Method for modifying Bayer process, processing low-grade diaspore bauxite and producing alumina

Abstract

The invention provides a method for modifying a Bayer process, processing low-grade diaspore bauxite and producing alumina. The method comprises steps that: (1) silicon is chemically pre-removed, wherein the low-grade bauxite is immersed into a sodium aluminate solution containing a stabilizing agent, such that a slurry containing dissolved silica is obtained; (2) obtained high-silicon sodium aluminate solution is processed through desilication, wherein desilication crystal seeds are added to the slurry processed through filtration, such that desilication is carried out; (3) the sodium aluminate solution is processed through seed precipitation, wherein aluminum hydroxide crystal seeds are added to the sodium aluminate solution processed through desilication, such that seed precipitation is carried out; (4) the obtained aluminum hydroxide product is baked, such that an alumina product is obtained; (5) a high-pressure dissolution process is carried out, wherein the obtained seed precipitation mother liquor is processed through evaporation and alkali supplementation, and is used in high-pressure dissolution of a concentrate obtained in the step (2); a stabilizing agent is added to the obtained sodium aluminate solution, the sodium aluminate solution is then used for processing the next batch of bauxite, and the steps (1) to (4) are repeated. The method provided by the invention is suitable to be used for processing low-grade diaspore bauxite. With the method, a silicon scaling problem in alumina industries can be effectively solved, energy consumption can be substantially improved, and the quality of the finished product alumina can be improved.

Description

technical field [0001] The invention relates to the field of bauxite treatment, in particular, the invention relates to an improved Bayer method for processing low-grade diaspore bauxite to produce alumina. Background technique [0002] At present, in the production of alumina, there are mainly Bayer method, sintering method and hybrid method to realize industrial production. Among them, the Bayer method has the advantages of low energy consumption, simple process, and low production cost. However, the production of alumina by the Bayer method has strict requirements on raw materials. Generally, the aluminum-silicon ratio is required to be greater than 8, and it is especially suitable for Sanshui with a high aluminum-silicon ratio. Alumina production from bauxite raw materials. And more than 80% of my country's bauxite is aluminum-silicon ratio (Al in bauxite 2 o 3 and SiO 2 mass ratio) 4-8 middle and low-grade diaspore type, due to the high silica content of this bauxit...

AI Technical Summary

Problems solved by technology

However, the alkali concentration used in the high-pressure hydrochemical part of the method is relatively high, the liquid-solid separation is relatively difficult, and the process is relatively complicated and difficult to operate.

[0009] When dealing with low-grade diaspore-type bauxite ore in the prior art, either the energy consumption is high, the process is complicated, the cost is high, and the product quality is unstable, or the recovery rate of alumina is low due to the addition of chemical reagents. And cause a large amount of tailings to be unusable, or the concentration of alkali used is high, making liquid-solid separation more difficult, the process is relatively complicated, unfavorable operation, etc.

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