Express determination of coke’s ash content by the gamma-albedo method

Abstract

Continual monitoring of the ash content is required in fuel processing. The traditional thermogravitational method of determining the ash content is not suitable for use on a large scale, since the analysis is laborious, slow, and destructive. The gamma-albedo method lacks the disadvantages of the standard method and provides results of satisfactory accuracy if the chemical composition of the fuel’s mineral component is relatively constant. In the present work, attention centers on the possibility of express determination of coke’s ash content on the basis of the albedo of low-energy gamma radiation from the Fe-55 radionuclide, with corrections for the variable chemical composition—in particular, fluctuations in the calcium concentration in the ash-forming part of the fuel. To take the perturbing action of calcium into account, the X-ray fluorescence of calcium is measured. The ash content is assessed on the basis of the integral intensity of secondary radiation due to the γ-ray scattering and fluorescence of the calcium. It is clear that artificial attenuation of the secondary radiation is required, in view of the qualitatively different changes in intensity of the fluorescence and scattered radiation as a function of the calcium concentration and also the complex dependence of the integral intensity of the secondary radiation on the ash content. A model is proposed for optimizing the thickness of the attenuating filter so as to ensure equal and opposite changes in the intensity of the fluorescence and scattered radiation with variation in calcium concentration. Recommendations are made for practical application of the proposed method, in terms of the attainment of satisfactory accuracy with fluctuation in the ash content and the composition of the mineral mass. The basic metrological characteristics of the traditional and proposed methods are presented, along with the results of experimental trials.