The Effect Of Felt-Web Structure Interaction On Press Dryness Variability, 19PaperCon
During pressing, batt fibres in the press felt exert a localized pressure on the wet web, the extent of which depends on the structure and geometric properties of the felt’s batt fibers and base weave but also on the structure of the wet web itself. This results in an important interaction between felt and paper web which affects press dryness, it’s variability and subsequent drying efficiency. In this work, we elucidate the interaction between felt and web structure and its effect on dryness variability through a series of laboratory trials. Oriented paper sheets, 80 gsm are pressed with two different orientations, one aligned with the felt aligned in the machine direction (MD) or with web aligned in the cross direction (CD) in order to establish different web-felt contact interactions. The wet webs are then imaged at high speed using a Near Infrared (NIR) camera simultaneously which allows moisture in the web to be visualized during drying. The average press dryness was shown to be independent of felt orientation. However, when the press felt was oriented in the CD, systematic variability in press dryness was observed and the drying time increased.
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