GASEOUS REDUCTION OF IRON OXIDES .4. MATHEMATICAL-ANALYSIS OF PARTIAL INTERNAL REDUCTION-DIFFUSION CONTROL
GASEOUS REDUCTION OF IRON OXIDES .4. MATHEMATICAL-ANALYSIS OF PARTIAL INTERNAL REDUCTION-DIFFUSION CONTROL
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DOI：
10.1007/bf02643212
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发表时间：
1972-01-01
期刊：
影响因子：
--
通讯作者：
TURKDOGA.ET
中科院分区：
文献类型：
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作者：
TIEN, RH;TURKDOGA.ET
在氧化铁气态还原的数学分析中，在推导速率方程时同时考虑了多孔氧化物的部分内部还原和多孔铁层中的气体扩散。速率方程由部分解析解和部分数值解推导出来，并得到了先前获得的实验结果的充分证实。先前确定的以下参数用于速率方程的应用：i) 维氏体孔壁上气体反应的特定速率常数，ii) 维氏体的孔表面积，iii) 赤铁矿还原过程中形成的多孔维氏体中的有效气体扩散率，以及 iv) 多孔铁层中的有效气体扩散率。随着还原进度超过约 50% O 去除量，维氏体-铁扩散界面处的内部还原区的有效深度急剧增加。对于在 100% H2 中还原 1 至 2 厘米直径的赤铁矿球体，扩散铁-维氏体界面处的气体成分在铁-维氏体平衡气体成分的 10 至 20% 范围内；超过约 50% O 去除量后，还原速率主要由多孔铁层中的气体扩散控制。从数学分析发现，内部还原的相对深度随着颗粒尺寸的减小和温度的升高而增加。
In this mathematical analysis of gaseous reduction of iron oxides, the partial internal reduction of the porous oxide and gas diffusion in the porous iron layer are considered simultaneously in deriving the rate equation. The rate equation, derived by partly analytical and partly numerical solutions, is well substantiated by the experimental results obtained previously. The following parameters, determined previously, are used in the application of the rate equation: i) specific rate constant for the gas reaction on the pore walls of wustite, ii) pore surface area of wustite, iii) effective gas diffusivity in the porous wustite formed during reduction of hematite, and iv) effective gas diffusivity in the porous iron layer. The effective depth of the internal reduction zone at the wustite-iron diffuse interface increases steeply with the progress of reduction beyond about 50 pct O removal. For reduction of 1 to 2 cm diam hematite spheroids in 100 pct H2, the gas composition at the diffuse iron-wustite interface is within 10 to 20 pct of that for the iron-wustite equilibrium; beyond about 50 pct O removal, the rate of reduction is controlled primarily by gas diffusion in the porous iron layer. From the mathematical analysis it is found that the relative depth of internal reduction increases with decreasing particle size and increasing temperature.