Modelling supersonic quenching of magnesium vapour in a Laval nozzle

Supersonic quenching of magnesium vapour plays a pivotal role in the carbothermal reduction process for magnesium and the production of fine magnesium powders. Modelling of this process has previously been based on Classical Nucleation Theory in a one-dimensional flow expansion without considerations of background gas turbulence and the associated heat and mass transfers. This paper presents a single-velocity field, multi-component fluid model that overcomes the above shortcomings. The model has been validated using steam condensation data and applied to study supersonic quenching of magnesium vapour in a laboratory-scale Laval nozzle. Modelling results indicate a strong dependence of the vapour condensation characteristics on parameters such as vapour concentration and choice of carrier gas. The model is potentially a useful tool for designing and up-scaling processes that utilise supersonic quenching of metallic vapours.

► We modelled supersonic quenching of magnesium vapour in a Laval nozzle. ► The model considered condensation and solidification of Mg in a carrier gas mixture. ► Choice of carrier gas critically affects supersonic cooling inside the nozzle. ► Increasing Mg vapour concentration reduces the production of Mg solids in the nozzle.