Petrographical and geochemical characterization of the inertinite-rich coal from the Ningdong Coalfield, Northwest Ordos
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ORIGINAL PAPER
Petrographical and geochemical characterization of the inertinite-rich coal from the Ningdong Coalfield, Northwest Ordos Basin, China Fangpeng Du 1,2 & Shuzheng Ning 3 & Chiyang Liu 2 & Congcong Li 1 & Junwei Qiao 1 & Furong Tan 1 & Zheng Luo 1 Received: 9 August 2018 / Accepted: 14 December 2018 # Saudi Society for Geosciences 2019
Abstract This study deals with the coal petrographical and geochemical characteristics of the #2 and #6 coal seams in the Ningdong Coalfield, Northwest Ordos Basin. Proximate analysis, sulfur forms, ash composition, trace element contents along with macral analysis, and X-ray diffraction were performed on the coal samples. The Ningdong coal was deposited in a large continental (freshwater) basin, which resulted in very low ash yield and total sulfur contents (7.63 and 0.35% on average, respectively), with organic sulfur being the dominant sulfur form. The average random vitrinite reflectance of #2 and #6 seams are 0.49 and 0.60%, respectively, indicating a low metamorphic grade. Inertinite is the most abundant group in the Ningdong coal (50.1% on average), whereas, the vitrinite and liptinite contents are 44.2 and 2.4%, on average, respectively. SiO2 is the major coal ash component (35.57%), whereas, the Al2O3, CaO, and Fe2O3 contents also exceed 10% of the crystalline phases. Trace element contents are low in general; a lot of them are less than the respective World hard coal values. At the same time, the contents of Sc, Cr, Mn, Cu, Y, La, Tl, Pb, Th, U, Cs, Yb, and Hf are close to the average values of the World hard coal, with Mn and Sr even slightly enriched in the #6 and #2 seam, respectively. Analysis shows that Si, Al, K, Ti, Li, Cr, Nb, Pb, Th, Cd, In, Hf, and Ta are mainly hosted in the exogenous minerals and Ca, Mg, and Na mainly come from the endogenous minerals. The flat and wide basin structure along with the paleomire supply with fresh water are the major reasons of the special petrographical and geochemical feature of the Ningdong coal. Keywords Inertinite-rich coal . Petrographic . Geochemistry . Ningdong Coalfield . Jurassic
Introduction Coal mining and utilization is one of the major environmental pollution sources because the coal’s chemical composition is complex and sometimes contains potential toxic elements and organic compounds (Huang et al. 1999; Finkelman 2004; Zhao et al. 2008; Dai et al. 2012; Wang et al. 2016; Kim et al. 2017; Vaseem et al. 2017; Zhao and Luo 2017; Li
* Fangpeng Du [email protected] 1
Aerophoto Grammetry & Remote Sensing Bureau, China National Administration of Coal Geology, Xi’an 710199, China
2
State Key Laboratory for Continental Dynamics/Department of Geology, Northwest University, Xi’an 710069, China
3
China National Administration of Coal Geology, Beijing 100038, China
et al. 2018a, b). However, coal still dominates the energy supply in many developing countries, including China, and the dilemma between further exploitation and pollution will last for decades (Dai and Finkelman 2018). Clean and efficient use of
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