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Scientific background

Treatment of Pulp in a Kneader and Disperger presented by Johannes Leitner johannes.leitner@student.tugraz.at. Scientific background. State of the art: Deflaking and refining in single disk refiners at high energy demand Pronounced effect of consistency

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Scientific background

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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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