The effect of fines on dewatering, wet and dry web properties

Speed of paper machines is often limited by the drainage rate of the furnish and the mechanical properties of the wet web, i.e. the tension and relaxation properties. In this study, the effects of the fibre properties and fines content on dewatering, dry and wet web properties were determined. The share of long fibres decreased only slightly when the pulp was refined in the Valley beater. More fibre cutting occurred during refining in the ProLab refiner. Tests showed that refining of pulp from SR20 to SR30 and SR70 using a Valley beater or a ProLab refiner increased the dewatering time. The wet and dry tensile strength as well as the residual tension of the wet web at 2% strain also increased. Removal of fines shortened the dewatering time and decreased the wet and dry tensile strength, and the residual tension compared to pulps containing fines. Addition of fines increased the dewatering time as well as the dry and wet tensile strength. The fibre properties affected the residual tension more than the fines content, while the fines content was more important for the wet tensile strength.