Alumina Product Particle Size Of The Main Factors And Particle Size Control Model

Seeded precipitation of sodium aluminate solution is an important process for alumina production. The promotion of Gibbsite precipitation from sodium aluminate solution is always a hotspot on investigating of seeded precipitation of sodium aluminate solution. How to strengthen the seed decomposition process, and to raise the rate of dissociation and the product particle size of aluminum hydroxide has the important meaning to the development of aluminum industry in our country.The influence of three kinds of different generation polyamidoamine on surface tension and the seed precipitation of sodium aluminate solution have been investigated. It has shown that surface tension of sodium aluminate solution to PAMAM was determined through the biggest bubble method. According to the surfactant nature of the interface, we can accurately obtain the critical micelle concentration of 1.5G, 2.0G, 2.5G PAMAM: 1300mg/L, 250mg/L, 175mg/L. PAMAM is a non-ionic surfactant. It not only can improve the seed precipitation of sodium aluminate solution, but also can obviously increase the volume percentage of +45μm particles of Al(OH)₃ products. When concentration of 2.5G PAMAM reached critical micelle concentration, the effect to precipitation ratio was maximal. And the effect on product size distribution was also the most notable.The multivariate linear fitting of data of seed precipitation of sodium aluminate solution was performed with MATLAB software according to the point of view of investigating rate constant of agglomeration process of the seed precipitation of sodium aluminate solution yield. The influence of molecular ratio, caustic alkali concentration, temperature and seed load on rate constant of agglomeration process of the seed precipitation of sodium aluminate solution have been investigated. In the applicable scope, molecular ratio, caustic alkali concentration and reaction rate constant have become the linear relationship. The molecular ratio and caustic alkali concentration should not be too high. It has shown that with increase of molecular ratio and caustic alkali concentrations, reaction rate constant reduces gradually. Conversely, the high temperature and the large seed load help to increase the reaction rate constant. A quantitative relationship between reaction constant and molecular ratio, caustic alkali concentration, temperature and seed load have constructed through the multivariate linear regression equation. Herein, K= -5.7918×10³a_k -5.05×10^-5 N_k+9.60×10^-5T+2.37×10^-5m -0.0172132. The formula not only can predict precipitation ratio and seed load, but also can explain importance of temperature decrease system theoretically.The changes of the relative supersaturation, precipitation ratio, the product particle size distribution and reaction rate constant of the seed precipitation of the sodium aluminate solution under different temperatures have been investigated. The results have shown that from 50℃to 75℃relative supersaturation of the sodium aluminate solution decreased as temperature gradual increased. Average particle size and reaction rate constant increased with the gradual increase of temperature. Aluminum sodium precipitation ratio reached the maximum at 65℃. In addition, the precipitation ratio of sodium aluminate solution was 28.86% at temperature decrease system. However, the precipitation ratio of sodium aluminate solution was only slightly lower than the one at 65℃. The product particle size under this condition was larger than the one at 65℃. Seed precipitation at temperature decrease system not only ensured larger seed precipitation ratio, but also improved the product particle size.