Coal is an organic rock and mineral with high reduction barrier and adsorption barrier. Under certain geological conditions, some useful metal elements can be enriched to reach the scale of mineralization. Based on some research data at home and abroad, this paper discusses the abundance, occurrence, geological origin and utilization possibility of beneficial metals niobium, gallium, rhenium and scandium in coal and coal-bearing rock series. The study on the enrichment or mineralization of rare metal elements in coal is one of the important contents of coal geochemistry and deposit geochemistry, which deserves further strengthening.
Selected Papers on Coal Petrology and Coal Geochemistry in Ren Deyi
There are some precious beneficial elements in the composition of trace elements in coal, and some of them have been enriched and integrated into associated deposits with considerable scale, which has attracted more and more attention. For example, in Jurassic coal-bearing basins such as Kazakhstan, Kyrgyzstan, Yili and Tuha in Xinjiang, large uranium deposits have been found in sandstone beds on the roof of coal seams and some coal seams, and some of them have formed production capacity. Another example is the Mesozoic-Cenozoic large lignite germanium deposits found in Lincang, Yunnan, Wulantuga mining area, Inner Mongolia and Russian coastal border areas. The main characteristics of these sediments can be found in many literatures [1 ~ 8].
In recent years, highly enriched rare metal elements such as gallium, niobium, rhenium and scandium, rare earth elements and precious metal elements such as silver, gold and platinum group elements have been found in coal. Many high-content trace elements in coal are potentially important strategic mineral resources or economically recoverable by-products of coal processing. Strengthening its exploration and deeply studying its occurrence and enrichment law are conducive to fully and rationally utilizing coal resources and mineral resources associated with * * * and developing circular economy.
Based on the literature and known data, the elements such as niobium, gallium, rhenium and scandium are briefly described as follows.
I. Niobium
Niobium is a rare metal with strong corrosion resistance and high melting point. Its alloy is super heat-resistant and super light. It can be used as an important material for missiles, rockets and aerospace engines, as well as an important superconducting material and a rare metal in great demand in the world. Clark value of niobium in the earth's crust is 265438±0μg/g/g. According to Ketris and Yudovich [9], the average content of niobium in coal in the world is 3.7 μ g/g. Russian scholar середин suggested that niobium content in coal should be evaluated as an associated useful mineral.
The anomaly of niobium in coal may be syngenetic, mainly because coal syngenetic with weathering crust is often rich in niobium. Under the condition of supergene zone, niobium can be combined with organic acids, such as niobium-containing mineral powder in fulvic acid solution, which can make the niobium content in the solution reach 1mg/L within 4 or 5 months, which is hundreds of times higher than that in natural water.
Secondly, when there is diopside altered by acidic pyroclastic rocks in the coal seam, niobium will also be enriched in the adjacent coal. Hower et al. reported that the niobium content in the upper and lower layers of tonstein gangue beds in the eastern Kentucky of the United States was extremely high, reaching 55 ~ 88 μ g/g and 76 ~ 150 μ g/g [10] respectively.
The anomaly of niobium in coal may also be affected by metal-bearing hydrothermal solution. Seredin reports [1 1] A graben-type Eocene lignite in the Russian Far East was reformed by hot liquid rich in niobium, so that the niobium content in the coal reached 60μ g/g/g.
Some coals in the world are rich in niobium. The content of niobium in Permian coal in Kuznets coalfield of Russia can reach 30 ~ 50μ g/g, and the content of niobium in coal ash can reach180 ~ 360μ g/g. The content of niobium in No.30 coal seam of Essex coalfield in Minutinsk Carboniferous-Permian coalfield is 90μg/g, and the content of niobium in coal ash is 580μ g/g ... Two layers of Miocene lignite with a thickness of 90m and 22m in Zetaf coalfield in Poland are enriched with niobium, and the content of niobium in coal ash exceeds 200μ g/g [6, 12,/kloc-0].
The average content of niobium in the Upper Permian coal in Heshan, Guangxi is 50μg/g, in which the content of niobium in the upper coal with the thickness of No.4 coal seam 1. 1m in Liuhualing Mine is 126μg/g, which is 689μ g/g [14] converted into coal ash. According to Dai et al.' s research, the average niobium content in No.34 coal seam of Upper Permian in Zhijin coalfield of Guizhou is 64μg/g, and that in No.3 coal seam of Upper Permian in Dafang coalfield is 80 μ g/g [15 ~ 17].
The analysis by Spears and Zheng [18] on the main coalfields in Britain shows that illite is the main carrier of niobium in coal. Liu Dameng and others [19] analyzed the Antaibao mine in Shanxi and reached a similar conclusion. Niobium in coal from Kuznets coalfield, Russia is mainly enriched in pyrochlore and tantalite. Palmer et al. [20] confirmed that 66% of niobium in the studied coal was organic by six-step chemical extraction. Querol et al. [2 1] studied Neogene sulfur-bearing lignite in Beypazary, Turkey, and found that the main component of coal was organic niobium. It can be seen that the occurrence state of niobium in different coals varies from place to place.
Dai Shifeng et al. [22] and Zhou Yiping [23] reported that Nb is highly enriched in coal and mudstone of alkaline pozzolanic altered claystone in southwest China. Alkaline mudstone can not only be used as an isochronous marker layer, but also be used to find the location of ancient crater according to the spatial distribution law of the horizon and thickness of alkaline mudstone in coal-bearing series, which is of great significance to find rare elements related to the construction of alkaline volcanic rocks.
Second, gallium (Ga)
Gallium is a typical dispersed element, which is used in optical fiber communication equipment, computers and color TV displays. The Clark value of gallium is 16μ g/g [24]. It is difficult to form an independent gallium deposit in nature, but it is mainly recovered from bauxite and sphalerite deposits. The global content of gallium in coal is 5.8μg/g, while the average content of gallium in coal ash is 33 μ g/g [9]. The average content of gallium in coal in China is 6.5 μ g/g [7].
The content of gallium in some coalfield coals in the world is high, and the content of gallium in the ash of some coals is as high as several hundred micrograms per gram. Therefore, the combustion by-products of gallium-rich coals have the potential to extract gallium. According to the regulations of National Mineral Reserves Committee 1987, the industrial utilization standard of gallium in various gallium-bearing deposits is 20μg/g for bauxite and 30μg/g for coal.
The research of Zhou Yiping and Ren Youliang [25] shows that the content of gallium in upper Permian coal ash in southwest China can reach 63.7 ~ 4010.5 μ g/g, which mainly exists in organic state and is lower than that in upper Permian coal ash.
No.6 coal in Heidaigou extra-thick coal seam of Zhungeer coalfield in Inner Mongolia is a typical example of gallium enrichment in coal [26, 27]. The average content of Ga in this coal seam is 44.6μg/g, and some horizons can reach 76 μ g/g. Micro-area analysis shows that the main carrier of Ga is boehmite in coal, and some of it is distributed in organic matter [26, 27]. Moreover, the coal is also unusually rich in al, which leads to a high concentration of Al2O3 in the coal-fired products of this coal seam, and the Al2O3 content in the fly ash exceeds 50%. Therefore, No.6 coal seam in Heidaigou is a gallium-aluminum deposit coexisting with coal. Although the Halwusu and Guanbanwusu coals in the south and north of Heidaigou are rich in gallium, they have not yet reached industrial grade. With the increase of coal production in recent years, the amount of coal resources rich in gallium and aluminum in Heidaigou is decreasing year by year, which should be paid great attention by relevant departments to protect this rare coal resource. In addition, the fly ash discharged from the power plant burning No.6 coal seam in this area accumulates all the year round, forming artificial deposits rich in al and Ga. The distribution, occurrence and migration characteristics of aluminum and gallium in this artificial deposit deserve further study.
The coal in the "two Russian feet" coal seam in Chernogor coal-producing area of Minsk coalfield in Russia contains 30 μ g/g of gallium, and the coal ash contains 375 μ g/g of gallium. Miocene germanium-bearing coal in Lakovsk coal-producing area of Russian Far East contains 30 ~ 65μ g/g gallium, and coal ash contains 0/00 ~ 300 μ g/g gallium. In the low ash coal in Amos, a carboniferous coal seam in the northwest of Kentucky, USA, the coal ash contains gallium 140 ~ 500μ g/g [28].
The research of Affolter( 1998) shows that the ash content of raw coal in a large power plant in Kentucky, USA is 70μg/g, and the slag content is
It can be seen that the by-products of coal combustion, mainly fine fly ash, have become the third main source of comprehensive recovery of gallium from minerals in the world.
Three. rhenium (Re)
Rhenium is a rare metal with super heat resistance, which is the material of a new generation of aerospace engines, strategic mineral resources, efficient catalysts and materials for manufacturing new medical devices. Rhenium is an extremely dispersed element, and the Clark value of rhenium in the crust is only 0.6 ng/g [24]. When it is used as an associated metal, the content of rhenium in the mineral is required to be not less than 2 ng/g. In the copper-bearing sandstone-type copper deposit in Lezkazgan, Kazakhstan, rhenium locally reaches industrial grade. Russia середин [6] suggested that when the rhenium content in coal exceeds 1μg/g, it can be evaluated as a beneficial associated rhenium mineral resource.
According to the annual reports клер and неханов 198 1, Jurassic coal in Anglian, Uzbekistan contains 0.2 ~ 4 μ g/g of rhenium.
Lignite in carbonate rocks of HerBraud Basin in northern Spain contains 9 μ g/g of rhenium. This "lignite" is rich in asphaltene and ash, and its characteristics are close to those of oil shale.
Rhenium is often enriched in coal of uranium deposits. In the uranium-rich zone on the upper part of the reduction zone of the 4m-thick uranium-coal deposit in Lower Ili, Kazakhstan, the average rhenium content is 9.5μg/g；/g; The average content of rhenium in the lower part of coal seam transition zone is 4.2μg/g/g, and coal can reduce and enrich perrhenate in solution as a reduction barrier.
According to the report юровский 1968, the clean coal (Ad=8%) of Volney Yang in Nanpuli, Donetsk coalfield contains 4μg/g rhenium.
The content of rhenium in coal was determined by high resolution inductively coupled plasma mass spectrometry (ICP-MS), but rhenium was not detected in most domestic samples. However, the contents of rhenium in coal samples from Kailuan, Hebei, Jining, Shandong, Taiyuan Formation, Jincheng, Shanxi, Upper Permian coal seam in Xingren, Guizhou and Upper Triassic coal seam in Anyuan, Jiangxi are 0. 106 ~ 0.39 μ g/g, although these values are lower than those required for associated ore evaluation. Rhenium in early and middle Jurassic uranium deposits in Xinjiang deserves attention.
Four. scandium (Sc)
Scandium is a rare metal with high heat resistance, and it is very expensive to manufacture light alloy. At present, it is mainly extracted from the waste residue of tungsten, titanium, uranium and other metals (scandium content is 80 ~ 100μ g/g), and the output is quite low. середин proposed that when the content of scandium in coal ash exceeds 100μg/g, it can be evaluated as a beneficial by-product of coal combustion [6]. According to the report of Ketris and Yudovich, the average content of scandium in coal is 3.9μg/g and that in coal ash is 23 μ g/g [9].
Recent research shows that the content of scandium in coal ash in some coal-producing areas is quite high. The content of scandium in coal ash of chernigov open-pit coal mine, Kartan open-pit coal mine and Nanjilgai coal mine in Kuznets coalfield is100 ~ 200μ g/g [31]. After the heavy-liquid separation of coal, it is found that the scandium content in the low-density clean coal in Chernogor coal-producing area of Kuznets coalfield is 400μg/g, so the clean coal rich in scandium can be extracted in the coal preparation stage. The scandium content in coal ash of some coal seams in Minsk coalfield of Russia is 95 ~ 1 75μ g/g, and that in low-density coal is 400μ g/g ... The upper coal seam of Beryozov coal production area in Kansk-Achinsk Jurassic coalfield of Russia/kloc-0 contains scandium 230μg/g, and its scandium content in ash reaches 870μ g/g.
Amos coal seam in northwest Kentucky, USA is very thin (
The average scandium content in Upper Permian coalfield in Heshan, Guangxi is 42.2μg/g, while the scandium content in coal ash in the middle of No.4 coal seam in He Sui Coal Mine is 22 1 μ g/g [14].
Other by-products that are extremely high in element content in coal and may be recovered include vanadium, antimony, cesium, molybdenum, tungsten, beryllium, tantalum, rare earth, zirconium and hafnium.
It is of great significance to explore and evaluate the beneficial mineral resources associated with coal. The deficiency of this work in coal resource exploration is hard to make up. When doing this work, you need to pay attention to the following matters.
(1) Optimize the best beneficial elements test method to ensure the reliability of the test results.
(2) Because the beneficial elements associated with * * * in coal is often enriched in the local horizon and specific space of coal seam, it is necessary to pay attention to the reasonable arrangement of sampling points to grasp the law of its enrichment and integration.
(3) The best way to utilize the beneficial metal elements in coal is to extract them from fly ash. Therefore, it is very important to study the habit of beneficial elements in the process of coal combustion and other processing and utilization, as well as the enrichment degree of beneficial elements in coal by-products and the possibility of its recovery.
(4) The beneficial minerals associated with * * * in coal are often polymetallic, and there are often potential harmful elements besides beneficial elements. Therefore, it is necessary to conduct a comprehensive technical, economic and environmental assessment to ensure that the impact of potential harmful factors on the environment and human health is minimized during the development process.
Take the exam and contribute.
[1] Zhuang Hanping, Lu, Fu Jiamo, et al. Study on the occurrence of germanium in Lincang super-large germanium deposit. China Science (Series D),1998,28 (Supplements): 37 ~ 42.
Hu, Bi, Su Wencheng et al. Germanium-rich hydrothermal solution and abnormal enrichment of germanium in coal. China Science Bulletin,1999,44 (sup. ) : 257 ~ 258
Qi, Hu, Su, etc. Genesis of continental hydrothermal sedimentary siliceous rocks and super-large germanium deposits: A case study of Lincang germanium deposit. China Science (Series D), 2003,33 (3): 236 ~ 246.
Zhuang Xinguo, Quirolx, Alastuey A, et al. Geochemical and mineralogical study of Cretaceous Wulantuga high germanium coal deposit in Shengli coalfield, Inner Mongolia. International Journal of Coal Geology, 2006,66:19 ~136.
Sun Lei, Ma, etc. Geology and distribution of germanium deposits in Shengli coalfield, Inner Mongolia Autonomous Region. Journal of Coal, 2007,32 (11):1147 ~151.
[6] Середин В В.Металлоносностъ углей: условия формирования и перспективы освоения.в:угольнаябазаиссии，тVI。 Москва: Геоинформмарк,2004.С 453 ~ 5 19
Ren, Zhao Fenghua, Dai Shifeng, et al. Trace element geochemistry of coal. Beijing: Science Press, 2006: 35 1 ~ 366.
Du, Zhuang Xinguo, Kui Luoer, et al. Distribution of Germanium in Wulantuga High Germanium Deposit in Shengli Coalfield, Inner Mongolia. International Journal of Coal Geology, 2009,78 (1):16 ~ 26.
[9] Ketris M.P., Yudrich Ya E. Clarkes Estimation of Carbonaceous Biorocks: World Average of Trace Elements in Black Shale and Coal. International Journal of Coal Geology, 2009,78 (2):135 ~148
[10] Hower J.C. ruppert L.F. eble C.F. Rare earth elements, yttrium and zirconium elements in the fire clay coal seam in eastern Kentucky are abnormal. International Journal of Coal Geology,1999,39, 14 1 ~ 153.
[1 1] Sheredin v. The first data of abnormal niobium content in Russian coal. Dockwra Di College, Rossi,1994,335,634 ~ 636.
[12] Seredin V Y, Finkelman R B. Metal-bearing coal: a summary of main genesis and geochemical types. International Journal of Coal Geology, 2008,76: 255 ~ 289
[ 13] Юдович ЯЭ,Кетрис МП.Данные элементы -примеси в углях.Екатеринбург: Уральское отделение Российской Академии Наук,2006, 1 ~ 538
[14] Zeng R, Zhuang X, Koukouzas N, et al. Characteristics of trace elements in late Permian sulfur-rich coal in Heshan coalfield, Guangxi. International Journal of Coal Geology, June, 20051:87 ~ 95
[15] Dai Sheng, Ren Dan, Hou×, Shao L. Geochemical and mineralogical anomalies of late Permian coals in Zhijin coalfield, southwest China and their volcanic origin. International Journal of Coal Geology, May 2003:117 ~138
[16] Dai Sheng, Ren Dan, Tang Yong, et al. Enrichment and distribution of elements in late Permian coal in western Guizhou. International Journal of Coal Geology, June, 20051:19 ~137
Mineralogy and geochemistry of late Permian coal in Dafang coalfield, Guizhou Province: the influence of siliceous and iron-rich calcareous hydrothermal solution. International Journal of Coal Geology, June, 20051:241~ 258
[18] Spears DA, Zheng Y. Geochemistry and sources of elements in some British coals. International Journal of Coal Geology,1999,38:161~179.
[19] Liu Deming, Yang Qing, Tang Tianzhu, et al. Sulfur and element geochemistry in Antaibao open-pit coal mine, Pingshuo, Shanxi. International Journal of Coal Geology, 200 1, 46: 5 1 ~ 64
[20] Palmer C A, Krasnow M R, Finkelman R B, et al. Leaching evaluation to determine the occurrence mode of specific toxic elements in coal. J Coal quality, 1993,12:135 ~141
[2 1] Querol X, Fernández-Turiel J L, ló pez-soler a. Trace elements in coal and their behaviors during combustion in large power plants. Fuel,1995,74 (3): 331~ 343
Dai Shifeng, Zhou Yiping, Ren Deyi, et al. Geochemical and mineralogical characteristics and genesis of late Permian coal in Songzao mining area, Chongqing China Science Series D: Earth Science, 2007,37 (3): 353 ~ 362.
Zhou Yiping. Early alkaline volcanic ash alteration zone in Longtan, southwest China. Coalfield Geology and Exploration,1999,27 (6): 5 ~ 9.
[24] Rudnic, Gao, the composition of continental crust. Papers on geochemical crust. Amster Dam: Elsevier; 2004: 1 ~ 64
Zhou Yiping, Ren Youliang. Distribution of Gallium in Late Permian Coalfield Coal in Southwest China and Geochemical Characteristics of Gallium in Coal Seam Oxidation Zone. Geological Review,1982,28 (1): 47 ~ 59.
Dai Shifeng, Ren Deyi, Li Shengsheng. Super-large gallium deposit discovered in Zhungeer, Inner Mongolia. Science Bulletin, May, 20061(2):177 ~185.
Dai Sheng, Ren Dan, Zhou Chunlin, et al. Mineralogy and geochemistry of No.6 coal (Pennsylvanian) in Junggar coalfield, Ordos Basin, China. International Journal of Coal Geology, 2006,66: 253 ~ 270.
[28] Hower J.C. Ruppert L.F. Williams D.A. "Control of Boron and Germanium Distribution in Low Sulfur Amos Coal Seam in Coalfield of Western Kentucky, USA". International Journal of Coal Geology, 2002, 53: 27 ~ 42.
[29] Mardon S.M. Hower J.C. "The influence of coal characteristics on the quality of coal combustion by-products: an example of Kentucky power plant". International Journal of Coal Geology, 2004, 59: 153 ~ 169.
Acid leaching of gallium from coal powder and extraction of foam sponge. Journal of Central South Institute of Mining and Metallurgy,1994,25 (6): 762 ~ 766
[31] Nifantov B.F. Valuable toxic elements in coal. Coal resources in Russia, geological indicator: Moscow, 2003: 77 ~ 9 1
[32] Arbuzov ·S·I, Ershov VV, and Richer Vanov LP, The Potential of Rare Metals in Coal in Misa Basin. Russian Siberian branch. Akkad Sci。 , Novosibirsk. 2003: 347
Potential symbiotic and associated mineral resources in coal and coal-bearing strata-a problem worthy of attention
Ren Deyi, Dai Shifeng
(State Key Laboratory of Coal Resources and Safe Mining, CUMT (Beijing), Beijing100083;
CUMT School of Earth Sciences and Surveying and Mapping Engineering (Beijing), Beijing 100083)
Abstract: Coal is an organic rock and mineral deposit with high reduction barrier and adsorption barrier properties. Under certain geological conditions, it can enrich some useful metal elements and reach the scale of mineralization. Based on the literature at home and abroad, the abundance, occurrence, geological origin and utilization possibility of useful metals niobium, gallium, rhenium and scandium in coal and coal-bearing strata are discussed. The study on the enrichment or mineralization of rare metal elements is one of the main topics in coal geochemistry and deposit geochemistry, so it needs to be further strengthened.
Keywords: coal; Coal-bearing strata; Rare metals; Symbiotic and associated deposits
(This paper was co-authored by Ren Deyi and Dai Shifeng and originally published in Coal Geology of China, No.21Vol.2, 2009 10).