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Image-based quantitative infrared analysis and microparticle characterisation for pulp and paper applications
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
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 [en]
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: urn:nbn:se:kth:diva-180722ISBN: 978-91-7595-843-9 (print)OAI: oai:DiVA.org:kth-180722DiVA: diva2:896477
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
List of papers
1. Size and shape characterization of fines and fillers: a review
Open this publication in new window or tab >>Size and shape characterization of fines and fillers: a review
2015 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, no 3, 466-487 p.Article in journal (Refereed) Published
Abstract [en]

Many properties of fines and fillers are dependent on their size and shape. This review is on the literature on size and shape characterization of fines and fillers. It takes into account measurement techniques of particle width, length, equivalent diameter, area, and shape/morphology. The advantages and limitations of different methods are discussed. Measurement of other particles properties, e.g., optical, chemical or rheological, were not included in the review. Size and shape characterization methods can be roughly divided into gravimetric and non-gravimetric methods. Gravimetric measurements methods account for all particles in the sample, but give only indicative size and shape information. Non-gravimetric methods usually give more direct size and shape information, but only account for particles larger than the resolution of the instrument. Additionally, measuring both larger and smaller particles simultaneously is rarely possible. An implication is that current analysers fail to measure a larger share of the sample, for example fibrils, which have a high impact on product properties. Of the reviewed measurement techniques, flow microscopy had the highest potential. Based on instruments found in other application areas, possible developments for flow microscopes include multiwavelength illumination and sensors, fluorescent staining, and hydrodynamic focusing.

National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-175521 (URN)000361615500012 ()2-s2.0-84951767329 (Scopus ID)
Funder
Swedish Energy Agency
Note

QC 20151020

Available from: 2015-10-20 Created: 2015-10-16 Last updated: 2017-12-01Bibliographically approved
2. Optical methods for fines and filler size characterization: Evaluation and comparison
Open this publication in new window or tab >>Optical methods for fines and filler size characterization: Evaluation and comparison
2016 (English)Report (Other academic)
Abstract [en]

The pulp fines and mineral fillers in the fine fraction of a papermaking stock influence process conditions and sheet properties. The influence is largely dependent on the size and shape of the particles. Quantitative characterization of the size and shape of fines and fillers would aid in process control and prediction of product properties.  Thus, the aim of the study was to evaluate and compare optical instruments which can be used to quantitatively characterize the fine fraction of a papermaking stock. The compared instruments were the Mastersizer2000 from Malvern, based on diffraction scattering of a laser beam, the ImageStream from Amnis, and the Fiber Tester and Fiber Tester Plus from ABB Lorentzen & Wettre. The last three instruments are all based on imaging of the particles and have spatial resolutions ranging from 0.33 µm to about 10 µm per pixel.

All instruments overestimated the size of calibration spheres with known sizes. In several cases, calibration particles that were smaller than the spatial resolution of the instrument were detected. In these cases, the relative measurement error was large, likely due to positioning and quantization errors. It is also suggested that the oversizing was partly due to dissimilar optical properties of the calibration particles, compared to the typical sample, and that better calibration materials for fines need to be developed.

For the image-based instruments, the relative share of fines and filler particles increased with as the size of the measured particles decreased. Thus, with higher spatial resolution, more particles were detected. However, the shape of the particle size distribution depended on the resolution and the field-of-view. The ImageStream resolved single PCC particles, which has not previously been done using flow microscopy. Due to its limited field-of-view, the ImageStream could not measure the largest fines, which were detected by the Fiber Tester and Fiber Tester Plus. While the Fiber Tester Plus did not resolve single PCC particles, it detected, due to its higher resolution, a higher share of smaller particles than the Fiber Tester. Overall, the ImageStream and the Fiber Tester Plus were found to be complementary.

The diffraction-based method struggled to measure small fines. It is proposed that small fines diffracted light insufficiently to be detected by the instrument. The obtained result was also highly sensitive to the choice of refractive index; a fact that some of the previous users apparently were not aware of.

In summary, image-based methods were found to perform better than the diffraction-based method when measuring on fines and mixtures of fines and fillers, while the highest resolution image-based instrument and the diffraction-based method were best when measuring on pure fillers.

Place, publisher, year, edition, pages
Stockholm: Innventia AB, 2016. 55 p.
Series
Innventia Report, 717
Keyword
Stock, fine fraction, fines, fillers, size, shape, morphology, particle size distribution, particle characterization, flow microscopy, laser diffraction, flow cytometry
National Category
Paper, Pulp and Fiber Technology Reliability and Maintenance
Research subject
Production Engineering; Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-180719 (URN)
Funder
Swedish Energy AgencyVINNOVAÖnnesjö Foundation
Note

QC 20160122

Available from: 2016-01-21 Created: 2016-01-21 Last updated: 2016-01-22Bibliographically approved
3. Characterization of morphological changes of chemical pulp fibres and fines due to refining
Open this publication in new window or tab >>Characterization of morphological changes of chemical pulp fibres and fines due to refining
(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
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:nbn:se:kth:diva-180720 (URN)
Funder
Swedish Energy AgencyVINNOVAÖnnesjö Foundation
Note

QS 2016

Available from: 2016-01-21 Created: 2016-01-21 Last updated: 2016-01-22Bibliographically approved
4. A method for measurement of the directional emittance of paper in the infrared wavelength range
Open this publication in new window or tab >>A method for measurement of the directional emittance of paper in the infrared wavelength range
2012 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 5, 958-967 p.Article in journal (Refereed) Published
Abstract [en]

A method for measuring the directional emittance of paper and board samples was developed. The available literature showed that the influence of temperature and observation angle on the emittance of dry and moist paper had not been investigated in detail. Methods adapted for such investigations were not available. In the developed method, the emittance of a sample is determined by comparing its infrared radiation with the radiation emitted from a reference surface with known emittance. In order to investigate the influence of the wavelength range, two cameras, operating in the mid-wavelength and long-wavelength infrared range, respectively, were used. The method allows for the adjustment of the directional emission angle in a range from 0° down to 80°, and variation of the sample temperature between 30°C and 100°C. A study was performed to evaluate the method. Here, the directional emittance of handsheets made from thermo-mechanical pulp was measured at different wavelength ranges, sample temperatures and emission angles. The obtained emittance values and trends were in agreement with previous experimental work and theoretical predictions. The emittance of the samples was also measured using Fourier-Transform Infrared spectroscopy. Given the methodological differences between the two measurement approaches, the results were in good agreement.

Keyword
Directional emittance, Emissivity, FTIR, Goniometer, Hemispherical emittance, Method development, Paper emittance, Thermography
National Category
Paper, Pulp and Fiber Technology Reliability and Maintenance
Research subject
SRA - Production
Identifiers
urn:nbn:se:kth:diva-105415 (URN)10.3183/NPPRJ-2012-27-05-p958-967 (DOI)000313375400017 ()2-s2.0-84871732616 (Scopus ID)
Funder
Swedish Energy AgencyXPRES - Initiative for excellence in production research
Note

QC 20130118. Updated from accepted to published.

Available from: 2012-11-21 Created: 2012-11-21 Last updated: 2017-12-07Bibliographically approved
5. Directional emittance of dry and moist paper
Open this publication in new window or tab >>Directional emittance of dry and moist paper
2014 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, no 2, 294-303 p.Article in journal (Refereed) Published
Abstract [en]

The directional emittance of dry and moist paper and board samples was measured in two wavelength ranges; the mid-wavelength infrared (MWIR) range and the long-wavelength infrared (LWIR) range. The influence of pulp type, pulp drying, pulp refining, fibre orientation, additives, coating, and observation angle on the emittance of dry paper was examined. The influence of sample moisture and observation angle on the emittance of moist samples was also investigated. The emittance in the LWIR range was higher than the MWIR emittance. The emittance varied with pulp type, especially for TMP, which had a significantly lower emittance compared to the samples made of chemical pulp. The impact of different properties, such as pulp type, refining or coating, was much smaller in the LWIR range than in the MWIR range. Observation angle was found to significantly impact the emittance at angles larger than 60 degrees from the normal direction in the MWIR range, and angles larger than 70 degrees in the LWIR range. The emittance increased with increasing moisture ratio. This increase was most pronounced at low absolute moisture ratios, where an addition of an already small amount of water could impart a large change in emittance. It was found that the emittance and sample moisture could be correlated well using a linear combination of the emittance of dry paper and pure water.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2014
Keyword
Paper, Board, Moisture, Infrared, Thermography, Emittance, Emissivity, Directional, MWIR, LWIR
National Category
Paper, Pulp and Fiber Technology
Research subject
Production Engineering; Physics; Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-141776 (URN)10.3183/NPPRJ-2014-29-02-p294-303 (DOI)000338336400014 ()2-s2.0-84901785653 (Scopus ID)
Funder
Swedish Energy Agency, 2011-0054422
Note

QC 20140225

Available from: 2014-02-21 Created: 2014-02-21 Last updated: 2017-12-05Bibliographically approved
6. Analysis of the plastic and elastic energy during the deformation and rupture of a paper sample using thermography
Open this publication in new window or tab >>Analysis of the plastic and elastic energy during the deformation and rupture of a paper sample using thermography
2012 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, 329-334 p.Article in journal (Refereed) Published
Abstract [en]

Thermography has been used to quantitatively analyze the plastic and elastic energy during deformation of paper. Sack paper samples were subjected to uniaxial tensile testing until rupture occurred. The temperature of the sample was simultaneously recorded with an infrared camera. The mechanical energy invested in the deformation was determined based on the force and deformation data. The thermal energy that accumulated in the sample during testing was estimated using the temperature measurements. Here, special attention was put on using the correct emittance values for the sack paper by measuring it with a new method. When comparing exerted mechanical energy with released thermal energy up to the time of sample rupture, about 40% to 60% of the mechanical energy could be detected as thermal energy. The lacking share of heat was most likely lost due to cooling of the sample during the experiments, as a lower share of detected mechanical energy was obtained for longer experiments. When comparing the increase in thermal energy during rupture to the elastic energy stored in the sample, an agreement of better than 90% was found.

Keyword
Elastic deformation, Emittance, Paper mechanics, Plastic deformation, Rupture work, Thermal energy, Thermography, Elastic energy, Emittances, Infra-red cameras, Mechanical energies, Paper samples, Sack paper, Uniaxial tensile testing, Deformation, Elasticity, Experiments, Temperature measurement, Tensile testing, Thermography (imaging), Thermography (temperature measurement), Paper, Experimentation, Pyrometry, Tensile Tests, Thermal Analysis
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-104882 (URN)10.3183/NPPRJ-2012-27-02-p329-334 (DOI)000315696000022 ()2-s2.0-84865201840 (Scopus ID)
Funder
XPRES - Initiative for excellence in production research
Note

QC 20121114

Available from: 2012-11-14 Created: 2012-11-14 Last updated: 2017-12-07Bibliographically approved

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