煤燃烧中外在矿物质转化机理及动力学参数计算

Excluded Mineral Matter Transformation Mechanism and Kinetics During Coal Combustion

应用热重实验和热分析动力学研究了煤中3种典型矿物质的转化机理，采用MasterPlot法推断反应的最概然机理函数，由Coats-Redfem法计算了其反应的动力学参数．实验和计算结果显示：高岭石在700—900K时发生脱水反应，生成偏高岭石，其反应机理为成核与生长，反应的活化能为86kJ／mol；随后，偏高岭石在1100K左右开始转变为莫来石．方解石在1000-1200K发生分解反应，生成氧化钙，其反应机理为成核与生长，反应的活化能为170kJ／mol．黄铁矿先在700-800K时发生分解反应，生成磁黄铁矿，其反应机理为三维扩散，反应的活化能为210kJ／mol；随后，磁黄铁矿在约900-1000K时发生氧化反应，生成磁铁矿，其反应机理为成核与生长，反应的活化能为147kJ／mol．

The transformation mechanism of three typical excluded mineral kaolinite, calcite and pyrite are investigated by thermal analysis kinetics. Firstly, the thermogravimetry experiment is conducted, and then the most probable kinetic function is obtained using Master Hot method. Finally, the kinetics data of reaction is calculated by using data from thermogravimetry, the improved Coats-Redfem method. The experimental and calculation results indicate that, the decomposition of kaolinite occurs at 700-900 K due to release of water, leading to the formation of metakaolinite. Its reaction mechanism is nuclear producing and growing process and it active energy value is 86 kJ/mol. Subsequently, at around 1 100 K metakaolinite converts to mullite. The decomposition of calcite happen at 1 000--1200 K, which leads to the release of carbon dioxide and formation of calcium oxide. Its reaction mechanism is nuclear producing and growing process and its active energy value is 170 kJ/mol. The reaction of pyrite takes place in two steps. In the first step, pyrrhotite is produced at 700-800 K. Its reaction mechanism is three-dimensional diffusion and its active energy value is 210 kJ/mol; later, the oxidation reaction of pyrrhotite occurs at 900-1 000 K and magnetite is produced. Its reaction mechanism is nuclear producing and growing process and its active energy value is 147 kJ/mol.