Coal Preparation

On-Line Monitoring and Control of DMC Separation Density and Efficiency

Coal Preparation » Process Control

Published: March 07Project Number: C13058

Get ReportAuthor: Shenggen Hu, Bruce Firth | CSIRO Enerty Technology

Separation density (RD50) and efficiency (Ep) are two important performance parameters of  dense medium cyclones (DMCs). These two parameters are not directly measured but calculated from particle density partition curves. Currently partition curves for DMCs are obtained from washability analysis or density tracer test.  However, these analysis cannot be performed routinely due to relatively high cost and time constraints.  Therefore, the RD50 and Ep are not routinely determined, let alone monitored on-line. Consequently, undesirable RD50 and/or Ep changes caused by unusual operating conditions and faults are not detected in a timely manner. Moreover, parallel DMC modules could be operating under different separation densities and efficiencies. The yield loss from operating in this way is very costly and variation in product quality will also be high.

In this project, an on-line measurement system for the on-line determination of dense medium cyclone separation density (RD50) and efficiency (Ep) from measured feed flowrate, the ratio of medium to coal, medium density in feed, overflow and underflow streams has been developed by integrating and modifying the electrical impedance spectroscopy based technique developed in previous ACARP projects. Software for the measurements and data communication was also developed.  An inclined channel flow guide in the front of the EIS electrode assembly has been developed to release air bubbles, which introduce significant noise in the measured EIS spectrum.

Plant-based trials of the on-line measurement system have been successfully carried out at a Bowen Basin plant. It has been found that the on-line measurement system can monitor the DMC feed flowrate,  the ratio of medium to coal, the medium density in feed, overflow and underflow streams.  The medium density measured by EIS has a similar accuracy as that from a Marcy gauge. Although the EIS technique has a lower precision than the Nucleonic gauge, the EIS technique is more reliable to measure the medium density in situations where the types of fine contaminants change frequently.

Mathematical models for estimating RD50 and Ep from the on-line measurements of process parameters have been developed.  In order to identify the most suitable model, three different types of models have been investigated: the modified Suspension-Partition Model [Hu et al., 2001], empirical correlations and the numerical tracer test model. Density tracer test and float-sink data from plant trials and other sources have been used to validate the model predictions. Due to lack of approaches to estimating model parameters and the requirement of intensive computation of CFD model, the numerical tracer test model was not successful. Empirical models can estimate RD50 and Ep with an accuracy level depending on the operating conditions.

A Suspension-Partition Model has been modified for predicting RD50 and Ep from measured process parameters.  All model parameters can be estimated from the measured process parameters. The model permits the partition curves of any particle size fractions to be generated. This model is particularly suitable for on-line application due to its simple computation.  From this model,  equations has been developed for the determinations of the medium splitting interface and the particle separation boundary.  A simple one-parameter equation for the calculation  of RD50   has been derived from this simplified theoretical model as:

Algorithms and  procedures for predicting Ep have been developed.  The predictions of RD50  and/or Ep from the Suspension-Partition Model agree very well with those obtained from 56 cases carried out in this project or from the literature.  

The average error of RD50 predictions using the above equation for 56 cases carried out in this project or from the literature is less than 0.035 RD. Considering an error of about 0.02 RD in the medium density measurement and significant errors in the determinations of RD50  and Ep from float-sink analysis, the predictions  from the modified suspension-partition model should be regarded as practical and useful. 

The measurement of medium density by EIS does not suffer from the bias problem as that encountered in Nucleonic gauge.  The precision of EIS technique in the plant-based trials is lower than that from Nucleonic gauge. But in a stable upward pipe flow,  the precision of EIS technique can be as high as 0.005.  Due to the acceptable accuracy,  the EIS technique and  the model for RD50 prediction will be very useful for monitoring and control of the differences in the feed medium density and cut points in parallel loops.

The modified Suspension-Partition Model is also useful  for the predictions DMC surging and vortex overloading. It has been found from a limited number of cases that the value of the difference between the medium splitting interface and the particle separation boundary is a reliable criterion for surging occurrence or vortex-finder overloading. Therefore, further work on the application of the model to the predictions of DMC surging and vortex-finder overloading  are highly recommended.  Further investigations are also required to extend the application of the model to operation limits of DMCs  and non-conventional DMCs. One of the  potential improvements in the suspension-partition model is to include the effect of the ratio of medium to coal.

The EIS concept has been shown to be able to indicate the density of the DMC medium and the ratio of medium to coal at the pilot plant and plant scales. It needs to be recognised that these outcomes were achieved for a limited time with experienced researchers in attendance. This indicates that the concept has the potential to be an important monitoring device in this economic significant aspect of coal preparation.

Interest is being expressed in a commercially available device by both industry and equipment manufacturers/suppliers. The next step is the development of appropriate EIS devices for longer term trials and the conduct of these trials. The emphasis would be the ability to provide information consistently on a longer term basis in the physically robust environment encountered in a coal preparation plant. The mechanism of supporting and conducting this next step is currently being investigated. 


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