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Author:Lindström, Mats
Title:Empirical modeling of chemical consumptions in kraft pulp bleaching
Empirisk modellering av kemikalieanvändningen vid blekning av kraft massa
Publication type:Master's thesis
Publication year:2012
Pages:103 s. + liitt. 22      Language:   eng
Department/School:Puunjalostustekniikan laitos
Main subject:Selluloosatekniikka   (Puu-23)
Supervisor:Sixta, Herbert
Instructor:Henttonen, Ville
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  2316   | Archive
Keywords:delignification
bleaching
empirical modeling
kraft massa
delignifering
blekning
empirisk modellering
Abstract (eng): The aim of this study was to investigate the opportunities for empirical modelling of oxygen delignification and ECF-bleaching of craft pulp.
Previously published results for birch, eucalyptus and southern pine were modelled with linear multivariate regression.
The outcome was ambiguous as adequate models were not obtained for all datasets.

In the modelling of oxygen delignification statistically significant models were obtained for both the keppa number and ISO-brightness.
For one dataset, the obtained brightness model predicted the delignification better than the kappa number model.
It was also shown that the HexA-free kappa number is generally a more suitable dependent than the kappa number.

In the modelling of the ECF-bleaching it was shown that satisfactory models can be obtained by utilizing initial pulp properties and chlorine dioxide charge as predictors.
The accuracy was improved if important process parameters such as D0-temperature could be incorporated.
However, none of the attempts succeeded to include oxygen or hydrogen peroxide charges in the models.
Based on the analysis of the bleaching models, it was suggested that the bleaching should preferably be modelled stage by stage, especially if it incorporates more than one bleaching chemical.

Nonlinear models were also tested, but without improving the model accuracies.
This and other problems are discussed, and further investigations are recommended.
Abstract (swe): Målet med arbetet var att undersöka möjligheterna för empirisk modellering av syre-delignifiering och ECF-blekning av kraft massa.
Publicerade delignifierings- och blekresultat för björk, eukalyptus och tall modellerades med linjär multipel regressionsanalys.
Modelleringsresultaten var blandade då all data inte resulterade i tillfredställande modeller.

För syre-delignifieringen erhölls statistiskt signifikanta modeller för både kappa nummer och blekgrad.
För eukalyptus var blekgraden lämpligare som beroende variabel än kappa nummer eller HexA -fritt kappa nummer.
Analys av modellerna visade också att HexA -fritt kappa nummer generellt är ett bättre beroende variabel än kappa nummer.

Modellering av ECF-blekningen visade att tillfredsställande modeller kan erhållas genom att inkludera variablerna blekgrad, kappa nummer och klordioxid tillsats.
Noggrannheten för modellerna förbättrades ifall det var möjligt att inkludera D0-temperaturen eller andra viktiga processparametrar.
Det var dock inte möjligt att inkludera syre eller väteperoxid tillsatser i någon av modellerna.
Baserat på analysen av modellerna rekommenderades det att blekningen borde modelleras steg före steg, i synnerhet ifall det inkluderar flera än en blekningskemikalie.

Icke-linjära modeller kontrollerades också, men utan förbättring av modellerna.
Det här och andra problem diskuterades, och rekommendationer för fortsätta studier gavs.
ED:2012-06-04
INSSI record number: 44640
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