Optimum oxidation temperature of coal bed for methane desorption in the process of CBM extraction

To explore the optimum oxidation temperature of coalbed for promoting methane desorption, this paper carried out the experiments based on the self-built coal oxidation heating system in different gaseous environments and the high-temperature and high-pressure gas adsorption instrument. Besides, the effect of methane on free radicals and surface functional groups at the optimum oxidation temperature was studied by using electron spin resonance (ESR) spectrum and Fourier transform infrared spectroscopy (FTIR). The results show that the residual methane is the lowest at the oxidation temperature of 80 degrees C, indicating that 80 degrees C is the optimum oxidation temperature for CBM extraction. At 80 degrees C, the inhibitory effect of methane on the reactivity of coal is stronger and the reactivity can also increase. At low concentration (< 25%), the inhibitory effect of methane on the oxidation reaction of aliphatic hydrocarbon is poor. And the inhibitory effect can be improved by oxidizing and heating coal to 80 degrees C. At 80 degrees C, the inhibitory effect of methane on -OH oxidation is stronger at low methane concentration. Meanwhile, the concentration range of methane inhibiting -OH oxidation can be expanded by oxidizing and heating coalbed to 80 degrees C. The inhibitory effect of methane on -COOH oxidation mainly occurs when methane concentration is high. The concentration can be lowered when coalbed is oxidized and heated to 80 degrees C. -C-O group can be formed only when methane concentration exceeds a certain value, but this initial methane concentration can be lowered when coalbed is heated up to 80 degrees C through oxidation.