Wet End Control for strength optimization Roland Berger...

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

BTG is part of a financially strong parent: Spectris plc

Beta LaserMike

Brüel & Kjær Vibro

In-line instrumentationTest and measurement

HBM

Brüel & Kjær S & V

Materials analysis

Malvern

PANalytical

Spectris plc

Industrial controls

Microscan

Red Lion Controls

© BTG 2013

Each unit serves its own distinct customer base

� $1billion public company� Made up of 13 companies� Focused on improving productivity of industrial

processes

Brüel & Kjær Vibro

BTG

NDC Infrared Engineering

Servomex

HBM

Particle Measuring Systems

PANalytical Red Lion Controls

OmegaEngineering

FCW1001/15-3

Our value proposition

� Instruments

� Broad and unique portfolio of consistency transmitters

� Broad portfolio of In-line analyzers

� Industry-leading laboratory instruments

� In-depth, on-site application expertise

Designed to

provide high ROI

solutions in pulping

and paper

production

© BTG 2013


� Duroblade

� Best-in-class high-performance meteringand doctoring blades

� Industry-standard, metering rods, beds and accessories


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


drainage = ideally fibrillation without fines

� Energy savings - FOC

Case: refining control presented in Kadant Presentation


Case: Kadant PresentationCustomer savings 190 000$ / year



� Fines / ash management

� With RET-2512 and RET-5503

� To stabilize sheet homogeneity

� = to stabilize strength homogeneity


� 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



� 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

Wet End Control for strength optimization Roland Berger...

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