| Objective: China has a large number of coal mining enterprises and a large number of coal mining employees,most of which are underground mining,and a large number of people are threatened by coal dust,noise,radiation and other related occupational risk factors.One of the most common and major occupational health hazards is respiratory disease caused by coal mine dust.The relevant pathogenic mechanism remains to be further explored,so the continuous research on coal dust itself is still worthy of attention.Scanning electron microscopy has great advantages in the observation of fine particulate matter,and its own energy spectrum analysis system can scan and analyze the element composition of the observation object,which is very convenient and time-saving.However,there is no standard method for the determination of coal dust by scanning electron microscopy in China at present,and few studies have applied this technology to the observation of coal dust particles.Through a series of horizontal comparison and data analysis,we will select the most practical and efficient operation method to preliminarily explore the observation method of coal dust particles by scanning electron microscopy,so as to standardize the sampling,sampling,observation and measurement of coal dust as much as possible.It provides convenience and reliable reference for updating the occupational environment status of coal mine in time so as to take corresponding measures and make reasonable adjustment.Methods: In this study,from 16 subordinate coal mines of a mining group in Huaibei,Anhui Province,5 subordinate coal mines were randomly selected for on-site coal dust collection according to geographical location distribution and mine construction time,and a total of 60 dust samples were collected.The coal dust sample of No.1 mine is used to explore and form a complete observation method: firstly,the determination of sample preparation method and laying method,horizontal comparison of various methods of sample preparation and laying method,comparison of imaging effect,select the best;Secondly,the method of photographing particle samples is specified,and the sample size of a single sample is determined.Then a parameter measurement;The Image J software is used to process the pictures taken by the particle electron microscope,complete the measurement of particle morphology parameters,specify practical measurement and operation methods,and obtain the data of particle circumference,area,longest diameter,shortest diameter,etc.,which are then brought into the relevant formula for calculation,and comparative analysis is carried out according to the sample collection location and dust type.The morphology of particles is described objectively.Finally,energy spectrum analysis software attached to scanning electron microscopy was used to conduct energy spectrum spot scanning and surface scanning of sample particles,and a semi-quantitative report of element composition was obtained for subsequent analysis.Then the observation method proposed in this study is applied to the coal dust observation of No.2 ～ No.5 mine to verify the operability and practicability of the method.Results:1.Comparison of coal dust particle shape type distribution differences.By using this method to observe coal dust samples from 5 different coal mines,it can be found that in the same coal mine,different types of coal dust particles are exposed to different types of job,the difference is statistically significant(P < 0.05).No matter what kind of job or coal dust type,the proportion of flat and sharp coal dust is significantly higher than that of round and blunt coal dust,and the difference is statistically significant(P < 0.05).The distribution difference of coal dust particle shape type among different mines also has statistical significance(P < 0.05).2.Comparison of particle size distribution differences of coal dust particles in the same coal mine.In the same coal mine,the particle size distribution of coal dust exposed to different types of work is different,and the difference is statistically significant(P < 0.05).In No.1mine,coal dust particles are contacted by hewers and heading men are more concentrated in the range of 2 < d ≤ 5 μm,the coal dust particles contacted by auxiliary workers are relatively dispersed in the range of d ≤ 5 μm;In No.2 mine,coal dust particles contacted by auxiliary workers are more concentrated in the range of 2 < d ≤ 5 μm,the coal dust particles are contacted by hewers are more distributed in the particle size range of d ≤ 2μm and d > 10 μm;In No.3 mine,coal dust particles contacted by hewers and heading men are relatively dispersed in the range of d > 2 μm,coal dust particles are contacted by auxiliary workers are concentrated in the range of 2 < d ≤ 5 μm;In No.4 mine,coal dust particles are contacted by hewers and auxiliary workers are more concentrated in the range of 2 < d ≤ 5 μm,coal dust particles are contacted by heading men are relatively dispersed in the range of d > 2 μm;In No.5 mine,it can be seen that the coal dust particles contacted by hewers are relatively dispersed in the range of d > 2 μm,coal dust particles contacted by heading men and auxiliary workers are concentrated in the range of 2 < d ≤ 5 μm.3.Comparison of coal dust particle size distribution differences among different coal mines.For hewers and auxiliary workers,the differences of coal dust particle size distribution among the five mines were statistically significant(P < 0.05),in the particle size distribution of coal dust exposed to heading men,the difference among No.1,3 and 4mines was not statistically significant(P < 0.05),no statistical significance was found between No.2 and No.5 mines(P < 0.05),the difference between No.2 and No.1,3 and4 mines was statistically significant(P < 0.05),the difference between No.5 mine and No.1,No.3 and No.4 mine was also statistically significant(P < 0.05).4.Comparison of the proportion difference of some elements in coal dust particles.In the same coal mine,the proportion of some elements in coal dust particles exposed to different types of work is different,and the difference is statistically significant(P <0.05).The proportion of C element content in coal dust contacted by auxiliary workers in No.1 mine is significantly lower than that of hewers and heading men,and the difference is statistically significant(P < 0.05);In No.2 mine,the proportion of Si element content in the contact coal dust of heading men is significantly higher than that of hewers and auxiliary workers,and the difference is statistically significant(P < 0.05);The proportion of Si element content in coal dust particles contacted by hewers in No.3 mine is significantly higher than that of heading men and auxiliary workers,and the difference is statistically significant(P < 0.05);In No.4 mine,the proportion of Si element content exposed to coal dust in heading men is significantly lower than that in hewers and auxiliary workers,and the difference is statistically significant(P < 0.05);Only the proportion of Al element content in No.5 mine is different among different types of work,and the content of heading men is significantly higher than that of hewers and auxiliary workers,and the difference is statistically significant(P < 0.05).Conclusion: 1.This study preliminarily explored the characterization and analysis method of coal mine dust using scanning electron microscopy,which is highly operable and practical.2.The observation method proposed in this study can be used to find the differences in particle shape type distribution and particle size distribution of coal dust in different working areas of the same mine;The particle shape and type distribution of fixed point exhume and total dust also have obvious difference among different mines.3.The particle size of coal dust exposed to auxiliary workers is actually the smallest among the three types of work,so more attention should be paid to dust prevention and control in the working area of this type of work,and relevant measures should be strengthened.4.Coal dust particles in different work areas have obvious differences in the proportion of chemical element composition.Dust removal and personal protection can be carried out according to the distribution characteristics of coal dust,so as to achieve better dust removal effect. |
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