Chapter 2: Characterisation, Classification and Properties of Coal Combustion Products


David French, CSIRO Division of Energy Technology
Ken Riley, Retired (Formerly CSIRO Division of Energy Technology)
Colin Ward, UNSW


A number of different types of properties may be significant in characterising coal combustion products, and in evaluating their use in different markets and applications. For some purposes, such as evaluating the links between feed coal and ash characteristics, it is also necessary to obtain similar information on the coal itself, for example the coal’s mineral matter characteristics (Ward 2002; Vassilev & Tascon 2002; Suárez-Ruiz & Ward 2008a), or on gases, slags and fouling deposits associated with the coal utilisation process (Carpenter et al. 2005; Suárez-Ruiz & Ward 2008b).

The principal techniques that may be used to evaluate the physical, chemical and mineralogical properties of fly ash and other CCPs are summarised in this section. These and other techniques are also described in a review paper by Vassilev and Vassileva (2005). Data derived from the different techniques, with special reference to the ashes from Australian and some overseas power stations, and the relation of the ash properties to relevant feed coal characteristics, are summarised in the remainder of the chapter. The information is intended to serve as a guide to ash producers and ash users on how ashes and other CCPs can be characterised for different purposes, and also to how factors such as coal source and combustion conditions may affect a number of key ash properties.


  1. 2.1 Analytical Techniques for Ash Characterisation
    1. 2.1.1 Particle size distribution
    2. 2.1.2 Particle density and surface area
    3. 2.1.3 Other physical properties
    4. 2.1.4 Chemical analysis techniques
      • X-ray fluorescence spectrometry
      • Atomic absorption spectrometry
      • Inductively coupled plasma (ICP) techniques
      • Unburnt carbon and loss on ignition
      • Other determinations
    5. 2.1.5 X-ray diffraction
      • Principles of operation
      • X-ray diffraction of coal combustion products
      • Quantitative XRD analysis techniques
    6. 2.1.6 Optical microscopy
    7. 2.1.7 Electron microscopy
    8. 2.1.8 Electron microprobe and similar techniques
  2. 2.2 Physical Properties of Fly Ash
    1. 2.2.1 Particle size characteristics
    2. 2.2.2 Surface area, density and pore size characteristics
    3. 2.2.3 Particle morphology
  3. 2.3 Chemical Properties of Fly Ash
    1. 2.3.1 Major element chemistry
    2. 2.3.2 Unburnt carbon and loss on ignition
    3. 2.3.3 Trace elements
  4. 2.4 Fly Ash Mineralogy
  5. 2.5 Relation of Feed Coal Properties to Fly Ash Characteristics
    1. 2.5.1 Relation of coal characteristics to physical properties of fly ash
    2. 2.5.2 Relation of coal characteristics to chemical properties of fly ash
    3. 2.5.3 Relation of coal characteristics to fly ash mineralogy
  6. 2.6 References

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