Further insight in the web consolidation process Part III. Modelling of paper shrinkage

A model for the web consolidation process in the paper dryer is developed and compared with experimental data for the kraft pulps. The model contains one parameter called the shrinkage factor which is used as the fitting parameter to the experimental data. The shrinkage factor can have a value between zero implying no shrinkage and a value of one which implies that all the liquid volume removed leads to shrinkage. The fitted shrinkage factor is below unity in all experiments with kraft pulps except one. This indicates that not all the removed liquid causes shrinkage. The fact that the shrinkage is higher than for ideal shrinkage (which assumes that all the water removed leads to shrinkage), can be caused by the assumption that the liquid is only located in the non-gaseous phase, and thus spreads over a smaller area than the total surface area. The results for the new model were compared with three previous models from the literature. Taking the whole range of beating degrees into account the new model showed the best agreement with the experimental data.