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Fundamental understanding of removal of liquid thin film trapped between fibers in the paper drying process: A microscopic approach, TAPPI Journal May 2020
ABSTRACT: In the fabrication of paper, a slurry with cellulose fibers and other matter is drained, pressed, and dried. The latter step requires considerable energy consumption. In the structure of wet paper, there are two different types of water: free water and bound water. Free water can be removed most effectively. However, removing bound water consumes a large portion of energy during the process. The focus of this paper is on the intermediate stage of the drying process, from free water toward bound water where the remaining free water is present on the surfaces of the fibers in the form of a liquid film. For simplicity, the drying process considered in this study corresponds to pure convective drying through the paper sheet. The physics of removing a thin liquid film trapped between fibers in the paper drying process is explored. The film is assumed to be incompressible, viscous, and subject to evaporation, thermocapillarity, and surface tension. By using a volume of fluid (VOF) model, the effect of the previously mentioned parameters on drying behavior of the thin film is investigated.
Journal articles
Magazine articles
´We Must Grow—In All Areas’, Paper360º May/June 2020
´We Must Grow—In All Areas’, Paper360º May/June 2020
Journal articles
Magazine articles
Wireless Sensors Improve Toxic Gas Mitigation in P&P Mills, Paper360º May/June 2020
Wireless Sensors Improve Toxic Gas Mitigation in P&P Mills, Paper360º May/June 2020
Journal articles
Magazine articles
TAPPI Journal Summaries, Paper360º May/June 2020
TAPPI Journal Summaries, Paper360º May/June 2020
Journal articles
Magazine articles
How Strikes, Regulations and Disasters Impact Pulp and Paper Supply Chains, Paper360º May/June 2020
How Strikes, Regulations and Disasters Impact Pulp and Paper Supply Chains, Paper360º May/June 2020
Journal articles
Magazine articles
Human Capital: The New Metric to Measure, Paper360º May/June 2020
Human Capital: The New Metric to Measure, Paper360º May/June 2020
Journal articles
Magazine articles
COVID-19 Has Created New Opportunities for Tissue and Towel, Paper360º January/February 2021
COVID-19 Has Created New Opportunities for Tissue and Towel, Paper360º January/February 2021
Journal articles
Magazine articles
Smart and Resource-Efficient: The DNA of the Paper Industry, Paper360º July/August 2021
Smart and Resource-Efficient: The DNA of the Paper Industry, Paper360º July/August 2021
Journal articles
Magazine articles
TAPPIConLive! New Technology Showcase Previews, Paper360º July/August 2021
TAPPIConLive! New Technology Showcase Previews, Paper360º July/August 2021
Journal articles
Magazine articles
A guide to eliminating baggy webs, TAPPI Journal June 2021
ABSTRACT: Slack or baggy webs can cause misregistration, wrinkles, and breaks in printing and converting operations. Bagginess appears as non-uniform tautness in the cross direction (CD) of a paper web. The underlying cause is uneven CD tension profiles, for which there are few remedies once the paper is made. Precision measurements of CD tension profiles combined with trials on commercial paper machines have shown that uniform CD distribution of moisture, basis weight, and caliper profiles at the reel are key to avoiding bagginess. However, the most important but infrequently measured factor is the CD moisture profile entering the dryer section. Wetter areas entering the dryers are permanently elongated more than dry areas, leading to greater slackness in the finished paper. In storage, wound-in tension can amplify baggy streaks in paper near the surface of a roll and adjacent to the core. Unwrapped or poorly wrapped rolls exposed to low humidity environments may have baggy centers caused by moisture loss from the roll edges.All of the factors that impact bagginess have been incorporated in a mathematical model that was used to interpret the observations from commercial trials and can be used as a guide to solve future problems.