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以碳酸钠为添加剂,采用氧化焙烧-水浸工艺从高硅高钙低品位钒渣中提取五氧化二钒。考察了碳酸钠加入量、焙烧温度、焙烧时间、浸出温度、浸出时间、浸出液固比等对钒浸出率的影响。结果表明:氧化焙烧过程对钒的提取影响显著,而水浸过程影响较小。通过氧化焙烧使钒转化为可溶性的钒酸钠与不溶性的钒酸钙。在水浸过程中,钒酸钠溶于水;而钒酸钙与磷酸钠或硅酸钠反应转化为可溶性的钒酸钠,可同时除去浸出液中的杂质硅和磷。通过实验获得了优化工艺参数:碳酸钠加入量为18%,焙烧温度为700℃,焙烧时间为2.5 h;浸出温度为90℃,浸出时间为30 min和液固比为5∶1 m.lg-1。在此优化条件下,钒浸出率可达到89.5%以上,浸出液中主要杂质为Si,P和Cr。产物五氧化二钒的纯度大于99%。
Taking sodium carbonate as additive, the vanadium pentoxide was extracted from the high-silicon, low-calcium and low-grade vanadium slag by oxidation roasting-water immersion process. The effects of sodium carbonate addition amount, calcination temperature, calcination time, leaching temperature, leaching time and leachate solidification ratio on the leaching rate of vanadium were investigated. The results show that the oxidation roasting process has a significant effect on the extraction of vanadium, but has little effect on the leaching process. Vanadium is converted to soluble sodium vanadate and insoluble calcium vanadate by oxidative roasting. During flooding, sodium vanadate is soluble in water; and calcium vanadate is converted to soluble sodium vanadate by reaction with sodium or sodium silicate, which removes both silicon and phosphorus impurities in the leachate. The optimized process parameters were obtained through experiments: the amount of sodium carbonate was 18%, the calcination temperature was 700 ℃, the calcination time was 2.5 h, the leaching temperature was 90 ℃, the leaching time was 30 min and the liquid-solid ratio was 5:1 m.lg -1. Under this optimized condition, vanadium leaching rate can reach over 89.5%, and the main impurities in leaching solution are Si, P and Cr. The purity of the product vanadium pentoxide is more than 99%.