锂辉石-氧化钙烧结法提锂的物相重构与动力学

Phase reconstruction and kinetics of lithium extraction by spodumenecalcium oxide sintering process

对锂辉石-氧化钙烧结过程进行热力学分析,绘制了各反应Gibbs自由能与温度的关系图。结果表明,Al2O3会优先和Na2O、Li2O、K2O反应,然后与CaO反应生成CaO·Al2O3,而且烧结温度需高于1060℃以保证LiAlSi2O6能够完成晶形转变。并探讨了锂辉石-氧化钙烧结法提锂的反应机理。考察了不同烧结条件对锂浸出率的影响并对熟料进行X射线衍射(XRD)分析表征。实验结果表明,在配料比为1∶1.25、烧结温度1150℃、烧结时间60min时,锂的浸出率达到92.14%,熟料中的主要物相为Ca2SiO4与LiAlO2。利用XRD和扫描电镜-能谱联用仪(SEM-EDS)对熟料与浸出渣的物相、显微形貌及元素分布情况进行了分析表征。为了确定烧结反应的控制性步骤,在最优烧结条件的基础上对烧结过程进行动力学分析,结果表明,锂辉石-氧化钙烧结体系属于球形颗粒三维界面化学反应控制,烧结过程的动力学拟合方程为1-(1-x)^1/3=0.00677t。

In this paper, the thermodynamic analysis of spodumene-calcium oxide sintering process was carried out, and the relationship between Gibbs free energy and temperature was plotted. The results showed that the Al2O3 will react with Na2O, Li2O and K2O first and then with CaO to form CaO·Al2O3. The sintering temperature was higher than 1060℃ to ensure that the LiAlSi2O6 can complete the crystal transition. The reaction mechanism of lithium extraction by spodumene-calcium oxide sintering method was discussed in detail. The effect of sintering conditions on the leaching rate of lithium was investigated and the clinker was characterized by XRD.The experimental results indicated that the leaching rate of lithium reached 92.14% when the mixture ratio was 1∶1.25 at the sintering temperature of 1150℃, and the sintering time of 60 min. The main phases in clinker were Ca2SiO4 and LiAlO2. The phase,microstructure and distribution of element of clinker and leaching slag were analyzed and characterized by XRD and SEM-EDS. In order to to determine the control step of the sintering process, the dynamic analysis of the sintering process was carried out on the basis of the optimized sintering conditions. The results showed that the spodumene-calcium oxide sintering system was chemical reaction control of the three-dimensional interface of the spherical particles, and the fitting equation of the kinetics of the sintering process was 1-(1-x)^1/3= 0.00677 t.