The effects of magnetic field intensity,roasting temperature and roasting time on digestion rate and settling performance of bauxite with different iron contents were investigated systematically.The results indicate that such magnetic treatment can profoundly change the microstructure and digestion performance of bauxite.For the two samples carrying different iron contents,phase transformation of the aluminum oxide phase proceeds faster in the high iron bauxite than the low one.The optimal pretreatment conditions of low iron bauxite are roasting temperature 550 °C and magnetic field intensity 6 T,while for high iron bauxite are 500 °C and 9 T.The digestion rate of alumina can reach 95% and 92% at digestion temperature of 190 °C and 250 °C.The settling performances of roasted ore by intense magnetic field after digestion are enhanced through pretreatment.
The mixer-settler is a core device of solvent extraction for separating rare earth elements. There are some adverse effects like high rare earth accumulation and poor production efficiency during industrial production. Current researches usually focus on changing the structure of the mixer-settler without making a breakthrough towards gravity clarification. In this paper, in order to improve the efficiency of clarification, a mixer-settler with double stirring mode was designed and manufactured by adding a stirring device in the settler after reducing the volume of the settler. The innovation of this research involves adopting the ultraviolet-visible spectrophotometer to investigate the quantity of aqueous phase entrainment at the settler outlet in order to measure the clarification degree. Experimental results show that the clarification effect with stirring is better than that without stirring. The clarification effect is ameliorated as the stirring speed increases. Generally, the clarification effect shows a best condition when the offset distance is 12.5 cm, making the phase entrainment reduced to less than 0.1%. When the clearance over the tank bottom is 7 cm and 10 cm, respectively, the quantity of aqueous phase entrainment is better than the case with a clearance of 4 cm. The results show that the stirring paddle close to the mixed phase zone can better promote the two-phase separation.
Wang ShuchanZhang TinganZhao QiuyueLiu YanWu Qiuyang
The effects of pyrolysis mode and pyrolysis parameters on Cl content in alumina were investigated, and the alumina products were characterized by XRD, SEM and ASAP. The experimental results indicate that the spray pyrolysis efficiency is higher than that of static pyrolysis process, and the reaction and evaporation process lead to a multi-plot state of the alumina products by spray pyrolysis. Aluminum phase starts to transform into γ-Al2O3 at spray pyrolysis temperature of 600 °C, which is about 200 °C lower than that of static pyrolysis process. The primary particle size of γ-Al2O3 product is 27.62 nm, and Cl content in alumina products is 0.38% at 800 °C for 20 min.
