Alumina Carbon Thermal Reduction And Vacuum Chlorination Reaction Research

In this paper, the present situation and the development of aluminum production industry and the recent investigations of new process for aluminum production were generally discussed, in further the process of aluminum production by carbothermic reduction and chlorination of alumina under vacuum was studed systematically including aspects such as thermodynamic, mechanusm research and chlorination of reduction products by carbothermic reduction of alumina.The thermodynamic analysis of alumina cabothemic reduction indicated that in the process of alumina reduction, under conditions of1623K temperature and10Pa system pressure, Al(g) and Al2O(g) would be generated by reactions between Al2O3and C, so is this case when under conditions of1773K temperature and30Pa system pressure. Both under the conditions of1623K temperature and10Pa system pressure and1773K temperature and30Pa system pressure, the reactions between Al(g)/Al2O(g) and CO(g) or Al(g)/Al2O(g) and C can probably carry out. The product by the reactions between Al(g)/Al2O(g) and CO(g) mainly distribute in upper crucible due to the reactions tend to occur in lower temperature zone of crucible and the high temperature do harm to the proceed of the reactions. According to the distribution of temperature in crucible under experiment temperature of1623K or1773K, Al4O4C would just reacted with C in lower half part of crucible. The chlorinations of AI4C3å'ŒAl4O4can proceed under experiment conditions of1573K and50Pa.The mechanism study of alumina carbothermic reduction under vacuun show that aluminum was produced in experiment process when1623K and5-30Pa, aluminum product was condensate of intermediate product Al(g) or disproportionaion of intermediate product Al2O(g), CO was the key factor to whether aluminum product would generated in low temperature condensation tower or not. The reduction products mainly contained Al4O4C and Al4C3mostly distributed in the bottom of condensation tower, Al4O4C and Al4C3were produced by reactions between Al(g)/Al2O(g) and CO. The reactions between Al(g)/Al2O(g) and CO proceeded in the bottom of condensation tower, and condensate of Al(g) or disproportionation of Al2O(g) occurred in inner condensation tower. Al4O4C and Al4C3were produced by two steps,:first of all, Al2O3reacted with C to produce intermedia products; in second, Al4O4C and Al4C3were generated by the reactions between the intermedia products and CO, and CO was oxidant in this process. The initial reactions between Al2O3and C were reactions between solid and solid, the effective contact of solid phases played the most important role in this process. When abundant C exist, the reaction between Al4O4C and C was easily carried out to produce the final product Al4C3of carbothermic reduction of aluimna.In the process of aluminum production by carbothermic reduction and chlorination of alumina under vacuum, the chloriantion process was mainly the chlorination reactions of Al4C3and Al4O4C. When1573K and5-50Pa, Al4C3reacted with AlC13to produce AlCl and C, the generated C would wrap up the AI4C3to stop the proceeding of the chlorination reaction. AlCl would descompose into pure aluminum and AlCl3in condensation tower, and AlCl3condensate in top cap. Al4O4C reacted with AlCl3to produce AlCl, Al2O3and CO.The research on experiment parameter show the solid-solid reactions between Al2O3and C were the control step in carbothermic reduction of alumina under vacuum, roller mixing was beneficial to the proceeding of carbothermic reduction of alumina under vacuum. In the process of carbothermic reduction of alumina, experiment parameter would be chose as follow, material mass ratio of Al2O3:C=3, roller mixing, heated up to1693-1723K with heat preservation time of90min, chlorination proceeding time60min with reaction temperature1573K.