Research On Reactive Crystallization Of Lithium Carbonate

With the rapid development of the lithium battery industry,lithium carbonate is an essential raw material for lithium battery electrodes.The purpose of this research is to optimize production conditions of lithium carbonate with the help of artificial neural networks(ANN)and computational fluid dynamics.Firstly,to control the nucleation of the reactive crystallization process,a model for predicting the metastable zone widths for this process was developed.Existing empirical models have various shortcomings such as large experimental quantity and severe restrictions.Artificial neural networks were introduced to predict the metastable zone widths.Compared with empirical models,the usual ANN model increased accuracy by 2% on average.The orthogonal-dataset-trained ANN model also has better prediction efficiency,which could reach the same accuracy using only 12% training dataset.The results showed that the orthogonal ANN model could improve the prediction accuracy while reducing the amount of experiments.Then the crystallization kinetics of the reaction crystallization process of lithium carbonate was analyzed with the continuous steady-state method,and the nucleation and growth kinetic equations of lithium carbonate were derived.It was found that the crystal growth of lithium carbonate in solution is a particle-size dependent growth.The crystallization kinetics and computational fluid dynamics(CFD)were combined to complete the continuous and steady-state numerical simulation of the lithium carbonate reaction crystallization process.The crystallizer used in the simulation was a 4.5L crystallizer with a Ruston impeller,and the k-ε model was used to simulate the flow field.Then importing the particle balance equation(PBE)into the flow field by user defined function,the coupled CFD-PBE model was founded.A high-resolution(HR,high resolution)method was used to discretize the model and solved the equations.After experimental verification,the results turned out to be consistent with the experiments.Finally,the effects of stirring speed,residence time and temperature on the particle size distribution of lithium carbonate crystals were investigated.It was found that the higher stirring speed leads to the smaller particle size;as the higher temperature or residence time get higher,the average particle size became larger;as the stirring speed and residence time increases,the PSD(particle size distribution)become more uniform.In summary,based on the orthogonal ANN model,this paper solved the problem of large experimental amount and difficulty in stable prediction on metastable width prediction.In addition,the reactive crystallization kinetics of lithium carbonate was established.Coupled with CFD,it can help guide industry scaling up of the crystallizer.