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Author:Kim, DongYun
Title:Improved fiber treatment with novel refiner fillings
Publication type:Master's thesis
Publication year:2005
Pages:iii + 98 s. + liitt. 17      Language:   eng
Department/School:Puunjalostustekniikan osasto
Main subject:Paperitekniikka   (Puu-21)
Supervisor:Paulapuro, Hannu
Instructor:Koskenhely, Kari
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark TKK  646   | Archive
Keywords:refining
refiner filling
pin
homogeneity
chemical pulp
jauhatus
jauhinterät
homogeenisuus
kemiallinen massa
Abstract (eng): The purpose of this thesis was to develop chemical pulp properties more effectively by using novel refiner fillings.
To this end, two different pin fillings were compared with conventional refiner fillings in terms of gap behaviour, refined pulp properties and hand sheet properties.

It is suggested that in chemical pulp refining, fibers are treated as fiber flocs and not as individual fibers.
Under the shear forces in the grooves and the refining zone, the fiber flocs can be formed and broken up.
In refining fillings, normally the thickness of flocs is high in relation to the refiner gap, so a large amount of pulp in the form of flocs may go through the refining zone without entering between the bars.
As a result, some fibers undergo no structural changes while others lose their fiber-like shape because of the harsh treatment.
Consequently, this results in a heterogeneous refining result.

With pins in the grooves, fibers are prevented from flowing freely through the groove without any treatment.
The pins were assumed to disperse flocs by modifying the primary flow in the groove by creating speed differences in the flow, which cause additional turbulence - flock breakage - helping smaller flocs or more fibers to enter between the bars.
In addition, in the modified pin fillings the pins are installed at different heights, rising towards the outer periphery in order to reduce the back flow at the end of refining zone.

When more specific energy was applied, the gap of the reference fillings decreased, whereas the gap of the pin fillings and the modified pin fillings decreased less.
At a specific edge load of 2.5 J/m, the gap of the modified pin fillings was larger (about O.2mm) than that of the reference fillings.

At a higher SEL of 3.5 J/m and 4.5 J/m, the pulps treated with the modified pin filings retained a higher proportion of the long fiber fraction (longer than 2 mm) and a smaller amount of fines, which resulted in longer average fiber length.
At 2.5 J/m SEL, the difference between the modified pin fillings and the reference fillings in terms of the proportion of the long fiber fraction was too small to affect the average fiber length.
Similar FSP results were obtained at higher refining intensities, and somewhat lower FSP values were gained with the modified pins fillings at a SEL of 2.5 J/m.

The modified pin fillings produced higher fracture toughness and tear strength for hand sheets made from the whole pulp than the reference fillings, but they also gave slightly lower tensile strength.
For hand sheets made from the long fiber fraction (R100), no differences in these properties were noted.
These results imply that the difference in strength properties for hand sheets made from the whole pulp may arise from the different amounts of fines generated when using different fillings.

Because the modified pin fillings produce a larger amount of long fibers and consequently give longer average fiber length, also giving higher fracture toughness and tear strength, the modified pin fillings are suitable for modifying softwood Kraft pulps for use as reinforcement pulp.
ED:2005-05-12
INSSI record number: 28814
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