Prediction of Paper Formation by Fluidisation and Reflocculation Experiments

Abstract

Reference geometries consisting of a constriction block and a secondary pipe were used to provide reference information for estimation of the performance of more complex geometries resembling to real headbox designs. This information included the fluidisation ability curves, i.e. the minimum attained floc size in function of mechanical energy loss, the rate of fluidisation in sudden expansion, the rate of subsequent reflocculation and the level of saturation floc size. The functionality of this approach was illustrated with measured information of a particular complex geometry on several research environments of different scale. By paper samples produced with a similar geometry, the tight connection of the fluidised state of the suspension and of the attained formation was verified. Reduction of the residence time of suspension in the headbox resulted to lower floc size in slice lip area and to better level of formation in produced paper. In addition, both properties revealed a similar form for this dependency. By changes on tensile strength ratio of the produced paper, the operation of the forming section was shown to have an apparent but not controlling effect on the level of formation obtained.