| dc.description.abstract | The seeding technique is an effective method to control the size and size uniformity of crystals in the batch cooling crystallization. Crystal size has a great influence on the downstream process such as filtration and drying. In many studies related to seeding, a simple empirical equation based on mass balance is used to understand the relationship between seed crystal size, seed loading, and crystal size. However, this relationship is too ideal and simplified, and many process control or operation parameters are ignored. The purpose of this study is to modify the seeding equation by designing experiments with different operating parameters. Temperature cooling range and supersaturation will be taken into consideration to derive an equation for seeding in the D-mannitol system in batch cooling crystallization, which is used to predict the crystal size for different experiments. To understand the crystallization mechanism of D-mannitol in water, the first part of the study was conducted through the nucleation induction period obtained with different initial degrees of supersaturation of: 1.45, 1.38, 1.32 and 1.25. The kinetics and thermodynamic parameters of the primary nucleation D-mannitol system such as interface energy, critical Gibbs energy barrier, nucleation rate, and critical size of nucleation can be obtained by Classical Nucleation Theory (CNT). In the second part of the experiment, we adjusted the three seeding parameters to conduct the batch cooling crystallization experiments with seed crystal sizes ranging from 88 to 125 μm: (1) cooling temperature range, (2) seed loading, and (3) supersaturation. The experimental results found that at the lower temperature cooling ranges of 30 to 15 °C and 25 to 5 °C with seed loading of 1, 3, and 5 wt% all obtained a uni-modal size distribution of D-mannitol crystal and the mean crystal size was about 200 μm. The modified seeding empirical equation was: Lp/Ls =((1+Cs)/Cs )^(1/n), where n=A′(C0-C* ) exp((-Ea)/kT). The values of n could be obtained from experiments with the same temperature cooling range with different seed loadings. The experimental results showed that n was 5.27, 7.81, and 11.98 with the temperature cooling ranges of 35 to 25 °C, 30 to 15 °C, and 25 to 5 °C, respectively. From the value of n, the activation energy of secondary nucleation in the D-mannitol system could be calculated as Ea = 172.55 × 10-22 J·nucleus-1 and the exponential pre-factor A′ = 1.41 × 10-3 mL of solution/mg. The empirical equation for D-mannitol seeding in water was successfully established and well-validated in subsequent experiments adjusting the seed sizes to 44 – 88 μm and 125 – 177 μm. | en_US |