Mineral matter identification in some Pakistani coals (original) (raw)
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International Journal of Coal Geology, 2012
The Karmozd and Kiasar mines are two major coal producing areas in the central Alborz coal-bearing field, northern Iran. This study focused on the mineralogy and geochemistry, with respect to the mode of occurrence of elements in feed coals and element partitioning during coal preparation. The low sulfur content in the coal seams indicates a non-marine origin, i.e. deposition in lacustrine and swamp environments. Detrital minerals in the coal seams are quartz, feldspar (albite and orthoclase), mica (muscovite and biotite), amphibole (hornblende), and kaolinite. Authigenic minerals include pyrite, calcite, and chlorite. The contents of most elements are within the general worldwide ranges (with the exceptions of Mn, Co, and Cr, in some coal seams). Correlation coefficients between elements and the ash yield identified four separate groups of elements. The sequential extraction results indicate that Al, Na, K, Zn, Cu, and Co principally occur in the silicates, whereas Pb and Cr mainly occur in the organic fraction. Calcium and Mg display strong affinities to the carbonate phase, while Cd mainly occurs in the water soluble and organic fractions. The calculated removability index shows that the coal cleaning method in Zirab not only removes mineral matter and pyritic sulfur, but also reduces the content of most inorganic elements.
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
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.
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.
This paper presents the extraction of major and trace elements from a coal sample, in deionized water, by using three different extraction techniques. Rotary mixing and ultrasonic extraction were examined for different extraction times, while the microwave-assisted extraction was performed at different tem-Sb and Pb) in solution were determined employing inductively coupled plasma atomic emission spectrometry; whereas the results obtained for Na, K, Ca and Mg were compared employing ion chromatography. Comparing the rotary-and ultrasonic-assisted extractions, it was shown that the former technique was more efficient for the determination of Fe, Na and Pb, whereas the latter one proved more efficient for the determination of Co and Cr ions. Microwave-assisted extraction was shown to be the most efficient method for all the tested elements in coal. In addition, sequential extraction of the elements was realized using microwave digestion. The results of the sequential extraction experiments indicated associations of investigated elements with a mineral phase and organic matrix. Sequential extraction provided information on possible leaching of As, Cd, Co, Cr, Ni, Pb, Fe and Mn under environmental conditions .
Fuel Processing Technology, 2011
This is a very first preliminary investigation on the distribution of heterogeneous nature of mineral matter in one of the industrially important Assam (India) pulverized coal using computer-controlled scanning electron microscopy (CCSEM). The results show that clay minerals, quartz, pyrite, and pyrrhotite form the bulk of the mineral matter. Minor minerals, such as calcite, dolomite, ankerite, barite, oxidized pyrrhotite, and gypsum, are also observed in the sample. The particle size distribution (PSD) of the included minerals is generally observed to be finer than that of the excluded ones in the coal. As a consequence, the coal rich in included minerals has more small mineral particles, which may affect its reactivity. Regarding the association of individual mineral species, the proportion of included to excluded is found to be higher in major cases. With regard to the modes of occurrence of major inorganic elements, it is found that Si mostly occurs as quartz and clay minerals, while Al mostly occurs as silicate minerals. Fe is primarily present as iron sulfides, iron oxide, and Fe-Al-silicate. S is partitioned into iron sulfides and gypsum. Most Ca occurs as carbonates and gypsum, with a minor fraction associated with clay minerals. Mg is mainly present as dolomite and clay minerals, with a very minor fraction present as ankerite. The majority of alkali elements are associated with aluminosilicates. P is mostly associated with kaolinite and/or present as more complex compounds containing Al, Si, and other elements as apatite is found to be absent in the coal studied. Ti is mainly present as rutile and kaolinite.
Energy, Exploration & Exploitation, 2013
The micro-analysis of the inorganic constituents was performed on a tertiary Indian coal sample using computer-controlled scanning electron microscopy (CCSEM). A laboratory combustion experiment of the coal was also carried out to reveal the emission characteristics of particulate matters (PM2.5 and PM10). The results show the presence of major minerals like clay minerals, quartz, pyrite, and pyrrhotite forming the bulk of the mineral matter including some minor minerals, such as calcite, dolomite, ankerite, barite, oxidised pyrrhotite, and gypsum in the sample. The particle size distribution (PSD) of the included minerals is generally observed to be finer than that of the excluded ones in the coal. As a consequence, the coals rich in included minerals have smaller particles, which may affect its reactivity. The ratio of included to excluded minerals is found to be higher in majority of cases. It is found that Si mostly occurs as quartz and clay minerals, while Al mostly occurs as silicate minerals. Fe is primarily present as iron sulfides, iron oxide, and Fe-Al-silicate. S is partitioned into iron sulfides and gypsum. Most Ca occurs as carbonates and gypsum, with a minor fraction associated with clay minerals. Mg is mainly present as dolomite and clay minerals, with a very minor fraction present as ankerite. The majority of alkali elements are associated with aluminosilicates. P is mostly associated with kaolinite and/or present as more complex compounds containing Al, Si, and other elements as apatite is found to be absent in the coal studied. Ti is mainly present as rutile and kaolinite. The PSD of the individual elements were also determined in the coal by CCSEM data and 73.81 % of sulphur was found to be present as included indicating the high organically bound sulphur in the coal. During combustion, concentration of PM10 was found to be higher than PM2.5. The PMs are observed to contain of many potentially hazardous toxic elements viz. Si, Pb, S, Br, As, Cd, F and Cl.
Chemical and physical characterization of mine samples from Lakhra coal field, South Sind, Pakistan
Open-File Report, 1987
Thirty-nine coal samples were collected from operating coal mines in the Lakhra (37 samples) and Meting-Jhimpir (2) coal fields of the South Sind region, Pakistan. The samples represent 29 different coal mines, were obtained from operating faces, and were collected and analyzed in accordance with the standards established by the American Society for Testing and Materials. Statistical appraisal of the analytical results indicates that the bulk of the coal currently being mined in the South Sind region has an apparent rank of subbituminous C with high sulfur (4 percent) and medium ash (15 ,. *' percent) contents. The generalized chemical and physical characteristics on the as-received basis are as follows: moisture, volatile matter, and fixed carbon are each about 28 percent; and heat value is about 7100 Btu/lb. The study is a beginning in valid characterization of the Early Tertiary coals of southern Pakistan. The encouragement and support of E.A. Noble, Resident USGS Advisor in Pakistan, is hereby acknowledged. 'LigA = lignite A, subC = subbituminous C, subB bituminous, hvBb = high volatile B bituminous, hvAb Materials, 1982). I/Includes Kurd-Sho area of NWFP. subbituminous B, subA = subbituminous A, hvCb = high volatile C high volatile A bituminous