真空铝热还原Li_5AlO_4制取金属锂的研究

Extraction of Lithium from Li_5AlO_4 by Vacuum Aluminum Thermal Reduction

常压煅烧氢氧化锂、氧化铝和氧化钙混合物可得到Li_5AlO_4型富锂熟料,真空铝热还原该熟料可制备金属锂,同时获得12CaO·7Al_2O_3型还原渣,该渣通过碱液溶出、碳酸化分解可制备氢氧化铝。研究了还原温度、还原时间、铝粉过量系数对真空铝热还原制取金属锂过程的影响。结果表明:在系统压强-5 Pa,还原温度1200℃,还原时间120 min,铝粉不过量的条件下,金属锂的还原率为97.76%,还原渣主要成分为12CaO·7Al_2O_3。铝粉过量超过10%不利于金属锂还原率的提高,且还原渣的主要成分为CaO·2Al_2O_3和CaO·Al_2O_3。

Pure Li was extracted from Li5AlO4by vacuum aluminum thermal reduction with a calcinated mixture of Li OH,Al2O3 and CaO powders as the raw materials,with Al powder as reduction agent,and with 12 CaO ·7 Al2O3 as the slag,which could be recycled into Al（ OH）3later by leaching and by decomposing with CO2. The impact of the reduction temperature and time,and Al excess coefficient on Li reduction rate were experimentally investigated. The results show that the thermal reduction rate of Li could be as high as 97. 76 % under the optimized conditions： reduced at 1200 ℃ for 120 min,at a pressure below 5 Pa and with an Al excess coefficient of 0. 0 %（ wt）.12 CaO·7 Al2O3 phase was found to dominate the reduction slag. As the Al excess coefficient increased to above10 %,Li reduction rate decreased,accompanied by a dominance of CaO ·2 Al2O3 and CaO · Al2O3 phases in the slag.