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Improvement of energy efficiency in TMP refining by selective wood disintegration and targeted application of chemicals
Paper & Fibre Res Inst PFI, NO-7491 Trondheim, Norway.
QualTech AB, SE-28221 Tyringe, Sweden.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
Norske Skog Saugbrugs, NO-1756 Halden, Norway.
2011 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 26, no 1, 31-46 p.Article in journal (Refereed) Published
Abstract [en]

A pilot refining trial on Loblolly pine (Pinus taeda) was conducted using a novel process configuration called ATMP (Advanced Thermomechanical Pulp). In this process, selective wood disintegration due to mechanical pre-treatment of chips and increased refining intensity is combined with targeted application of chemicals after defibration. Standard TMP was compared to ATMP where different chemical strategies were applied. These strategies employed active chemicals known to cause sulphonation, carboxylation/oxidation and degradation of fibre components in order to assist the refining process. Main goal of the study was to evaluate the potential of decreasing the energy demand in refining evaluated at equal tensile index compared to a TMP reference. Another goal was to produce pulp where the TMP character, i.e. good optical properties combined with good bulk and strength properties, was fully preserved. The objective was also to study other quality aspects of the pulp produced using the ATMP process and compare these to properties of conventional TMP. Energy demand in refining was decreased with at least 0.6 MWh/odt compared to TMP at tensile index 25 Nm/g when ATMP concept was used. Maximum achieved reduction in the refining energy demand was 1.1 MWh/odt (42%) compared to the TMP reference at tensile index 25 Nm/g. Statistical analysis showed that pulp, produced using the ATMP process, retained all its important properties such as light scattering, density and elongation on the same level as control TMP, i.e. it had the same character. All pulps produced using the ATMP process had very low shive content. Treatment with hydrogen peroxide and magnesium hydroxide was the most successful chemical strategy tested during the pilot trial. It was most successful both in respect to improved optical properties (14 ISO % increase in brightness could be achieved by adding 25 kg/odt hydrogen peroxide in the first stage refiner) and reduction of energy demand in refining.

Place, publisher, year, edition, pages
2011. Vol. 26, no 1, 31-46 p.
Keyword [en]
ATMP; TMP; Energy reduction; Hydrogen peroxide; Magnesium hydroxide; Sodium bisulphite; Refiner bleaching
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:miun:diva-13845DOI: 10.3183/NPPRJ-2011-26-01-p031-046ISI: 000293770200004ScopusID: 2-s2.0-79955371638OAI: oai:DiVA.org:miun-13845DiVA: diva2:419559
Available from: 2011-05-27 Created: 2011-05-27 Last updated: 2012-04-02Bibliographically 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. 119 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 108
Keyword
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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