In the first part of this paper (by E. Back) the fundamentals of press-drying are reviewed. Effects of process variables in single stage press-drying promoting the flow of wood components (especially lignin) under heat, moisture, and pressure are illustrated. For press-drying of hardwood pulps the role of residual lignin in parenchyma cells, with delayed removal in pulping, is analysed. The possibilities of short, multiple-stage press nips as useful for continuous paper production are exemplified.
In the second part (by R. Swenson) the application of the press-drying process is discussed for different paper grades. Various pilot plant approaches to dynamic, i.e. continuous, press drying are shown. The variables which affect the product and process are presented, with the results obtained when going from static press-drying to a dynamic slow speed press-drying machine. The problems of high speed press-drying to a paper machine is shown.