| With the continuous improvement of mining mechanization,the mining intensity and production concentration of coal mines are also increasing,and the harm of mine dust is becoming more and more serious.The "14th Five-Year Plan" puts forward the intelligent construction of mines and takes it as the main supporting field of coal science and technology,which is an inevitable requirement for the technological progress of the coal industry and is of great significance to improve the technological revolution of coal mines.In order to improve the intelligent construction of mines,ensure safe and efficient production in coal mines,and realize the grading and intelligent control of dust in the comprehensive excavation work.In this project,the dust production and dust diffusion characteristics of the excavation face and the spray dust reduction technology are comprehensively studied,the installation location of the dust reduction device is determined through the study of the dust production and dust diffusion characteristics,the dust concentration is divided into dust concentrations for the study of gas-liquid two-phase spray dust reduction,which provides theoretical support for improving the dust reduction efficiency of the dust reduction system,and finally develops an intelligent spray dust reduction system to achieve dust classification control.The main findings are as follows:The results show that the total dust concentration tends to be stable after 32m from the boring surface,the cumulative settlement rate reaches about 40%,and the respiratory dust tends to stabilize after 24m from the tunneling surface,and the cumulative settlement rate is about 13%,indicating that in the process of natural dust settlement,the respiratory dust is suspended in the air for longer and more difficult to settle,the farther away from the boring face,the proportion of respiratory dust in total dust is higher and higher,and the concentration of respiratory dust in the process of dust diffusion is faster and more stable than that of total dust.Under the same working conditions,the average volume diameter of extremely hard coal dust production was 15.57μm,and the cumulative proportion of respirable dust was 52.61%.The average volume diameter of hard coal dust production was 23.65μm,and the cumulative proportion of respirable dust was 37.79%.The average volume diameter of medium hard coal dust production was 30.89μm,and the cumulative proportion of respirable dust was 26.41%,indicating that the larger the solidity coefficient of the coal rock,the more divergent the dust generated during cutting,the more fine dust produced,the more respiratory dust.The monitoring data of coal rock dust concentration with different solidity coefficients showed that under the same cutting conditions,the total dust concentration was negatively correlated with the solidity coefficient,and the larger the solidity coefficient,the lower the total dust concentration generated during the cutting process.The breath dust concentration is positively correlated with the solidity coefficient,and the higher the solidity coefficient,the higher the respiratory dust concentration generated when the coal is cut and broken.The longitudinal diffusion law of dust was studied by FLUENT simulation of full-size roadway,and the results showed that within 20～30m from the end of the boring surface,the dust pollution area diffused from the return air side to the full section of the roadway,forming vortices at the boring surface and thus causing the formation of dust accumulation area at the TBM driver position,so for the dust control of the tunneling alley,the return air side should be focused on prevention and control in the first 20m to prevent the dust pollution area from expanding to the full section of the roadway.When spraying dust reduction in the roadway,the best installation location of the spray bracket should be 20～30m away from the boring surface.Through the self-built gas-liquid two-phase nozzle spray dust reduction experimental platform,the dust reduction efficiency of different dust concentrations with different spray parameters is studied.Then,the research on the spray coverage and flow characteristics of gas-liquid two-phase nozzles was carried out,and the results showed that the effective coverage width of a single nozzle with good dust reduction effect was more than 0.8m,and the effective coverage length was 1.3m.Regardless of the gas supply and water pressure ratio of the gas-liquid two-phase nozzle,the gas and liquid flow affect each other,and there is a certain relationship between the water flow rate and the gas-liquid flow ratio,the fitting curve is approximated:Ql=e[3.88-0.01(Qg/Ql)+1.58×10-5(Qg/Ql)2];Then,the research on the relationship between dust reduction efficiency and gas-liquid flow was carried out,and the dust was divided into three grades above 0～250mg/m3,250～350mg/m3 and 350mg/m3 according to the results.Find the gas-liquid flow relationship with higher dust reduction efficiency for different dust concentrations,When the dust concentration is 0～250mg/m3,Qg is within 1900～2200L/h,Ql is within 27～34L/h,when Qg=1861.26+3.1617×106×O.71Ql is met and Qg is slightly greater than Ql,the dust reduction efficiency can reach more than 90%;When the dust concentration is 250350mg/m3,the concentration of droplets in the fog field needs to be increased for the dust reduction efficiency to increase to 90%;When the dust Qg is within 2050～2200L/h,and Ql is within 30～34L/h,when Qg=3209.8-33.5Ql is met and Qg is slightly greater than Ql,the dust reduction efficiency can reach more than 90%;When the dust concentration is above 350mg/m 3,a smaller gas-liquid flow ratio and a larger liquid flow rate are adjusted under the law of formula Ql>e[3.88-0.01(Qg/Ql)+1.58×10-5(Qg/Ql)2].According to the divided dust concentration grade,the optimal dust reduction gas-liquid flow rate corresponding to different dust concentrations is given as follows:2000L/h and 30L/h;2100L/h、32L/h;2000L/h、40L/h。According to the research results,an intelligent dust reduction system was developed,the dust concentration was intelligently graded and controlled,the optimal gas-liquid flow ratio was set for different grades of dust concentration to achieve efficient dust reduction,and the best installation location of the intelligent dust reduction system was determined to be 20m away from the comprehensive excavation face.Finally,industrial application was carried out in the 5109 material tunnel excavation lane and some transfer points of Tianshan Russian Mine,and the intelligent control effect and dust reduction effect were verified,The results show that the dust reduction effect at the tunneling lane and the transfer point is good.The Thesis includes 79 figures,27 tables and 91 references. |
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