Features of Producing Aluminum From Wastes of Foundry

Processy litʹâ, 2020, Tom 140, №2, p.3-7

Abstract

Received 12.11.2019

UDC 669.715:621.74

The mechanism of production of metallic aluminum from casting slag is presented. It is based on the peculiarities of the temperature dependences of chemical reactions involving aluminum. The process scheme consists of two stages: pyrometallurgical and hydrometallurgical. The mechanism of the pyrometallurgical process is based on the change in the valence of aluminum from three to one, and vice versa, depending on the reaction temperature. The temperature is then lowered to 1000-1100 0С. As a result, the monoxide alumina decomposes into metallic aluminum and trivalent alumina. Then the aluminum is drained and processed sodium aluminate (gray loose powder) to obtain pure aluminum oxide. The hydrolysis is carried out in autoclaves. As a result, aluminum hydroxide is formed. To increase the rate of this reaction stirring with air is used. Due to hydrolysis, the precipitate of aluminum hydroxide is separated from the solution by filtration. It is then washed, dried and quenched at a temperature of 1200 0С at which Al (OH)3 is converted to α–Al2O3. Thus obtained pure alumina is fed to the electrolysis. A series of experiments was carried out regarding the determination of aluminum yield in the process of interaction of casting slag containing aluminum with caustic sodium (Na2CO3). Studies have shown that approximately 49% of aluminum can be extracted from the foundry slag in a metallurgical manner. The non-waste technological scheme is presented.