Use of Chlorine to Remove Magnesium from Molten Aluminum

Abstract

Removal of Mg from aluminum scraps, known as demagging, has been widely applied in the aluminum industry. This work discusses bubble-formation theories and magnesium kinetic removal from aluminum scraps using chlorine and inert gas fluxing. The interfacial area of the bubbles and residence time were estimated using a mathematical model. To inject gaseous chlorine, three types of nozzles were used with varying internal diameter. In addition, a porous plug, as well as varying input chlorine flow and concentration were used. The use of lower chlorine concentration improves efficiency because the interfacial tension is reduced therefore, more and smaller bubbles are formed. The model proposed herein is consistent with the experimental data.

Review on Application of Gases for Aluminium Refining

“…Fig.6a is an experimental result obtained by Vieira et al [17]. Argon gas was purged into the aluminium melt at various velocities and it was found that the oxide layer on the surface prevents the melt from further oxidation.…”

“…Application of chlorine not only reduces the magnesium content in the melt but also assists the removal of alkali metals, alkali earth metals, hydrogen. In addition to that, phase separation between the liquid metal and solid inclusions is also achieved [13], [17].…”

“…Figure1: Mg concentration with: a) Velocity of purging gas [17], b) Temperature of degassing [18], c) Gas flow rate [15], d)…”

Magnesium Removal from an Aluminum A-332 Molten Alloy Using Enriched Zeolite with Nanoparticles of SiO2

“…However, when the alloy is produced from scrap, the resultant Mg content of the alloy is higher than 0.1 wt-% and the excess of Mg needs to be removed. Vieira et al [5] used the chlorine method and discuss bubble-formation theories and magnesium kinetic removal from aluminum scraps using chlorine and inert gas fluxing. In spite of that Neff and Cochran [6] showed that the kinetics of the magnesium removal as MgCl 2 is rapid, but the unreacted chlorine and the gaseous coproduct AlCl 3 can limit the environmental acceptability of the process.…”