Combustion characteristics of low-rank coal chars in O2/CO2, O2/N2 and O2/Ar by TGA

The combustion reactivity of two chars prepared from 2 low-rank coals in Northwest China were studied using a thermogravimetric analyser (TGA). The effects of different atmospheres (O2/CO2, O2/N2 and O2/Ar) and different oxygen concentrations on the combustion characteristics were investigated. The results indicate that both atmosphere and oxygen concentration show effectiveness on combustion of char. Compared with N2 and Ar, CO2 could significantly promote the reaction. When combustion atmosphere changes from O2/CO2 to O2/Ar, the burnout temperature increases by 63.7 and 68.8°C for the two chars respectively. Meanwhile, when the combustion atmosphere changes from O2/CO2 to O2/N2, which is 135.9 and 129.6°C, respectively. An increase in concentration of oxygen can also improve the combustion performance of chars in the test. At the same time, kinetic analysis of the combustion profiles of the chars reveals that both the apparent activation energy E and the pre-exponential factor A increased with increasing oxygen concentration and the compensation effect exists between activation energy E and pre-exponential factor A of chars' combustion.