(84b) Operating parameters of a continuous sono-chemical precipitation reactor

The wet chemical synthesis allows the concurrent production and stabilisation of nanoparticle dispersions. The state of the art process equipment used for precipitation reactions are stirred tank reactors in batch or continuous operation. The quality of mixing in these reactors is limited by the over all energy dissipation of the stirring energy. Therefore the scale up of nanoparticle precipitaion in tank reactors is limited. The alternative concept is the application of flow through reactors, which allow short mixing times due to a high local energy input. Flow through reactors can be designed as static mixers, impinging jets or sono-chemical reactors. The latter will be discussed with the focus on the apparatus design concept and possible ability for different particle synthesises. Both, the constructive design of the reaction chamber and the operation parameters affect the efficiency of the particle synthesis. The main aim of the process scale up is to maintain the same high particle quality compared to lab scale batch precipitation. The particle quality is evaluated using PCS- and XRD-measurements, and TEM images as well. The effect of the operation parameters ultrasonic power consumption, residence time, particle and reactant concentration on the particle size is shown. Further experimental and numerical results focussing on the geometric design of the reaction chamber are discussed. Here the main question is the position of the ultrasonic horn, of the feed pipes and the strategy to supply the stabilizing agent.

Keywords: magnetic fluids, stabilized suspension, ultrasound, crystallization, process equipment, nanoparticle, specific energy input.