Comparison of methodological approaches to the determination of organic carbon in wastes of mining, processing and combustion of coal

Abstract

The content of organic carbon is one of the key indicators in determining the areas of using waste of mining, processing and combustion of coal. The measurement results obtained by existing measurement methods are often incomparable to each other, which does not allow obtaining a reliable information about the waste composition. The goal of this study is to generalize current methodological approaches and choose the most effective one for determining the content of organic carbon in samples of waste of mining, processing and combustion of coal. Three most appropriate methods were selected proceeding from the analysis of the methods used for determining organic carbon in various natural and technogenic objects. Method No. 1 is based on the calculation of organic carbon content as the difference between total carbon measured by a CHN analyzer and carbonate carbon determined by the gravimetric method. In method No. 2, the determination of organic carbon content is carried out through the determination of the ash, moisture and carbonate carbon content. Method No. 3 includes demineralization of the sample with hydrochloric acid, drying, and calcination of the resulting residue. The samples of waste of mining, processing and combustion of coal with mass fraction of organic carbon from 0 to 60% were used as objects of the research. According to the results of experimental studies and taking into account possible limitations, measurement procedure based on method No. 3 for determining the content of unburned carbon in ash and slag from a thermal power plant was chosen. The applicability of the newly developed measurement procedure was verified for an extended area of objects, which includes, in addition to the samples of coal combustion waste, the samples of waste of their mining and processing. The comparability of the results obtained by other methods was demonstrated, and a preliminary assessment of the metrological characteristics was performed. The measurement procedure can be used in analysis of the reference samples used for construction of the calibration characteristics in the determination of organic carbon by instrumental methods, as well as in the determination of the metrological characteristics of the reference materials of the composition of waste of mining, processing and combustion of coal.