Abstract:

The gas-liquid-solid reactive crystallization process of lithium carbonate includes two consecutive steps, which are the carbonization reaction process of lithium carbonate and the thermal decomposition process of lithium bicarbonate solution. First, the factors of the lithium carbonate carbonization reaction rate were investigated. The numerical solution was obtained by solving the established model, which proved that the lithium carbonate carbonization process obeyed the diffusion-controlled mechanism. For the thermal decomposition process, the relationship between the particle size distribution, crystal morphology, and agglomeration of lithium carbonate crystalline products and factors such as the concentration, temperature, stirring, seed crystals, and external field have been studied. Especially, rod-shaped lithium carbonate crystals with complete morphology and no coalescence can be obtained by using ultrasonic sound. Finally, the fouling mechanism of lithium carbonate was revealed by continuous crystallization experiments, which were designed to investigate the fouling phenomenon in industrial-scale production. The smooth surface coupled with the seed addition in metastable zone strategy was proposed to effectively avoid the fouling.

Key words: crystallization, reactive crystallization, separation, kinetics, lithium carbonate

摘要：

碳酸锂的气液固三相反应结晶过程包含碳酸锂碳化反应和碳酸氢锂溶液的热析分解两个过程。首先对于碳化过程，考察了碳酸锂碳化转化率和反应速率的影响因素；建立并求解构建碳化微观机理模型，进而确定了碳酸锂碳化过程为气体传质控制。对于热析分解过程，研究了碳酸锂晶体产品的粒度分布、晶体形貌和聚结程度等与反应物浓度、温度、搅拌、晶种以及外场等因素的关系，尤其是在超声结晶条件下能够获得形貌完整且不聚结的碳酸锂棒状晶体。最后，揭示了碳酸锂的结垢机理，并基于实验验证提出了光滑表面、介稳区控制和晶种添加等方案可有效抑制结垢。

关键词: 结晶, 反应结晶, 分离, 动力学, 碳酸锂