Flow pattern, periodicity and energy dissipation in a batch rotor–stator mixer

Utomo, Adi T.; Baker, M. R.; Pacek, Andrzej W.

doi:10.1016/j.cherd.2008.07.012

Cited by 89 publications

(71 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The power numbers for the MICCRA D-9 and VMI were found to be 2.56 and 2.40 respectively. This is within the range of power numbers for batch rotor-stators in the turbulent regime: 1-3 (Padron, 2001;Utomo et al, 2008). Doucet et al (2005), who used a slightly different VMI geometry which had a stator with 8 circular orifices on the upper part, in addition to the slots on the side and a rotor which only included the 4-bladed impeller, reported a comparable power number of 3.0 in the turbulent regime.…”

Section: -Vp Field Emission Gun Scanning Electron Microscope (Fegsupporting

confidence: 52%

Dispersion of clusters of nanoscale silica particles using batch rotor-stators

Kamaly

Tarleton

Özcan-Taşkın

2017

Advanced Powder Technology

View full text Add to dashboard Cite

Nanoparticle powders added into a liquid medium form structures which are much larger than the primary particle size (aggregates and agglomerates)-typically of the order of 10's of microns. An important process step is therefore the deagglomeration of these clusters to achieve as fine a dispersion as possible. This paper reports the findings of a study on the dispersion of hydrophilic fumed silica nanoparticle clusters, Aerosil 200V, in water using two batch rotor-stators: MICCRA D-9 and VMI. The MICCRA D-9 head consists of a set of teeth for the stator and another for the rotor, whereas the VMI has a stator with slots and a rotor which consists of a 4-bladed impeller attached to an outer set of teeth. The dispersion process, studied at different power input values and over a range of concentrations (1, 5, 10 wt.%), was monitored through the evolution of PSD. Erosion was found to be the dominant breakage mechanism irrespective of operating conditions or rotor-stator type. The smallest attainable size was also found to be independent of the power input or the design of the rotor-stator. Break up kinetics increased upon the increase of power input, and this also depended on the rotor-stator design. With MICCRA D-9 which has smaller openings on both the stator and rotor, the break up rate was faster. Increasing the particle concentration decreased break up kinetics. It could also be shown that operating at high concentrations can still be beneficial as the break up rate is higher when assessed on the basis of specific power input per mass of solids.

show abstract

Section: -Vp Field Emission Gun Scanning Electron Microscope (Fegsupporting

confidence: 52%

Dispersion of clusters of nanoscale silica particles using batch rotor-stators

Kamaly

Tarleton

Özcan-Taşkın

2017

Advanced Powder Technology

View full text Add to dashboard Cite

show abstract

“…When N is at its maximum value (18 krpm), then Re Blade ¼ 10 6 , far above the value of Re Blade $ 10 4 where turbulence becomes fully developed. 37 We suggest that it is this turbulence that produces local shear rates that are high enough to result in exfoliation.…”

Section: Exfoliation Mechanismmentioning

confidence: 92%

“…In a high-shear rotor-stator mixer, very high shear rates are achieved in the gap between the rotor and stator and in the holes in the stator. 26,37 This means graphene production is probably localised in the vicinity of the rotor-stator. However, for a rotating-blade mixer no such well-dened, highly localised regions of high shear exist.…”

Section: Exfoliation Mechanismmentioning

confidence: 99%

Turbulence-assisted shear exfoliation of graphene using household detergent and a kitchen blender

et al. 2014

View full text Add to dashboard Cite

To facilitate progression from the lab to commercial applications, it will be necessary to develop simple, scalable methods to produce high quality graphene. Here we demonstrate the production of large quantities of defect-free graphene using a kitchen blender and household detergent. We have characterised the scaling of both graphene concentration and production rate with the mixing parameters: mixing time, initial graphite concentration, rotor speed and liquid volume. We find the production rate to be invariant with mixing time and to increase strongly with mixing volume, results which are important for scale-up. Even in this simple system, concentrations of up to 1 mg ml À1 and graphene masses of >500 mg can be achieved after a few hours mixing. The maximum production rate was $0.15 g h À1 , much higher than for standard sonication-based exfoliation methods. We demonstrate that graphene production occurs because the mean turbulent shear rate in the blender exceeds the critical shear rate for exfoliation.Over the last decade, graphene has become one of the most studied of all nano-materials due to its 2-dimensional structure and its unique set of physical properties. 1,2 During this period, the focus of much of the research community has been on mapping out and understanding the fundamental physics and chemistry of graphene. However, in recent years, the emphasis has started to shi slightly towards the demonstration of applications. 3 Over the next few years, we expect the emphasis to shi further as both academic and industrial researchers concentrate on fullling the applications potential of graphene, eventually leading to a range of graphene-enabled products.However, before this can be achieved, it will be critically important to develop industrially scalable production methods for graphene. While graphene can be produced by a range of techniques, many applications will require solution-processed 4 graphene. In particular, a number of applications will require access to large volumes of graphene dispersions or inks. Using standard solution deposition techniques such as inkjet printing 5,6 or spray coating, 7,8 such inks can be used to prepare a range of lms, coatings or patterned structures. In particular, applications in areas such as printed electronics will require the production of conductive lms or traces. Here, defect free graphene performs particularly well, giving high conductivity structures without high temperature post treatments. 5 Thus, it is clear that large scale production techniques for defect-free graphene are urgently required.Defect free graphene is generally produced by sonicating graphite powder either in certain solvents 9-16 or aqueous surfactant 17-23 solutions. The sonication tends to break up the graphite crystallites as well as exfoliating them to give large number of graphene nanosheets. 11 Raman spectroscopy 15,24,25 shows this method to produce negligible quantities of basal plane defects while XPS shows the akes to be un-oxidised. 14 While the graphene produced by this m...

show abstract

“…Yoon et al [16] investigated the flow in a Rushton turbine using PIV. Utomo et al [17] combined LDV and computational simulations to quantify the flow patterns and energy dissipation in a batch rotor-stator mixer. These studies have shown the utility in applying non-intrusive diagnostic technique to better understand the flow fields in these devices.…”

Section: I1 Backgroundmentioning

confidence: 99%

Characterization of Mixing in a Simple Paddle Mixer Using Experimentally Derived Velocity Fields

Bohl¹,

Mehta

Santitissadeekorn

et al. 2011

Journal of Fluids Engineering

View full text Add to dashboard Cite

The flow field in a cylindrical container driven by a flat bladed impeller was investigated using Particle Image Velocimetry (PIV). Three Reynolds numbers (0.02, 8, 108) were investigated for different impeller locations within the cylinder. The results showed that vortices were formed at the tips of the blades and rotated with the blades. As the blades were placed closer to the wall the vortices interacted with the induced boundary layer on the wall to enhance both regions of vorticity. Finite Time Lyapunov Exponents (FTLE) were used to determine the Lagrangian Coherent Structure (LCS) fields for the flow. These structures highlighted the regions where mixing occurred as well as barriers to fluid transport. Mixing was estimated using zero mass particles convected by numeric integration of the experimentally derived velocity fields. The mixing data confirmed the location of high mixing regions and barriers shown by the LCS analysis. The results indicated that mixing was enhanced within the region described by the blade motion as the blade was positioned closed to the cylinder wall. The mixing average within the entire tank was found to be largely independent of the blade location and flow Reynolds number.

show abstract

Flow pattern, periodicity and energy dissipation in a batch rotor–stator mixer

Cited by 89 publications

References 10 publications

Dispersion of clusters of nanoscale silica particles using batch rotor-stators

Dispersion of clusters of nanoscale silica particles using batch rotor-stators

Turbulence-assisted shear exfoliation of graphene using household detergent and a kitchen blender

Characterization of Mixing in a Simple Paddle Mixer Using Experimentally Derived Velocity Fields

Contact Info

Product

Resources

About