Influence of pellet composition and structure on carbothermic reduction of silica
Influence of pellet composition and structure on carbothermic reduction of silica
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DOI：
10.1007/s11663-999-0059-9
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发表时间：
1999-04
期刊：
影响因子：
--
通讯作者：
A. Agarwal;U. Pad
中科院分区：
文献类型：
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作者：
A. Agarwal;U. Pad
冲天炉中的熔化区具有大于1773 K的温度和还原性气氛。此条件适合于二氧化硅的碳热还原。硅碳热还原法生产铁合金的关键是快速原位生成SiC及其随后在铁水中的溶解。本研究的主要目的是研究碳热还原过程的动力学，并确定快速和完全原位转化二氧化硅到SiC的最佳参数。在1773 K以上，碳热还原过程的关键反应为：（1）SiO2（s）+CO（g）= SiO（g）+CO2（g），（2）SiO（g）+2C（s）= SiC（s）+CO（g），（3）C（s）+CO2（g）= 2CO（g）。为了满足本研究的目的，条件必须使得在碳和二氧化硅表面发生的表面反应是速率限制的，并且整个二氧化硅转化为SiC。颗粒组成和结构的碳硅比，它们的颗粒尺寸，和压实压力，确保表面反应是速率控制方面进行了测定。根据工艺参数对气固反应动力学进行了数学建模。反应动力学通过减小碳和二氧化硅颗粒尺寸而改善。然而，低于某一临界粒度，反应动力学没有显著改善。为了将SiO2（s）完全转化为SiC（s），过量的碳和临界孔隙率是必要的，以确保反应[1]产生的全部SiO（g）通过反应[2]在颗粒内消耗。
The melting zone in a cupola has temperatures greater than 1773 K and a reducing atmosphere. This condition is suitable for the carbothermic reduction of silica. The key to the applicability of carbothermic reduction of silica for ferroalloy production is rapidin situproduction of SiC and its subsequent dissolution in the hot metal. The main objective of this investigation was to study the kinetics of the carbothermic reduction process and determine the optimum parameters for rapid and completein situconversion of silica to SiC. At temperatures above 1773 K, the key reactions in the carbothermic reduction process are (1) SiO2(s)+CO (g)=SiO (g)+CO2(g), (2) SiO (g)+2C (s)=SiC (s)+CO (g), (3) C (s)+CO2(g)=2CO (g). To meet the objective of this study, conditions must be such that the surface reactions occurring at the carbon and silica surfaces are rate limiting and the entire silica is converted to SiC. Pellet composition and structure in terms of carbon to silica ratio, their particle sizes, and compaction pressure that ensure surface reaction is rate controlling were determined. The gas-solid reaction kinetics was mathematically modeled in terms of the process parameters. The reaction kinetics improved by reducing both carbon and silica particle sizes. However, below a certain critical particle size, there was no significant improvement in the reaction kinetics. For complete conversion of SiO2(s) to SiC (s), excess carbon and critical porosity are necessary to ensure that the entire SiO (g) generated by Reaction [1] is consumedviaReaction [2] within the pellet.