Experimental study of some factors affecting pulp screen capacity

Salem, Hayder; Gooding, Richard; Martinez, D. Mark; Olson, James A.

doi:10.3183/npprj-2014-29-02-p218-224

Cited by 3 publications

(11 citation statements)

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“…The symbols in the contours denote the points where the screen plugs irreversibly. Consistent with the literature (Delfel 2009;Salem 2013), the curves were remarkably linear for all pulp furnishes and screen geometries. The operational window or the range of allowable rotor speeds depended on the slot velocity 𝑉 𝑠 and the ratio of the fibre to slot width ℓ/𝑤.…”

Section: Screen Operational Windowsupporting

confidence: 89%

“…The screening trials were performed with a Beloit MR8 laboratory pressure screen (Fig. 1) similar to that used by Salem (2013). The MR8 is a 212 mm diameter horizontal screen and is equipped with a variable frequency drive (VFD) to control the rotor speed up to 2000 rpm.…”

Section: Methodsmentioning

confidence: 99%

“…Although screens can fail in many ways, this study focused on plugging occurring in the screen apertures. Understanding the limits of screening operation is crucial for screen operators to maximize throughput while reducing power consumption and preventing plugging (Salem 2013). These limits are fundamentally dictated by the interplay between fibre deposition (slot velocity), the pressure pulses created by the rotor (rotor speed), and the rheology of the pulp suspension (Martinez et al 1999;Salem 2013).…”

Section: Introductionmentioning

confidence: 99%

“…It used a series of trials, in which different pulp suspensions and screen geometries were employed. As is typically done in industry as well as in other screening studies (Estevez-Reyes 1995;Salem 2013), plugging was monitored using pressure sensors. Unlike other groups, the pressure fluctuations were examined using the statistical tool that was conceptualized in part one of this study to detect the onset of screen plugging.…”

Section: Introductionmentioning

confidence: 99%

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Understanding the limits of screening operation. Part 2: Characterizing the operational window

Villalba,

Olson,

Martinez

2024

BioRes

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The limits of the pulp screening operation can be defined as the maximum throughput before the apertures start to plug permanently. This two-part article sought insights into the limits of screening operation. In part two, the operational window of the screen was characterized by performing a series of screening trials with different pulp furnishes, where the plugging point was conventionally measured with the pressure signal. The limits of operation, given by a slot velocity and rotor speed contour, showed a robust linear relationship at the point of plugging, which depended on the ratio of the fibre length to aperture size. For size ratios less than 1.5, the screen did not plug under the conditions tested. In addition, the plugging detection tool was conceptualized in part one based on the kurtosis of the distribution of fluctuation peaks, and it was employed here. Effectively, deviations from the Gaussian distribution of the pressure fluctuation peaks signal the onset of screen plugging. Thus, the utility of this tool was confirmed for detecting plugs using readily available pressure fluctuation data in pilot-scale screening operations.

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Section: Screen Operational Windowsupporting

confidence: 89%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Understanding the limits of screening operation. Part 2: Characterizing the operational window

Villalba,

Olson,

Martinez

2024

BioRes

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“…To this end, screens with smaller apertures are operated at progressively lower rotor speeds, higher flow rates and pulp consistencies. Such conditions push the limits of screening operation, where plugging is likely to occur due to the irreversible fibre deposition in the screen apertures (Salem 2013). Screen plugging results in the reduction of the screening efficiency and, in some cases, the sudden stoppage of pulp production (Estevez-Reyes 1995).…”

Section: Introductionmentioning

confidence: 99%

Understanding the limits of a screening operation. Part 1: Characterization of screen plugging

Villalba,

Olson,

Martinez

2024

BioRes

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Pressure screening is a critical step in the production of high-quality paper. In efforts to meet sustainable market demands, mill operators are forced to push the limits of screening operation to the point where plugging becomes a recurrent issue. This two-part study provides insights into the limits of screening operations. In the first part, some published imaging data was analyzed to delve into the plugging mechanisms. The observed hysteresis and intermittency were measured by image processing techniques, which revealed that an intermittent behavior of plug-and-release events is intensified as permanent, stable plugs start to form. The intermittency was characterized as changes in the distribution of open area fluctuation peaks. Thus, the kurtosis of the fluctuation peak distribution is proposed as a metric for a plugging soft-sensor. In part 2 of this investigation, the limits of screening operation were characterized by performing a series of screening trials. The utility of the soft-sensor metric for plugging was assessed with the pressure fluctuation data.

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Model and optimal operational windows for hydrodynamic fiber fractionation

Schmid

Radl²

2020

Nordic Pulp &Amp; Paper Research Journal

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Based on fitted experimental data, an empirical fractionation model for mini-channel hydrodynamic fiber fractionation (miniFrac) is presented. This model, combined with an optimization procedure, is then used as a design tool to synergize competing fractionation performance characteristics, i. e., product quality, product yield and energy demand. Based on this model, miniFrac is compared to state-of-the-art fiber fractionation technology with respect to (i) long fiber-short fiber fractionation and (ii) fines-fiber fractionation. In terms of fines-fiber fractionation, miniFrac is outperformed by typical micro-hole pressure screening regarding the purity of fines fraction. However, a comparison with a slotted (slot width of 0.2 mm) and a smooth-holed pressure screen (hole diameter of 0.8 mm) shows, that miniFrac is capable of outperforming both systems regarding product quality and energy demand at a comparable product yield. If, in the case of fines-fiber fractionation, reject purity (i. e., fines exclusion) is more important than fines purity (i. e., long fiber remain in the reject), miniFrac is an interesting tool with some key advantages over pressure screens.

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Experimental study of some factors affecting pulp screen capacity

Cited by 3 publications

References 0 publications

Understanding the limits of screening operation. Part 2: Characterizing the operational window

Understanding the limits of screening operation. Part 2: Characterizing the operational window

Understanding the limits of a screening operation. Part 1: Characterization of screen plugging

Model and optimal operational windows for hydrodynamic fiber fractionation

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