Research on the environmental trace elements in permian coals and their ashes from Huainan coalmine area,China

The contents of environmental trace elements in permian coal from Huainancoalmine area and their combustion products were tested by ICP-MS.Analysis and comparativeresearches on the contents of eighteen environmental trace elements in coal andits combustion product suggest that Se and Cd have a high level of distribution in coals;As, Se, Cd, Sb and As, Se, Cd, Mo, Be, Sb also have a high level of distribution in 815 ℃and 1 100 ℃ coal ashes, respectively.Combustion temperature, thermodynamics featuresof trace elements and ash content in coal are the main factors that influence theabundance of trace elements in coal and ash.

Characteristics of Coal Ashes in Yanzhou Mining District and Distribution of Trace Elements in Them

In the process of combustion of coal organic and inorganic materials in it will undergo a complex variation. Part of them will become volatiles and, together with coal smoke, enter into atmosphere, some will remain in micro-particulates such as ash and dust and find their way into atmosphere in the form of solid particles, and the rest will be retained in ash and slag. Coal ashes are the residues of organic and inorganic substances in coal left after coal combustion and the composition of coal ashes is dependent on that of minerals and organic matter in coal. This paper deals with the chemical composition of coal ashes, the distribution of trace elements in them and their petrological characteristics, and also studies the relationship between the yield of coal ashes and the distribution of trace elements. In addition, a preliminary study is also undertaken on the factors that affect the chemical composition of coal ashes. As viewed from the analyses of coal ash samples collected from the Yanzhou mining district, it can be seen clearly that coal ashes from the region studied are composed chiefly of crystalline materials, glassy materials and uncombusted organic matter and the major chemical compositions are SiO 2, Al 2O 3, Fe 2O 3, and CaO, as well as minor amounts of SO 3, P 2O 5, Na 2O, K 2O and TiO 2. During the combustion of coal, its trace elements will be redistributed and most of them are enriched in coal ashes. At the same time, the concentrations of the trace elements in flying ash are much higher than those of bottom ash, i.e., with decreasing particle-size of coal ashes their concentrations will become higher and higher. So the contents of trace elements are negatively proportional to the particle-size of coal ashes. There has been found a positive correlation between the trace elements Th, V, Zn, Cu and Pb and the yield of coal ashes while a negative correlation between Cl and the yield of coal ashes.

Bioleaching of trace elements and rare earth elements from coal fly ash

Coal fly ash originated from coal combustion has high concentrations of metals. If suitable leaching techniques are identified, then coal fly ash could serve as a useful source of valuable minerals including rare earth elements (REEs). In this study, three microbial strains, Candida bombicola, Phanerochaete chrysosporium and Cryptococcus curvatus were tested on their performance of leaching trace elements and REEs from fly ash. Through comparing mineral loss and leaching efficiencies resulting from indirect leaching or use of the culture supernatant, C. bombicola was identified to be the best leading to the highest mineral loss and extracting efficiencies of trace elements and REEs among the three strains. The highest mineral loss observed from using the supernatant of this yeast strain was 59.7%. Among all trace elements, As and Mo had the highest leaching efficiency of 80.9% and 79.5%. respectively. The same leaching test led to 67.7% of Yb and 64.6% of Er dissolved from the ash. This study, thus, demonstrated that bioleaching is feasible for leaching metals out of fly ash. The C. bombicola strain deserves further investigation due to its robust actions on metal leaching.

Trace elements of Carboniferous–Permian coal from the Adaohai Mine, Daqingshan Coalfield, Inner Mongolia, China

A total of 48 samples of Carboniferous–Permian coal was taken from the Adaohai Mine, Daqingshan Coalfield, Inner Mongolia, China. Cu2 coal is the major coalseam of the Daqingshan Coalfield. The samples were analyzed by the ?nductively coupled plasma–mass spectrometer method.The results indicate the content of V, Cr, Cu, Zn, Ga, Se, Ag,Cd, In, Ba, Pb and U of the Cu2 coals from Adaohai Mine is higher than that of the common Chinese coals. Compared to the world hard coals, the content of V, Cu, Zn, Ga, Se, Sr, Ag,Cd, In, Ba and U is relatively high. Compared to the clark values of the crust, only elements Se, Ag, Pb and Bi are enriched in the coal. Most of the elements in coal benches are lower than in those in roofs and partings. The statistical analysis and clustering analysis showed that the modes of trace elements occurrence for the Cu2 coal correlated positively with the minerals. The values of Sr/Ba show that the coal forming environment was influenced both by sea water and fresh water.

Distribution Characteristics of Sulfur and the Main Harmful Trace Elements in China's Coal

To promote the rational development and use of clean coal resources in China, data on the regional and age distribution of sulfur, arsenic and other harmful elements in Chinese coal was broadly collected, tested for content, and analyzed. Coal in northwestern China is characterized by low to extremely low levels of sulfur; the coal of the Taiyuan Formation in northern China mainly has high-sulfur content; that of the Shanxi Formation is mainly characterized by low sulfur coal; and the Late Permian coal in southern China has overall higher sulfur content; other regions have low sulfur coal. The average content of harmful trace elements in the bulk of China＇s coal is similar to the corresponding content in the coal of the North America and the rest of the world, whereas the content of various elements （Hg, Sb and Se） is different in magnitude to the corresponding percentage in the crust. The average content of the elements Cr, Se, Co, Be, U, Br in Late Permian coal in S China ranks first in the country whereas the average content of Hg and CI in the coals of Late Carboniferous to Early Permian age in N China are the highest. The average content of Mn in Early and Middle Jurassic coal is higher in NW China. The high content of harmful elements in some coal should cause particular concern both in the development and utilization of coal.

Impact of coal gangue on the level of main trace elements in the shallow groundwater of a mine reclamation area

Coal gangue is the most used filling material during reclamation of areas suffering subsidence from min- ing. Main trace element levels (F, As, Hg, and Pb) in shallow groundwater in the reclamation area may be affected by leaching from the gangue. This can has an impact on the application of the water for agricul- tural irrigation or use as drinking water. Therefore, it is of great significance to understand the effect coal gangue has on the shallow groundwater of a reclaimed area. We studied the effect of coal gangue on fluo- rine, arsenic, mercury, and lead levels in the shallow groundwater of a reclamation area by testing the water and the coal gangue. One well near the reclamation area was used as a control well and element levels in water from this well and from the soil next to the well were also measured. The results show that the levels of these elements are increasing in the reclamation area over time. The increase in fluorine, arsenic, mercury, and lead in monitor wells varies from 7.42% to 8.26%, from 7.13% to 7.90%, from 4.85% to 6.48%, and from 4.69% to 6.42%, respectively. Fluorine and arsenic levels are lower in monitor wells than in the control water. The other elements are found in greater concentration than in the control. The Nemerow index also indicates that the shallow groundwater in the reclamation area I is moderately affected by the back-filling coal gangue, while the shallow groundwater in the reclamation area II and III are slightly affected by the back-filling coal gangue. This shallow groundwater could be used for agri- cultural irrigation or for drinking.

Mineralogy,distribution,occurrence and removability of trace elements during the coal preparation of No.6 coal from Heidaigou mine

Optical microscopy and scanning electron microscopy in conjunction with energy dispersed X-ray spectrometry(SEM–EDX)were used to study the minerals and the concentrations of 33 trace elements in No.6 coal from Heidaigou mine.The distributions,organic affinity and removability of 18 trace elements were studied by float-sink experiments.A determination of the maceral groups was also undertaken.A high mineral content,dominated by kaolinite,was found in No.6 coal from Heidaigou mine.The bauxite content was relatively high and it was mainly present as individual particles in fusinite lumens or was intimately intergrown with carbonate minerals.The pyrite and quartz contents were low.Some marcasite with a parallel twin structure was observed by cross-polar reflected light.A small amount of bean-like goyazite was present in the calcite.The weighted trace element content in Heidaigou formations is relatively low,which is beneficial for coal processing and utilization.The concentrations of Ga,Hg,Pb,Se,Th,Ta are relatively high compared with the average values of Chinese coals.As,Hg,Mo,Ge,Ga,Ta,Ti,W,Mn are mainly present in minerals while B,Be,Th,P,Sc,Sr,V,Y,Yb are mainly found in organic matter.As,Ge,Hg,Mo are mainly present in sulfides and Be,Th,P,Sc,Sr,Y,Yb are mainly present in inertinite.B and V are mainly present in vitrinite.The high organic affinity and the low theoretical removability of most trace elements cause difficulties in removing them during coal preparation.

The Trace Elements are Bounded by Organic Functional Groups in Coal:A Studying Result Based on FTIR Analysis

The relationship between trace elements in coal and organic functional groups of coal, also some of aromatic structure, was investigated by using curve fitting of infrared spectra. Cluster analysis was also performed according to the degree of affinity of organic groups to the trace elements. The results show that there is a possibility that trace elements, especially LREE, were bound to peripheral organic functional groups of middle rank coal macromolecule. The most possible functional group that binds trace element is the hydroxyl, and to the less degree, the asymmetric -CH3 and 〉CH2 stretching, -CH3 stretching, etc. The degree of affinity of trace elements to different functional groups varies. The tendency obeys the natural structural changing law of trace elements-- the periodic law. The deviation of some trace elements from this regular trend is attributed to the deviation of intrinsic ＂confusion degree＂ （conventional molar entropy） of the matter system of coal basin, which is affected by the inner and outer factors during the evolution.

Geochemical characteristics of REY, Li, Ga trace elements in the No. 9 coal seam of the Daheng mine, Ningwu coalfield, Shanxi Province, China

To understand the geochemical characteristics of the No.9 coal in the Daheng Mine of the Ningwu coalfield,the trace element analysis was conducted through X-ray fluorescence spectroscopy(XRF)and inductively coupled plasma mass spectrometry(ICP-MS).The sedimentary environment was discussed according to the element geochemical parameters.The results show that Li,Ga,Hf,Zr,Nb,Th,and Ta are slightly enriched in the No.9 coal of Daheng Mine.The average value of the rare earth elements and yttrium(ΣREY)in coal here is 144.20μg/g(excluding parting),which is higher than the average value ofΣREY in the world’s coal and China’s coal.The light rare earth elements(LREY)are enriched.The content of Eu was 0.12‒2.10μg/g with an average of 0.57μg/g,and the Eu is obviously negatively abnormal.Most of the trace elements in the coal are positively correlated with the ash content,which shows that the occurrence of these trace elements is related to inorganic minerals.The results of sequential chemical extraction experiments show that rare earth elements mainly exist in coal in the form of aluminosilicate.The value of the Sr/Ba and the content of S reflect that the coal-forming environment was influenced by seawater.The values of V/Cr and Ni/Co reflect that the peat swamp is in an anaerobic environment and a strongly reducing environment during the coal-forming period.

Characteristics of trace elements of the No.9 coal seam from the Anjialing Mine, Ningwu coalfield, China

Trace elements of the No. 9 coal seam from Aanjialing mine were measured by ICP–MS. The results indicated that Li, Ga, Cr, Sr, Zr and Pb are significantly enriched in the No. 9 coal seam. The Li and Ga contents in most of the coal seam samples reached an economically valuable level. Most trace elements were enriched near the roof and floor. The data from the Sr/Ba, V/Zn, Th/U, V/Zr and V/Ni ratios reveal that during this period, the peat swamp from this area was formed in swamp water, which was influenced by sea-water or, in an sea-land transition environment, where the ancient water salinity was slightly high. The Eu negative anomaly obviously shows that the rare earth elements are consistent with the terrigenous rocks, so we deduced that the rare earth elements contained in the mineral may mainly come from terrestrial detritus.

Vertical variation of trace elements and its relation to the water-bearing capacity of Ordovician strata,in Datun coal field

We tested for fourteen trace elements in samples collected from the Ordovician strata in Datun coal field.The vertical concentration variation of these trace elements is reported.The relationship of the variation to the water-bearing capacity of the Ordovician strata is discussed.The minimum concentration of eleven(of 14 total) trace elements appears in the lower Majiagou formation.The maximum concentrations mainly appear in the Badou and Jiawang formations:eight maxima are located in Badou and four more are in Jiawang.The study of karst development and the water-bearing capacity of Ordovician strata shows that karst is well developed in the Majiagou formation and there is a consequent high water-bearing capacity in this formation:Badou and Jiawang formations are contrary to this situation.The results illustrate that the minimum concentrations of most trace elements within certain Ordovician formations can be taken as strong evidence for the existence of a well developed karst and a high water-bearing capacity.

The transformation and concentration of environmental hazardous trace elements during coal combustion

Studied the content and distribution of 18 environmental hazardous trace elementsin the lignite, fatty coal, anthracite and its burnt products by combustion simulatingexpriment in the one-dismensinal boiler.The transformations and concentration of 18 traceelements during different coal combustion were discussed.The results show that there aresome content distribution of 18 hazardous trace elements in every burnt product, but thelaw of concentration and dispersion of every trace element during different coal combustionis very different.Experiment results indicate that the transformation and concentrationof trace elements during coal combustion are related to the element contents and occur-rencesof trace elements in raw coal, but are also affected by some man-made factorssuch as the combustion method of boiler, combustion temperature and atmosphere, thetype of precipitators and so on.

Study of trace elements in coal and mining wastes and its significance in China

In the world energy about 26% of all was derived from coal combustion. Nearly 80% of the electricity produced in China is generated from coal. Coal will play the most important role in the coming 50 years as the past century in China. However one consequentially of the mining and combustion of coal is the mobilization of trace elements, especially trace metals, which have environmental and human health significance. Information on concentrations and distributions of potentially toxic elements in coal, and information on the modes of occurrence of these elements and the relations of the minerals in coal can help to predict the behavior of the potentially toxic trace metals during cleaning, combustion, weathering, and leaching.

Composition and Trace Element Content of Coal in Taiwan

Researches on trace elements in coal and their influence on environment and human health were introduced. Some 4 coal samples were taken from Taiwan to test the content of trace elements. The author holds that a further study is needed for understanding the modes of occurrence of elements during the deposition and coalification stage in the studying area.

Biology Migration and Distribution Characteristics of Trace Elements in Reconstructed Soil with Coal Gangue Filling

With mixed gangue,coarse gangue and washed gangue as well as the maize in the reclaimed land in Luling Mine of Huaibei as the research object,the biology migration and distribution characteristics of trace elements in the reconstructed soil with different types of coal gangue filling were studied,the contents of Cu,Pb,Zn,Sn,Hg,Cd and Cr were determined,and the distribution characteristics of the trace elements in the coal gangue and different organs of the maize were analyzed.The results showed that the contents of trace elements were the highest in washed gangue and the least in coarse gangue in the gangue used for the reclamation,and there were significant differences in the enrichment ability of trace elements in different organs of maizes that were planted in reclamation land,of which fruit was weaker than other organs,while leaf presented strong absorption ability.

Geochemistry of Permian Coal and Its Combustion Residues in Huainan Coalfield, China

INAA (instrumental neutron activation analysis) was used to determine the contents of trace elements in coal samples from 11 workable Permian coal seams in Huainan coalfield. With XRFS (X-ray fluorescence spectrometry), the geochemical composition of its combustion residues from Tianjiaan Power Plant and Luohe Power Plant was analyzed. In addition, the electron microprobe was employed to study the chemical composition of some fly ashes and bottom ashes. Compared with those of the coals around the world, most trace elements of the Huainan coal are characterized by a normal abundance. Like most coals worldwide, the elements Se, S, As, Sb, Br, U and Cl are enriched in Huainan coal according to dark's value, while the other elements tend to be diluted. The large fluctuation in the contents of trace elements in this kind of coal demonstrates great differences in coal seams. On the other hand, the contents of these elements are very similar in different bottom and fly ash samples. The elements with low organic affinity tend to concentrate in fly and bottom ash than in coal, especially those elements associated with Fe. However, the elements with strong organic affinity tend to be volatile during the combustion. Moreover, the abundance of the elements in fly ash and bottom ash changes with different densities and with different particle sizes. The bottom and fly ashes consist of glass, lime, mullite, coal residues and ferrite minerals. Some residual chars contain higher contents of volatile elements, such as S, P, Cl and As, indicating that the ash containing more residual chars has a strong adsorption of some hazardous elements, suggesting a possible utilization of power plant ash in the field of water cleaning.