Coal Preparation

Effect of Various Constitutents on Storage and Transportation of Coal

Coal Preparation » General

Published: July 01Project Number: C6057

Get ReportAuthor: John Chambers, Yan Liu, Alan Roberts | University of Newcastle

The effect of various constituents of coal on the handleability of both raw and clean coal is generally unknown. There is some information on the influence of moisture content, size distribution and clay content on coal handleability. However the overall influence on handleability of the recovery of additional fines or the specific effects of the use of various chemical additives or processing agents used in the preparation of clean coal is generally unknown.

The purpose of this project was to identify the extent of the problem and make recommendations concerning possible solutions. In some cases attention to design detail for various items of handling plant may be sufficient. In other cases management action in modifying the extent to which various chemical additives or processing agents are used, may reduce handling problems in existing plant.

Specifically, the research has involved flow properties testing to characterise coal containing various proportions of additives at different moisture levels.

The project has dealt, in some detail, with the influence of water on the properties of coal. At the more fundamental level, the mechanisms for water retention by coal particles as influenced by particle size and size distribution has been investigated. From a more practical point of view, a significant finding of the research has been the way in which moisture content of coal influences the unconfined yield strength and bulk density.

It has been known for some time that the strength of coal increases marginally with increase in moisture content over the lower moisture range, but then increases rapidly reaching a maximum strength several times in magnitude as the moisture further increases only a few percent. As the moisture content increases beyond that corresponding to the maximum strength and approaches the saturated moisture content, the strength of the coal decreases. As a general rule, the moisture content at which coal reaches the maximum unconfined yield strength usually occurs within the range 65% to 85% of the saturated moisture content.

The research has shown that for a given major consolidation pressure, the bulk density of coal has a minimum value at the moisture content for which the unconfined yield strength is a maximum. This is an important finding that has not previously been known.

The assessment of the handling characteristics of wet coal fines with oil additives has been undertaken. The test work involved trials using four oil types, a light oil (Singer sowing machine oil), a heavy oil (automotive engine oil), unleaded petroleum and diesel oil. The addition of oil to moist coal increases the bulk density and decreases wall friction angles. The tensile strength is increased slightly with added oil. The addition of light oil and heavy oil has opposite effects on the unconfined yield strength of moist coal; the light oil reduces the bulk strength while the heavy oil increases bulk strength.

The results for the diesel oil as a coal additive are the most encouraging. The diesel oil increases the bulk density and reduces the bulk strength, both desirable characteristics. The application of diesel oil as an additive reduces wall friction, the reduction being significant in the case of stainless steel liners. Again, a desirable result. The improvement in handling characteristics are quite pronounced for diesel contents up to 2%, but only marginal for diesel contents in the range 2% to 4%. Beyond 4% moisture content the bulk density increases substantially with increase in diesel content.

The project has involved the development of additional specialised test equipment to complement the standard flow property equipment comprising the Jenike type direct shear test apparatus and compressibility tester. The additional equipment includes an apparatus for measuring the tensile strength of consolidated coal samples, an associated powder packing apparatus, a surface friction coefficient test rig for liquid bubbles and a large Jenike type, direct shear tester which incorporates a 250mm diameter shear cell. It is noted that the standard Jenike shear tester utilises 95mm and 65mm diameter shear cells. The 250mm cell has the advantage of allowing more representative coal size ranges to be tested.

The large shear tester is a sophisticated machine that incorporates a unique, inverted loading arrangement in which the normal load is applied from underneath rather than from the top as in the standard shear tester. This has the advantage of permitting much lower values of normal stress to be applied during shear, a factor relevant to chute design and analysis.

An important advantage of the large shear tester is the hydraulic loading arrangement which allows much higher consolidation pressures to be obtained than is possible with the standard shear tester. This feature, combined with the larger cell diameter to permit more representative particle size ranges to be tested, makes this device particularly suitable for the design of large expanded-flow bins and gravity reclaim stockpiles. For stockpiles, it is possible for consolidation pressures as high as 1 MPa to be experienced at the base of the piles.

Some teething problems have been encountered during the development of this tester these been mainly associated with the stiffness of the machine. However, these problems have been substantially overcome.

The concept of a 'handleability or flowability indices' to rate coals in terms of their degree of difficulty during handling has been developed and is outlined in Appendix B. This can assist coal operators to determine strategies which may be applied for handling different coal types in specific installations. The indices highlight the influences on the coal handling properties of such parameters as particle size, fines content, moisture, temperature and storage time. Apart from providing information on the degree of handling difficulty that may be experienced, the indices can be an indicator as to what conditioning needs to be performed on particular coals to improve its handleability.

For coal, it is considered that the most appropriate test for 'handleability' should be based on the unconfined compression test. This test is simpler to apply than the Jenike direct shear test as used for the flow property tests. Although not part of the original project brief, a prototype tester has been constructed and is yielding promising results.


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...

C28028The Inclusion Of High Interest Native Plants In Mine Site Restoration Programs: Propagation, Translocation And Field Re-Introduction

This report synthesises over 10 years of ex situ and in si...

C27049Mine Machine Radar Sensor Integration

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


Open Cut

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

Recently Completed Projects

C34029Validation Of Laser Induced Breakdown Spectroscopy (LIBS) As A Rapidly Deployable Field Technology To Estimate Coal Quality

Rapid evaluation of a coal resource by in-situ characterisation dow...

C34028Guidelines For Assessment Of Geotechnically Safe And Stable Post-Mining Landforms

The purpose of this project was to develop a guidelines document as ...

C34016Elements In Coal – A Start-To-End Analysis

This project explores the fate and concentration potential of critical e...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C26016Determining The Benefits Of Online Thickener Underflow Rheology Measurements

The aim of this project is to determine how useful the rheology meas...

C33056Modelling And Control Of Classifying Cyclones

Hydrocyclones are one of the key technologies for the classification...

C28056Surface Alloying Of Centrifuge Baskets And Sieve Bends Screen Surfaces To Increase The Service Lifetime

The main objective of this project was to improve the wear resistanc...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C33066Washability And Distribution Of Sulfur And Trace Elements For Different Size And Density Fractions Of Raw Coals

Based on the hypothesis that the levels of sulfur and other toxic tr...

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...

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


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