ISBN 9783843907163

978-3-8439-0716-3, Reihe Technische Chemie

Kerstin Wohlgemuth
Induced Nucleation Processes during Batch Cooling Crystallization

175 Seiten, Dissertation Technische Universität Dortmund (2012), Softcover, A5

Zusammenfassung / Abstract

Crystallization is often used to separate or purify chemical products. The product quality is determined by the crystal size distribution (CSD), the mean crystal size, and the purity. Controlling nucleation is a crucial step guaranteeing constant product quality. Two methods of nucleation control exist: seeding and sonocrystallization. Seed crystals are sometimes difficult to produce and their use leads to the risk of cross-contamination. Sonocrystallization means the application of ultrasound within the metastable zone to induce nucleation. Despite years of investigation, it is not yet understood how nucleation can be induced by ultrasound.

The objectives of this work are the decryption of the induced nucleation mechanism and the identification of key process parameters for product design. To prove the possibility of a heterogeneous nucleation mechanism, where the cavitation bubbles act as nucleation sites, the idea of gassing crystallization comes up. Three different model systems were investigated concerning cooling, gassing, and sonocrystallization.

An existing model to simulate CSDs was extended based on experimental investigations. Cooling, gassing, and sonocrystallizations can be simulated. All important phenomena such as nucleation, growth, agglomeration, and breakage were taken into account. A sequential parameter determination procedure is developed and successfully applied.