Distribution, modes of occurrence, and main factors influencing lead enrichment in Chinese coals

Lead is a potentially harmful element that has caused serious environmental pollution during its mining and use along with serious human health problems.This study assessed lead in Chinese coals based on published literature,with a particular focus on data reported since 2004.The analysis included 9447 individual samples from 103 coalfields or mines in 28 provinces in China.The arithmetic mean content of lead in the studied coals was 15.0μg/g.Considering the coal reserves,the weighted-average lead concentration in Chinese coals was calculated to be 19.6μg/g.Lead was significantly enriched in the coals from Henan Province and enriched in the coals from the Tibet Autonomous Region.The coals from Tibet–Western Yunnan and the southern areas of China had elevated lead concentrations.Sulfides are the primary hosts of lead in Chinese coals,although other hosts include silicates,organic matter,carbonates,and other minerals.Source rocks in the sediment-source region and marine environments may be the most significant factors contributing to lead enrichment in Chinese coals.Hydrothermal fluids and peat-forming plants also contribute to lead enrichment in some Chinese coals.

Distributions of rare-earth elements in two Chinese coals and their burnt products

The concentrations of two fresh Chinese coals (lignitie and fatty coal ) from dif-ferent geological origin and the corresponding fly and bottom ashes were determined us-ing inductively coupled plasma mass spectrometry(ICP-MS). The ranges and means of concentrations of these elemennts were given. Based on the combustion simulating ex-periment in the one-dismensional boiler, the contents of REE (rare-earth element) of 18 samples in lignite, fatty coal and their fly and bottom ashes in different combustion condi-tion were determined, and geochemical feature of REE were analyzed.

Ultimate Composition of Main Chinese Power Coals

Calculations and analyses are made for the ultimate composition of 158 Chinese power coals. The results reveal that the carbon content on as received basis, Cr, increases linearly with the increase of the low heating value Qnot,a, on as received basis; the hydrogen content on as received basis, Hr, first increases with the increase of the volatile content on dry ash free basis Vdaf （Vdaf 〈 33.0%） and then decreases （Vdaf 〉 33.0%）; the oxygen content on as received basis, Oar, increases linearly with the increase of Vau, ranging between 2.0% and 12.5%. By comparison, the nitrogen content on as received basis N of bituminous and lean coal is higher, while the sulfur content on as received basis Sar Of anthracite is higher than bituminous coal, lean coal and lignite. The hydrogen on as received basis Hr is important for the conversion between low heating value and high heating value on as received basis for Chinese power coals, and Sr is important for the calculation of high heating value from the oxygen bomb heat value for Chinese power coals.

STUDY ON THE INFLUENCE OF WETTING HEAT ON COAL SLURRYABILITY

Wetting Heat of various ranks of coals in water was measured by using SETARAM C80D Calorimeter. The data were correlated to coals' slurryability which is characterized by the solid load at the viscosity of 1 Pa's and 25℃. The results showed that the heat of wetting by wa-ter decreases as coal rank increases in the range of brawn coal to bituminous coaI with carbon content of 89% ~90% (daf), and then, increases a little for anthracite. This trend fitted well to the relationship of slurryability to coal rank. The heat of wetting was also correlated to the inher-ent moisture content and the oxygen content of coal, which are commonly considered as slurrya-bility indication parameters. Hence, the wetting heat is another measure of coal's slurryability.

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.

Construction of a macromolecular structural model of Chinese lignite and analysis of its low-temperature oxidation behavior

The aim of this paper is to analyze the change in the active structure of lignite during the process of lowtemperature oxidation by constructing a molecular structure model for lignite. Using quantum computation combined with experimental results of proximate analysis, ultimate analysis, Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS), a structural model for the large molecular structure was constructed. By analyzing the bond lengths in the model molecule, the evolution law for the active structure of lignite was predicted for the process of low-temperature oxidation. In low-temperature oxidation,alkanes and hydroxyls are the primary active structures observed in lignite, though ether may also react. These active functional groups react with oxygen to release heat, thereby speeding up the reaction between coal and oxygen. Finally, the content of various functional groups in the process of lignite low-temperature oxidation was analyzed by infrared analysis, and the accuracy of the model was verified.