中国科技论文在线 http://www.paper.edu.cn

Available online at www.sciencedirect.com

Journal of Geochemical Exploration 97 (2008) 59–68 www.elsevier.com/locate/jgeoexp

Composition and quality of coals in the Huaibei Coalfield, , ⁎ Liugen Zheng a,c, Guijian Liu a,b, , Lei Wang a, Chen-Lin Chou d

a CAS Key Laboratory of Crust–Mantle Materials and the Environments, School of Earth and Space Sciences, University of Science and Technology of China, 230026, PR China b State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, The Chinese Academy of Sciences, Xi’an 710075, Shannxi, PR China c Croucher Institute for Environmental Science and Department of Biology, Baptist University, Tong, Hong Kong SAR, PR China d Illinois State Geological Survey (Emeritus), Champaign, IL 61820, USA Received 28 June 2007; accepted 5 November 2007 Available online 21 November 2007

Abstract

The Huaibei Coalfield, Anhui Province, China, is one of the largest coalfields in China. The coals of Permian age are used mainly for power generation. Coal compositions and 47 trace elements of the No. 10 Coal of the Shanxi Formation, the No. 7, 5, and 4 Coals of the Lower Formation, and the No. 3 Coal of the Upper Shihezi Formation from the Huaibei Coalfield were studied. The results indicate that the Huaibei coals have low ash, moisture, and sulfur contents, but high volatile matter and calorific value. The ash yield increases stratigraphically upwards, but the volatile matter and total sulfur contents show a slight decrease from the lower to upper seams. Magmatic intrusion into the No. 5 Coal resulted in high ash, volatile matter, and calorific value, but low moisture value in the coal. Among the studied 47 trace elements, Ba, Co, Cr, Cu, Hg, Mo, Ni, Pb, Sb, Th, U, V, and Zn are of environmental concerns. Four elements Hg, Mo, Zn, and Sb are clearly enriched in the coals as compared with the upper continental crust. © 2007 Elsevier B.V. All rights reserved.

Keywords: Huaibei Coalfield; Coal compositions; Coal quality; Trace elements; Minerals

1. Introduction gas resources and abundant coal reserves (1000 billion Mt), coal has been and will continue to be relied upon as Coal is an important energy resource in the world. In a dominant primary energy source (Xu et al., 2000; Liu China, due to limited domestic petroleum and natural et al., 2004). Guan et al. (2006) predicted that coal will constitute about 55% of primary energy source in China in 2015, decreasing from the present 67%. The coal production in 2006 is 2.3 billion tons. With the use of a ⁎ – Corresponding author. CAS Key Laboratory of Crust Mantle huge amount of coal, the growing impact on the en- Materials and the Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, PR vironment and human health occurs during the course of China. coal exploitation, coal cleaning, transportation, and E-mail address: [email protected] (G. Liu). combustion (Zheng et al., 1999; Finkelman et al., 2002;

0375-6742/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.gexplo.2007.11.002 转载 中国科技论文在线 http://www.paper.edu.cn

60 L. Zheng et al. / Journal of Geochemical Exploration 97 (2008) 59–68

Dai and Ren, 2006; Liu et al., 2007a). In fact, some of data not only provide information about the behavior of these environmental problems could be reduced if coal coal during combustion, but also information about the quality information is available and adequate clean coal emissions of sulfur dioxide, carbon dioxide, nitrogen technologies are used. Therefore, information about the oxides, and hazardous trace elements (such as Hg, As, F characteristics of chemical properties, such as minerals and Se) into the atmosphere, which may result in en- and trace elements in coals, are urgently needed for vironmental problems, such as acid rain and global climate coal utilization in an environmentally acceptable change, and in human health problems (Finkelman and manner (Finkelman and Gross, 1999; Liu et al., 2003, Gross, 1999; Finkelman et al., 2002; Liu et al., 2007a, 2005a). 2007b; Zheng et al., 2006a, 2007a). In general, coal chemical properties include proximate The Huaibei Coalfield, located in Northern Anhui and ultimate analysis, calorific value, sulfur content, ash Province, is one of the major coalfields in China (Fig. 1). composition, and minor and trace element contents. These Some studies on trace elements (especially some potential

Fig. 1. Location of the Huaibei coalfield in Anhui Province, China. 中国科技论文在线 http://www.paper.edu.cn

L. Zheng et al. / Journal of Geochemical Exploration 97 (2008) 59–68 61 hazardous trace elements) in coals in the coalfield have are 23 active underground coal mines in the coalfield been reported (Zheng et al., 2005, 2006a, 2006b, 2007b, (Figs. 1 and 2). The coal reserves in the Huaibei Coalfield 2008a; Zhao et al., 2000; Liu et al., 2005b). However, up are abundant and the coal rank is mainly bituminous with to date, no systematic studies on ash yield, moisture, small amounts of anthracite and natural coke due to the volatile matter, sulfur, etc. in the Huaibei Coalfield were effect of magmatic intrusions. Annual production is over conducted. The aim of the present study is to investigate 30 Mt, which is mainly used by power plants and the chemical characteristics of the coals in the Huaibei industrial boilers. The Pennsylvanian and Permian age Coalfield and provide systematic information about coal coal-bearing sequences in the 1300 m in thickness quality for use in environmental protection. (Fig. 3). There are 13 to 46 coal seams in different mining areas, but only three to 12 seams are economically 2. Geological setting minable. The cumulative thickness of the minable coal seams varies from 1.5 m to 15 m. Coal seams in the The Huaibei Coalfield located in the northern Anhui Formation and the Formation (Pennsylvanian) Province is one of the major coalfields in China. There are thin and rarely mined. The economically minable

Fig. 2. Coal-mines in the Huaibei Coalfield, Anhui Province, China. 中国科技论文在线 http://www.paper.edu.cn

62 L. Zheng et al. / Journal of Geochemical Exploration 97 (2008) 59–68

Fig. 3. Stratigraphic column and lithological characteristics of coal-bearing sequence in the Huaibei Coalfield. seams are mainly in the Shanxi Formation and the Lower (Upper Pennsylvanian) consists of limestone, sandstone, Shihezi Formation (Permian). The coal seams in the mudstone, and coal. It contains three to eleven coal seams, Upper Shihezi Formation are only partially economically most of which are either not economically minable or only minable. The coal-bearing formations in the Huaibei locally minable. coalfield are briefly described below. The Shanxi Formation (Lower Permian) is 96 m to The Benxi Formation (Middle Pennsylvanian) ranges 143 m thick and is composed mainly of sandstone, fine- from 2 m to 22 m in thickness and is composed primarily grained sandstone, mudstone, and coal, with one or two of thin-bedded limestone, aluminous mudstone, ores, minable coal seams and a cumulative coal thickness of andcoal.The121mto150mthickTaiyuanFormation 1.9 m. 中国科技论文在线 http://www.paper.edu.cn

L. Zheng et al. / Journal of Geochemical Exploration 97 (2008) 59–68 63

Fig. 4. Samples collected from the No. 10, 7, 5, 4 and 3 Coals of Permian age in the Huaibei Coalfield.

The Lower Shihezi Formation (Lower Permian) is when they were collected to prevent contamination and 102 m to 151 m thick, and is primarily composed of minimize oxidation. sandstone, fine-grained sandstone, mudstone, aluminous The samples were collected from five coal seams, mudstone, and coals. It contains four to 20 coal seams, and which are No. 10, 7, and 3 Coals in the Mengzhuang Mine about half of these seams are minable with a cumulative and No. 5 and 4 Coals of the Zhuzhuang Mine (Fig. 4). coal thickness of 11.6 m. No. 7, 5, and 4 Coals occur in this The thickness of No. 10, 7, 5, 4, and 3 Coals at the formation. No. 7 and 5 Coals are locally influenced by sampling locations was 1.9, 1.2, 2.5, 2.8 and 1.5 m, magmatic intrusions in parts of the coalfield. respectively. Samples HB10-1 to HB10-8 were collected The Upper Shihezi Formation (Upper Permian) con- from the No. 10 Coal of the Shanxi Formation. Samples tains sandstone, fine-grained sandstone, and mudstone; the HB7-1 to HB7-2, HB5-1 to HB5-6, and HB4-1 to HB4-9 sandstones show various colors, including purple, yellow were collected from No. 7, 5, and 4 Coals of the Lower and green, in the upper part of the formation. The formation Shihezi Formation, respectively. Samples HB3-1 to HB3- contains five to thirteen coal seams, and only one coal seam 4 were collected from the No. 3 Coal of the Upper Shihezi (No. 3 Coal) has a minable thickness of 1.5 m. Formation (Fig. 3). The Shiqianfeng Formation (Upper Permian) is more than 1000 m thick and consists of red-brick-colored, fine- 3.2. Analytical methods grained sandstone and coarse-grained sandstone. No coal is present, but thin gypsum layers are found locally in this The bulk samples from the field were air-of 0.5 kg was formation. obtained. The samples for mineralogical, proximate, ultimate and chemical analyses were pulverized to less 3. Samples and methods than 200-mesh and dried for 12h in a desiccator. Proximate and ultimate analyses were performed following ASTM 3.1. Sample collection (1992) standard procedures at the Laboratory for Coal Chemical Analysis at the of Science and Twenty nine samples of coal were collected from two Technology, , Anhui, China (Table 1). underground mines (Mengzhuang Mine and Zhuzhuang The minerals in coals and ashes were determined by Mine) in the Huaibei Coalfield, Anhui Province (Figs. 2 X-ray diffraction (XRD, D/max-1200 from ) and and 4). Bench samples of uniform thickness were cut scanning electron microscopy (SEM). Trace elements downward along each seam so that the vertical variation (Ag, As, Au, Ba, Br, Cl, Co, Cr, Cs, Cu, Ga, Hf, I, In, of geochemical characteristics within these seams can be Mo, Rb, Sb, Sc, Sr, Ta, Th, U, V, W, Zn, La, Ce, Nd, Sm, studied. The samples were placed in plastic storage bags Eu, Tb, Dy, Yb, Lu) in the samples from No. 10, 7 and 3 中国科技论文在线 http://www.paper.edu.cn

64 L. Zheng et al. / Journal of Geochemical Exploration 97 (2008) 59–68

Table 1 Main parameters of coal quality of coals from the Huaibei Coalfield, Anhui Province, China

Coal seam A d% M ad% VM daf% St,d% P d% Q, ad (MJ/Kg) C daf% H af% N af% No. 3 (n=4) Range 10.08–15.63 2.03–3.17 36.07–40.76 0.22–0.81 0.002–0.016 26.0–30.1 81.8–83.9 5.12–6.11 1.43–1.63 Av. 13.60 2.56 38.32 0.48 0.019 27.9 83.0 5.49 1.52 Geo. 13.44 2.53 38.28 0.43 0.008 27.9 83.0 5.47 1.52 No. 4 (n=9) Range 8.75–24.98 1.89–2.44 36.89–41.24 0.23–0.85 0.004–0.021 26.4–30.2 64.8–81.1 1.17–3.72 1.94–3.52 Av. 13.23 2.08 38.98 0.51 0.010 28.7 73.4 2.83 2.89 Geo. 14.70 2.08 38.96 0.48 0.009 28.7 73.2 2.71 2.83 No. 5 (n=6) Range 15.01–18.35 1.68–2.06 34.32–39.43 0.46–0.88 0.009–0.032 29.8–34.2 72.0–76.0 3.22–3.83 2.66–3.64 Av. 16.44 1.92 36.07 0.64 0.020 32.1 73.6 3.51 3.11 Geo. 16.40 1.91 36.05 0.62 0.019 32.1 73.5 3.50 3.09 No. 7 (n=2) Range 12.53–12.88 1.91–1.94 36.28–38.93 0.44–0.74 0.002–0.004 28.0–29.4 81.5–83.8 5.22–5.72 1.53–1.76 Av. 12.71 1.93 37.61 0.59 0.003 28.7 82.7 5.47 1.65 Geo. 12.70 1.93 37.60 0.57 0.003 28.7 82.6 5.46 1.64 No. 10 (n=8) Range 1.51–23.14 1.53–2.68 39.72–47.20 0.32–1.74 0.003–0.120 24.3–31.2 79.0–83.7 4.78–7.40 1.43–1.73 Av. 12.05 1.86 42.47 0.96 0.026 28.05 82.2 5.79 1.59 Geo. 10.43 1.82 42.40 0.84 0.014 27.97 82.1 5.75 1.59 Huaibei Coals Range 1.51–24.98 1.53–3.17 34.32–47.20 0.22–1.74 0.002–0.120 24.3–34.2 64.8–83.9 1.17–7.40 1.43–3.64 Av. 13.46 2.10 38.78 0.66 0.017 29.1 77.8 4.34 2.30 Geo. 12.20 2.07 38.69 0.59 0.011 29.0 77.6 4.07 2.17 In the table: n–number of the samples; Av.–average value; Geo.–geometrical mean; A–ash yield; d–dry; M–moisture; ad–air-dried; VM–volatile

matter content; daf–on a dry and ash-free basis; St–total sulfur; P–phosphorus; Q–calorific value; %–wt.%.

Coals were determined by instrumental neutron activa- 1200 W for 25 min, and at 1200 W for 30 min). After tion analysis (INNA) at the China Atomic Energy cooling, the sample was diluted to 50mL with double- Research Institute in (Tables 2 and 3). distilled deionized water. The mercury content was Samples from No. 5 and 4 Coals were analyzed for determined using a flow injection mercury system trace elements (As, Ba, Co, Cr, Cu, Ga, Rb, Sc, Sr, Ta, (FIMS) on Perkin Elmer As90 at the Hong Kong Baptist Th, U, V, Zn, Ni, Ge, Y, Zr, Nb, Hf, Pb, La, Ce, Pr, Nd, University, Hong Kong, China (Table 3). Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) by inductively coupled-plasma mass spectrometry (ICP- 4. Results and discussion MS) on PE Elan 6000 from the U.S. and for major elements (Si, Al, Ca, Fe, K, Mg, Na, P, Mn, S, and Ti) by 4.1. Ash yield inductively coupled-plasma atomic-emission spectro- metry (ICP-AES) on Varian VISTA-PRO from the U.S. The ash yield is the amount of residue after the coal is at the Institute of Geochemistry, Chinese burned (Liu et al., 2003, 2005a). It is an important and Academy of Science in Guangzhou (Tables 2 and 3). routinely determined characteristic of coal quality. The Samples were digested using HNO3:HCl:HF (3:1:1) in a ash yield of samples from the Huaibei Coalfield is microwave oven, and the precision (relative standard between 1.51% and 25.0%, with an average of 13.5% and deviation) was ± 5%. a geometric mean of 12.2% (Table 1). The Permian coals For Hg determination, the coal sample (0.1 g) was in the Huaibei Coalfield are much lower in ash yield than treated with 12 mL of an oxidizing solution (HNO3:HCl = the Late Permian coals from Qianxi Fault Depression 3:1) and 3 mL hydrofluoric acid in a Telfon digestion Area in southwestern China (29.3%) (Zhang et al., 2004) vessel put in a microwave oven (at 600 W for 30 min, at and the Upper Permian coals from the Coalfield,

Table 2 Average ash composition of five coal seams in the Huaibei Coalfield, Anhui Province, China

Coal seam SiO2 Al2O3 CaO Fe2O3 K2O MgO Na2OP2O5 MnO2 SO3 TiO2 No. 3 51.51 33.07 6.34 4.56 1.60 0.839 0.529 0.078 0.037 1.14 1.95 No. 4 52.19 30.44 8.13 4.46 1.59 1.090 0.475 0.085 0.092 1.25 1.44 No. 5 52.59 36.24 2.55 4.31 2.50 1.037 0.516 0.101 0.012 1.68 2.14 No. 7 52.68 34.75 3.57 4.09 1.67 1.014 0.506 0.098 0.009 1.83 1.52 No. 10 48.48 29.24 7.57 7.33 0.9 1.994 0.606 0.524 0.037 2.09 1.33 中国科技论文在线 http://www.paper.edu.cn

L. Zheng et al. / Journal of Geochemical Exploration 97 (2008) 59–68 65

Table 3 Abundances of trace elements in coals from the Huaibei Coalfield, Anhui Province, China (in μg/g) Element Range Average Geometric Standard China U. S.➂ Upper continental EF No. of samples mean deviation crust➃ Ag 4.9–16.5 11.3 10.0 5.9 0.5➀ b0.1 nd – 3 As 0.38–9.47 2.79 1.79 2.77 3.80➁ 24 4.8 0.58 12 Au 0.002–0.067 0.013 0.006 0.021 3➀ b0.05 nd – 11 Ba 49–472 184 162 93 160➀ 170 628 0.29 29 Br 0.55–10.16 4.5 3.21 3.07 9➀ 17 nd – 14 Cl 43–343 148 131 75 264➁ 614 nd – 14 Co 2.4–20.6 9.2 7.7 5.2 7.05➁ 6.1 17.3 0.53 29 Cr 10.7–101.1 34.2 29.1 22.3 15.35➁ 15 92 0.37 29 Cs 0.09–5.88 1.92 0.99 1.93 2.0➀ 1.1 4.9 0.39 14 Cu 22.3–132.9 48.2 44.6 23.2 18.35➁ 16 28 1.72 22 Ga 3.4–31.9 12.8 11.3 7.0 6.52➁ 5.7 17.5 0.73 29 Ge 0.66–5.36 1.68 1.45 1.16 2.97➁ 5.7 nd – 15 Hf 0.63–6.81 2.52 2.16 1.49 3➀ 0.73 5.3 0.48 29 Hg 0.07–0.79 0.26 0.21 0.18 0.19➁ 0.17 0.05 5.20 29 I 1.16–4.79 2.77 2.49 1.28 nd b1.0 nd – 13 In 0.014–0.18 0.068 0.054 0.045 nd b0.3 nd – 14 Mo 2.63–11.37 5.05 4.60 2.47 3.11➁ 3.3 1.1 4.59 14 Nb 2.57–7.76 5.84 5.51 1.81 12➀ 2.9 12 0.49 15 Ni 11.6–20.6 16.4 16.2 2.9 13.71➁ 14 47 0.35 15 Pb 8.2–20.6 18 16.3 10.7 15.55➁ 11 17 1.06 15 Rb 2.3–61.3 17.9 13.9 13.6 8➀ 21 82 0.22 27 Sb 0.224–4.245 1.098 0.721 1.176 0.83➁ 1.2 0.4 2.75 14 Sc 2.4–30.6 9.19 7.98 5.41 4➀ 4.2 14 0.66 29 Sr 28–205 105 94 48.6 149➀ 130 320 0.33 29 Ta 0.143–2.525 0.611 0.499 0.476 0.8➀ 0.22 0.9 0.68 29 Th 2.1–42.9 8.88 7.16 7.76 5.81➁ 3.2 10.5 0.85 29 U 0.47–6.59 2.84 2.46 1.46 2.41➁ 2.1 2.7 1.05 29 V19–191 108 87 65 35.05➁ 22 97 1.11 29 W 0.84–6.04 1.91 1.41 1.52 1.8➀ 1 1.9 1.01 13 Y 15.3–42.1 26.9 25.5 9.2 9➀ 8.5 21 1.28 15 Zn 5–1019 304 33 211 42.18➁ 53 67 4.54 29 Zr 39–138 92.8 87.2 29.5 67➀ 27 193 0.48 15 La 8.6–62.6 31.7 29.5 11.2 17.79➀ 12 31 1.02 29 Ce 26.0–121.8 63.5 60.2 20.3 35.06➀ 21 63 1.01 29 Pr 2.26–9.51 5.86 5.15 1.65 3.76➀ nd 7.1 0.83 15 Nd 8.7–36.6 21.8 20.7 6.5 15.03➀ 9.5 27 0.81 29 Sm 1.89–7.24 4.09 3.92 1.190 3.01➀ 1.7 4.7 0.87 29 Eu 0.337–1.590 0.775 0.74 0.245 0.65➀ 0.4 1 0.78 29 Gd 1.29–6.47 3.24 3.48 1.025 3.37➀ nd 4 0.81 15 Tb 0.225–1.080 0.587 0.559 0.185 0.517➀ 0.3 0.7 0.84 29 Dy 1.46–9.09 3.71 3.49 1.397 3.141➀ nd 3.9 0.95 29 Ho 0.318–2.180 0.789 0.745 0.195 0.731➀ nd 0.83 0.95 15 Er 0.90–6.76 2.22 2.07 0.579 2.081➀ nd 2.3 0.97 15 Tm 0.136–1.130 0.339 0.317 0.084 0.335➀ nd 0.3 1.13 15 Yb 0.84–7.65 2.17 1.97 1.208 1.975➀ 0.95 2 1.09 29 Lu 0.142–1.515 0.417 0.371 0.250 0.323➀ 0.14 0.31 1.35 29 ➀Tang and Huang (2004); ➁Ren et al. (2006);➂Finkelman (1993); ➃Rudnick and Gao (2004).

Shandong, China (Liu et al., 2003), and close to that in the 15.6%, with arithmetic means of 12.1%, 12.7%, 16.4%, Jining Coalfield, Shandong, China (Liu et al., 2005a). 13.2%, and 13.6%, respectively. The sedimentary environments and geological con- The average ash yield of No. 10 Coal in the Shanxi ditions may influence the ash yield of coals. The ash Formation (12.1%) is lower than those in No. 7, 5, 4 Coals yield of No. 10, 7, 5, 4 and 3 Coals from the Huaibei of the Lower Shihezi Formation and the No. 3 Coal of the Coalfield is in the ranges of 1.51% to 23.1%, 12.5% to Upper Shihezi Formation. Thus, the ash yield increases 12.9%, 15.0% to 18.4%, 8.75% to 25.0%, and 10.1% to stratigraphically upward in the Huaibei Coalfield. The ash 中国科技论文在线 http://www.paper.edu.cn

66 L. Zheng et al. / Journal of Geochemical Exploration 97 (2008) 59–68 content in coal may be controlled by sedimentary con- No. 10 Coal of the Shanxi Formation was deposited in an ditions within the mires during coal formation (Brenda, environment slightly influenced by seawater, whereas the 1996). The No. 5 Coal which is partly influenced by No. 7, 5, and 4 Coals of the Lower Shihezi Formation and magmatic intrusion has an average ash yield of 16.4% the No. 3 Coal of the Upper Shihezi Formation were which is higher than the upper No. 4 and 3 Coals (13.2% deposited in a fluvial environment without marine in- and 13.6%, respectively). It appears that the late geologic fluence. Gao et al. (2006) reported that the organic sulfur process can affect the ash content in coals. is the dominant sulfur form in the Huaibei coals.

4.2. Moisture 4.5. Calorific value

In the Huaibei coals, the moisture content ranges from The calorific value is related to carbon content, 1.53% to 3.17%, with an average of 2.10% (Table 1). The moisture, minerals, coal rank and maceral composition moisture contents in the No. 10 Coal of the Shanxi of coals (Liu et al., 2005a). The calorific value of the Formation and in No. 7, 5, and 4 Coals of the Lower Huaibei coals ranges from 24.3 to 34.2 MJ/kg, with an Shihezi Formation are obviously lower than that in the average of 29.1 MJ/kg (Table 1). The average calorific No.3 Coal in the Upper Shihezi Formation (2.56%). The values of the No. 10, 7, 4, and 3 Coals are close, which No. 5 Coal that is influenced by magmatic intrusion has a are 28.1, 28.7, 28.7, and 27.9 MJ/kg, respectively. The low moisture content of 1.92%. No.5 Coal was influenced by magmatic intrusion and thus has lower moisture (average 1.92%) and volatile 4.3. Volatile matter matter (average 36.1%) contents and a higher calorific value (32.1 MJ/kg) than other coals. The volatile matter content in the coals from the Huaibei Coalfield is between 34.3% and 47.2%, with an 4.6. Ash composition average of 38.8% on a dry and ash-free basis (Table 1). The volatile matter content in coals is a measure of coal rank. In The chemical composition of coal ashes varies the Huaibei coals, the volatile matter content varies slight- significantly depending on the nature of mineral matter ly among different coals, and the average is 42.5%, 37.6%, in coal (Liu et al., 2003; Stanislav et al., 1997). In 36.1%, 39.0%, and 38.3% in No. 10, 7, 5, 4, and 3 Coals, general, the major and minor elements in coal ashes are respectively. The No. 5 Coal has the lowest average Si, Al, Ca, Fe, K, Mg, Na, P, Mn, S, and Ti (Table 2). volatile matter content (36.1%). This coal is slightly higher The most abundant constituents of coal ashes of the in rank than other coals because of magmatic intrusion. Huaibei Coalfield are SiO2,Al2O3, CaO, and Fe2O3. The ash of No. 10 Coal of the Shanxi Formation is lower in SiO2 4.4. Sulfur and Al2O3 contents than that of No. 7, 5, and 4 Coals of the Lower Shihezi Formation. The No. 10 Coal was slightly The sulfur content in Chinese coals varies in the influenced by marine water during coal deposition, whereas range between 0.2% and 8% (Gao et al., 2005). The the other coals were deposited in a terrestrial environment abundance of sulfur in coals is related to the depositional without the influence of seawater. The ash of No. 10 Coal is environments of coal seams (Chou, 1990, 1997, 2004; higher in Fe2O3,MgO,P2O5,andSO3 than other coals. Liu et al., 2001, 2004, 2007c; Zheng et al., 2008b). Higher Fe and S contents in the No. 10 Coal indicate a The sulfur content of the Huaibei coals is between higher pyrite content as a result of seawater influence. 0.22% and 1.74%, with an average of 0.66% (Table 1). The ash of the No. 5 Coal is high in SiO2 and Al2O3 Samples HB10-8, HB10-7, and HB10-3 from the No. 10 contents which may be related to magmatic intrusion. In Coal of the Shanxi Formation are medium-sulfur coals general, the ash composition of the Huaibei Coalfield is (1.74%, 1.24%, and 1.5%, respectively), all other samples similar to that of the Zibo and Jining Coalfields in are low-sulfur coals (total sulfur content b1%) (Table 1). Shandong, China (Liu et al., 2003, 2005a), but is The No. 10 Coal (0.96%) of the Shanxi Formation has the different from coals in southwestern Guizhou province, highest average sulfur content, which is followed by the China (Zhang et al., 2004). No. 7 Coal (0.59%), No. 5 Coal (0.64%), and No. 4 Coal (0.51%) of the Lower Shihezi Formation. The No. 3 Coal 4.7. Mineral matter of the Upper Shihezi Formation has the lowest sulfur content. The trend of decreasing sulfur content upwards is Minerals that have been identified in the Huaibei coals related to sedimentary environments of coal seams. The using XRD and SEM include quartz, illite, kaolinite, 中国科技论文在线 http://www.paper.edu.cn

L. Zheng et al. / Journal of Geochemical Exploration 97 (2008) 59–68 67 chlorite, smectite, pyrite, calcite, dolomite, plagioclase Coal has a lower moisture and volatile matter and goethite. The clay mineral content (smectite, illite, contents, but a higher calorific value than other coals. kaolinite, and chlorite) accounts for more than 60% in the (3) Most of the Huaibei coals are low-sulfur, with an studied samples. Pyrite is low in the Huaibei coals, and is average sulfur content of 0.66%. As a result of only observed in samples of the No. 10 Coal of the Shanxi different depositional environments of coals, the Formation because of its depositional environment average sulfur content in coal beds decreases from slightly influenced by seawater. the Shanxi Formation, the Lower Shihezi Forma- tion, to the Upper Shihezi Formation. 4.8. Trace elements in the Huaibei coals (4) The Huaibei coals are enriched in many trace elements of environmental concerns (Ba, Co, Cr, Abundances of trace elements in the Huaibei coals are Cu, Hg, Mo, Ni, Pb, Sb, Th, U, V, and Zn). The listed Table 3. The Huaibei coals are highly enriched in Ag portion of the elements associated with mineral by a factor of up to 22.6, in Zn by a factor of up to 7.2, and matter (mainly pyrite) may be reduced by physical in V by a factor of up to 3.1 as compared to the average of coal cleaning. Chinese coals (Tang and Huang, 2004; Ren et al., 2006). As compared with the average Chinese coals, the Huaibei Acknowledgements coals are enriched in the following elements by small factors: Cu (2.6×), Sc (2.3×), Cr and Rb (2.2×), Ga (2.0×), This work was supported by the National Natural Mo (1.6×), Th (1.5×), Hg and Zr (1.4×), Co (1.3×), Ba, Ni, Science Foundation of China (40772095, 40572090) and Pb, and U (1.2×), and rare earth elements (1–2×). Natural Science Excellent Youth Foundation of Anhui As compared with the upper continental crust (Rudnick Province, China. The authors thank the editor and and Gao, 2004), the Huaibei coals are enriched in Hg, Mo, reviewers for their constructive comments. Zn, and Sb, by factors of 5.20, 4.59, 4.54, and 2.75, respectively (Table 3). References Among the trace elements studied for the Huaibei Coalfield, Ba, Co, Cr, Cu, Hg, Mo, Ni, Pb, Sb, Th, U, V, Brenda, S.P., 1996. Quality and petrographic characteristic character- and Zn are considered to be of environmental concerns istics of Paleocene coals from the Hanna basin, Wyoming. Organic (Swaine and Goodarzi, 1995). During coal utilization, Geochemistry 24, 181–187. trace elements may be redistributed into the atmospheric, Chou, C.-L., 1990. Geochemistry of Sulfur in Fossil Fuels. In: Orr, W.L., White, C.M. (Eds.), ACS Symposium Series 429. American water bodies, and soils, causing environmental contam- Chemical Society, Washington, D.C., pp. 30–52. Chapter 2. ination. Zheng et al. (2008a) showed that Hg in the Chou, C.L., 1997. Geologic factors affecting the abundance, distribution, Huaibei coals occurs mainly in sulfide-bound and and speciation of sulfur in coals. In: Yang, Qi (Ed.), Geology of Fossil organic-bound forms. In some Huaibei coals which are Fuels- Coal. Proceedings of the 30th International Geological – influenced by magmatic intrusion, a significant portion Congress, vol. 18, part B. VSP,Utrecht, The Netherlands, pp. 47 57. Chou, C.-L., 2004. Origins and evolution of sulfur in coals. Western Hg is silicate-bound. The portion of Hg that is associated Pacific Earth Sciences vol. 4 (1), 1–10. with mineral matter (mainly in pyrite) may be removed Dai, S.F., Ren, D.Y., 2006. Fluorine concentration of coals in China— by physical coal cleaning (Toole-O'Neil et al., 1999), but an estimation considering coal reserves. Fuel 85, 929–935. organic-bound Hg in coals cannot be reduced this way. Finkelman, R.B., 1993. Trace and minor elements in coal. In: Engel, M.H., Macko, S.A. (Eds.), Organic Geochemistry. Plenum, New York, pp. 593–607. 5. Conclusions Finkelman, R.B., Gross, P.M.K., 1999. The type of data needed for assessing the environmental and human health impacts of coal. (1) The ash yields of the Huaibei coals are relatively International Journal of Coal Geology 40, 91–101. low. Coal ash in Huaibei coals are composed Finkelman, R.B., William, O., Vincent, C., Calin, A.T., Beklin, H.E., Zheng, B.S., Harry, E.L., Susan, V.M., Anne, L.B., 2002. Health mainly of SiO2,Al2O3, CaO, and Fe2O3 as well as impacts of coal and coal use: possible solutions. International some minor constituents. In some coals, ash yield Journal of Coal Geology 50, 425–343. increases stratigraphically upwards. Coal seams Gao, L.F., Liu, G.J., Chou, C.-L., Zheng, L.G., Zheng, W., 2005. The influenced by magmatic intrusion have higher study of sulfur geochemistry of Chinese coals. Bulletin of Mineralogy, Petrology and Geochemistry 24 (1), 79–87 (in Chinese SiO2 and Al2O3 contents in the ash, and a rela- tively higher ash yield than other coals. with English abstract). Gao, L.F., Liu, G.J., Xue, J., Zhang, H.Y., Zheng, L.G., 2006. (2) Disregarding the No. 5 Coal, the moisture content Determination of sulfur-containing organic compounds in coals in coals increases in the order of No. 10, 7, 4, and 3 from Huaibei coalfield, Anhui Province, China. Environmental Coals. Because of magmatic intrusion, the No. 5 chemistry 25 (4), 498–502 (in Chinese with English abstract). 中国科技论文在线 http://www.paper.edu.cn

68 L. Zheng et al. / Journal of Geochemical Exploration 97 (2008) 59–68

Guan, W.H., Gu, C.L., Lin, Z.S., 2006. Study on the change of energy Xu, X.C., Chen, C.H., Qi, H.Y., He, R., You, C.F., Xiang, G.M., 2000.

consumption structure in China. Journal of Natural Resources 21 Development of coal combustion pollution control for SO2 and (3), 401–407 (in Chinese with English abstract). NOx in China. Fuel Processing Technology 62, 153–160. Liu, G.J., Peng, Z.C., Yang, P.Y., Wang, G.L., 2001. Sulfur in coal and Zhang, J.Y., Ren, D.Y.,Zhu, Y.M., Chou, C.-L., Song, D.Y.,Zheng, B.S., its environmental impact from Yanzhao Mining , China. 2004. Mineral matter and potentially hazardous trace elements in Chinese Journal of Geochemistry 20 (3), 273–281. coals from Qianxi Fault Depression Area in southwestern Guizhou, Liu, G.J., Yang, P.Y., Peng, Z.C., Wang, G.L., Zhang, W., 2003. China. International Journal of Coal Geology, 57, 49–61. Comparative study of the quality of some coals from the Zibo Zhao, Z.G., Tang, X.Y., Li, B.F., 2000. Geochemistry of rare earth coalfield. Energy 28, 969–978. elements of coal in Huaibei Coalfield. Geochemica 29 (6), Liu, G.J., Yang, P.Y., Peng, Z.C., Chou, C.-L., 2004. Petrographic and 578–583 (in Chinese with English abstract). geochemical contrasts and environmentally significant trace Zheng, B.S., Ding, Z.H., Huang, R.G., Zhu, J.M., Yu, X.Y.,Wang, A.M., elements in marine-influenced coal seams, Yanzhou mining area, Zhou, D.X., Mao, D.J., Su, H.C., 1999. Issues of health and disease China. Journal of Asian Earth Science 23, 491–506. relation to coal use in southwestern China. International Journal of Liu, G.J., Zheng, L.G., Gao, L.F., Zhang, H.Y., Peng, Z.C., 2005a. The Coal Geology 40, 119–132. characterization of coal quality from the Jining coalfield. Energy Zheng, L.G., Liu, G.J., Xue, J., 2005. Environmental effects and 30, 1903–1914. comprehensive utilization of waste rocks from Huaibei and Liu, G.J., Stanislav, V.V., Gao, L.F., Zheng, L.G., Peng, Z.C., 2005b. Huainan Coalfields. Journal of Anhui Institute of Architecture & Mineral and chemical composition and some trace element Industry 13, 1–5 (in Chinese with English abstract). contents in coals and coal ashes from Huaibei coal field, China. Zheng, L.G., Liu, G.J., Chou, C.-L., Gao, L.F., Peng, Z.C., 2006a. Energy Conversion and Management 46, 2001–2009. Arsenic in Chinese coals: Its abundance, distribution, modes of Liu, G.J., Zheng, L.G., Nurdan, S.D.A., Gao, L.F., Liu, J.H., Peng, Z.C., occurrence, enrichment processes, and environmental significance. 2007a. Health effects of arsenic, fluorine, and selenium from indoor Acta Geoscientia Sinica 27 (4), 355–366 (in Chinese with English burning of Chinese coal. Review of Environmental Contaminate and abstract). Toxicology 189, 89–106. Zheng,L.G.,Liu,G.J.,Zhang,H.Y.,Gao,L.F.,Xue,J.,2006b.Theaffinity Liu, G.J., Zheng, L.G., Qi, C.C., Zhang, Y., 2007b. Environmental of associated elements in Permian coals from the Huaibei Coalfield. geochemistry and health of fluorine in Chinese coals. Environ- Acta Petrologica et Mineralogica 25 (3), 243–249 (in Chinese with mental Geology 52 (7), 1307–1314. English abstract). Liu, G.J., Zheng, L.G., Zhang, Y., Qi, C.C., Chen, Y.W., Peng, Z.C., Zheng, L.G., Liu, G.J., Chou, C.-L., 2007a. The distribution, 2007c. Distribution and mode of occurrence of As, Hg, and Se and occurrence and environmental effect of mercury in Chinese sulfur in coal seam 3 of the Shanxi Formation, Yanzhou Coalfield, coals. Science of the Total Environment 384, 374–383. China. International Journal of Coal Geology 71, 371–385. Zheng, L.G., Liu, G.J., Chou, C.-L., Qi, C.C., Zhang, Y., 2007b. Ren, D.Y., Zhao, F.H., Dai, S.F., Zhang, J.Y., Luo, K.L., 2006. Geochemistry of rare earth elements in Permian coals from the Geochemistry of Trace Elements in Coals. The Science Press, Huaibei Coalfield, China. Journal of Asian Earth Sciences 31, Beijing, pp. 268–279 (in Chinese). 167–176. Rudnick, R.L., Gao, S., 2004. Composition of the Continental Crust. Zheng, L.G., Liu, G.J., Qi, C.C., Zhang, Y., Wong, M.H., 2008a. The Treatise on Geochemistry, vol. 3. Elsevier, Amsterdam, pp. 1–64. use of sequential extraction to determine the distribution and Stanislav, V.V., Kunihiro, K., Christina, G.V.,1997. Relations between ash modes of occurrence of mercury in Permian Huaibei coal, Anhui yield and chemical and mineral composition of coals. Fuel 76, 3–8. Province, China. International Journal of Coal Geology 73, Swaine, D.J., Goodarzi, F., 1995. Environmental Aspects of Trace 139–155. Elements in Coal. Kluwer Academic Publishers, The Netherlands, Zheng, L.G., Liu, G.J., Chou, C.-L., 2008b. Abundance and modes of pp. 24–50. occurrence of mercury in some low-sulfur coals from China. Tang, X., Huang, W., 2004. Trace Elements in Chinese Coals. The International Journal of Coal Geology 73, 19–26. Commercial Press, Beijing, p. 8 (in Chinese). Toole-O'Neil, B., Tewalt, S.J., Finkelman, R.B., Akers, D.J., 1999. Mercuryconcentrationincoal–unraveling the puzzle. Fuel 78, 47–54.