Coal Preparation

Generalised Model of the Reflux Classifier using Computer Simulations Based on the Discrete Element Method

Coal Preparation » Fine Coal

Published: July 16Project Number: C22030

Get ReportAuthor: R. Moreno-Atanasio, N.H. Syed and K.P. Galvin | University of Newcastle

The aim of this project was to develop a generalised model of the Reflux Classifier (RC) utilizing a combination of a continuum approach based on the mechanisms of segregation and dispersion within the system, and a tracer particle approach based on the Discrete Element Method (DEM). The continuous segregation-dispersion model provides a direct solution to the transport of specific species through the system. Due to the computational demand of DEM, a tracer level approach was adopted in order to keep the total number of particles to a minimum, and thus make the computational demands manageable. Given the DEM operated at a tracer particle level, the degree of hindered settling was governed by the continuum solution, which was solved simultaneously with the DEM approach. DEM is based upon Newton's laws to describe particle translational and rotational motion, allowing the particle motion to be observed discretely. The segregation and dispersion approach, however, is based upon a volume flux balance method, and describes the net flux of a particle species relative to the vessel in terms of the dispersion and segregation contributions.


Validation of the model was undertaken with reference to the published literature. In 2008 it was discovered that the performance of the Reflux Classifier was improved significantly by introducing closely spaced inclined channels, with a nominal spacing of 6 mm (Galvin et al, 2010). The previous spacing had been typically 60 mm. This change led to the re-design of the technology, and the exploitation of a new laminar-shear mechanism, arising due to the high shear rate in the inclined channels. Therefore, following 2008, the variation in the D50 with particle size was reduced significantly and the Ep values also decreased significantly. For example, over the size range 0.25 to 2.0 mm the Ep was reduced from 0.15 to typically 0.08, well below anything achieved previously using water-based technology. The new model developed in this report focussed on this particular case, involving the laminar-shear mechanism, in the first instance, achieving excellent agreement with the reported partition curves (Galvin et al, 2010). The DEM model did provide some useful visualisation of the underlying mechanism, but the computational demands were considered too great for the model to be of general use.


Following the success of the model in describing the laminar-shear mechanism, and hence the partition curves in an RC2000 unit, additional validation work was conducted by simply removing the contributions of the shear rate in the inclined channels. Hydrodynamic dispersion is governed by the value of the dispersion coefficient which is applied in the vertical and horizontal directions of the vertical section of the Reflux Classifier, and in the tangent direction of the inclined channels. However, in the normal direction of the inclined channels the dispersion coefficient is quantified directly via the shear rate. Thus, the effects of the laminar-shear mechanism were removed by 'switching off' this contribution due to the shear rate. The net result was that the model predicted the poorer separation performance observed in the Reflux Classifier prior to 2008, with reference to published data in 2005 (Galvin et al, 2005). The agreement was excellent. Hence the model is considered to be both robust and predictive.


Overall, the continuum model based on the contributions of segregation and dispersion provides an effective model of the Reflux Classifier. The model describes the feed in terms of the mass portions within nominated size and density classes, for example six size fractions across seven density fractions corresponds to 42 species. Thus, the model is able to determine the partition curves for a given feed subjected to a specific volumetric and solids loading, and for a given yield, and fluidization rate. It is noted that beyond the size range of 0.25 to 2.0 mm the model showed some departure from the experimental data in the size range 0.125 to 0.250 mm. But as discussed in the report, the true behaviour may lie in between the experimental and simulated results hence this issue will be the subject of future study.



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