| Aluminum is the only second important metal to the iron and steel in the world, which has played an important role in the national economy. It has been widely used in agriculture, machine, light industry, petroleum chemical, metallurgical industry, military, transportation industry and aerospace, also widely used as architecture structural materials, family life appliance and sports goods. This article gives a general comment on the following points: the usage and properties of aluminum, various production methods, the bauxite resources around world and the recent research for new production methods. The mechanisms, thermodynamic and process for aluminum production by alumina carbothermic reduction chlorination in vacuum have been investigated, as many problems exist in the aluminum production by Hall-Heroult which can not be solved completely.Experiments have been carried out by using analytical chemical agents as raw materials, AlCl(g) was generated by the system of AlCl3(g)-Al2O3-C at high temperature, which will disproportionate into aluminum and AlCl3(g,s) while it entered low temperature zone, and aluminum and AlCl3(g,s) would be condensated in different zones, respectively, as the difference of the condensation temperature of those.Thermodynamic calculations indicate that the preferential order of products is Al4O4C>Al4C3>Al2OC>Al2O>Al between the system of alumina and carbon while under 100Pa, temperature for Al4O4C and Al2OC transformed into Al4C3 should be 1726K and 1701K, respectively. Temperature for aluminum generated by Al2O3-Al4C3 and Al4O4C-Al4C3 should be 1879K and 1889K, respectively. Temperature for AlCl(g) generated by carbothermic-chlorination process among Al4O4C, Al4C3, Al2O3, C and AlCl3(g) should be below 1502K, and temperature for Al2OC participated in carbothermic chlorination process should be higher than 1853K. Initial temperature for aluminum produced by AlCl(g) disproportionate should be 950-1050K while at 101-102Pa. AlCl(g) disproportion process is a capacity reduction reaction, so the larger the system pressure is, the more beneficial foe AlCl(g) disproportion to carry out.Mechanism analysis for aluminum production by alumina carbothermic-chlorination shows that Al4O4C and Al4C3 begin to generate over 1693K under 50 to 100Pa, and the contents of those are increased with the temperature increasing. Al2O3 and Al4O4C will be transformed into Al4C3 with temperature continued to increase or system pressure down. Carbothermic-chlorination process shows that reactions occurred among Al2O3, Al4O4C, Al4C3, C and AlCl3(g) but not only among Al2O3, C and AlCl3(g) while at 70-180Pa and 1703-1853K. AlCl(g) disproportionate into Al and AlCl3(g,s) while it entered low condensation zone that below 933K, and Al metals were easily carbonized into Al4C3 by C at higher temperature zone.Process analysis for aluminum production by alumina carbothermic-chlorination shows that it is beneficial for the process of carbothermic and chlorination to continue when reactant weren't melted and sublimation hole wasn't blocked under that conditions: temperatures of carbothermic and chlorination were no higher than 1763K at 50-100Pa, sublimation rate of anhydrous-AlCl3 was below 0.32g/min, molar ratio of C and Al2O3 was 3:1, carbothermic and chlorination time were 40min and 40-50min, respectively. Effect of Fe2O3, SiO2 and TiO2 on aluminum production by that process have been investigated under above optimum conditions, the results indicated that Al direct collection attained 72.09% while added 10.0%Fe2O3, molar ratio of C and Al2O3 was 4:1 at 1713-1723K. Al direct collection and reactant weight loss rate were obviously lower than that of added 0%SiO2 at 1753-1763K when added 2.5%-15.0% SiO2. Al direct collection attained 82.38%, the purity of which was higher than 94.67% while added 10.0%TiO2, molar ratio of C and Al2O3 was 4:1 at 1753-1763K. |
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