Method for improving seed decomposition rate in aluminum oxide production

Abstract

The invention discloses a method for improving the seed decomposition rate in aluminum oxide production. The method is characterized in that in a seed crystal decomposition process, an electrodialysis technology is adopted to cooperate with seed crystals to decompose a sodium aluminate solution. The synergistic effect of electrodialysis and seed crystal decomposition decomposes the sodium aluminate solution into a high-causticity-ratio solution and aluminum hydroxide crystals and separates the undecomposed sodium aluminate solution, and the undecomposed sodium aluminate solution can be maintained at a low causticity-ratio level, so that rapid seed crystal decomposition is ensured, the decomposition efficiency is improved, the decomposition rate is also improved, and meanwhile, the cycle efficiency of producing the aluminum oxide by the Bayer method is also improved.

Description

technical field [0001] The invention relates to the technical field of alumina production, in particular to a method for improving the decomposition rate of seeds in alumina production. Background technique [0002] The Bayer process is the mainstream process for producing alumina in the world. Decomposition is a key step, which is to add aluminum hydroxide seeds to the sodium aluminate solution obtained by dissolving bauxite, so that the sodium aluminate solution can be decomposed to obtain more hydrogen. alumina crystals. As the decomposition continues, the caustic ratio of the solution system continues to increase, making the decomposition rate slower and slower, and it is difficult to increase the decomposition rate. At present, there are many ways to improve the decomposition rate of seed fractions. Some adopt the form of additives but the cost is too high or the operation is difficult; some adopt the form of adjusting the original process parameters but the effect is ...

AI Technical Summary

Problems solved by technology

As the decomposition continues, the caustic ratio of the solution system continues to increase, making the decomposition speed slower and slower, and it is difficult to increase the decomposition rate.

At present, there are many ways to improve the decomposition rate of seed fractions. Some adopt the form of additives but the cost is too high or the operation is difficult; some adopt the form of adjusting the original process parameters but the effect is limited; In the form of mother liquor, but the seed crystal decomposition rate is still not high, the highest is not more than 70%, and the process is cumbersome

In patents that use electrodialysis technology to strengthen decomposition, the electrodialysis operation is often carried out step by step after the decomposition of the seed crystal. The Chinese patent No. CN101070171A discloses a method for strengthening the Bayer method of seed separation. This patent adopts the decomposed mother liquor after the conventional Bayer method of seed separation, and adopts ionic membrane electrolysis. Under the joint action of electricity and ionic membrane, the solution The stability of the aluminum hydroxide is reduced, so that the aluminum hydroxide in it continues to be decomposed and separated, thereby increasing the decomposition rate of the Bayer process system alumina and improving the cycle efficiency of the Bayer process alumina production. The patent uses electrodialysis to improve the decomposition rate. Technology, electrodialysis operation and seed crystal decomposition are carried out step by step. The object of electrodialysis treatment is mainly the mother liquor after seed separation, which can improve the seed crystal decomposition rate to a certain extent. However, due to the relatively high causticity of the seed separation mother liquor, the decomposition rate The improvement is limited, there is no report of more than 70%, and the process is more cumbersome

For example, the Chinese patent with the publication number CN105836771A discloses a method for improving the decomposition rate and cycle efficiency of alumina production. In order to evaporate the mother liquor and process the mother liquor, the evaporated mother liquor enters the evaporation process for evaporation and concentration, and the treated mother liquor is subjected to static treatment. After the static treatment is completed, the solid-liquid separation is obtained to obtain the supernatant and aluminum hydroxide; At the same time, the water is sent to the cationic membrane diffusion dialyzer for countercurrent exchange to obtain the raffinate and recovered lye; (3) The raffinate is sent back to the crystal seed decomposition process for further decomposition; the recovered lye is sent to the evaporation process for evaporation and concentration, After concentration, it is sent to the wet grinding process to mix with ore. The patent processes the mother liquor, which is cumbersome to operate, and the decomposition rate of the seed crystal is still not high, the highest is not more than 70%, and the process is cumbersome

Images