High kappa refining and its effect on drainability and the technical properties of paper
Kauppinen, Juha (2019)
2019
Materials Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2019-05-27
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201905311826
https://urn.fi/URN:NBN:fi:tty-201905311826
Tiivistelmä
High kappa pulp is used for the production of kraftliner. The high kappa pulp has also a high lignin content where the kappa number is between 80 and 100. At high kappa, rigid fibers are obtained to achieve that brings the required properties of the packaging, such as compression resistance. The high kappa number also provides a better yield, which has led to an increase in the production of kraftliner in the pulp industry.
Higher lignin content also causes problems because the lignin binds the bundles of fibers to each other, so the fiber suspension also has a high shives concentration. In addition, the high lignin content also affects the drainability of the fiber suspension, drainability is an important parameter of the washing stage. Because the stiffness decreases as the refining increases, the high kappa pulp is only mildly refined to avoid losing good stiffness properties. However, other strength properties are improved as shape of the fibers are changed for example, the length and the width of the fibers. Also the binding ability improves.
The target of this thesis was to study high kappa pulp refining. In this experiment, the focus was on a change in pulp properties over the refiner. During this study, the pulp samples were obtained from two different pulp mills. During the trials the specific energy consumption, consistency of the blow refiners and the kappa number were changed. The samples from both mills were analyzed: the drainability, the shive content, the kappa number and the fiber properties were measured. After the measurements, the pulp samples were refined, hand sheets were made, and the paper´s technical measurements were performed in laboratory.
As a result of the defibration, the shive content and drainability of the pulp decreased. Raising the kappa level during the tblow refining did not significantly affect the pulp drainability. The shive content affected the specific energy consumption in the post-refining, i.e. a higher shive content and the kappa number increased the required specific energy consumption in order to reach the desired refining level. The pulp from the samples were subjected to post-refining and the higher refining level had better strength properties. The results from the sheets (100 g/m2) show that as the lignin content increased the densities of the sheets diminished and the air permeability also increased.
Higher lignin content also causes problems because the lignin binds the bundles of fibers to each other, so the fiber suspension also has a high shives concentration. In addition, the high lignin content also affects the drainability of the fiber suspension, drainability is an important parameter of the washing stage. Because the stiffness decreases as the refining increases, the high kappa pulp is only mildly refined to avoid losing good stiffness properties. However, other strength properties are improved as shape of the fibers are changed for example, the length and the width of the fibers. Also the binding ability improves.
The target of this thesis was to study high kappa pulp refining. In this experiment, the focus was on a change in pulp properties over the refiner. During this study, the pulp samples were obtained from two different pulp mills. During the trials the specific energy consumption, consistency of the blow refiners and the kappa number were changed. The samples from both mills were analyzed: the drainability, the shive content, the kappa number and the fiber properties were measured. After the measurements, the pulp samples were refined, hand sheets were made, and the paper´s technical measurements were performed in laboratory.
As a result of the defibration, the shive content and drainability of the pulp decreased. Raising the kappa level during the tblow refining did not significantly affect the pulp drainability. The shive content affected the specific energy consumption in the post-refining, i.e. a higher shive content and the kappa number increased the required specific energy consumption in order to reach the desired refining level. The pulp from the samples were subjected to post-refining and the higher refining level had better strength properties. The results from the sheets (100 g/m2) show that as the lignin content increased the densities of the sheets diminished and the air permeability also increased.