(41r) 'Effect of Nucleation Agents on Spherical Agglomeration in the Cooling Crystallization of L-Methionine

L-methionine, the sulfur-containing essential amino acid, is generally achieved to thin and plate-like crystals with {001} planes by a batch cooling crystallization. This morphology of crystals has an adverse effect on powder flowability. However, when a small amount of nucleation agents was added, spherical agglomeration of L-methionine having better flow characteristics was produced in the cooling crystallization. To understand the effect of these additives, the measurement of induction times and statistical approach on the induction time distribution were implemented. It was confirmed that additives have roles as nucleation promoters and nucleation rate kinetics was evaluated in terms of supersaturation. Using the thermodynamic parameters of this model, the values of the effective interfacial energy for heterogeneous nucleation was estimated. Surface energy for the crystal-solution interface was changed according to the kinds of additives due to the hydrophobic-hydrophobic interactions on {001} planes between sulfur atoms of L-methionine and additive molecules. Also effects of process variables, cooling rates, kinds and concentrations of additives, on the size distribution of spherical agglomerates which achieve the increase on powder flowability were investigated