CRYSTAL DISSOLUTION AND GROWTH IN A LEAN FLUIDIZED-BED CRYSTALLIZER

Abstract

Dissolution and growth rates of potassium alum crystal were measured in a lean fluidized-bed crystallizer in which the flow rate of solution was set near the settling velocity of seed crystals. The dissolution rates were shown to be linear with respect to undersaturation. The mass transfer coefficient of crystal growth and the surface integration coefficient were determined using the two-step model with a surface integration kinetics of second-order. Mass transfer coefficients for dissolution and growth were found to be independent of the crystal size and the solution velocity, and were jointly correlated in a form derived from the Froessling equation. The surface integration rate turned out to be a function of crystal size, which was responsible for the size-dependent growth of potassium alum crystal.