Crystal growth kinetics of two-step growth process in liquid fluidized-bedcrystallizers

The fluidized-bed crystallizers have long been used in the chemical industr y and recently for water treatment as the so-called pellet reactors. This r eport summarizes the experimental results regarding hydrodynamics and cryst al growth rates in laboratory-scale fluidized-bed crystallizers. The two-st ep crystal growth model rather than the over-all model is adopted to explai n the observed kinetic behaviors. In using the two-step growth model, the d isadvantage is the uncertainty of the surface-reaction order. A reliable me thod is suggested to explore the surface-reaction order using a lean fluidi zed-bed crystallizer The crystal growth process of sparingly soluble salts, which have been studied recently for a few systems, seems more complex tha n that of soluble salts. Then, a comparison of crystal growth kinetics of s oluble salts is made between the dense and lean fluidized-bed crystallizers . As a conclusion, the two-step growth model is suitable for the estimation of crystal growth rates in the design of a liquid fluidized-bed crystalliz er. (C) 1999 Elsevier Science B.V. All rights reserved.