Change search
Link to record
Permanent link

Direct link
BETA
Brännvall, ElisabetORCID iD iconorcid.org/0000-0002-8992-3623
Publications (9 of 9) Show all publications
Brännvall, E. & Kulander, I. (2019). Consequences in a softwood kraft pulp mill of initial high alkali concentration in the impregnation stage. Nordic Pulp & Paper Research Journal, 34(1), 28-35
Open this publication in new window or tab >>Consequences in a softwood kraft pulp mill of initial high alkali concentration in the impregnation stage
2019 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 34, no 1, p. 28-35Article in journal (Refereed) Published
Abstract [en]

Impregnation with high initial concentration is fast and efficient, leading to a homogeneous delignification in the subsequent cook, resulting in improved screened pulp yield. To obtain high initial alkali concentration, the white liquor flow needs to be significantly increased. The moisture content of the wood chips and the alkali concentration of the white liquor limit the initial alkali concentration of the impregnation liquor that can be reached. It is therefore of interest to evaluate the possibility to implement high alkali impregnation (HAI) industrially and the consequences this would have on the mill system. The effect of HAI on mass and energy balances in a kraft pulp mill has been studied using mill model simulations. The sensitivity to disturbances in important parameters for process control has been compared to impregnation scenarios used industrially. It was shown that high initial alkali concentration can be achieved on industrial scale by increased white liquor flow. HAI has a positive effect on recovery flows and reduces the need for make-up chemicals. The HAI concept is less sensitive to variations in process parameters, such as chip moisture and white liquor concentration, thus diminishing the risk of alkali depletion in chip cores. © 2019 Brännvall and Kulander.

Keywords
Delignification, Impregnation, Softwood, effective alkali, kraft cooking, simulation model; pulp mill, yield
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-37837 (URN)10.1515/npprj-2018-0026 (DOI)2-s2.0-85061696612 (Scopus ID)
Available from: 2019-02-28 Created: 2019-02-28 Last updated: 2019-03-05Bibliographically approved
Svärd, A., Moriana, R., Brännvall, E. & Edlund, U. (2019). Rapeseed Straw Biorefinery Process. ACS Sustainable Chemistry and Engineering, 7(1), 790-801
Open this publication in new window or tab >>Rapeseed Straw Biorefinery Process
2019 (English)In: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 7, no 1, p. 790-801Article in journal (Refereed) Published
Abstract [en]

A rapeseed straw biorefinery process was demonstrated with more than 50% of the straw recovered as products. Xylan with a weight-average molecular weight of 56 760 g/mol was extracted in an alkaline step. The straw residue was subjected to soda pulping, resulting in cellulose-rich fibers and a lignin-rich liquid fraction. The lignin contained syringyl and guaiacyl aromatic structural units in a 1/0.75 ratio. The cellulose pulp was bleached, resulting in a cellulose fraction of 85% purity and a crystallinity index (CI) of 83%. Two grades of nanocellulose, CNF and CNC, were isolated from the bleached pulp. The CNF was very heterogeneous in size with an average diameter of 4 nm and an average length of 1177 nm. The CNC had an average diameter of 6 nm and an average particle length of 193 nm. CNF and CNC had good thermal stability and an aspect ratio of 294 and 32, respectively.

Place, publisher, year, edition, pages
American Chemical Society, 2019
Keywords
Biorefinery, Bleached pulp, Canola straw, Lignin; Nanocellulose, hydrothermal extraction, xylan
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-36956 (URN)10.1021/acssuschemeng.8b04420 (DOI)2-s2.0-85058836615 (Scopus ID)
Funder
Swedish Research Council Formas, 2013-844
Note

cited By 0; Article in Press

Available from: 2019-01-02 Created: 2019-01-02 Last updated: 2019-07-05Bibliographically approved
Brännvall, E. (2018). Increasing pulp yield in kraft cooking of softwoods by high initial effective alkali concentration (HIEAC) during impregnation leading to decreasing secondary peeling of cellulose. Holzforschung, 72(10), 819-827
Open this publication in new window or tab >>Increasing pulp yield in kraft cooking of softwoods by high initial effective alkali concentration (HIEAC) during impregnation leading to decreasing secondary peeling of cellulose
2018 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, no 10, p. 819-827Article in journal (Refereed) Published
Abstract [en]

Pulp yield can be improved by a more homogeneous delignification of the chips, achieved by improved impregnation prior to the cooking stage. Complete and efficient impregnation is obtained by increasing the diffusion rate by means of an impregnation liquor with a high initial effective alkali concentration (HIEAC). In the present study, the effect of HIEAC in the impregnation was evaluated and compared to a reference impregnation procedure and a prolonged impregnation. After the various impregnation scenarios, the alkali concentration was always adjusted to the same level in the beginning of the cooking stage. Impregnation with a HIEAC resulted in yield improvements by 1-1.5% units, due to a higher cellulose yield and possibly also to higher yield of glucomannan. The HIEAC with an even alkali distribution within the chips prior to the cooking stage resulted in a more uniform delignification carbohydrate degradation. Yield increase obtained by uniform delignification is due to both decreased shives content as well as less secondary peeling.

Keywords
chemical composition, diffusion, high initial effective alkali concentration (HIEAC), homogeneous delignification, impregnation, kraft pulping, molecular mass distribution (MMD), peeling, pulp yield, softwood, Cellulose, Delignification, Kraft process, Kraft pulp, Molecular mass, Softwoods, Alkali concentrations, Chemical compositions, Diffusion rate, Kraft cooking, Molecular mass distributions, Pulp yields, Yield Improvement, Yield increase, Pulp cooking
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-33965 (URN)10.1515/hf-2018-0011 (DOI)2-s2.0-85048776090 (Scopus ID)
Available from: 2018-07-02 Created: 2018-07-02 Last updated: 2018-12-12Bibliographically approved
Svärd, A., Brännvall, E. & Edlund, U. (2018). Modified and thermoplastic rapeseed straw xylan: A renewable additive in PCL biocomposites. Industrial crops and products (Print), 119, 73-82
Open this publication in new window or tab >>Modified and thermoplastic rapeseed straw xylan: A renewable additive in PCL biocomposites
2018 (English)In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 119, p. 73-82Article in journal (Refereed) Published
Abstract [en]

Xylan extracted from rapeseed straw was chemically modified to gain hydrophobic and thermoplastic properties via macroinitiator formation followed by a free radical grafting-from polymerization with octadecyl acrylate. Biocomposites were then prepared by incorporation of 5 or 20% (w/w) rapeseed straw xylan into a poly(ε-caprolactone) (PCL) matrix by melt extrusion. The grafted xylan was homogeneously distributed within the biocomposite and reinforced the PCL matrix while at the same time preserving the ability to elongate to tensile strains >500%. Analogous biocomposites made from unmodified xylan in a PCL matrix resulted in heterogeneous mixtures and brittle tensile properties.

Keywords
Rapeseed/canola straw, Extraction, Autohydrolysis, Severity factor, Hemicellulose
National Category
Polymer Technologies
Identifiers
urn:nbn:se:ri:diva-33752 (URN)10.1016/j.indcrop.2018.03.067 (DOI)2-s2.0-85045072624 (Scopus ID)
Available from: 2018-05-02 Created: 2018-05-02 Last updated: 2018-08-13Bibliographically approved
Brännvall, E. & Reimann, A. (2018). The balance between alkali diffusion and alkali consuming reactions during impregnation of softwood. Impregnation for kraft pulping revisited. Holzforschung, 72(3), 169-178
Open this publication in new window or tab >>The balance between alkali diffusion and alkali consuming reactions during impregnation of softwood. Impregnation for kraft pulping revisited
2018 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, no 3, p. 169-178Article in journal (Refereed) Published
Abstract [en]

The purpose of the impregnation stage is to ensure that cooking chemicals reach all parts of the chips. However, as alkali comes into contact with wood, reactions take place, which alter the paths available for ionic transport and dissolve wood components. The aim of the present study is to establish the most favorable impregnation conditions, which result in an even alkali concentration profile through the chip at a sufficiently high level without extensive yield losses due to peeling. Softwood chips were subjected to different impregnation conditions. The progress of impregnation was assessed by analyzing the concentration of hydroxide ions in the bound liquor inside wood chips and the release of acetic acid. The extent of undesired reactions was measured as the amount of carbohydrate degradation products formed and amount of wood dissolved. Increased temperature and time lead to more degradation of the carbohydrates during impregnation. At high temperature, the concentration of alkali in the bound liquor was lower due to higher alkali consumption in degradation reactions. The most favorable process is to perform impregnation at an elevated initial effective alkali (EA) for a short time. This resulted in an increased alkali concentration in the bound liquor within the chip without extensive carbohydrate degradation.

Keywords
acetic acid; alkali consumption; alkali diffusion; analytical pyrolysis (Py-GC/MS); black liquor; bound liquor; deacetylation index; diffusion; effective alkali (EA); free liquor; impregnation parameters; kraft pulping; peeling; shrinking core model; simultaneous Py and TMAH methylation; softwood
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-33586 (URN)10.1515/hf-2017-0078 (DOI)2-s2.0-85037588364 (Scopus ID)
Available from: 2018-04-14 Created: 2018-04-14 Last updated: 2019-01-10Bibliographically approved
Brännvall, E. (2017). The limits of delignification in kraft cooking. BioResources, 12(1), 2081-2107
Open this publication in new window or tab >>The limits of delignification in kraft cooking
2017 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 1, p. 2081-2107Article in journal (Refereed) Published
Abstract [en]

The perspective of the article is to explore kraft cooking at the limits of delignification, i.e. what degree of delignification is needed to obtain fibre liberation and what is the maximum degree of delignification possible in the kraft pulping stage. The reasons for the quite narrow boundaries for sufficient and maximum delignification are explained, and the differences between the behaviour of hardwood and softwood kraft pulping are clarified.

Keywords
delignification, hardwood pulp, kraft pulping, softwood pulp
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-32966 (URN)
Available from: 2018-01-03 Created: 2018-01-03 Last updated: 2018-08-13Bibliographically approved
Brännvall, E. & Bäckström, M. (2016). Improved impregnation efficiency and pulp yield of softwood kraft pulp by high effective alkali charge in the impregnation stage. Holzforschung, 70(11), 1031-1037
Open this publication in new window or tab >>Improved impregnation efficiency and pulp yield of softwood kraft pulp by high effective alkali charge in the impregnation stage
2016 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 11, p. 1031-1037Article in journal (Refereed) Published
Abstract [en]

A pulp yield increase up to 2% can be achieved by impregnation with a liquor containing 2 M effective alkali (EA) concentration instead of 1 M. The yield increase is due to higher cellulose and glucomannan contents in the pulp, which can be rationalized by less yield loss by peeling, as impregnation is more effective at an elevated EA level. A rapid loading of chips with alkali can be realized due to a high diffusion rate. When the temperature becomes higher in the cooking stage, enough alkali is available for delignification reactions without the risk of alkali depletion in the chip core, so that the delignification is more homogeneous.

Keywords
carbohydrate composition, homogeneous delignification, impregnation, kraft pulping, pulp yield, softwood pulping
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-26206 (URN)10.1515/hf-2016-0020 (DOI)2-s2.0-84994176220 (Scopus ID)
Available from: 2016-11-25 Created: 2016-11-25 Last updated: 2019-06-14Bibliographically approved
Bäckström, M., Jensen, A. & Brännvall, E. (2016). Influence of chip presteaming conditions on kraft pulp composition and properties. Holzforschung, 70(5), 393-399
Open this publication in new window or tab >>Influence of chip presteaming conditions on kraft pulp composition and properties
2016 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 5, p. 393-399Article in journal (Refereed) Published
Abstract [en]

Presteaming is a well-established technique in pulp mills, which improves cooking liquor impregnation by removing air from within and between chips. The aim of the study was to investigate how conditions during steaming affect the subsequent kraft cook and properties of the obtained pulp. It was found that higher pressure and temperature during chip presteaming led to increased degradation and dissolution of hemicelluloses. Lower refinability and tensile index was obtained for pulps cooked after presteaming at high pressure and for a long time.

Keywords
alkali consumption, kraft cooking, presteaming, pulp properties, soft, wood, yield
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-12624 (URN)10.1515/hf-2015-0104 (DOI)2-s2.0-84967113433 (Scopus ID)
Available from: 2016-09-15 Created: 2016-09-15 Last updated: 2019-06-14Bibliographically approved
Bäckström, M., Melander, E. & Brännvall, E. (2013). Study of the influence of charges on refinability of bleached softwood kraft pulp (ed.). Nordic Pulp & Paper Research Journal (4), 588-595
Open this publication in new window or tab >>Study of the influence of charges on refinability of bleached softwood kraft pulp
2013 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, no 4, p. 588-595Article in journal (Refereed) Published
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-9768 (URN)2-s2.0-84891842664 (Scopus ID)
Available from: 2016-09-12 Created: 2016-09-12 Last updated: 2018-08-13Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8992-3623

Search in DiVA

Show all publications
v. 2.35.8