Institute for Paper Pulp and Fiber Technology Treatment

Institute for Paper, Pulp and Fiber Technology Treatment of Pulp in a Kneader and Disperger presented by Johannes Leitner johannes. leitner@student. tugraz. at Johannes. Horst Leitner Professor Cerjak, 19. 12. 2005 Coimbra, 9 th of May 2014 1

Institute for Paper, Pulp and Fiber Technology 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 Johannes. Horst Leitner Professor Cerjak, 19. 12. 2005 Coimbra, 9 th of May 2014 2

Institute for Paper, Pulp and Fiber Technology Equipment and pre-studies • Trials performed in STSM at PMV Darmstadt, Germany Kneader Disperger • • 0 - 30 - 60 rpm Both Frequency modulated 30 g optimal Sample weight Inline preheating Preparations 7, 5 – 60 minutes treatment time Johannes. Horst Leitner Professor Cerjak, 19. 12. 2005 0 - 1200 -1500 rpm 60 g no-preheating 1 -2 minutes Coimbra, 9 th of May 2014 3

Institute for Paper, Pulp and Fiber Technology 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 p. H 9. 1 by Na. OH • Centrifuged at 4000 rpm, for 30 minutes Johannes. Horst Leitner Professor Cerjak, 19. 12. 2005 Coimbra, 9 th of May 2014 4

Institute for Paper, Pulp and Fiber Technology 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 Johannes. Horst Leitner Professor Cerjak, 19. 12. 2005 Coimbra, 9 th of May 2014 5

Institute for Paper, Pulp and Fiber Technology Results and Interpretation SR & Curl in the disperger Kneader Disperger Disintegrated pulp in a kneader (left) and disperger (right) • Disperger: Long intensive treatment results in inacceptable nodular structure of pulp even after 30 000 revolutions in the disintegrator Johannes. Horst Leitner Professor Cerjak, 19. 12. 2005 Coimbra, 9 th of May 2014 6

Institute for Paper, Pulp and Fiber Technology 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 Johannes. Horst Leitner Professor Cerjak, 19. 12. 2005 Coimbra, 9 th of May 2014 7

Institute for Paper, Pulp and Fiber Technology Results and Interpretation Fiber length, Fibrillation and Fines Comparison between kneader and disperger at 35% consistency , pulp at room temperature and ~ 800 revolutions Fiber property No treatment Kneader Disperger Lw Fiber Length [mm] 2. 57 mm 2. 2 mm 2. 46 mm Fibrillation in % 2. 8 % 3. 43 % 3. 23% Fines content in % 3. 48% 3. 85 % 3. 71 % • Kneading resulted in • significant fiber shortening due to sharp edges • significantly higher fibrillation and fines content Johannes. Horst Leitner Professor Cerjak, 19. 12. 2005 Coimbra, 9 th of May 2014 8

Institute for Paper, Pulp and Fiber Technology Results and Interpretation Fiber Swelling and Dry Content Effect of temperature in the kneader and treatment in the disperger at 35% consistency Property Untreated reference Disperger 1200 rev. Disperger 2400 rev. Kneading at 45 °C; 800 rev. Kneading at 100 °C; 800 rev. WRV in g/g 1. 35 1. 20 0. 95 1. 21 1. 09 43% 58. 8% 35. 9 % 39. 5% Dry content 35, 9 % in % • 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 Johannes. Horst Leitner Professor Cerjak, 19. 12. 2005 Coimbra, 9 th of May 2014 9

Institute for Paper, Pulp and Fiber Technology Summary 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 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 Johannes. Horst Leitner Professor Cerjak, 19. 12. 2005 Coimbra, 9 th of May 2014 10