a strong integration of multi-disciplinary practical and fundamental knowledge of tailings dewatering and management.