Rate-limiting Mechanisms of Water Removal during the Formation, Vacuum Dewatering, and Wet-pressing of Paper Webs: A Review

Martin A. Hubbe, Björn Sjöstrand, Lars Nilsson, Antti Koponen, J. David McDonald

Abstract


Because some of the critical events during the removal of water before the dryer section on a paper machine happen very rapidly within enclosed spaces – such as wet-press nips – there have been persistent challenges in understanding the governing mechanisms. In principle, a fuller understanding of the controlling mechanisms, based on evidence, should permit progress in achieving both higher rates of production of paper and more reliable control of paper attributes. In addition, energy can be saved, reducing environmental impacts. The goal of this article is to review published work dealing both with the concepts involved in water removal and evidence upon which existing and new theories can be based. The scope of this review includes all of the papermaking unit operations between the jet coming from the headbox and the final wet-press nip of an industrial-scale paper machine. Published findings support a hypothesis that dewatering rates can be decreased by densification of surface layers, plugging of drainage channels by fines, sealing effects, flocculation, and rewetting. Ways to overcome such effects are also reviewed.

Keywords


Drainage rate; Hydrofoil; Vacuum flatbox; Couch roll; Press felt; Extended-nip press

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Welcome to BioResources! This online, peer-reviewed journal is devoted to the science and engineering of biomaterials and chemicals from lignocellulosic sources for new end uses and new capabilities. The editors of BioResources would be very happy to assist you during the process of submitting or reviewing articles. Please note that logging in is required in order to submit or review articles. Martin A. Hubbe, (919) 513-3022, hubbe@ncsu.edu; Lucian A. Lucia, (919) 515-7707, lucia-bioresources@ncsu.edu URLs: bioresourcesjournal.com; http://ncsu.edu/bioresources ISSN: 1930-2126