Influence on sheet dewatering by structural differences in forming fabrics
2016 (English)In: Paper Conference and Trade Show (PaperCon 2016): Proceedings of a meeting held 15-18 May 2016, Cincinnati, Ohio, USA., TAPPI Press, 2016, 767-776 p.Conference paper (Refereed)
Forming fabrics for paper manufacturing are designed with great care to enhance both process and products and are accountable for a lot of the performance of paper machines in the forming section, both with regards to energy and quality aspects. Different approaches to the design of the weave pattern and the choice of yarn materials and diameters have given the market different fabric structures. Fabric parameters that have been shown to cause differences in dewatering are caliper, void volume and permeability. To understand how the structure of the forming fabrics affects sheet dewatering selected fabrics have been tested experimentally, with dewatering equipment that simulates vacuum dewatering.
Dryness of the paper sheet was determined after dewatering and the air volume sucked through sheet and fabric was calculated. The fabrics that were chosen had similar values for all the known parameters previously shown to affect dewatering but had different structures that are defined by the open area (%) in the paper side and the wear side. Tests were performed with three fabric structures and 80 g/m2 softwood sheets. The sheets were made of both unbeaten and highly beaten pulp, and two vacuum levels were used during trials.
The results show that the fabric structure influences the sheet dewatering rate even if the caliper, void volume and permeability are the same. The air volume sucked through the structure of sheet and wire during the dewatering increased linearly with dwell time indicating that a constant air volume was reached. No significant differences were observed between the different fabrics in terms of the air volume at steady state. The conclusions are that the structure of forming fabrics affects the dewatering rate at certain conditions even with constant air volume and outgoing dryness. This is believed to be connected to (i) the fibers’ penetration of the fabric’s surface during the dewatering process or to (ii) the different resistances to in-plane and thickness- direction flow of the fabrics or to a combination of (i) and (ii). Studies of surface topography are used to explain the phenomenon and numerical simulations will be made in a later study to further evaluate this.
Place, publisher, year, edition, pages
TAPPI Press, 2016. 767-776 p.
Research subject Chemical Engineering
IdentifiersURN: urn:nbn:se:kau:diva-47597ISBN: 9781510831193 (print)OAI: oai:DiVA.org:kau-47597DiVA: diva2:1062840
Paper Conference and Trade Show (PaperCon 2016), 15-18 May 2016, Cincinnati, Ohio, USA.