Chemical pulping: Electrical resistance tomography for evaluating a medium consistency mixer

Kourunen, Jari; Heikkinen, Lasse; Paananen, Petteri; Peltonen, Kari; Käyhkö, Jari; Vauhkonen, Marko

doi:10.3183/npprj-2011-26-02-p179-185

Cited by 8 publications

(3 citation statements)

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“…ERT was used by Kourunen et al [124] to evaluate the performance of a pilot-scale medium-consistency mixer: Additionally, they compared the obtained results with those from temperature measurements. A 10% (wt/wt) softwood pulp suspension mixture, flowing at a mean velocity of~2.1 m/s, was again quantified based on the mixing index (quotient between the standard deviation of the conductivity distribution and the mean value of the distribution of an image data set).…”

Section: Applications Of Et In the Pulp Suspensions Domainmentioning

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: Applications Of Et In the Pulp Suspensions Domainmentioning

confidence: 99%

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

et al. 2020

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“…ERT was successfully used to assess the temporal variation of the mixing index, based on the CoV, with the changes in operating conditions including chemical flow rate, suspension flow rate, and fiber mass concentration. Kourunen et al applied ERT to assess the mixing efficiency of a pilot‐scale medium consistency mixer and compared the results with those from temperature measurement. Cold water, air, and steam were used as tracers, with mixing quality again based on the CoV.…”

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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“…ERT was successful in monitoring the temporal variation of the mixing index, based on the coefficient of variation (CoV), as a function of the operating conditions, including the chemical flow rate, suspension flow rate, and fiber mass concentration. Kourunen et al 13 applied ERT to assess the performance of a pilot-scale medium-consistency mixer and compared the results with those from temperature measurement. Mixing in a 10 wt % softwood pulp suspension flowing at a mean velocity of ∼2.1 m/s was again quantified based on the CoV.…”

Section: Introductionmentioning

confidence: 99%

Pilot-Scale Examination of Mixing Liquid into Pulp Fiber Suspensions in the Presence of an In-Line Mechanical Mixer

Yenjaichon¹,

Grace²,

Lim³

et al. 2012

Ind. Eng. Chem. Res.

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The quality of liquid mixing into the main stream for an in-line mechanical mixer was investigated for water and pulp suspensions over a range of mass concentrations (0–3.0%), main-stream velocities (0.5–3.0 m/s), jet velocities (3.8–12.6 m/s), and rotational speeds (0–800 rpm) based on electrical resistance tomography and a modified mixing index, derived from the coefficient of variation of conductivity values. The mixing quality was worse when the jet penetrated to the far wall of the pipe for all fiber mass concentrations investigated, whereas this only applied at higher mass concentrations without the impeller. For water flow, the residence time had a significant effect on mixing at higher impeller speeds. With the impeller present, the mixing quality in pulp suspensions improved substantially and was similar to that for water when the flow approached the turbulent regime, with a considerably lower main-stream velocity required for mixing compared to a tee mixer alone. At higher mass concentrations, the energy supplied was insufficient to provide the same level of turbulence as that in water, even at the highest main-stream velocity and impeller speed examined. Improved mixing with increasing impeller speed primarily occurred in the high-shear zone around the impeller, with turbulence decaying rapidly downstream, likely aided by reflocculation.

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Chemical pulping: Electrical resistance tomography for evaluating a medium consistency mixer

Cited by 8 publications

References 0 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

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

Pilot-Scale Examination of Mixing Liquid into Pulp Fiber Suspensions in the Presence of an In-Line Mechanical Mixer

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