Technique for processing bauxite to produce hydroted alumina with sodium hydroxide molten salt growth method

Abstract

The invention relates to a process that the sodium hydroxide molten salt method is adopted to treat the bauxite to produce the aluminium hydroxide, which comprises that the sodium hydroxide solution blended evenly and the bauxite are heated to carry out the molten salt stripping reaction; the stripping grog is leached and the red mud is separated to gain the sodium aluminate solution which carries out deep desilication; the sodium aluminate solution seeds are decomposed to gain the aluminium hydroxide crystal and seeded precipitation spent liquor; the seeded precipitation spent liquor is evaporated and crystallized and the crystallized mother liquor returns to the molten salt stripping step; the sodium aluminate crystallization returns to the seeded precipitation step after dissolved by adding water. The invention has the advantages that: the digestion temperature is 500 DEG C. to 800 DEG C. lower than that of the traditional sintering method, which can greatly reduce the energy consumption; the invention is operated under normal pressure with simple flow and convenient operation; the invention can process middle-low grade-diasporite bauxite, which conforms to the realistic need of aluminium oxide development in our country; the dissolving rate of the aluminium oxide is high; any accessories are not added and the red mud amount is small, thereby the sodium loss and the aluminum loss are small and valuable metals inside are easily recycle; the product has good quality.

Description

technical field [0001] The invention belongs to the processing field of bauxite, and in particular relates to a process for processing bauxite with sodium hydroxide molten salt method to produce aluminum hydroxide. Background technique [0002] As the main raw material of electrolytic aluminum, the alumina industry occupies a very important position in my country's national economy. More than 98% of my country's bauxite is diaspore type bauxite. At present, the methods of processing bauxite in my country mainly include Bayer method and sintering method. [0003] The technological process of the Bayer method is: after the bauxite is crushed, it is ground with lime and the evaporated mother liquor to make a raw ore slurry, which is dissolved at 240-280°C and a pressure of 3.7-6.5MPa. The dissolved slurry is diluted with red mud washing water, and then the sodium aluminate solution is separated from the red mud in a settling tank, and the red mud is washed and then discharged...

AI Technical Summary

Problems solved by technology

[0007] The purpose of the present invention is to overcome the prior art when processing bauxite to produce aluminum hydroxide or aluminum oxide, or the raw materials used are limited, or the high reaction temperature leads to high energy consumption, complicated process, high cost and poor product quality. Unstable, or the high concentration of alkali used makes liquid-solid separation more difficult, the process is relatively complicated, unfavorable operation, or the inhomogeneous direct mixing of bauxite and sodium hydroxide molten salt will affect the dissolution rate of alumina , and causticization of lime is likely to cause defects such as loss of sodium hydroxide, so as to provide a simple process, high utilization rate of alumina, no need for high temperature and high pressure equipment, low investment, easy to operate sodium hydroxide molten salt method to process bauxite to produce hydrogen Alumina process

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