真空硅热还原氧化锌的热力学分析

通过热力学计算并分析了真空硅热法还原氧化锌反应的吉布斯自由能. 结果表明, 在1100-1500 K温度范围内硅热还原氧化锌具有热力学上的可行性, 但是生成的SiO₂与反应物ZnO反应生成炉渣2ZnO·SiO₂, 导致约50% (w)的ZnO不能被还原. 如果加入CaO与SiO₂造渣, 就能抑制2ZnO·SiO₂的生成, 保证ZnO完全被还原成金属锌. 热力学计算表明, 造渣反应和真空工艺都可以降低还原反应的吉布斯自由能. 实验结果表明, 热镀锌灰中分离出的ZnO在温度为1448 K、真空度为20 Pa、反应时间为2 h的条件下通过硅热还原可得到具有良好结晶形貌的金属锌, 还原率为92.81%. 经X射线衍射(XRD)分析, 反应后的残渣主要成分为2CaO·SiO₂.

Thermodynamic Analysis of Silicothermic Reduction Zinc Oxide in Vacuum

The Gibbs free energy of a vacuum silicothermic reduction for the production of metallic zinc was calculated and analyzed thermodynamically. The results show that reducing ZnO by silicon is thermodynamically possible at 1100-1500 K. However, about 50%(w) of the ZnO was not reduced because the SiO₂ generated by the reduction of ZnO with silicon can react with ZnO and produce 2ZnO·SiO₂. Upon the addition of CaO, it can react with SiO₂ before ZnO to inhibit the production of 2ZnO·SiO₂ and ZnO can be reduced to Zn completely. Slagging reactions and the vacuum technique can be used to lower the Gibbs free energy of the reduction reaction. We carried out experiments to reduce ZnO from hot dip galvanizing ash using silicon. The results showed that the reduction efficiency of ZnO was 92.81% and the metal Zn obtained was well crystallized under the following experimental conditions: a temperature of 1448 K, a vacuum reduction time of 120 min, and a residual gas pressure of 20 Pa. X-ray diffraction (XRD)analysis indicated that the main compound in the slag was 2CaO·SiO₂.