Gasification profiles of Thrace region coal under CO2, N2/CO2, and N2/DRY air environments

Abstract

This research aimed at understanding the gasification behaviour of Thrace-Saray region coal by conducting several thermogravimetry analysis (TGA) experiments. The effects of heating rate (20–50 °C/min), final gasification temperature (750–950 °C), and isothermal gasification duration (60–120 min) on the overall gasification processes of as received and washed and dried coal samples were determined under CO2, N2/CO2, and N2/dry air environments. Three main reaction regions were observed in CO2 and N2/CO2 gasification experiments. Regions were correlated with the moisture loss and initiation of devolatilization of labile volatiles (50–200 °C), the main pyrolysis stage (200–600 °C), at which the comparatively stronger bonds break and devolatilization of heavier volatiles with char evolution occur, and the final gasification stage (>800 °C) respectively. Obtained thermogravimetry and differential thermogravimetry (TG/DTG) curves were further interpreted based on reaction initiation temperature, peak temperature, maximum mass loss rate, and residue percentage. Based on the evaluated parameters, higher gasification temperature (950 °C), longer isothermal duration (120min.), lower gas flow rate (60 ml/min), and the lower heating rate (20 °C/min.) for the CO2 gasification process and-comparatively higher heating rate (40 °C/min.) for the N2/CO2 gasification process were found to be the optimum conditions for both of the specified coal samples. The observation of fourth reaction region in N2/dry air experiments increased the complexity of the analysis and the distinction between the combustion and the gasification reactions. In all experiments, gasification reactivity of the washed and dried coal sample was found to be higher than that of as received coal sample.