Occurrence Of Mercury In Coals Research Articles

Geochemistry of Mercury in the Permian Tectonically Deformed Coals from Peigou Mine, Xinmi Coalfield, China

AbstractAs the mercury emitted from coal combustion can lead to serious environmental issues, researchers pay more attention to the content, distribution and occurrence of mercury in coal. In this paper, the content, distribution, and occurrence of mercury in the Permian tectonically deformed coals from Peigou Mine, Xinmi coalfield, Henan Province were investigated. A total of 18 bench samples were taken from No.2‐1 coals seam in Peigou Mine, including 15 coal bench samples, two roofs and one floor. The mercury concentration, mineral composition, and main inorganic element content of 18 samples were determined by DMA‐80 direct mercury analyzer, XRD, and XRF respectively. The results show that the mercury content ranges from 0.047 ppm to 0.643 ppm, with an average of 0.244 ppm. Though the coal seam has turned into typical tectonically deformed coal by the strong tectonic destruction and plastic deformation, the vertical distribution of mercury has remarkable heterogeneity in coal seam section. By the analysis of correlation between mercury and the main inorganic elements and the mineral composition in coal, we infer that majority of mercury mainly relates to pyrite or kaolinite.

Mercury Removal and Ash Reduction from Coal by an Air Dense Medium Fluidized Bed

ABSTRACTThis study focused on the occurrence of mercury in coal and the effectiveness of mercury and ash removal by an air dense medium fluidized bed (ADMFB). Results of the study revealed that there was a linear correlation between the mercury content, ash content and density of coal. This was attributed to the fact that mercury mainly exists in high density minerals containing elements with a certain affinity for mercury such as silicon, aluminum, iron, titanium, potassium, sodium, chloride, zinc, and magnesium. There is therefore a good correlation between the separation efficiency of ADMFB and the quality of the clean coal, as well as the overall removal of mercury. By optimizing the operating conditions based on the fitting models, clean coal with a mercury content of 0.0841 ppm and a separation efficiency exceeding 99.8% was obtained. The desirability of the separation effect optimized by fitting models was 0.999. Based on these results, it was concluded that ADMFB is an effective way to remove mercury from coal and reduce its ash content.

Mercury in Chinese Coals: Modes of Occurrence and its Removal Statistical Laws during Coal Separation

As one of the dangerous trace elements in coal, mercury has become an advanced research hotspot in coal purification. The content of ash, sulfur, and mercury of raw coals from four high-Hg coal preparation plants located in the main production areas of China was tested. To distinguish the connection between mercury content and the content of ash or sulfur, person correlation analysis and regression correlation analysis were performed by SPSS. The modes of occurrence of mercury in coal samples of these four plants were studied by sequential chemical extraction procedure (SCEP). The laws of mercury removal during coal preparation were researched by analyzing the mercury contents of feedings and products from the four plants. Results showed that mercury in coal was significantly associated with inorganic constituents or sulfur or both of them. The sulfide associated form is the dominant mode of occurrence of mercury in coals. Removal statistical laws of mercury during the process of preparation can be summar...

Studies of the correlation between mercury content and the content of various forms of sulfur in Polish hard coals

Similarities concerning the occurrence of mercury and sulfur in coal are the reasons for studying the correlation between mercury content and the content of the various forms of sulfur such as: total sulfur, pyritic sulfur, sulfate sulfur, and organic sulfur. For this purpose a wide range of different coals and rejects were used. Selected samples differed significantly in the content of ash, mercury, sulfur and its various forms. In the examinations, both steam and coking coals were studied. For coking coals, samples of raw coals, clean coals, middling products and rejects derived from coal preparation plants were examined. To verify the correlation a statistical analysis was performed. The Spearman’s rank correlation coefficient and the correlation coefficients R for polynomial functions of degree 1 and 2 were determined.Based on the obtained results, it can be concluded, that mercury occurs in Polish hard coals both in the organic matter and the inorganic constituents. For the organic matter a significant correlation between the content of mercury and the content of total sulfur and organic sulfur was obtained for subset of examined samples characterized by a relatively low ash yield (clean coals derived from the coal cleaning process). In the case of the inorganic constituents a significant correlation between the content of mercury and the content of pyritic sulfur was obtained for the examined subset of samples characterized by a very high ash yield (rejects derived from the coal cleaning process). An analysis of the subsets of samples derived from individual mines showed that the modes of occurrence of mercury in coal were different for various Polish mines. These differences may be explained by the genetic diversity of coal i.e. various diagenetic, coalification and post-diagenetic conditions, including such phenomena as mineralization that post-dates coal formation and magmatic intrusion, etc.In order to explain the mercury and sulfur behavior in the analyzed processes of coal cleaning the percentage share of those elements in rejects in relation to raw coal was also determined. The mercury removal efficiencies recorded for the cleaning process of Polish hard coals ranged from about 33% to as much as 67%.Results of the statistical analyses did not, however, provide necessary evidence allowing for the formulation of final conclusions regarding the modes of occurrence of mercury in Polish coals, its association with sulfur present in coal as well as proportioning of mercury in the processes of coal cleaning. The results did make it possible, though, to identify the major scientific problems, which, if solved by relevant methods (e.g. XRD, SEM, EPMA), will facilitate the understanding of the Hg-modes of occurrence in various Polish hard coals. The results of the statistical analyses will also make it easier to appropriately select samples in order to explain these scientific problems.

A Comparison of Microwave and Conventional Wet Acid Digestion Method for the Determination of Mercury in Coal and Coal Ash

Mercury in coal and coal ash samples was determined by atomic fluorescence spectrometry after microwave digestion. The validity of the method was studied by spike recovery tests and by analyzing certified reference material. The results obtained for mercury in coal and coal ashes were generally in good agreement with that of the wet digestion method. Moreover, microwave methods generally permitted to reduce considerably the digestion time. Furthermore, the mercury results obtained for coal samples by different acid mixtures microwave method provided valuable information for identifying the modes of occurrence of mercury in coal.

Identifying modes of occurrence of mercury in coal by temperature programmed pyrolysis

Understanding the modes of occurrence of mercury in coal provides information needed to evaluate effectiveness of mercury emission control by pretreatment of coal prior to coal combustion. Two coals of different rank, lignite, and bituminous coal, were investigated to identify the modes of occurrence of mercury in coal by density separation followed by acid extraction procedure and temperature programmed pyrolysis. The bituminous coal was divided into five density fraction between <1.4 and >1.8 g/cm 3 by separation in a heavy-liquid mixture. The density-fractionated fractions were extracted by HNO 3 solution. The treated samples and the lignite were pyrolyzed at a ramp rate of 1 °C/min from room temperature to 660 °C to investigate the mercury release behavior during temperature programmed pyrolysis of coal. The results showed that each mode of occurrence of mercury has its characteristic temperature range for mercury release: Hg 0 at <150 °C, HgCl 2/organic-bound Hg at 150–250 °C, HgS/silicate-bound Hg at 250–400 °C, and pyrite-bound Hg at 400–600 °C. It is inferred that HNO 3 extraction and density separation are effective for the removal of pyrite-bound Hg and then the coal can be pyrolyzed at 400 °C to remove mercury in other forms.

Evaluation of mercury associations in two coals of different rank using physical separation procedures

Mercury is considered to be a toxic metal of major concern, while coal combustion is recognized as one of the main anthropogenic sources of this element. Various processes have been investigated for mercury control in coal-fired utilities. However, until now, no cost-effective or efficient technology has been established for the removal of mercury emissions from coal combustion. For the development of such technologies a deep knowledge of the mode of occurrence and association of mercury compounds in different coals is necessary. Size fractionation, density separation, and oil agglomeration procedures were evaluated in this work not only to assess their efficiency as cleaning methods in mercury removal, but also to determine the associations of mercury with mineral/organic phases. Although the efficiency for mercury removal was found to be generally low, the results obtained provided valuable information for identifying the modes of occurrence of mercury in coal.

00/03037 Modes of occurrence of mercury in coals from Guizhou, China

00/03037 Modes of occurrence of mercury in coals from Guizhou, China

00/00046 Modes of occurrence of mercury in coals from Guizhou, People's Republic of China

In this paper, a primal dual programming model of international coking coal trade is constructed to test for non-competitive market behaviour. World trade in 1996 is simulated under perfect competition and various non-competitive market structures. Statistical tests are used to compare simulated trade flows with actual data. Assuming Cournot-Nash behaviour, an all consumer oligopsony market structure is preferred to alternative models. Under an all consumer oligopsony world coking coal prices and trade are lower than under perfect competition. Under an oligopsonistic structure welfare gains from productivity increases in Australian coal mines might largely accrue to coal buyers.

Modes of occurrence of mercury in coals from Guizhou, People's Republic of China

The modes of occurrence of mercury in coals from Guizhou, P.R. China were investigated using sequential extraction procedures and density separation experiments. The sequential extraction tests were carried out using 32 coals sampled from the Longtan Group of the Permian system in Guizhou Province. Eight coal samples collected from the same area were divided into 10 density fractions between <1.4 and >2.8 g/cm 3 by separation in a heavy-liquid mixture. Combining the results of mineral transformation and of the amount of mercury leached during the leaching experiments with the results of the correlation between mercury and mineral phases and organic matter from density separation experiments, the authors concluded that mercury in the coals examined mainly exists in pyrite. The studies also showed that most of mercury in these coals can be brought into the environment easily by acid mine drainage. It is inferred that a rather large part of Hg in coals from Guizhou may be removed by using conventional coal cleaning techniques.