Refining of Fine Paper Fibres-Separate or Mixed Refinig?, 1996 Papermakers Conference Proceedings

Fine papers are typically produced from various softwood and hardwood mixtures. Long and coarse softwood fibres act as a reinforcement material whereas short and fine hardwood fibers form a good printing base. These fibers have different physical dimensions and a different refining behaviour. Long and thick softwood fibres require coarser fillings and higher refining intensity than short and thin hardwood fibers. The stronger the fibres the higher the need for the refining energy and the higher the possible energy input in each refining stage. For these reasons the most typical refining systems comprise separate refining lines for different fibers and each line has two or three refiners in series. Sometimes, however, the fibers are mixed together before refining and a mixed refining system very often comprises also two or three refiners in series. Practice has shown that both a separate and mixed refining are successfully used to produce a high quality end product. It has also shown that, in some cases, the end product quality and/or economy has been improved by rebuilding a mixed refining system into a separate refining system. In order to find out the advantages and the disadvantages of various refining systems a comprehensive study has been performed so that various softwood and hardwood fibers have been refined separately and in various mixtures. Measured fibre properties and energy consumption have indicated that some fibres are better refined separately but some fiber mixtures favour mixed refining.