A method for removing gallium from primary aluminum by vacuum distillation

Abstract

A method for removing gallium from primary aluminum by vacuum distillation, which is carried out according to the following steps: (1) put the primary aluminum in a vacuum smelting furnace, and evacuate until the air pressure is 0.1-20Pa; (2) raise the temperature and keep the pressure at 0.1-20Pa 20Pa; smelting with heat preservation at 900-1100°C, the gallium in the primary aluminum is evaporated into the condenser; (3) cooling with the furnace. The invention uses primary aluminum containing gallium as a raw material, can realize the smelting and purification of aluminum simply and effectively, and obtains purified aluminum containing less than 50 ppm gallium; no waste gas is generated during the production process, and there is no pollution to the environment.

Description

technical field [0001] The invention relates to the technical field of metallurgical materials, in particular to a method for removing gallium from primary aluminum by vacuum distillation. Background technique [0002] In the modern aluminum smelting industry, the primary aluminum produced by the cryolite-alumina molten salt electrolysis method is cast into aluminum ingots after purification, clarification and slag removal; the purity of primary aluminum is generally between 99.5 and 99.8%. Impurities include iron, silicon, copper, vanadium, gallium, calcium and a small amount of non-metallic impurities, etc. Among them, the impurity gallium is brought in by the raw material alumina. [0003] Gallium and aluminum have many similarities in chemical parameters, and they often enter aluminium-containing minerals in the form of isomorphic substitution, and they are closely symbiotic in bauxite; in the process of alumina production, gallium is mainly produced from bauxite belts ...

AI Technical Summary

Problems solved by technology

[0003] Gallium and aluminum have many similarities in chemical parameters, and they often enter aluminium-containing minerals in the form of isomorphic substitution, and they are closely symbiotic in bauxite; in the process of alumina production, gallium is mainly produced from bauxite belts In the Bayer process of bauxite processing, gallium is mainly enriched in the form of sodium gallate and evaporated mother liquor, and a small part enters alumina; when sintering bauxite is processed, gallium is enriched in the carbonation decomposition and returned In the mother liquor, a small part enters aluminum hydroxide; during the process of bringing gallium from alumina to electrolytic aluminum, ionic gallium is preferentially precipitated at the cathode than aluminum, and gallium has a high solid solubility in aluminum, up to 20%. , so the precipitated gallium will be solid-dissolved into aluminum; the presence of impurity gallium reduces the current efficiency of the electrolysis process on the one hand, and on the other hand reduces the purity of primary aluminum, which will adversely affect the subsequent aluminum processing and use quality; trace amounts of gallium Will reduce the corrosion resistance of aluminum, increase the sensitivity of aluminum to chloride ions, and reduce the conductivity of aluminum

[0004] In the existing production process, gallium is mainly enriched and separated in the mother liquor of alumina production to prevent gallium from entering alumina products; in the actual production process, if the content of gallium in bauxite is very small, many enterprises The removal process of gallium is often omitted, or the removal of gallium is not complete, which will cause the primary aluminum produced by electrolysis in the downstream process to contain gallium as an impurity; because gallium and aluminum have similar chemical properties, general aluminum purification methods such as chlorination, oxidation, It is difficult to remove impurity gallium in aluminum by precipitation method and flux purification method; and the cost of electrolytic refining, segregation smelting and other methods is relatively high, and it is difficult to realize large-scale industrial application; currently there is no impurity removal method for gallium in primary aluminum literature report