Stepwise Development of a Mathematical Model for Air Flow in Vacuum Dewatering of Paper

Abstract

Part of the dewatering in a paper machine takes place via vacuum suction boxes situated below the moving web. In addition to the removal of liquid water, considerable amounts of air are sucked through the paper. The air flow that accompanies dewatering is a crucial parameter for the electricity consumption of a vacuum system. The present study models this air flow, combining differential conservation equations with fiber characterization. Measured air flow rates for different vacuum levels, basis weights, and pulp types are compared to model predictions. More than 70% of the data agree within the range of experimental error.

Keywords:

• Energy analysis
• Paper drying
• Porous media
• Transport phenomena

ACKNOWLEDGMENTS

Kamal Rezk, Jan Forsberg, and Jonas Berghel are thanked for the valuable advice and inspiration they provided throughout the course of this study.