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Chemitermomechanical pulp made from birch at high temperature
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. (FSCN – Fibre Science and Communication Network)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
2006 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, no 2, 216-221 p.Article in journal (Refereed) Published
Abstract [en]

The inherent stiffness of birch wood-fibres makes birch an excellent raw material in the manufacture of high bulk pulp. By a combination of chemical impregnation of birch chips and pre-heating of the chips to high temperature prior to refining, it is possible to manufacture CTMP with very high bulk using a low energy input. Trials revealed that the high pre-heating temperature lowers the energy consumption considerably. At 500 ml CSF an increase in the pre-heating temperature from 110C to 160C reduced the energy consumption by more than 40 %. Despite the low energy input, the shive content remained low or was even reduced and the internal bond strength, in terms of Scott-Bond, compared favourably with Spruce CTMP. In summary, a high pre-heating temperature can be used to manufacture birch CTMP with very high bulk, at a low energy consumption.

Place, publisher, year, edition, pages
2006. Vol. 21, no 2, 216-221 p.
Keyword [en]
CTMP, birch, pre-treatment. pre-heating, energy consumption, paperboard, bulk, shive content.
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:miun:diva-3757DOI: 10.3183/NPPRJ-2006-21-02-p216-221ISI: 000238726200008Scopus ID: 2-s2.0-33745726932Local ID: 4038OAI: oai:DiVA.org:miun-3757DiVA: diva2:28789
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2016-09-29Bibliographically approved
In thesis
1. High temperature CTMP from birch
Open this publication in new window or tab >>High temperature CTMP from birch
2006 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is intended to contribute to understanding of the chemithermomechanical pulping of birch intended for high freeness grades. It focuses on the effects that conditions during pre‐treatment, i.e. the chemical addition of sodium sulphite and sodium hydroxide and the temperature in pre‐heater, have on the energy consumption and process runnability in terms of disc clearance. Pulp properties are evaluated in regard to brightness and the relation between bulk and internal bond strength. Pilot trials showed that pre‐heating birch chips to high temperature prior to refining (HT CTMP > 140°C), facilitated defibration and considerably lowered energy consumption. This made it possible to produce pulp with very high freeness. Despite the low energy input at high pre‐heating temperature, shive content remained low or was even reduced in the high freeness range. Mill trials confirmed the positive effect of a high pre‐heating temperature on energy consumption and on pulp properties. Furthermore it was shown that the internal bond strength in sheets from birch CTMP, in terms of Scott‐Bond at a given bulk, compared well with that of Spruce CTMP. Moreover, the shive content of birch CTMP produced using the high temperature technique was lower than that of spruce CTMP at a given bulk. A new laboratory technique ʹthe shavings methodology was used in combination with multivariate data analysis to investigate the effect of various pre‐treatments on native wood brightness. This method looks directly on the changes in brightness of the green wood as such. It revealed that the brightness of green birch wood is sensitive to increases in relative humidity and temperature. It also indicated that using a relatively high pre‐heating temperature (~140–155°C) when manufacturing birch CTMP is not necessarily detrimental to pulp brightness, provided the chemical charge is properly adjusted. However, at very high temperature (>160°C), the time in the pre‐heater should be kept short. Measurement of frictional behaviour, at simulated CTMP conditions, showed that the coefficient of friction of birch was greatly affected by chemical modification. Thus extraction raised the coefficient of friction. This rise can probably be attributed to reduced lubrication by the extractive substances and to the higher moisture content in the extracted samples. Sulphonation of the birch samples with 3 % Na2SO3 and 2 % NaOH (pH 13.5) gave a local maximum around 140–155°C. The local peak may be correlated with the reduction in energy consumption when the pre‐heating temperature is increased in the production of birch CTMP. Birch wood and spruce wood are also shown to have distinct differences in frictional performance. The coefficient of friction between birch and steel is higher than that between spruce and steel. The high stiffness and density of the birch wood and differences in the amount and composition of birch and spruce extractive substances probably account for the observed variations.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2006
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 11
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-9109 (URN)91-85317-20-9 (ISBN)
Presentation
2006-05-10, Sundsvall, 00:00 (Swedish)
Opponent
Available from: 2009-06-08 Created: 2009-06-08 Last updated: 2009-07-13Bibliographically approved

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Vesterlind, Eva-LottaHöglund, Hans
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