ACARP ACARP ACARP ACARP
Coal Preparation

Tailings Management Through Control Of Colloidal Interactions

Coal Preparation » Environmental Improvement

Published: July 11Project Number: C18039

Get ReportAuthor: Philip Ofori, Anh V Nguyen, Bruce Firth, Clint McNally | CSIRO Energy Technology & School of Chemical Engineering University of Queensland

Handling fines rejects, stabilising tailings dams with a high proportion of clay materials and the emerging problem of availability, quality and cost of water present significant challenges to the coal industry. Effective solutions for these challenges are needed and require an improved understanding of surface interactions forces between tailings particles which control the settling and consolidation of flocculated coal preparation plant (CPP) tailings. The thickened tailings approach provides a possible pathway for addressing some of the issues concerning tailings dam management, rehabilitation and water recovery. This project was undertaken to:

· Provide insights into the surface interaction forces between particles during coagulation, flocculation, settling and bed consolidation of coal preparation tailings in intensive thickening processes;

· Correlate the understanding of surface interaction forces with particle and floc settling rates and degree of bed consolidation during sedimentation; and

· Develop approaches to enhance and optimise CPP tailings thickening for demonstration at a pilot scale in a subsequent project.

Four samples from four coal preparation plants in the Bowen Basin and Hunter Valley, together with over 20 flocculant samples from three major international suppliers were obtained, characterised and examined in this project.

The flocculation tests were conducted under reproducible hydrodynamic conditions in batch mode. Flocculants were found that were effective in flocculating each of the four tailings samples and optimum dosages were identified with respect to settling rates.  Hydrodynamic conditions were found to have profound impact on floc settling rates and to a lesser extent sediment consolidation. Low mixing speeds produced large flocs with high settling rates, while very high mixing speed during flocculation resulted in irreversible floc degradation leading to much reduced settling rates with some additional sediment consolidation. The surface interaction forces between the coal tailings surfaces were measured and statistically characterised using atomic force microscopy (AFM). The AFM results showed that there was an optimum flocculant concentration for each tailings sample which produced the highest adhesive strength of surface interaction forces needed to resist floc breakage by external forces. However, the optimum concentrations that produced the highest adhesive forces differed from those required to produce optimum settling rates. The concentrations required to produce the highest adhesive forces in the AFM were much lower than those required to produce the highest settling rates in the sedimentation tests due to the large surface area of particles in the concentrated suspensions used in the settling tests compared just a few particles used in the atomic force measurements. Fractal analysis by laser scattering to examine the structures of flocculated aggregates showed that there were optimum mixing speeds and flocculant dosages to produce flocs with compact structure of fractal dimension greater than 2.

Application of shear to pre-sedimented flocs resulted in significant additional sediment consolidation. In this approach, flocculation and settling were partially decoupled from consolidation, allowing flocculation to be optimised for fast settling. Subsequent application of shear to the settled sediment aided in the removal of inter and intra-floc liquor to improve consolidation and sediment density. While the approach was simple to implement in batch mode, its implementation in a continuous system without restabilising the entire suspension could be a challenge. It is recommended that this approach be tested on a continuous pilot scale system to provide the basis for large scale testing.

Underground

Health and safety, productivity and environment initiatives.

Recently Completed Projects

C26061The Young’S Moduli, Poisson’S Ratios And Poroelastic Coefficients Of Coals

This report describes the measurement of coal (and rock) properties ...

C24015 Assessment Of Convergence Based Roof Support Design For Longwall Abutment Loads

The aim of Stage two of project C24015 was to develop a roof support...

C25072New Approaches To Mine Gas Analysis And Ratios

The spontaneous combustion of coal remains a hazard in underground c...

Underground

Open Cut

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

Recently Completed Projects

C26022Real-Time Prediction Of Coal Top Through Guided Borehole Radar Wave Imaging For Open Cut Blast-Hole Drilling

Damage to the tops of coal seams caused by incorrect blast stand-off...

C26027Using An Ecotoxicological Approach To Validate The DGT Technique For The Measurement Of Bioavailable Metal Concentrations

This project builds on the opportunity identified through Project C2...

C25039Prediction Of Long-Term Salt Generation From Coal Spoils

The release of salts from spoil piles has the potential to affect su...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C250083D Flotation Of Fine Particles

In this project a process for the continuous, selective agglomeratio...

C20052Full Scale Gravity - Desliming Using Cascading REFLUX Classifiers

Considerable quantities of fine coal are disposed of as part of the ...

C26007 Revised Dustiness And DEM Test Method (Update Of AS4156.6) Part 2:Preparation

In 2015 project C23054 investigated and reviewed the Australian Stan...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C25045Stage Two - Assessment Of In Situ High-Temperature Strength Of Cokes

Stage I of this project established a reliable and repeatable proces...

C27003Review Of ACARP Research To Support Marketing Of Australian Thermal Coal

In this project, researchers pinpointed issues relating to the use o...

C25044Trace Elements In Coal; Status Of Test Methods In Use And Their Applicability

 STAGE 1 REPORT

The key objectives of this stage...

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C27008Selective Absorption Of Methane By Ionic Liquids

The connection of a ventilation air methane (VAM) abatement plant di...

C24061Proof-Of-Concept Photocatalytic Destruction Of Methane For Coal Mining Fugitive Emissions Abatement

Australia's fugitive emissions in 2015 were 41 Mt CO2-e (representin...

C23052Novel Stone Dust Looping Process For Ventilation Air Methane Abatement - Phase 3

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