Geochemistry Characteristics Of Spontaneous Combusted Gangue In The Duerping Coal Mine,Xishan Coalfield

Coal gangue a kind of solid waste which is produced in the process of coal mining,and these coal gangue piled up in the coal mining area forming a mountain.The spontaneous combustion of coal gangue piles is a sign of mining pollution,so the study of spontaneous combustion gangue is urgently needed.This article based on the Duerping coal mine in Xishan coalfield,several methods were taken,such as X-ray diffraction(XRD),Polarizing microscope,Scanning electron microscopy(SEM),XRF,HG-AFS,ES,ICP-MS,ICP-OES and other required equipment.The mineralogy characteristics of spontaneous combustion gangue was analysied,the geochemical characteristics of minor,trace and rare earth elements were measured,and the property change of coal gangue before and after spontaneous combustion.Here are some results:(1)Burning waste rock generally appears red and gray,and white salt and sulfur-bearing yellow substance on the surface,XRD spectrum showed the main minerals of unburned samples are quartz,kaolinite,and some clay minerals,and the main minerals of combustion samples are quartz and anhydrite;The samples microscopically observed by polarizing microscope showed unburned samples have minerals such as quartz,kaolinite,and illite,but quartz and montmorillonite are in the combusted samples.Unburned samples microscopically observed by SEM that proved there were quartz,pyrite,siderite,aluminum silicate,anatase,calcite,zircon,barite,witherite,plaster of paris,burning samples are quartz,kaolinite,calcium silicate,gypsum,gibbsite,etc.Before and after the beheavior of kaolinite samples showed that suffering from the high temperature of 500? above,the mineral species decreased,mineral structure was relatively single,given priority to with gypsum secondary minerals,suggest that the sample of acidic water eluviation.(2)Minor elements(C,N)associated with the organic matter of coal gangue,their content decreased significantly after combustion,while the phosphorus element hardly changed because it existed in phosphate.Chlorine decreased which was related to combustion and leaching.(3)The ratio of Sr/Ba and B/Ga suggest that DY1601-DY1605 belonged to continental fresh-water deposit,DY1606 and DY1607 were continental brackish water deposits,V/Cr(1.26-1.71),U/Th(0.20-0.44),Ni/Co(2.10-3.66),?U(0.75-0.93),(Cu+Mo)/Zn indicated that all the samples were in aerobic environment.Compared the above value of the sample with partings of 2#,3# and 8#coal seam indicated that coal gangue may come from Shanxi formation;Compared with UCC found that coal gangue enriched most poisonous and harmful elements in coal gangue,during combustion Cr,Ge,Sn,Pb,Bi and In reduced,Ni and zinc increased;Compared with China's coal,north China C-P coal and the United States coal found that Cu,zinc,Sr,Mo from deficit to enrichment during combustion,although some elements has enriched after burning,but their content has changed;During spontaneous combustion it found that the content of Be,Sc,Cs,In and Th almost no change,but V,Ni,Cu and zinc,Rb,Ba,Mo,Sb,Tl increased,Cr,Co,Ga,Ge,As,Se,U,Nb,Cd,Pb,Sn,Ta,W,Bi content decreased,poisonous and harmful elements Cr,As,Se,Cd,U and Pb content reduce.We suggested that the reduced elements may enter into the atmosphere,soil and water.(4)Due to weathering,burning and eluviation,the content of light rare earth elements of coal gangue increased,heavy rare earth elements content reduced,europium negative anomaly indicated that it suffered oxidation environment,according to cerium anomaly we can conclude that unburned samples were from the partings of 2#coal seam.The rare earth element in coal gangue chondrite standardized curves are skewed to the right,which has obvious europium negative anomaly,the results showed that their provenance is consistent,and originate from terrigenous clastic rock,LREE have a higher level of fractionation than that of HREE;The rare earth elements of waste rock after spontaneous combustion on the standardization of continental crust curves observed that light rare earth content increased,the content of Gd-Lu decreases,the distribution of the combustion sample pattern is consistent,besides DY1602 samples with europium negative anomaly,other samples have europium positive anomalies,and the europium positive anomaly of DY1605 is the most obvious.After combustion,the value of ?Ce increased,and the value of ?Ce of DY1602 was the maximum(?Ce=1.04),so we can indicate that oxidation affects the value of ?Ce.