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Validation of a Discrete Element Method (DEM) Model of the Grinding Media Dynamics within an Attritor Mill Using Positron Emission Particle Tracking (PEPT) Measurements

1
Johnson Matthey Technology Centre, P.O. Box 1, Belasis Avenue, Billingham, Cleveland TS23 1LB, UK
2
School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, UK
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Johnson Matthey Technology Centre, Blount’s Court, Sonning Common RG4 9NH, UK
*
Author to whom correspondence should be addressed.
Appl. Sci. 2019, 9(22), 4816; https://doi.org/10.3390/app9224816
Received: 20 October 2019 / Revised: 6 November 2019 / Accepted: 8 November 2019 / Published: 11 November 2019
Positron emission particle tracking (PEPT) was used to investigate the grinding media dynamics in a laboratory-scale attritor mill in the absence of powder. The grinding media motion was analysed as a function of the equipment’s typical operating parameters: impeller speed, impeller clearance and bead fill level. It was observed that the impeller speed had the strongest influence on the media motion. An increase of the impeller speed from 300 rpm to 600 rpm led to a change in the bead recirculation patterns with the increasing formation of well segregated upper and lower recirculation loops that fully developed at the maximum speed of 600 rpm. For a constant impeller speed, an increase of the bead loading did not majorly affect the bead velocity as remarked by minor changes on the flow field. For all the impeller clearance values, the occupancy plots revealed an inefficient dead region at the bottom of the attritor where the beads were moving at very low velocity. In this region the beads were tightly packed under their own weight and, furthermore, there was an absence of direct contact with the impeller arms. The depth of this region increased proportionally to the distance between the bottom of the impeller and the vessel base indicating that a minimum value of clearance should be set to optimise the lower recirculation pattern. For two experimental conditions, the data generated by PEPT measurements were utilised to set-up a friction-adjusted discrete element method (DEM) model. Here, the simulation results were qualitatively and quantitatively compared against the PEPT data by assessing the averaged velocity flow fields and the average velocity profiles at different radial locations inside the vessel. Given the intrinsic uncertainty of the PEPT measurements, the DEM model results were in considerably good agreement with the experimental results. The major discrepancy was observed close to the vessel wall where the simulations overpredicted the velocity by about 10%. View Full-Text
Keywords: vertical stirred mill; grinding media motion; positron emission particle tracking (PEPT); discrete element method (DEM) simulations; coarse graining; validation vertical stirred mill; grinding media motion; positron emission particle tracking (PEPT); discrete element method (DEM) simulations; coarse graining; validation
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MDPI and ACS Style

Daraio, D.; Villoria, J.; Ingram, A.; Alexiadis, A.; Hugh Stitt, E.; Marigo, M. Validation of a Discrete Element Method (DEM) Model of the Grinding Media Dynamics within an Attritor Mill Using Positron Emission Particle Tracking (PEPT) Measurements. Appl. Sci. 2019, 9, 4816. https://doi.org/10.3390/app9224816

AMA Style

Daraio D, Villoria J, Ingram A, Alexiadis A, Hugh Stitt E, Marigo M. Validation of a Discrete Element Method (DEM) Model of the Grinding Media Dynamics within an Attritor Mill Using Positron Emission Particle Tracking (PEPT) Measurements. Applied Sciences. 2019; 9(22):4816. https://doi.org/10.3390/app9224816

Chicago/Turabian Style

Daraio, Domenico; Villoria, Jose; Ingram, Andrew; Alexiadis, Alessio; Hugh Stitt, E.; Marigo, Michele. 2019. "Validation of a Discrete Element Method (DEM) Model of the Grinding Media Dynamics within an Attritor Mill Using Positron Emission Particle Tracking (PEPT) Measurements" Appl. Sci. 9, no. 22: 4816. https://doi.org/10.3390/app9224816

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