Further insight in the web consolidation process Part II. Triangular phase diagrams for analysis of paper shrinkage

A new type of triangular phase diagram has been developed in which both the volume fractions and the shrinkage modes can be visualised and compared for the consolidation process in the paper dryer. The triangular phase diagrams show the development of the solid, the liquid and the gas volume fractions as well as the shrinkage relative to either ideal or no shrinkage of the sheets. Analysis showed that for the kraft pulps the shrinkage increased continuously with decreasing moisture ratio. The shrinkage was larger than ideal shrinkage at moisture ratios below approximately 1 kg H2O/kg DS, which indicates a reduction in the gas volume in the sheets in this range of moisture ratios. The CTMP sheets showed a region of no shrinkage down to a moisture ratio of 0.6-0.8 kg H2O/kg DS followed by a region of shrinkage higher than ideal shrinkage down to totally dry sheets.