wet end control for strength optimization roland berger...
TRANSCRIPT
Wet End Control for strength optimization
Roland Berger, BTG Instruments GmbH
The 2nd International Conference
„The issues in mechanics of pulp-and-paper materials“
September 10-12
Arkhangelsk, Russia
Content
1. Introduction BTG
2. Wet End related production and quality issues
3. Impact on functional and process chemicals
4. Charge - a window to the pulp suspension
2© BTG 2010
5. Mill examples showing various control strategies
1. Fine paper
2. Liner and corrugated Medium
6. Conclusions
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© BTG 2013
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� Instruments
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Designed to
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solutions in pulping
and paper
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© BTG 2013
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production
Product technology
combined with
application know-
how = improved
productivity and
surface quality
FCW1001/15-4
Complex Wet End
5© BTG 2010
Wet End Related Production Issues
Low FillerRetention
Deposits WhitePitch
6© BTG 2010
Poor DrainageLow Dry Content
Web breaks
Web BreaksHigh AOX, COD
Wet End Related Quality Issues
Formation, Web Strength
7© BTG 2010
SCT, BurstAsh content
SizingElastic limit
Tensile StrenthBasis Weight
Origin of charge
� A mixture of fibers, fines and papermaking additives
8© BTG 2010
Pigment
Retention aid
Fiber
Anionic trash
Fixative
Fine
Colloidal system
� Papermaking components have colloidal dimensions
� Colloidally
dissolved� Fine
dispersed
� Coarse
dispersed
Lignin FibersCaCO3
� Ions in
solution
2-SO
4
9© BTG 2010
Size1 nm 1 µm 100 µm 1 mm
Lignin
PolyelectrolytesFines
FibersCaCO32+
2-
Ca
CO
Na
3
+
500 nm
Electrokinetic effects / electrokinetic phenomena
Interactions in the wet end
Flocculant
Starch
Fixative
Fixative
Fixative
10© BTG 2010
Size
WSA
Fiber
Fixative
Fixative
Anionic Trash
Charge detection
• A window to the pulp suspension
11© BTG 2010
Fibers, fines, Particles
Zeta potential (mV)Colloidally dissolved matter
Charge demand (ml)
PCD-04SZP-10
Why 2x charge measurements?
Zeta PotentialDissolved Charge
12© BTG 2010
� What is the adsorption capacityof the fiber?
� Did the additive adsorb?
� How much dissolved charge in the system?
� What is the charge of additives?� How much fixing agent is
required?
Optimum dosage of cationic starch
SZP: -25 mV PCD: -5 ml PCD: -2 mlSZP: -25 mV
Ineffective dosage
Strength Additive
+
13© BTG 2010
SZP: -25 mV PCD: -5 ml PCD: -2 mlSZP: -25 mVStrength Additive
SZP: -25 mV PCD: -1 ml PCD: -1 mlSZP: -15 mV
Effective dosage
Strength Additive
+
Impacts on strength properties in relation to the wet end
� Furnish type, TMP, Kraft, recycled, broke,
fillers, etcG
� Shear forces from pump, cleaner, screen, etc
� Transport media pH, conductivity, solid
14© BTG 2010
� Transport media pH, conductivity, solid
content, temperature, etc
� Residence time, chest sizes
� Fiber treatment
� Residual chemicals
� Fines in back water
Survey from stock prep to head box
15© BTG 2010
Wet End Survey
� Understand interaction in pulp suspension
� selection and performance assessment of fixing agents, strength additives and retention chemicals
� Selecting of the ideal addition sequence
� Selection of optimum dosage points and dosage
16© BTG 201016
� Selection of optimum dosage points and dosage amount
� identification and quantification of carry over impacting strength properties
Strength improvement Mill case I – Fine paper
Machine description
� Fine Paper machine
� Production 120.000 tpy
� Width 3.6 m� Width 3.6 m
Problem description
� High costs for retention chemicals
� High number of web breaks
� High costs due to unwanted down time
Wet End Survey revealed problem
18© BTG 2010
Sources of anionic disturbances
19© BTG 2007
� Optical brightener and dispersant are major reason for disturbance
Charge control in fine paper
Reduced retention aid
-200
-150
-100
-50
0
Coated broke charge
0,63
0,73
0,83
0,93
1,03
Retention aid dosage
Broke charge
© BTG 200721
-450
-400
-350
-300
-250
before charge control 6 month after charge control
Coated broke charge
0,23
0,33
0,43
0,53
0,63
Retention aid dosage
Charge set point
Ret.aid dosage
average dosageretention aid
� Increased initial web strength due to controlled flocculation
� Reduced retention aid consumption by 60%
Reduced web breaks
8
10
12
14
number of wet breaks
Wet breaks
Average
� Increased initial web strength due to controlled flocculation
� Web breaks reduced by 60% after charge control loop
0
2
4
6
before charge control 6 month after charge control
number of wet breaks
Strength improvement Mill case II – Liner & Fluting
Machine description
� Kraft Liner and Corrugated Medium
� Production 200.000 tpy
� Width 3.8 m� Width 3.8 m
Problem description
� Need to reduce basis weight
� Limited due to strength issues
� High costs due to unwanted down time
Liner requirements
� BW, thickness
� Burst
� SCT
� Resistance to perforation
EASIER, SMALLER, SMARTER, LIGHTER 24© BTG 2013
� Resistance to perforation
� Tensile strength
� Water barrier
� Printability, brightness (white-top)
Liner and corrugated medium production requirements
� Raw materials
� Waste papers ���� Cost / Strength properties
� Unbleached kraft pulp ���� Strength properties
� Refining (for some grades) ���� to increase strength
� Retention ���� to keep strength
� Drainage ���� to increase productivity
���� To decrease energy consumption
25© BTG 2013
Strength optimization (Solution 1)
� Refining control with DRT-5500
� Refining waste paper requires a different
strategy than kraft pulp
� Goal : increase strength with no decrease of
drainage = ideally fibrillation without fines
EASIER, SMALLER, SMARTER, LIGHTER 26© BTG 2011
drainage = ideally fibrillation without fines
� Energy savings - FOC
Case: refining control presented in Kadant Presentation
EASIER, SMALLER, SMARTER, LIGHTER 27© BTG 2011
Case: Kadant PresentationCustomer savings 190 000$ / year
EASIER, SMALLER, SMARTER, LIGHTER 28© BTG 2011
Strength optimization (Solution 2)
� Fines / ash management
� With RET-2512 and RET-5503
� To stabilize sheet homogeneity
� = to stabilize strength homogeneity
EASIER, SMALLER, SMARTER, LIGHTER 29© BTG 2011
� Fines / ash management by
� Right choice of raw materials
� Retention aid control
� Approach also valid for
porosity management
� Basis weight and thickness control
� Accurate basis weight control
� With VBW-1100
Strength optimization (Solution 3)
EASIER, SMALLER, SMARTER, LIGHTER 30© BTG 2011
� Consistency management from pulper to
headbox
� With MEK-3000, TCR-2511
� Consistency survey of stock preparation
� Proactive maintenance and calibration service of
valuable consistency control tools
Conclusions
In most paper processes, wet end chemicals are added in fixed dosages, usually optimized for a single process condition
Variations of the incoming raw materials and broke lines often not considered
31© BTG 2010
often not considered
Sustainable improvement through a solid approach with first lab measurements and later process
Quick ROI due to sustainable efficiency gain and impoved paper quality can be achieved with relatively low investment
32© BTG 2010
Thank you very much for your
attention !