Geochemistry of sulfur and elements in coals from the Antaibao surface mine, Pingshuo, Shanxi Province, China

Abstract

Coal-bearing strata in the Antaibao surface mine, Pingshuo mining district Shanxi, China occur in the Taiyuan Formation (Upper Carboniferous) and Shanxi Formation (Lower Permian). The most productive coal seams in the mine are the Nos. 11, 9 and 4. Twenty-five samples of coals, partings, and roof shales from the Nos. 11, 10, 9, 5 (Taiyuan Formation), and 4 (Shanxi Formation) seams in the Antaibao mine were analyzed for ash, and total sulfur contents and forms of sulfur. The No. 11 seam is a medium- to high-sulfur coal (1.3–3.1% S). A coal sample (14.1% ash) from the No. 10 seam contains 3.4%, and high ash coal (37.4% ash) from the same seam contains only 0.4% total sulfur. The No. 9 seam is a low- to medium-sulfur coal (0.6–1.3% S). The highest sulfur content among the samples is 5.8% total sulfur from a coal sample of the No. 5 seam. The No. 4 seam is low-sulfur coal (0.29–0.54% S). The remarkable variation in sulfur content among the coal seams in the Taiyuan and Shanxi Formations could reflect different depositional environments; from coastal to lower deltaic plain for the Taiyuan, and from upper deltaic plain to fluvial basin for the Shanxi Formation. The sulfate sulfur comes mainly from the oxidation of pyrite. Sixteen samples were analyzed for 26 major, minor and trace elements by X-ray fluorescence spectrometry. The Sr content is significantly higher in coals from the No. 4 seam in the Shanxi Formation than those from Nos. 11 to 5 seams. Chlorine, Sr, Ca and P are elements bound organically; while Si, Al, Ti, Fe, K, Na, Mg, Cr, V, Ni, Rb, Ba and Nb are mainly associated with minerals.