Abstract: A new method for transforming calcium orthovanadate to vanadium oxide，through carbonization ammoniation/cooling crystallization was proposed for processing vanadium slag by KOH sub-molten salt method. According to the investigation of the equilibrium solubility data for ternary NH4HCO3-NH4VO3-H2O system at the temperatures of carbonization reaction（75℃）and vanadium crystallization（40℃），solubility data of NH4VO3 was finally achieved. At the temperature of 40℃，solubility data of NH4VO3 decreased with increasing NH4HCO3 concentration. And at the temperature of 75℃，the change of NH4VO3 solubility data followed the U type with concentration of NH4HCO3. Based on the different solubility curves，the design was proved and the theory of crystallization rate 92.71% was deduced. A flowchart of vanadium transformation process was optimized for processing vanadium slag with KOH sub-molten salt method.

Key words: sub-molten salt, calcium orthovanadate, ammonium metavanadate, carbon dioxide, crystallization, optimization

摘要： 针对钾系亚熔盐法钒渣钒铬共提清洁生产工艺的中间产品钒酸钙，提出通过碳化铵化/冷却结晶将钒酸钙转化为钒氧化物产品的新方法。分别研究了NH4HCO3-NH4VO3-H2O三元体系在碳化反应温度（75℃）和结晶沉钒温度（40℃）时NH4VO3的溶解度，得到了此时NH4VO3的溶解度数据。40℃时，NH4VO3溶解度随NH4HCO3浓度升高而降低。75℃时，NH4VO3溶解度则随NH4HCO3浓度升高呈U形变化。通过对比两个温度下NH4VO3的溶解度曲线，验证了碳化铵化工艺75℃反应、40℃结晶的设计思路。并经过理论计算，得到NH4VO3的理论一次结晶率为92.71%。再由得到理论结晶率时的反应和结晶NH4HCO3浓度，优化了钾系亚熔盐法钒渣钒铬共提清洁生产工艺中钒转化单元的工艺路线，绘制了工艺原则流程图。

关键词: 亚熔盐, 钒酸钙, 偏钒酸铵, 二氧化碳, 结晶, 优化