Fluorine Content and Distribution Pattern in Chinese Coals

International Journal of Coal Geology 57 (2004) 143–149 www.elsevier.com/locate/ijcoalgeo

Fluorine content and distribution pattern in Chinese coals

Kunli Luoa,*, Deyi Renb, Lirong Xua, Shifeng Daib, Daiyong Caob, Fujian Fenga, Jian’an Tana

a Institute of Geographical Sciences and Natural Resource Research, CAS, Building 917, 3 Datun Road, Beijing 100101, China b China University of Mining and Technology, Beijing 100083, 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 20–300 mg/kg, mostly about 50–100 mg/kg. Fluorine content of Permo–Carboniferous coals, the main steam coals in China, is 50–300 mg/kg; Jurassic coals 20–70 mg/kg. There are great differences in fluorine content of Late Permian coals in Southwest China (50–3000 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 50–3000 mg/kg. Fluorine content in all platform areas, where magma activity is less, is comparatively low, about 20–200 mg/kg. D 2004 Elsevier B.V. All rights reserved.

Keywords: Chinese coal; Fluorine content; Distribution pattern; Source

1. Introduction Cheng, 1998). Coal may constitute 70% of the fossil energy resources in China and will play a dominant Coal accounts for 75% of all energy consumed in role in the near future. Fluorine is a noxious trace China, much more than oil, natural gas or hydropow- element in coal. Fluorine is generally emitted as gases er. About 70% (1080 million tons) of the mined coal such as HF, SiF4,CF4, etc., when coal is burned, is directly used as fuel (Fan and Pan, 1995; Wu, 1996; resulting in the contamination of atmosphere (Lu, 1996; Liu et al., 1999, 2000; Qi et al., 2000).HFis 10–100 times more toxic than SO2 and is particularly * Corresponding author. Tel.: +86-10-64856503; fax: +86-10- hazardous for animals and plants (Jeng et al., 1998; 64851844. Piekos and Paslawska, 1999; Notcutt and Davies, E-mail address: [email protected] (K. Luo). 2001). Fluorosis is endemic in China, e.g. Guizhou,

Western Hunan, Southern Shaanxi, mainly resulted Third, the relative proportions of Chinese coal from fluoride-rich coal combustion. China has more resource with different fluorine contents were not cases of fluorosis than any other country, more than taken into account when average fluorine content in 40 million dental fluorosis patients and 2.6 million coals was estimated by Zheng and Cai (1988). The skeletal fluorosis patients (both mainly distribution in average fluorine content of Chinese coal in their paper the North China Plate and a few areas of the South mainly was based on the arithmetical average of their China; Tan, 1989; Finkelman et al., 1999; Finkelman samples. and Gross, 1999). In addition, Chen and Tang (2002) studied fluorine Several studies have determined the fluorine con- content in Chinese coals and summarized the results tent and distribution pattern in Chinese coals (Zheng of other scientists, but the above problems can also be and Cai, 1988; Lu, 1996; Liu et al., 1999, 2000; Qi et found in their research. al., 2000; Luo et al., 2001; Chen and Tang, 2002). But Ren et al. (1999) reported the fluorine content was these studies focused on certain coal mines or coal 100–3600 mg/kg by eight coal samples mainly col- types. There are few integrated studies on fluorine lected from Xishan coal mine in Shanxi Province; content of the Permo–Carboniferous and Jurassic however, sampling locations were chosen because the coals in the North China and Northwest China, which coal seam is in close proximity to basic igneous rocks are widely distributed and used. (about 1 m). Those coal samples also do not represent Zheng and Cai (1988) first reported the average Chinese coals overall. fluorine content in Chinese coals, as 200 mg/kg on Further study of the fluorine content and distribu- average, much more than the world average for coal tion pattern in Chinese coals is needed. For this paper (Swaine, 1990). But among their 337 coal samples, about 300 coal samples were collected to study the 100 samples ‘‘came from 20 provinces in China’’ and fluorine content and distribution pattern in Chinese no explanation of sampling locations were given; 193 coals according to their different coal basins and samples from South China (Yunnan, Guizhou, geologic age. 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 2. Main character of Chinese coal resource the location of the other 4 four samples were not given. There are three main problems with their studies: The spatial distribution of Chinese coals is quite First, their samples are not representative of all uneven, with much more in the North and West and Chinese coals, because most samples were collected less in the South and East. The 11 western provinces from South China, where only about 8% of Chinese have about 5115 billion tons coal, accounting for coals are mined, while only a few samples came from 91.83% of total Chinese coal resource (5570 billion 6 six of the seven largest coal resource provinces— tons). Coal resources are largest in seven western Sinkiang, Inner Mongolia, Shanxi, Shaanxi, Ningxia provinces—Sinkiang, Inner Mongolia, Shanxi, and Gansu. Shaanxi, Guizhou, Ningxia and Gansu, among which Second, no explanation of sampling method was the six northwestern provinces north of Kunlun-Qin- given. There can be great differences in fluorine ling Mountains have about 84% of Chinese coal content even in the same coal seam. Luo et al. resources, while the southwestern areas (mainly Guiz- (1994) studied Silurian stone coal in Shaanxi Province hou and Yunnan) have only 7% (Zeng, 2001; Chen and found that the fluorine content of one lump of and Zhang, 1993). stone coal was 82 mg/kg, but the another lump was The main coal-forming periods in China were the 4200 mg/kg from different parts of the same coal Pennsylvanian, Permian and Jurassic. The Permo– seam. So sampling method according to strict criterion Carboniferous coals are the main coals used for power (strip sampling and channel sampling according to GB generationinChina(Zeng, 2001), accounting for 482-1995 (Chinese sampling standard of coal)) is very nearly 58% of Chinese coals. Among them, Taiyuan important, and the fluorine content of the lump of coal Formation of Pennsylvanian coals and Shanxi Forma- sample is not representative of the coal seam. tion of Early Permian coals account for 27% and 17%, K. Luo et al. / International Journal of Coal Geology 57 (2004) 143–149 145 respectively, mainly in North China and Northwest 1995 (Chinese sampling standard of coal seam), mak- China; Shihezi Formation of Late Permian coals ing a straight channel in the coal bed, then collecting account for about 3%, mainly in Northwest China; the coal and gangue in the channel as the sample (Yang Longtan Formation of Late Permian coals account for et al., 1998). about 10%, mainly in Southwest China (Yunnan and All samples were analyzed for fluorine by the Guizhou Province). Jurassic coal accounts for about Northwest Geological Testing Center of Northwest 39% of Chinese coals (mainly in Northwest China) Geological Research Institute, Geological Testing and the other coals (mainly Triassic, Cretaceous and Center of Coal Academy of Sciences in Xi’an, Shaanxi Tertiary coals) about 5% (Chen and Zhang, 1993). and Coal Testing Center of Shaanxi Quality Testing Center. Alkali-fusion/fluorine ion-selective electrode method was used to analyze some samples before 3. Samples collecting and analytical methods 1998, and most samples were analyzed by pyrohy- drolysis/fluorine ion-selective electrode method dur- Fluorine content in Chinese coals is closely related ing 1999–2002 in the above testing centers (Yang et to the structural position of coal basins, roughly al., 1998). For quality control in chemical analysis, the correlating with volcanic activity and magmatic intru- standard reference materials (GBW11122 (coal, Chi- sion, as well as the age of magmatic intrusion and the na), GBW08402 (coal fly ash, China), Chinese Stan- source of the volcanic and magmatic rocks (Luo et al., dard Sample Study Center, Chinese Academy of 1994, 2001, 2002; Luo and Zhang, 1996). Coals in the Measurement Sciences) were randomly analyzed with same tectonic unit having the similar paleostructure, each batch of coal and gangue samples. The relative paleogeography, paleoclimate, tectonism and meta- standard deviation was less than 10% and the detection morphism during and after the coal-forming process limit was 10À 9. will have the similar fluorine content (Luo et al., 2001, 2002). Therefore, it is reasonable to collect coal samples 4. Average fluorine content in Chinese coals and analyze their fluorine content according to their structure positions and geologic ages than according Many factors should be taken into account when to coal type (Luo et al., 2002). fluorine content in coals is evaluated, such as the Coal samples were collected from the coal formed different coal-forming basins, different coal-forming in various coal-forming periods. Permo–Carbonifer- periods, different coal types, especially their different ous coals, the main steam coals in the North China proportions to Chinese coal resource. Plate and the Northwest China, were sampled from We use the following symbols to simplify the Hancheng Chenghe and Tongchuan mines (5#, 10# formula: and 11# coal) in Shaanxi province, including Liaoyuan Mine in Hancheng (Permian coal of Shanxi Forma- A0—the average fluorine content in Jurassic coal tion), Xiangshan, Sangshuping and Magouqu mines in (about 39%); the Hancheng Mine, the Tongchuan Mine and the B0—the average fluorine content in Pennsylvanian Pubai Mine (Pennsylvanian coal of Taiyuan Forma- coal (mainly Taiyuan Formation, about 27%); tion)—the typical coal basin in west of North China C0—the average fluorine content in Early Permian Plate. Samples also came from the Datong, Pingshuo coal (mainly Shanxi Formation, about 17%) and Xishan mines in Shanxi province—the typical coal D0—the average fluorine content in Late Permian basin in west of North China Plate; from 4#, 8# and 9# coal (mainly Longtan Formation, about 10%) coals of Pingyin Mine in Shandong province—the E0—the average fluorine content in coal of the typical coal basin in east part of North China Plate; other periods (including Shihezi Formation Early from the main coal mines in Guizhou, West Hunan and Permian and Neogene coal, about 5%). Yunnan Provinces in Southwest China. Samples collecting methods in this paper are mainly channel So the average fluorine content in Chinese coals sampling and strip sampling according to GB 482- ( F) can be expressed as F = A0 Â 39% + B0 Â 27% + 146 K. Luo et al. / International Journal of Coal Geology 57 (2004) 143–149

C0 Â 17% + D0 Â 10% + E0 Â 5%, giving an average 5. Fluorine distribution pattern in Chinese coals of about 82 mg/kg, close to that in the world (80 mg/kg). Fluorine content in all platform areas, where mag- Fluorine-rich coal reserves are not large in China, matic activity was less active, is comparatively low, which only include Late Permian coals of the Longtan about 50–300 mg/kg. For example, fluorine content Formation in Yunnan and Guizhou (only about 10% of most Permo–Carboniferous coals is less than 200 of Chinese coal). Stone coals are not included in mg/kg in North China Plate, in the Northwest China Chinese coal resource, but they would make a great and Yangzi Plate, mostly about 50–100 mg/kg. Fluo- impact on local human health because of their distri- rine content of coals in the platform may decrease bution in the South, which has low coal resources. 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 Sampling spot Number Marginal Platform Coal Sampling Number Igneous Platform Coal gangue epoch of platform gangue spot of developing samples and samples province in geosyncline marginal platform J South of Shaanxi 12 400–500 300–350 Shenfu, 8 20 200–250 Shaanxi Tiemu Temple, 2 20–50 300–350 Sinkiang 12 20–50 200–400 Sichuan

P2 Southwest of 12 400–1500 400 Guizhou Qujing, Yunnan 50–1500 and Zhijin, Guizhou Liangshan 3 50–380 200–300 Moutain and Huanyingshan Moutain, Sichuan

P1 Pingshuo, 6 100–200 300–400 Shanxi Datong, 60 50–250 200–500 Shanxi (3#) Weibei, 18 50–290 Shaanxi (2#,3#)

C2 Pingshuo, 30 50–150 Shanxi (8#,11#) Datong, 12 50–150 Shanxi (8#) Weibei, 50 50–150 150–500 Shaanxi (11#,10#,5#) Xishan, 8 200–600 Beijing (8#) S Ankang, Shaanxi 20 400–3000 O Ankang, Shaanxi 5 400–700

1 South of Shaanxi, 30 400–1500 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. K. Luo et al. / International Journal of Coal Geology 57 (2004) 143–149 147

Table 2 Relation between fluorine content and igneous rock of coals in southwest China and Daba Area, Qinling Mountain Sampling spot Number of Sampling mode Rock type Fluorine content Epoch Distance from Sampling Samples (g tÀ 1) igneous rock (m) depth (m)

Zhijin, Guizhou 2 strip sample coal 52 P2 >100 2 Zhijin, Guizhou 2 lump sample coal 1200 P2 1 0.2 Qujing, Yunnan 2 strip sample coal 68 P2 >50 2 Qujing, Yunnan 2 lump sample coal 1100 P2 12 Datong, Shanxi 2 lump sample coal 950 C2 2 0.2 Datong, Shanxi 2 lump sample coal 215 C2 30 0.1 Wamiao, Ziyang 2 channel sample stone coal 1500 1 12 Wamiao, Ziyang 4 channel sample stone coal 620 1 51 Maoba, Ziyang 5 channel sample stone coal 430 2 100 1 Tiefo, Langao 3 channel sample stone coal 615 1 10 1.5 Haoping, Ziyang 2 channel sample syenite-porphyry 1618 S1 1 (from stone coal) 10 Haoping, Ziyang 5 channel sample stone coal 2200 S1 2.0 3 Haoping, Ziyang 5 lump sample bottom of stone coal 1500 S1 3.4 0.1 content of anthracites, generally speaking, is less than related with coal-forming periods and circumstances. 100 mg/kg and high rank bituminous coal is less than Permo–Carboniferous coals (11# and 5#) with high 150 mg/kg. Fluorine content in Chinese coals is also rank are widely distributed in Northwest and North

Fig. 1. Map showing fluorine content and distribution pattern in Chinese coals. 148 K. Luo et al. / International Journal of Coal Geology 57 (2004) 143–149

China, where fluorine content is about 50–150 mg/ coals is about 82 mg/kg, close to that in the world kg, a little lower than 2# and 3# Permian coals, where (80 mg/kg). fluorine content is about 150 mg/kg. Fluorine content Fluorine content in Chinese coals is closely relat- is about 100 mg/kg in Late Permian coal measures in ed structural position of coal basins, the amount of Yunnan and about 20–50 mg/kg in Jurassic coals in volcanic activity and magmatic intrusion, as well as most coal basins in the Northwest China. Fluorine the age and the source of volcanic and magmatic content of coal gangue in Northwest and North China rocks. Frequent volcanic activity and magma intru- is about 200–700 mg/kg, much higher than coals in sion is the main reason for fluorine-rich coals and the same strata. Whether in South or in North China, stone coals in geosynclines region and on the edge fluorine content of coals is relatively low if there was of platform areas, such as Southeast Qinling Moun- no influence of magmatic activity at the same or later tain (Daba Area), Dabie Mountain as well as south- time (Table 1). west China, where fluorine content is about 50–3000 In geosyncline areas (e.g. the east of Kunlun- g/kg. Fluorine content is quite low (about 50–200 Qinling Mountain-Daba Area in South Shaanxi and mg/kg) in the platform areas, where there is little Dabie Mountain in North Hubei) and on the edge of magma activity. platform areas (e.g. Southwest China), there have been In China, low-fluorine coals are mainly distributed numerous tectonic movements, especially since Cam- in stable platforms in North China and Northwest brian. Volcanism brought abundant fluorine into coal China. Medium- to high-fluorine coals are mainly in basins and coal seams. Fluorine is more enriched by Guizhou-Yunnan, where there was more volcanic absorption by organic matter and clay in coal-bearing activity and magma intrusion during and after coal- strata. It is very clear that volcanic activity and magma forming period than the North China Plate. Super- intrusion are the primary reasons for fluorine-rich high-fluorine coals include stone coal in igneous rock coals in Daba Area, Dabie Mountain Area and South- in geosynclines region South Qinling Mountain and west China, where there was more volcanic activity Late Permian coals of Longtan Formation, occur in and magmatic intrusion during and after coal-forming the southwest of Yunnan and Guizhou, but not all Late period than the on North China Plate. The fluorine Permian coals in Yunnan and Guizhou are high- content in coal correlates negatively with the distance fluorine coals, so not more than 3% of Chinese coals from igneous rock in geosyncline areas and on the are high-fluorine coals (stone coals are not included in edge of platform areas (Table 2). Chinese coal reserves). But most of high-fluorine Fig. 1 shows fluorine content and distribution pat- coals are anthracite coals and local people directly tern in Chinese coals. The Permo–Carboniferous and use them as fuel for cooking and for warmth in winter. Jurassic coals in North China and Northwest China are So the high-fluorine and superhigh-fluorine coals mainly low-fluorine coals, accounting for nearly 90% have resulted in serious indoor air pollution and of Chinese coals. High-fluorine coals in China include human health problems in Daba Area of South Qin- Permo–Carboniferous coals on the edge of platform ling Mountain and Yunnan-Guizhou. 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 Acknowledgements and Guizhou, but not all Late Permian coals in Yunnan and Guizhou are high-fluorine coals. Stone coals are The authors express their heartfelt thanks to Dr. not included in Chinese coal reserves, so most of Robert B. Finkelman, U.S. Geological Survey for his Chinese coals are low-fluorine coals. help in editing the English text. We also like to thank Wei Bingren, Wang Biyu, Gao Bolin, Zhao Xian- gyou, the staff in Xiangshan and Magouqu Coal 6. Conclusions Mine, the staff in Coal Power Group, and some students of Geology Department in Xi’an University Most Chinese coals are low-fluorine coals ( < 200 of Science and Technology for their valuable help. mg/kg). The average fluorine content in Chinese The Chinese Key Project for the Chinese Tenth Five- K. Luo et al. / International Journal of Coal Geology 57 (2004) 143–149 149

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