A comparison between powder flow property testers

Salehi, Hamid; Barletta, Diego; Poletto, Massimo

doi:10.1016/j.partic.2016.08.003

Cited by 52 publications

(34 citation statements)

References 25 publications

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“…While results from RST-01 and RST-XS are in good agreement, a considerable deviation (up to 20 %) was observed when comparing results from the Schulze ring shear tester to the Jenike shear tester. Similar outputs are found by other researchers (Berry et al, 2015;Koynov et al, 2015;Salehi et al, 2017), where yield loci from the Brookfield powder flow tester, the Schulze ring shear tester, the FT4 powder rheometer and the Jenike shear tester are compared. The Brookfield powder flow tester and the FT4 powder rheometer show systematically lower shear responses in comparison to the other two shear testers.…”

Section: Introductionsupporting

confidence: 77%

Effect of Particle Size and Cohesion on Powder Yielding and Flow

Shi

Mohanty

Chakravarty

et al. 2018

KONA

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The bulk properties of powders depend on material characteristics and size of the primary particles. During storage and transportation processes in the powder processing industry, the material undergoes various modes of deformation and stress conditions, e.g., due to compression or shear. In many applications, it is important to know when powders are yielding, i.e. when they start to flow under shear; in other cases it is necessary to know how much stress is needed to keep them flowing. The measurement of powder yield and flow properties is still a challenge and will be addressed in this study. In the framework of the collaborative project T-MAPPP, a large set of shear experiments using different shear devices, namely the Jenike shear tester, the ELE direct shear tester, the Schulze ring shear tester and the FT4 powder rheometer, have been carried out on eight chemically-identical limestone powders of different particle sizes in a wide range of confining stresses. These experiments serve two goals: i) to test the reproducibility/ consistency among different shear devices and testing protocols; ii) to relate the bulk behaviour to microscopic particle properties, focusing on the effect of particle size and thus inter-particle cohesion. The experiments show high repeatability for all shear devices, though some of them show more fluctuations than others. All devices provide consistent results, where the FT4 powder rheometer gives lower yield/steady state stress values, due to a different pre-shearing protocol. As expected, the bulk cohesion decreases with increasing particle size (up to 150 μm), due to the decrease of inter-particle cohesion. The bulk friction, characterized in different ways, is following a similar decreasing trend, whereas the bulk density increases with particle size in this range. Interestingly, for samples with particle sizes larger than 150 μm, the bulk cohesion increases slightly, while the bulk friction increases considerably-presumably due to particle interlocking effects-up to magnitudes comparable to those of the finest powders. Furthermore, removing the fines from the coarse powder samples reduces the bulk cohesion and bulk density, but has a negligible effect on the bulk friction. In addition to providing useful insights into the role of microscopically attractive, van der Waals, gravitational and/or compressive forces for the macroscopic bulk powder flow behaviour, the experimental data provide a robust database of cohesive and frictional fine powders for industrially relevant designs such as silos, as well as for calibration and validation of models and computer simulations.

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Section: Introductionsupporting

confidence: 77%

Effect of Particle Size and Cohesion on Powder Yielding and Flow

Shi

Mohanty

Chakravarty

et al. 2018

KONA

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“…f) shear tester: this technique has been used to measure caking of particulate materials at room conditions or elevated temperature, humidity and consolidation stress [30][31][32]. The details of shear tester principles have been illustrated elsewhere [33]. This method is time consuming, since powder will be consolidated for a desired period of time before a single point in yield locus line can be measured.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…The unconfined yield strength in powder shear tester is a property derived from the static yield locus through the determination of the unconfined yield Mohr circle. This parameter, therefore, is a combined function of the material cohesion, c, and also of the static angle of internal friction, ϕ[33]. These parameters are reported inTable 1.…”

mentioning

confidence: 99%

Development and application of a novel cake strength tester

et al. 2019

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Caking can cause many problems in industries during processing or storage of particulate materials. Caking magnitude depends on several factors, for instance temperature, consolidation stress and storage time. In this research paper, a novel force displacement and easy-to-use caking tester for measuring quantitatively cake strength as a result of elevated temperature, consolidation stress and storage time is introduced. The developed tester outweighed the conventional uniaxial unconfined failure caking tester due to the defined location of the failure plane to maximise repeatability, the necessity for a lower quantity of powder, maximised exposed surface and lower wall friction as well as production costs. The experimental design has been conducted by changing the temperature, consolidation stress and storage duration. The results showed that the tester could distinguish cake strength between different experimental conditions. A statistical model has been successfully developed to study the effect of each variable on the cake strength.

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“…Leturia M. et al (2014) have convincingly shown that one or more appropriate measurement techniques should often be applied in order to get an understanding of the product's flow properties under realistic conditions. Surprisingly, Salehi H. et al (2017) have recently shown that even similar methodologies working with the conventional Jenike shear and ring shear principle can provide inconsistent results. This all makes a reliable assessment of the powder flow properties a complicated task.…”

Section: Introductionmentioning

confidence: 99%

Real-time in-situ Rheological Assessment of Sticky Point Temperature and Humidity of Powdered Products

Groen

Kooijman

Belzen

et al. 2020

KONA

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Unwanted changes in powder flow behavior can unexpectedly occur when a product is exposed to certain conditions of temperature and humidity. This can happen during production, but also during transport or storage. The work reported here demonstrates the novel approach of using an amended powder rheology setup for measuring and predicting such changes in powder flow behavior. The developed methodology makes it possible to vary in-situ the temperature and the relative humidity of the air to which the product is exposed, thereby mimicking realistic conditions of production or related unit operations. An air flow capable of fluidizing the powder particles is controlled at a specific constant temperature and its relative humidity can be altered while measuring the torque in the fluidized powder bed in real time. The fluidization is necessary for generating a homogeneous introduction of temperature and relative humidity. Results obtained using citric acid and commercial coffee whitener products have proven this methodology to provide both similar and in certain instances dissimilar results compared to the more established methodology such as measuring the vapour adsorption isotherms. These observations are explained. In this way, it can be predicted under which combinations of temperature and humidity a product does or does not become sticky. The main advantages of our approach are that the flow properties are directly assessed, the interpretation of the obtained data is more straightforward and that the measurement times are shortened substantially.

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A comparison between powder flow property testers

Cited by 52 publications

References 25 publications

Effect of Particle Size and Cohesion on Powder Yielding and Flow

Effect of Particle Size and Cohesion on Powder Yielding and Flow

Development and application of a novel cake strength tester

Real-time in-situ Rheological Assessment of Sticky Point Temperature and Humidity of Powdered Products

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