Sodium Silicate Wet Processing Technology Research

The key question during the process of alumina production lies in the separation of aluminum and silicon where the silicon is precipitated as the form of sodium hydrate alumino-silicate called sodium-silicon slag hereunder. The slag is the major reaction product of silicon mineral when processing the bauxite by the alkali treatment. The traditional sintering process recovers aluminate and sodium oxide by the method allowing the slag flow back into sintering system for batching, but a large amount of slag and its liquor back into system form a void internal cycle, which lowers the actual capacity of the sintering process and increases production cost with increased various consumption. High pressure hydration treatment and hydrothermal treatment have disadvantages in economic due to their high temperature, high a_k and alkali concentration,Therefore, a new short flowsheet wet treatment process must be exploited. The paper describes its study direction such as the following :a)Putting lime into the slag to remove alkali by transformation of the sodium-silicon slag into hydrate garnet ,then effects the recovery of alkali. It alsoshows the effect rule of temperature, molecular ratio of [CaO]/[Na₂O] , time and L/S ratio on the removal of alkali. The feasible condition for the alkali recovery are as follows: temperature 80¹00℃, L/S ration 5, molecular ratio of [CaO]/[Na₂O] 3-4, reaction time 2 hours;b ) investigating effect of the addition way and concentration of the additives, modification times, temperature, L/S ratio, time, concentration of alkali liqour and sodium aluminate on the transformation of the slag without alkali. The feasible conditions for transformation are 8¹00% R concentration, time 2h, 5¹0 L/S ratio, 50℃ temperature and one time modification;c) studying the effect of alumina digestion time , caustic concentration, L/S ration, soda concentration on alumina digestion in the process of alumina digestion after the slag transformation. The feasible conditions for alumina digestion are: about 50℃ temperature, 1h time, approximately 10 L/S ratio, 50¹00g/L caustic alkali concentration;d)The resulting experiment indicates that the alkali recovery ratio can reach about 90% and more than 50% during the recovery of alumina, which render the A/S ratio less than 0.6 and N/S ration less than 0.2 in the abandoned residue;e)The expanded field tests of the sodium-silicon slag wet treatment have a good agreement with the experimental results;f)The application of this new wet treatment on alumina production will have a better economical and social efficiency, thus it will be widely expanded and applicated;f) It puts forward principled process flowsheet of the wet treatment with sodium-silicon slag.