THERMAL DECOMPOSITION OF BARZAS COALS

Abstract

Thermal decomposition processes of two types of Barzas sapromixites - a tile-like modification (“tile”) and a product of its weathering (“exfoliated tile”) - have been investigated in various media (air and helium). It has been shown that in the course of temperature-programmed decomposition (10 °C/min) of these forms of tile-like Barzas sapromixite, in both oxidizing (air) and inert (helium) atmospheres, four main temperature ranges can be distinguished: 1) < 150 °C - removal of adsorbed water (this temperature region is more pronounced for the weathered form of tile-like Barzas sapromixite); 2) 150-350 °C - removal of low molecular weight volatile components of coal in helium environment (with their simultaneous ignition in case of the decomposition in air); 3) 350-550 °C - the temperature region of primary or fast coal pyrolysis in an inert medium; in an oxidative medium, this stage of pyrolysis is accompanied by the burning of released tarry substances; 4) > 550 °C - the temperature region of secondary or high-temperature coal pyrolysis to form semi-coke in helium atmosphere, or the region of burning this semi-coke in air medium. Thermal breakdown processes of “exfoliated tiles” in the temperature range of the most intensive decomposition (350-550 °C) have been found to require less energy consumptions than the similar processes for tile-like Barzas coals (by 72-73 kJ/mol for both gas media of thermal treatment). It is supposed that the differences observed in thermal behavior of Barzas sapromixite forms under investigation may be related to the different contents of mineral components and their effects on the thermal decomposition of coal organic matter.