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High consistency hydrogen peroxide bleaching of a Norway spruce stone groundwood pulp: Influence of heat treatment and iron content
Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik. (FSCN)
2011 (Engelska)Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 26, nr 2, s. 186-196Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The objective of this work was to improve the understanding on how thermal treatments of mechanical pulps containing iron influence the unbleached brightness and hydrogen peroxide bleachability at high brightness levels. An unbleached Norway spruce stone groundwood (SGW) pulp was subjected to heat and iron (Fe3+) treatments followed by a chelating stage and a high consistency hydrogen peroxide bleaching stage. The hydrogen peroxide bleachability was studied on pulps as a function of pre-treatment at elevated temperatures and strongly bound iron content prior to bleaching and the alkali charge during bleaching. The evaluation was done using an experimental design based on the MODDE software (Umetrics AB).

Heat treatment of the unbleached SGW pulp at 110 or 140 degrees C did not induce a significant increase in light absorption coefficient. Increasing the heat treatment temperature to 170 degrees C did, however, result in an increased light absorption coefficient corresponding to a brightness loss of 3.5% ISO. The light scattering coefficient was found to be essentially unchanged regardless of the heat-treatment conditions applied. The brightness loss resulting from the heat treatment could only partly be regained by hydrogen peroxide bleaching.

An increased amount of strongly bound iron in the unbleached SGW pulp increased the light absorption coefficient. This increase was slightly higher when heat pre-treatment was performed at 140 and 170 degrees C compared to when heating at 110 degrees C. Hydrogen peroxide bleaching was found to reduce the iron content of the pulps and thus regain some of the brightness that was lost. This effect was most pronounced at the higher alkali charge levels. It is thus important to minimise the processing temperature, the time at high temperature and the iron content of the pulp in order to improve the unbleached brightness and bleachability of mechanical pulps.

Ort, förlag, år, upplaga, sidor
2011. Vol. 26, nr 2, s. 186-196
Nyckelord [en]
Mechanical pulps; Brightness; Light scattering; Light absorption; Bleaching; Hydrogen peroxide; Temperature; Iron
Nationell ämneskategori
Kemiteknik
Identifikatorer
URN: urn:nbn:se:miun:diva-12987DOI: 10.3183/NPPRJ-2011-26-02-p186-196ISI: 000291334400003Scopus ID: 2-s2.0-79958727861OAI: oai:DiVA.org:miun-12987DiVA, id: diva2:387620
Tillgänglig från: 2011-01-14 Skapad: 2011-01-14 Senast uppdaterad: 2017-12-11Bibliografiskt granskad
Ingår i avhandling
1. High consistency hydrogen peroxide bleaching of Norway spruce mechanical pulps
Öppna denna publikation i ny flik eller fönster >>High consistency hydrogen peroxide bleaching of Norway spruce mechanical pulps
2010 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Ort, förlag, år, upplaga, sidor
Sundsvall: Mittuniversitetet, 2010
Serie
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 49
Nationell ämneskategori
Kemiteknik
Identifikatorer
urn:nbn:se:miun:diva-12984 (URN)978-91-86694-07-4 (ISBN)
Handledare
Tillgänglig från: 2011-01-14 Skapad: 2011-01-14 Senast uppdaterad: 2011-01-14Bibliografiskt granskad
2. Improved hydrogene peroxide bleaching of mechanical pulps through fundamental understanding of the influence of heat, iron, fines and chemical treatment on chromophore content
Öppna denna publikation i ny flik eller fönster >>Improved hydrogene peroxide bleaching of mechanical pulps through fundamental understanding of the influence of heat, iron, fines and chemical treatment on chromophore content
2013 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Ort, förlag, år, upplaga, sidor
Sundsvall: Mid Sweden University, 2013. s. 76
Serie
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 170
Nationell ämneskategori
Kemiteknik
Identifikatorer
urn:nbn:se:miun:diva-20982 (URN)978-91-87557-16-3 (ISBN)
Handledare
Tillgänglig från: 2014-01-08 Skapad: 2014-01-08 Senast uppdaterad: 2014-01-08Bibliografiskt granskad

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