Control of bagasse pulp quality by fractionation and refining

This study examines the possibilities of using fractionation followed by refining as a tool to improve the homogeneity of bagasse pulp quality and to overcome its drawbacks in papermaking, for instance its poor drainability. In pressure screen fractionation, long and coarse fibres go to the reject fraction, while short fibres and fines tend to be directed to the accept fraction. The reject fraction was compared to original unfractionated pulp in terms of fibres properties and the consolidation of the fibre network during filtration. The reject fraction forms a more open fibre network, reaches higher consistency faster during filtration and carries a higher structural pressure compared to the original unfractionated bagasse pulp. The reject fraction and unfractionated pulp were refined in a Voith laboratory refiner at the same refining levels. Fibres (R100) separated from the refined reject fraction were found to display greater swelling ability (measured as Fibre Saturation Point, FSP) and more external fibrillation than similar fibres separated from unfractionated refined pulp. Sheets made from the reject fraction have a higher tear index than sheets made from unfractionated pulp when compared at a certain sheet density. On the other hand, due to their lower fines content, sheets made from the reject fraction show low light scattering potential. A small amount of the accept fraction was added to softwood fibres before refining to enhance the Scott bond - light scattering combination of softwood pulp.