Devolatilization behaviour of Kolubara and Kostolac lignite (Serbia) during the combustion process: A case study

In this study the devolatization behaviour of lignite samples, of various grain sizes, on a wire mesh reactor is evaluated. Lignite samples were rapidly heated at four different temperatures (300, 500, 700 and 900 °C). The feed lignite reveals a high content of huminite, a low inertinite and liptinite contents in the Kostolac samples and a slightly higher liptinite content in the Kolubara samples. The char obtained at 300 °C and 500 °C shows slight petrographic and chemical changes. The major changes in chemical and petrographic compositions were observed in char heated at higher temperatures (700 °C and 900 °C). FTIR spectral data for both Kolubara and Kostolac lignite samples reveal a decrease in aliphatic- and oxygen­containing structures with increase in temperatures from 300 to 700 °C. The lack of aliphatic and oxygen-containing structures, the breakdown of clay minerals and negligible amount of water are detected in samples devolatilized at 900 °C where aromatic structures dominate.

Huminite reflectance of initial samples confirms the low rank (lignite) of all the samples. Char of all grain sizes obtained at 300 °C and 500 °C showed very small changes in the maceral composition and reflectance value and still corresponded to lignite rank. A significant change in maceral composition and increase reflectance is observed in char obtained at 700 °C and 900 °C of all grain sizes.