Key Parameters of Preventing Spontaneous Combustion of Coal Stockpile Based on Heat Transfer Technology by a Heat Pipe

Over the past few decades, the spontaneous combustion of large-scale coal stockpile is frequent due to natural airflow contacted the surface and entered in the voids of coal stockpile, coal is oxidized and accumulated the heat, and then coal spontaneous combustion occurred, which seriously caused the waste of natural resources and environmental pollution. In this study, based on the principle of heat transfer by heat pipe (HP), an experiment is conducted to study the effect of heat transfer by HP, such as the temperature difference and heat transfer ratio, heat transfer radius, cumulative heat transfer volume, in a coal stockpile as its heating temperature increased from 100 degrees C to 150 degrees C under the different lab conditions. The results indicated that the average temperature drop scale in the coal stockpile by HP was 46.3%, 10.8%, and 32.8% that under the lab conditions, respectively. A comparison study revealed that as the inserted angle of HP in the coal stockpile is 60o, the heat transfer effect of HP is significantly affected by outside ambient, especially sensitive to airflow. For instance, as the HP inserted scale is 1:4, outside air velocity is 2.0 m/s, the maximum heat transfer radius in the coal stockpile is 49.2 cm, the overall heat transfer effect enhanced by 79% and 93% that with the heating temperature in the coal stockpile is 100 degrees C and 150 degrees C, respectively. Therefore, it can be concluded that the utilization of HP is a reasonable method to remove the accumulated heat in the coal stockpile, as well as the suitable arrangement is also significantly important before this technique is conducted. This study provided a new technical approach and theoretical basis for the prevention and control before the large-scale stockpile has the risk of spontaneous combustion.