Coal Preparation

Plant-based Investigations of Hydrodynamic Behaviours in Large Coal Flotation Cells

Coal Preparation » Fine Coal

Published: June 14Project Number: C21051

Get ReportAuthor: Shenggen Hu and Philip Ofori | CSIRO


The performance of flotation cells can be impaired by the occurrence of biased feed distribution and unfavourable hydrodynamic behaviours, such as short-circuiting, pulp circulation flows, dead volumes or excessively high shear stress.


The hydrodynamics of a flotation cell is mainly determined by the cell design, but also influenced by operating conditions. Residence time distributions (RTDs) of phases are the easiest-to-obtain indications of the hydrodynamics of a flotation cell. The most important outcome from RTD experiment is the measured mean residence time. If the experimental mean residence time is different from the expected value, it indicates that there are unfavourable hydrodynamic behaviours such as dead volumes, short-circuiting, pulp recirculation or another anomaly. The cause of the difference can usually be determined by comparing the shapes of the RTD curves for the ideal case and the case in question.


Since the 1980s, fine coal cleaning in Australia has been dominated by Microcel and Jameson cell technologies. However, the hydrodynamic behaviours of these cells have not been experimentally characterised in the context of fine coal flotation. Therefore, industrial trends towards an increasingly larger capacity of new and existing installations and the need for improving combustibles recovery require a better understanding of hydrodynamic behaviours in industrial coal flotation cells.


The objective of this project was to characterise the hydrodynamic behaviours of Microcel columns and Jameson cells by carrying out plant-based experiments to determine the RTDs of liquid and solids phases and measure gas holdup distributions in the pulp phase.


This project has successfully developed effective approaches for characterising hydrodynamic behaviours in plant-scale flotation cells, based on residence time distribution (RTD) tests combined with electrical impedance spectroscopy (EIS) measurements. Plant-based tests have demonstrated that potassium chloride solutions and fine magnetite particles coated with sodium oleate can be conveniently used as liquid and floatable solids tracers in RTD tests in practical conditions. It has also been demonstrated that EIS is a sensitive tool for identifying abnormal distributions of froth characteristics (froth stability, solids loading and water content) and gas hold-up in the pulp phase.


Plant-based investigations of hydrodynamic behaviours in two Microcel columns were carried out at two Bowen Basin coal preparation plants. The following major unfavourable hydrodynamic behaviours were observed in the Microcel columns:

· Inappropriate positioning of four feed inlets caused the biased transfer of floatable solids towards the inner launder and the solids loading in the froth phase within the inner launder was almost twice as high as that in the froth exiting from the outer launder of the Microcel column, resulting in local overloading of the area surrounded by the inner launder.

· Sub-optimal injection locations of air spargers generated strong circulation flows along the axial direction, leading to large stagnant volumes of up to 70% of the total cell volume and short circuiting in the Microcel column with a height of 16 m and 25% dead volume in the column with a height of 9 m.

· Uneven distribution of the feed inlets caused froth solids loading to vary along the outer launder.

· The flow patterns in the pulp phase were either perfectly mixed flows or contained a major component of a perfectly mixed flow.

· Significant portions (63% for the 16 m column and 25% for the 9 m column) of feed reported to the tailing exit in less than 5 mins, resulting in low combustibles recoveries.


RTD tests and EIS measurements for solids loading of the froth phase were carried out on a circular and a rectangular Jameson cell at a Bowen Basin coal preparation plant. The following major hydrodynamic behaviours have been identified from these investigations:

· The multi-port feed distributor on the top of the circular Jameson cell produced a significant bias in the slurry feed distribution to the 24 downcomers, as evidenced by different RTD curves and solids loadings of froth phase.

· The pipe manifold feed distributor on the rectangular Jameson cell subdivided the slurry feed into branch streams with different solids content to each downcomer, leading to the solids content in the downstream branches being higher than those in upstream branches.

· The plunge of multi-phase mixture from the downcomer into the pulp phase generated high shear stress which could disrupt weak particle-bubble aggregates.

· The plunge of multi-phase mixture caused a fast channel flow between the downcomer exit and the tailings exit.


The improved understanding of hydrodynamic characteristics in Microcel columns and Jameson cells has allowed low-cost modifications of the internal structure of the flotation cells to be developed to optimise flow patterns and improved flotation plant performance in terms of capacity and product yield.


Health and safety, productivity and environment initiatives.

Recently Completed Projects

C27039True Triaxial Strength Of Coal Measure Rocks And Its Impact On Roadway Stability And Coal Burst Assessment

Rocks in the ground are subject to a range of stresses. The stresses...

C3063Underground Vehicle Design Standards And Statutory Implications

The Australian underground diesel vehicle fleet has evolved since di...

C3064Conveyor Belting And Lagging Shear Characteristics - Drive Drum Slip

The primary aim of this project was to investigate the relationsh...


Open Cut

Safety, productivity and the right to operate are priorities for open cut mine research.

Recently Completed Projects

C26029Geological Controls On Fluorine And Phosphorus In Bowen Basin Coals

Increasing global restrictions on fluorine in product coal prompted ...

C28033Raw Ash To Yield Relationships

Correct outcomes in yield predictions for product ash from coal bore...

C27038Establishing Self-Sustaining And Recognisable Ecological Mine Rehabilitation

In recent years an increasing interest has been placed on mining ope...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C27064Dry Beneficiation Using FGX And X-Ray Sorters

Conventional dry processing methods engage a single beneficiation de...

C26010Multi-Sloped Screening Efficiency With Changing Strokes, Frequencies, Feed Solids And Feed Rates-Pilot Plant Study

Optimising multi-sloped screens is often described as an art and the...

C28059Impact Of Water Quality In Coal Handling And Preparations Plants

The objective of this project was to deliver a concise reference do...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C23052Novel Stone Dust Looping Process For Ventilation Air Methane Abatement

This multi‐phase project is concerned with the mitigation of m...

C27054Optimisation Of A Thermal Flow Reversal Reactor For Ventilation Air Methane Mitigation

Ventilation air methane (VAM) generally accounts for 50-85% of the t...

C28076Selective Absorption Of Methane By Ionic Liquids (SAMIL) - Phase 2 Demonstration In A Packed Bed Reactor

An alternative approach to high temperature oxidation of ventilation...

Mine Site Greenhouse Gas Mitigation

Low Emission Coal Use

Step-change technologies aimed at reducing greenhouse gas emissions.

Recently Completed Projects

C17060BGasification Of Australian Coals

Four Australian coals were trialled in the Siemens 5 MWth pilot scale ga...

C17060AOxyfuel Technology For Carbon Capture And Storage Critical Clean Coal Technology - Interim Support

The status of oxy-fuel technology for first-generation plant is indicate...

C18007Review Of Underground Coal Gasification

This report consists of a broad review of underground coal gasification,...

Low Emission Coal Use

Mining And The Community

The relationship between mines and the local community.

Recently Completed Projects

C16027Assessing Housing And Labour Market Impacts Of Mining Developments In Bowen Basin Communities

The focus of this ACARP-funded project has been to identify a number...

C22029Understanding And Managing Cumulative Impacts Of Coal Mining And Other Land Uses In Regions With Diversified Economies

The coal industry operates in the context of competing land-uses that sh...

C23016Approval And Planning Assessment Of Black Coal Mines In NSW And Qld: A Review Of Economic Assessment Techniques

This reports on issues surrounding economic assessment and analysis ...

Mining And The Community


National Energy Research,Development & Demonstration Council (NERDDC) reports - pre 1992.

Recently Completed Projects

1609-C1609Self Heating of Spoil Piles from Open Cut Coal Mines

Self Heating of Spoil Piles from Open Cut Coal Mines

1301-C1301Stress Control Methods for Optimised Development...

Stress Control Methods for Optimised Development and Extraction Operations

0033-C1356Commissioned Report: Australian Thermal Coals...

Commissioned Report: Australian Thermal Coals - An Industry Handbook