ACARP ACARP ACARP ACARP
Coal Preparation

A New Approach to Coarse Flotation

Coal Preparation » Fine Coal

Published: November 17Project Number: C23036

Get ReportAuthor: Kevin Galvin | The University of Newcastle

There are significant coal losses in flotation due to oversize particles entering the flotation circuit, usually due to worn screens. Conventional flotation fails to recover a significant fraction of these coarse particles, typically larger than 0.5 mm. A robust plant design requires unit operations that can span a wide size range, allowing changes in the screen aperture due to wear to be fully accommodated. Similarly, a single process that can operate across the full size range of 0-2 mm could also be attractive, provided the process is simple to run, high in throughput, and efficient.

The performance of the Reflux Flotation Cell in recovering coal in the size range 0 to 2 mm was investigated at a laboratory scale. The original hypothesis was that coarse particles could be recovered by applying high gas fluxes to produce a concentrated fluidized bed of spherical bubbles at a volume fraction of order 0.5~0.6. Then, any coarse particle detachment should be followed immediately by re-attachment with nearby bubbles. While this re-attachment might be the case, the study showed clearly that coarse coal recovery was favoured by lower gas fluxes, below 0.5 cm/s. There was little impact on coarse particle recovery due to the introduction of high volumetric feed fluxes.

The project included two distinct investigations. The first was concerned with the flotation of coarse tracer particles added to the system one at a time under specific hydrodynamic conditions. Tracer particles up to a screened top-size of 2.0 mm were introduced to the RFC individually, as part of the feed water. These particles were strongly hydrophobic, having a relative density of 1.25-1.30, saturated by diesel. The number of particles that partitioned to the overflow and underflow were counted. The proportion of the particles reporting to the overflow then provided a measure of performance. The experiments showed that the coarse particle recovery was very high at low gas fluxes, especially flux values below 0.5 cm/s. The results were clearly sensitive to the gas flux, and broadly independent of the feed flux.

The second approach involved the flotation of industrial feeds at different pulp densities. Since the tracer particle study effectively involved only a two-phase system, the industrial feed provided an assessment as a function of increasing solids concentration. Thus, this work provided a measure of the effect of particle-particle interactions on coarse particle yield and hence combustible recovery. These experiments were benchmarked against the Float/Sink separation method at a relative density of 1.6. Where the benchmark combustible recovery was high at coarse sizes, the RFC combustible recovery was similarly high. In some experiments, the Float/Sink combustible recovery at a relative density of 1.6 fell to below 60% at the coarser sizes. Here the coal feed contains more near-density material, and is arguably much lower in hydrophobicity. Nevertheless, the RFC also performed well on these coals relative to the benchmark.

In general, the recovery was higher than for the Float/Sink result for finer sizers, and lower for the coarser particles, consistent with that observed for water based gravity separation. The cross-over point occurred at coarser sizes of nearly 2.0 mm when the Float/Sink combustible recoveries were very high. Where the Float/Sink combustible recoveries fell to low levels (less than 60% at an RD of 1.6) at coarser sizes, the cross-over occurred at finer sizes, closer to 1.0 mm. This simply reflected the rapid Float/Sink decline in recovery as the particle size increased.

Overall, single stage flotation at the optimum feed and gas flux was superior to two stage flotation at half the feed flux, with a high gas flux in stage 1 followed by the optimum gas flux in stage 2. In conclusion, the Reflux Flotation Cell was very effective in floating coarse particles provided the gas flux was below 0.5 cm/s. This gas flux also provides adequate carrying capacity for the coarser particles.

Underground

Health and safety, productivity and environment initiatives.

Recently Completed Projects

C34019Longwall Bretby Cable Handling Monitoring With Fibre Optics

This project examined the potential of using fibre optic sensing tec...

C27049Mine Machine Radar Sensor Integration

The aim of this project was to develop an integrated radar sensor an...

C29007Innovative Coal Burst System To Investigate The Influence Of Confinement Loss And Pre-Conditioning On Coal Burst Mechanism

The challenges associated with designing and operating a safe and pr...

Underground

Open Cut

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

Recently Completed Projects

C33035High Water Recovery, Low Cost Desalination Using PV-Powered Membrane Capacitive Deionisation (Mcdi)

Capacitive deionization is a robust, energy efficient and cost effec...

C28035Topsoil Deficits In Site Rehabilitation Accelerated Transformation Of Spoils To Functional Soils

The incorporation of commercial biological amendments (compost, worm...

C34036Tyre Handler Testing Rig Stage 2: Lifting Trials

Tyre handling is a major source of risk in surface mining operations...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C34060In-Situ Investigation Of Coke Structure Formation Under Stamp Charged Coking Conditions

Stamp charged cokemaking has emerged as an effective technique to im...

C34062Improving The Classification Of Microstructure Distribution In Coke CT Images Using Deep Learning And Lineal Path Calculations

This project builds on a number of earlier projects that have helped...

C29071Source Of Variability Of Reactivity Of Coke In The CSR Test

The Coke Strength after Reaction (CSR) test is used worldwide to det...

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)

This third and final stage of this project was the culmination of a ...

C29069Low-Cost Catalyst Materials For Effective VAM Catalytic Oxidation

Application of ventilation air methane (VAM) thermal oxidiser requir...

C23052Novel Stone Dust Looping Process For Ventilation Air Methane Abatement

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

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