Enrichment and distribution of trace elements in Padhrar, Thar and Kotli coals from Pakistan: Comparison to coals from China with an emphasis on the elements distribution (original) (raw)
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Mineral matter identification in some Pakistani coals
Fuel Processing Technology, 2002
Extractions of some of the inorganic elements from Pakistani coal samples were made with ammonium acetate, HCl, HNO3, and acid mixture. The various extracts and the residues were analyzed for the inorganic elements like Cu, Zn, Mn, Fe, Ca, Mg, K and Na. Even though ammonium acetate and acids extracted a considerable amount of inorganic elements, complete demineralization was not achieved. These elements are present both in the form of ion exchangeable cations (extractable with ammonium acetate) and as part of discrete-mineral particles (extractable with acids).
Composition, Trace Element Contents and Major Ash Constituents of Thar Coal, Pakistan
2010
Thar coalfield is a part of the Thar Desert of Pakistan. Pakistan has coal reserves of 185 billion tons, of this Thar coal reserves account for 175 billion tons spread over a single geographically contained area of 9100 sq km in the south eastern part of the Sindh. It is bounded in the north, east and south by India, in the west by the irrigated Indus river flood plain. The terrain is sandy and rough with sand dunes forming the topography. Various physio-chemical parameters including chemical composition of coal ashes, distribution of trace elements in them, were analyzed to understand the coal prospects and its share in the domestic energy production. In addition a preliminary study have also undertaken on the factors that effect the chemical composition of coal ashes. The apparent rank is high volatile Lignite "B" coal. Arithmetic mean values for proximate analysis of coals (as received basis; n=54) show these coals to be 6.83% Ash, 29.55% volatile matter, 19.2% fixed carbon and 44.3% moisture and have a heat of combustion of 6094 BTU/lb. Average values for ultimate analysis of the coal show these coals to be 4.96% hydrogen, 51.18% carbon, 0.31% nitrogen, 2.45% sulphur and 14.88% oxygen. The geometric mean values of these, as viewed from the analysis of coal ash samples collected from the Thar coal field region, it can be seen that coal ashes from region studied are composed of organic matter and the major chemicals are SiO 2 , Al 2 O 3 , Fe 2 O 3 and CaO as well as minor amounts of SO 3 ,P 2 O 5 , Na 2 O, K 2 O and TiO 2 . During the combustions of coal, its trace elements will be redistributed and most of them are enriched in coal ashes.The mineralogy of Sindh coal samples suggests that these coals have quartz and Kaolinite as the dominant phase and minor amount of calcite, Illite and Muuscovite. The dominant minerals of Thar coals are Composition, Trace Element Contents and Major Ash Constituents of Thar Coal, Pakistan 93 quartz. Quartz also tends to occur in the form of comparatively large particles of free mineral matter, whereas much of the pyrite is dispersed in the coal substances and clay sediments.
International Journal of Coal Geology
The ash yield and concentrations of twenty-four minor and trace elements, including twelve potentially hazardous trace elements were determined in Mukah coal from Sarawak, Malaysia. Comparisons made to the Clarke values show that Mukah coal is depleted in Ag, Ba, Be, Cd, Co, Mn, Ni, Se, U, and V. On the other hand, it is enriched in As, Cr, Cu, Pb, Sb, Th, and Zn. Among the trace elements studied, V and Ba are associated predominantly with the clay minerals. Manganese, Cr, Cu, Th, and Ni are mostly bound within the aluminosilicate, sulphide and/or carbonate minerals in varying proportions, though a portion of these elements are also organically bound. Arsenic, Pb and Sb are mostly organically bound, though some of these elements are also associated with the sulphide minerals. Zinc is associated with both the organic and inorganic contents of the coal. Among the potentially hazardous trace elements, Be, Cd, Co, Mn, Ni, Se, and U may be of little or no health and environmental concerns, whereas As, Cr, Pb, Sb and Th require further examination for their potential health and environmental concerns. Of particular concern are the elements As, Pb and Sb, which are mostly organically bound and hence cannot be removed by physical cleaning technologies. They escape during coal combustion, either released as vapours to the atmosphere or are adsorbed onto the fine fly ash particles.
Concentration and distribution of trace elements in some coals from Northern China
International Journal of Coal Geology, 2007
The aims of this study were to determine the concentration and identify the distribution of existent trace elements in dental enamel from whole sections of dental organs. In this study the distribution of trace elements was analyzed considering three main areas: the surfaces near the dentin-enamel junction and the external and intermediate surfaces. Seventeen location points were studied in the enamel tissue through scanning electron microscopy. Qualitative and quantitative analysis of chemical elements were performed by spectral dispersive X-ray energy. The results of the present study indicate the presence of thirteen trace elements (Al, Sn, Sb, I, Si, Yb, Ba, K, Br, Sr, Sc, In, S), their distribution and concentration models are presented here and different anatomical distributions in the crown of the dental organ are shown. In conclusion, with the energy dispersive spectral X-ray analysis, different element distributions and concentrations of trace elements were identified in the thickness of the dental enamel.
The present study probed the quantity of critical elements and minerals in Akkakhel, Akhorwal, and Sheikhan coal deposits located in Kohat, Pakistan. For this purpose, thirteen coalmines were sampled for the determination of critical elements and minerals in coal. The results showed that the critical elements in the coal namely, magnesium (Mg), calcium (Ca), potassium (K), iron (Fe), sodium (Na), silver (Ag), manganese (Mn), cobalt (Co), nickel (Ni), cadmium (Cd), chromium (Cr), copper (Cu), zinc (Zn), sulfur (S), and lead (Pb) were relatively higher than the world's coal and upper continental crust. The higher concentration of critical elements is attributed to the spinel group, sulfides, carbonates, and clay minerals. In all the coalfields, quartz and pyrite minerals' existence and mode of occurrence were common in Akkakhel, Akhorwal, and Sheikhan coalmines. The minerals namely, anatase, gibbsite, calcite, periclase, and palygorskite minerals were common in Akhorwal and Sheikhan coalmines. The critical elements were associated with montmorillonite, potassium sulfide, sillimanite, hematite, chalcopyrite, illite, goldichite, spinel, phengite, sphalerite, dolomite, ilmenite, and siderite minerals. Moreover, the identification of mineral phases through SEM and XRD analysis results in the reduction of sulfur to a considerable level through the froth flotation technique, which limits the SOx emission to the atmosphere. The data obtained during this study will be useful for the industries such as energy, power, space technology, and cement manufacturing. However, sustainable mining, extraction of minerals, and utilization of mining wastes will limit the negative impacts on the environment.
International Journal of Coal Geology
China will continue to be one of the largest coal producers and users in the world. The high volume of coal use in China has focused attention on the amounts of toxic trace elements released from coal combustions and also the valuable trace elements extracted or potentially utilized from coal ash. Compared to world coals, Chinese coals have normal background values for most trace elements, with the exception of higher Li (31.8 μg/g), Zr (89.5 μg/g), Nb (9.44 μg/g), Ta (0.62 μg/g), Hf (3.71 μg/g), Th (5.84 μg/g), and rare earth elements (∑La-Lu + Y, 136 μg/g). This is not only due to the higher ash yields of Chinese coals but also to alkali volcanic ashes found in some southwestern coals. The background values of toxic elements of Hg (0.163 μg/g), As (3.79 μg/g), and F (130 μg/g) in Chinese coals are comparable to coals from most other countries. The genetic types for trace-element enrichment of Chinese coals include source-rock-controlled, marineenvironment-controlled, hydrothermal-fluid-controlled (including magmatic-, low-temperature-hydrothermalfluid-, and submarine-exhalation-controlled subtypes), groundwater-controlled, and volcanic-ash-controlled.
International Journal of Coal Geology, 2005
The concentration of trace elements and their distribution in the late Permian coal in the Heshan coal field, Guangxi Autonomous Region, were analysed in this paper. The late Permian coal of the Heshan mining district was developed in a low energy and shallow, confined carbonate platform. Heshan coal is a low volatile bituminous coal characterized by a high sulphur content, ranging between 2.0% and 8.2%. Compared with the worldwide average content of the trace elements in coal, the content of some trace element in the study coal is markedly high (Bi, Nb and Sc).
Geochemistry of trace elements in coals from the Zhuji Mine, Huainan Coalfield, Anhui, China
International Journal of Coal Geology, 2010
The abundances of nine major elements and thirty-eight trace elements in 520 samples of low sulfur coals from the Zhuji Mine, Huainan Coalfield, Anhui, China, were determined. Samples were mainly collected from 10 minable coal seams of 29 boreholes during exploration. The B content in coals shows that the influence of brackish water decreased toward the top of coal seams; marine transgression and regression occurred frequently in the Lower Shihezi Formation. A wide range of elemental abundances is found. Weighted means of Na, K, Fe, P, Be, B, Co, Ni, Cr, Se, Sb, Ba, and Bi abundances in Zhuji coals are higher, and the remainder elements are either lower or equal to the average values of elements in coals of northern China. Compared to the Chinese coals, the Zhuji coals are higher in Na, K, Be, B, Cr, Co, Se, Sn, Sb, and Bi, but lower in Ti, P, Li, V and Zn. The Zhuji coals are lower only in S, P, V and Zn than average U.S. and world coals. Potassium, Mg, Ca, Mn, Sr, As, Se, Sb and light rare earth elements (LREE) had a tendency to be enriched in thicker coal seams, whereas Fe, Ti, P, V, Co, Ni, Y, Mo, Pb and heavy rare earth elements (HREE) were inclined to concentrate in thinner coal seams. The enrichment of some elements in the Shanxi or Upper Shihezi Formations is related to their depositional environments. The elements are classified into three groups based on their stratigraphic distributions from coal seams 3 to 11-2, and the characteristics of each group are discussed. Lateral distributions of selected elements are also investigated. The correlation coefficients of elemental abundances with ash content show that the elements may be classified into four groups related to modes of occurrence of these elements.