Significant dry content increase in the press section

The process of pressing paper significantly contributes to the overall energy efficiency of paper manufacturing. In order to further improve the ecological footprint of this process, there are ongoing activities to optimize the efficiency of the mechanical dewatering process, which would provide increased dryness content of the web after the press section.

Within a modern press section, a shoe press applies a pressure gradient in the z-direction, which is the driving mechanism of the mechanical dewatering. Theoretical considerations show that the dewatering efficiency can be improved with a tailor-made pressure gradient that takes the specific paper grade and boundary conditions into account. To obtain the desired pressure gradient, an optimized adjustment of the mechanical components and press fabrics is crucial, as the dynamic properties of the fabrics will considerably affect the resulting system compression behavior.

Using advanced simulation tools, laboratory experiments and pilot machine trials, we developed a novel dewatering system consisting of both mechanical components and fabrics to provide the desired pressure gradient for optimized dewatering with respect to the operating conditions of a paper machine. This was achieved through an integrated approach of mechanical and fabric development. After testing it on a small-scale pilot shoe press, the system was installed at the Smurfit Kappa Roermond mill, focusing on testliner and corrugated medium. After a successful preparation and start-up, and because of great cooperation between Voith and Smurfit Kappa, the initial results show an increase in dryness content after the press section of >1% immediately after starting the new pressing system.

In addition to the economic and ecologic benefits, implementing the novel pressing system can increase production when the dryer section is the limiting factor of the paper machine. Furthermore, the higher dryness content after the press section further increases the runability of the paper machine. These benefits can be achieved without time- and cost-intensive rebuilds, as the novel pressing system requires only minor adaptations to the shoe press roll and press fabrics, making it a very economical solution for paper manufacturers.