SiO_2在炉渣CaO-SiO_2-MgO-Al_2O_3体系中的熔解行为

Melting Behavior of SiO_2 in CaO-SiO_2-MgO-Al_2O_3 System

采用直接熔解法研究了SiO_2颗粒在CaO-SiO_2-MgO-Al_2O_3渣系中的熔解过程,探索了炉渣成分、温度对SiO_2颗粒熔解时间的影响规律,通过SEM-EDS并结合factsage软件分析了SiO_2熔解机理,确定SiO_2颗粒周围没有形成固相层,并在此基础上结合缩芯模型构建了动力学模型。结果表明,随着炉渣碱度及温度提高,SiO_2颗粒熔解完成所需时间逐渐降低,而随着炉渣中MgO及Al_2O_3含量增加,SiO_2颗粒的熔解完成所需时间先降低后增加。SiO_2的熔解过程分为2个阶段,反应前期为界面反应控制,表观活化能为330.52 k J/mol;反应后期为外扩散控制,表观活化能为480.28 k J/mol,控制环节的转变是由熔体黏度的变化造成的。

The melting process of SiO_2 particles in CaO-SiO_2-MgO-Al_2O_3 system was studied by using direct melting method,and effects of furnace slag compositions,temperature on the SiO_2 particles melting time were investigated. The melting mechanism of SiO_2 particles was analyzed by using SEM-EDS and factsage software. It is found that there was no solid-phase layer formed around SiO_2 particles.On this basis,a kinetic model was constructed by combining with the shrinking core model. Results show that the melting time of SiO_2 particles in slag shortened with the rising of slag basicity and temperature,while the increased content of MgO and Al_2O_3 in slag led to the melting time of SiO_2 particles prolonged after initially shortened. It is shown that the melting process of SiO_2 is divided into two stages： an earlier stage is controlled by a surface reaction,with an apparent activation energy of 330. 52 k J/mol,and the later stage is controlled by an external diffusion with an apparent activation energy of 480. 28 k J/mol. And such transition is mainly caused by the variation in the melt viscosity.