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Characterization of morphological changes of chemical pulp fibres and fines due to refining
KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics. Innventia, Sweden. (Manufacturing and Metrology Systems)ORCID iD: 0000-0002-1467-7413
Mid Sweden University; Innventia.
Innventia, Sweden.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The influence of the refining process on the morphological changes of a chemical softwood pulp was investigated. An industrial-like laboratory refiner was used, where the pulp was refined with five refining segments with differences in bar widths, groove widths, and cutting angles. The refined pulp was characterized with a fibre analyser with a spatial resolution of approximately 4 µm/pixel and a wide size range. The fines fraction of the refined pulp was also characterized with an imaging flow cytometer with a spatial resolution of 0.33 µm/pixel and a narrower size range.

The fibre analyser measurements showed that the mean length, width, and aspect ratio of the fines decreased monotonically with accumulated refining energy. The imaging flow cytometer with its higher spatial resolution showed little change in fines morphology with accumulated refining energy.

The morphology of the fines was more dependent on the applied specific refining energy than the design of the refining segment. However, a segment with much finer grooves and bars, initially designed for hardwood, gave significantly less fibre shortening, fines generation, external fibrillation, kink, and fines that were more fibrillar, compared to the other segments. 

Keyword [en]
Chemical pulp, morphology, stock characterization, refining, fines, fibrillation
National Category
Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science; Production Engineering
Identifiers
URN: urn:nbn:se:kth:diva-180720OAI: oai:DiVA.org:kth-180720DiVA: diva2:896452
Funder
Swedish Energy AgencyVINNOVAÖnnesjö Foundation
Note

QS 2016

Available from: 2016-01-21 Created: 2016-01-21 Last updated: 2016-01-22Bibliographically approved
In thesis
1. Image-based quantitative infrared analysis and microparticle characterisation for pulp and paper applications
Open this publication in new window or tab >>Image-based quantitative infrared analysis and microparticle characterisation for pulp and paper applications
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Measurements of process variations and particle morphology are widely employed in the pulp and paper industry. Two techniques with high potential, infrared thermography and microparticle characterisation, are mainly used qualitatively. Quantitative thermography requires knowledge of the emittance, a material property which has not been measured under many process-relevant conditions. Quantitative characterisation of microparticles, e.g. pulp fines and mineral fillers, requires the analysis of a large number of particles, which can be accomplished using flow microscopes. Flow microscopes for pulp analysis have had insufficient spatial resolution to resolve fines and fillers. Additionally, there has been a lack of methods which can differentiate between fines and fillers in a mixed suspension.

State-of-the-art instruments for particle image analysis were evaluated and compared to laser diffractometry, a measurement method based on scattering by diffraction. Laser diffractometry was found to be highly sensitive to the complex refractive index of the particles, and especially to its change due to moisture absorption. A high-resolution imaging flow cytometer and a high-resolution fibre analyser were found to be complementary for characterisation of pure fines and fines/filler mixtures, and superior to laser diffractometry. A method for differentiating between fines and fillers in a suspension based on their autofluorescence and side-scattering was proposed and qualitatively evaluated.

Furthermore, a method for measuring the directional and integrated emittance of paper was developed and its accuracy was determined. Measurements on a wide range of samples showed that the emittance of fibre-based materials vary significantly with wavelength, pulp type, observation angle, and moisture content. By applying measured quantitative values of the emittance, the thermal energy emitted by sack paper samples during mechanical deformation could be quantitatively calculated. The increase in thermal energy at the time of rupture was found to correlate well with the elastic share of the mechanical energy that was stored in the sample during its elongation.

In summary, the results of this work have facilitated the use of quantitative microparticle analysis and infrared thermography for pulp and paper applications. 

Abstract [sv]

Mätningar av processvariationer och partiklars form och storlek utförs i stor skala inom massa- och pappersindustrin. Två mättekniker med stor potential, infraröd termografi och mikropartikel-karaktärisering, används mest kvalitativt idag. Kvantitativ termografi kräver att provets emittans är känd. Emittansen är en materialegenskap som inte har mätts för många förhållanden som är relevanta inom papperstillverkning. Kvantitativ karaktärisering av partiklar kräver att ett tillräckligt stort antal partiklar analyseras, något som kan göras med flödesmikroskop. Flödesmikroskop för mäldanalys har haft otillräcklig upplösning för att karaktärisera mikrometerstora partiklar, t.ex. fines och fyllmedel. Det har heller inte funnits någon metod som kan särskilja mellan fines och fyllmedel i en blandning.

Högupplösta mätinstrument för bildbaserad mikropartikelkaraktärisering utvärderades och jämfördes med en laserdiffraktometer, en mätmetod baserad på ljusspridning genom diffraktion. Laserdiffraktometerns mätresultat påverkades starkt av det brytningsindex som antogs för provet, och hur brytningsindexet ändrades med fukthalt. En högupplöst bildbaserad flödescytometer och en högupplöst fibermätare konstaterades komplettera varandra vid mätningar av mäldens finmaterial. De var även pålitligare än laserdiffraktometern vid mätningar av organiskt finmaterial. En metod för att skilja mellan organiskt och oorganiskt finmaterial i en mäld baserat på deras autofluorescens och ljusspridning presenterades och utvärderades kvalitativt.

En metod för att mäta den vinkelberoende och våglängdsintegrerade emittansen hos fiberbaserade material utvecklades och dess mätnoggrannhet utvärderades. Mätningar på ett stort antal prover visade att emittansen varierade betydligt med våglängd, mäldtyp, observationsvinkel, och fukthalt. Genom att använda den uppmätta emittansen kunde den termiska energin som frigjordes av ett säckpappersprov vid brottögonblicket beräknas. Denna energi korrelerade väl med den elastiska energi som lagrades i provet medan det töjdes, fram till tidpunkten för brottet.

Sammanfattningsvis har resultaten av detta arbete möjliggjort kvantitativ användning av mikropartikel-karaktärisering och infraröd termografi i massa- och papperstillämpningar.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 132 p.
Series
TRITA-IIP, ISSN 1650-1888 ; 16:01
Keyword
Metrology, stock, papermaking, refining, fibrillation, fines, filler, morphology, classification, flow microscopy, fibre analyser, flow cytometry, laser diffraction, dynamic image analysis, process variation, thermography, emittance, emissivity, infrared, MWIR, LWIR, goniometer
National Category
Reliability and Maintenance Paper, Pulp and Fiber Technology
Research subject
Production Engineering; Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-180722 (URN)978-91-7595-843-9 (ISBN)
Public defence
2016-02-12, Innoversum, Innventia, Drottning Kristinas Väg 61, Solna, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Energy AgencyÖnnesjö Foundation
Note

QC 20160122

Available from: 2016-01-22 Created: 2016-01-21 Last updated: 2016-01-22Bibliographically approved

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