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ATMP Process: Improved Energy Efficiency in TMP Refining Utilizing Selective Wood Disintegration and Targeted Application of Chemicals
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
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 [en]
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: urn:nbn:se:miun:diva-13844ISBN: 978-91-86694-34-0OAI: oai:DiVA.org:miun-13844DiVA: diva2:419665
Public defence
2011-05-05, 10:18 (English)
Supervisors
Available from: 2011-05-27 Created: 2011-05-27 Last updated: 2012-07-30Bibliographically approved
List of papers
1. Review: Reduction of energy consumption in TMP refining through mechanical pre-treatment of wood chips
Open this publication in new window or tab >>Review: Reduction of energy consumption in TMP refining through mechanical pre-treatment of wood chips
2010 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, no 2, 156-161 p.Article, 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.

Keyword
TMP refining; Chip pre-compression; Chip pre-treatment; Energy reduction; ATMP
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-11886 (URN)10.3183/NPPRJ-2010-25-02-p156-161 (DOI)000279341100003 ()2-s2.0-79551553499 (ScopusID)
Available from: 2010-07-30 Created: 2010-07-30 Last updated: 2016-09-22Bibliographically approved
2. Improvement of energy efficiency in TMP refining by selective wood disintegration and targeted application of chemicals
Open this publication in new window or tab >>Improvement of energy efficiency in TMP refining by selective wood disintegration and targeted application of chemicals
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.

Keyword
ATMP; TMP; Energy reduction; Hydrogen peroxide; Magnesium hydroxide; Sodium bisulphite; Refiner bleaching
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-13845 (URN)10.3183/NPPRJ-2011-26-01-p031-046 (DOI)000293770200004 ()2-s2.0-79955371638 (ScopusID)
Available from: 2011-05-27 Created: 2011-05-27 Last updated: 2012-04-02Bibliographically approved
3. Peroxide-based ATMP refining of spruce: energy efficiency, fibre properties and pulp quality
Open this publication in new window or tab >>Peroxide-based ATMP refining of spruce: energy efficiency, fibre properties and pulp quality
2011 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 26, no 1, 47-63 p.Article in journal (Refereed) Published
Abstract [en]

Pilot scale refining of White spruce using a modified TMP refining process (ATMP - Advanced Thermomechanical Pulp) was studied. ATMP combines selective wood disintegration by mechanical pretreatment and refining at elevated intensity with chemical treatment after defibration (in this study hydrogen peroxide, alone and in combination with alkali). The electrical energy efficiency and pulp quality using ATMP were evaluated and compared to a conventional TMP process. One goal was to retain the combination of optical properties and strength of typical TMP. Fibre properties (structural dimensions, external and internal fibre development) as well as the amount of split fibres resulting from TMP and ATMP processes were compared. The results indicate an electrical energy efficiency improvement potential of 0.65 MWh/odt (34%) at tensile index 30 N.m/g of ATMP compared to reference TMP. All ATMP pulps retained their TMP character, i.e. the relationships between light scattering coefficient, density, elongation properties and strength that are important for printing paper. ATMP had a significantly lower content of shives and higher external and internal fibre development compared to TMP at equal energy application. The long fibre fraction of ATMP also contained significantly higher amount of split fibres. The brightness of ATMP produced with addition of hydrogen peroxide (28 kg/odt) and magnesium hydroxide (14 kg/odt) was 14 ISO % higher compared to TMP.

Keyword
ATMP; TMP; Energy reduction; Fibre characterisation; Hydrogen peroxide; Magnesium hydroxide; Refiner bleaching
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-13846 (URN)10.3183/NPPRJ-2011-26-01-p047-063 (DOI)000293770200005 ()2-s2.0-79955447235 (ScopusID)
Available from: 2011-05-27 Created: 2011-05-27 Last updated: 2012-03-21Bibliographically approved
4. Role of equipment configuration and process chemicals in peroxide-based ATMP refining of spruce
Open this publication in new window or tab >>Role of equipment configuration and process chemicals in peroxide-based ATMP refining of spruce
2011 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 26, no 2, 232-247 p.Article in journal (Refereed) Published
Abstract [en]

Pilot scale refining of White spruce using ATMP (Advanced Thermomechanical Pulp) process was studied. Conventional TMP process, where first stage refiner was equipped with low-intensity segments, was the first reference used in the trial. Another reference was a TMP process with modified equipment configuration (ATMP (aq.)). Modifications consisted of mechanical pre-treatment of chips in Impressafiner and Fiberizer prior to first stage relining at elevated intensity. TMP and ATMP (aq.) references were compared to the ATMP (Mg+P) process which had the same equipment configuration as the ATMP (aq.) and where fibre development in refining was further enhanced using hydrogen peroxide and magnesium hydroxide. The main goal of the trial was to separate the effects of equipment configuration from the effects of process chemicals in ATMP refining. Impact on the development of individual fibre properties. properties of fines fraction. whole pulp properties and laboratory sheet properties was studied and linked to the energy efficiency in refining Electrical energy demand, needed to reach the tensile index of 30 Nm/g could be reduced by 0.42 MWh/odt (28 %) compared to conventional TMP process when mechanical pre-treatment and refining at elevated intensity (ATMP (aq.)) were utilized. Relining energy reduction was 0.49 MWh/odt (33 %) when ATMP (Mg+P) concept was used. The content of shives was considerably lower for ATMP and ATMP (aq.) pulps compared to the TMP reference. ATMP (Mg+P) also had higher brightness compared to the references, an increase by 10 ISO % for a 26 kg/odt hydrogen peroxide charge.

Keyword
ATMP; TMP; Energy reduction; Fibre characterisation; Fines; Hydrogen peroxide; Magnesium hydroxide; Refiner bleaching
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-13858 (URN)000294524200002 ()2-s2.0-80052377787 (ScopusID)
Available from: 2011-05-30 Created: 2011-05-30 Last updated: 2012-04-18Bibliographically approved
5. Using ATMP Technology to Improve Energy Efficiency and Pulp Quality in Production of SC magazine Paper
Open this publication in new window or tab >>Using ATMP Technology to Improve Energy Efficiency and Pulp Quality in Production of SC magazine Paper
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-13849 (URN)
Available from: 2011-05-27 Created: 2011-05-27 Last updated: 2014-08-14Bibliographically approved
6. Bleaching efficiency in peroxide-based ATMP process compared to conventional bleaching
Open this publication in new window or tab >>Bleaching efficiency in peroxide-based ATMP process compared to conventional bleaching
(English)In: Holzforschung, ISSN 0018-3830Article in journal (Refereed) Submitted
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-13850 (URN)
Available from: 2011-05-27 Created: 2011-05-27 Last updated: 2011-05-27Bibliographically approved

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