电池级碳酸锂精制工艺技术研究

Study on purification technology of battery grade lithium carbonate

从氢化前处理、氢化反应、热分解、母液循环4个阶段对电池级碳酸锂生产工艺进行优化。实验结果显示:氢化前处理阶段,工业级碳酸锂经过6倍氨三乙酸(相对于钙镁杂质总量)处理,再经6倍EDTA(相对于钙镁杂质总量)氢化分解除杂,杂质去除率达到98%以上;氢化反应阶段,由氢化溶解率与氢化液p H变化趋势确定氢化时间为80 min、适宜液固质量比大于23∶1;热分解阶段,加入乙醇、升高温度都能提高热分解效率,热分解效率达到69.5%,相比空白提高了21.1%;产品纯度随洗涤次数的增加先增加后降低,3次洗涤后产品纯度达到电池级标准;经过最终母液循环,整体液固质量比降至10∶1左右,产品纯度达到99.5%以上,回收率大于92%,钙、镁含量分别降至0.000 5%、0.002 0%。

The purification processes of Li2 CO3 were divided into four stages,such as hydrogen pretreatment, hydrogenation reaction,thermal decomposition and mother liquor circulation,to simplify the production process,reduce production cost and improve process efficiency.The experimental results showed that the impurity removal rate of industrial grade Li2 CO3 more than 98% after 6 times（relative to the total amount of calcium and magnesium impurities） wash of ammonia acetic acid hydrogenation process and 6 times（relative to the total amount of calcium and magnesium impurities） wash of EDTA.The optimum hydrogenation time was 80 min,and the optimum liquid-solid ratio was greater than 23∶1 in the hydrogenation reaction stage according to the change trend of the hydrogenating dissolution rate and the p H of the hydrogenation solution.The heat decomposition efficiency can be improved by adding ethanol and increasing the internal temperature in the thermal decomposition process.The thermal decomposition efficiency was up to 69.5%,which was increased by 21.1% compared with blank controlled experimental result.The purity of the product increased first and then decreased with the increase of washing times,and the purity reached the battery grade standard after 3 times washing.Through the mother liquor circulation,whole liquid-solid ratio decreased to about 10∶1,the purity of the product reached more than 99.5%,the recovery rate was more than 92%,Ca and Mg content were reduced to 0.000 5% and 0.002 0%,respectively.