Institute for Paper, Pulp and Fiber Technology Professor Horst Cerjak, Johannes Leitner Coimbra, 9th of May 2014 Treatment of Pulp in a Kneader and Disperger presented by Johannes Leitner

Institute for Paper, Pulp and Fiber Technology Professor Horst Cerjak, Johannes Leitner Coimbra, 9th of May 2014 Scientific background State of the art: Deflaking and refining in single disk refiners at high energy demand Pronounced effect of consistency Kneading and disperging is a well established technology for recycled pulp Study the behaviour of disperging and kneading of unbleached softwood kraft pulp and the effect on fiber defects Temperature below 100 °C Effect of Consistency Kneading/Dispersing Intensity

Institute for Paper, Pulp and Fiber Technology Professor Horst Cerjak, Johannes Leitner Coimbra, 9th of May 2014 Equipment and pre-studies Trials performed in STSM at PMV Darmstadt, Germany KneaderDisperger rpm Both Frequency modulated rpm 30 g optimal Sample weight60 g Inline preheating Preparations no-preheating 7,5 – 60 minutestreatment time1-2 minutes

Institute for Paper, Pulp and Fiber Technology Professor Horst Cerjak, Johannes Leitner Coimbra, 9th of May 2014 Materials and methods Material Unbleached softwood kraft pulp at Kappa 45 Methods Fiber morphology using Metso Fiberlab Length weighted fiber length Curl and Kink/m Fibrillation and Fines content Schopper Riegler Water retention value - internal standard Sample were washed to conductivity below 10 µS/cm Suspension adjusted to pH 9.1 by NaOH Centrifuged at 4000 rpm, for 30 minutes

Institute for Paper, Pulp and Fiber Technology Professor Horst Cerjak, Johannes Leitner Coimbra, 9th of May 2014 Results and Interpretation SR & Curl in the disperger Decreased consistency shows lower curl and slower dewatering Extremely high curl and fast dewatering at longer treatment times

Institute for Paper, Pulp and Fiber Technology Professor Horst Cerjak, Johannes Leitner Coimbra, 9th of May 2014 Results and Interpretation SR & Curl in the disperger Disintegrated pulp in a kneader (left) and disperger (right) Disperger: Long intensive treatment results in inacceptable nodular structure of pulp even after revolutions in the disintegrator KneaderDisperger

Institute for Paper, Pulp and Fiber Technology Professor Horst Cerjak, Johannes Leitner Coimbra, 9th of May 2014 Results and Interpretation SR & Curl in the kneader Disintegrated pulp in a kneader (left) and disperger (right) Faster increase in fiber curl at lower rotation speed No significant change in Schopper Riegler

Institute for Paper, Pulp and Fiber Technology Professor Horst Cerjak, Johannes Leitner Coimbra, 9th of May 2014 Results and Interpretation Fiber length, Fibrillation and Fines Fiber propertyNo treatmentKneaderDisperger Lw Fiber Length [mm] 2.57 mm2.2 mm2.46 mm Fibrillation in %2.8 %3.43 %3.23% Fines content in %3.48%3.85 %3.71 % Comparison between kneader and disperger at 35% consistency, pulp at room temperature and ~ 800 revolutions Kneading resulted in significant fiber shortening due to sharp edges significantly higher fibrillation and fines content

Institute for Paper, Pulp and Fiber Technology Professor Horst Cerjak, Johannes Leitner Coimbra, 9th of May 2014 Results and Interpretation Fiber Swelling and Dry Content PropertyUntreated reference Disperger 1200 rev. Disperger 2400 rev. Kneading at 45 °C; 800 rev. Kneading at 100 °C; 800 rev. WRV in g/g Dry content in % 35,9 %43%58.8%35.9 %39.5% Effect of temperature in the kneader and treatment in the disperger at 35% consistency High shear in the open disperger results in drying and hornification. Effects are related to lab construction! Increased temperature in the kneader results in less hornification

Institute for Paper, Pulp and Fiber Technology Professor Horst Cerjak, Johannes Leitner Coimbra, 9th of May 2014 Summary Kneader: Very fast increase in fiber curl Minor role of consistency Moderate decrease in WRV and dry content Same or lower SR High fiber cutting and stronger increase in fines and fibrillation Disperger: Slower increase in fiber curl; high at intensive treatment Pronounced effect of consistency Interesting results for SR, WRV and dry content Moderate fiber cutting and increase in fines and fibrillation