Prediction of the Sheet Formation Using the Fibre Floc Evolution Model, 2008 PAPERCON Conference

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Minimizing formation, i.e. small-scale basis weight variation, is one major challenge in the papermaking process. The fibre suspension behaviour, and especially the local floc size, is, therefore an important factor in understanding the formation of the fibrous material. To examine the evolution of the local fibre floc size, the Fibre Floc Evolution (FFE) model was used in the initial drainage zone of the Fourdrinier-type of dewatering section. In the FFE model, the existence of different floc sizes is taken into account, as well as their possibility to break-up or coalesce with other flocs. In this study, the main effort was put on the flocculation modelling, and thus, the jet impingement and dewatering were considered relatively simply. Computationally predicted floc size distributions in the machine direction are given for two different jet-to-wire ratios. When comparing the effect of jet-to-wire ratio on the average floc size, it is noticed that the FFE model predicts smaller flocs for the higher shear flow (J/W =1.05) than for the lower shear (J/W =1.0). Hence, the model seems to correctly predict the floc size evolution and also the paper sheet formation, at least qualitatively, being, therefore, a promising basis to advance modelling of the paper sheet formation.