Method for producing aluminum oxide by Bayer process

Abstract

The invention discloses a method for producing aluminum oxide by a Bayer process and relates to improvement of increasing slurry concentration with back feeding bauxite digestion technology during an aluminum oxide production process. The method is characterized by comprising the following steps: adding gibbsite-type bauxite to a flash evaporation process; increasing Rp of the digested bauxite slurry after the convergence to 1.30-1.35; adding decomposition mother liquor or flat plate washing liquor with Rp of 0.10-0.60 in the dilution process; reducing the Rp of the crude liquor to 1.15-1.18; and refining the crude liquor. In the method provided by the invention, a method of adding alkali after bauxite sweetening is adopted, thus the solid content of back feeding bauxite is effectively increased; and as the alkali liquor is added after the digestion, so that the amount of the alkali liquor involved in the back feeding bauxite digestion is remarkably reduced, and the bauxite slurry reduced ratio of a back feeding bauxite system is effectively reduced, thus the steam consumption of the back feeding bauxite digestion is reduced. Through the invention, the capacity of a single system of the Bayer process can be further increased, a system of the Bayer process is maximized, the power consumption and the evaporation steam consumption are reduced, and the high-quality operation of the system is maintained; and besides, the sustainable stable operation of the high-yield situation is ensured while the system capacity is increased.

Description

technical field [0001] The invention discloses a method for producing alumina by the Bayer method, which relates to the improvement of the post-adding ore-enriching and stripping process in the alumina production process. Background technique [0002] In the process of producing alumina by Bayer method, the gibbsite-type bauxite is treated by post-adding ore-enriching and leaching technology, which can make the leached pulp Rp (Al in sodium aluminate solution 2 o 3 with Na 2 The mass ratio of O) is increased from about 1.10 to more than 1.30. The experiment shows that adding imported gibbsite bauxite can dissolve Na 2 The equilibrium Rp that can be achieved when the 0k concentration is 180~220g / l is 1.30~1.36. However, in the follow-up production process, the crude liquid Rp that can pass through the crude liquid refining system is the highest at 1.18-1.20. Because, at present, the main equipment of the crude liquid refining system is the leaf filter, when the crude liqu...

AI Technical Summary

Problems solved by technology

[0003] The purpose of the present invention is to address the shortcomings of the above-mentioned prior art, and to provide a Bayer method for producing alumina that can effectively solve the problem of leaf filter cake hardness, difficulty in unloading, short filter cloth cycle, and frequent brushing, which limits system capacity. Methods