Home – Home – Jornals – Chemistry for Sustainable Development 2021 number 5

The granulometric and morphological composition of fine coal powders prepared according to a special technique for the size classes -0.2 +0.1, -0.1 +0.063, -0.063 +0.04, -0.04 mm from ten different grades of coal (B, D, G, Zh, K, KS, OS, SS, T, A) of the Kuznetsk coal basin was investigated. Technical and elemental analysis, petrographic studies were carried out with the coal samples using standard methods. The set of values of the reflectivity of vitrinite, the sum of the fusenized components, the thickness of the plastic layer and the yield of volatile substances allowed us to establish the grade identity of the studied samples in accordance with the unified classification of coals on the basis of genetic and technological parameters. According to the results obtained by SEM, changes in the structure of coals and the relief of the fracture surface pattern are observed in the series of metamorphism of the studied coal samples from brown coal to anthracite. The granulometric composition of coal powders was determined by laser diffraction when the samples were dispersed in an aqueous medium with the addition of a surfactant. The particle size distribution in coal powders of the fraction -0.04 mm for all grades of coal is characterized as monomodal, in the fractions -0.063 +0.04 mm - as monomodal asymmetric, in fractions -0.1 +0.063 and -0.2 +0.1 mm - as bimodal. These fractions contain irregularly shaped particles (needle-shaped, oval), as determined by means of SEM. According to the results of the studies of KS grade coal by means of NMR spectroscopy, it is established that the content of aliphatic carbon (CH₃) in the samples increases insignificantly with a decrease in the size of the coal powder fraction - from 3.05 % for the fraction -0.2 +0.1 mm to 3.73 % for the fraction -0.04 mm. The values of the aromaticity index f _a for all fractions remain constant.