Trace Element Content Of Coal Research Articles

Trace elements in world steam coal and their behaviour in Dutch coal-fired power stations: A review

Abstract Trace elements associated with the combustion of coal have received more attention recently, as can be seen from the increasing demands laid down in legislation and permits. Knowledge of the trace element content of coal is essential. Coal used in the Netherlands is imported from all over the world. As a consequence, Dutch power stations are designed to burn a wide range of bituminous coals. The largest share nowadays originates from South Africa, Colombia, and Indonesia, with these three countries accounting for more than 85% of the coal fired in the Netherlands in recent years. The coals, as imported in the Netherlands, have been monitored for their (trace) element content. At present the database contains results of own analyses of about 170 coals, originating from 14 different countries. An important uncertainty was the question of how homogeneous the imported lots are. It appears that the lots as imported from overseas are fairly homogeneous. The behaviour and fate of trace elements in coal-fired power stations has been studied in more than 40 mass balance studies since 1977. More than 50 test series have been completed during co-combustion of biomass and waste materials (up to 40% on mass base) since 1993. It has therefore been possible to establish a relationship between (trace) elements in the fuel and the ash, as well as with emissions into the atmosphere.

Composition and Trace Element Content of Coal in Taiwan

To investigate the trace element contents of local coal, four coal samples were collected from operating mines in NW Taiwan. Detailed petrographic and chemical characterization analyses were then conducted. Analytical results indicate that (1) the samples were high volatile bituminous coal in rank with ash content ranging from 4.2 to 14.4% and with moisture content ranging from 2.7 to 4.6%; (2) the macerals were mostly composed of vitrinite with vitrinite reflectance less than 0.8%; (3) the sample of Wukeng mine has the highest Fe2O3 (29.5%), TI (54.8 ppm), Zn (140 ppm), and As (697 ppm) contents in ash and Hg (2.3 ppm) in the coal. If used properly, these coals should not present health hazards.

Environmental aspects of trace elements in coal combustion

During coal formation, many trace elements are accumulated with respect to mean crust and mean soil, which may impose environmental hazards in coal combustion. This review tries to combine available data from chemical technology, geochemistry and analytical chemistry in order to overlook the fate of trace elements in the coal combustion process and their pathways to various ash fractions. Volatilization techniques which have been used in microchemistry for several decades to achieve decomposition and separation from main elements of the crust simultaneously, are briefly outlined. A compilation of data of trace element contents of coals, coal ashes and slags is given, as well as tables of boiling points, to indicate possible volatilization reactions in reducing, oxidizing, or halogenide containing gas streams. Particle size and depletion temperature influence the composition of ash. Data from selective leaching of coal and coal ash help to estimate environmental impacts as well as to stimulate strategies for future regain of valuable trace elements. Magnetometric profiling is suggested as a new tool to detect accumulations of particles emitted by combustion processes into the environment, in order to find suitable sites for immission sampling.

97/02356 Investigation of the behavior of potentially hazardous trace elements in Kentucky coals and combustion byproducts

The minor- and trace-element content of coal is of great interest because of the potentially hazardous impact on human health and the environment resulting from their release during coal combustion. Of the one billion tons of coal mined annually in the United States, 85-90% is consumed by coal-fired power plants. Potentially toxic elements present at concentrations as low as a few egg can be released in large quantities from combustion of this magnitude. Of special concern are those trace elements that occur naturally in coal which have been designated as potential hazardous air pollutants (HAPs) in the 1990 Amendments to the Clean Air Act. The principle objective of this work was to investigate a combination of physical and chemical coal cleaning techniques to remove 90 percent of HAP trace elements at 90 percent combustibles recovery from Kentucky No. 9 coal. Samples of this coal were first subjected to physical separation by flotation in a Denver cell. The float fraction from the Denver cell was then used as feed material for hydrothermal leaching tests in which the efficacy of dilute alkali (NaOH) and acid (HNO{sub 3}) solutions at various temperatures and pressures was investigated. The combined column flotation and mild chemical more » cleaning strategy removed 60-80% of trace elements with greater than 85, recovery of combustibles from very finely ground (-325 mesh) coal. The elemental composition of the samples generated at each stage was determined using particle induced X-ray emission (PIXE) analysis. PIXE is a rapid, instrumental technique that, in principle, is capable of analyzing all elements from sodium through uranium with sensitivities as low as 1 {mu}g/g. « less

Selected elements in major minerals from bituminous coal as determined by INAA: implications for removing environmentally sensitive elements from coal

The four most abundant minerals generally found in Euramerican bituminous coals are quartz, kaolinite, illite and pyrite. These four minerals were isolated by density separation and handpicking from bituminous coal samples collected in the Ruhr Basin, Germany and the Appalachian basin, U.S.A. Trace-element concentrations of relatively pure (∼ 99 +%) separates of major minerals from these coals were determined directly by using instrumental neutron activation analysis (INAA). As expected, quartz contributes little to the trace-element mass balance. Illite generally has higher trace-element concentrations than kaolinite, but, for the concentrates analyzed in this study, Hf, Ta, W, Th and U are in lower concentrations in illite than in kaolinite. Pyrite has higher concentrations of chalcophile elements (e.g., As and Se) and is considerably lower in lithophile elements as compared to kaolinite and illite. Our study provides a direct and sensitive method of determining trace-element relationships with minerals in coal. Mass-balance calculations suggest that the trace-element content of coal can be explained mainly by three major minerals: pyrite, kaolinite and illite. This conclusion indicates that the size and textural relationships of these major coal minerals may be a more important consideration as to whether coal cleaning can effectively remove the most environmentally sensitive trace elements in coal than what trace minerals are present.

96/03306 - Potentially hazardous trace elements in Kentucky coals

The minor and trace element content of coal is of great interest because of the potential environmental impact resulting from their release during coal combustion. Results will be presented from the investigation of how trace elements in western and eastern Kentucky bituminous coals partition (1) in advanced cleaning techniques prior to combustion and (2) in the solid waste streams during coal combustion. For the coal cleaning studies, samples of run-of-mine coal were subjected to a commercially available laboratory scale column floatation process followed by various hydrothermal leaching treatments. For the combustion studies, samples of feed coal, bottom ash, and fly ash were collected from single source western and eastern Kentucky coal fired powered plants. The trace element composition of coal and coal byproducts were obtained using particle induced x-ray emission (PIXE) and instrumental neutron activation analysis (INAA). Modes of occurrence for some of the elements were determined using x-ray absorption fine structure (XAFS) spectroscopy to augment the compositional data.

Distribution of major, minor and trace elements in Hat Creek Deposit No. 2, British Columbia, Canada

The major-, minor- and trace-element contents of coals from Hat Creek No. 2 deposit, British Columbia, are determined using INAA and inductively coupled plasma emission spectrometry (boron only). Al, Cr, Fe, Mn and Na were found to be inorganically bound in the coal while As, B and S are associated with the organic fraction of the coal. The rare-earth element concentrations in the coal are variable, however, the LREE/HREE ratio decreases from base to the top of the deposits. Many elements show little variation in concentration with depth; however, the gradual increase of As and S with depth appears to be rank related and indicative of progressive decrease in porosity with increasing rank. Concentrations of B and Cr are sensitive to the environment of coal deposition, with coal deposited in a freshwater environment (Hat Creek No. 2 deposit), having low B and high Cr compared with more brackish coals.

Trace-Element Content of Bituminous Coal from Appalachian and Eastern Interior Regions and Rocky Mountain Coal Province--Data as of 1979: ABSTRACT

We have studied 2,035 samples from the Appalachian bituminous coal beds, 370 samples from the eastern interior coal beds, and 362 samples from the Rocky Mountain coal beds. The coals analyzed range in rank from high-volatile bituminous to low-volatile bituminous; the Appalachian coals have the lowest mean volatile-matter and moisture contents and the highest fixed-carbon content and Btu value. The Rocky Mountain coals have the highest mean ash content and lowest fixed-carbon content and Btu value. The average Appalachian coal has a much higher rank than does coal from either of the other regions. Of the 19 elements reported, seven (Cu, F, Mn, Pb, Sb, U, and V) have mean values that vary less than twofold among the three areas. Of these, U is the most uniformly distributed. Other elements (Co, Ni, Zn, and S) have about a fourfold variation, whereas As is 6.5 times as abundant in Appalachian coal as in Rocky Mountain coal. In average, the other elements are 2 to 6.5 times as abundant in some coals from the three areas Table as in others. The Rocky Mountain coals have the lowest mean contents of 15 of the elements listed in the table; only U and F mean contents are slightly higher in this area. The eastern interior coals have the highest mean contents of nine of the elements, and the Appalachian coals have the highest mean contents of eight of the elements. As the average rank of the coals increases, the average contents of As, Co, Cr, Cu, Hg, Se, and V also increase; however, the distribution of most other elements is not related to rank. In general, the trace-element content of coal is influenced largely by the depositional environment and does not depend on rank. End_of_Article - Last_Page 761------------

Differential thermal and thermogravimetric studies and some trace-element contents of some coals and carbonaceous shales from west-central Sinai, Egypt

DTA, modified DTA, thermogravimetric and spectrochemical analyses were performed on twelve samples of Carboniferous carbonaceous shales and coals and two samples of vitrain (separated from the carbonaceous shale or coal) in west-central Sinai. The analyses indicate that these coals and carbonaceous shales belong to the high-volatile sub-bituminous A coal-rank. Trace-element contents for Pb, Zn, Ga, B, Mn, Ge, Ni, V, Cr, Cu and U are given and averaged. These are then compared with the averages for the only published trace-element contents of the nearby Jurassic Ayun Musa coals. They are found to be richer in Pb, Zn and Ga. Ge is remarkably concentrated in the vitrain bands and seamlets inside the Carboniferous Sinai host-coals while V, Zn and Pb and, to a lesser extent, Mn, Cr and U are depleted in vitrains relative to their host-rocks.

Determination of Sulfur, Ash, and trace Element Content of Coal, Coke, and Fly Using Multielement Tube-Excied X-ray Fluorescence Analsis

A procedure using tube excited energy dispersive x-ray fluorescence analysis with interelement corrections has been developed for multielement analysis of major and trace elements and ash content of coal, coke, and fly ash. The procedure uses pressed pellets and an exponential correction for interelement effects. The average deviations ranged from about 0.0003% for V at an average concentration of about .003% to 0.1% for S at an average concentration of 4%. About 25 elements were measured and 100 second minimum detectable concentrations ranged from about one part per million for elements near arsenic to about one tenth of one percent for sodium.