The Bayer Process Reduces The Red Mud N/S Study

In the production of alumina with Bayer process,alkali consumption is an important technology economic index for evaluating the economic benefits,which reflects production technology and management levels of an enterprise.High sodium silica ratio(N/S)in red mud is the main reason for the high alkali consumption in Bayer process.Therefore,the object of this paper is to investigate the dissolution conditions in Lime Bayer process,which is hoped that the findings will guide the optimization of production technology in a demestic alumina enterprise.In this paper,the influence of different additives on the sodium silica ratio(N/S)in red mud was analyzed,which helps to find an appropriate additive for reducing the alkali consumption and increasing the dissolution rate of alumina in the production.The following aspects are carried out in this paper.First,the bauxite dissolution was studied by Lime Bayer process in China.The experiment was carried out by changing the content of lime(C/S),stirring intensity,liquid solid ratio,particle size,reaction time,the concentration of sodium carbonate,the ratio of aluminum to silicon and the content of trace elements in mother liquor.The results showed that the dissolution rate of alumina reached more than 95%,the N/S of red mud was reduced to 0.32 and the A/S of red mud was about 1.3,which attained to the enterprise outside standard,when the conditions were temperature was 265℃,adding lime dosage was C/S＝1.3,the ratio of liquid to solid was 3.8,the particle size was less than 0.074 mm ore accounted more than 90%,the stirring speed was 500 r/min.Then,magnesium oxide,dicalcium ferrite,calcium ferrite hydrate,calcium ferrite hydrate prepared by red mud were selected to replace the lime by Bayer process.The results showed that the Magnesium Oxide had no effects on reducing N/S of red mud,and adding Magnesium Oxide too much would reduce the dissolution rate,with dicalcium ferrite instead of lime,adding a small amount of dicalcium ferrite to reduce red mud N/S is not obvious,but the dissolution rate remained at a high level,when the amount of dicalcium ferrite was increased to C/S=2.0,the N/S of red mud was decreased to 0.28.the effect of using calcium ferrite hydrate completely replacing lime to reduce N/S of red mud and increasing the leaching rate of alumina was effective,when the amount of calcium ferrite hydrate was added by C/S = 1.75,N/S of red mud could be reduced to 0.26,alumina dissolution rate was 94.16%.The preparation of hydrated calcium ferrite from red mud iron ore was also effective in reducing N/S of red mud.By analyzing the composition of the slag,the change of the red mud phase was the reason for the increase of the dissolution rate of alumina.The optimization of production technology and the development of new additives provide reference for energy saving and emission reduction.