In coal mining, operative monitoring of the ash content is necessary during the actual winning process, e.g., on the conveyor belt.The traditional method of igniting the specimen and weighing the unburnt residue is fairly accurate, but laborious and slow. Promise is shown by nuclear methods based on the absorption and scattering of soft y rays. A number of authors have proposed that the ash content should be measured by means of the scattering of 8 rays or by neutron or density Y--7 methods.However, these methods are difficult to apply when the ash concentration is high and the requirements for accuracy are stringent.The intensity of the scattered radiation and the degree of absorption of y rays by the specimen depend on a number of factors, including the effective atomic number Zef f and the density p of the medium.If there is a unique relation between z_ff or p and the ash content of the coal, then we can estimate the ash content from the measured intensity of scattered radiation or the degree of absorption of y rays with constant measurement geometry. Coal is a complex geological material consisting of combustibles and ashes.It can be regarded as a two-component mixture of carbon (z~) and ash (z2) and then the variation of Zef f with the ash content (for low-energy ~ quanta photoelectric absorption predominates) can be written [i] in the form D ~~\ J'a where the Pi are the contents of the components with atomic numbers z i in the mixture.Calculations for coals from Ekibastuz reveal that the atomic numbers of coals with various ash contents range from 6.0 (pure carbon) to 13.1 for an ash content C of 90%, so that a 10% increase in ash content causes a 1.7% increase in Zef f.From the fundamental law of attenuation of y rays [2] we can determine the concentration,For such a medium, the error of the determination is governed by the relative error of the change in intensity AI/I: 1 AI 1 AI AC = m (~q-~L~)'7 = ~'7 ; (3)it decreases as the relative sensitivity S increases. In turn, the latter depends on the thickness m of the absorber and the mass attenuation coefficients ~ of the elements of the first and second media.V. I.

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