Simulation of induction time for nucleation was performed under isothermal conditions for unseeded aqueous solutions of different concentrations. The effects of stirrer speed and growth rate on induction time were both explained with the proposed secondary nucleation-mediated mechanism. The effect of stirrer speed N r was incorporated into the simulation with an empirical relation of k b2 ∝ N r j, where k b2 is the coefficient in the secondary nucleation rate equation B 2 = k b2 (ΔT) b2μ 3, ΔT is supercooling, j and b2 are empirical constants and μ 3 is the third moment of crystal size distribution. The simulated induction time decreased with an increase in stirrer speed at lower supercoolings, while it remained unchanged at higher supercoolings. Such action of stirrer speed was similar to that observed in the literature data. The growth rate effect was considered to be caused by a faster increase in the secondary nucleation rate via a faster increase in μ 3. The simulated induction time decreased with an increase in crystal growth rate. This type of growth rate effect is completely different from the existing mechanism considering the time needed for invisible nuclei to grow to a detectable size.
ASJC Scopus subject areas
- 化学 (全般)