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Insights into Pulp Treatment: Kneading and Disperging Effects on Fiber Properties

This study investigates the treatment of unbleached softwood kraft pulp using a kneader and disperger. The research examines the effects of different operational parameters such as consistency, treatment time, and temperature on pulp fiber morphology, including curl, fibrillation, and fines content. Key findings reveal that lower consistency leads to reduced curl and dewatering efficiency. The kneader enhances fiber shortening and increases fibrillation and fines, while the disperger demonstrates slower curl increases but significant changes in water retention value. The findings offer insights into optimizing pulp treatment technologies for improved recycling processes.

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Insights into Pulp Treatment: Kneading and Disperging Effects on Fiber Properties

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  1. Treatment of Pulp in a Kneader and Dispergerpresentedby Johannes Leitnerjohannes.leitner@student.tugraz.at

  2. Scientific background • State of the art: • Deflaking and refining in single disk refiners at high energydemand • Pronouncedeffect of consistency • Kneading and dispergingis a well established technology forrecycledpulp • Study thebehaviour of disperging and kneading of unbleachedsoftwood kraft pulpandtheeffect on fiberdefects • Temperaturebelow 100 °C • Effect of Consistency • Kneading/DispersingIntensity

  3. Equipment and pre-studies • Trials performed in STSM at PMV Darmstadt, Germany • KneaderDisperger • 0 - 30- 60rpmBothFrequencymodulated0- 1200-1500 rpm • 30 g optimal Sample weight 60 g • InlinepreheatingPreparationsno-preheating • 7,5 – 60 minutestreatment time 1-2 minutes

  4. Materials and methods • Material • Unbleachedsoftwood kraft pulp at Kappa 45 • Methods • Fiber morphologyusingMetsoFiberlab • Lengthweightedfiberlength • Curl and Kink/m • Fibrillation and Finescontent • SchopperRiegler • Water retentionvalue - internalstandard • Sample werewashed to conductivitybelow 10 µS/cm • Suspension adjusted to pH 9.1 byNaOH • Centrifuged at 4000 rpm, for 30 minutes

  5. Results and InterpretationSR & Curl in thedisperger • Decreasedconsistencyshowslowercurlandslowerdewatering • Extremelyhighcurland fast dewateringatlongertreatmenttimes

  6. Results and Interpretation SR & Curl in thedisperger • Disintegratedpulp in a kneader (left) and disperger (right) • Disperger: Long intensive treatmentresults in inacceptablenodularstructure of pulpeven after 30 000 revolutions in thedisintegrator Kneader Disperger

  7. Results and Interpretation SR & Curl in thekneader • Disintegratedpulp in a kneader (left) and disperger (right) • Fasterincrease in fibercurl at lower rotation speed • Nosignificantchange in Schopper Riegler

  8. Results and InterpretationFiber length, Fibrillation and Fines Comparisonbetweenkneader and disperger at 35% consistency , pulp at roomtemperatureand ~ 800 revolutions • Kneadingresulted in • significantfibershorteningdue to sharpedges • significantlyhigherfibrillation and finescontent

  9. Results and InterpretationFiber Swelling and DryContent Effect of temperature in thekneader and treatment in thedisperger at 35% consistency • High shear in theopendispergerresults in drying and hornification. Effectsarerelated to lab construction! • Increasedtemperature in thekneaderresults in lesshornification

  10. Summary Disperger: • Slowerincrease in fibercurl; high at intensive treatment • Pronouncedeffect of consistency • Interestingresultsfor SR, WRV and drycontent • Moderate fibercutting and increase in finesandfibrillation • Kneader: • Very fast increase in fibercurl • Minorrole of consistency • Moderate decrease in WRV and dry content • Same orlower SR • High fibercutting and strongerincrease in finesandfibrillation

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