The combustion performance and kinetics of Saray-Thrace region coal: The effects of particle size and heating rate

Abstract

This research aimed at understanding the effects of particle size and heating rate on combustion characteristics and kinetics of Saray-Thrace region coal by performing thermogravimetry (TG-DTG) analysis. The TG-DTG curves revealed two main reaction regions for each heating rate studied (5, 10, and 15 °C/min, particularly the evaporation of moisture and carbonization stages. The reaction intervals extended while the corresponding peak and burn-out temperatures increased as the heating rate was increased. Furthermore, a slight delay occurred in burn-out temperatures while the peak temperatures mostly increased with increased particle size, which is correlated with the decrease in surface area. On the other hand, the average mass loss percentages in carbonization stages mostly increased with increased particle size. Similarly, the combustion performance and reactivity of coal samples, which were evaluated through the values of combustion performance index (S), maximum reactivity (Rmax), and ignition index (D), suggested that the larger the particle size and the higher the heating rate, the better the combustion activity. The kinetic analysis of coal samples was also performed using model-free (iso-conversional) methods, particularly the Ozawa - Flynn - Wall (OFW) and Kissinger - Akahira – Sunose (KAS). The corresponding average activation energy (Ea) range of different size coal samples varied within the range of 62.1–191.8 kJ/mol, and the lowest Ea found for the largest particle size coal sample, supported the ignition performance and reactivity results.