On the use of a powder rheometer to characterize the powder flowability at low consolidation with torque resistances

Salehi, Hamid; Poletto, Massimo; Schütz, Denis; Romirer, Richard

doi:10.1002/aic.15934

Cited by 24 publications

(9 citation statements)

References 32 publications

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“…The cell containing the powder is made of a glass cylinder with a porous bottom plate, and the unit is equipped with impellers of different shapes and wall conditions. Salehi et al (2017b) used an APPC to study the effects of the impeller depth and the aeration rate on the torque acting on a flat blade impeller in samples of free-flowing powders, namely glass beads, alumina and sieved silica sand, up to the minimum fluidisation (0 < FI < 1). The dependency of T on the air velocity, the bed height and the impeller depth confirm the observations of Bruni et al (2005;2007).…”

Section: R8mentioning

confidence: 99%

From Quasi-static to Intermediate Regimes in Shear Cell Devices: Theory and Characterisation

Francia

Yahia

Ocone

et al. 2021

KONA

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The design of new technology for processing and manufacturing particulate products requires understanding granular rheology over a broad range of conditions. Powders display a complex behaviour due to their ability to rearrange under stress, and as a result, granular flow is generally classified into three flow regimes, namely a quasi-static regime dominated by frictional contacts, an inertial regime dominated by collisional and kinematic stresses and an intermediate regime where the three sources of stress are important to establish a stress-strain rate relationship. Characterisation of the flowability is generally restricted to the flow initiation in quasi-static regime, even if, transition into inertial conditions is very common in practical applications involving the control of dense flows, such as powder handling, particle formation processes or additive manufacturing. This work presents a critical review of available techniques to characterise the departure from the quasi-static regime into an intermediate flow. We revise the application of shear cells and present different strategies to modify classic devices with external actuation, such as aeration, to operate at higher inertial numbers. We pay particular attention to innovative designs using aerated Couette flow configurations, highlight the complexity in the standardisation and the challenges in advancing towards a universal model.

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Section: R8mentioning

confidence: 99%

From Quasi-static to Intermediate Regimes in Shear Cell Devices: Theory and Characterisation

Francia

Yahia

Ocone

et al. 2021

KONA

View full text Add to dashboard Cite

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“…The powder bed can also be conditioned prior to torque measurement to remove any residual vertical friction due to insertion of the impeller in the bed. Recently, Salehi et al (2017), evaluated the Anton Paar powder cell for characterising flowability at low stresses using glass beads, sand and alumina powder. They reported that the minimum torque necessary to rotate an impeller in a powder bed depends on material properties, air flow rate, impeller depth and shape of the impeller.…”

Section: Powder Cell Of the Anton Paar Modular Compact Rheometermentioning

confidence: 99%

“…By introducing the permeating air, the powder flow, which is initially in the quasistatic state, could transform into the intermediate or even dynamic state, where the bulk friction coefficient is shown to increase almost linearly with the inertial number. Bruni et al (2007Bruni et al ( , 2005 and Tomasetta et al (2012) used a mechanically stirred fluid-bed rheometer to study the rheology of aerated and fluidised powders, which was followed by Salehi et al (2017Salehi et al ( , 2018. To keep the bed in quasi-static state, the rotational speed of the impeller and gas superficial velocity were chosen to have low values.…”

Section: Effect Of Shear Strain Rate and Medium Fluid Dragmentioning

confidence: 99%

Cohesive Powder Flow: Trends and Challenges in Characterisation and Analysis

Ghadiri

Nan

Hare

et al. 2020

KONA

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Powder processing and manufacturing operations are rate processes for which the bottleneck is cohesive powder flow. Diversity of material properties, particulate form, and sensitivity to environmental conditions, such as humidity and tribo-electric charging, make its prediction very challenging. However, this is highly desirable particularly when addressing a powder material for which only a small quantity is available. Furthermore, in a number of applications powder flow testing at low stress levels is highly desirable. Characterisation of bulk powder failure for flow initiation (quasi-static) is well established. However, bulk flow parameters are all sensitive to strain rate with which the powder is sheared, but in contrast to quasi-static test methods, there is no shear cell for characterisation of the bulk parameters in the dynamic regime. There are only a handful of instruments available for powder rheometry, in which the bulk resistance to motion can be quantified as a function of the shear strain rate, but the challenge is relating the bulk behaviour to the physical and mechanical properties of constituting particles. A critique of the current state of the art in characterisation and analysis of cohesive powder flow is presented, addressing the effects of cohesion, strain rate, fluid medium drag and particle shape.

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“…Particulate materials should ideally retain their desired flow properties during processing, handling and storage as well as through the distribution chain to the final consumer [1]. These types of reduction in the handling behaviour of particulate materials can lead to huge costs being imposed on industries [2]. Such costs justify the need for developing a tester for measuring as well as means for predicting caking at industrial scales.…”

Section: Accepted Manuscriptmentioning

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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On the use of a powder rheometer to characterize the powder flowability at low consolidation with torque resistances

Cited by 24 publications

References 32 publications

From Quasi-static to Intermediate Regimes in Shear Cell Devices: Theory and Characterisation

From Quasi-static to Intermediate Regimes in Shear Cell Devices: Theory and Characterisation

Cohesive Powder Flow: Trends and Challenges in Characterisation and Analysis

Development and application of a novel cake strength tester

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