Transcript A Method to Determine Fiber Wall Damage Induced by

Institute for Paper, Pulp and Fiber Technology
Treatment of Pulp in a Kneader and Disperger
presented by Johannes Leitner
[email protected]
JohannesHorst
Leitner
Professor
Cerjak, 19.12.2005
Coimbra, 9th 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
JohannesHorst
Leitner
Professor
Cerjak, 19.12.2005
Coimbra, 9th 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
JohannesHorst
Leitner
Professor
Cerjak, 19.12.2005
0- 1200-1500 rpm
60 g
no-preheating
1-2 minutes
Coimbra, 9th 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 pH 9.1 by NaOH
• Centrifuged at 4000 rpm, for 30 minutes
JohannesHorst
Leitner
Professor
Cerjak, 19.12.2005
Coimbra, 9th 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
JohannesHorst
Leitner
Professor
Cerjak, 19.12.2005
Coimbra, 9th 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
JohannesHorst
Leitner
Professor
Cerjak, 19.12.2005
Coimbra, 9th 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
JohannesHorst
Leitner
Professor
Cerjak, 19.12.2005
Coimbra, 9th 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
JohannesHorst
Leitner
Professor
Cerjak, 19.12.2005
Coimbra, 9th 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
JohannesHorst
Leitner
Professor
Cerjak, 19.12.2005
Coimbra, 9th 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
JohannesHorst
Leitner
Professor
Cerjak, 19.12.2005
Coimbra, 9th of May 2014
10