Method for Measuring Permeability of Pulp Suspension at High Basis Weights

摘要

During the formation of pulp to paper, a large amount of water is added to dilute the pulp in order to obtain a homogenous material. This water can be mechanically and/or thermodynamically removed by different process solutions. The pulp suspension flows through various process equipment that influence the pulp suspension by changing its properties before the pulp suspension finally becomes paper. It is important to understand the mechanisms behind the transport path of water in this process in order to reduce cost and to increase the production rate of pulp and paper. The resistance to flow must be known in order to describe the flow path and the corresponding pressure drop in dewatering equipment in a pulp mill. For networks with a complex geometry, a reliable method is to measure the resistance to flow at discrete points and to fit suitable resistance models to the results obtained. The objective of this study is to investigate how the history of pulp suspensions affects their permeability. A device for measuring the permeability of various pulp suspensions at high basis weights is developed and validated. Then the permeability of a number of virgin pulp species is measured. Some of the suspensions are then circulated in a closed flow loop and permeability is measured as a function of the number of loops. The results from two separate tests show that a basis weight variation and a different process treatment of the pulp suspension do not influence permeability.