Study on the heat removal efficiency of thermal probe on coal stockpile under different arrangement and ambient air velocity

摘要

In recent decades, the spontaneous combustion of large-scale coal stockpile was frequent, seriously causing the waste of resources and environmental pollution. The ambient airflow was one of the factors that induced it occurred. In this paper, based on the principle of heat removal by thermal probe, we conducted a simulated experiment to study the heat removal effect, such as the temperature difference and heat removal ratio, heat removal radius, and cumulative heat removal volume, in a coal stockpile as its internal temperature increased from 100 to 150 oC under different experimental conditions. The results showed that the scale of temperature drop at designated point in the coal stockpile were 46.3%, 10.8%, and 32.8% that under the above experimental conditions, respectively. A comparison study found that as the insertion angle of thermal probe in the coal stockpile was 60 degree, the heat removal efficiency of thermal probe was significantly affected by outside circumstance, and is highly sensitive to airflow. For instance, as the thermal probe insertion scale was 1:4, outside air velocity was 2 m/s, and inserted angle of thermal probe was 60 degree, the average radius of heat removal by thermal probe was 5.79 m (maximum heat removal radius), and the overall heat removal efficiency of thermal probe was enhanced by 79% and 93% that in a constant temperature circumstance (100 and 150 °C), respectively. Therefore, it can be concluded that the suitable arrangement of thermal probe in the coal stockpile was advantageous to heat removal. This paper provided a new technical approach and theoretical basis for the prevention and control of coal spontaneous combustion for large-scale coal stockpile under different conditions.