Wet End Control for strength optimization Roland Berger, BTG Instruments GmbH The 2 nd 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 5. Mill examples showing various control strategies 1. Fine paper 2. Liner and corrugated Medium 6. Conclusions BTG 2010 2
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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 Duroblade Best-in-class high-performance metering and doctoring blades Industry-standard, metering rods, beds and accessories In-depth, on-site application expertise Designed to provide high ROI solutions in pulping and paper production Product technology combined with application knowhow = improved productivity and surface quality BTG 2013 FCW1001/15-4
Complex Wet End BTG 2010 5
Wet End Related Production Issues Low Filler Retention Deposits White Pitch High AOX, COD Poor Drainage Low Dry Content Web breaks Web Breaks BTG 2010 6
Wet End Related Quality Issues Formation, Web Strength SCT, Burst Ash content Sizing Elastic limit Tensile Strenth Basis Weight BTG 2010 7
Origin of charge A mixture of fibers, fines and papermaking additives Fine Pigment Anionic trash Fiber Retention aid Fixative BTG 2010 8
Colloidal system Papermaking components have colloidal dimensions Ions in solution Colloidally dissolved Fine dispersed Coarse dispersed 2- SO 4 Ca 2+ Na + Lignin Polyelectrolytes CaCO 3 Fines Fibers CO 2-3 1 nm 500 nm 1 µm 100 µm 1 mm Electrokinetic effects / electrokinetic phenomena Size BTG 2010 9
Interactions in the wet end Flocculant WSA Starch Size Fixative Fixative Fixative Fixative Fiber Anionic Trash BTG 2010 10
Charge detection A window to the pulp suspension SZP-10 Fibers, fines, Particles Zeta potential (mv) PCD-04 Colloidally dissolved matter Charge demand (ml) BTG 2010 11
Why 2x charge measurements? Dissolved Charge Zeta Potential How much dissolved charge in the system? What is the charge of additives? How much fixing agent is required? What is the adsorption capacity of the fiber? Did the additive adsorb? BTG 2010 12
Optimum dosage of cationic starch Ineffective dosage + SZP: -25 mv PCD: -5 ml Strength Additive SZP: -25 mv PCD: -2 ml Effective dosage + SZP: -25 mv PCD: -1 ml Strength Additive SZP: -15 mv PCD: -1 ml BTG 2010 13
Impacts on strength properties in relation to the wet end Furnish type, TMP, Kraft, recycled, broke, fillers, etc Shear forces from pump, cleaner, screen, etc Transport media ph, conductivity, solid content, temperature, etc Residence time, chest sizes Fiber treatment Residual chemicals Fines in back water BTG 2010 14
Survey from stock prep to head box BTG 2010 15
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 amount identification and quantification of carry over impacting strength properties BTG 2010 16 16
Strength improvement Mill case I Fine paper Machine description Fine Paper machine Production 120.000 tpy 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 BTG 2010 18
Sources of anionic disturbances Optical brightener and dispersant are major reason for disturbance BTG 2007 19
Charge control in fine paper
Reduced retention aid 0 1,03-50 0,93-100 0,83 Coated broke charge -150-200 -250-300 -350 Broke charge Charge set point Ret.aid dosage average dosage retention aid 0,73 0,63 0,53 0,43 Retention aid dosage -400 0,33-450 0,23 before charge control 6 month after charge control Increased initial web strength due to controlled flocculation Reduced retention aid consumption by 60% 21 BTG 2007
Reduced web breaks 14 12 Wet breaks Average 10 number of wet breaks 8 6 4 2 0 before charge control 6 month after charge control Increased initial web strength due to controlled flocculation Web breaks reduced by 60% after charge control loop
Strength improvement Mill case II Liner & Fluting Machine description Kraft Liner and Corrugated Medium Production 200.000 tpy 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 Tensile strength Water barrier Printability, brightness (white-top) BTG 2013 EASIER, SMALLER, SMARTER, LIGHTER 24
Liner and corrugated medium production requirements Raw materials Waste papers Unbleached kraft pulp Cost / Strength properties Strength properties Refining (for some grades) to increase strength Retention to keep strength Drainage to increase productivity To decrease energy consumption BTG 2013 25
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 Energy savings - FOC BTG 2011 EASIER, SMALLER, SMARTER, LIGHTER 26
Case: refining control presented in Kadant Presentation BTG 2011 EASIER, SMALLER, SMARTER, LIGHTER 27
Case: Kadant Presentation Customer savings 190 000$ / year BTG 2011 EASIER, SMALLER, SMARTER, LIGHTER 28
Strength optimization (Solution 2) 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 BTG 2011 EASIER, SMALLER, SMARTER, LIGHTER 29
Strength optimization (Solution 3) 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 BTG 2011 EASIER, SMALLER, SMARTER, LIGHTER 30
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 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 BTG 2010 31
BTG 2010 Thank you very much for your attention! 32