Study On A Novel Process For Preparing Lithium From Li₂CO₃ By Vacuum Thermoreduction

Because of the increasing requirement of metal lithium in the domestic and foreign market ,the conventional industrial method ,electrolysis-method, Will not meet the needs. It is extremely urgent to develop a novel practicable way to solve the problem in the conventional method. The process of producing metal lithium in the vacuum thermoreduction of Li2O by reducing agent CaC2^ Al and Al-Si alloy was introduced based on the theoretical analysis and practical research.The properties, the application and the consumption of metal lithium and its compounds were discussed in the part of the introduction. The production method of lithium and its compounds were summarized. The vacuum thermoreduction for producing metal lithium is more advanced compared with the electrolysis-method.The advantages of vacuum reduction of metal-oxides were explained in the part of the theoretical analysis. The feasibility in thermodynamics and the kinetic model of vacuum thermoreduction reaction of Li20 were discussed as well.The experiment in which CaC2 > Al and Al-Si alloy were used respectively as reducing agent ,LJ2CO3 as the raw material were carried out on the condition of the pressure of 5Pa and the reduction temperature ranging from 1173K to 1423K. The mechanism of reducing reaction, the thermodynamics and kinetics model were also observed.The research of vacuum CaC2 reduction of Li2O demonstrated the process of thermodecomposition of CaCa and the thermoreduction of Li2O. The relationship between reduction ratio and reduction temperature as well as reaction time were deduced. It was indicated that both the increasing temperature and the extending time could improve the production ratio of metal lithium. The optimum technical conditions of vacuum thermoreduction of Li2O reduced by CaC2 in a chamber pressure of 5Pa was established: temperature: 1323K, time:80minute, ratio of charge: Li2CO3:CaC2=2:l, in theway the metal lithium with a purity of 98.28% was obtained.The research in the vacuum aluminum thermoreduction of LijO showed that a lower temperature was enough or a higher reduction ratio could be reached with the existence of CaO in raw material at the same condition. For example ,the reaction ratio was 84% which would be above 93% if mixed with CaO in raw material in the vacuum aluminum reduction reactions taking place 90 minute at the temperature of 1373K. Product of 98.89% metal lithium was collected in this experiment.The vacuum Al-Si alloy reduction of Li2O was studied theoretically and the residual of experiments was analyzed in X-ray diffraction. The results showed that the production ratio rose greatly owing to the emergence of more stable product in the reactions. The reduction ratio went beyond 97% on the conditions of the temperature 1373K and the time 90 minute. The metal lithium of 99% content was produced in this experiment carried on the conditions of temperature of 1273K and time of 60 minute.Compared the researches above, a process for preparing metal lithium from Li2C03, by vacuum decomposition, vacuum reduction has been proposed .It will be of significance in reducing production cost of lithium and protecting environment.