A method for multi-stage hydrogen peroxide to remove organic matter in alumina production process

Abstract

The invention discloses a method for removing organic substances in the aluminum oxide production process with hydrogen peroxide through multiple stages. The method comprises the following steps that firstly, leach liquor is injected into bauxite, aluminum oxide in the bauxite is leached, and a seed pregnant solution is obtained; secondly, the content of organic substances in the seed pregnant solution is measured, and the total volume V of hydrogen peroxide needed for a reaction is calculated; thirdly, 50-70%V of hydrogen peroxide is added into the seed pregnant solution, a reaction is carried out, and a solution obtained after the reaction enters an evaporation stage; fourthly, 20-40%V of hydrogen peroxide is added into an evaporation mother solution, a reaction is carried out for 1-60 min, and a solution obtained after evaporation of the evaporation mother solution serves as leach liquor to be recycled; fifthly, 5-15%V of hydrogen peroxide is added into the recycled leach liquor, and then the steps are repeated. According to the method, H2O2 is added into a sodium aluminate solution and can make full contact with the sodium aluminate solution; besides, H2O2 has the oxygenolysis feature and can remove organic substances under the normal pressure conditions, and the running pressure of equipment is reduced; the method has the advantages of being small in energy consumption, high in efficiency, low in cost and free of pollution.

Description

technical background [0001] The invention relates to a method for removing organic matter in the production process of alumina, in particular to a method for removing organic matter in the process of producing alumina by the Bayer process with multi-stage hydrogen peroxide. Background technique [0002] The production of alumina by the Bayer method is to dissolve bauxite with NaOH solution in a high-pressure stripper at high temperature, and then dissolve the alumina to obtain a sodium aluminate solution, and the impurities enter the residual red mud. A seed crystal is added to the separated sodium aluminate solution, and the seed crystal is decomposed under the condition of constant stirring to precipitate aluminum hydroxide. The decomposed mother liquor is returned to dissolve the next batch of ore. The product alumina is obtained after aluminum hydroxide is burnt. [0003] Sources of organic matter in the production of alumina by the Bayer process: (1) Bauxite: Bauxite ...

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Problems solved by technology

And the viscosity of the solution increases during the circulation production process, which is not conducive to the sedimentation, separation and filtration of aluminum hydroxide

[0006] (2) Loss of alkali: organic matter in the solution reacts with alkali to generate various organic sodium salts, causing alkali loss

[0007] (3) The organic matter makes the particle size of sodium carbonate monohydrate precipitated during the evaporation process of the decomposed mother liquor finer, which makes sedimentation and filtration separation difficult, and the higher the organic matter content, the more serious the harm

[0009] (5) Affect dissolution: Sodium oxalate and sodium acetate will slow down the dissolution rate

Moreover, the co-precipitation of sodium oxalate and alumina accelerates the scarring speed of equipment such as seed separation tanks and evaporators, which brings many problems to production.

[0010] (6) Affect the decomposition of crystal seeds: With the increase of the concentration of organic matter, the decomposition rate of crystal seeds decreases, the particle size of aluminum hydroxide becomes finer, and it is easy to break during the roasting process of aluminum hydroxide, and the viscosity of the decomposed slurry increases. Adsorbed organic matter, slightly reddish brown, affecting the quality of alumina (aluminum hydroxide)

But colloidal hydroxide precipitates are difficult to separate and contain aluminum, causing loss of aluminum

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