Coal Geochemical Characteristics Of Nangou Coal Mine In Xuangang Mining Area, Shanxi Province

This paper takes the main coal seam of Nangou Coal Mine in Ningwu Coalfield Xuangang Mining Area as the research object.The content characteristics,occurrence state and enrichment mechanism of elements in coal were discussed.Polarizing microscope was used to observe the coal maceral;X-ray fluorescence spectroscopy?XRF?was used to determine the content of major elements in coal and gangue;X-ray diffraction?XRD?was used to analyze mineral composition in coal;Scanning electron microscopy and spectroscopy?SEM-EDX?was used to observe the morphological characteristics of minerals;the content of trace elements in coal and gangue was determined by Inductively coupled plasma mass spectrometry?ICP-MS?;and the occurrence of trace elements in coal was determined by step-by-step chemical extraction?SCEP?.Coal maceral analysis shows that the coal maceral are mainly vitrinite,and the degree of gelation is relatively high.The coal seam is formed in the environment of high reducibility.The analysis of coal facies indicates that 2^#_PP and 5_PP^#coal in Nangou coal mine are formed in low peat moor.The minerals in 2^#_PP and 5^#_PP coal are mainly clay minerals and calcite.The clay mineral is mainly kaolinite,which is derived from terrigenous detrital matter.Calcite is a metaplastic mineral formed by precipitation in circulating water of cracks or voids in coal.Under the scanning electron microscope,5^#_PP coal showed that the minerals such as pyrite,quartz,rutile and zircon were distributed in a small amount.Li,Cu,Ga,In and Hf in 2^#_PP coal of Shanxi Group are slightly enriched,Zr and Nb are enriched;Li,Ga,Sr and Zr are enriched in 5^#_PP coal of Taiyuan Group.Rare earth element distribution patterns and La/Yb-?REE graphical were used to analyze the provenance.The trace element provenance may be the granite and sedimentary rocks of the northern Yinshan paleo-land.Correlation analysis shows that some trace elements in 2^#_PP and 5^#_PP coals were positively correlated with ash,indicating that some trace elements were mainly present in inorganic minerals.Some trace elements were not significantly correlated or negatively correlated with ash,indicating trace elements are also present in organic matter.The Tessier five-state method was used to extract the trace elements and rare earth elements in coal,and the content of the elements in each state was determined by ICP-MS.The results show that most of the trace elements are mainly in the inorganic minerals with kaolinite as the main mineral,followed by the organic state,and the exchangeable ionic state in Cu,Mo and Sb accounts for a large proportion.The Mn element is mainly iron-manganese oxide state,and the iron-manganese oxide state of Sc,Sr and Pb elements also accounts for a large proportion.The carbonates in each element accounted for the least proportion,while the carbonate minerals in Nangou 2^#_PP and 5^#_PP coal are mainly calcite,so calcite plays a role of dilution in the enrichment and concentration of trace elements.Stepwise chemical extraction of the rare earth elements shows that the state of the rare earth elements in coal is dominated by aluminosilicate bound state?74%?and organically bound state?18%?.The enrichment of the rare earth elements in Taiyuan coal is also related to pyrite.Compared with medium and heavy rare earth elements,the proportion of light rare earth elements in residual state is higher and that of organic state is lower.