A study of combustion characteristics of pulverized coal in O2/H2O atmosphere

Abstract

Oxy-steam combustion technology in which the mixtures of oxygen and steam are used as oxidizer instead of air is a new generation oxy-fuel combustion technology. The combustion characteristics of SH and PDS pulverized coal in O2/H2O mixtures are studied using non-isothermal thermogravimetric analysis technology in this paper. The effect of combustion atmosphere, oxygen concentration, heating rate and particle size on the combustion characteristics of SH and PDS pulverized coal in O2/H2O mixtures are analyzed based on the combustion profiles and kinetic analysis. The results show that replacing the inert N2 gas in the oxidizer with steam delayed the burning process of SH and PDS pulverized coal. With the increasing of the oxygen concentration, the ignition Ti and burnout temperature Th decrease and the comprehensive combustibility index S increases both in O2/H2O and O2/N2 atmosphere. In O2/H2O atmosphere, the combustion of SH and PDS coal occur in a higher temperature region as the heating rate increases, but the increase in heating rate can enhance the coal combustion property. As the particle size decreases, the maximum mass loss rate increases and the ignition and burnout temperature decrease. The results of kinetic analysis indicate that the combustion reactions of SH and PDS pulverized coal in O2/H2O mixtures follow the first-order kinetics through linear fitting of experimental data using Coats–Redfern integral method, and compensation effect exists between apparent activation energy and pre-exponential factor in different oxygen concentrations during coal combustion in O2/H2O mixtures.