Method for extracting alumina from bauxite

Abstract

The invention discloses a method for extracting alumina from bauxite, which is suitable for extracting the alumina from various and different ore mineral types of bauxites. The method comprises the following steps: mixing and grinding the crushed bauxite and sodium carbonate according to a certain proportion, and then obtaining high-purity alumina through roasting, circular leaching, sedimentation-filtration, carbonization, additive recycling, washing, calcinations and the like. In the whole production process, the generated carbon dioxide and the used additive can be recovered and reused. Compared with the Bayer process and other methods for producing the alumina, the method has the advantages of low requirement on the grade of the alumina from the bauxite, low requirement on the aluminum-silicate (A/S) ratio, no limitation to the type of minerals, high extraction rate of the alumina, low energy consumption, more succinct process, no special requirements on the equipment, lower cost and the like, thereby easily realizing industrialization.

Description

Technical field: [0001] The invention belongs to the field of metallurgy and chemical comprehensive production, in particular to a method for extracting alumina from bauxite. technical background: [0002] With the continuous development of human society, the demand for aluminum resources is also increasing. At present, with the development of the alumina industry, there has been a serious shortage of bauxite resources, especially high-quality bauxite resources. At present, the contradiction between the supply and demand of bauxite is very prominent, especially in my country, most of the mines are seriously depleted in ore grade to varying degrees, and the high-grade or high-aluminum-silicon ratio bauxite in most major mining areas is even on the verge of depletion. Facing the current situation that high-grade or high-quality bauxite resources with high aluminum-silicon ratio are increasingly scarce, the existing alumina production technology is facing serious challenges. H...

AI Technical Summary

Problems solved by technology

In the above-mentioned existing various methods, except the Bayer method, there are serious defects: either the energy consumption is too high, and it is difficult to obtain benefits (techniques such as soda lime sintering method, lime sintering method and microwave aiding dissolution method); If the extraction rate is too low, it is also difficult to obtain benefits (non-high temperature method); or the amount of slag discharge is too large, resulting in excessive solid waste discharge, which seriously pollutes the environment, and fundamentally, it is still difficult to obtain benefits; or the process is long and complicated , a large number of equipment, a lot of operating processes are mutually restrained, and there are problems such as high energy consumption and high cost (combined method, etc.); or the additives used are too corrosive to the equipment, and the recovery of the auxiliary acid is difficult and it is easy to cause pollution to the environment. A series of fatal shortcomings have seriously affected the promotion of its industrialization (acid leaching method, ammonium fluoride aiding method, ammonium sulfate sintering method, etc.)

[0004] Compared with other existing methods, although the Bayer process is relatively simple, the investment and energy consumption are relatively low, more than 90% of alumina is produced by the Bayer process, but the serious disadvantage of this method is that it is only suitable for high Processing of gibbsite-type bauxite with aluminum-silicon ratio

Among all kinds of bauxite resources in my country, diaspore accounts for more than 98% of the total reserves, especially most of them have high SiO 2 The outstanding characteristics of the content, the use of the Bayer method is greatly restricted

[0005] In addition to the above, Alkali fusion of soda ash and bauxite raw materials was first invented by the French chemist Satri in 1858 to extract Al 2 o 3 The technology - soda ash sintering method, due to the alkali fusion process, SiO 2 and Al 2 o 3 with Na 2 CO 3 The reaction produces a large amount of insoluble sodium aluminosilicate (Na 2 O·Al 2 o 3 2SiO2 2 ) solid, not only makes Al 2 o 3 The extraction rate has dropped significantly, the quality of the extracted alumina is poor, and a large amount of raw material soda ash Na 2 CO 3 to Na 2 O·Al 2 o 3 2SiO2 2 Na in solid 2 O, cannot be released for recycling, so Al 2 o 3 Extraction costs have risen substantially

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