EFFECTS OF IMPURITY ON CRYSTAL-GROWTH AND NUCLEATION KINETICS IN AN MSMPR CRYSTALLIZER

An MSMPR crystallizer was used to study the crystallization kinetics o f potassium alum in the presence of impurities. Three different types of impurity, including an ionic species (Cr3+), a dispersing agent ((N aPO3)(6)), and an organic dye (Bismarck Brown), were tested. Although various effects of impurities on the crystal growth and nucleation rat es were observed, the responses to the addition of impurity for crysta l growth and nucleation rates were in the same direction; no matter th ey were increasing, decreasing, or remaining unchanged. However, under the constraint of constant magma density and retention time, differen t kinetic behavior, that is, the addition of impurity causes the cryst al growth and nucleation rates to respond in an opposite direction, fo r the same system was concluded.