Study On Reduction Performance Of Iron Oxide In Iron-bearing Bauxite Residue Produced By Calcification-carbonation Process

With the rapid development of China’s alumina production,China’s high-quality bauxite reserves have been difficult to meet current industry requirements.The efficient use of large reserves of low-grade and high iron complex bauxite resources attracts more and more attention from the industry and academia.Our team proposed a calcification and carbonization method for producing alumina from high iron bauxite:(1)dissolution the bauxite and restructuring the entire silicon into calcium aluminosilicate(2)carbonizing the calcified residue by CO2(3)extraction the iron from the carbonized residue at low temperature after alkali dissolution.This method breaks the shortage of counterweight of Na,Si and Al in the Bayer alumina production process,which can make the content of Na and Al tends to zero in theory and also can be directly used in cement industry.The structure of the new red mud is calcium and carbonate,which can achieve a harmless red mud.Based on the resource of high iron bauxite from Wen Shan aera,Yun Nan provience,China,the reduction properties of iron in the low temperature dissolution residue and the separation behavior and characteristics of iron in the calcification and carbonization method were researched.Through the theoretical study of pure substance,the new method and the scientific issues of the iron contained phase transition in the reduction process were studied.The research of paper may provide a necessary theoretical basis for the efficient and clean use for the high iron bauxite.The main content of this paper are:(1)The results of thermodynamic calculation for the calcification-carbonization transition and reduction process indicate that:higher temperature will promote the transition of calcification,the temperature of carbonization should be low and the effect of CO2 pressure on the reaction is little.when the excess CaO is added into calcification process,it can play a alkaline role in the reduction process.The iron olivine and iron spinel phase are destroyed,and the reduction of ferrous oxide into iron meta is promoted.(2)After the synthesis of iron garnet hydrate,the reduction process of iron in the carbonized residue was studied.The results show:when calcification temperature is between 200 to 280 ℃ it can generate a stable iron-based garnet.After the Carbonation and dissolution of aluminum,it can decompose into iron oxide and hydrated garnet.The results of iron reduction showed that:under the condition of 1h,1050℃ reduction temperature,260℃calcification temperature,the iron reduction rate can be up to 77.2%for the residue,and the main phase is metallic iron,calcium hydroxide and aluminum silicate.(3)The directly reduction process of the red mud from high iron bauxite dissolution was researched.The results show:the dissolution rate of A1 by Bayer alumina production process for the raw material.The reduction rate was 75.8%at 1050℃ reduction temperature and the main phase was metallic iron,sodium silicate and sodium silicate sodium.(4)The reduction process of iron in the calcified and carbonized residue was researched,and the results show that:the dissolution of aluminum is 83.67%for the high iron bauxite after the calcification and carbonization method,which is much higher than that of Bayer process.The reduction process of iron in the residue shows that:the metallization ratio is 80.5%for 2h at 1050℃,which is a bit higher than that of Bayer process.(5)The effect of reduction iron from red mud and residue is obvious when the sodium carbonate is added.The metallization ratio is 93.6%for the calcified and carbonized residue for 1h at 1050℃,which is higher than that of 86.7%from red mud.