Occurrence And Origin Of Harmful Trace Elements In High-sulfur Coal From Hanxing Coalfield

Distribution,occurrence,and origin of harmful traceelements in coal have always been the hot topics in coal geology.On the theoretical basis of coalfield geology,mineralogy and geochemistry,this thesis comprehensively applies many analysis and test methods,such as industrial analysis,optical microscope observation,electron probe with energy spectrum,X-ray diffraction,X-ray fluorescence spectrometer（XRF）,inductively coupled plasma mass spectrometer（ICP-MS）,etc.By comprehensively utilizing theoretical knowledge of Mineralogy and element geochemistry,the mineralogical characteristics,distribution and occurrence characteristics of harmful trace elements in No.9 coal of Yunjialing Coal Mine,Han Xing Coalfield are studied,the formation mechanism of sulfide minerals（pyrite,chalcopyrite and chalcopyrite）in coal is discussed in detail,and the source of harmful elements in coal is analyzed.The result shows that No.9 coal of Yunjialing Coal Mine is anthracite with low-ash,extra-low moisture,high sulfur and extra-low volatility.The main minerals in No.9 coal are illite,albite,calcite and pyrite,along with some trace minerals chalcopyrite,chalcopyrite,anatase,iron dolomite and apatite.Sulfide minerals in No.9 coal of Yunjialing Coal Mine are mainly pyrite and chalcopyrite.The microscopic occurrence forms of pyrite include massive,vein and fissure filling.Chalcopyrite usually occurs together with chalcopyrite,which is ring-banded encapsulated massive chalcopyrite.Sometimes both occur on the surface of massive pyrite or iron dolomite as speckles with obvious metasomatism.Block pyrite in coal is mainly formed at early diagenetic stage and vein and fissure filling are of metahydrothermal origin.Ring-banded chalcopyrite and chalcopyrite are of metahydrothermal origin.Harmful trace elements（Co,Cu,As,Se,Mo）in coal mainly occur in sulfide minerals and Ba mainly occurs in illite.Compared with the average value of Chinese coal,the contents of K₂O and Na₂O in No.9 coal of Yunjialing Coal Mine are higher,which are 4.32 times and 3.54 times of the average value of Chinese coal respectively.The content of Si O₂（7.66%）,Al₂O₃（5.26%）,Ca O（1.43%）,P₂O₅（0.08）,Mn O（0.03%）and Mg O（0.25%）were at average level.The content of Fe₂O₃（2.35%）and Ti O₂（0.12%）is significantly lower than that of Chinese coal.The contents of harmful trace elements Cu,As and Se in coal are enriched,which are 26.9,2.3 and 2.6 times of the world average value of coal respectively.Especially Cu is enriched abnormally,the copper content in single coal seam（YJL9-4c）is as high as1095μg/g.Harmful trace amounts（Co,Cu,As,Se,Mo and Ba）in coal are mainly controlled by three factors:terrigenous input,seawater influence and hydrothermal activity.