The Study And Optimization Of Carbonization Process In The Lithium Extraction Process

Increasingly important strategic position of lithium products gradually led to the rapid development of salt lake lithium technology.Lithium carbonate as a salt lithium can be directly prepared from lithium salt using salt lake lithium technology,also is the basic raw materials of newly developing lithium battery industry.Lithium resources in the salt lake convert into lithium carbonate products mainly by impurity removal and carbonization reaction.The first step as research hotspot applied in industry frequently,and carbonization process according little research and simple industrial application need more investigated.In this paper,the effects of various factors on the conversion,crystal morphology and impurity content in the industrial carbonization process were studied.Then,according to the shortcomings of the process of industrial carbonization process,two new systems as ball milling and autoclave pressurized reaction systems were proposed,and the effects of the main factors on the conversion,crystal morphology and impurity content of the carbonation process were investigated.There are mainly three sections in this dissertation.（1）The effects of the molar ratio of reactants,the concentration of lithium chloride,the temperature and the rate of feeding on the carbonization process in the process of regular and reverse feeding were investigated.The experimental results show that the reaction temperature has the greatest effect on the conversion,crystal morphology and impurity content of target Li2CO3 products.The microstructure of the target Li2CO3 products prepared at low temperature is close to the flaky intercalation aggregates,and it tend to reach the rod-like interspersed aggregates at high temperature.The two kinds of target Li2C03 particles are both easy to carry impurities and the former impurity content is higher.The conversion under regular and reverse feeding ways were 78.43%and 78.46%under the optimized conditions.And the Na+ content of the target Li2CO3 product was only 0.130%and 0.167%,which was better than that of the industrial grade lithium carbonate.The shortcomings of industrial carbonization process are low conversion and high impurity content of several-times washed products.（2）A technique for preparing Li2CO3 was developed through dry milling mechanochemical process instead of industrial carbonization process.The XRD patterns of primary Li2CO3 powders indicate that mechanochemical reaction of both Na2C03 and LiCl can be completed in 15 min under the optimal conditions at rotation speed as 600 rpm,ball-to-sample mass ratio as 5/1,and molar ratio of Na2CO3 to LiCl as 1/2.The after one-time washing products of Li2CO3 contain impurity of Na+ less than 0.1%with the minimum values as 0.076%which is better than that of industrial carbonization reaction.Two shapes of massive particles and smaller grains less than 1 μm in nano scale can be observed in the target products of Li2CO3 powders.The developed technique for preparing Li2CO3 products can be applied in insufficient water areas such as northwestern China especially in Qinghai-Tibet plateau.（3）The carbonation process of sodium carbonate and lithium chloride solution under the pressure of CO2 and N2 in the autoclave was investigated.Under the optimal reaction conditions,the conversion ware 92.79%with CO₂ pressurization and 92.13%with N2 pressurization,and the conversion were much higher than that of industrial carbonation.The microstructure of target Li2CO3 products under both gas pressurized were accumulation of rod-like particles and amorphous small particles.And the contents of Na+in the Li2CO3 products were 0.114%and 0.128%.In order to avoid the introduction of Na+impurities,using ammonium carbonate as a carbonation agent in the autoclave react with lithium chloride.The reaction conversion is very low and the highest is only 36.38%.So it’s not suitable for industrial application.The above research provides reliable data support for the process optimization and new process development of the carbonization process,which has certain reference significance for the efficient extraction and utilization of salt resources.