Study On Prediction And Cooling Methods Of Seasonal Thermal Hazard In The Mine

Thermal disaster in mine is the 6th major disaster after that of roof, gas, fire, water and dust, and it is considered as the four occupational hazard factors in the mine together with dust, noise and toxic and harmful gases seriously threatening the miner’s safety and health. Along with the increment of mining depth, the geothermal temperature increases and the temperature of surrounding rock increases. Especially in the summer the temperature of the ground is high, the temperature of the working place in mine is increased. Thus the degree of the thermal disaster is increased significantly, and the existing cooling methods are difficult to meet the specification requirements.Based on a large number of surveys and a testing analysis of the high temperature geothermal disasters in Shandong Juye mining area, the paper masters the influence of ground surface climate one year to the climate in mine. The formation characteristics and influence factors of the seasonal heat disaster in the mine are suggested. Therefore, in order to master the mine seasonal heat harm and its control method, the numerical analysis of transient temperature field of surrounding rock under the seasonal wind temperature action, the prediction of wind temperature and the cooling methods are studied in the paper. And the paper obtains the following main innovations.The thermal conductivities of 8 groups of air duct, coal and rock mass are tested of temperature at 10~60℃ by laser thermal conductivity meter, which provide the basic parameters for predicting the temperature field of surrounding rock. According to the temperature of mine airflow and the temperature field of surroundings rock exists the interaction relationship, this paper establishes a calculation model of the roadway temperature field distributed in unsteady air temperature. Using the finite difference method calculates the cooled zone temperature field distribution and the corresponding software is compiled. Through it the temperature field of surrounding rock is calculated under the influence of the seasonal wind temperature in the mine. The distributed optical fiber temperature measurement system is used to test the temperature field of surrounding rock, and the results are in agreement with the predictions. Based on the variation of cooled zone temperature field, which is under the seasonal variation of wind temperature, the mechanism of the formation of the seasonal thermal damage in underground mine is revealed. This provides a theoretical basis for the implementation of the ground wellhead refrigeration and dehumidifying the ventilation airflow.To have an accurate grasp of the mine airflow temperature and humidity under the seasonal climate impact, to predict underground thermal damage distribution, the paper analyses various heat source temperature prediction model of the wind. It also puts forward the airflow temperature and humidity prediction models based on an overall mine ventilation network solution. Using the air temperature prediction model in single roadway, the air volume is known. But, because of the large differing temperatures and other factors in mine ventilation network, natural wind pressure has a great influence on air distribution. The paper considers the coupling relation between air temperature and air volume. The paper develops the software for calculating the temperature of airflow and humidity in the mine roadway based on an ObjectARX platform. The ventilation network in Zhao coal mine is simulated. The temperature and humidity of the 1307 mining face and the 3303 mining face are measured on the two ventilation routes. The measured results are in agreement with the predicted data. Thus, the temperature and humidity in mine can be predicted through the analysis software, and it provides a important basis for geothermal disaster analysis and the design of cooling system of mine.According to the formation characteristics of the seasonal thermal disaster in the mine, a mine cooling process with full ventilation volume is put forward to eliminate the heat damage in the summer. The air heat and humidity will be stayed on the wellhead. Because the mine total air volume is large(20000m3/min), a non-power air heat exchanger is designed for the cooling of pithead. The heat resistance is 24~45 Pa, and the average leakage rate is 8~9%.As the wellhead is the transport channels and difficult to be closed, the method of the automatic door locking wellhead is proposed. The main and auxiliary shaft mouth cooling air chamber is formed. So the system ensures a good cooling effect of the intake of airflow in the shafts.Through a practical operation in Zhaolou coal mine of Juye mining area, the cooling system can reduce the wind temperature of all the intake airflow to 10~15℃ both in main and auxiliary shafts. The air temperature is droped on the inlet air route 4~5℃, the humidity is droped 15%, the mining face supply air temperature is below 26℃. The labor production environment is significantly improved. The technology of full ventilation volume cooling process is proved practical to solve the problem of Zhaolou seasonal thermal disaster deep in mining. The research to high temperature mine cooling provides a new thinking and new method. The research results could be used as guidance to other types of high-temperature geothermal disaster in mine.