Study On Preparation Process Of Battery Grade Lithium Carbonate

Nowadays,lithium extraction technology in brine has made great strides.The supply and demand of industrial-grade Li₂CO₃ have gradually become saturated in the international market.The price of industrial Li₂CO₃dramatically dropped due to lowering development cost.However,the development of high-purity Li₂CO₃ will not only improve the added value of products,but also facilitate the serial development and extension of the industrial chain for lithium products.Therefore,putting lithium resources to good use and researching the battery-grade lithium carbonate preparation process intensively is a subject with highly value of industrial application.The aim of this dissertation adopts the carbonation decomposition method to purify the industrial waste generated by a company's production of batteries,and to obtain products that meet the battery grade lithium carbonate industry standard.First,the experimental conditions of the thermal decomposition stage were explored to find the appropriate thermal decomposition conditions.On this basis,with the purity and yield of lithium carbonate as indicators,the effects of carbonization temperature,carbonization time,CO₂ flow rate,solid-liquid ratio,and stirring speed on the purification of lithium carbonate were examined.And for some impurities with difficulty to remove,using multiple filter cake cycle,filtrate circulation and cake filtrate cycle to further purification of lithium carbonate impurities,so that the product can fully meet the industry standards of lithium carbonate battery grade.From the macroscopic kinetics of the carbonization process study and the effects of various factors on the carbonation reaction process:?1?The experimental results of the thermal decomposition stage showed that the suitable thermal decomposition reaction conditions are reaction time60 min,reaction temperature 95?,stirring speed 300 rpm.Experiments were carried out under suitable thermal decomposition conditions to obtain a Li₂CO₃ yield of 71.98%.?2?The experimental results of carbonization decomposition showed that the suitable reaction conditions were solid-liquid ratio 1:50,reaction time 60min,CO₂ flow rate 10L/min,reaction temperature 20°C,stirring speed 300rpm.The analysis of the products made under suitable carbonization reaction conditions can meet the requirements of battery grade lithium carbonate except for Mg,Ca,K impurities,and the yield can reach 80.11%.?3?The carbonization decomposition experiments showed that the purity of Li₂CO₃ was improved by filter cake cycle several times to reduce the impurity,but yield reduced sharply.The yield and purity of Li₂CO₃were improved by filtration cycle several times but the effect of removing impurities on Mg?Ca is limited.Therefore,neither the filtrate loop nor the cake loop should be used as the preferred circulation method.After 5 cycles of filtrate cakes and filtration,the Li₂CO₃ product yield above 55%,up to industry standard for battery-grade lithium carbonate.The prepared Li₂CO₃product has a rod-like morphology,uniform size,and good dispersibility.?4?From macro-kinetics experimental study,the“gray layer control”condensation model fitting equation can better fit this carbonization reaction,the macro-kinetics formula can be calculated as follow:1-3?1-x?^2/3+2?1-x?=ktApparent activation energy E_a=-36.344kJ/mol.