ACARP ACARP ACARP ACARP
Technical Market Support

QEMSCAN for Characterisation of Coal and Utilisation By-Products

Technical Market Support » Thermal Coal

Published: May 08Project Number: C14073

Get ReportAuthor: David French, Colin Ward, Alan Butcher | CSIRO Energy Technology, University of New South Wales, Intellection

QEMSCAN is an automated electron beam image analysis technique, originally developed by CSIRO, Division of Minerals and now by a CSIRO spin-off company Intellection Pty. Ltd., which has been widely applied in the minerals industry. However, its use in the coal and related industries has been limited. The technique has the potential to provide quantitative mineralogical and textural data for assessing coal behaviour during preparation, in power generation (pf and FBC combustion), coking and steel production, gasification and the management and utilisation of coal by-products and wastes.    QEMSCAN analysis can provide unique phase-specific information not obtainable from other analytical techniques which is of relevance to the coal producing and coal utilisation industries. The methods of data acquisition offer advantages over other SEM based techniques in that measurements are made at the individual pixel level rather than averaging over an area and greater use is made of the chemical composition for phase identification rather than relying upon back scattered electron intensity.  

The objective of this project was to develop new QEMSCAN analytical techniques for coal and coal by-product characterisation that will provide unique phase-specific information that can be used by the coal industry to address technical and marketing issues, to optimise existing utilisation technologies and assist in the development of new technologies.

Sample preparation techniques were reviewed and techniques for the preparation of coke and char samples were investigated. Coal samples are prepared using carnauba wax which offers sufficient contrast to allow the measurement of both coal and inorganic phases, thus enabling the relationships of the organic matter with the inorganic phases to be determined. Samples of fly ash and similar materials can be prepared using standard epoxy resins. Sample preparation techniques for the preparation of coke and char were investigated as carnauba wax and common epoxy resins are unsuitable for the mounting of coke and char samples. Four specialist resins were tested, one of which shows some promise and its potential should be further investigated.

The use of chemistry and/or back-scattered electron intensity to identify individual macerals was investigated. Although chemical differences do exist between the various maceral groups these are insufficient to use as suitable discriminant due to the short counting times used in a QEMSCAN analysis. Similarly, there is considerable overlap in the BSE intensity values so they also cannot be used as a reliable discriminant. The use of optical images and coregistration with the corresponding QEMSCAN images should be investigated as this is considered to be the most promising approach to maceral identification and determination of relationships between the individual macerals and the inorganic phases.

Organically associated inorganic elements such as sulphur, calcium and iron are of interest with respect to utilisation and possible catalytic role of the latter two elements in gasification and coke utilisation. Good sensitivity is obtained for sulphur at the levels typically found in coal and its use as a possible discriminant should be further investigated. The other inorganic elements occur at very low levels and cannot be reliably detected using the current counting strategy. Although the counting time could be extended to increase the sensitivity, to do so would increase the total acquisition time to impractical levels at which the analysis would cease to be cost-effective. If such elements are of interest then the use of other techniques such as electron microprobe analysis should be considered.

High-quality reference energy-dispersive X-ray spectra were collected of typical coal and ash minerals, coal macerals, and ash glass compositions in boiler deposits and gasifier slags and these were used for development, testing and refinement of the SIPs used for coal characterisation. Further work on SIP development is required in specific areas such as reliable identification of the clay minerals and better discrimination of glass compositions in utilisation by-products.

Case studies illustrating how QEMSCAN analysis could be employed were carried out in four areas of coal production and utilisation viz.

  • Coal preparation
  • Pf combustion - Boiler deposits-  Fly and bottom ash
  • Fluidized bed combustion
  • Gasification

It was also intended to investigate potential applications of QEMSCAN analysis to coke and char studies but lack of a suitable mounting medium prevented this.

These case studies have demonstrated that QEMSCAN analysis can provide unique information not readily obtainable by other means. In particular, data can be obtained on particle size and shape, phase identification and abundance, mode of occurrence and association of the identified phases. Unlike other techniques such as X-ray diffraction, QEMSCAN analysis can supply information on variations in chemistry of the amorphous phase which is relevant to issues such as ash deposition in pf boilers and ash behaviour in fluidised bed systems.  

However, it is not an analytical panacea and should always be used in conjunction with other techniques as chemical analysis, quantitative X-ray diffraction analysis, and electron microprobe investigation. QEMSCAN is a beam analysis technique and, as such, has an effective resolution of 1-2μm. Consequently, fine-grained minerals such as dispersed quartz in coal and mullite in fly ash may not be identified and this must be borne in mind when comparing QEMSCAN data with for example, quantitative XRD mineralogy. Also, polymorphs such as those of silica (quartz, tridymite and cristobalite) cannot be identified and phases of similar composition such as hematite and magnetite cannot be reliably distinguished due to the short counting times employed in a typical QEMSCAN analysis.

At this stage of development, QEMSCAN should be used as an investigative tool rather than for routine analysis. To maximise the usefulness of the information obtained from a QEMSCAN analysis, discussion with the client prior to analysis is required so that the nature of the problem to be addressed is clearly understood and the most appropriate data collection strategy can be selected.

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

C29021Assessing The Impact Of Consecutive Night Shifts On Night-Time Alertness, Daytime Sleep And Timing Of The Circadian System

In the Australian coal mining industry, most guidelines for managing...

C33037Quantifying Recharge To Groundwater Systems In The NSW Coalfields (Sydney, Gunnedah And Gloucester Basins)

The purpose of this project was to estimate the rate of diffuse rec...

C26029Geological Controls On Fluorine And Phosphorus In Bowen Basin Coals

Increasing global restrictions on fluorine in product coal prompted ...

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