浅析Fick定律描述CO+H2混合气体还原铁矿物内扩散环节的偏差  

A preliminary analysis of deviations arising from description of the internal diffusion step by Fick’s Law in iron ore reduction with CO and H2 gas mixtures

作　　者：张京[1] 孟繁超 邵磊 邹宗树 Zhang Jing;Meng Fanchao;Shao Lei;Zou Zongshu(College of Sciences, Northeastern University, Shenyang 110819, China;School of Metallurgy, Northeastern University, Shenyang 110819, China)

机构地区：[1]东北大学理学院,沈阳110819 [2]东北大学冶金学院,沈阳110819

出　　处：《材料与冶金学报》2019年第3期169-174,共6页Journal of Materials and Metallurgy

基　　金：国家自然科学基金资助项目(51604068,51574064)

摘　　要：针对铁矿物的气固还原,钢铁冶金领域内主要采用未反应核模型对其进行研究.目前即使考虑还原剂为CO+H 2混合气体,也就是CO-CO 2-H 2-H 2O四元体系参与扩散的情况,未反应核模型中对内扩散环节的描述仍以仅严格适用于二组元扩散体系的Fick定律为主.因此,本文以精确描述复杂多组元体系传质过程的Maxwell-Stefan关系式为基础,首先建立与其耦合的铁矿物气固还原单界面未反应核模型,并开发相关数值算法.然后,通过比较相同条件下基于Fick定律未反应核模型(Fick模型)和基于Maxwell-Stefan关系式未反应核模型(M-S模型)的计算结果,探讨采用Fick定律描述多组元气体内扩散相对于采用Maxwell-Stefan关系式描述多组元气体内扩散的偏差.研究结果表明,相比于M-S模型,Fick模型计算的CO还原速率偏小,H 2还原速率偏大,总还原速率偏大,并且这些偏差随矿石还原度的提高和固体产物层结构参数的减小而增大.对某一组元(CO或H 2)的还原速率而言,Fick模型的计算偏差随该组元含量的增加而减小.对总还原速率而言,各组元含量越接近,Fick模型的计算偏差越大.与之相反,各组元含量差异越大,Fick模型的计算偏差越小.Studies regarding gaseous reduction of iron ore in the field of ferrous metallurgy are conducted mainly by using the unreacted shrinking-core model (USCM). At the current stage, the internal diffusion step in USCM is usually described by Fick’s law that is accurate only for binary diffusion systems. However, this Fick’s law based USCM (Fick Model) is often adopted in scenarios where the gaseous reducing agent is a mixture of CO and H 2, leading to a quaternary diffusion system of CO-CO 2-H 2-H 2O. A novel one-interface USCM coupled with the Maxwell-Stefan relations, which can describe precisely multicomponent mass transfer processes, is therefore built in the present work and a numerical algorithm is developed correspondingly. In order to assess the consequences due to the aforementioned description of CO-CO 2-H 2-H 2O diffusion system by Fick’s law, the results calculated by the (conventional) Fick Model and the Stefan-Maxwell relations based USCM (M-S Model) are compared under identical conditions. The comparisons show that CO, H 2 and total reduction rates calculated by the Fick Model are generally different from the ones by the M-S Model. The deviations regarding CO, H 2 and total reduction rates are negative, positive and positive, respectively. In addition, these deviations become greater with an increase in reduction degree of iron ore and with a decrease in the structural parameter of solid product shell (the ratio between porosity and tortuosity of solid product shell). As for reduction rate of each individual species (CO or H 2), the deviation of Fick Model becomes smaller as its content increases. As for the total reduction rate of the whole process, the deviation becomes greater as the contents of CO and H 2 are more comparable. As the contents of the two species differ greater from each other, nevertheless, the deviation becomes smaller.

关 键 词：铁矿石还原 气固反应 等摩尔反向扩散 多组元气体扩散 未反应核模型 

分 类 号：TF531[冶金工程—钢铁冶金]