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D. Söderberg and M. Lucisano. Reduction of layer mixing in stratified forming through hydrodynamic control. In Advances in Paper Science and Technology, Trans. of the XIIIth Fund. Res. Symp. Cambridge, 2005, (S.J. I’Anson, ed.), pp 83–105, FRC, Manchester, 2018.


STFI-Packforsk has recently patented the “Aq-vanes”, a new technology for stratified forming headboxes. In this new solution, a thin passive liquid layer (a liquid vane or “Aq-vane”) is injected
in the headbox between neighbouring pulp streams through a narrow hollow channel, thereby preventing mixing between the layers.

One of the most interesting features of the Aq-vane technology is that layer purity and separation can be controlled externally by tuning a set of process parameters. This opens the field for a widespread industrial application of stratified forming, a paper maker’s quantum leap that may reduce energy and raw material consumption, lead to improved product properties and possibly even to the development of new grades. In fact, although the basic concept of producing an engineered layered structure is not new in papermaking; its application has been extremely limited to a few selected grades, such as high grammage paperboard or multi-layer tissue.

The Aq-vanes have been implemented on EuroFEX, STFI-Packforsk’s research paper machine, for extensive pilot scale trials. Thereby a number of technical solutions for the injection of the liquid layer has been tested and evaluated. In a parallel project, a method for measurement of layer purity in stratified forming has been developed. It is based on sheet splitting using a heat-seal pouch lamination technique. An image analysis method is then used to identify the colour of the fibres and thus the layer

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