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Nordic Pulp & Paper Research Journal

The international research journal on sustainable utilization of forest bioresources

Editor-in-Chief: Lindström, Tom

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Volume 34, Issue 2


Length-based hydrodynamic fractionation of highly networked fibers in a mini-channel

Thomas Schmid
  • Corresponding author
  • Institute of Process and Particle Engineering (IPPT), Graz University of Technology, Inffeldgasse 13/III, 8010 Graz, Austria
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/ Jakob D. Redlinger-Pohn
  • Institute of Process and Particle Engineering (IPPT), Graz University of Technology, Inffeldgasse 13/III, 8010 Graz, Austria
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/ Stefan Radl
  • Institute of Process and Particle Engineering (IPPT), Graz University of Technology, Inffeldgasse 13/III, 8010 Graz, Austria
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Published Online: 2019-03-23 | DOI: https://doi.org/10.1515/npprj-2018-0086


Fractionation of cellulose fibers is performed within a circular mini-channel (diameter 7 mm) to realize a novel fractionation principle. We show that fractionation within a single-floc regime relies on the formation of a rigid network in cases where the crowding number is chosen to be greater than 60. Fractionation is performed for channel Reynolds numbers Re> 10,000, and unlike the situation in larger channels, fractionation is found to be relatively independent of Re. Experiments show a high dependency of the radial aperture velocity and aperture width on fractionation performance associated with fibers that are longer than 200 µm. By contrast, fibers shorter than 200 µm are only influenced by the volumetric flow rate through the aperture. Our results suggest that fibers smaller than 200 µm are mobile in the near wall region. Fibers longer than 200 µm are, dependent on their length, drawn out of the network by hydrodynamic forces acting on them as a result of the radial fluid velocity caused by the accept flow through the aperture. Our results support a novel fractionation hypothesis that is in contrast to previous findings, which were based on dilute flows and were demonstrated in channels having a larger size.

Keywords: fiber network; fibers; grade efficiency; hydrodynamic fractionation; mini-channel


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About the article

Received: 2018-12-17

Accepted: 2019-03-03

Published Online: 2019-03-23

Published in Print: 2019-05-26

The authors gratefully acknowledge the industrial partners Sappi Austria Produktions-GmbH & Co KG, Zellstoff Pöls AG and Mondi Frantschach GmbH, and the Competence Centers for Excellent Technologies (COMET), promoted by BMVIT, BMDW, Styria and Carinthia and managed by FFG, for their financial support of the K-project FLIPPR² (Future Lignin and Pulp Processing Research – PROCESS INTEGRATION).

Conflict of interest: The authors declare no conflicts of interest.

Citation Information: Nordic Pulp & Paper Research Journal, Volume 34, Issue 2, Pages 182–199, ISSN (Online) 2000-0669, ISSN (Print) 0283-2631, DOI: https://doi.org/10.1515/npprj-2018-0086.

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