DEPENDENCE OF THE ASH CONTENT OF COALS OF VARIOUS DEGREE OF METAMORPHISM ON THE GRANULOMETRIC COMPOSITION

The shortage of traditional coking coals necessitates the inclusion of low-metamorphosed coals of grades DG, G and Zh in the composition of coke charges, the technological properties of which significantly depend on the granulometric composition. In this regard, the study of the distribution of ash content and the yield of volatile substances by fractions of various dispersities acquires both fundamental and applied importance. By the method of sedimentation in a liquid medium, narrow fractions with a predominant particle size from 0.5 to 5.0 microns were isolated from the initial coal grains. The granulometric composition was monitored by scanning electron microscopy; the ash content and yield of volatile substances were determined using standard technical analysis methods. It has been established that the nature of the dependence of ash content on particle size is determined by the brand of coal. For DH and G samples, with a decrease in particle size of less than 1 microns, there is a sharp increase in ash content due to the accumulation of high-ash mineral components in fine grades. In contrast, the ash content of the thinnest fractions of W grade coal decreases, approaching the indicators of the initial coal, which indicates a different nature of the distribution of mineral mass. It is shown that sedimentation separation reduces the ash content of high-ash grade G coal by 7 ‒ 8 % due to the removal of fine high–ash fractions. The prospects of using an ultrafine fraction of W grade coal with a particle size of about 1 microns as a component of the coke charge are substantiated, which makes it possible to regulate its composition without deterioration of ash content.

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