Nucleation and crystallization behaviors of dipyrone in the pilot-scale stirred tank with different impeller types: Experiments and simulations

Abstract

Nucleation processes in solution crystallization are significantly affected by scaling up. This study focuses on the crystallization behavior of dipyrone in a 37 L stirred tank with 95 % ethanol, while the effects of three impeller types (SH-PI, DH, and A320-DW) on nucleation are examined. The nucleation parameters including nucleation rate J, critical Gibbs free energy, critical nucleation size, and chemical potential difference ∆μ, were calculated using the modified Sangwal's model and classical nucleation theory. The ∆μ was influenced by both impeller type and cooling rate R, with the latter exerting a more significant influence. J was most significantly affected by T₀. As T₀ increased from 328.15 K to 338.15 K and then to 348.15 K, the average J value increased by 7.99-fold and 4.99-fold, respectively. Particle size distribution (PSD) analysis revealed that particle size increased as T₀ decreased and R increased. Based on the J value and PSD, A320-DW impeller is recommended for the nucleation process at higher T₀. The electron structure of the dipyrone molecule was calculated by density functional theory (DFT), suggesting that the monoclinic crystal habit of dipyrone arises from stronger interactions at one end of the long chain of the molecules. This study provides valuable insights into the nucleation and characteristics of crystals from the perspective of industrial crystallization.