Continuous crystallization is increasingly used in the production of pharmaceutical ingredients, but for an appropriate application of such continuous process deposition of particles in tubular systems must be examined as well. In this work the influence of various parameters such as particle size, pipe diameter and volume fraction of solid phase on the critical deposition velocity was studied. The aim was to find the optimal process parameters for the use in a real continuous crystallizer.
Experimental work started with the crystallization performed in a batch reactor. Afterwards, the obtained suspension was pumped through a closed loop, where visual control (camera) was used for monitoring the deposition of particles in a horizontal pipe. For monitoring of particle size distributions FBRM technique was used, which was also validated using optical microscopy.
The dependency of critical deposition velocity on the particle size and pipe diameter was studied and a correlation was derived suiting the theoretical background information. On the other hand, the correlation between critical deposition velocity and volume fraction of solid-phase was not found in this work. Furthermore, various empirical correlations were examined and their ability to model deposition in this system was investigated. The correlations which best described our system were additionally optimized and also a new model was proposed correlating the critical deposition velocity and various process parameters examined. In conclusion some topic for further research were proposed.
|
