Abstract
We performed a continuous industrial MSMPR crystallization of sodium chloride (NaCl) by means of evaporation at different impurity concentrations in a liquor solution such as seawater. We sieved the suspended crystals in the crystallizer, and determined the growth and nucleation rates using the population balance of the crystal size distribution (CSD). We observed the crystals at each stage in the sieves with a microscope, and measured the degrees of roundness and agglomeration. We also measured the impurity concentration represented by potassium ions in the crystals. The suspension density was useful for correlating the growth and nucleation rates. The impurity concentration in the crystals increased as that in the solution increased. We described the impurity concentration as a function of the crystal size, and it was larger at a size range of less than 300μm and had minimum values and increased slightly by again increasing crystal size. The degrees of roundness and the aggregation of the crystals were significant factors for correlating the impurity concentration in the crystals. We propose modeling by operative variables for the growth rate, nucleation rate, suspension density, degrees of roundness, and aggregation, and the distribution coefficient of impurity as a function of crystal size for NaCl industrial crystallization.
