Profiling of inorganic elements in coal seams using laboratory-based core scanning X-ray fluorescence techniques

Abstract

The major inorganic elements in cores of coal and interbedded non-coal materials, ranging from 0.9 to 1.7 m in length, have been evaluated using energy-dispersive X-ray fluorescence (ED-XRF) measurement at close-spaced (2 mm) intervals in a laboratory-based Itrax core scanner, to evaluate the potential of this type of technology for use in quality assessment of potentially mineable coal seams in exploration and mine geology programs. The ED-XRF measurements from the scanner were calibrated against a suite of independently-analysed coals to provide quantitative data on the percentages of Si, Al, K, Ca, Fe, Ti and S at each individual point. With the exception of (total) S, also used in quality assessment, these values were recalculated as percentages of the relevant oxides, and combined to provide an estimate of the expected ash yield. Profiles were prepared illustrating the variation in the different components through the seam section, plotted alongside optical and X-radiograph images of the scanned core. Samples of selected 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 core scan data. Despite difficulties due to precipitated salts and anomalous element concentrations on or near some core surfaces, as well as differences in moisture content between the scanned core and the conventionally-analysed samples, the results of this cross-checking have shown a general level of agreement for the different coal and non-coal materials involved. While the precision is not as high as that from conventional methods, the scan data allow the materials in the cores, including composites representing potentially mineable intervals, to be categorised to an extent that is of significant value for many exploration and mine geology applications.