Study On Oil Soluble Organic Additive For Raising Seeding-decomposition Rate

The procedure of seed precipitation was the most time-consuming in Bayer process, and the efficiency of precipitation was far lower than that of theoretic. Therefore, seed precipitation became choke point in alumina production, and strengthen precipitation was the main method to solve the problem.Decreasing molecular ratio of sodium aluminate solution and purifying solution in order to remove organic compounds and other impurities were two ways to optimize seed precipitation process, but they were hard to achieve. How to adopt a new technique or method, finding an easy-to-operate and economical precipitation process to abbreviate process time, improving precipitation rate and advancing circulation rate had a great and obvious significance to alumina production.Oily organic was used as additive to optimize seed precipitation process and improve precipitation rate under the precondition of without changing process in this paper. H1-2 additive which adapts to Al2O3 production in our country was screened out from additive types of G, H and F and its adding methods was determined according to laboratory testing. The effect of H1-2 was further verified according semi-industrialization in 5 months.The effects of different additives were compared in experimentation of two-segment method and one-segment method in single tank, and in the experimentation of two-segment cycle. The results indicated that:The additive of series H could improve the precipitation rate.lOppm of H1-2 could improve the precipitation rate about 1.03%～3.9% in 15h and the granularity of Al2O3 did not change obviously; the additive of series G could improve the precipitation rate about 0.12%～0.91%, and increased the granularity of Al2O3 about 4.33%～12.55%; the additive of series F could not improve the precipitation rate obviously.The results of semi-industrialization experiments indicated that:When 10ppm H1-2 was put in at starting time,6ppm was put in at balance time and the temperature, solid-content and flux were the same, the precipitation rate was improved by 1.74% compared to blank, the intensity of Al2O3 was better, the attrition index was improved by 10.4% compared to blank and the granularity of Al2O3 was not changed obviously. At the same time, the additive did not make negative effect to Bayer process.