Experiments and Modeling of Pulp Mat Formation

Abstract

<p>In this dissertation, new insights into dispersed air, surfactant and defoamer effects on pulp mat formation in brownstock washing are described based on extensive experimental research. Observations of bubble behavior and channel formation are used to explain the relationship between the presence of dispersed air and the resulting low water drainage rates from the pulp pad. The work provides new understanding of the mechanism of dispersed air effect on pulp washing.</p> <p>A new pulp mat water permeability model is also included in this dissertation. The model covers a wider pulp fiber concentration range than previous models in literature.</p> <p>A systematic experimental investigation of pulp mat formation from dilute suspensions provides concentration profiles and mat thickness as a function of time. Dynamic fiber concentration profiles along the mat formation direction were inferred from standard images using a grayscale analysis calibrated against a set of known concentrations. A modified semi-empirical filtration model, based on the work of Tiller et al, was applied to compressible porous pulp fiber mat formation, and fits the experimental results very well. With this newly developed model, it is easy to calculate the capacity of a pulp washer at varied operating conditions. This model can be used for process optimization and control and make it possible to further improve the pulp washer efficiency.</p>