Crystallization kinetics of ammonium carnallite (NH4MgCl3 center dot 6H(2)O), a double salt formed in NH4Cl-MgCl2 solution, and ammonium chloride in the NH4Cl-MgCl2-H2O system were experimentally investigated with the mixed-suspension mixed-product removal (MSMPR) crystallizer. The metastable zone widths of ammonium carnallite and ammonium chloride were explored. The effects of temperature and MgCl2 concentration on the nucleation and growth behaviors of ammonium carnallite and ammonium chloride crystals were investigated in both batch and continuous mode. Results showed that the crystal growth rates of the two salts are size-independent. The higher temperature enhances their nucleation and growth rates. The higher MgCl2 concentration results in a greater nucleation rate and lower growth rate of NH4Cl. The nucleation and growth kinetic parameters were determined with the experimental values at various temperatures and MgCl2 concentrations. A kinetic operation equation which agreed well with experimental data was then proposed for design purposes. The operation model capable of analyzing the effect of suspension density and residence time on the crystal size of ammonium chloride, and ammonium carnallite was finally employed to the preliminary design of crystallizers in the ammonium chloride recovery process.