Three dimensional coal characterisation (maceral, mineral and cleats) by means of x-ray microfocus computer tomography (žct

One of the aims in coal quality studies, coal bed methane extraction studies, and research on environmental impact of coal, is a full 3D-quantitative characterisation of coal maceral content and distribution, mineral content and cleat system distribution. X-ray microfocus computer tomography, which is a non-destructive technique enabling virtual slicing opaque objects, is an excellent tool.Stacking several slices enables 3D visualisation of the object. The final images show differences in linear attenuation coefficient of X-rays. This linear attenuation coefficient depends on the density and the atomic number of the object. Consequently, components that differ in these parameters can be distinguished. A calibrated dual energy technique allows to extract quantitative information on density and atomic number of the constituents and thus enable maceral and mineral characterisation.The optimal resolution of this technique is 10 ľm in three dimensions, which is far better than for classical medical CT (500 × 500 × 1000 ľm) used in earlier studies. For this purpose, a correlation between microfocus computer tomography data with data of colour image analysis of reflected light microscopy and with back-scattered electron microscopy data allows maceral and mineral characterisation in three dimensions. Moreover, a calibration with an artificial object with several fracture apertures enables the quantification of cleat sizes.