Coal — Guidelines for application of coal grain analysis

This Handbook has been developed to provide clear and concise background information and procedures for the practical application of coal grain analysis data.  It lays out the applications and clearly describes the limitations of each approach, as well as describing the validation approach that a practitioner may employ for their own purposes.

Coal grain analysis (CGA) provides quantification of the organic and inorganic components in coal based on a semi-automated optical microscopy measurement technique.  CGA specifically provides the data at a particle (grain) level so that the nature and behaviour of individual particles may then be interpreted.

Coal matter composition is determined only to a maceral group level (vitrinite, inertinite and liptinite). Inorganic (mineral) matter is routinely classified into two components, either dark mineral or bright mineral.  The CGA approach may however be employed to identify individual mineral types.

This document sets out recommended practices for applying the results obtained from CGA. It covers particles nominally larger than 0.001 mm with and upper particle size of generally 1mm, but particles up to 4mm may be analysed.

CGA applies the concept of optical microscopy maceral analysis to individual particles rather than to a coal sample as a whole.  It uses the reflectance in air as the criterion for ascribing an individual point (pixel) measurement to particular maceral group. When CGA is applied to a large number of particles which comprise a representative sample, the sum of the CGA data across all particles is considered to be representative of the material concerned.

The collection and collation of data into a CGA Report is undertaken automatically using an image analysis software program (ParIS®) developed and owned by CSIRO.  The CGA approach demonstrates how different fines processes may be configured to achieve significantly higher overall recoveries, whilst also providing the composition information useful to tailor overall CPP product types.