微波场中生物炭还原褐铁矿反应动力学实验及模型计算

采用微波失重在线检测装置和XRD分别分析了褐铁矿与生物炭升温至923 K的失重变化及微波焙烧前后的矿相变化；同时基于褐铁矿微波还原焙烧升温失重曲线，采用Achar-Brindley-Sharp-Wendworth微分法和Coats-Redfern积分法，计算了褐铁矿在不同温度段的反应动力学参数. 结果表明，褐铁矿与生物炭在923 K的还原温度下转变为磁铁矿，同时生成少量的硅酸亚铁(Fe2SiO4)；其微波还原焙烧过程分为3个阶段进行，在366~470 K，反应的表观活化能(E1)分别为30.7和26.3 kJ/mol，反应机理符合反应级数函数，属于化学反应控制；在470~650 K，表观活化能(E2)分别为40.3和33.1 kJ/mol，反应机理符合Avrami-Erofeer函数，是随机成核和随后生长的化学反应控制；在650~825 K，表观活化能(E3)分别为52.4 和52.9 kJ/mol，反应机理符合Zhuralev-Lesokin-Tempelman函数，属于三维扩散控制.

Kinetic Experiment and Modelling of Reduction Reaction of Limonite with Biochar in Microwave Field

The changes of weight loss and mineral phase of limonite with biochar before and after microwave roasting were measured at 923 K. Based on the curves of rising temperature and weight loss of reduction roasting by microwave heating, the reaction kinetics parameters of limonite in different temperature periods were calculated by Achar-Brindley-Sharp-Wendworth differentiation method and Coats-Redfern integration method. The results showed that the limonite reduced by biochar changed into magnetite at 923 K, and produced little ferrous silicate (Fe2SiO4) in roasted ore. And the reduction roasting process of limonite with biochar by microwave heating was divided into three temperature stages. The apparent activation energy (E1) was 30.7 and 26.3 kJ/mol in 366~470 K respectively, and the reaction mechanism accorded with reaction order function, belonging to the chemical reaction control. In 470~650 K, the apparent activation energy (E2) was 40.3 and 33.1 kJ/mol respectively, the reaction mechanism accorded with Avrami-Erofeev function, belonging to the chemical reaction control of stochastic coring and afterward growing up. But in 650 ~825 K, the apparent activation energy (E3) was 52.4 and 52.9 kJ/mol respectively, and the reaction mechanism accorded with Zhuralev-Lesokin-Tempelman function, belonging to the three-dimensional diffusion control.