CO release characteristics of coal spontaneous combustion in low-temperature oxygen-deficient environments: coupling effects of temperature, oxygen concentration and time

CO is a colorless, odorless, and toxic atmospheric pollutant. CO is produced at low temperatures from coal residues in underground mining goaf and is emitted into the atmosphere. There’s a good correspondence between CO and coal spontaneous combustion. Recognizing the CO release characteristics in goaf can help improve the effectiveness of preventing coal spontaneous combustion and reduce CO emissions. This study takes three coals with different metamorphic degrees as examples, and carries out continuous isothermal oxidation experiments and temperature-rising experiments, to study the time effect of CO release from isothermal oxidation in low-temperature oxygen-deficient phase. Based on the opposing reaction mechanism of CO release and fundamental principles of calculus, a CO release rate generalized model was established. The study shows that: Under isothermal oxidation conditions, the CO release rate decreases exponentially with time. The CO release rate increases linearly with the increase of temperature and O₂ concentration. Taking the parameters of CO release capacity as a link, the CO release time effect obtained in continuous isothermal oxidation experiment was extended to the temperature-rising oxidation process. The kinetic properties of the CO release process were analyzed by means of equivalent kinetics. The CO release rate generalized model shows consistency with continuous isothermal (mean percentage errors < 3%) and temperature-rising experiments (mean absolute errors < 4.08×10^-6). The model can quantitatively reflect the coupling effects of temperature, O₂ concentration and time on the CO release rate, and can predict CO release rate at any temperature and O₂ concentration change course.