Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • 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
Low consistency refining of mechanical pulp: process conditions and energy efficiency
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The thesis is focussed on low consistency (LC) refining of mechanical pulp. Theresearch included evaluations of energy efficiency, development of pulpproperties, the influence of fibre concentration on LC refining and effects of rotorposition in a two-zoned LC refiner.

Trials were made in mill scale in a modern TMP line equipped with an MSDImpressafiner for chip pre-treatment, double disc (DD) first stage refining and aprototype 72-inch TwinFlo LC refiner in the second stage. Tensile index increasedby 8 Nm/g and fibre length was reduced by 10 % in LC refining at 140 kWh/adtgross specific refining energy and specific edge load 1.0 J/m. Specific lightscattering coefficient did not develop significantly over the LC refiner.

The above mentioned TMP line was compared with a two stage single disc highconsistency Twin 60 refiner line. The purpose was to evaluate specific energyconsumption and pulp properties. The two different process solutions were testedin mill scale, running similar Norway spruce wood supply. At the same tensileindex and freeness, the specific energy consumption was 400 kWh/adt lower in theDD-LC concept compared with the SD-SD system. Pulp characteristics of the tworefining concepts were compared at tensile index 47 Nm/g. Fibre length was lowerafter DD-LC refining than after SD-SD refining. Specific light scattering coefficientwas higher and shive content much lower for DD-LC pulp.

The effects of sulphite chip pre-treatment on second stage LC refining were alsoevaluated. No apparent differences in fibre properties after LC refining werenoticed between treated and untreated pulps. Sulphite chip pre-treatment iniiicombination with LC refining in second stage, yielded a pulp without screeningand reject refining with tensile index and shives content that were similar to nonpre-treated final pulp after screening and reject refining.

A pilot scale study was performed to investigate the influence of fibreconcentration on pulp properties in LC refining of mechanical pulps. MarketCTMP was utilised in all trials and fibre concentrations were controlled by meansof adjustments of the pulp consistency and by screen fractionation of the pulp. Inaddition, various refiner parameters were studied, such as no-load, gap and baredge length. Pulp with the highest fibre concentration supported a larger refinergap than pulp with low fibre concentration at a given gross power input. Fibreshortening was lower and tensile index increase was higher for long fibre enrichedpulp. The results from this study support the interesting concept of combiningmain line LC refining and screening, where screen reject is recycled to the LCrefiner inlet.

It has been observed that the rotor in two-zoned refiners is not always centred,even though pulp flow rate is equal in both refining zones. This leads to unequalplate gaps, which renders unevenly refined pulp. Trials were performed in millscale, using the 72-inch TwinFlo, to investigate differences in pulp properties androtor positions by means of altering the pressure difference between the refiningzones. In order to produce homogenous pulp, it was found that uneven plate gapscan be compensated for in LC refiners with dual refining zones. Results from thedifferent flow rate adjustments indicated that the control setting with similar plategap gave the most homogenous pulp.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2011. , 53 p.
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 70
Keyword [en]
Mechanical pulping, low consistency refining, energy efficiency, rotor position, plate gap, fibre concentration
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:miun:diva-15406ISBN: 978-91-86694-60-9 (print)OAI: oai:DiVA.org:miun-15406DiVA: diva2:467482
Supervisors
Available from: 2011-12-19 Created: 2011-12-19 Last updated: 2012-08-01Bibliographically approved
List of papers
1. Comparison of mechanical pulps from two stage HC single disc and HC double disc - LC refining
Open this publication in new window or tab >>Comparison of mechanical pulps from two stage HC single disc and HC double disc - LC refining
2012 (English)In: Appita journal, ISSN 1038-6807, Vol. 65, no 1, 57-62 p.Article in journal (Refereed) Published
Abstract [en]

A mechanical pulping line consisting of high consistency (HC) double disc (DD) and low consistency (LC) refining was compared with a two stage single disc (SD) high consistency twin refiner line. The purpose of this study was to evaluate specific energy consumption and pulp properties. The two different process solutions were tested running similar Norway spruce wood supply. At similar tensile index and freeness, the DD-LC concept reduced the electric energy consumption by 400 kWh/adt compared with the traditional two-stage SD-SD system. Pulp characteristics of the two refining concepts were compared at tensile index 47 Nm/g. Fibre length was reduced more after DD-LC refining than after SD-SD refining. Specific light scattering coefficient was higher after DD-LC refining than SD-SD refining, while the development in second stage refining was better for SD-SD pulp than for DD-LC pulp. Shive level was significantly lower for DD-LC pulp than for SD-SD pulp.

Keyword
mechanical pulp; TMP; low consistency; high consistency; refining; energy; efficiency; double disc; single disc
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-15381 (URN)000299854800016 ()2-s2.0-84865203787 (Scopus ID)
Available from: 2011-12-19 Created: 2011-12-19 Last updated: 2017-12-08Bibliographically approved
2. Effect of fibre length distribution on low consistency refining of mechanical pulp
Open this publication in new window or tab >>Effect of fibre length distribution on low consistency refining of mechanical pulp
(English)Manuscript (preprint) (Other academic)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-15403 (URN)
Available from: 2011-12-19 Created: 2011-12-19 Last updated: 2016-12-09Bibliographically approved
3. The effect of rotor position on pulp properties in a two-zoned low consistency refiner
Open this publication in new window or tab >>The effect of rotor position on pulp properties in a two-zoned low consistency refiner
2012 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 3, 525-530 p.Article in journal (Refereed) Published
Abstract [en]

Earlier studies have shown that plate gaps are sometimes unequal in two-zoned low consistency refiners and that unequal gaps render unevenly refined pulp. It is also known that optimisation of plate gap in low consistency refining leads to improved energy efficiency. In this work, trials were made in mill scale in a modern TMP line equipped with a prototype 72 inch TwinFlo low consistency refiner in second stage. The study was designed to investigate the development of pulp properties from different rotor positions by means of altering the outlet flow rate ratio. The specific energy consumption was calculated for each refining zone and setting, based on flow rate and temperature increase. In order to produce homogenous pulp, it was found that uneven plate gaps need to be compensated in low consistency refiners with dual refining zones. Results from the different flow rate adjustments indicated that the control setting with similar plate gap gave the most homogenous pulp. However, further studies are needed to find an adequate rotor control strategy. The temperature increase in each refining zone seems to correlate well with the applied specific energy consumption in each refining zone.

National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-15405 (URN)10.3183/NPPRJ-2012-27-03-p525-530 (DOI)000311020100002 ()2-s2.0-84865238569 (Scopus ID)
Note

I Stefan Anderssons Licentiatavhandling ingår den inskickade versionen av artikeln

Available from: 2011-12-19 Created: 2011-12-19 Last updated: 2017-12-08Bibliographically approved

Open Access in DiVA

Lic Stefan Andersson(1314 kB)1701 downloads
File information
File name FULLTEXT01.pdfFile size 1314 kBChecksum SHA-512
c28234022b73ea4630954cb0450ce99401b952570fbf5c3de11735d80c04d5b6272dbda4e21a893cdc6d24a7b2154f7734f7486c82b2bdceeccea3f18e8caca4
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Andersson, Stefan
By organisation
Department of Natural Sciences, Engineering and Mathematics
Paper, Pulp and Fiber Technology

Search outside of DiVA

GoogleGoogle Scholar
Total: 1701 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 2192 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • 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