Growth rate dispersion in batch and continuous crystallizers
The photomicrographic technique was used to study the secondary nucleation and growth characteristics of ammonium dihydrogen phosphate-water system. The contact nuclei were produced by contacting the growing 100 face of an ADP crystal. Experiments were conducted at different levels of undercooling and the macroscopic mechanism of growth was determined to be size-independent with the contact nuclei exhibiting growth rate dispersion;Based on the current investigation and the previous ones on potassium nitrate and citric acid monohydrate, a macroscopic "Constant Crystal Growth" model is proposed;The Constant Growth Model was also used to develop mathematical models for both continuous and batch crystallizers. The technique of Laplace transformation was used to relate the birth distribution, the growth rate distribution and the product crystal size distribution for both continuous and batch systems. A number of anomalies reported in the literature have been explained using this mathematical development. A procedure to determine growth rate kinetics in the presence of growth rate dispersion is also presented for the batch citric acid monohydrate-water system.