Prediction of Self-ignition in Multi-Layer Coal Seams Based on Simulating Airflow Field

摘要

A simplified steady model of air flow diffusion and chemical reaction in loose coal is solved numerically and distribution of oxygen volume fraction and flow velocity magnitude is obtained in present study. The simulating results of oxygen volume fraction and velocity magnitude distribution is compared with critic value as well as duration of self-ignition of coal spontaneous combustion from experiment to partition "three zones"; mining conditions to avoid spontaneous combustion are also obtained. The method is employed to predict spontaneous combustion in multi-layer mining workface in Dongrong No.2 coalmine successfully. The result showed that self-heating zone lies in 50～140 m in the airflow inlet side and in 50-85 m in outlet side away from the workface in the coal pillar. If moving velocity of the workface is larger than 1.6 m/d, there is no danger of spontaneous combustion; while if the workface stopped to move but ventilation kept normal for 38 days, spontaneous combustion will take place in airflow inlet side of the pillar. Compared with predicting spontaneous combustion by numeric modeling the whole process of coal spontaneous combustion, much smaller amount of calculation is required and precision can satisfy the demand of extinguishing and preventing spontaneous combustion by the given method.