Evolution Of Migration Behavior Of Fluorine In Coal And Sulfur-Containing Coal Molecular Structure

Coal is the mainly energy source in China, huge amount of coal utilization has caused serious pollution to the environment. Especially, for the emission of fluorine and sulfur which have caused damage to human health, and gradually concerned by people. Fluorine of halogen is one of the hazardous elements in coal, the transformations of fluorine during coal combustion are responsible to the safe utilization and pollutant emission. This thesis provided an overview of the present research on the determination methods of fluorine, the occurrence characteristics, the mechanism, behavior of fluoride during coal combustion, emission control method and Coal Molecular structural model. In this work, we focused on studying determination methods of fluorine in coal, the occurrence characteristics of Guizhou coa, the mechanism, behavior of fluoride during coal combustion, the migration behavior and washability of fluorine in guizhou coal during cleaning process and Containing-sulfur Coal Molecular structural model was constructed based on several structure parameters derived from XPS, FTIR and ¹³CNMR, which were processed by curve-fitting and curve-resolved. The minimum-energy conformation of Guizhou coal macromolecules was calculated by molecular mechanics calculation and molecular dynamics simulation. The key findings of this dissertation are as follows:Fluorine content in coal was determined by high temperature combustion hydrolyzing-ion chromatograpy method. The impact factors during the process of measuring were analyzed, the measurement accuracy of this method was evaluated, and this method was compared with the ion selective electrode for the fluoride content in coal. High temperature combustion hydrolyzing--ion chromatograpy method can determine the fluoride content in coal with advantanges of rapid, sensitive, convenient, accurate, non-interference, etc.. It was an effective method to measure fluoride content in coal and other complex minerals; Compared with ion-selective electrode method, ion chromatography method had good stability, small interference received, faster and more convenient; the average fluorine content in Guizhou coal 715.20 mg/kg, which is much higher than the average fluorine content of China and world average. Most Guizhou coal was high-fluorine-coal, in the case of direct combustion use, it can cause great harm to the environment and human health.The correlation between fluorine and coalification degree, sulfur, chlorine, phosphor and alkali metals in Guizhou coals has been analyzed. The low-temperature ashing experiment was carried out. The fluorine concentration is independent of coal rank; and the fluorine concentration also depends on the kinds of fluorine-bearing minerals and their contents; There is no correlation between fluorine and chlorine; Fluorine is positively correlated with organic sulfur, phosphor and alkali metals. The inorganic occurrence is the primary mode of occurrence of fluorine in coals from Guizhou province.Thermogravimetric analyzer and portable infrared gas analyzer were employed to study the reaction characteristics and the law of release during the process of combustion of Guizhou coal. the reaction kinetic parameters of Guizhou coal simples were calculated, the release process of fluoride in Guizhou coal was analyzed as well. Reaction kinetics model of fluoride release during the process of coal combustion, The reaction activation energy was calculated through isothermal release experiment of fluoride in coal. The following conclusions were obtained: under oxygen atmosphere, the activation energy at the range of low temperature was lower than that at the range of high temperature; fluoride release was divided into three sections during coal combustion, precipitation of free and adsorptive fluoride in moisture at the temperature of 150～200℃, large release of fluoride caused by fluorine-containing mineral reactions involved in combustion of coal at about 600～950℃, and after 1100℃, the mineral such as fluorapatite occurred pyrolysis at condition of high temperature; the release process of fluoride during coal combustion can be described with a one-level reaction kinetics model, the reaction activation energy E and frequency factor A depend on the mode of occurrence of fluoride in coal and the thermal stability of fluoride; The results have very important guiding significance for analysis and understanding of precipitation characteristics of fluoride under different ways, the correct evaluation for fluoride pollution and taking reasonable and effective measures to control fluoride pollution, etc.The removal of fluorine in the Guizhou coal was explored by the washing experiment. A systematic analysis of migration behavior and washability of fluorine in Guizhou coal during cleaning process were conducted, and the washability and removal efficiency of fluoride of 11 Guizhou coal samples were cakculated. The results showed that only when the ash and fluoride contents are not high, the fluorine in Guizhou coals can be removal effective by flotation.Containing-sulfur coal molecular structural model was constructed based on several structure parameters derived from XPS, FTIR and ¹³CNMR, which were processed by curve-fitting and curve-resolved. The minimum-energy conformation of Guizhou coal macromolecules was calculated by molecular mechanics calculation and molecular dynamics simulation.In summary, the determination methods of fluorine, occurrence characteristics, behavior of fluoride during coal combustion and migration behavior and washability of fluorine in Guizhou coal during cleaning process were studied; The containing-sulfur coal molecular structural model was constructed. This work is helpful for the rational utilization of Guizhou coal and the development of effective pollution emission control technology.