Deutsch
English
Nanoparticles can be defined as a disperse system in which at least one length expansion is below 100 nm. Compared to a chemically equivalent, continuous material, these have significantly more favorable optical, electrical, magnetic, mechanical, diffusion and material properties. Nanoparticles are widely used in various industrial and scientific fields, e.g. biotechnology, as catalyst carriers, for data or energy storage and microelectronics. For mass application, e.g. for new so-called "advanced materials", it is necessary to make sufficient quantities of nanoparticles available. The low production quantities are currently the reason for the high costs of nanoparticles. One possible solution is the wet-chemical production of nanoparticles, which poses considerable technical problems for stirred tanks. Flow reactors can be seen as an alternative for mixing and precipitation reactions. However, these have been little investigated to date, particularly for precipitation reactions, and are therefore not available on the market in an optimized form. The use of ultrasound enables a defined, externally controllable, intensive, locally limited energy input into the process chamber. The mixing times achieved by ultrasound with the active mechanisms of cavitation and vibration are in the range required for precipitation (<1ms). With regard to sonochemistry, it must be noted that the decisive problem is the scale-up of the research results obtained in the laboratory reactor to large-scale dimensions or throughputs. Due to the complex processes in ultrasound and the resulting cavitation, undesirable effects occur when scaling up from laboratory to technical scale. The reaction yields on a technical scale are less productive than expected. This is the background and motivation for the present project, in which the following objectives are pursued:
- Creating a design strategy using modern methodological approaches for a specific class of ultrasonic reactors and thus the
- Evaluate and improve the operating behavior of ultrasonic precipitation reactors for the production of nanoparticles.
- Demonstration of the implementation of a continuous ultrasonic precipitation reactor.
The aim of nanoparticle synthesis must be to produce the particles as a stable colloid in order to prevent agglomeration of the particles. In the production of nanoparticles by precipitation, the aim is to promote homogeneous nucleation and avoid agglomeration. This can be achieved by the highest possible supersaturation, i.e. a late but intensive mixing of the reactant streams. In order to avoid unbalanced flow conditions and broad particle size distributions, targeted flow control in precipitation reactors is necessary.
The overarching and technological goal of this project is the development of reactors for the efficient and controlled production of nanoparticles. The concept is based on the wet-chemical production of nanoparticles in continuously operated ultrasonic precipitation reactors. The design strategies developed here increase design reliability. This means that equipment manufacturers or ultrasonic specialists can design and offer equipment and systems for precipitation processes using ultrasound with significantly reduced risk.
A central issue in the optimization of precipitation reactors is the assessment of micromixing. The characteristic times of the micromixing are determined using the Villermaux method. The sound field is measured using a hydrophone. The Weissler reaction is used to characterize the sonochemical reactivity in the homogeneous liquid phase. <pstyle="text-align:justify">This AIF project is a joint project with the Institute of Mechanical Process Engineering and Mineral Processing at TU Bergakademie Freiberg. At the TU Bergakademie Freiberg, the experimental part of the work is carried out with the characterization of the hydrodynamic mixture in the process chamber of an ultrasonic reactor by means of Villermaux reaction, the characterization of the mixture by the ultrasonic field and its geometric propagation in the process chamber, as well as the optimization of the geometry and the operation of the optimized precipitation reactors. At TU Clausthal, the simulation of the flow control in the reactor is carried out for its optimization and for the analysis of the micromixing. <pstyle="text-align:justify">The project is funded by the German Federation of Industrial Research Associations "Otto von Guericke" e.V. - AiF 15347.
Publications and conferences (*speaker)
- Ö. Ertunc, N. Özyilmaz, H. Lienhart, K. Beronov, F. Durst: Inhomogeneity of turbulence generated by passive grids, Journal of Fluid Mechanics, in review
- N. Özyilmaz, K. Beronov, A. Delgado: Characterization of the dissipation tensor from DNS of grid-generated turbulence, High Performance Computing in Science and Engineering, Garching/Munich 2007, Springer Verlag, 2008.
- K. Beronov, F. Durst, N. Özyilmaz, P. Lammers: Statistics and intermittency of developed channel flows: a grand challenge in turbulence modeling and simulation, High Performance Computing on Vector Systems, Springer Verlag, 2006.
- N. Özyilmaz*, G. Brenner: Effects of roughness elements on BaSO4 precipitation in T-shaped microchannels. To be presented in Conference on modeling fluid flow 2009, Budapest, Hungary.
- Ö. Ertunc*, N. Özyilmaz, H. Lienhart, F. Durst: Persistence of inhomogeneity of turbulence generated by static grid structures, to be presented in 12th EUROMECH European Turbulence Conferencet Marburg, Germany.
- N. Özyilmaz*, G. Brenner: Numerical Modeling of BaSO4 precipitation. to be presented in ProcessNet Annual Meeting in CFD, Extraction, Mixing, Fulda, Germany, 2009.
- N. Özyilmaz*, G. Brenner: Numerical Modeling of BaSO4 precipitation. to be presented in ProcessNet Annual Meeting in CFD, Extraction, Mixing, Fulda, Germany, 2009.
- N. Özyilmaz, K. Beronov*, A. Delgado: Characterization of the Reynolds stress and dissipation-rate decay and anisotropy from DNS of grid-generated turbulence, GAMM 2008, Bremen, Germany.
- N. Özyilmaz*, K. Beronov, F. Durst: Direct simulation of turbulence generation and transformation in flows obstructed by square grids, Fifth International Symposium on turbulence and shear flow phenomena, Munich, Germany, 2007.
- N. Özyilmaz*, G. Brenner: Ultrasonics Effects in BaSO4 precipitation, To be presented in ProcessNet Annual Meeting Reaction Engineering. Würzburg, 2009.
- K.Beronov*, N. Özyilmaz, F. Durst: Characterization and high-throughput microfluidic applications of an obstructed-channel flow class, Fifth International Symposium on turbulence and shear flow phenomena, Munich, Germany, 2007.