In-situ inorganic analysis of coal seams using a hand-held field-portable XRF Analyser

The major inorganic elements in cores of coal and associated non-coal materials, ranging up to 7.6 m in length, as well as in large, naturally-broken coal blocks, have been measured using a hand-held, field-portable energy-dispersive X-ray fluorescence (fp-XRF) analyser, to evaluate the potential of such technology in quality assessment of coal seams for exploration and mine geology programs. Calibration against a suite of independently-analysed coals was used to provide element-specific user factors, which were incorporated into the individual fp-XRF analyses to obtain data on the percentages of Si, Al, K, Ca, Fe, Ti and S, and in some cases Mg and P, at each measurement point. With the exception of (total) S, these values were then recalculated as percentages of the relevant oxides, and combined to provide an estimate of the expected ash yield from the materials concerned. Profiles were prepared illustrating the variation in the different components through seam sections in three different drill cores, based on measurement of points at a 10 mm spacing. Samples of selected core intervals were analysed by conventional techniques, and the ash yield, total sulphur and individual oxide percentages compared to those indicated for the same intervals by the fp-XRF data. Although difficulties were encountered due to precipitated salts and anomalous element concentrations on or near some core surfaces, the results have shown a general level of agreement for the different coal and non-coal materials involved. While the accuracy is not as high as that from conventional methods, the fp-XRF data allow the materials in cores and exposed coal faces to be categorised to an extent that is of value for many research and industry applications.