| Fire is one of the main disasters affecting coal mine safety,and it is a difficult problem facing coal mine enterprises in China.Traces of goaf coal spontaneous combustion caused great economic losses,and carbon dioxide fire extinguishing technology has played a great role in traces of prevention and control of coal spontaneous combustion,and ice fire prevention technology capable of cooling and adsorption of the characteristics of inert gas,oxygen insulation,however,the study of ice fire prevention technology is relatively small,and dry ice sublimation rate is too small can't meet the requirements of mine fire prevention.In this paper,the sublimation rate of dry ice is studied theoretically and experimentally,and how to accelerate the sublimation of dry ice is designed.In this paper,the time and heat required for quantitative dry ice sublimation are theoretically calculated and analyzed,and the variation law between the sublimation rate and the height of the cylinder when the dry ice accumulates into a cylinder is analyzed.The sublimation rate of dry ice is 0.856g/s?0.899g/s(4.28×10-4m3/s?4.50×10-4m3/s)when the tiling thickness of dry ice is 0.282m?0.427m or the height of piled cylinder is 0.565?0.855 m.When the height of dry ice cylinder is 0.565m?0.58m,the sublimation rate of dry ice is the fastest,which is 0.899g/s.Under the condition of wind,the wind speed of the inlet is 1m/s?4m/s,and the sublimation rate of dry ice is 0.00138m3/s?0.00783m3/s when it is 0.1m?0.8m from the front edge of the slab.Experiments show that the sublimation rate of dry ice in the case of airtight and no wind is slower than that in the case of airflow.The larger the airflow is,the faster the sublimation rate of dry ice will be.It can be seen from the experimental results that the sublimation rate of dry ice in natural state is very small.By changing the air flow through the device,the sublimation rate of dry ice is also changed.When the wind speed is 0.5m/s,the sublimation rate of dry ice is up to 0.0404g/s.According to the theoretical analysis of dry ice sublimation rate and related experimental research,and combined with the characteristics of actual goaf,the dry ice phase change fire prevention device is designed,which includes the design of dry ice storage device,heating drive device and antifreeze device.The size of the device is designed to be 200cm×100cm×100cm.The raw material of the heating drive device is calcium oxide and water with a mass ratio of 1:1.3,and the antifreeze is calcium chloride aqueous solution with a concentration of 30%.Finally,through numerical simulation,the distribution of the goaf flow field is analyzed without dry ice and after dry ice is put into the goaf,and the effects of different flow rates of carbon dioxide,different release locations and different air intake on the flow field and oxygen concentration field in the goaf are simulated.There are 32 figures,8 tables and 102 references in this paper. |
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