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The Interrelation of Pulp Fiber Morphology, Flocculation and Network Strength

The Interrelation of Pulp Fiber Morphology, Flocculation and Network Strength . R. Eckhart, W. Bauer Institute for Paper, Pulp and Fiber Technology Graz University of Technology. Outline. Introduction Measurement of Flocculation Measurement of Network Strength Exemplary Result Conclusion.

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The Interrelation of Pulp Fiber Morphology, Flocculation and Network Strength

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  1. The Interrelation of Pulp Fiber Morphology, Flocculation and Network Strength R. Eckhart, W. Bauer Institute for Paper, Pulp and Fiber Technology Graz University of Technology

  2. Outline • Introduction • Measurement of Flocculation • Measurement of Network Strength • Exemplary Result • Conclusion

  3. Outline • Introduction • Measurement ofFlocculation • Measurement of Network Strength • ExemplaryResult • Conclusion

  4. Introduction Fiber Flocculation Fiber Morphology „CrowdingNumber“ MechanicalInterlocking Fiber Length Fiber Curl Flexibility Fibrillation Coarseness . . . „CrowdingNumber“ MechanicalInterlocking Network Strength

  5. Outline • Introduction • Measurement ofFlocculation • Measurement of Network Strength • ExemplaryResult • Conclusion

  6. Measurement of Flocculation camera observation channel light source dosage of chemicals chest centrifugal pump

  7. Measurement of Flocculation • Flow Velocity • 2-3 m/s • Channel-geometry: • length: 100 cm • width: 3.5 cm • height: 1.6 cm Turbulence at the beginning of the channel 4 mm 16 mm

  8. Measurement of Flocculation

  9. Measurement of Flocculation FFT Structure Analysis Intensity of structures 4 mm 3 cm Size of structures

  10. Outline • Introduction • Measurement ofFlocculation • Measurement of Network Strength • ExemplaryResult • Conclusion

  11. Measurement of Network Strength

  12. Measurement of Network Strength • Gap: 3 mm • Consistency: 0,4 % • wall effects will have at • least some impact on • the results

  13. Measurement of Network Strength • Critical concentratiion for floc formation: • c… concentration • r… length to width ratio • nf… number of fibers within the volume swept out by an average rotating fiber Continous network starting at => c ~ 0.1%

  14. Measurement of Network Strength • Forces at fiber to fiber contact (literature review): • Colloidal Forces • Mechanical Interlocking (Kinks, Curl, strong fibrillation) • Forces due to elastic deformation of fibers • (surface friction) • Surface tension (eventually trapped air within the network) Increasing conc. Starting at 0.3% Flocculation- Formation Micro-flocculation - Retention

  15. Measurement of Network Strength • About 30g of suspension • Measurement parameters • Amplitude 5% (the upper limit mentioned in the literature) • Frequency-sweep; 10 Measurement steps, 100 – 1 [1/s] • 3 independent measurements, results are averaged

  16. Measurement of Network Strength • Storage modulus: • c… concentration • k… constant representing fiber properties • α… constant representing network properties k… fiber length distribution, fiber wall thickness, fiber flexibility, fibrillation (surface friction) α … for 3-dimensional networks about 3 => storage modulus is dependent on c and k

  17. Outline • Introduction • Measurement ofFlocculation • Measurement of Network Strength • ExemplaryResult • Conclusion

  18. Network Strength – Floculation Behaviour • Pulp Samples: • Softwood pulp flash dried • Softwood pulp Valleybeater 50‘ • Eucalypt Pulp • Mixtures • Softwood unrefined– Eucalypt Pulp • 75-25, 50-50, 25-75 • Softwood Valleybeater 50‘ - Eucalypt Pulp • 75-25, 50-50, 25-75

  19. Network Strength – Floculation Behaviour • Morphological Parameters: • Fiber Length • Fiber Curl • Flexibility • Fibrillation

  20. Network Strength – Floculation Behaviour

  21. Network Strength – Floculation Behaviour

  22. Network Strength – Floculation Behaviour

  23. Outline • Introduction • Measurement ofFlocculation • Measurement of Network Strength • ExemplaryResult • Conclusion

  24. Conclusion • Flocculation Behaviour and Network Strength show a • linear corellation depending on fiber parameters • like fiber flexibility, fiber length, fiber curl and maybe • fibrillation… • Floc size distribution and shear stability (network • strength) together might be capable of a description of • formation behaviour of a certain pulp mixture

  25. Thank you for your Attention!!

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