Critical oxygen volume fraction of smothering quenched zone based on closed oxygen consumption experiment

In order to accurately divide the goaf spontaneous three zones,a new method of determining the oxygen con-centration of goaf with closed oxygen consumption experiment was put forward according to the oxygen consumption characteristics of different coals. The thermal equilibrium condition of coal oxidation temperature in goaf and its consis-tency with oxygen consumption rate and oxygen concentration at the lowest temperature were analyzed. Using the self-developed closed oxygen consumption experimental device,the data of attenuation characteristics of coal oxygen con-centration in the device were collected,using the oxygen concentration changes of oxygen consumption rate of coal difference quotient obtained at different oxygen concentrations. The critical oxygen concentration was determined ac-cording to the quantitative relationship between oxygen consumption rate and oxygen concentration. The experiment was carried out on anthracite and spontaneous combustion bituminous coal. The critical oxygen concentration of anthra-cite in the No. 3 coal seam of Changping Mine is 14. 2% ,the critical oxygen concentration of the bituminous coal in the No. 4 coal seam of Jiudaoling Mine is 6. 8% ,and the critical oxygen concentration of bituminous coal in the No. 7 coal seam of Xiaonan Mine is 8. 2% . New method determines the demarcation criteria between the spontaneous zone and suffocation zone according to different coals and coal quality,and based on the different characteristics of oxygen consumption,which is in agreement with the practice in fire engineering.