The salt flux for secondary aluminum melting can increase the direct recovery rate of aluminum during the remelting process. Aluminum and scrap aluminum, such as those used in beverage containers (UBCS), are processed in this way. The remelting of aluminum in the furnace is carried out under a layer of molten salt to prevent the oxidation of aluminum in the furnace atmosphere and promote the coalescence of molten aluminum, thereby maximizing the recovery of aluminum. During processing, droplets of oxide film are easily formed on the surface of molten aluminum. The oxide film inhibits the coalescence of molten aluminum, resulting in the loss of smaller particles in the process, thereby reducing the amount of aluminum recovered. Irrecoverable aluminum droplets with oxide films are sometimes called dross.
The flux for secondary aluminum smelting in the furnace helps to strip and suspend the oxide film, thereby increasing the coalescence of droplets and reducing the formation of slag. The salt stream wets the oxide film and initiates the decomposition of the film, peeling it from the surface of the molten aluminum droplets. The oxide film fragments peeled from the aluminum are still suspended in the flux. The aluminum droplets, which are denser than the flux, then form a continuous molten pad under the flux layer. The covering flux also prevents further oxide formation by protecting the metal from the furnace atmosphere.
The flux for secondary aluminum melting is mainly composed of a mixture of high-purity sodium chloride and potassium chloride. The high-purity salt used in these processes is extracted and purified from the solution through complex and highly developed methods.
A high-purity salt flux composition containing high-purity NaCl and KCl, alkaline reagents, and fluoride. The salt flux composition promotes the coalescence of molten aluminum droplets and prevents the oxidation of aluminum, thereby increasing the yield of aluminum recovered from the recycling process.