Molecular structure evolution characteristics of coals in Ningxia Hui Autonomous Region
With the typical coal samples taken as the research objects from different mining areas of Ningdong,Helanshan,Ningnan and Xiangshan in Ningxia Hui Autonomous Region,the coal structure was characterized by X-ray diffraction,Raman spectroscopy and Fourier transform infrared spectrosco-py,and the coal structure parameters and variation rules were obtained by peak fitting.The results show that the optical properties of low-medium rank coal are isotropic,the aromatic layer size is small,and the orientation is arbitrary.With the increase of coal rank,thed002value of aromatic layer spacing de-creases at the fastest rate,and the ductility La increases rapidly.When Rmax is greater than 2.0％,the change of d002 value slows down,which corresponds to the increase of stacking degree Lc value.At d002＜0.348 0 nm,the Raman parameters ID1/IG and AD1/AD1+G began to decrease linearly,the size of aro-matic lamellae in the molecular structure of coal increased,the orientation increased,the optical proper-ties showed anisotropy in the direction of parallel and perpendicular to the aromatic lamellae,and the degree of structural ordering increased.With the increase of coalification degree,the infrared spectrum shows that the fat structure content is low,the aromatic structure absorption band is significant,the aro-maticity parameter increases rapidly,the aliphatic hydrocarbon side chain falls off rapidly,and the hy-drocarbon generation potential parameter'A'becomes smaller.The coal of Helanshan coalfield and Xiangshan coalfield is superimposed by magmatic heat,and the metamorphic temperature is higher,which leads to the enhancement of aromatic ring condensation and the increase of aromatic hydrocar-bons.The research results provide certain guidance for the structural evolution of coal and the clean and efficient utilization of coal.
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