Journal of the Southern African Institute of Mining and Metallurgy
On-line version ISSN 2411-9717
Print version ISSN 0038-223X
RICHARDS, J.M.; NAUDE, G.; THERON, S.J. and MCCULLUM, M.. Petrological characterization of coal: an evolving science. J. S. Afr. Inst. Min. Metall. [online]. 2013, vol.113, n.11, pp.865-875. ISSN 2411-9717.
For most of the 20th century optical petrography has been the primary petrological and mineralogical tool used to characterize coal. The development of quantitative SEM-based techniques, e.g. QEMSCAN®, for coal began only about a decade ago. The application of these techniques for coal lagged behind other commodities, but they are currently being developed with the aim to provide 'one complete analysis' for coal. Quantitative SEM-based techniques are supplemented by quantitative X-ray diffraction (XRD). Recent indications are that these more modern techniques cannot replace the 'standard' petrographic and chemical evaluations, but rather complement them where and when required. The great advantage of quantitative SEM-based techniques is that they are very rapid, with the result that large volumes of samples can be processed on a routine basis. This is ideal for coal type identification, since the results can be used in the creation of 'intelligent' composites. This can lead to the more speedy evaluation of coal deposits by reducing the number of samples on which detailed metallurgical and characterization test work is required, without an increase in the overall statistical error of the resource model. Coal petrography, however, remains important for the prediction of the coking characteristics of certain coals and coal products. As a consequence it is therefore important that any coal laboratory be able to produce data with confidence. This requires strict quality control and assurance protocols that adhere to international standards.
Keywords : coal petrography; coking strength; scanning electron microscopy; QEMSCAN®.