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Thesis for the Degree of Master of Science

 

Year 2005
Teemu Palviainen

Wet end chemistry studies on two mechanical grade LWC machines


One of the important factors in papermaking is the chemistry in the paper machine’s approach system. The chemistry has an impact, for example, on chemical behavior and web forming, and therefore on productivity with a non-deviating quality.

The chemistries of two mechanical grade LWC machines using similar furnishes were studied using a comparative method. The aim of this study was to determine the differences in existing chemistries and the factors affecting the chemical behavior between the two machines. A comparative approach was chosen, because one of the machines has a known effective retention program and a relatively stable runnability. It was also the intention to determine why the similar chemical program is not as effective in the other machine, despite the similar furnish. The behavior of the retention chemicals at a laboratory scale was also studied in order to devise a better architecture for a more efficient chemical program.

The main factor affecting the chemical behavior in the two machines was the different bleaching method used for the mechanical pulps. The different bleaching methods were found to have a large impact on the chemistry of the pulp, thus requiring different chemistry from the fixatives.

Different coagulants have specific characteristics and influence certain pulp properties. It was possible, using a certain premix of two coagulants, to control the charge and turbidity simultaneously. These results were new and they make it possible to enhance wet end chemistry control, therefore achieving more stable runnability.


This info last modified 22 Nov 2017 by Jerri Kämpe-Hellenius