Fluorine content and distribution pattern in Chinese coals

Size: px

Start display at page:

Download "Fluorine content and distribution pattern in Chinese coals"

Felicity Rogers
5 years ago
Views:

1 International Journal of Coal Geology 57 (2004) Fluorine content and distribution pattern in Chinese coals Kunli Luo a, *, Deyi Ren b, Lirong Xu a, Shifeng Dai b, Daiyong Cao b, Fujian Feng a, Jian an Tan a a Institute of Geographical Sciences and Natural Resource Research, CAS, Building 917, 3 Datun Road, Beijing , China b China University of Mining and Technology, Beijing , China Received 13 April 2003; received in revised form 29 September 2003; accepted 9 October 2003 Abstract About 300 coal samples were collected to study the fluorine content and distribution pattern in Chinese coals in different coal basins and geologic periods. The Permo Carboniferous and Jurassic coals in the North China Plate and Northwest China account for nearly 90% of Chinese coals and their fluorine content is mg/kg, mostly about mg/kg. Fluorine content of Permo Carboniferous coals, the main steam coals in China, is mg/kg; Jurassic coals mg/kg. There are great differences in fluorine content of Late Permian coals in Southwest China ( mg/kg), which accounts for only 7% of Chinese coals. According to the proportions of the coals with different fluorine content in Chinese coal resources, the average fluorine content of Chinese coals is about 82 mg/kg, which is close to the world average (80 mg/kg). Most Chinese coals are low-fluorine coals ( < 200 mg/kg). Fluorine content in Chinese coals is closely related with structure position of coal basins, the degree of volcanic activity and magma intrusion, as well as the age, and source of the volcanic and magmatic rock. Frequent volcanic activity and magma intrusion is the main reason for fluorine-rich coals and stone coals in South Qinling Mountain (Daba Area) and Southwest China, where fluorine content is about mg/kg. Fluorine content in all platform areas, where magma activity is less, is comparatively low, about mg/kg. D 2004 Elsevier B.V. All rights reserved. Keywords: Chinese coal; Fluorine content; Distribution pattern; Source 1. Introduction Coal accounts for 75% of all energy consumed in China, much more than oil, natural gas or hydropower. About 70% (1080 million tons) of the mined coal is directly used as fuel (Fan and Pan, 1995; Wu, 1996; * Corresponding author. Tel.: ; fax: address: luokl@igsnrr.ac.cn (K. Luo). Cheng, 1998). Coal may constitute 70% of the fossil energy resources in China and will play a dominant role in the near future. Fluorine is a noxious trace element in coal. Fluorine is generally emitted as gases such as HF, SiF 4, CF 4, etc., when coal is burned, resulting in the contamination of atmosphere (Lu, 1996; Liu et al., 1999, 2000; Qi et al., 2000). HFis times more toxic than SO 2 and is particularly hazardous for animals and plants (Jeng et al., 1998; Piekos and Paslawska, 1999; Notcutt and Davies, 2001). Fluorosis is endemic in China, e.g. Guizhou, /$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi: /j.coal

2 144 K. Luo et al. / International Journal of Coal Geology 57 (2004) Western Hunan, Southern Shaanxi, mainly resulted from fluoride-rich coal combustion. China has more cases of fluorosis than any other country, more than 40 million dental fluorosis patients and 2.6 million skeletal fluorosis patients (both mainly distribution in the North China Plate and a few areas of the South China; Tan, 1989; Finkelman et al., 1999; Finkelman and Gross, 1999). Several studies have determined the fluorine content and distribution pattern in Chinese coals (Zheng and Cai, 1988; Lu, 1996; Liu et al., 1999, 2000; Qi et al., 2000; Luo et al., 2001; Chen and Tang, 2002). But these studies focused on certain coal mines or coal types. There are few integrated studies on fluorine content of the Permo Carboniferous and Jurassic coals in the North China and Northwest China, which are widely distributed and used. Zheng and Cai (1988) first reported the average fluorine content in Chinese coals, as 200 mg/kg on average, much more than the world average for coal (Swaine, 1990). But among their 337 coal samples, 100 samples came from 20 provinces in China and no explanation of sampling locations were given; 193 samples from South China (Yunnan, Guizhou, Sichuan, Hubei, Hunan and Guangxi Province), including 7 stone coal samples and 186 coal samples; 40 samples from the east edge of North China Plate and the location of the other 4 four samples were not given. There are three main problems with their studies: First, their samples are not representative of all Chinese coals, because most samples were collected from South China, where only about 8% of Chinese coals are mined, while only a few samples came from 6 six of the seven largest coal resource provinces Sinkiang, Inner Mongolia,, Shaanxi, Ningxia and Gansu. Second, no explanation of sampling method was given. There can be great differences in fluorine content even in the same coal seam. Luo et al. (1994) studied Silurian stone coal in Shaanxi Province and found that the fluorine content of one lump of stone coal was 82 mg/kg, but the another lump was 4200 mg/kg from different parts of the same coal seam. So sampling method according to strict criterion (strip sampling and channel sampling according to GB (Chinese sampling standard of coal)) is very important, and the fluorine content of the lump of coal sample is not representative of the coal seam. Third, the relative proportions of Chinese coal resource with different fluorine contents were not taken into account when average fluorine content in coals was estimated by Zheng and Cai (1988). The average fluorine content of Chinese coal in their paper mainly was based on the arithmetical average of their samples. In addition, Chen and Tang (2002) studied fluorine content in Chinese coals and summarized the results of other scientists, but the above problems can also be found in their research. Ren et al. (1999) reported the fluorine content was mg/kg by eight coal samples mainly collected from Xishan coal mine in Province; however, sampling locations were chosen because the coal seam is in close proximity to basic igneous rocks (about 1 m). Those coal samples also do not represent Chinese coals overall. Further study of the fluorine content and distribution pattern in Chinese coals is needed. For this paper about 300 coal samples were collected to study the fluorine content and distribution pattern in Chinese coals according to their different coal basins and geologic age. 2. Main character of Chinese coal resource The spatial distribution of Chinese coals is quite uneven, with much more in the North and West and less in the South and East. The 11 western provinces have about 5115 billion tons coal, accounting for 91.83% of total Chinese coal resource (5570 billion tons). Coal resources are largest in seven western provinces Sinkiang, Inner Mongolia,, Shaanxi, Guizhou, Ningxia and Gansu, among which the six northwestern provinces north of Kunlun-Qinling Mountains have about 84% of Chinese coal resources, while the southwestern areas (mainly Guizhou and Yunnan) have only 7% (Zeng, 2001; Chen and Zhang, 1993). The main coal-forming periods in China were the Pennsylvanian, Permian and Jurassic. The Permo Carboniferous coals are the main coals used for power generation in China (Zeng, 2001), accounting for nearly 58% of Chinese coals. Among them, Taiyuan Formation of Pennsylvanian coals and Formation of Early Permian coals account for 27% and 17%,

3 K. Luo et al. / International Journal of Coal Geology 57 (2004) respectively, mainly in North China and Northwest China; Shihezi Formation of Late Permian coals account for about 3%, mainly in Northwest China; Longtan Formation of Late Permian coals account for about 10%, mainly in Southwest China (Yunnan and Guizhou Province). Jurassic coal accounts for about 39% of Chinese coals (mainly in Northwest China) and the other coals (mainly Triassic, Cretaceous and Tertiary coals) about 5% (Chen and Zhang, 1993). 3. Samples collecting and analytical methods Fluorine content in Chinese coals is closely related to the structural position of coal basins, roughly correlating with volcanic activity and magmatic intrusion, as well as the age of magmatic intrusion and the source of the volcanic and magmatic rocks (Luo et al., 1994, 2001, 2002; Luo and Zhang, 1996). Coals in the same tectonic unit having the similar paleostructure, paleogeography, paleoclimate, tectonism and metamorphism during and after the coal-forming process will have the similar fluorine content (Luo et al., 2001, 2002). Therefore, it is reasonable to collect coal samples and analyze their fluorine content according to their structure positions and geologic ages than according to coal type (Luo et al., 2002). Coal samples were collected from the coal formed in various coal-forming periods. Permo Carboniferous coals, the main steam coals in the North China Plate and the Northwest China, were sampled from Hancheng Chenghe and Tongchuan mines (5#, 10# and 11# coal) in Shaanxi province, including Liaoyuan Mine in Hancheng (Permian coal of Formation), Xiangshan, Sangshuping and Magouqu mines in the Hancheng Mine, the Tongchuan Mine and the Pubai Mine (Pennsylvanian coal of Taiyuan Formation) the typical coal basin in west of North China Plate. Samples also came from the Datong, Pingshuo and Xishan mines in province the typical coal basin in west of North China Plate; from 4#, 8# and 9# coals of Pingyin Mine in Shandong province the typical coal basin in east part of North China Plate; from the main coal mines in Guizhou, West Hunan and Yunnan Provinces in Southwest China. Samples collecting methods in this paper are mainly channel sampling and strip sampling according to GB (Chinese sampling standard of coal seam), making a straight channel in the coal bed, then collecting the coal and gangue in the channel as the sample (Yang et al., 1998). All samples were analyzed for fluorine by the Northwest Geological Testing Center of Northwest Geological Research Institute, Geological Testing Center of Coal Academy of Sciences in Xi an, Shaanxi and Coal Testing Center of Shaanxi Quality Testing Center. Alkali-fusion/fluorine ion-selective electrode method was used to analyze some samples before 1998, and most samples were analyzed by pyrohydrolysis/fluorine ion-selective electrode method during in the above testing centers (Yang et al., 1998). For quality control in chemical analysis, the standard reference materials (GBW11122 (coal, China), GBW08402 (coal fly ash, China), Chinese Standard Sample Study Center, Chinese Academy of Measurement Sciences) were randomly analyzed with each batch of coal and gangue samples. The relative standard deviation was less than 10% and the detection limit was Average fluorine content in Chinese coals Many factors should be taken into account when fluorine content in coals is evaluated, such as the different coal-forming basins, different coal-forming periods, different coal types, especially their different proportions to Chinese coal resource. We use the following symbols to simplify the formula: A 0 the average fluorine content in Jurassic coal (about 39%); B 0 the average fluorine content in Pennsylvanian coal (mainly Taiyuan Formation, about 27%); C 0 the average fluorine content in Early Permian coal (mainly Formation, about 17%) D 0 the average fluorine content in Late Permian coal (mainly Longtan Formation, about 10%) E 0 the average fluorine content in coal of the other periods (including Shihezi Formation Early Permian and Neogene coal, about 5%). So the average fluorine content in Chinese coals ( F) can be expressed as F = A 0 39% + B 0 27% +

4 146 K. Luo et al. / International Journal of Coal Geology 57 (2004) C 0 17% + D 0 10% + E 0 5%, giving an average of about 82 mg/kg, close to that in the world (80 mg/kg). Fluorine-rich coal reserves are not large in China, which only include Late Permian coals of the Longtan Formation in Yunnan and Guizhou (only about 10% of Chinese coal). Stone coals are not included in Chinese coal resource, but they would make a great impact on local human health because of their distribution in the South, which has low coal resources. 5. Fluorine distribution pattern in Chinese coals Fluorine content in all platform areas, where magmatic activity was less active, is comparatively low, about mg/kg. For example, fluorine content of most Permo Carboniferous coals is less than 200 mg/kg in North China Plate, in the Northwest China and Yangzi Plate, mostly about mg/kg. Fluorine content of coals in the platform may decrease with their increase in metamorphic degree. Fluorine Table 1 Fluorine content and distribution pattern in Chinese coals (mg/kg) Coal- South of China North of China forming epoch Sampling spot Number of samples Marginal platform and geosyncline Platform Coal gangue Sampling spot Number of samples Igneous developing province in marginal platform Platform Coal gangue J South of Shaanxi Shenfu, Shaanxi Tiemu Temple, Sichuan Sinkiang P 2 Southwest of Guizhou Qujing, Yunnan and Zhijin, Guizhou Liangshan Moutain and Huanyingshan Moutain, Sichuan P 1 Pingshuo, Datong, (3#) Weibei, Shaanxi (2#,3#) C 2 Pingshuo, (8#,11#) Datong, (8#) Weibei, Shaanxi (11#,10#,5#) Xishan, Beijing (8#) S Ankang, Shaanxi O Ankang, Shaanxi South of Shaanxi, Hunan and Hubei Note: is a hyphen and it means the range of fluorine content from 400 to 500 mg/kg generally; # in the back or the front of the number commonly means the number of coal seam in China.

5 K. Luo et al. / International Journal of Coal Geology 57 (2004) Table 2 Relation between fluorine content and igneous rock of coals in southwest China and Daba Area, Qinling Mountain Sampling spot Number of Samples Sampling mode Rock type Fluorine content (g t 1 ) Epoch Distance from igneous rock (m) Zhijin, Guizhou 2 strip sample coal 52 P 2 >100 2 Zhijin, Guizhou 2 lump sample coal 1200 P Qujing, Yunnan 2 strip sample coal 68 P 2 >50 2 Qujing, Yunnan 2 lump sample coal 1100 P Datong, 2 lump sample coal 950 C Datong, 2 lump sample coal 215 C Wamiao, Ziyang 2 channel sample stone coal Wamiao, Ziyang 4 channel sample stone coal Maoba, Ziyang 5 channel sample stone coal Tiefo, Langao 3 channel sample stone coal Haoping, Ziyang 2 channel sample syenite-porphyry 1618 S 1 1 (from stone coal) 10 Haoping, Ziyang 5 channel sample stone coal 2200 S Haoping, Ziyang 5 lump sample bottom of stone coal 1500 S Sampling depth (m) content of anthracites, generally speaking, is less than 100 mg/kg and high rank bituminous coal is less than 150 mg/kg. Fluorine content in Chinese coals is also related with coal-forming periods and circumstances. Permo Carboniferous coals (11# and 5#) with high rank are widely distributed in Northwest and North Fig. 1. Map showing fluorine content and distribution pattern in Chinese coals.

6 148 K. Luo et al. / International Journal of Coal Geology 57 (2004) China, where fluorine content is about mg/ kg, a little lower than 2# and 3# Permian coals, where fluorine content is about 150 mg/kg. Fluorine content is about 100 mg/kg in Late Permian coal measures in Yunnan and about mg/kg in Jurassic coals in most coal basins in the Northwest China. Fluorine content of coal gangue in Northwest and North China is about mg/kg, much higher than coals in the same strata. Whether in South or in North China, fluorine content of coals is relatively low if there was no influence of magmatic activity at the same or later time (Table 1). In geosyncline areas (e.g. the east of Kunlun- Qinling Mountain-Daba Area in South Shaanxi and Dabie Mountain in North Hubei) and on the edge of platform areas (e.g. Southwest China), there have been numerous tectonic movements, especially since Cambrian. Volcanism brought abundant fluorine into coal basins and coal seams. Fluorine is more enriched by absorption by organic matter and clay in coal-bearing strata. It is very clear that volcanic activity and magma intrusion are the primary reasons for fluorine-rich coals in Daba Area, Dabie Mountain Area and Southwest China, where there was more volcanic activity and magmatic intrusion during and after coal-forming period than the on North China Plate. The fluorine content in coal correlates negatively with the distance from igneous rock in geosyncline areas and on the edge of platform areas (Table 2). Fig. 1 shows fluorine content and distribution pattern in Chinese coals. The Permo Carboniferous and Jurassic coals in North China and Northwest China are mainly low-fluorine coals, accounting for nearly 90% of Chinese coals. High-fluorine coals in China include Permo Carboniferous coals on the edge of platform areas (e.g. Zhangjiakou of Hebei Province, Mentougou of Beijing on the north edge of North China Plate) and Late Permian coals of Longtan Formation in Yunnan and Guizhou, but not all Late Permian coals in Yunnan and Guizhou are high-fluorine coals. Stone coals are not included in Chinese coal reserves, so most of Chinese coals are low-fluorine coals. 6. Conclusions Most Chinese coals are low-fluorine coals ( < 200 mg/kg). The average fluorine content in Chinese coals is about 82 mg/kg, close to that in the world (80 mg/kg). Fluorine content in Chinese coals is closely related structural position of coal basins, the amount of volcanic activity and magmatic intrusion, as well as the age and the source of volcanic and magmatic rocks. Frequent volcanic activity and magma intrusion is the main reason for fluorine-rich coals and stone coals in geosynclines region and on the edge of platform areas, such as Southeast Qinling Mountain (Daba Area), Dabie Mountain as well as southwest China, where fluorine content is about g/kg. Fluorine content is quite low (about mg/kg) in the platform areas, where there is little magma activity. In China, low-fluorine coals are mainly distributed in stable platforms in North China and Northwest China. Medium- to high-fluorine coals are mainly in Guizhou-Yunnan, where there was more volcanic activity and magma intrusion during and after coalforming period than the North China Plate. Superhigh-fluorine coals include stone coal in igneous rock in geosynclines region South Qinling Mountain and Late Permian coals of Longtan Formation, occur in the southwest of Yunnan and Guizhou, but not all Late Permian coals in Yunnan and Guizhou are highfluorine coals, so not more than 3% of Chinese coals are high-fluorine coals (stone coals are not included in Chinese coal reserves). But most of high-fluorine coals are anthracite coals and local people directly use them as fuel for cooking and for warmth in winter. So the high-fluorine and superhigh-fluorine coals have resulted in serious indoor air pollution and human health problems in Daba Area of South Qinling Mountain and Yunnan-Guizhou. Acknowledgements The authors express their heartfelt thanks to Dr. Robert B. Finkelman, U.S. Geological Survey for his help in editing the English text. We also like to thank Wei Bingren, Wang Biyu, Gao Bolin, Zhao Xiangyou, the staff in Xiangshan and Magouqu Coal Mine, the staff in Coal Power Group, and some students of Geology Department in Xi an University of Science and Technology for their valuable help. The Chinese Key Project for the Chinese Tenth Five-

7 K. Luo et al. / International Journal of Coal Geology 57 (2004) Year Plan (Grant No. 2001BA704B03) and Chinese National Key Project for Basic Research (Grant No. G ) as well as the Knowledge Innovation Foundation of Institute of Geographical Sciences and Natural Resource, Chinese Academy of Sciences (Grant No. SJ10G-A01-03) supported this work. References Chen, P., Tang, X.Y., Fluorine in coal of China. Coal Geology of China 14, (in Chinese, with English Abstr.). Chen, W.M., Zhang, Z.S., Coal Chemistry Coal Industry Press, Beijing (in Chinese). Cheng, Y.Q., On spreading the application of clean coal technology in China. China Coal 24 (4), (in Chinese, with English Abstr.). Fan, W.T., Pan, H.Z., To develop clean coal technology in China. China Coal 21 (1), (in Chinese, with English Abstr.). Finkelman, R.B., Gross, P.M.K., The types of data needed for assessing the environmental and human health impacts of coal. International Journal of Coal Geology 40, Finkelman, R.B., Belkin, H.E., Zheng, B.S., Health impacts of domestic coal use in China. Proceedings of the National Academy of Sciences of the United States of America 96 (7), Jeng, J.H., Hsieh, C.C., Lan, W.H., Cytotoxicity of sodium fluoride on human oral mucosal fibroblasts and its mechanisms. Cell Biology and Toxicology 14 (6), Liu, J.Z., Yao, Q., Cao, X.Y., Cen, K.F., Research on the measurement and regularities of distribution of fluorides in coal. Coal Geology & Exploration 27 (2), 9 12 (in Chinese, with English Abstr.). Liu, J.Z., Qi, Q.J., Cao, X.Y., Zhou, J.H., Cen, K.F., Studies on existence pattern, combustion transfer and retention mechanism of fluorine in coal. China Science & Technology Periodical 6 (10), (in Chinese, with English Abstr.). Lu, B.H., Occurrence mode of fluorine and chlorine in coal seam of China. Geology & Exploration 24 (1), 9 11 (in Chinese, with English Abstr.). Luo, K.L., Zhang, Z.S., Study on the source of fluorine poisoning in Ziyang County of Shaanxi. Environmental Protection in Coal Mine 4, (in Chinese, with English Abstr.). Luo, K.L., Chen, D.M., Ge, L.M., Accompanied and Associated Ores of the Paleozoic Black Shale and Coal, Shaanxi Province, China Northwest University Press, Xi an (in Chinese). Luo, K.L., Li, R.B., Wang, L.Z., Tan, J.A., Xiang, L.H., Fluorine content and distribution pattern of coal and its source in China. Journal of Environmental Sciences 22, (in Chinese, with English Abstr.). Luo, K.L., Xu, L.R., Li, R.B., Xiang, L.H., Fluorine emission amount from combustion of steam coal of North China Plate and northwest China. Chinese Science Bulletin 47 (16), Notcutt, G., Davies, F., Environmental accumulation of airborne fluorides in Romania. Environmental Geochemistry and Health 23 (1), Piekos, R., Paslawska, S., Fluoride uptake characteristics of fly ash. Fluoride 32 (1), Qi, Q.J., Liu, J.Z., Zhou, J.H., Cao, X.Y., Cen, K.F., Review on determination methods of trace element fluorine in coal. Coal Conversion 23 (2), 7 10 (in Chinese, with English Abstr.). Ren, D.Y., Zhao, F.H., Wang, Y.Q., Yang, S.J., Distributions of minor and trace elements in Chinese coals. International Journal of Coal Geology 40, Swaine, D.J., Trace Elements in Coal Butterworths, London. Tan, J.A., The Atlas of Endemic Diseases and their Environments in the People s Republic of China. Science Press, Beijing, pp (in Chinese). Wu, R.T., The developing trend of coal production in China. China Coal 22 (12), (in Chinese, with English Abstr.). Yang, J.H., Chen, W.M., Duan, Y.L., Handbook of Coal Testing Coal Industry Press, Beijing (in Chinese). Zeng, Y., Special coal types in Western China and their exploitation and utilization. Journal of China Coal Society 26 (4), (in Chinese, with English Abstr.). Zheng, B.S., Cai, R.G., Study on fluorine content in China coal. Chinese Journal of Control of Endemic Diseases 3 (2), (in Chinese).

Arsenic content and distribution pattern in Chinese coals

Toxicological & Environmental Chemistry, Oct. Dec. 2005; 87(4): 427 438 Arsenic content and distribution pattern in Chinese coals LUO KUNLI Institute of Geographical Sciences and Natural Resources Research,