Changes in a Chemical Structure of Brown and Bituminous Coals during Low-Temperature Processing under Various Atmospheric Conditions

Abstract—In this work infrared attenuated total reflection spectroscopy (ATR IR spectroscopy) was used to study changes in the chemical structure of fine particles of brown and bituminous coals during heat treatment at temperatures up to 350°C in an air atmosphere and with a limited amount of air. Additionally, the thermal effects occurred during the coal processing in this temperature range under similar atmospheric conditions were investigated. It is shown that the bituminous coal samples have noticeable changes in the chemical composition starting from temperatures of 200°C when treated in air, and from 250°C for samples obtained in conditions without air access. Meanwhile, the IR spectra of brown coal samples demonstrate changes starting from temperatures of 200°C regardless of atmospheric processing conditions. Differential scanning calorimetry (DSC) in combination with thermogravimetry (TG) allowed to estimate the quantitative content, thermophysical parameters and the nature of the moisture in the samples.