Metastable Zone Width and Primary Nucleation Kinetics for Crystallization of KCl from a KCl-MgCl₂‑H₂O System

Effects of MgCl₂ and NaCl mass fraction, stirring rate, cooling rate, and flotation reagent on metastable zone width of KCl in the aqueous system K⁺, Mg²⁺//Cl^–-H₂O were investigated by a laser method. Metastable zone width increases with a decrease in stirring rate and saturation temperature and an increase in cooling rate. Moreover, metastable zone width increases significantly with the presence of dodecyl morpholine (DMP). The effect mechanism was revealed by molecular dynamics simulation. It demonstrated that diffusion inhibition in K⁺ of DMP contributes to the increase in metastable zone width. Furthermore, the self-consistent Nývlt-like equation and classical 3D nucleation theory were employed to study primary nucleation kinetics of KCl with acceptable accuracy. The activation energies E_sat of the KCl nucleation process calculated by the self-consistent Nývlt-like equation and classical 3D nucleation theory are 14.88 and 11.91 kJ/mol, respectively. Research on metastable zone width provides a thermodynamic basis for KCl production process optimization from cold decomposition of carnallite.