Project Details
Projekt
Process-technological fractionation of finest particles based on geometrical and material separation characteristics in a strong centrifugal field
Applicant
Professor Dr.-Ing. Hermann Nirschl
Subject Area
Mechanical Process Engineering
Term
since 2017
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 380484211
As part of the priority program "Highly specific multidimensional fractionation of technical ultrafine particle systems", the subproject investigates the separation of nanoscale particle collectives using geometric and material separation characteristics in the strong centrifugal field of a semi-continuous tubular centrifuge. In the first funding period, a method was developed which enables the analysis of a separation experiment by means of analytical centrifugation and the calculation of multi-dimensional grade efficiency curves. The sedimentation coefficient of a particle depends on geometrical as well as material factors, which includes several dimensions in contrast to the consideration of a hydrodynamic diameter. The application of the method was demonstrated in the case of superimposed size and density fractionation of a particle mixture of heavy and light nanoparticles. The difficulty in the practical determination of a grade efficiency curve lies in assigning a relative number or mass of particles to each measured separation criteria within the distribution. With the aim of using fast and non-invasive measuring methods, this aspect was implemented with the aid of UV-VIS spectroscopy. The methodology enabled the quantitative determination of the composition of a fractionated particle mixture. In order to generate a valuable process monitoring, a UV-VIS flow sensor was incorporated. It was shown that in case of classification, a prediction of the particle concentration in the overflow can be made over a longer process time with low error.In the second funding period, the focus will lie on the experimental assessment of the process fractionation via grade efficiency curves of the centrifuge. Here, parameters such as the suspension properties and the operating conditions of the apparatus are decisive for the separation result. A further goal it to carrying out model-based evaluations and making predictions about the separation result, depending on the multidimensional separation characteristics, with as little error as possible. Simultaneously, the optimal choice of operating parameters for a desired separation result can be derived. Since the process time also influences the semi-continuous fractionation of the suspensions in a tubular centrifuge, real-time monitoring of the separation kinetics with the UV-VIS flow sensor is planned. The objective hereby is the recording of a stable measuring signal from which information about the relative particle concentration of the fine fraction can be extracted. Potentially, negative changes in product quality can be reacted to by adjusting the operating conditions. Ultimately, the subproject is working on the experimental and model-based investigation of multidimensional separation processes in high-performance centrifuges, on the development of solution strategies and on gaining a better understanding of the occurring physical processes.
DFG Programme
Priority Programmes
