Correlation analysis between active groups and heat transport characteristics of long-flame coal under oxygen-limited

To analyse the active groups in long-flame coal and its heat transport characteristics under oxygen-limited, a Fourier transform infrared spectrometer and laser flash apparatus were selected, and active groups and thermosphysical parameters of coal were received during 30–300 °C at 5, 7, 10, 13, 17, and 21 vol%, the correlation among them under oxygen-limited were obtained by grey correlation method. The results showed that the contents of –COOH, aromatics –CH, and –CH2 structures were larger than other functional groups at 13 vol%. With rising temperature, an increase in oxygen concentration promoted the reduction of intermolecular hydrogen bonding, –CH3, and –CH2. Compared with content of intermolecular hydrogen bonding at 30 °C, its maximum reduction at 5, 7, 10, 13, 17, and 21 vol% reached 15.75%, 20.56%, 24.37%, 23.02%, 25.73%, and 30.39% at 300 °C. Meanwhile, with elevating oxygen concentration after 210 °C, thermal diffusivity and thermal conductivity gradually enlarged, which was mainly influenced by –CC- and –COOH. The specific heat capacity at 13 vol% was larger than that under other oxygen concentrations, which was mainly influenced by C–O, –COOH, and –CC-. Those findings can provide a theoretical basis for underground coal spontaneous combustion.