Zn在FetO-CaO-SiO2-Al2O3渣系中的挥发行为

Vaporization behaviors of Zn in Fe_tO-CaO-SiO_2-Al_2O_3 slag system

研究Zn在含Cl的FetO-CaO-SiO2-Al2O3渣系中的挥发行为,包括挥发气体种类、挥发率以及各因子如温度、渣成分、添加剂等的影响。应用吉布斯自由能最小化原则,热力学计算显示在本实验温度条件下,样品90%渣+10%ZnO+CaCl2中的挥发气体为金属Zn、ZnCl2及FeCl2。实验结果表明,金属Zn及FeCl2气体挥发量随温度增加而增加,而ZnCl2气体量却随之降低。反应初期,样品挥发速度很快,10 min后基本趋于稳定,ZnCl2主要形成于样品升温期间(室温至实验温度1 190℃),恒温期间,生成的ZnCl2与FeO反应生成FeCl2气体及ZnO,后者又被FeO还原成金属Zn气体。渣成分中,FeO含量和二元碱度CaO/SiO2对Zn的挥发气体种类及挥发率有重要影响。添加还原剂如C粉可显著提高Zn的挥发率。

Vaporization behavior of zinc in the slag system FetO-CaO-SiO2-Al2O3 was examined, including the formation ratio of vapor species and their partitioning as well as the effect of process factors such as temperature, holding time, slag composition, and addition of reductive agents. A thermodynamic estimation with the principle of Gibbs free energy minimization shows that the major vapor species from the sample of FeO-CaO-SiO2-Al2O3 system＋ZnO＋CaCl2 are metallic Zn, ZnCl2 and FeCl2 in the experimental temperature range. The results suggest that the formation ratio of metallic Zn and FeCl2 increases with temperature increasing, while that of ZnCl2 decreases. The evaporation of sample is initially fast and becomes steady after holding for 10 min. Gaseous ZnCl2 is mainly formed during heating period, at the holding stage it reacts with FeO to produce gaseous FeCl2. With regard to slag compositions, FeO and basicity significantly affect the evaporation of zinc. The evaporation ratio of zinc can be enhanced by the addition of reductants such as carbon powder.