Environmental Geochemistry And Cleanliness Grade Evaluation Of Typical Hazardous Elements At Huainan Coalfield

Huainan coalfield is rich in coal resources.The hazardous elements in coal are released during coal burning.The hazardous elements produced can accumulate in biological,soil and atmospheric environment,posing a great threat to human health.Therefore,it is of great theoretical and practical significance to carry out environmental geochemistry and clean grade evaluation of hazardous elements in coal,which meets the practical needs of green development and clean and efficient utilization of coal.On the basis of sufficient domestic and foreign literature research and large data analysis of typical hazardous elements in coal from Huainan coalfield,this paper took the main coal seam(13-1 coal,11-2 coal,8 coal,6 coal,4 coal and 1 coal)of Huainan coalfield as the research object and the fixed bed simulation combustion experiment was adopted.Combined with Inductively Coupled Plasma Mass Spectrometry(ICP-MS),Atomic Fluorescence Spectrometry(AFS),X-Ray Diffraction(XRD),X-Ray Fluorescence spectrometry(XRF),Scanning Electron Microscope-Energy Dispersive Spectrometer(SEM-EDS)and Thermogravimetric Analysis(TG),the content,distribution rule,symbiotic combination,modes of occurrence,combustion characteristics and environmental effects of typical hazardous elements in Huainan coalfield were systematically studied.The cleanliness levels of main coal seams in Huainan coalfield were divided,and the following results are obtained:(1)Based on the large data analysis of typical hazardous elements in the main coalbed of Huainan coalfield in the past,the average content and range of typical hazardous elements in Huainan coalfield(3709 samples)were proposed,of which Cr,Mn and Ni elements were relatively high in Huainan coalfield,with the average values of 37.46?g/g,50.03?g/g and 23.67?g/g respectively;Compared with the world coal,the enrichment coefficients of Se and Hg elements were more than 4,which were "high content level",while the other typical hazardous elements were all at "normal content level".Through systematic analysis of the plane distribution characteristics of hazardous elements in coal,it was found that the high-value areas of As and Se elements in coal were mainly located in the west of coal field,the high-value areas of Hg elements were located in the east of coal field,and the other typical hazardous elements(Cr,Mn,Co,Ni,Cd,Sb and Pb)were all relatively high in Panji area of Huainan(especially near Pansan coal mine),which may be related to magmatic intrusion phenomenon in Pansan coal mine.(2)Cluster analysis,correlation analysis and stepwise chemical extraction experiments were used to study the symbiotic combination characteristics and modes of occurrence of typical hazardous elements in coal.It was concluded that except for As element,the other typical hazardous elements mostly showed inorganic affinity.Compared with Se and Hg elements,the modes of occurrence of As element was more significantly affected by different coal-forming environments.The presence of organic arsenic in coal may be closely related to the low metamorphic degree,low ash content and low arsenic content of coal.(3)Through fixed bed simulation combustion experiments at different temperature points and different combustion rates,combined with inductively coupled plAsma mass spectrometry,atomic fluorescence spectrometry and thermogravimetric analysis,a classification method for the volatility of typical hazardous elements in coal was proposed,the influencing factors of volatility of typical hazardous elements in coal were clarified,the maximum weightlessness temperature(TP)can be used as a coal quality index to reflect the influence of different heating rates on volatility of typical hazardous elements in coal,and the potential environmental impact of As,Se,Hg,Cd,Sb,Pb,Cr and Ni elements in Huainan coalfield coal was pointed out.(4)By using the generalized contrast weighted scaling index method,an evaluation index system suitable for Huainan coalfield was established.By systematically evaluating the cleanliness levels and regional distribution of main mines and main coal seams in Huainan coalfield,it was concluded that the cleanliness levels of coal resources in Huainan coalfield were mainly good-medium clean coal,and some areas were poor clean coal,in which the element of Cr content in poor clean coal often exceeded the maximum concentration limit,and there may be a certain degree of pollution during combustion.However,Se,As,Hg and Pb elements were close to or exceed the maximum concentration limit in some coal seams,which required special attention.