Techniques for visualization of cavern boundaries in opaque industrial mixing systems

Simmons, Mark; Edwards, I.; Hall, Joseph W.; Fan, Xianfeng; Parker, D.J.; Stitt, E. Hugh

doi:10.1002/aic.11889

Cited by 27 publications

(20 citation statements)

References 10 publications

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“…In contrast, storage and mixing containers, which can be found in industrial processes in large number, and which vary with respect to their size, purpose, etc., are the second most studied application area using ET. In particular, researchers have focused on stirred containers possessing various baffles and mixing characteristics with diameters in the interval 15-40 cm [98,99], and on plant-scale containers with diameters of around 150 cm [100,101].…”

Section: Operating Apparatusmentioning

confidence: 99%

Electrical Tomography: A Review of Configurations, and Application to Fibre Flow Suspensions Characterisation

et al. 2020

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Understanding the behaviour of suspension flows continues to be a subject of great interest considering its industrial relevance, regardless of the long time and effort dedicated to it by the scientific and industrial communities. Information about several flow characteristics, such as flow regimen, relative velocity between phases, and spatial distribution of the phases, are essential for the development of exact models for description of processes involving pulp suspension. Among the diverse non-invasive techniques for flow characterisation that have been reported in the literature for obtaining experimental data about suspension flow in different processes, Electrical Tomography is one of the most interesting, since it presents perhaps the best compromise among cost, portability, and, above all, safety of handling (indeed there is no need to use radiation, which requires special care when using it). In this paper, a brief review and comparison between existing technologies for pulp suspension flow monitoring will be presented, together with their strengths and weaknesses. Emphasis is given to Electrical Tomography, because it offers the above-mentioned compromise and thus was the strategy adopted by the authors to characterise different flow processes (solid–liquid, liquid–liquid, fibres, etc.). The produced portable EIT system is described, and examples of results of its use for pulp suspension flow characterisation are reported and discussed.

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Section: Operating Apparatusmentioning

confidence: 99%

Electrical Tomography: A Review of Configurations, and Application to Fibre Flow Suspensions Characterisation

et al. 2020

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“…Among the latter, measurements of the fluid velocity were done using hot film anemometry (Solomon et al 1981 ), Laser Doppler Anemometry, LDA, (Moore et al 1995 ; Jaworski et al 1994 ; Jaworski 2006 ), ultrasonic doppler velocimetry, UDV, (Ein-Mozaffari and Upreti, 2009 ; Hui et al 2009 ; Saeed et al 2007 ) or Particle Image Velocimetry, PIV, (Arratia et al 2006 ; Gabelle et al 2013 ). Other investigation methods include flow observation using tracer particles (Arratia et al 2006 ), visualization using dye (Amanullah et al 1997 ; Galindo and Nienow 1992 ), X-ray photography (Elson et al 1986 ), electrical resistivity tomography, (Hui et al 2009 ; Pakzad et al 2008 ; Simmons et al 2009 ), or even freezing (Wilkens et al 2005 ). The studies were performed for different impellers, e.g.…”

Section: Introductionmentioning

confidence: 99%

A new model of cavern diameter based on a validated CFD study on stirring of a highly shear-thinning fluid

Story

Jaworski

2017

Chem. Pap.

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Results of numerical simulations of momentum transfer for a highly shear-thinning fluid (0.2% Carbopol) in a stirred tank equipped with a Prochem Maxflo T type impeller are presented. The simulation results were validated using LDA data and both tangential and axial force measurements in the laminar and early transitional flow range. A good agreement between the predicted and experimental results of the local fluid velocity components was found. From the predicted and experimental values of both tangential and axial forces, the power number, Po, and thrust number, Th, were also calculated. Values of the absolute relative deviations were below 4.0 and 10.5%, respectively, for Po and Th, which confirms a satisfactory agreement with experiments. An intensive mixing zone, known as cavern, was observed near the impeller. In this zone, the local values of fluid velocity, strain rate, Metzner–Otto coefficient, shear stress and intensity of energy dissipation were all characterized by strong variability. Based on the results of experimental study a new model using non-dimensional impeller force number was proposed to predict the cavern diameter. Comparative numerical simulations were also carried out for a Newtonian fluid (water) and their results were similarly well verified using LDA measurements, as well as experimental power number values.

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“…Electrical resistance tomography (ERT) is a noninvasive technique, used recently to evaluate mixing in various processes . It has also been used to assess the efficiency of in‐line mixers in pulp and paper processes.…”

Section: Introductionmentioning

confidence: 99%

In‐line jet mixing of liquid‐pulp‐fiber suspensions: Effect of fiber properties, flow regime, and jet penetration

et al. 2012

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Mixing effectiveness was determined experimentally for side jet injection into pipe flow for water and pulp suspensions for a range of fiber mass concentrations (0-3.0%), mainstream velocities (0.5-5.0 m/s), and side-stream velocities (1.0-12.7 m/s). The mixing quality was measured in cross-sectional planes along the pipe using electrical resistance tomography and quantified by a modified mixing index, derived from the coefficient of variation of conductivity. Mixing depended strongly on the flow regime and jet penetration. For turbulent flow, the criteria for in-line jet mixing in water are applicable to the mixing in suspensions, with small differences likely due to differences in fiber network strength and influences of fiber-turbulence interactions in modifying turbulent structures in the bulk. When a suspension flows as a plug, however, the mixing differs greatly from that in water, depending on the fiber network strength in the core of the pipe.

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Techniques for visualization of cavern boundaries in opaque industrial mixing systems

Cited by 27 publications

References 10 publications

Electrical Tomography: A Review of Configurations, and Application to Fibre Flow Suspensions Characterisation

Electrical Tomography: A Review of Configurations, and Application to Fibre Flow Suspensions Characterisation

A new model of cavern diameter based on a validated CFD study on stirring of a highly shear-thinning fluid

In‐line jet mixing of liquid‐pulp‐fiber suspensions: Effect of fiber properties, flow regime, and jet penetration

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