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Gasification kinetics of Thrace region coal by thermogravimetry analysis

2020-05-01
Kök, Mustafa Verşan
Yildirim, Betul
This study aimed at understanding the gasification kinetics of Thrace region coal samples performing isothermal carbon dioxide gasification experiments at five different temperatures (750, 825, 850, 900, 950 degrees C). Thermogravimetric analysis (TGA) experiments were carried out isothermally on as received, and washed and dried coal samples, proximate and ultimate analyses of which were conducted priority. Firstly, the activation energies (Ea) of both coal samples were calculated using first order kinetics based on maximum reactivity (R-max) and reactivity index (R-s) values in substitution for the reaction rate (k(T)) in Arrhenius equation. In order to check the applicability of this computationally efficient and practical method, the obtained results were then compared with the Ea results calculated by three nth order representative gas-solid kinetic models, namely, the volumetric model (VM), grain model (GM), and random pore model (RPM). VM, GM, and RPM kinetic analyses results proposed almost identical Ea values for the as received coal (139.88 kJ/mol, 138.96 kJ/mol, and 138.87 kJ/mol respectively), which also falls within the 127.11-143.86 kJ/mol range proposed by the Rmax and Rs values. The Ea values for washed and dried coal, on the other hand, were found to be almost identical by the VM and GM (113.07 kJ/mol and 113.68 kJ/mol respectively) while the RPM proposed relatively lower Ea (107.89 kJ/mol). Rmax and Rs values proposed an Ea range of 87.62-102.62 kJ/mol for the washed and dried coal sample.