In-situ study on CO/CO2/H2/CH4 emissions during high temperature oxidative pyrolysis of coal via tetrahydrofuran extraction

The study examined the oxidative pyrolysis of raw and residual coals extracted with tetrahydrofuran, as well as the CO/CO₂/H₂/CH₄ emissions at high temperatures (200∼900 °C). Tetrahydrofuran was found to extract aromatic and aliphatic hydrocarbons from lower metamorphic coal, as well as hydroxyl, increasing the specific surface area of char formed by oxidative pyrolysis of residual coal. The CO₂/CO ratio was temperature dependent, and the increase period was fit by a polynomial and a linear function, with critical temperature of around 570 °C. The greater CO₂/CO ratio of raw coal suggested that oxidative pyrolysis produced more CO₂. The kinetic analysis showed that the change in activation energy is inconsistent with the gas production, and the gases were found to be proportionate to the specific surface area of the coal chars, implying that the char structure has a significant influence on gaseous product emissions and the coal oxidative pyrolysis at high temperatures is a diffusion-controlled heterogeneous reaction. The findings of this study could be useful for determining the status of coal fire.