Thermal decomposition and combustion of coals, fuel wood, and hydrolytic lignin, as studied by thermal analysis

Abstract

Different biofuel woods (spruce, pine, and spruce and pine bark), hydrolytic lignin, and coals from different deposits [D coal from Inta, Zh coal from Vorkuta, and D coal from Khakassia] were studied on a synchronous thermal analyzer at heating rates of 5, 10, and 20 K/min in inert and air atmospheres. Classical thermogravimetric and differential thermogravimetric curves were obtained to describe the thermal decomposition of hemicellulose, cellulose, and lignin and the combustion of a carbon residue as the main components of the biofuel woods. The decomposition of the coal fuels from different deposits was studied, and the temperature ranges of drying, the release of volatile substances, and the combustion of carbon residues were obtained. The results of thermal analyses were processed with the use of an isoconversional method based on the Friedman and Ozawa–Flynn–Wall models and with the aid of an extended independent parallel reaction (EIPR) model. A satisfactory repeatability of the results was obtained to indicate the applicability of both of these methods. The subsequent study of wood, hydrolytic lignin and, coals from different deposits was carried out with the aid of the EIPR model. The activation energies of biofuel woods varied in a range from 62 to 93 kJ/mol, which are much lower than those of coals (104–116 kJ/mol).