| Chlorine is somewhat enriched in coal, it is mainly volatilized during the coal combustion process. As an energy source, coal is extensively used in the world. Coal combustion is one of the main sources of chlorine in the atmosphere and is the predominant anthropogenic source. Chlorine is active in O3 and OxHy free radical destruction in the troposphere and, thus, is assumed to play important roles in global climate change. High concentrations of Cl in coal are associated with corrosion problems in boilers. Although chlorine is a common and abundant element in coal, a round-robin study determined that most of the analytical techniques available for its determination were unreliable and irreproducible. The need for an accurate and rapid analytical method of chlorine determination in coal is immediate.Coal is the major fossil fuel used in China, the world's largest coal-mining and-consuming country. Therefore, coal combustion has a significant effect on chlorine emission. However, an extensive and detailed research on chlorine in Chinese coals has not yet been conducted.In this paper, we studied the analytical method of chlorine determination in coal, thereafter, the chlorine content and its distribution in Chinese coals was studied.Based on the study, some conclusions can be drawn:1. A method for the determination of chlorine (Cl) in coal using pyrohydrolysis for sample digestion and ion chromatography (IC) for the further determination was proposed. The pyrohydrolysis conditions specifically for the release of Br from coal were optimized:1.000 g coal sample, a temperature of 1050 0C,25 min of pyrohydrolysis, and 90mLmin-1 of oxygen flux. The released Br was absorbed by 15 mL receiver solution of 7.2mM Na2CO3 and 6.8mM NaHCO3. Chlorine in the analyte was investigated to be Cl" and evaluated by the IC method. The limit of detection and quantification of the proposed method were 0.072μg.g-1 and 0.24μg.g-1, respectively. The accuracy of this approach was confirmed by the analysis of ffour coals spiked with Chinese soil reference materials (SRMs) with an indexed recovery from 93.35 to 108.54%, whose mean value was 98.48%. Six repeated tests were conducted for eight coal samples. A good repeatability was obtained with a relative standard deviation value from 0.18 to 0.69%, averaging 0.41%. The outstanding advantage of this method is shown below:the simplicity of the matrix and little absorption of vessel surface resulting from pyrohydrolysis, which means that there are no interferences during the final halogens determination; the converting entire bromine to bromide in the absorption. The detection limit can be further reduced by increasing the sample weight. With such benefits as simplicity, precision, accuracy and economy, the method can be widely used for routine analysis of Cl in coal and other geochemical samples.2. Chlorine contents in Chinese coals are achieved through a designed nationwide samples collecting and consistently determining by the most effective method i.e. pyrohydrolysis-IC. The contents of chlorine in Chinese coals show logarithm normal frequency distributions. The estimate of the most probable fluorine concentration for Chinese coals can be designated as 237.6 mg/kg.3. The concentration of chlorine versus ash content in 288 coal samples was studied. A weakly negative correlation is inferred from this data.4. The chlorine content decreasing from bituminous coal, through anthracite and lignite, to subbituminous coal.5. Chlorine contents in coal increase from Early Carboniferous, Tertiary, Early Jurassic, Late Jurassic, Middle Jurassic, Late Permian, Early Permian, Late Carboniferous, Late Triassic to Middle Carboniferous.6. Chlorine contents in coal decrease from Permocarboniferous coal-cumulating area in northern China, through Mesozonic-Cenozoic coal-cumulating area in Yunnan Province and Tibet, Early-Middle Jurassic coal-cumulating area in northwestern China and Late Jurassic coal-cumulating area in northeastern China, to Late Permian coal-cumulating area in southern China.
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