Experimental Study On Pre-desilication From Low Grade Bauxite By Suspension Roasting-alkali Leaching Process

By suspension roasting-alkali leaching process,the kaolinite in bauxite is decomposed by calcination to form amorphous silica and loose aluminum-silicon spinel,and then through the alkali-doped desilicon,can effectively improve the diaspore-kaolinite low-grade bauxite of the aluminum to silicon ratio（A/S）.In this paper,a low grade bauxite sample from a place in Henan Province is studied.The suspension experiment was carried out by using a rapid reactor in a suspended state,and the roasted ore was subjected to mineral phase analysis and alkali desilication test,The optimum extraction conditions of roasted ore were determined by the difference（interaction）and variance method,all of these are Based on the study of mineral analysis and thermodynamics.Besides,the parameters of the kinetics equation of the alkali leaching of the suspended ore were obtained by the kinetic study,and the relationship between the alkali leaching temperature and the desilication rate was determined.The results of the trial study are as follows:The suspended state roasting test results show that the suspended state rapid roasting has a significant effect on the activation of silica in montmorillonite-kaolinite low-grade bauxite,and also improves the activity of alumina.The kaolinite was transformed into amorphous silica and loose aluminum-silicon spinel in the temperature of 1030±5℃.Silica is more easily leached in the lye in the two substances.The single-factor test,orthogonal test extreme（interactive）analysis and orthogonal test analysis of variance analysis showed that the main influencing factors of desilication of roasting ore were alkali leaching temperature,alkali leaching concentration and liquid.In addition,the alkali leaching time and the stirring speed have some influence on the desilication rate,the alumina loss rate and the increase of A/S.The interaction effect between alkali leaching conditions is not obvious.Considering the high liquid-solid ratio will lead to the production process of the recycle lye is too large,combined with orthogonal test（orthogonal）and orthogonal test variance analysis results,the optimum alkali leaching conditions are A4B1C4D1（T=100℃,t=30min,c=125g/l,l/s=4ml/g）under the test conditions.The kinetic analysis of alkali leaching shows that The leaching process of suspended ore is controlled by the diffusion of solid film,and its kinetic equation is: t2=k_nks[1-2η/3-（1-η）2/3],Its activation is 19.86kJ/mol;Under the conditions of alkali leaching concentration of 150 g / l,liquid to solid ratio of 4,stirring speed of 200 r / min and leaching temperature of 95 ℃,the alkali leaching temperature and the desiliconization rate basically meet the relationship: y=u（x）=-121.22+3.10×T-0.012×T².