Method for expelling carbonate in production of aluminum oxide

Abstract

The invention relates to a method to exclude carbonate in the production process of aluminum oxide, which relates to a technological method producing aluminum oxide with the Bayer process. The method is characterized in that: the liquid caustic which is required in the production process of aluminum oxide with the Bayer process is directly added into the salt draining settling tank, the settled bottom stream is solid-liquid separated into carbonate and the evaporation alkali liquor; the solid obtained by the separation is dealt with the causticizing process or the sintering process to produce aluminum oxide; the liquor obtained by the separation and the overflow of the settling tank are added into the mother liquor tank together, and then is circularly lye allocated. By using the invention, the liquid caustic with normal temperature high caustic sodium concentration is added into the salt draining settling tank, the temperature of the solution in the settling tank is reduced, the caustic sodium concentration of the solution is improved, and the separating speed for the carbonate crystallization is accelerated. The liquid caustic, the overflow of the settling tank and the evaporation mother liquor are mixed into the mother liquor tank, and during the circular lye allocation, only the flow of the evaporation stock solution and the mixed mother solution is calculated and regulated, ,the technological process by using the circular lye allocation with the Bayer process is simplified, the operation of the lye allocation is more convenient and exact.

Description

Technical field [0001] A method for eliminating carbonates in alumina production relates to a process method for producing alumina by the Bayer process. Background technique [0002] The NaO in the sodium aluminate solution in alumina production includes sodium hydroxide (commonly known as caustic alkali), NaOH, and sodium carbonate (commonly known as caustic alkali) Na 2 CO 3 , Sodium sulfate Na 2 SO 4 Wait. For the production of alumina by the Bayer process, only OH- in NaOH can dissolve alumina in bauxite to obtain sodium aluminate solution. Sodium carbonate not only increases the circulating liquid volume of the system, but also causes the solution to evaporate or dissolve. During the flash evaporation process, crystallization will block the pipeline, which will interrupt the production process in severe cases. [0003] Due to the introduction of raw materials such as bauxite and lime, the decausticization reaction in the dissolution process, and the CO in the air brought int...

AI Technical Summary

Problems solved by technology

The disadvantage is that when the mother liquor is evaporated and directly enters the bag filter, the solution temperature is high, and the amount of crystallization of carbonate is small, so that a large amount of sodium carbonate remains in the solution, and the effect of salt removal is poor.

In the production operation, it is necessary to calculate and adjust the flow ratio of the three solutions of the evaporated stock solution, the evaporated mother liquor and the liquid caustic soda for the deployment of circulating lye, which is difficult to control the production

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