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The use of Fenton chemistry for reducing the refining energy during TMP production: the effect of free ferrous and free or chelated ferric ions
Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The potential of using acid hydrogen peroxide under Fenton conditions to lowerthe electrical energy consumed during the production of Black spruce (Piceamariana) thermomechanical pulp (TMP) was investigated in pilot scale. Thechemical system, which consisted of ferrous sulphate, hydrogen peroxide andoptionally an enhancer (such as a chelating agent), was evaluated as an inter-stagetreatment. The produced TMPs were thoroughly characterised in order to explainthe effect of the chemical system on fibre development and to be able to propose amechanism for the impact on refining energy reduction. The possibility to improvethe optical properties by washing, chelating and sodium dithionite or hydrogenperoxide bleaching the treated pulps was evaluated. The system of lignocellulosicmaterial, a Norway spruce (Picea abies) TMP, and Fenton chemistry was alsoevaluated in a model study to understand more about how conditions such as e.g.initial pH, dissolved organic material and reaction time affect the reactions.Ferrous and ferric ions (free and chelated) and different anions were evaluated.Moreover, it was examined whether hydroxyl radicals could be detected andmonitored.The results obtained in pilot scale showed that it is possible to significantly reducethe specific energy consumption by approximately 20% and 35% at a freenessvalue of 100 ml CSF or a tensile index of 45 Nm/g by using 1% and 2% hydrogenperoxide respectively. The energy reduction was obtained without any substantialchange to the fractional composition of the pulp, although tear strength wasslightly reduced, as were brightness and pulp yield. No major differences betweenthe reference pulp and the chemically treated pulps were found with respect tofibre length, width or cross-sectional dimensions. However, the acid hydrogenperoxide-treated pulps tended to have more collapsed fibres, higher flexibility, alarger specific surface area and a lower coarseness value. The yield lossiiiaccompanying the treatment was mainly a consequence of degradedhemicelluloses. It was also found that the total charge of the chemically treatedpulps was higher compared to the reference pulps; something that may haveinfluenced the softening behaviour of the fibre wall.A washing or chelating procedure could significantly reduce the metal ion contentof the chemically treated TMPs. The amount of iron could be further reduced to alevel similar to that of untreated pulps by performing a reducing agent-assistedchelating stage with dithionite. The discoloration could not, however, becompletely eliminated. The brightness decrease of the treated pulps was thereforenot only caused by the greater iron content in the pulp, but was also dependent onthe type of iron compound and/or other coloured compounds connected with theacid hydrogen peroxide treatment. Oxidative bleaching using hydrogen peroxidewas more effective than reductive bleaching using sodium dithionite in regainingthe brightness that was lost during the energy reductive treatment.From the model study and by using a chemiluminescence method, it could beconcluded that hydroxyl radicals were present in the system of Fenton chemicalsand lignocellulosic material (TMP). Initial pH, retention time, pulp consistency,type of catalyst (free or chelated) and dissolved organic material had an impact onthe reactions between TMP and acid hydrogen peroxide. Different anions(sulphate, nitrate and chloride) of ferric ion salt gave a similar catalytic effect.There appeared to be more reactions with the TMP when there was less dissolvedorganic material in the liquid phase from the start. A catalyst of ferrous sulphatehad a greater impact on the pulp (increased total fibre charge and carbonyl groups,more dissolved organic material in filtrate) than ferric ions chelated withethylenediaminetetraacetic acid at an initial pH of about 3-7. If using ferric-EDG(ethanol diglycinic acid) as catalyst, the measured effect on the pulp was similar orless compared to using ferrous sulphate. Ferric-EDG, however, gave higherhydrogen peroxide consumption and more detectable hydroxyl radicals than usingferrous sulphate (initial pH 5-8). It is likely that the iron catalyst must bind to theTMP, or be in close proximity to it, for the hydroxyl radicals to be able to react withthe material.A mechanism was proposed: the hydroxyl radicals generated in the Fentonreaction will probably attack and oxidise the available outer fibre surfaces,weakening these layers, and simultaneously dissolve some of the organic material.This can facilitate fibre development, give a better bonding pulp and reduce theelectrical energy required during refining.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2013. , 102 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 169
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:miun:diva-20737ISBN: 978-91-87557-15-6 (print)OAI: oai:DiVA.org:miun-20737DiVA: diva2:679758
Supervisors
Available from: 2013-12-16 Created: 2013-12-16 Last updated: 2013-12-16Bibliographically approved
List of papers
1. Energy efficient refining of Black spruce TMP by using acid hydrogen peroxide: Part 1. A pilot plant study
Open this publication in new window or tab >>Energy efficient refining of Black spruce TMP by using acid hydrogen peroxide: Part 1. A pilot plant study
2009 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 24, no 3, 255-265 p.Article in journal (Refereed) Published
Abstract [en]

The potential of using acid hydrogen peroxide for lowering the

electrical energy consumption during production of Black spruce (Picea

mariana) thermomechanical pulp (TMP) was investigated. The chemical

system, which consisted of ferrous sulphate, hydrogen peroxide and

optionally an enhancer [ethylenediaminetetraacetic acid (sodium salt),

3,4-dimethoxybenzyl (veratryl) alcohol or oxalic acid/sodium oxalate],

was evaluated as an inter-stage treatment where the primary refiner was

used as a mixer. The approach has the advantage of minimising the

capital investment needed for implementation, thus being directly

applicable in a thermomechanical pulping process consisting of two or

more refiners in series.

The results obtained in a pilot plant trial revealed that is was

possible to significantly reduce the specific energy consumption by

approximately 20-and 35% to a freeness value of 100 ml CSF by using 1

and 2% hydrogen peroxide, respectively. The energy reduction could be

obtained without any substantial change in fibre length, fractional

composition of the pulp or tensile strength of the paper. The tear

strength was slightly reduced however, as was the pulp yield. The major

drawback with the acid hydrogen peroxide system was a reduction in

brightness by at least 6 brightness units. The addition level of

ferrous sulphate was too high and the possibility to reducing the

discoloration should be considerable when the chemical system is

optimized.

 

Place, publisher, year, edition, pages
Stockholm: SPCI, 2009
Keyword
TMP, Black spruce, Energy reduction, Hydrogen peroxide, Ferrous sulphate, Refining, Inter-stage treatment, Pulp and paper properties, Fenton’s reagent.
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-8823 (URN)10.3183/NPPRJ-2009-24-03-p255-265 (DOI)000270862100001 ()2-s2.0-72749098172 (Scopus ID)
Projects
Mechanical Pulp Industrial Research College
Available from: 2009-04-29 Created: 2009-04-29 Last updated: 2013-12-16Bibliographically approved
2. Energy efficient refining of Black spruce TMP by using acid hydrogen peroxide: Part 2. Washing, chelating and bleaching studies
Open this publication in new window or tab >>Energy efficient refining of Black spruce TMP by using acid hydrogen peroxide: Part 2. Washing, chelating and bleaching studies
2009 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 24, no 3, 266-272 p.Article in journal (Refereed) Published
Abstract [en]

The acid hydrogen peroxide system has the potential to significantly

reduce the specific energy consumption in the production of softwood

thermomechanical pulps (TMPs). A drawback of the chemical system is

discoloration of the pulp during refining. The work presented in this

study evaluates the possibility to regain the lost brightness by

washing, chelating and sodium dithionite or hydrogen peroxide bleaching

of the treated pulps.

A washing or chelating procedure can reduce the metal ion content of

the chemically treated TMPs considerably, though brightness can be

increased by a maximum of two ISO units. The amount of iron can be

further reduced to a level similar to that of untreated pulps by

performing a reducing agent-assisted chelating stage (Q(Y)) with

dithionite. The discoloration cannot,, however, be completely

eliminated. The brightness decrease-of the treated pulps is thus not

only caused by higher iron content in the pulp, but is also dependent

on the type of iron compound and/or other coloured compounds connected

with the acid hydrogen peroxide treatment.

Oxidative bleaching with hydrogen peroxide (P) is more effective than

reductive bleaching with sodium dithionite in regaining the brightness

lost during the energy reductive treatment. By using a Q(Y) P sequence,

a hydrogen peroxide charge of 3.8% was needed to reach an ISO

brightness of 75% for the chemically treated pulps. The corresponding

hydrogen peroxide charge for the untreated TMP reference was 2.5%.

 

Place, publisher, year, edition, pages
Stockholm: SPCI, 2009
Keyword
TMP, Black spruce, Energy reduction, Bleaching, Hydrogen peroxide, Sodium dithionite, Brightness, Metals
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-8825 (URN)10.3183/NPPRJ-2009-24-03-p266-272 (DOI)000270862100002 ()2-s2.0-72749097945 (Scopus ID)
Projects
Mechanical Pulp Industrial Research College
Available from: 2009-04-29 Created: 2009-04-29 Last updated: 2013-12-16Bibliographically approved
3. Energy efficient refining of Black spruce TMP by using acid hydrogen peroxide: Part 3. Chemical and morphological characterisation
Open this publication in new window or tab >>Energy efficient refining of Black spruce TMP by using acid hydrogen peroxide: Part 3. Chemical and morphological characterisation
2010 (English)In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 36, no 1-2, 2-9 p.Article in journal (Refereed) Published
Keyword
Thermomechanical pulp, Energy reduction, Hydrogen peroxide, Fibre dimensions, Cross-section, Chemical composition
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-8826 (URN)
Projects
Mechanical Pulp Industrial Research College
Available from: 2009-04-29 Created: 2009-04-29 Last updated: 2013-12-16Bibliographically approved
4. Acid hydrogen peroxide treatment of Norway Spruce TMP: A model study using free ferrous ions and ferric ions chelated with EDTA as catalysts
Open this publication in new window or tab >>Acid hydrogen peroxide treatment of Norway Spruce TMP: A model study using free ferrous ions and ferric ions chelated with EDTA as catalysts
2013 (English)In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 33, no 4, 267-285 p.Article in journal (Refereed) Published
Abstract [en]

The acid hydrogen peroxide system has been evaluated in more detail in the presence of a coarse Norway spruce thermomechanical pulp (TMP). The effects of parameters on the reactions involved were determined, such as pH, retention time, pulp consistency, type of iron catalyst, and the amount of dissolved organic material. Residual hydrogen peroxide, chemical oxygen demand, dissolved iron, and total fiber charge were quantified and the hydroxyl radical activity was monitored. The results showed that a catalyst of free ferrous ions (Fe2+) gave more reactions with the lignocellulosic material than ferric ions (Fe3+) chelated with EDTA. Furthermore, there were somewhat more reactions with the TMP when there was less dissolved organic material in the liquid phase from the start. Hydroxyl radicals were detected in all cases, but the level differed depending on the conditions used. It is likely that the iron must bind with the TMP or be in close proximity for the hydroxyl radicals to react with the pulp.

Keyword
Hydrogen peroxide, TMP, Fenton's reagent, hydroxyl radicals, EDTA, COD, total fiber charge
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-19831 (URN)10.1080/02773813.2013.792840 (DOI)000320098800004 ()2-s2.0-84879089637 (Scopus ID)
Available from: 2013-09-05 Created: 2013-09-05 Last updated: 2013-12-16Bibliographically approved
5. Acid Hydrogen Peroxide Treatment of Norway Spruce TMP: The Effect of an Extended pH Range when Catalyzed by Free Ferrous and Free or EDG/EDTA-Chelated Ferric Ions
Open this publication in new window or tab >>Acid Hydrogen Peroxide Treatment of Norway Spruce TMP: The Effect of an Extended pH Range when Catalyzed by Free Ferrous and Free or EDG/EDTA-Chelated Ferric Ions
2014 (English)In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 34, no 2, 135-155 p.Article in journal (Refereed) Published
Abstract [en]

The influence of different types of iron salts (i.e., ferrous or ferric cations with sulphate, nitrate or chloride anions) on the reaction between coarse thermomechanical pulp and acid hydrogen peroxide (Fenton chemistry) was studied when the initial pH was 3.2 and 5.3. Also, ferric ions chelated with EDTA or EDG at different molar ratios were compared with ferrous sulphate when the initial pH was extended from about 3 to 8. Different anions of ferric ion salt gave a similar catalytic effect. At an initial pH of 7–8, the ferric-EDTA catalyzed reaction resulted in similar or higher hydrogen peroxide consumption and more detectable hydroxyl radicals than the ferrous sulphate catalyzed reaction, but less reaction with the pulp was indicated. Between pH 5–8, using Fe-EDG as a catalyst gave higher hydrogen peroxide consumption and more detectable hydroxyl radicals than if using ferrous sulphate; however, the measured effect on the pulp was similar or less.

Keyword
Hydrogen peroxide, TMP, Fenton's reagent, hydroxyl radicals, ferrous, ferric, sulphate, nitrate, chloride, EDTA, EDG, TOC, total fiber charge
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-20729 (URN)10.1080/02773813.2013.844166 (DOI)000328465700005 ()2-s2.0-84890598506 (Scopus ID)
Available from: 2013-12-16 Created: 2013-12-16 Last updated: 2014-01-09Bibliographically approved

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