ACARP ACARP ACARP ACARP
Coal Preparation

A Step Change in Fine Coal Beneficiation - Inverse Flotation

Coal Preparation » Fine Coal

Published: July 12Project Number: C19036

Get ReportAuthor: Kevin Galvin, Kathika Liyanaarachchi, Simon Iveson, Grant Webber, Catherine Whitby, John Ralston, Daniel Weissmann, Diana N. H. Tran | University of Newcastle, University of South Australia

The objective of this study was to establish a major step change in the technology used by the coal preparation industry to beneficiate fine particles, especially particles smaller than 0.200 mm. We use the term “Inverse Flotation” to describe the new method of fine coal beneficiation. Particles in a gaseous dispersion interact from the gas side of the gas-liquid interface, either at a planar interface or at the surface of falling drops.

In conventional flotation the particles approach the gas-liquid interface from the liquid side. This limits the efficiency of recovering fine particles, because fine particles tend to follow the fluid stream lines and hence have a low collision efficiency with the bubbles. Due to the low viscosity of air compared to water, inverse flotation processes should have a much higher collision efficiency.

The aim of this project was to perform laboratory scale experiments to test the feasibility of two alternative inverse flotation methods. The first method involved contacting the particles with a moving liquid interface in a trough. Hydrophilic particles should sink, and the hydrophobic coal particles should float and be entrained in the overflow. This work was carried out at the University of South Australia. The trough showed the potential to separate particles based on their hydrophobicity. For instance, the trough could split a -106 um coal sample with a head ash of 55 % into an overflow product with an ash of 23 % and underflow with an ash of 61 %, at a yield of 57 %. This work was compared with that achievable using a laboratory Denver flotation cell. After 20 minutes, in the absence of a frothing agent, this cell was able to separate the same feed sample and achieve a product with 11 % ash at a yield of 39 %. However, with MIBC frothing agent, a product with 14 % ash at a yield of 62 % was achieved. This result was much better than that obtained using the trough.

The second method involved the interaction of a dry dispersion of feed with falling drops. This work was carried out at the University of Newcastle. The feed plume of dispersed particles was projected horizontally into the collision chamber. Water drops were released to fall vertically through the chamber. The dispersed particles then collided with the water drops, with selective capture of the hydrophilic particles. The water collected at the base of the chamber, and then drained into the underflow collection tank.

These experiments produced a linear correlation between the recovery of the particles in the underflow and the water flux. The difference in underflow recovery for two types of particles provides a measure of the selectivity of the process. For glass ballotini (spheres) in 38-45 um size range, the cleaned ballotini had a recovery about 30 % higher than the uncleaned ballotini. Clean (hydrophilic) crushed silica particles had a 45 % higher probability of being captured than coal particles of a similar size. Hence, this work proved that there is selectivity between hydrophilic and hydrophobic particles.

Overall, there was some clear selectivity measured, dependent on the particle size and other surface properties of the material. However, given the limited magnitude of the observed selectivity, it is unlikely that either of these concepts will develop into a new technology competitive with conventional froth flotation. The trough also suffered from a very limited throughput capacity. The multiple falling drop apparatus had serious operational problems when trying to disperse fine particles into a plume, due to their tendency to aggregate. These problems would only become worse with real feeds.

As a result, it is recommended that no further investment be made into developing either of these two processes.

Underground

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...

Underground

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

NERDDC

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

NERDDC