Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Method for fractionating an aqueous paper fibre suspension and hydrocyclone for carrying out said method
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
Show others and affiliations
2008 (English)Patent (Other (popular science, discussion, etc.))
Abstract [en]

The invention relates to a method and to a device which is used to fraction aqueous paper fibre suspensions (S). Relatively large centrifugal forces are used, also in suspension components having essentially the same densities, in order to achieve good results. This is achieved by virtue of the fact that the paper fibre suspension (S) entering via the inlet (10) is guided initially in a first annular chamber (4) which narrows in an axial direction (4) and subsequently in a second annular chamber (5) which widens in an axial direction. As a result, good fractionating results can be obtained, in particular, when the fibre material consistency in the inlet area is approximately 0.5 - 2 % and also the necessary mass fluxes are maintained at a relatively low level. Said method can be used, for example, for fractionating fresh cellulose and/or wood pulp. It can also be used in the preparation of used paper, wherein said method is particularly economical.

Place, publisher, year, edition, pages
2008.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-6379OAI: oai:DiVA.org:kth-6379DiVA: diva2:11073
Patent
EP 1799903B1 (2008-12-03)
Note

QC 20170615

Expired

Available from: 2006-11-22 Created: 2006-11-22 Last updated: 2017-06-15Bibliographically approved
In thesis
1. Flow Field and Fibre Fractionation Studies in Hydrocyclones
Open this publication in new window or tab >>Flow Field and Fibre Fractionation Studies in Hydrocyclones
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Hydrocyclones can be used to fractionate fibres according to their papermaking potential. The obtained fractions typically differ in fibre wall thickness and/or degree of fibre treatment. Despite a multitude of potential application scenarios, the process has so far had little commercial success. This is largely explained by the low fractionation efficiency and unfavourable operating characteristics of the process.

The fractionation efficiency of a hydrocyclone is closely related to its flow field. The influence of pulp concentration on the tangential velocity field was therefore studied, by using a self-cleaning pitometer. It was found that the pulp concentration had a strong influence on the tangential velocity. At a feed pulp concentration above 7.5 g/l, the suspension rotated almost as a solid body. As a consequence, the magnitude of radial acceleration and shear stresses decreased dramatically. It is suggested that this is detrimental to the fractionation efficiency.

The radial velocity field was measured using an Ultrasonic Velocity Profiler. The measurements showed that the rotational centre of the flow field did not correspond with the geometrical centre of the hydrocyclone. This displacement caused the tangential velocity component of the vortex to contribute substantially to the measurement result of the radial velocity component.

Based on the findings in respect to the flow field studies, a novel design for a fibre fractionation hydrocyclone was proposed. The flow field inside this hydrocyclone was compared to that in a conventional hydrocyclone. It was found, that high radial acceleration and shear stresses could be maintained in the novel design even at high fibre concentration. The fractionation efficiency of the novel hydrocyclone was characterised in terms of surface roughness difference between fine and coarse fraction. When operated with refined bleached softwood kraft pulp, the novel hydrocyclone could produce fractions with a substantial surface roughness difference without deteriorating the dewatering characteristics of the fine fraction. A low thickening of the reject is proposed to be the explanation for that. When fractionating TMP, the best efficiency occurred at a concentration of 10 g/l.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2006:40
Keyword
Fibre suspension, fractionation, hydrocyclone, measurement technique, velocity measurement, shear forces
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-4175 (URN)
Public defence
2006-12-01, STFI-salen, STFI-Packforsk, Drottning Kristinas väg 61, Stockholm, 10:10
Opponent
Supervisors
Note
QC 20100804Available from: 2006-11-22 Created: 2006-11-22 Last updated: 2010-08-04Bibliographically approved

Open Access in DiVA

No full text

Other links

Espacenet

Search in DiVA

By author/editor
Norman, BoBergström, JonasVomhoff, Hannes
By organisation
Fibre and Polymer Technology
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 44 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf