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Author:Ahonen, Joni
Title:Taivekartongin runkokerroksen massakoostumuksen optimointi
The optimisation of middle layer pulp composition of folding boxboard
Publication type:Master's thesis
Publication year:2014
Pages:81 s. + liitt. 2      Language:   fin
Department/School:Puunjalostustekniikan laitos
Main subject:Paperi- ja painatustekniikka   (P3003)
Supervisor:Paltakari, Jouni
Instructor:Aronen, Antti
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201404161684
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Location:P1 Ark Aalto  2214   | Archive
Keywords:folding boxboard
middle layer
z-directional strength
broke
taivekartonki
runkokerros
palstautumislujuus
BCTMP
hylkymassa
Abstract (eng):The aim of this master's thesis was to determine the optimum pulp composition for the middle layer of folding boxboard in a situation where the amount of broke was limited.
The limited availability of broke is a result of improved production efficiency and runnability of the board machine.
According to previous calculations, there would be approximately 10 to 15 % less of broke available in the near future.
And this has to be replaced with the same amount of BCTMP.

In the literature part of this study, the most important demands for folding boxboard are covered.
Z-directional strength and the affecting factors are examined more thoroughly.
As well as fibre network formation.
In addition the differences of pulp manufacturing methods and properties of different middle layer pulp components are studied.

The experimental part concentrates in the middle layer pulp composition.
It consists of five production scale test runs, which were carried out with different board grades (SC215, SC230, SC255, SC265 and SC295).
During the test runs, the affects of lowering the amount of broke in the middle layer were examined.
The implementation of the test runs proved to be challenging, within the given time period, due to problems with consistency of production and board quality.

As expected, when lowering the amount of broke in the middle layer, the major limiting factor was z-directional strength of the board.
Less expected were the sudden drops in z-directional strength and surface strength (IGT), that made lowering of the broke amount more difficult.
In addition some substantial differences in the strength values in the cross direction of the board machine appeared during the test runs.
This made the interpretation of the results a bit more challenging.

According to the results of the test runs, it seems to be possible to lower the amount of broke to some extent with all produced board grades.
The best potential is with the board grades in the middle of the basis weight range.
For the lightest grades, z-strength is already much lower, which means that the amount of broke cannot be lowered much more.
The z-strengths of the heavier grades are higher on average.
In practice, however, the heavier are the most problematic, due to the sudden drops and changes in z-directional strength properties.

During the spring of 2013, a substantial investment was made in broke refining, which increased the power of the individual refiners as well as the total capacity of broke refining.
With increased refining power the z-strength of the middle layer was improved and as a result the total amount of broke was lowered.
Abstract (fin):Diplomityön tavoitteena oli määrittää taivekartongin runkokerroksen optimaaliset massasuhteet eri kartonkilajeille uudessa tilanteessa, jossa hylkymassan käyttöä on rajoitettava.
Taustalla on kartonkikoneen tuotannon ja ajettavuuden paranemisen myötä heikentynyt hylyn saatavuus.
Laskelmien mukaan hylyn annostelua tulisi saada laskettua noin 10 -15 prosenttiyksikköä.
Vähentynyt hylyn osuus korvataan BCTMP:llä.

Työn kirjallisuusosassa selvitettiin yleisesti tärkeimmät taivekartongilta vaaditut ominaisuudet.
Tarkemmin perehdyttiin erityisesti kartongin paksuussuuntaiseen lujuuteen ja kuituverkoston muodostumiseen sekä niihin vaikuttaviin muuttujiin.
Lisäksi selvitettiin erilaisten massanvalmistusmenetelmien ja runkomassakomponenttien ominaisuuksia ja eroja.

Kokeellisessa osassa tutkittiin runkomassakoeajojen avulla mahdollisuuksia vähentää hylkymassan käyttöä sekä selvitettiin alhaisemman hylkyosuuden vaikutukset kartongin ominaisuuksiin.
Työlle varatun ajan puitteissa onnistuttiin suorittamaan koeajot viidellä eri kartonkilajilla (SC215, SC230, SC255, SC265 ja SC295).
Koeajojen suorittaminen osoittautui haasteelliseksi tuotannon ja laadun tasaisuuteen liittyvien ongelmien vuoksi.

Hylyn osuutta pienennettäessä kriittisimmäksi tekijäksi muodostui odotetusti runkokerroksen palstautumislujuuden heikkeneminen.
Myös palstautumislujuuden ja IGT-pintalujuuden nopeat romahdukset sekä radan poikkisuuntaiset vaihtelut rajoittivat hylyn osuuden pienentämistä.
Lisäksi yllättävät romahdukset vaikeuttivat tulosten tulkitsemista ja johtopäätösten tekemistä.

Koeajojen perusteella hylyn osuutta voidaan jonkin verran pienentää kaikilla kartonkilajeilla.
Suurin vähennyspotentiaali lienee keskiraskailla lajeilla.
Keveimmillä lajeilla jo lähtökohtainen palstautumislujuustaso on alhainen, mikä rajoittaa hylyn osuuden laskemista.
Raskaimmilla lajeilla hylyn osuutta voitaisiin puhtaasti palstautumislujuuksien perusteella pienentää huomattavasti.
Käytännössä se on kuitenkin hankalaa, erityisesti palstautumis- ja pintalujuuksien yllättävien heilahdusten ja poikkisuuntaisten profiiliongelmien vuoksi.

Keväällä kartonkikoneelle tehdyssä jauhatusinvestoinnissa hylkyjauhinten tehoja ja kapasiteettia nostettiin merkittävästi.
Investoinnin jälkeen runkokerroksen lujuus parantui selvästi, minkä ansiosta hylyn kokonaisosuutta voitiin pienentää ja runkosellun annostelu lopettaa.
ED:2014-06-18
INSSI record number: 49319
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