Thermal behaviors and kinetic characteristics of coal spontaneous combustion at multiple airflow rates by TG − DSC

Air leakage rates are a crucial factor affecting the oxygen supply and heat storage capacity of coal spontaneous combustion (CSC) in goaf in underground coalmines. A suitable airflow rates in goaf can significantly promote CSC. To accurately reveal the effect of airflow rate on CSC, a bituminous coal was selected, and the thermogravimetric and differential scanning calorimetry were used to receive the mass loss characteristics and enthalpy changes for sample. Six characteristic temperatures and five reaction stages were identified under multiple airflow rates, the combustion characteristics were calculated, and apparent activation energy was obtained by Coats–Redfern, FWO and Starink methods. The results indicate that with the increasing airflow rate, the characteristic temperatures decreased firstly and then rose, of which all characteristic temperatures at 150 mL min−1 were the lowest. Meanwhile, the stability and combustion capability of sample were prominently enhanced, and its exothermic ability and heat release enlarged, and the reaction capability with oxygen was the highest at 150 mL min−1. Then, the Avrami–Erofeev equation (n = 3/2) was verified to be the most appropriate mechanism of the coal sample. In addition, apparent activation energy of sample was the lowest at 150 mL min−1, and the CSC ability was sensibly strengthened. The findings will serve as a theoretical basis for the initial stage on CSC in underground coalmines.