Analysis of the Size Distribution of Product Crystals from a Continuous Crystallizer

Maltitol is crystallized with seeds by cooling mode in industry, often with large amount of fine crystals and wide crystal size distribution. To eliminate the fine nucleation, it's necessary to understand the nucleation kinetics. In this work, the solubility of maltitol in water was measured by the gravimetric method, the nucleation kinetics of maltitol in batch cooling crystallization was investigated using focus beam reflectance measurement (FBRM), and a novel method was proposed to determine the induction time from the trend of the crystal median chord given by FBRM. Based on the relationship between the induction time and the supersaturation, the nucleation mechanism was obtained, including homogenous nucleation at high supersaturation and heterogenous nucleation at low supersaturation. Additionally, combining the classical nucleation theory (CNT) and Arrhenius’ principle, the crystal‐solution interfacial energy and the energy barrier of homogenous nucleation were calculated. From the scanning electron microscope (SEM) images, the growth mechanism of maltitol was identified as surface nucleation growth and the surface entropy factor calculated from the kinetic analyses of tind data corroborated this growth mechanism.

The induction time, interfacial energy and growth mechanism of maltitol in batch cooling crystallization

Hou

et al. 2012

Crystallization of copper sulphate

Giulietti

Derenzo

Nývlt

et al. 1995

Results of the studies of copper sulphate pentahydrate batch crystallization in the temperature range from 70 down to 30 "C are presented. In some of the experiments, free sulphuric acid has been added. The metastable zone width, nucleation and growth kinetic parameters, as well as the system kinetic constant were determined and compared with the data published in the literature.Ergebnisse einer Studie der diskontinuierlichen Kristallisation von CuSO, . 5 H,O im Temperaturbereich zwischen 70 und 30 "C sind prasentiert. Freie Schwefelsaure wurde in einigen Versuchen zugegeben.Die Breite des metastabilen Gebietes, kinetische Keimbildungs-und Kristallwachstumsparameter sowie die kinetische Systemkonstante B, wurden aus den Versuchen ermittelt.

Effect of Ultrasonics on Agglomeration

Nývlt

Žáček

1995

Crystal size distribution of potassium aluminium sulphate dodekahydrate prepared under various conditions has been used for characterization of the degree of agglomeration of crystals. Six series of batch precipitation experiments with batch times from 2 to 80 minutes have been represented by a) dried crystals, b) the same crystals partially de-agglomerated before the measurement, c) wet crystals taken directly from the batch, d) the same crystals partially de-agglomerated before the measurement, e) wet crystals taken directly from the batch occurring under ultrasonic action, and f ) these crystals partially de-agglomerated just before the measurement. Degree of agglomeration decreases in this sequence. Der Aggiomerationsgrad von Kalium Aluminium Sulfat