Particle de-agglomeration with an in-line rotor-stator mixer at different solids loadings and viscosities

Abstract

In-line rotor-stators are used in a range of energy intensive processes but there is relatively little published work with these devices on which to base process design. This study was performed to investigate the performance of an in-line rotor-stator for the deagglomeration of nanoparticle clusters in a liquid with the objective of determining the effects of solids loading (up to 15%wt) and continuous phase viscosity (up to 100 mPa•s) on the mechanisms and kinetics of breakup and dispersion fineness. A Silverson 150/250MS rotorstator equipped with the EMSC (Emulsor) screen was used in the recirculation loop of a stirred tank charged with 100 litres of pre-dispersion. It was shown that the power number values 2 previously obtained at Reynolds numbers greater than 200,000 are constant at Reynolds numbers as low as 2,400. It was found that the breakup kinetics were not significantly affected by the solids loading, within the range covered in this study. Whilst 10 and 15%wt. pre-dispersions in water were non-Newtonian, during the course of deagglomeration, the dispersion rheology changes resulting in a Newtonian final dispersion of a low viscosity-only slightly higher than that of water. On the other hand, when the viscosity of the continuous phase was increased, the deagglomeration became slower even though the solids concentration was low (1%wt.) and the flow through the rotor-stator was still turbulent. This indicates that it is the flow conditions around the particle and not the bulk rheology of the dispersion that determines the kinetics of the de-agglomeration process. Breakup mechanism was found to be erosion and the dispersion fineness was determined by the size of aggregates.

Chemical and Process Engineering

“…It can therefore be concluded that the characteristic power number values remain constant at Reynolds numbers as low as about 500. Previous work (Padron and Özcan-Taşkın, 2018) with a different rotor-stator had shown this to be the case for Re > 10 3 .…”

Enhancing the Techno-Functional Properties of Lentil Protein Isolate Dispersions Using In-Line High-Shear Rotor-Stator Mixing

“…The results are in agreement with the literature as similar results on the effect of high-shear mixing on particle disruption have been found in the literature for powders. In particular, Pacek et al ( 2007) [42] and Padron and Özcan-Taskin (2018) [46], found that an in-line high-shear mixer at 8000 rpm, caused the reduction of particles of silicon from 90 µm to 9 µm after 20 min and from 100 µm to 15 µm after 30 min of shearing. The authors have also shown that in the timespan used in the present study (<15 min), in-line highshearing did not allow for the disruption of aggregates below 1-2 µm.…”

Yüksek Kayma Gerilmeli Karıştırıcılarda Besleme Hattı Tasarımının Karıştırıcı Performansına Etkisi

“…Buna göre, statordaki delik çapı ve delik sayısının artması ve rotor-stator arasında kalan boşluğun daraltılması topaklaşmayı etkileyici yönde önemli bir etki göstermektedir. Ayrıca ürünlerin karışım hacminde kalma sürelerinin de ürün kalitesini yüksek oranda etkilediği tespit edilmiştir [4] [5] [6].…”