As2O3真空碳热还原制备粗金属砷的热力学研究

采用HSC Chemistry 5.0热力学分析软件研究了As2O3真空碳热还原制备粗金属砷过程的吉布斯自由能与温度的关系,重点研究了挥发过程、碳热还原过程及砷蒸汽冷凝过程。结果表明,常压下As2O3在773K时以As4O6(g)双原子气态形式挥发,而在100Pa下挥发只需473K即可,与实际情况一致;As2O3(g)气体参与碳热还原过程的可能性较小,As2O3(s)粉末、As4O6(g)气体在100Pa真空压力下参与碳热还原反应温度分别是473～810K、873K,该温度均低于常压碳热还原过程所需温度(893～1 203℃);砷蒸汽的冷凝过程是As4(g)蒸汽先凝结成液态砷后,再冷凝成固态粗金属砷。

Thermodynamic Analysis on Crude Metal Arsenic Preparation by Arsenic Trioxide Carbothermic Reduction in Vacuum

Relationships between Gibbs free energy and temperature for crude metal arsenic preparation by As2O3 carbothermic reduction in vacuum were investigated with HSC Chemistry 5.0 thermodynamic analysis software. Volatilization process, carbothermic reduction process and arsenic vapor condensation process were emphatically studied. The results show that As2O3 volatilizes as As4O6(g) diatomic at 773 K under 0.1 MPa and 473 K under 100 Pa, which is highly correspondence with actual situation. There is little possibility for As2O3(g) take part in carbothermic reduction process. The temperature for As2O3(s) and As4O6(g) participate in carbothermic reduction reaction under 100 Pa is 473~810 K and 873 K respectively, which is less than that of 893~1 203 K under 0.1 MPa. The condensation process for arsenic vapor is As4(g) vapor firstly condensated into liquid arsenic, and then into solid arsenic.