Effect Of Desilication Products In The Bayer Process On The Stability Of Sodium Aluminate Solution

With the increasingly fierce competition in alumina enterprises, the problem of aluminum acid sodium solution hydrolysis in the process of bayer increasingly serious, it also indirectly become one of the bottlenecks in the development of reducing energy consumption and cost savings of many production enterprises of alumina oxide.In this paper, research on the type and quantity of sodium aluminosilicate hydrate generated in the pure system of sodium aluminate solution under different reaction temperature, the type and quantity of sodium aluminosilicate hydrate, crystal morphology and calcium oxide added to the desilication product type, crystal morphology and the effect of hydrolysis,to provide effective theory basis and practice guidance for process of bayer to reduce the loss.The results are as follows:Under the condition of unadded calcium oxide,sodium aluminosilicate hydrate generated by different temperature of noselite and sodalite which can help to increase stability of sodium aluminate solution, the rise of temperature has a greater influence on the solid phase composition,and solid phase composition goes to a more stable phase;Sodium aluminosilicate hydrate generated by different temperature system contains sodalite and noselite, and under the condition of low temperature, noselite on promoting the stability of sodium aluminate solution is better than the effection of the role of sodalite, and noselite crystallinity increased also promote the stability of sodium aluminate solution;different alkali concentration of alkali reaction temperature carbon at145℃,make the main composition of solid phase different, carbonate root sodalite and noselite formed, the higher content of noselite,the better on the stability of sodium aluminate solution, when the reaction temperature rise to245℃, the resulting solid phase bases appear calcium nepheline, alkaline nepheline calcium and alkaline calcium stone, the more is the calcium nepheline in the solid phase, the better is for the stability of sodium aluminate solution. Under the calcium oxide added, the reaction time to generate solid phase three chinalco acid calcium had a greater influence on the crystallinity, the longer the crystallinity is higher, and as the extension of reaction time, tricalcium aluminate constantly to hydrate garnet, this is the most favorable to promote the stability of sodium aluminate solution. Temperature is also a decisive factor, from145℃to195℃,tricalcium aluminate phase disappeared, and from195℃to245℃, noselite disappeared, only leaves the hydrated garnet phase at245℃, thus we can draw the conclusion that hydrated garnet facies is all generated under the condition of different solid phase which is the most beneficial for the promotion of the stability of sodium aluminate solution phase.The increasing of the calcium oxide content which impact on solid phase is not obvious, main composition transformed the tricalcium aluminate into hydrate garnet, the increasing composition of hydrated garnet content is the key factors affecting the stability of sodium aluminate solution.The solid phase adding generated by the different temperature system with the calcium oxide added,the difference is the reaction mechanism, generated tricalcium aluminate first,then tricalcium aluminate generates into hydrate garnet.Adding calcium oxide and carbon alkali simultaneously at145℃, the amount of carbon base is advantageous to the generating of hydrate garnet,and when the carbon concentration of alkali rose to20g·L-1,the content of hydrated garnet reduced;When the temperature comes to245℃,comtrast to the test results of calcium oxide unadded, but the addition of calcium oxide generated solid to the direction of hydrate garnet,only the calcium nepheline which is more stable in solution,with the increasing of carbon concentration of alkali,the hydrated garnet content gradually reduced.