Study On Dust Exposure Characteristics Of Respiratory Hemisphere For Different Dust-exposed Coal Miners

With the increasing level of mechanized mining in coal mines,the problem of dust exposure has become increasingly serious,leading to a high incidence and death rate of miners’ pneumoconiosis,and the sampling and detection of coal dust is particularly important.However,at present,coal dust is mainly sampled at fixed points,and there are few individual samples for different types of workers in coal mines,and there is a lack of research on dust characteristics in the respiratory hemisphere of miners.In view of this,this thesis takes the representative dust catcher in coal mine as the research object,and conducts full-term single-sample individual sampling of dust in their breathing hemispheres,measures the dust catcher concentration and operating environment parameters of different miners,and analyzes the physical and chemical parameters such as dust dispersion,free silica content,wettability and shape coefficient.Based on the measured parameters in the field,a physical model of the local roadway and the dust catcher is established,and the distribution characteristics of the flow field and dust field in and around the breathing hemisphere of the dust catcher and the dust concentration changes are investigated by numerical simulation,and a theoretical model of dust exposure characteristics of the dust catcher is obtained.The main conclusions of this thesis are as follows:1)The total dust and exhaled dust concentrations in the respiratory hemisphere area of most of the work types in the coal mine exceed the standard,among which the total dust and exhaled dust exposure concentration of the driver of the continuous mining machine in the digging team is the highest,73.06 mg/m~3 and 22.08 mg/m~3,respectively.The exposure concentrations of total dust and respiratory dust for different types of workers in the production shift are much higher than those in the maintenance shift,but the proportion of respiratory dust concentration to total dust in the maintenance shift is generally higher than that in the production shift,with the highest proportion of respiratory dust concentration being 59.65% for the bracket maintenance worker in the comprehensive mining team.The dust concentration in the coal processing plant is 42.89% to 59.86%,among which the highest percentage is in the screening workshop inspector.The temperature in the working area of the underground mining team and the digging team is relatively suitable,and the wind speed is in accordance with the national safety regulations,but the relative humidity is high,exceeding 85%.2)The proportion of exhaled dust in the breathing hemisphere of the measured work types in the total dust distribution generally exceeds 50%,with the highest proportion of exhaled dust below 5 μm in the breathing hemisphere of the transport team’s maintenance electricians accounting for 83.85%.The farther the miners are from the dust-producing surface,the higher the dispersion of dust exposure,and the dispersion of dust exposure in the overhaul shift is significantly higher than that in the production shift;The percent free silica content of dust in the breathing hemisphere of all the tested jobs is <10%,among which 2.39%～5.47% in the digging team;The contact angle of dust in the breathing hemisphere of all the tested jobs ranges from70.22°～86.70°,which is generally medium.The contact angle of dust in the respiratory hemisphere of the measured work types was in the range of 70.22°～86.70°,which generally belonged to medium hydrophilic coal dust,and the contact angle of dust in the respiratory hemisphere of the work types of the overhaul shift was larger than that of the production shift;The dust in the respiratory hemisphere of the measured work types was irregularly shaped and showed obvious agglomeration.The sphericity of dust ranges from 0.730 to 0.839,among which the sphericity of the dust contacted by the coal processing plant workers is relatively large and exceeds 0.8.3)Under the influence of pressed-in air supply,the distribution of gas-phase flow field in the roadway is complex,and the circulation phenomenon is obvious,and the airflow generated by human respiration has less influence on the overall flow field,but the flow field in the respiratory hemisphere is more obviously influenced by circulating respiration.The dust distribution in the respiratory hemisphere is obviously influenced by the dust producing area and time,and the dust concentration in the respiratory hemisphere reaches the maximum when the dust producing area is located in the middle of the dust producing surface.The overall concentration of both whole dust and exhaled dust in the human respiratory hemisphere tends to increase and then decrease with time,and the concentration in a single respiratory cycle tends to decrease with the inhalation process and increase with the exhalation process.There are 58 figures,24 tables and 99 references in this thesis.