Investigation of Tabas anthracite coal devolatilization: Kinetics, char structure and major evolved species

•No tar phase produced in this thermal treatment of Tabas coal.•Evolution of H2O, CO, SO2, CO2, CH4 and trace of C2H6 and H2 during devolatilization.•Devolatilization yields a more ordered char with higher atomic percent of C and lower O and S.•Iso-conversional model calculated the activation energy of Tabas coal about 312.6 kJ/mol.

The pyrolysis of low-volatile Tabas anthracite coal was investigated by thermogravimetric technique (TGA) in the temperature range from ambient to 1100 °C under non-isothermal heating conditions (1.5, 3, and 7 °C/min heating rates). Higher heating rates showed a small retarding effect on devolatilization toward higher temperatures. Iso-conversional method was used for the kinetic study of non-isothermal Thermogravimetric data. Activation energy calculated for coal conversion of 20-80% was about 319 kJ/mol which may be a result of stable ordered structure of this type of coal. Analysis of evolved gases by Fourier transform infrared spectrometry (FTIR) in 7 °C/min heating rate was conducted for the identification of the gaseous species and their evolution profiles during coal thermal degradation. H2O, CO, SO2, CO2, CH4 were respectively major gases detected in FTIR while C2H6 and H2 were also detected. From X-ray photoelectron spectroscopy (XPS) Cls spectrum, major functional group changes on raw and devolatilized coal surfaces are found to be an increase in ether and carbonyl bond intensity and a decrease in carboxylic bond. It was also showed in XPS wide energy spectra that C atomic percent increased after pyrolysis while O and S decreased.

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