固阳褐铁矿脱水反应动力学研究

Study on the Dehydration Reaction Kinetics of Guyang Limonite

利用热分析TG-DTA技术和X射线衍射技术对固阳褐铁矿脱水过程反应机制进行了研究。结合不同动力学机理模型对热分析数据进行了处理及相关性分析,确定了褐铁矿的脱水反应机制,采用CoatRedfern积分法计算了脱水反应动力学参数。结果表明:固阳褐铁矿脱水反应过程分为两个阶段,第一阶段:140~320℃,失重率为4.78%,反应活化能E=28.54 k J/mol,反应机理符合Avrami-Erofeev方程,为随机成核和随后生长的一级化学反应;第二阶段:320~465℃,失重率为3.84%,反应活化能E=61.92 k J/mol,反应机理符合二级反应函数,为化学反应控制。XRD结果表明,随着温度的不断升高,褐铁矿在200℃时发生了物相转变,针铁矿的衍射峰不断减弱、消失,而赤铁矿的衍射峰逐渐增强,矿相变纯。

The reaction mechanism of dehydration process of Guyang limonite was studied by TG-DTA and X-ray diffraction.The thermal analysis data were processed and analyzed by the liner correlation calculation with different dynamic mechanism models.The dehydration reaction mechanism was determined,meanwhile,the kinetic parameters of dehydration reaction were calculated by Coat-Redfern integral method.The results showed that the dehydration reaction process of Guyang limonite is divided into two stages.The first stage is at140~320℃with a weight loss rate of4.78%and a reaction activation energy of28.54kJ/mol.The reaction mechanism of the first stage is in accordance with Avrami-Erofeev equation,which belongs to the stoichiometric and subsequent growth of the primary chemical reaction.While the second stage is at320~465℃with a weight loss rate of3.84%and a reaction activation energy of61.92kJ/mol.The reaction mechanism of the second stage agrees with the secondary reaction function,and it is controlled by chemical reactions.XRD results showed that the phase transition of limonite occurs at200℃with increasing temperature,during which the diffraction peaks of goethite are weakening and disappearing,but the diffraction peaks of hematite gradually increase.As a result,the mineral phases become pure.