Analysis of the kinetic models of the silicothermic reduction process and their numerical simulation

doi:10.16085/j.issn.1000-6613.2018-2411

Abstract

Abstract:

The silicothermic reduction is the dominating technology to produce magnesium. However, the detailed kinetic and numerical simulation study of this process has been rarely reported due to its high reaction temperature and complicated heat transfer mechanism. According to experimental data, the segmental model was established, which was then transformed into an accurate mathematic model. After that, a three-dimensional unsteady numerical model incorporating the mathematical model, radiation and heat conduction models was established and used to predict the magnesium reduction and temperature distributions in the retort. The results indicated that the minimum temperature in the retort reached 1203K in 2 hours and the average magnesium reduction extent increased to 66% in 4 hours. Finally, we pointed out that the increase of the outer layer of briquette number and the enhancement in the heat transfer efficiency of the retort center could improve this technique. Besides, this study also could be applied to enhance the heat transfer equipment design, and to forecast the practical industrial production so that lots of amount of laboratory investment can be saved.

Key words: magnesium, production, reaction kinetics, kinetic modeling, heat transfer, numerical simulation

摘要：

硅热法是目前工业产镁的主要技术手段，但由于该过程涉及高温化学反应及复杂传热机理，鲜有报道对此技术进行详细动力学及数值计算研究。本工作采用实验的方法获得皮江法炼镁化学反应动力学数据，根据数据分析确定了分段动力学模型，并转化为精确的数学模型。然后建立了耦合数学模型、辐射模型和导热模型的三维非稳态数值计算模型，并通过数值模拟计算，获得工业产镁过程中球团反应转化率和温度随生产时间的分布规律。计算结果表明，生产时间2h后球团最低温度已达1203K，4h后物料平均还原率已达66%。该技术改进方向主要为增加外层球团数量并提高还原罐中心区域传热效率。本工作可以用于指导强化传热设备的设计，预测实际生产效果，节省大量试验投资。

关键词: 镁, 生产, 反应动力学, 动力学模型, 传热, 数值模拟

CLC Number:

Chao ZHANG,Jin FU. Analysis of the kinetic models of the silicothermic reduction process and their numerical simulation[J]. Chemical Industry and Engineering Progress, 2019, 38(9): 4155-4163.

张超,付瑾. 硅热法炼镁动力学的数学模型分析及数值模拟[J]. 化工进展, 2019, 38(9): 4155-4163.

Figures/Tables 13

化学组成成分	质量分数/%
MgO	21.07
CaO	32.44
SiO₂	0.58
Fe₂O₃	0.09
Al₂O₃	0.06
分解率	45.76

化学组成成分	质量分数/%
Si	76.08
Fe	21.75
Al	0.88
Ca	0.72
Mn	0.33
Cr	0.14
C	0.10

动力学模型	方程
Jander	$1 - 1 - α 1 / 3 2 = k J τ$
Ginstling	$1 - 2 / 3 α - 1 - α 2 / 3 = k G τ$
Surface reaction	$1 - 1 - α 1 / 3 = k S τ$
1^st Avrami	$- l n (1 - α) = k A τ$
Erofeev	$- l n 1 - α 1 / 3 = k E τ$

动力学模型	方程
Jander	$1 - 1 - α 1 / 3 2 = k J τ$
Ginstling	$1 - 2 / 3 α - 1 - α 2 / 3 = k G τ$
Surface reaction	$1 - 1 - α 1 / 3 = k S τ$
1^st Avrami	$- l n (1 - α) = k A τ$
Erofeev	$- l n 1 - α 1 / 3 = k E τ$

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