Open this publication in new window or tab >>2009 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 3, p. 266-272Article in journal (Refereed) Published
Abstract [en]
The acid hydrogen peroxide system has the potential to significantly
reduce the specific energy consumption in the production of softwood
thermomechanical pulps (TMPs). A drawback of the chemical system is
discoloration of the pulp during refining. The work presented in this
study evaluates the possibility to regain the lost brightness by
washing, chelating and sodium dithionite or hydrogen peroxide bleaching
of the treated pulps.
A washing or chelating procedure can reduce the metal ion content of
the chemically treated TMPs considerably, though brightness can be
increased by a maximum of two ISO units. The amount of iron can be
further reduced to a level similar to that of untreated pulps by
performing a reducing agent-assisted chelating stage (Q(Y)) with
dithionite. The discoloration cannot,, however, be completely
eliminated. The brightness decrease-of the treated pulps is thus not
only caused by higher iron content in the pulp, but is also dependent
on the type of iron compound and/or other coloured compounds connected
with the acid hydrogen peroxide treatment.
Oxidative bleaching with hydrogen peroxide (P) is more effective than
reductive bleaching with sodium dithionite in regaining the brightness
lost during the energy reductive treatment. By using a Q(Y) P sequence,
a hydrogen peroxide charge of 3.8% was needed to reach an ISO
brightness of 75% for the chemically treated pulps. The corresponding
hydrogen peroxide charge for the untreated TMP reference was 2.5%.
Place, publisher, year, edition, pages
Stockholm: SPCI, 2009
Keywords
TMP, Black spruce, Energy reduction, Bleaching, Hydrogen peroxide, Sodium dithionite, Brightness, Metals
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-8825 (URN)10.3183/NPPRJ-2009-24-03-p266-272 (DOI)000270862100002 ()2-s2.0-72749097945 (Scopus ID)
Projects
Mechanical Pulp Industrial Research College
2009-04-292009-04-292017-12-13Bibliographically approved