Fractionation of ultrafine particles by size and density: evaluation of separation efficiency by UV-VIS spectrometry

M. Winkler*, H. Nirschl, Karlsruhe Institute of Technology (KIT), Germany

Classification is an established process in solids processing technology to divide particulate products into defined fractions based on their size. However, complex particle systems with strict specifications for product-relevant properties often require a different approach. Thus, multidimensional fractionation is needed in which both geometric (particle size and shape) and material (density, interfacial properties) separation characteristics are taken into account.

Previous studies focused on the subordinate step of classification in semi-continuous tubular bowl centrifuges, which enable the separation of ultrafine particles due to high rotation speeds at high throughput rates. Further experimental studies expand the focus from well researched single substance to multi-component systems. Under constant operating conditions, differences in sedimentation velocity determine the percentage of fine and coarse material in the product stream. With enormous centrifugal forces affecting each particle in a collective, the process enables successful fractionation even with small differences in sedimentation velocity, which in turn is influenced by particle size, solid density and density of the dispersion medium. However, the disadvantage of sediment buildup in the rotor persists for any given fractionation step. Therefore, in order to maintain practical viability an online measurement technique is required which aims to counteract the loss of separation efficiency due to sediment buildup by adjusting the rotor speed. The difficulty lies in the acquisition of the above-mentioned, distributed separation criteria in complex multicomponent systems. Furthermore, data processing must allow a clear assessment of the separation efficiency during centrifugation. In light of this, the presented work centers on the development and implementation of said measurement methodology following the multidimensional fractionation using a powerful tubular bowl centrifuge...

Session: L4 - Wet Particle Fractionation
Day: 22 October 2019
Time: 16:45 - 18:00 h

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