氧化铁微粉气相还原过程的动力学模拟

Kinetic Simulation for Gas Reduction Process of Iron Oxide in Microscale

考虑到微小尺度下化学反应的热效应，提出了一维传热、传质与化学反应的耦合模型对氢气还原氧化铁微粉过程中的动力学行为进行了模拟．采用全隐式有限容积法对偏微分方程组作数值求解，得到不同温度、气体初始浓度和矿粉粒径条件下矿粉的还原率，模拟结果与文献中的实验结果基本吻合．模拟结果给出了气体在固相内的扩散分布行为，及不同条件下完全还原氧化铁微粉所需要的时间，根据气体在反应过程中的扩散行为，可知气体内扩散对微细氧化铁粉气相还原速率起重要作用．粒径为200～300μm的微粒完全还原所需时间在450～1400s之间．

Considering the heat effect of chemical reaction in microscale, a model coupling heat and mass transfer with chemical reaction was developed to simulate the kinetic behavior of fine ferrous oxide. Finite Volume Method （FEM）with fully implicit technique were applied for solving the governing parabolic equations. The reduction degrees of fine iron oxide at different conditions of temperature, initial gas concentration and particle size were calculated with the model. The model was validated by comparing with experimental results in the literature. The gas concentration profile developing inside the ferrous oxide particle and the time of complete reduction were given. Simulation results show that the diffusion of gas inside the particle influences the reduction rate extremely, and that the time for full reduction of iron oxide with particle size of 200-300μm is from 450 s to 1 400 s.