CaO固氟焙烧——盐酸浸出回收稀土钙热还原渣中稀土试验研究

Recovery of Rare Earth Elements From Rare Earth Calcium Thermal Reduction Slag by Calcium Oxide Fixation Fluorine Roasting and Hydrochloric Acid Leaching

采用氧化钙固氟焙烧—盐酸浸出法回收稀土钙热还原渣(还原渣)中的稀土和氟化钙,研究了氧化钙焙烧过程还原渣的转型机理、浸出过程的热力学和不同条件下稀土的浸出规律。热力学分析表明:升高温度能够促进氧化钙和氟化稀土反应生成氧化稀土和氟化钙;CaF_(2)的存在会抑制稀土元素的浸出,而高浓度的Ca^(2+)减少了F-溶出、促进稀土浸出。浸出试验结果表明:在一定范围内提高浸出温度、浸出时间、盐酸浓度、液固比均能促进稀土的溶出。适宜条件为:焙烧温度800℃、焙烧时间1.5 h、氧化钙与还原渣质量比为1∶1、球团直径10 mm、焙烧渣磨矿时间3min、浸出温度40℃、浸出时间1.5 h、盐酸浓度4 mol/L、液固比10∶1 m L/g。在上述适宜条件下,稀土浸出率达到95.44%;浸出渣CaF_(2)品位为97.02%,回收率为97.88%,实现了还原渣的高效综合利用。

Rare earth and calcium fluoride were recovered from rare earth calcium thermal reduction slag by calcium oxide fixation fluorine roasting and hydrochloric acid leaching.The transformation mechanism of the reduction slag during calcium oxide roasting,the thermodynamic analysis of leaching process and the leaching rule of rare earth under different conditions were studied.Thermodynamic analysis showed that increasing temperature can promote the reaction of calcium oxide and rare earth fluoride to produce rare earth oxide and calcium fluoride.The presence of CaF_(2)inhibits the leaching of rare earth elements,while the high concentration of Ca^(2+)reduces the leaching of F-and promotes the leaching of rare earth elements.The leaching test results showed that the leaching temperature,leaching time,hydrochloric acid concentration and liquid-solid ratio can promote the leaching of rare earth elements in a certain range.The optimum test conditions were:roasting temperature of 800℃,roasting time of 1.5 h,mass ratio of calcium oxide to reduction slag of 1∶1,pellet diameter of 10 mm,grinding time of roasting slag of 3 min,leaching temperature of 40℃,leaching time of 1.5 h,hydrochloric acid concentration of 4 mol/L,liquid-solid ratio of 10∶1 mL/g.Under the below suitable conditions,the leaching rate of rare earth reached 95.44%.The grade of CaF_(2)in the leaching residue is 97.02%with the recovery rate of 97.88%,and thus the comprehensive utilization of the reduction residue is realized.