Analysis on the cause of fog under Dongrong No.2 C

Analysis on the causes of fog in Dongrong No.2 Coal Mine preface

coal mine is a complex production system, and there are many factors affecting coal mine safety production. The fog under Dongrong No.2 coal mine not only easily leads to mine hoisting and transportation accidents, affects safety production, but also aggravates the pollution of the working environment and is harmful to human health

the development mode of Dongrong No.2 mine is the zonal development of the main transportation roadway mining area of the vertical shaft, with the development level elevation of -500m and the ground elevation of 66.8m at the end of July 2014. In the upper mining area of No. 1 middle school, there are two dark twisted lanes and the main air intake crosscut. In some periods of the year (especially in summer), the fog is rising, and the visibility is very low, which is less than 2m in serious cases. The foggy environment affects people's vision and mood, reduces labor efficiency, seriously interferes with pedestrians and transportation, and forms potential accident hazards. As the affected roadways are the main production roadways with frequent transportation pedestrians, in order to ensure the safe production and normal working environment of the mine, it is necessary to check the causes of the fog under the shaft "to determine the measures to control the fog

2 occurrence law of fog

(1) the occurrence of fog changes with seasons. The fog in the two dark twisted lanes and the main air intake stone gate in the upper mining area of the first middle school is larger in summer, followed by autumn, and smaller or even no in winter

(2) the occurrence of fog is related to the roadway height. There is no fog in the air inlet roadway. The fog starting point is located about 20m above the bifurcation point of the main and auxiliary winch lanes of the air inlet roadway, and it is foggy until the first working face with an elevation of -325m enters the substation in the wind tunnel

(3) the occurrence of fog is related to the temperature of tunnel airflow. At the first working face with an elevation of -325m into the wind tunnel, the original machine structure of the substation should be changed in the above two schemes. Due to the high temperature generated by the substation and pump station, the fog at the substation is significantly reduced, and the fog at 20m behind the substation completely disappears. After the air flow passes through the working face and return air lane, it enters the return air, and fog appears when it goes up the mountain

(4) the occurrence of fog is related to the opening of the tunnel damper. There are two air doors between the main air inlet roadway of the mine and the auxiliary winch Lane (return air uphill) in the upper mining area of the middle one. If the air doors are opened at the same time, the fog in the return air uphill roadway will immediately increase

3 measurement of on-site meteorological parameters of fog

metal pendulum impact testing machine should calibrate the equipment before leaving the factory

on site sampling for gas analysis. The analysis results show that the composition of the fog is very close to that of normal air, without toxic and harmful gases and other special components, and it is milky white under the light. Therefore, in order to analyze the causes of fog, the meteorological parameters of the place where the fog appeared under Dongrong No. 2 coal mine were measured in summer and autumn

4 Analysis of influencing factors of fog formation

generally, the water vapor in the air is close to saturation. When the meteorological parameters (such as air temperature and atmospheric pressure) change, the saturation ability of the air will be reduced. When the actual moisture in the air is greater than the saturation limit of the air to moisture, the excess moisture will condense into small water droplets, that is, fog will be formed. With the further decline of temperature, the precipitation of water increases, and small water droplets gather into larger beads, which are attached to the roadway wall or the surface of metal equipment. According to the above observation data, analyze the influencing factors of fog formation

4.1 influence of surrounding rock temperature

according to the detailed geological investigation report of Dongrong No. 2 mine, the depth of the constant temperature zone in the mining area is 20m, the temperature of the constant temperature zone is + 5.6 ℃, the geothermal gradient is 2.8 ℃/hm, and the geothermal rate is 35.7m/℃. According to the ground temperature prediction formula tvr=t0+ (z-z0)/g, the average ground temperature of - 500m can be calculated as 19.0 ℃. The main factor that makes the ground temperature change in this area is the natural warming rate, which has no influence of geothermal anomalies, so there should be no big error in the predicted value of ground temperature. According to the actual measurement of the temperature measurement hole in the -500m south wing rock roadway heading face, the original rock temperature is 18.8 ~ 19.0 ℃, which is basically consistent with the calculated value

although the rock wall temperature changes periodically with the seasonal change of the ground, the change of the tunnel wall temperature with long-term ventilation is not as large as that of the air flow temperature, and it also lags behind for a period of time. This is because the heat capacity of roadway surrounding rock is very large, and it takes a long time of heat exchange to make its temperature change significantly, which is commonly known as the heat regulation of roadway surrounding rock