A study of coal chars combustion in O2/H2O mixtures by thermogravimetric analysis

Oxy-steam combustion is a new oxy-fuel combustion technology which involves fuels burn in pure oxygen, and the high temperature is moderated using either water or steam. In this study, FG and XS char samples were prepared in a horizontal tube furnace at 1073 K under argon atmosphere. The combustion characteristics and kinetic parameters of FG and XS char in O2/H2O atmosphere were studied using non-isothermal thermogravimetric analysis. The results indicated that replacing N2 by H2O caused the improved in the combustion reactivity and performance of FG and XS char with the identical oxygen concentration. The ignition temperature, peak temperature and burnout temperature in O2/H2O atmosphere were lower than those in O2/N2 atmosphere with the identical oxygen concentration. The activation energy values of FG and XS determined by three mode-free methods decreased with the increasing conversion level, and the activation energy of FG char was less than that of XS char at the same conversion. The kinetic mechanism function calculated result based on the combination of the Popescu method and the Coats–Redfern integral method showed the combustion of FG char in O2/H2O atmosphere followed the first-order chemical reaction kinetic.