Basic Research On Preparing Mg By Vacuum Cu-Si Reduction

Vacuum thermal reduction and Electrolysis are the methods which preparemagnesium. Preparation of Mg using Vacuum thermal reduction was mainly process atpresent. Pidgeon in the Vacuum thermal reduction was widely applied. Pidgeon hassimple production process, good product quality and low production cost. However, italso has high resource consumption and long reduction cycle. These defects resulted inhigh cost preparing of Mg by Pidgeon and limited magnesium and magnesium alloysdevelopment rapidly.In this study, transmission phenomenon of vacuum thermal reduction Mg wasanalyzed and the new method which prepare of Mg using Cu-Si as reductant wasdiscussed. Analyzed on Cu-Si reduction for the preparation Mg in vacuum bythermodynamic analysis and the segregation phenomenon of mixed materials in theCu-Si vacuum reduction for the preparation Mg was explored. To realize differentrequirements in reaction stage and phase of which fluxing components were separatedand recycle in next experiment, the segregation velocity methods which regulatedmixed materials were proposed. Experiment research of preparation Mg using Cu-Sivacuum thermal reduction was done and metal magnesium was prepared. The methodwhich segregation separated slag and fluxing components was made full use of anddesalination experiment was done.①The characteristics of Cu-Si and Fe-Si alloy reductants were analyzed withCu-Si and Fe-Si phase diagram. The results indicate that Fe-Si is solid and Pidgeonreduction reaction of preparing for Mg is roughly solid-solid reaction when temperatureis about1373k; almost the whole process of the reduction can be solid-liquid reactionwhen temperature is about1373k and the initial Si content in Cu-Si alloy is less than35%.②The main reaction for Cu-Si reduction for the preparation Mg is2MgO（s）+2CaO（s）+[Si]_{Cu（l）}=2Mg（g）+2CaO·SiO2（s）. Under standard atmospheric pressure, thecritical reaction temperature for Cu-Si reduction of MgO is2390K The critical reactiontemperature is high and difficult to implement in the industry. In vacuum conduction,the critical reaction temperature decreases with reducing of system gas pressure andincreasing of Si content in Cu-Si. When Si content in Cu-Si is35%and system gaspressure is13.3Pa, the critical temperature of preparation of Mg using vacuum Cu-Si thermal reduction is1369K. At corresponding temperature （1473K） and system gaspressure （13.3Pa） of Pidgeon Process, the thermodynamics feasibility of Cu-Sireduction reaction is favorable which only needs Si content in Cu-Si alloy to be morethan0.034%wt.③Density difference of calcined dolomite and Cu-Si alloy melt in the Cu-Sivacuum thermal reduction exists in the mixed materials. Mixed materials weresegregated by the gravity. The segregation in the reaction process results in lowprobability of contact among reactants and deteriorates reaction process. Rapidsegregation of slag favors separation of slag phrase and fluxing components.Influencing factors of segregation in the mixed materials were analyzed and the methodof control segregation such as preparing reaction mixture materials of paste wereproposed, the corresponding experiment was done. The characteristics of fluxingcomponents and slag segregation were analyzed and corresponding experiment wasdone. The isolation rate of Cu is97%.④When vacuum degree is13.3Pa, temperature is1100℃by20℃/min speed,holding time is30min which is reaction time, the reduction rate of preparation of Mgusing Cu-Si vacuum thermal reduction is67.32%,however, the reduction time ofpreparation of Mg using Si-Fe vacuum thermal reduction is120min and its reductionrate is52.4%.The new method advantages which Cu-Si prepared for Mg by vacuumthermal reduction were more obvious than Si-Fe, in the production efficiency andresource utilization rate.