Research Of Desilication From Bauxite By Alkali Leaching Process

Bauxite as an important raw materials source of refractory, is facing an increasingly severe situation.Bauxite in high-grade is less and less, and the distribution is very deconcentrated. Most of the bauxite is a mixture of the high-grade and the low-grade, which can not be produced to excellent refractory by direct calcination. The reserve of low taste bauxite is relatively large.But it can only be produced to some low quality refractory.To solve this problem, different taste of bauxite were milled and homogenized for alkali leaching desilication. Removing some SiO2 would increase the content of Al2O3 correspondly, then the homogeneous bauxite can be obtained.Single factor test methods were used to research the effection of the roasting temperature, roasting time, alkali concentration, alkali leaching time, raw material fineness and added aid factors to desilication.The results showed that the optimum condition of the high-grade bauxite is:roasted at 1000℃for 120 min, alkali concentration is 150 g/L, alkali soaking time is 120min.The best test condition of the low-grade bauxite is:roasted at 1000℃for 90 min, alkali concentration is 150 g/L, alkali soaking time is 60 min. Bauxite can not be too fine, if not, it would not only go against the alkali leaching desilication, but also increase the production costs.Adding 4 g Na2SiO3·5H2O additive into each 100ml alkalilye is beneficial to desilication.Orthogonal experimental methods were used to research effection of the L/S (solution/bauxite), alkali leaching time, alkali leaching temperature to the low-grade bauxite. The optimum processing condition is:L/S is 10, alkali leaching time is 60min and the temperature is 95℃. Finally, after reaction of bauxite and NaOH, the liquid was analyzed and treated. Some silicon in bauxite reacted with NaOH, and formed sodium silicate.When a certain amount of CaO was added into the liquid at 90℃, the silicate in the liquid was completely disappeared after 5h, which transformed into calcium precipitation. After filtration and precipitation, all the solutions were NaOH solution, which could be recyclable after concentration test and adding NaOH to required concentration.