Research Of Vacuum Thermal Reduction Preparation Of Metallic Lithium Iron

Lithium and its compounds has been widely applied in various branches of industry with its excellent performance, including medicine、glass、refrigeration ceramics、atomic energy、metallurgical industry and military industry, etc. Along with the development of science and technology, lithium has became an important strategic resource in the national defense and the national economy; meanwhile just because of its advanced capability, lithium was also widely applied in modern high-tech fields such as aluminum-lithium alloy、light alloy、nuclear fusion、aerospace、new high-energy lithium battery, etc. Therefore, it’s very necessary to develop effective or improve the existing technology of preparation lithium. In this paper, situation of lithium resources, the main properties of lithium, the application situation, the prices, the consumption, and its preparation methods are reviewed, and the molten salt electrolysis method and vacuum thermal reduction method were compared and analyzed, obtained the superiority of vacuum thermal reduction preparation of lithium metal. Decomposing lithium carbonate and extracting metallic lithium from lithium oxide by iron reduction process were theoretically analyzed and experimentally studied.Thermodynamics and dynamics of lithium carbonate decomposition process are analyzed and discussed, the law of lithium carbonate thermal decomposition in the vacuum system was also studied. Thermodynamic studies show that lithium carbonate is difficult to occur decomposition reaction at atmospheric pressure, however, under vacuum condition the reaction is easy to occur and increasing temperatures or reducing system pressure are conducive to the reaction. With the degree of the vacuum was improved, the critical reaction temperature is reduced. When the system pressure was10Pa orlPa, the critical decomposition temperature were reduced to964.15K and889.05K separately. The results show that increasing the decomposition temperature or extending the holding time can both improve the decomposition rate of lithium carbonate. Under the condition of3Pa and holding temperature at973K for210min, lithium carbonate decomposition degree can achieve about89.23%, and there is no liquid in this process. When temperature continued to be increased, the lithium carbonate continued to be decomposed and partial micro-melting appeared. When the temperature rose to1373K, the lithium carbonate was basically complete decomposed and the decomposition extend to99.9%. Between923-973K, the reaction steps was controlled by the interfacial chemical reaction, the apparent activation energy was128.456kJ/mol. In addition, Li5FeO4was appeared in decomposition slag, it is probability because the decomposition products in the crucible occured following reaction in the air:5Li2O(s)+2Fe(s)+1.5O2(g)=2Li5FeO4(s)Thermodynamics and dynamics were calculated and analyzed on extracting metallic lithium from lithium oxide by iron reduction process. The thermodynamic studies shown that it is difficult to occur reduction reaction at atmospheric pressure, however, when the system pressure less than10Pa and the temperature more than1558K, the extracting lithium by iron reduction process of lithium oxide in vacuum is feasible. With the degree of the vacuum was improved, the critical reaction temperature is reduced. When the system pressure reached to10Pa or1Pa, the critical reduction temperature were reduced to1558K and1426K separately. FeO was generated at first, then with temperature increasing, the reaction of FeO and Li2O generated Fe3O4followed, at a higher temperature Fe3O4with Li2O may be occur further reaction generated Fe2O3, but under the condition of pressure1～5Pa, temperature of1423-1573K, the reduction reaction only generates FeO and Fe3O4. Through the study of single factor and orthogonal experiments we deduced:temperature have greatest impact on the reduction rate followed by time, and then the excessive rate of iron, and finally the pressure, and the optimum process conditions were derived: temperature at1573K, reduction time150min,10%excess of Fe,7MPa pressure, under this condition lithium reduction rate can achieve74.1%. It was chemical reaction stage controlled the reaction between1473～1523K, then the chemical reaction and diffusion mass transfer stage together controlled the reaction in1573K, the apparent activation energy is345.161kJ/mol. There may be occurred following reaction: Fe2O3(s)+5Li2O(s)=2Li5FeO4(s) Fe3O4(s)+Li2O(s)=Li2Fe3O5(s) FeO(s)+Fe2O3(s)+Li2O(s)=Li2Fe3O5(s)In addition, LisFeO4was also appeared in reduction slag, it is probability because products in the crucible occurred following reaction in the air:5Li2O(s)+2Fe(s)+1.5O2(g)=2Li5FeO4(s)...