The Production Of White Alumina Oxide
There are many varieties of alumina oxide abrasives. In addition to brown alumina oxide, white alumina oxide is also extremely important. White alumina oxide is also widely used. Let”s summarize the production process of white alumina oxide.with brown alumina For example, if it continues to develop, it will definitely become the benchmark of the industry and play an important role in leading the market. https://www.becens.com
The main raw material for the production of white alumina oxide abrasives is alumina powder, which is an industrial product made of bauxite through chemical purification. Alumina powder is white powder, with an alumina content of over 98% and a melting point of over 2000≧. It is also the main raw material for making pink alumina oxide.
Raw material requirements
High-quality white alumina oxide depends on the quality of alumina powder, and the quality of alumina powder depends on the content of alumina and sodium chloride in it. When making white alumina oxide abrasives, the alumina content must be controlled above 98.4%. The content of sodium oxide is not higher than 0.6%, otherwise many substandard products will be produced, so the content of sodium oxide should be strictly controlled. High sodium oxide content will generate a lot of β-alumina, which will affect the properties of white alumina oxide, such as the decrease of crystal hardness of white alumina oxide, the decrease of cutting ability, easy pulverization and broken, low thermal stability and so on.
Smelting principle
White alumina oxide is made of aluminum oxide powder which is melted in an electric arc furnace and then cooled and crystallized. Like brown alumina oxide, the smelting time determines whether the charge is fully melted and the carbon is fully volatilized. There is no reduction process in the smelting of white alumina oxide, so the impurities may remain in the crystal structure, which will affect the chemical composition and color of white alumina oxide and reduce the quality of white alumina oxide.
Among them, the most harmful impurity is sodium oxide. In order to eliminate or reduce the harm of sodium oxide, three methods have been adopted in smelting:
1. Adding quartz sand method: the purpose is to form nepheline and limit the formation of sodium aluminate. Nepheline is less harmful than impurity sodium aluminate, but adding sodium oxide will introduce silica impurities at the same time, and the remaining in alumina oxide Nepheline and silica are still difficult to remove, and still affect white alumina oxide.
2. Adding aluminum fluoride method: aluminum fluoride is relatively stable, and it is not easy to react with carbon at high temperature. When aluminum fluoride is added in excess, cryolite will form. It is possible to fully volatilize under the high temperature reaction, and if not volatilized, it will be segregated when the white alumina oxide is cooled, and the residue can also be removed in the water washing process. But this method is harmful to workers and equipment.
3. Cooling segregation method: The melting point of sodium aluminate is 1900≧, which is lower than that of alumina, so it is the first to crystallize from alumina oxide. The appearance and structure of sodium aluminate crystals and white alumina oxide crystals are different, and they are easy to identify and can be removed after released from the furnace. This method is mostly used at domestic and abroad. This industry requires that the sodium oxide content be as low as possible, preferably within 0.3%.
The content of low-sodium white alumina oxide and sodium oxide can be ＋0.2, or even ＋0.1. Because of the reduction of sodium content, the performance of white alumina oxide can be improved in various aspects, such as melting point, particle density, bulk density, flexural strength, compressive strength, true density, hardness and so on. At present, it is mainly used in special ceramics, high-quality refractory materials and other fields.
