Minimizing Salt and Metal Losses in Mg-Recycling through Salt Optimization and Black Dross Distillation

Magnesium recycling processes typically are based on the use of fluxes, mostly containing MgCl2, KCl, NaCl and CaF2. It is state of the art that application of salt flux in contact with magnesium scrap leads inevitably to the formation of a sludge so called "black dross" containing the both metallic and oxidic magnesium as well as salt components. Up to now it has not been yet possible to recycle this sludge economically. Such the investigation to recover metallic magnesium as well as part of the salt flux from this sludge is the task of this work. The main targets are to decrease the metal/salt loss and to enhance the metallic coagulation with the aim of increasing the recycling efficiency of the entire magnesium recycling cycle with the scope of the environmental requirements for a sustainable process. The results of using lab- as well as pilot-scale experiments lead to an almost zero-waste-process, which closes the existing gap in the magnesium recycling loop.