| Objective:This survey sampled coal dusts from different coal qualities in some of the main coal producing areas of China.The pyrophosphoric acid method was used to analyze the content of free silica in coal dust samples.To investigate the distribution of free silica content in coal dusts.In the process of detected the free silica content in coal dust by pyrophosphoric acid method,the operation process of the existing standard method was improved.The preparation of the standard material for the free silica content of coal dust in the future was prepared by means of data collection.Methods:Information Collection:Data of the reserves and regional distribution of coal resources in China,the coal quality classification standard in China,the characteristics of coal-bearing strata in China and the distribution of coal accumulating period,etc.The current research on the distribution of free silica in coal dust in China;The research progress and influencing factors of the determination of free silica in dust by pyrophosphoric acid method;And the basic theory of RM development.The Sample Collection:In this survey we collected coal dust samples from 48 different coal mines in Beijing,Shanxi,Chongqing,Shaanxi and Xinjiang.There are 3 in Beijing,9 in Shanxi,6 in Chongqing,25 in Shaanxi and 1 in Xinjiang.The selected areas include 100 billion tons of coal reserves,10 billion tons and less than 10 billion tons.The coal-bearing strata include the north,northwest and southwest regions of China's main coal-bearing regions.The period of coalescence(also known as coal age)includes the major coalescence periods such as Cambrian,carboniferous,Permian,Triassic,Jurassic and tertiary.The types of coal include anthracite,bituminous coal and lignite.Data Collection:The survey collected 46 data of free silica content in some coal mines from three regions of Xinjiang,Qinghai and Inner Mongolia.The data is provided by the local health administration,and the detection method of free silica content is pyrophosphoric acid.Experimental Analysis:In this survey we analyzed the content of free silica in coal dust samples by pyrophosphoric acid method.Each coal dust sample was measured three times and the results were averaged.In the present standard method,the coal dust samples were first incinerated in the porcelain crucible,then transfer in to the conical flask for pyrophosphate digesting.This step was improved to be incinerated and digested both in a conical flask that made of refractory glass,thus we skip the step that transfer the samples between the porcelain crucible and the conical flask.This improvement reduces the likelihood of errors due to improper operation.Statistical Analysis:The results of survey and experiment were analyzed with variance analysis.SPSS 20.0 statistical software was used for analysis.Results:In this survey,we collected coal dust samples in 48 coal mines from Beijing,Shanxi,Chongqing,Shannxi,Xinjiang,the samples collected in coal mining area,coal quality includes three kinds of coal quality anthracite,bituminous coal and lignite.The content of free silica in coal dust samples was detected by pyrophosphoric acid method,and dust samples with known free silica content were used as the quality control samples.The Experimental Results:The content of free silica in coal dust samples was determined by pyrophosphoric acid method.The results showed:The coal quality of three coal mines in Beijing is anthracite,and the content of free silica is 4.15%?9.49%.The content of free silica in a bituminous coal mine in Xinjiang autonomous region is 1.43%.The coal quality of 6 coal mines in Chongqing is bituminous coal,and the content of free silica content of coal dust is 2.01%?6.73%,three coal mines are anthracite,and coal dust free silica content is 1.45%?3.07%,one coal mine is lignite and the content of free silica is 4.33%.All nine coal mines in Shanxi Province are bituminous coal,and the content of free silica in coal dust is 3.30%11.04%.All 25 coal mines in Shaanxi province are bituminous coal,and the content of free silica is 4.17%?25.98%.The Data Collection Results:The coal in the three coal mines in Xinjiang is bituminous coal,the content of free silica in coal dust is 1.00%?6.37%.The data of free silica content of 10 coal mines were collected in Qinghai province,the lignite content of free silica in coal dust is 3.80%?5.40%,bituminous coal is 4.00%?7.50%,anthracite is 6.10?9.50%.Data on free silica content of 33 coal mines were collected in Inner Mongolia region,lignite is 4.02%?6.11%,bituminous coal is 2.10%?8.18%.Statistical Analysis Results:In the survey area,coal and source of data on the impact of coal dust free silica content is significant(F = 4.62,P<0.0001),the difference mainly comes from areas(F = 6.35,P<0.0001),the factors and no interaction effect between grouping factors.Conclusion:The results show that the content of free silica in coal dust between different regions is significant.Different types of sedimentary strata in different regions have different sedimentary types and different lithologic compositions.The difference of free silica content in coal dust should be mainly affected by coal bearing strata.After statistical analysis of the results of this survey,it was found that the difference of free silica content between different coal qualities was not significant after exclusion of regional factors.This may be related to Chinese coal classification standards,China's main coal classification to dry ash-free basis in coal volatile into the classification index,and cooperate with the light transmittance and bond index,etc.,does not take into account the free silica content in coal.There should be no regularity between the content of free silica and the degree of coalification between different coal.In pyrophosphate method with the current standard method,coal samples with porcelain crucible incinerate first and then pour into the conical flask process improvement for directly with high temperature resistant glass conical flask directly after incinerate digestion,the experimental results show that the quality control sample this for coal dust samples of pyrophosphate method improvement is successful.In the development of standard coal dust of pyrophosphoric acid,it is suggested that coal reserves,coal bearing strata,sedimentary methods and lithology components should be taken into consideration in the selection of coal quality.Coal dust for naturally occurring solid particulate matter,in the standard material development requirements,the uniformity and stability for partial shipments when sample request can relax appropriately,with pyrophosphate in coal dust dispersion and legal value of the work should be measured more,increase the setting value of sample size. |
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