Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (06): 1312-1318.doi: 10.3866/PKU.WHXB20110524

• THERMODYNAMICS, KINETICS, AND STRUCTURAL CHEMISTRY • Previous Articles     Next Articles

Thermodynamic Analysis of Silicothermic Reduction Zinc Oxide in Vacuum

YU Chao, QIU Ke-Qiang, CHEN Qi-Yuan   

  1. College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P. R. China
  • Received:2010-12-13 Revised:2011-02-14 Published:2011-05-31
  • Contact: QIU Ke-Qiang E-mail:qiuwhs@sohu.com
  • Supported by:

    The project was supported by the National Key Basic Research Program of China (973) (2007CB613601).

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Abstract:

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.

Key words: Vacuum silicothermic reduction, Hot dip galvanizing ash, Thermodynamics, Slagging reaction, Zinc metal