Modelling of agglomeration in industrial crystallization from solution

A phenomenological approach to evaluating the agglomeration rate of growing crystals is presented. Crystals larger than the Kolmogoroff microscale collide because of the fluctuating velocity field. Bridges between the crystals form as a result of competition between crystalline growth and the turbulent velocity fluctuations on the opposite sides of the agglomerate. Crystals smaller than the Kolmogoroff microscale collide because of viscous laminar microshear stresses within the same turbulent eddy, are kept close together by Van der Waals forces and are joined together by crystalline bridges that grow between them. The strength of these bridges depends on the supersaturation level during the moments following the collision. These two sets of phenomena lead to two different preferential generation mechanisms for agglomerates. One example involving important agglomeration effects is developed for each case: the crystallization of adipic acid belongs to the first group (large crystals), whereas the precipitation of calcium oxalate monohydrate is typical of the second case (small crystals).

[1]  René David,et al.  Crystallization and precipitation engineering—III. A discrete formulation of the agglomeration rate of crystals in a crystallization process , 1991 .

[2]  P. Saffman,et al.  On the collision of drops in turbulent clouds , 1956, Journal of Fluid Mechanics.

[3]  M. Cournil,et al.  Using a turbidimetric method to study the kinetics of agglomeration of potassium sulphate in a liquid medium , 1991 .

[4]  Michael J. Hounslow,et al.  Nucleation, growth, and aggregation rates from steady‐state experimental data , 1990 .

[5]  M. Hounslow.  A discretized population balance for continuous systems at steady state , 1990 .

[6]  M. Hounslow,et al.  A discretized population balance for nucleation, growth, and aggregation , 1988 .

[7]  S. Bhatia,et al.  Modified MWR approach: Application to agglomerative precipitation , 1992 .

[8]  S. Katz,et al.  Some problems in particle technology: A statistical mechanical formulation , 1964 .

[9]  K. Higashitani,et al.  Turbulent coagulation of particles dispersed in a viscous fluid. , 1983 .

[10]  J. Seinfeld,et al.  Numerical solution of the dynamic equation for particulate systems , 1978 .

[11]  J. Abrahamson.  Collision rates of small particles in a vigorously turbulent fluid , 1975 .

[12]  P. Ayazi Shamlou,et al.  Crystal break-up in dilute turbulently agitated suspensions , 1993 .

[13]  J. Klein,et al.  Crystallization and precipitation engineering—I. An efficient method for solving population balance in crystallization with agglomeration , 1988 .

[14]  René David,et al.  Crystallization and precipitation engineering—IV. Kinetic model of adipic acid crystallization , 1991 .