Propapier starts new type of hard nip sizer from Valmet

A new type of sizer, called Opti- Sizer Hard, and the related chemical systems were successfully started up by Finland’s Valmet on PM1 at Propapier AG’s Burg mill in Germany, on April 19, 2018, a day ahead of schedule. PM1 produces liner, fluting and kraft substitute grades from 100% waste paper. All the containerboard produced was saleable from the very start.

A prototype product and a very tight shut-down schedule was a challenging combination but despite the initial setup, most of the targets were achieved right after the start-up. The web passed through the nip smoothly and runnability was excellent. The new technology shows its potential to achieve the goals regarding strength properties and steam consumption.

Compared to a conventional sizer, an OptiSizer Hard has a pair of hard cover nip rolls. Starch is sprayed on the rolls which transfer the starch into the nip where it is further transferred into the paper web.

Valmet says that strength is among the most important benefits with OptiSizer Hard. Starch is dosed in the roll nip with higher nip pressure which increases the density of fibres leading to better strength properties. As well, the life cycle costs are lower because of the spray application and better nip profile control means runnability is better.

The existing starch preparation system was replaced with Valmet’s system specially designed for OptiSizer Hard and its spray application method. The properties of the produced starch have a substantially lower range of variation which helps to produce liner boards within the targeted quality specifications. The supply system is fully automated and equipped with pressure screens.

To further improve the properties of liner and fluting grades Propapier and Valmet signed a 20-week cooperation agreement. The aim is to find the best practices with the new sizer such as reducing energy consumption and further improving liner and fluting properties – e.g. the lighter basis weight of containerboards — without compromising other important properties.


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