Application of high-resolution X-ray microcomputed tomography for coal washability analysis

Float and sink testing is the standard laboratory method for determining the coal washability characteristics using heavy liquids. In this paper, we describe an alternative technique for determining coal washability using High-Resolution X-ray Microcomputed Tomography (HRXMT). Specifically, the application of HRXMT and specialized software have enabled us to determine the particle characteristics of coal samples with the considerable details needed for building washability analysis. Coal samples taken from the feed streams to the dense medium circuits at two plants in Australia were obtained, characterized and used in the analysis. The coal samples were fractioned into the size and density fractions using sieves and heavy liquids as per the Australian Standard AS 4156.1-1994. The fraction-averaged densities were determined using helium gas pycnometry. The float and sink results were obtained for calibration and validation of the HRXMT results. Our results show that HRXMT can be used to perform coal washability analysis. It provides a new methodology for non-destructive and non-toxic determination of coal washability data. It is safe and fast. Significantly, the successful applications of X-ray computed tomography to perform coal washability analysis would allow for developing an on-line coal washability monitoring system, which would not be achievable with the traditional float-and-sink analysis.