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Keywords: Coal, Ash content, X-Radiometric, Accuracy.
In studying coal with geophysical methods there is used gamma-gamma method based on detecting scattered gamma-radiation, the intensity of which depends on the coal effective atomic number Z. Most coal deposits are characterized by the dependence between coal Z and its ash content A. The unequivocal character of the given interconnection Z and A depends on the material composition of the mineral part presented both by light (Al, Si, Mg) and heavy (Ca, Fe) components. Redistribution of the component composition of the mineral (ash-forming) coal part leads to gamma-absorbing and scattering coal characteristics which is accompanied by the decreasing of the accuracy of coal ash content estimation. The most destabilizing affect on the scattered gamma-radiation method depends on fluctuations of heavy ash-forming components content. This destabilizing affect can be weakened by the compensation principle consisting in detecting scattered gamma-radiation together with X-ray fluorescence of a heavy element. The possibility of such a compensation is based on qualitatively inverse laws of the intensities of scattered and X-ray radiation changes depending on a heavy ash-forming element content. By means of measuring the integral intensity of the secondary radiation there is achieved a certain compensation of the exciting affect of varying composition. The method given is efficient only at an insignificant ash content dispersion. There are suggested complex methods of ash content express-control in coals according the integral intensity of the secondary radiation taking into account instrumental data about calcium concentration. The informative parameters for the on-line determining of calcium content there is selected the ratio of the secondary radiation integral intensities measured at two different thickness of the weakening filter: less inversion value corresponding to pre-inversion region for coals with minimum ash content and more inversion thickness corresponding to post-inversion region for coals with maximum ash content. In the process of nature studies at the Karaganda coal deposit mines there is achieved a satisfactory accuracy of quality estimation in the conditions of significant variability of ash content and material composition.
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