A Contribution to Design Gassing Crystallization Processes

Batch cooling crystallization is often used in chemical, biochemical, and pharmaceutical processes to design the properties of the solid product. The product properties and consequently the efficiency of the whole solid production process depend majorly on the nucleation event and the following crystal growth. In order to control the nucleation step, there exist several established technologies such as seeding and sonocrystallization. Gassing crystallization is an innovative induced nucleation technology and means the temporary introduction of gas bubbles within the metastable zone into a batch crystallizer to control the nucleation step. Motivation of this work is to contribute to the development of gassing crystallization processes and to establish it as alternative to seeding and sonocrystallization. Therefore, this work was divided into two parts with different focus: At first the potential of gassing crystallization to design product properties was investigated, the effect of gassing crystallization was quantified with respect to nucleation kinetic data, and gassing crystallization was compared to seeding and normal cooling crystallization. The second part focused on the transfer of gassing crystallization from lab to pilot scale and on the development of a transfer strategy, which was validated with a second substance system. This thesis showed that gassing crystallization is not only a promising alternative nucleation affecting technology at lab scale, but is also applicable to bigger scales. The potential of gassing crystallization was investigated extensively, quantified and shown to be competitive to established technologies. Especially the observation that gassing strongly affects the MZW and the nucleation mechanism is an important starting point for the application of gassing crystallization to various nucleation related crystallization phenomena. Gassing crystallization can be easily integrated into many batch crystallization setups and with the big potential shown and confirmed in this thesis it is recommended to be considered in future crystallization setups as nucleation affecting technology.