Hardwood kraft pulp structural features affecting refinability

Abstract Two industrial bleached Eucalyptus globulus kraft pulps (pulps A and B), cooked from the same wood stock with slightly different alkali charges and temperatures, showed different refinability in the laboratory beating of pulp using a PFI mill. The easy to refine pulp (A) and the difficult to refine pulp (B) did not reveal significant differences in their biometric data and general chemical composition, but pulp A showed ca. 5%–10% higher mechanical strength and twice as high refinability compared to pulp B. These differences were ascribed to slightly higher intrinsic viscosity and higher xylan content of pulp A compared to pulp B (1010 vs. 860 cm3 g−1 and 20.1 vs. 17.8%, respectively). The xylan structure and its location in fiber cells were also different, which affected the pulp’s refinability. The presence of high proportion of xylan in the bulk of fibers, rather than in their outer layers, seems to favor the pulp beating. An interpretation was also proposed, according to which the aggregation of cellulose fibrils during cooking, i.e. a partial coalescence of fibril crystallites, may also have a negative effect on pulp refinability.

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Prebleaching of eucalypt kraft pulp with OP stages: Effect of an acid pretreatment or chelation step

TAPPI Journal ◽

10.32964/tj11.6.31 ◽

2012 ◽

Vol 11 (6) ◽

pp. 31-38

Author(s):

TATIANA M. PÓVOAS ◽

DINA A.G. ANGÉLICO ◽

ANA P.V. EGAS ◽

PEDRO E.G. LOUREIRO ◽

LICÍNIO M. GANDO-FERREIRA ◽

...

Keyword(s):

Eucalyptus Globulus ◽

Comparative Evaluation ◽

Kraft Pulp ◽

Kraft Pulps ◽

Acid Pretreatment ◽

High Brightness ◽

Pulp Viscosity ◽

Brightness Reversion

We conducted a comparative evaluation of different treatments for the bleaching of eucalypt kraft pulps beginning with OP stages. The treatments tested were (1) an acid chelation stage with DTPA (OQP sequence); (2) a hot acid stage (AOP sequence); and (3) a chelant addition into the alkaline oxygen stage ((OQ)P and A(OQ)P sequences). The latter strategy was also studied for environmental reasons, as it contributes to the closure of the filtrate cycle. The OQP sequence leads to the highest brightness gain and pulp viscosity and the lowest peroxide consumption caused by an efficient metals control. Considering that the low biodegradability of the chelant is a problem, the A(OQ)P sequence is an interesting option because it leads to reduced peroxide consumption (excluding OQP) while still reaching high brightness values and similar brightness reversion to OQP prebleaching, with only a viscosity loss of 160 dm3/kg. Therefore, a hot acid stage could be considered when a separate acid Q stage is absent in a prebleaching sequence of Eucalyptus globulus kraft pulps involving OP stages.

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Optimization of elemental chlorine-free bleaching for a softwood kraft pulp • part 2: economic analysis of chemical and steam consumption

TAPPI Journal ◽

10.32964/tj9.9.47 ◽

2010 ◽

Vol 9 (9) ◽

pp. 47-53 ◽

Cited By ~ 2

Author(s):

BRIAN N. BROGDON

Keyword(s):

Chlorine Dioxide ◽

Previous Investigation ◽

Kraft Pulp ◽

Energy Costs ◽

Alkaline Extraction ◽

Stage Versus ◽

Kraft Pulps ◽

Steam Consumption ◽

Elemental Chlorine ◽

Softwood Kraft Pulp

Our previous investigation [1] re-analyzed the data from Basta and co-workers (1992 TAPPI Pulping Conference) to demonstrate how oxidative alkaline extraction can be augmented and how these changes affect chlorine dioxide consumption with elemental chlorine-free (ECF) sequences. The current study manipulates extraction delignification variables to curtail bleaching costs with a conventional U.S. Southern softwood kraft pulp. The economic advantages of ~0.35% to 0.65% H2O2 peroxide reinforcement in a 70°C (EOP)-stage versus 90°C (EO)-stage are predisposed to the brightness targets, to short or long bleach sequences, and to mill energy costs. Minimized bleaching costs are generally realized when a 90°C (EO) is employed in D0(EO)D1 bleaching, whereas a 70°C (EOP) is economically advantageous for D0(EOP)D1E2D2 bleaching. The findings we disclose here help to clarify previous ECF optimization studies of conventional softwood kraft pulps.

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Cellulose Nanofibril (CNF) Films and Xylan from Hot Water Extracted Birch Kraft Pulps

Applied Sciences ◽

10.3390/app9163436 ◽

2019 ◽

Vol 9 (16) ◽

pp. 3436 ◽

Cited By ~ 4

Author(s):

Marc Borrega ◽

Hannes Orelma

Keyword(s):

Food Packaging ◽

Kraft Pulp ◽

Barrier Properties ◽

Hot Water ◽

Kraft Pulps ◽

Cellulose Nanofibril ◽

Vapour Permeability ◽

Transparent Films ◽

Cnf Films ◽

Birch Kraft Pulp

The effects of xylan extraction from birch kraft pulp on the manufacture and properties of cellulose nanofibril (CNF) films were here investigated. Hot water extractions of bleached and unbleached kraft pulps were performed in a flow-through system to remove and recover the xylan. After the extraction, the pulps were oxidized with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and fibrillated in a high-pressure microfluidizer. Compared to CNF from bleached kraft pulp, the CNF dispersions obtained from water-extracted pulps were less viscous and generally contained a higher amount of microfiber fragments, although smaller in size. In all cases, however, smooth and highly transparent films were produced from the CNF dispersions after the addition of sorbitol as plasticizer. The CNF films made from water-extracted pulps showed a lower tensile strength and ductility, probably due to their lower xylan content, but the stiffness was only reduced by the presence of lignin. Interestingly, the CNF films from water-extracted bleached pulps were less hydrophilic, and their water vapour permeability was reduced up to 25%. Therefore, hot water extraction of bleached birch kraft pulp could be used to produce CNF films with improved barrier properties for food packaging, while obtaining a high-purity xylan stream for other high-value applications.

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Fate of phosphorus in the recovery cycle of the kraft pulping process

TAPPI Journal ◽

10.32964/tj19.3.139 ◽

2020 ◽

Vol 19 (3) ◽

pp. 139-148

Author(s):

MARYAM SADEGH MOUSAVI ◽

NIKOLAI DEMARTINI

Keyword(s):

Kraft Pulp ◽

Pulp Mill ◽

Field Studies ◽

Kraft Pulping ◽

Pulp Mills ◽

Recovery Cycle ◽

Green Liquor ◽

Green Liquor Dregs ◽

Kraft Pulp Mills ◽

Negative Effect

The accumulation of nonprocess elements in the recovery cycle is a common problem for kraft pulp mills trying to reduce their water closure or to utilize biofuels in their lime kiln. Nonprocess elements such as magne-sium (Mg), manganese (Mn), silicon (Si), aluminum (Al), and phosphorus (P) enter the recovery cycle via wood, make-up chemicals, lime rock, biofuels, and process water. The main purge point for these elements is green liquor dregs and lime mud. If not purged, these elements can cause operational problems for the mill. Phosphorus reacts with calcium oxide (CaO) in the lime during slaking; as a result, part of the lime is unavailable for slaking reactions. The first part of this project, through laboratory work, identified rhenanite (NaCa(PO4)) as the form of P in the lime cycle and showed the negative effect of P on the availability of the lime. The second part of this project involved field studies and performing a mass balance for P at a Canadian kraft pulp mill.

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Strong paper from spruce CTMP – Part II: Effect of pressing at nip press temperatures above the lignin softening temperature

Nordic Pulp & Paper Research Journal ◽

10.1515/npprj-2018-3009 ◽

2018 ◽

Vol 33 (1) ◽

pp. 142-149 ◽

Cited By ~ 1

Author(s):

Sven Norgren ◽

Gunilla Pettersson ◽

Hans Höglund

Keyword(s):

Compression Strength ◽

Kraft Pulp ◽

Softening Temperature ◽

Strength Properties ◽

Kraft Pulps ◽

Cationic Starch ◽

Tensile Index ◽

Very High

Abstract The main objective of the current study was to demonstrate that it is possible to enhance strength properties of sheets from spruce HT-CTMP and CTMP furnishes up to the same level as is common on sheets from softwood kraft pulps by changing conditions in papermaking. To achieve that, sheets of spruce HT-CTMP and CTMP were consolidated at densities close to that of the reference bleach kraft pulp by pressing at press nip temperatures well above the tack and softening temperatures of lignin. On sheets from spruce CTMP (CSF 420 ml), where the fibers were surface treated with cationic starch, it was possible to reach tensile index at the same level as on sheets from the untreated reference kraft pulp. The compression strength (SCT) of CTMP and HT-CTMP sheets, which were achieved at the highest press nip temperature (200 °C) in the study, was equal to or higher than that of the reference kraft pulp sheets. The results show that there is a great yet unexploited potential in papermaking from spruce HT-CTMP and CTMP furnishes, which could be utilized in manufacturing of products where very high requirements upon strength is demanded.

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Investigations into Laccase-Mediator Delignification of Kraft Pulps

Holzforschung ◽

10.1515/hf.1999.082 ◽

1999 ◽

Vol 53 (5) ◽

pp. 498-502 ◽

Cited By ~ 29

Author(s):

J. Sealey ◽

A.J. Ragauskas ◽

T.J. Elder

Keyword(s):

Bond Dissociation Energy ◽

Dissociation Energy ◽

Kraft Pulp ◽

Substituent Effects ◽

Computational Results ◽

Kraft Pulps ◽

Bond Dissociation ◽

Structure Activity ◽

Softwood Kraft Pulp

SummaryThe structure activity effects of 1-hydroxy benzotriazole and phthalimide derivatives as mediators for laccase were studied. Using a softwood kraft pulp it was shown that the N-hydroxy unit is a key component of 1-hydroxybenzotriazole for efficient laccase mediator delignification to occur. It was also found that the 1-hydroxybenzotriazole structure was very sensitive to substituent effects with respect to laccase-mediator delignification. Computational results from PM3 indicate that the bond dissociation energy, and electronic factors of the radical may contribute to the efficiency of the mediator for LMS delignification.

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Evidence for the formation of lignin-hexenuronic acid-xylan complexes during modified kraft pulping processes

Holzforschung ◽

10.1515/hf.2006.022 ◽

2006 ◽

Vol 60 (2) ◽

pp. 137-142 ◽

Cited By ~ 11

Author(s):

Zhi-Hua Jiang ◽

Jean Bouchard ◽

Richard Berry

Keyword(s):

Acid Hydrolysis ◽

Kraft Pulp ◽

Kraft Pulping ◽

Order Kinetic ◽

Kraft Pulps ◽

First Order ◽

Pseudo First Order ◽

Hexenuronic Acid ◽

Kinetics Of ◽

Hydrolysis Of

Abstract The finding that hexenuronic acid (HexA) groups can be selectively removed from kraft pulps by acid hydrolysis has provided an opportunity to reduce bleaching chemicals. However, there is evidence that the acid hydrolysis is not uniform. In this report, we evaluate the kinetics of acid hydrolysis of HexA in a xylan sample enriched with HexA, a conventional kraft pulp, and three modified kraft pulps: anthraquinone pulp (Kraft-AQ), polysulfide pulp (PS), and polysulfide-anthraquinone pulp (PS-AQ). We found that HexA present in the xylan and conventional kraft pulp behaved similarly toward the acid hydrolysis throughout. On the other hand, HexA present in the Kraft-AQ, PS-AQ and PS pulps was heterogeneous toward acid hydrolysis and the reaction can be separated into two pseudo-first-order kinetic phases, each of which has a different rate constant. The kinetic data provide evidence for the formation of lignin-HexA-xylan complexes during modified kraft pulping processes.

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Fate of Residual Lignin during Delignification of Kraft Pulp by Trametes versicolor

Applied and Environmental Microbiology ◽

10.1128/aem.64.6.2117-2125.1998 ◽

1998 ◽

Vol 64 (6) ◽

pp. 2117-2125 ◽

Cited By ~ 15

Author(s):

Ian D. Reid

Keyword(s):

Trametes Versicolor ◽

Kraft Pulp ◽

Lignin Degradation ◽

Water Soluble ◽

Kraft Pulps ◽

Residual Lignin ◽

Spruce Wood ◽

Single Ring ◽

Enzyme Bleaching ◽

By Products

ABSTRACT The fungus Trametes versicolor can delignify and brighten kraft pulps. To better understand the mechanism of this biological bleaching and the by-products formed, I traced the transformation of pulp lignin during treatment with the fungus. Hardwood and softwood kraft pulps containing 14C-labelled residual lignin were prepared by laboratory pulping of lignin-labelled aspen and spruce wood and then incubated with T. versicolor. After initially polymerizing the lignin, the fungus depolymerized it to alkali-extractable forms and then to soluble forms. Most of the labelled carbon accumulated in the water-soluble pool. The extractable and soluble products were oligomeric; single-ring aromatic products were not detected. The mineralization of the lignin carbon to CO2 varied between experiments, up to 22% in the most vigorous cultures. The activities of the known enzymes laccase and manganese peroxidase did not account for all of the lignin degradation that took place in the T. versicolor cultures. This fungus may produce additional enzymes that could be useful in enzyme bleaching systems.

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Changes in the lignin-carbohydrate complex in softwood kraft pulp during kraft and oxygen delignification

Holzforschung ◽

10.1515/hf.2004.114 ◽

2004 ◽

Vol 58 (6) ◽

pp. 603-610 ◽

Cited By ~ 48

Author(s):

Martin Lawoko ◽

Rickard Berggren ◽

Fredrik Berthold ◽

Gunnar Henriksson ◽

Göran Gellerstedt

Keyword(s):

Kraft Pulp ◽

Kappa Number ◽

Kraft Pulps ◽

Residual Lignin ◽

Oxygen Delignification ◽

Number Range ◽

Morphological Aspects ◽

Carbohydrate Complex ◽

Softwood Kraft Pulp ◽

Hydrolysis Of

Abstract Three kraft pulps in the kappa number range between 50 and 20 and the same pulps oxygen-delignified to similar lignin contents (kappa approximately 6) were analyzed for lignin-carbohydrate complexes (LCC) by a method based on selective enzymatic hydrolysis of the cellulose, and quantitative fractionation of the LCC. Between 85 and 90% of residual lignin in the unbleached kraft pulp and all residual lignin in the oxygen-delignified pulps were isolated as LCC. Three types of complexes were found; viz., xylan-lignin, glucomannan-lignin-xylan and glucanlignin complexes. After pulping to a high kappa number, most of the residual lignin was linked to xylan. Different delignification rates were observed so that most of the residual lignin was linked to glucomannan when the pulping was extended to a low kappa number. With increasing degree of oxygen delignification, a similar trend in the delignification rates of LCC was observed so that the residual lignin was increasingly linked to glucomannan. Complex LCC network structures seemed to be degraded into simpler structures during delignification. The differences in delignification rates are discussed with reference to the solubility properties and structural differences of LCC, and to morphological aspects of the pulp.

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Structural differences between reaction wood and opposite wood with different drying temperatures

BioResources ◽

10.15376/biores.15.2.4407-4416 ◽

2020 ◽

Vol 15 (2) ◽

pp. 4407-4416

Author(s):

Ivan Klement ◽

Tatiana Vilkovská ◽

Peter Vilkovský ◽

Štěpán Hýsek

Keyword(s):

Physical And Mechanical Properties ◽

Thick Wall ◽

Normal Wood ◽

Reaction Wood ◽

Drying Time ◽

Fiber Cells ◽

Opposite Wood ◽

Negative Effect ◽

Higher Temperature ◽

End Times

Reaction wood is characterized by having different anatomical and chemical features than normal wood. The different composition of cell walls, the higher quantitative proportion of thick-wall fiber cells, diameter, and the abundance of vessels have remarkable effects on reaction wood’s physical and mechanical properties. Reaction wood has fewer vascular cells. In addition, it has a smaller lumen diameter, which results in reduced permeability. Therefore, reaction wood is more difficult to dry at a certain moisture content. The differences in the drying times of the reaction wood and the normal wood were largest at a temperature of 60 °C and durations greater than 30 h, and the reaction wood dried more slowly. At a temperature of 120 °C, the differences in drying time were minimalized, and drying end times were almost identical. The expected negative effect of higher temperature on the morphology of reaction wood and opposition wood was not confirmed.

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