Study On The Content,Distribution And Occurrence Form Of Mercury In Shanxi Formation Coal Of Huainan Coalfield

Huainan Coalfield is an significant coal base in East China.With a large number of mining,it has entered the mining stage of 1 coal seam of Shanxi Formation.Mercury is a highly toxic element that occurs mainly in organic and inorganic forms in coal.Due to its characteristics of long-distance migration and strong redox capacity,it is easy to take place migration,transformation and redistribution in the process of coal processing and utilization,which will have an impact on the environment and human health.The early Permian shanxi coal group was taken as the research object in huainan.using XRD,XRF,SEM-EDS and ICP-MS,optical microscope,automatic sulfur measurement instrument,industrial analyzer and Sequential extraction experiments method and means,combination of stratigraphy,sedimentology,mineralogy,element geochemistry of rocks and other related knowledge analyse huainan coal of shanxi formation of physical and chemical properties,depositional environment characteristics,the mercury distribution in coal occurrence and enrichment characteristics and the release of mercury in coal combustion mechanism.The main research results show:(1)The depth coal of Shanxi Formation in Huainan belongs to the coal of medium and high volatile content,ultra-low ash,ultra-low total moisture and low-sulfur.According to the comprehensive analysis of oxides of major elements,XRD and microscopic observation,the minerals in the coal in the study area are mainly kaolinite,quartz,calcite and pyrite.The clay mineral kaolinite is filled in the cell cavity of the organic microscopic composition,and some very fine quartz particles were found,mainly in random groups,filling among the crystals of other minerals.Pyrite is mainly nodular,spherical and fissure filling.Based on the sedimentological characteristics,the Al₂O₃/TiO₂ratio is generally greater than 8,indicating that the sedimentary rocks in the study area are mainly intermediate-acid bedrok.The grey component index C value ranges from 0.10 to 1.68,indicating that the depositional facies is ocean-continental interdeposition in the study area.(2)The average mercury content of coal is 0.21?g/g in the study area.Compared with the mercury content in the crust,the enrichment coefficient EF of mercury in Shanxi Formation coal seam is 2.6,indicating enrichment.The mercury content in Zhangji coal mine is between 0.11?0.78?g/g,and that in Xinjier coal mine is between 0.03?0.93?g/g.The distribution of mercury content in coal is obviously different between the same coal seam and different coal mines,which is mainly affected by geological activities in depositional environment.The data fitting of mercury in coal and sedimentological characteristics is carried out by using the principle of data statistics.The results show that the mercury in coal of Zhangji coal mine is mainly affected by the depositional environment conditions such as redox environment,palaeosalinity and palaeoclimate.The upper coal seam of Xinjier Coal mine is influenced by geological activities dominated by seawater intrusion,while the lower coal seam is influenced by geological activities dominated by land debris input.(3)The occurrence form of mercury in coal is studied synthetically by chemical extraction experiment,correlation analysis and mineral analysis.The results show that mercury in the coal in the study area exists in pyrite in the form of sulfide binding.Among them,the mercury in Zhangji coal mine exists in the form of solid solution in pyrite,while the mercury in Xinjier coal mine is dispersed in the pyrite filled with cracks.(4)The dynamic release behavior of mercury in coal was simulated by combustion test.The results show that the mercury in coal begins to release at about 150?,the organic form of mercury in the coal begins to release at 200?300?,the sulfide form of mercury in the coal begins to release at 500?600?,and the mercury in the coal is almost completely released at about 750?in the combustion process.The release behavior of mercury in coal was observed by changing combustion conditions.As the heating rate increases,mercury in coal presents a positive correlation with it at low temperature,and a negative correlation with it at high temperature.At the same time,the air is reaction atmosphere that can promote the release of mercury in coal.