Coal Preparation

Application of Magnetic Fluids for Sink-Float Analysis - Literature Review

Coal Preparation » General

Published: June 04Project Number: C13055

Get ReportAuthor: Kevin Galvin | University of Newcastle

It is now more likely than ever that the Australian Coal industry will need to find an alternative to the heavy liquids used to produce a sink-float analysis of coal. Indeed, the Australian Standard on sink-float analysis is likely to be phased out over the next five years. Thus there is a strong motivation to find an alternative method. This report provides a literature review on the use of magnetized ferrofluids for producing a sink-float analysis.

A ferrofluid is a colloidal dispersion of 10 nm magnetite particles in a liquid, stabilized by the use of surfactants. When magnetized, and subjected to a magnetic field gradient, the dispersion experiences a powerful downwards force, much like the weight force of a dense liquid. In other words, by adjusting the current supplied to an electromagnet it is possible to produce a fluid of virtually any apparent density.

This technology is not new, and hence is not protected by patents. However, DeBeers have developed significant know-how, in addition to commercial devices that could be used immediately for sink-float analysis in the coal industry. It would be necessary, however, to investigate the accuracy of the method in the low density range of coal and mineral matter, and hence confirm its suitability. A comprehensive experimental study is therefore recommended in order to examine these issues.

The preferred technology for exploiting magnetized ferrofluids is the Ferro Hydrostatic Separator (FHS). Two poles of an electromagnet are separated by a physical distance known as the air gap, with the separation higher at the top than at the bottom. This arrangement creates a field strength that is smaller at the top than at the bottom, and hence a field gradient. The fluid in between is also magnetized, and, at sufficient magnetization, can be held in place on its own without the need for a container. The system is also placed on a slight incline in order to generate a horizontal gradient and hence horizontal motion. Particles that are added either float or sink, and hence can be seen to "pop" out the front end, either at the top or near the base. In this way, the FHS can function as a continuous production unit.

After studying this topic, it is concluded that a kerosene based ferrofluid offers significant advantages over a water based ferrofluid. Firstly, a kerosense based fluid is more readily diluted since the surfactant adsorbs onto the particles and is not at an equilibrium level within the fluid. If a water based fluid was diluted, additional surfactant would need to be added to ensure the surfactant remained adsorbed on the particles and did not desorb. Further, a kerosene based ferrofluid is much less dense which means a higher field gradient can be applied to achieve the minimum density for the sink-float work. Thus, the accuracy of the apparent densities should be higher. Kerosene is much less viscous and hence the drainage of the sink and float fractions will be quicker, and with the higher volatility the particles will dry more quickly.

DeBeers would like to secure a buyer for their know-how which is considerable, or at least a licensing arrangement. Unfortunately the sink-float market is not large, and hence the purchase of their know-how is not highly attractive. The technology is not protected by patents, though DeBeers does have some related patents, and details necessary to produce their current range of FHS machines. DeBeers also has significant know-how in the area of kerosene ferrofluid manufacture.

DeBeers have indicated they are prepared to provide an FHS machine for a comprehensive trial for the coal industry. Some minor improvements would be introduced, including the use of solid-state pressure transducers to measure and in turn control the density. The sink-float analysis would be conducted in the batch mode using a basket and scoop arrangement.


Health and safety, productivity and environment initiatives.


Open Cut

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

Recently Completed Projects

C19024Establishing Ecologically Sustainable Mine Water Release Criteria In Seasonally Flowing Streams

Extreme rainfall conditions in the Fitzroy Catchment over an approxi...

C25030Coal Mine Open Pit Final Void Closure And Relinquishment - Addressing Uncertainty In Coal Mine Environmental Planning

This report addresses uncertainties faced by coal mine operators whe...

C27046Estimation Of True Deformation Vector From Slope Radar Monitoring

Slope deformation radar monitors are now widely used in open cut coa...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C27004Improving Coal Flotation With Oscillatory Air Supply

This report provides detailed information on coal flotation with os...

C25018Improving Solids Recovery And Moisture Reduction In Ultrafine Coal Dewatering

This report provides detailed information on fine coal dewatering in...

C27028Lab Froth Flotation Testing Guide With Coal Quality

Correct outcomes from laboratory froth flotation testing in coal bor...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C26039Nanoporosity In Cokes: Their Origin, Control And Influence On CO2 Reactivity

This project using the outcomes of previous project C24060, examine...

C28063A Comprehensive Technical Review Of High-Efficiency Low-Emission (HELE) Pulverised Coal Combustion Technologies For Power Generation

Research and development has been undertaken worldwide to realise co...

C28064Carbon Structure Transformation During Coking Of Australian Coking Coals: Better Understanding The Coke Formation

Carbon structures of coke that are formed during the plastic layer a...

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

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...

C26004CFD Modelling Of Reverse Thermal Oxidisers For VAM Abatement - CFD Modelling Of Fixed-Bed RTO Devices

The project is part of a larger multi‐phase program of study a...

C27058Technological Assessment Of A Recycle Reactor For VAM Abatement

Underground coal mining emits high volumes of methane, diluted in ve...

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