Concentrations and modes of occurrence of some potentially valuable and toxic elements in the No. 5 coal from the Yanzishan Mine, Datong Coalfield, Shanxi Province, China

Yue Yuan,Songhang Zhang,Shuheng Tang

doi:10.1177/0144598719861272

Yue Yuan, Songhang Zhang + Show 1 more

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https://doi.org/10.1177/0144598719861272

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Abstract

In this study, the mineralogical compositions, concentrations and occurrence modes of the elements in the No.5 coal from the Yanzishan Mine were investigated, using X-ray powder diffraction (XRD), X-ray fluorescence spectrometry (XRF), inductively coupled plasma mass spectrometry (ICP-MS), and scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer (SEM-EDS). The No. 5 coal is characterized by high ash yield content (mean 32.30%) and low sulfur content (mean 0.47%). The minerals are mainly composed of kaolinite, quartz and pyrite, with a small proportion of illite, apatite, siderite, sphalerite and Ti-oxide. Compared with the Chinese coals, the No. 5 coal has much higher percentages of SiO2 (mean 16.22%) and Al2O3 (mean 14.57%) than other major oxides. Compared with the world hard coals and Chinese coals, the No. 5 coal is enriched in some potentially valuable (Al2O3, Li, Ge, Zr, and Hf) and toxic (Be, As, Se, Cd, and Pb) elements. Lithium and Hf are mainly associated with clay minerals; Be, Se, and Zr mainly have both inorganically and organically affinities; As mainly occurs as a sulfide form in pyrite; Cd is incorporated in clay minerals; and Pb has an affinity for both clay minerals and organic sulfur. All the coal samples are characterized by weakly positive or no pronounced Eu anomalies, indicating that the rare earth elements and yttrium (REY) likewise originated from granite of the Yinshan Oldland together with injection of the low temperature hydrothermal fluids.

Highlights

Coal has played and still plays a leading role as primary energy source in China
The No 5 coal is characterized by high ash yield content based on the Chinese Standards GB/T 15224.1–2010) (2011) and low sulfur content based on the Chinese Standards GB/T 15224.2–2010) (2011)
This study indicates that Cd is predominately associated with clay minerals, because of positive correlation coefficients with ash yield (r 1⁄4 0.79), Al2O3 (r 1⁄4 0.74), and SiO2 (r 1⁄4 0.78) (Figures 9(f) and (g))

Summary

Introduction

Coal has played and still plays a leading role as primary energy source in China. As the “Statistical Review of World Energy (2017)” mentioned (B., 2017), coal consumption decreased from 64% in 2015 to 62% in 2016, China is still the largest consumer of coal, accounting for 23% of the world’s annual coal consumption. Group 1 exhibits a high positive correlation coefficient with ash yield (0.7–1, including MgO, SiO2, Al2O3, TiO2, F, Sn, Cd, Ba, and U), indicating inorganic affinity.

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