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Review: Reduction of energy consumption in TMP refining through mechanical pre-treatment of wood chips
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
2010 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, no 2, p. 156-161Article, review/survey (Refereed) Published
Abstract [en]

This review covers the effect of mechanical pre-treatment of wood chips on the energy consumption in refining and the quality of pulp. To understand the mechanisms of mechanical pre-treatment, a short description of relevant refining theory and reported effects of pre-treatment on wood morphology is given. Mechanical pre-treatment offers a chance to utilize the energy needed to defibrate chips in a more efficient way, minimizing the cyclic elastic deformations which are the main defibration mechanism in refining. Studies of fibre morphology indicate that compressive pretreatment mechanically introduces favorable weak points in the S1 and S2 fibre walls where defibration proceeds easier upon subsequent refining.Published results which cover the effect of the pretreatment on energy consumption and pulp properties are reviewed. Energy reduction of between 10% and 30% is reported in the literature. High ratio of volumetric compression is necessary. Pressurized conditions are required to ensure that the fibres are not damaged during the pre-treatment. Other effects of compressive pretreatment include a more uniform chip size and moisture content, better penetration of chemicals and removal of extractives from the chips. A list of equipment used for chip pre-compression is provided together with published results of pilot-scale and mill-scale operation.

Place, publisher, year, edition, pages
2010. Vol. 25, no 2, p. 156-161
Keywords [en]
TMP refining; Chip pre-compression; Chip pre-treatment; Energy reduction; ATMP
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:miun:diva-11886DOI: 10.3183/NPPRJ-2010-25-02-p156-161ISI: 000279341100003Scopus ID: 2-s2.0-79551553499OAI: oai:DiVA.org:miun-11886DiVA, id: diva2:332031
Available from: 2010-07-30 Created: 2010-07-30 Last updated: 2017-12-12Bibliographically approved
In thesis
1. ATMP Process: Improved Energy Efficiency in TMP Refining Utilizing Selective Wood Disintegration and Targeted Application of Chemicals
Open this publication in new window or tab >>ATMP Process: Improved Energy Efficiency in TMP Refining Utilizing Selective Wood Disintegration and Targeted Application of Chemicals
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is focused on the novel wood chip refining process called AdvancedThermomechanical Pulp (ATMP) refining. ATMP consists of mechanical pretreatmentof chips in Impressafiner and Fiberizer prior to first stage refining atincreased intensity. Process chemicals (this study was concentrated on hydrogenperoxide and magnesium hydroxide) are introduced into the first stage refiner.It is known that the use of chemicals in TMP process and first stage refining atelevated intensity can reduce the energy demands of refining. The downside is thatthey also alter the character of the produced pulp. Reductions in fibre length andtear index are usually the consequences of refining at elevated intensity. Additionof chemicals usually leads to reduction of the light scattering coefficient. Usingstatistical methods it was shown that it is possible to maintain the TMP character ofthe pulp using the ATMP process. This is explained by a separation of thedefibration and the fibre development phases in refining. This separation allowsdefibration of chips to fibres and fibre bundles without addition of chemicals orincrease in refining intensity. Chemicals are applied in the fibre developmentphase only (first stage refiner). The energy demand in refining to reach tensileindex of 25 Nm/g was reduced by up to 1.1 MWh/odt (42 %) using the ATMPprocess on Loblolly pine. The energy demand in refining of White spruce, requiredto reach tensile index of 30 Nm/g, was reduced by 0.65 MWh/odt (37%).Characterizations of individual fibre properties, properties of sheets made fromlong fibre fractions and model fibre sheets with different fines fractions werecarried out. It was established that both the process equipment configuration (i.e.the mechanical pre‐treatment and the elevated refining intensity) and the additionof process chemicals in the ATMP process influence fibre properties such as external and internal fibrillation as well as the amount of split fibres. Improvementof these properties translated into improved properties of sheets, made from thelong fibre fractions of the studied pulps. The quality of the fines fraction alsoimproved. However, the mechanisms of improvement in the fines quality seem tobe different for fines, generated using improved process configuration andaddition of process chemicals. The first type of fines contributed to better bondingof model long fibre sheets through the densification of the structure. Fines whichhave been influenced by the addition of the process chemicals seemed in additionto improve bonding between long fibres by enhancing the specific bond strength.The improved fibre and fines properties also translated into better airpermeability and surface roughness of paper sheets, properties which areespecially important for supercalendered (SC) printing paper. The magnitude offibre roughening after moistening was mainly influenced by the processequipment configuration while the addition of process chemicals yielded lowestfinal surface roughness due to the lowest initial surface roughness. There was nodifference in how fines fractions from the studied processes influenced the fibreroughening. However, fines with better bonding yielded model fibre sheets withhigher PPS, probably due to their consolidation around fibre joints. Hence, thedecrease in PPS can probably be attributed to the improvements in the long fibrefraction properties while the improvement of fines quality contributed to thereduction of air permeability.The process chemicals, utilized in the ATMP process (Mg(OH)2 and H2O2) alsoproved to be an effective bleaching system. Comparable increases in brightnesscould be reached using the ATMP process and conventional tower bleaching.Maximum brightness of the pulp was reached after approximately 10 minutes ofhigh‐consistency storage after refining or 40 minutes of conventional bleaching.This study was conducted using a pilot scale refiner system operated as a batchprocess. Most of the experiments were performed using White spruce (Piceaglauca). In Paper I, Loblolly pine (Pinus taeda) was used. It is believed that theresults presented in this thesis are valid for other softwood raw materials as well,but this limitation should be considered.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2011. p. 119
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 108
Keywords
ATMP, TMP, Hydrogen Peroxide, Magnesium Hydroxide, Mechanical Pre-Treatment, Fibre Characterisation, Refiner Bleaching, SC Paper, Newsprint
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-13844 (URN)978-91-86694-34-0 (ISBN)
Public defence
2011-05-05, 10:18 (English)
Supervisors
Available from: 2011-05-27 Created: 2011-05-27 Last updated: 2012-07-30Bibliographically approved

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Gorski et al: Review: Reduction of energy consumption in TMP refining through mechanical pre-treatment of wood chips. JNPPR 2010 Vol 25 2 pp 156-161(560 kB)1434 downloads
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Gorski, DmitriEngstrand, Per

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