Abstract
The objective for this work was to investigate the possibility to use a pressure screen equipped with a micro-perforated screen basket to produce a fine fraction from bleached chemical pulp. Trials were performed with unrefined bleached chemical hardwood pulp, and with unrefined and refined bleached chemical softwood pulp. The effect of feed concentration, feed flow, and volumetric fine fraction flow was evaluated. The difference between the fine fraction (i. e. the particles passing the screen) and the feed was analysed by studying the fibre morphology. The results showed that high feed concentration was positive for both the fine fraction concentration and the separation efficiency. A higher fine fraction concentration was also obtained when using hardwood pulp, which was explained by the shorter fibre length. Refining of the pulp prior to the fractionation proved beneficial, as a larger share of the refined pulp passed the screen, resulting in a twice as high concentration of the fine fraction when compared to unrefined pulp.
Funding statement: Financial support was received by Financial support was received by Stiftelsen för Kunskaps- och Kompetensutveckling, the Swedish Energy Agency, and the industrial partners participating in the CREPs (Production Concepts for Raw Material and Energy Efficient Products) research project at Rise: BillerudKorsnäs, Kadant NOSS, Metsä Board and Stora Enso.
Acknowledgments
The authors are grateful for the financial support from RISE Research Institutes of Sweden, The Knowledge Foundation and the companies participating in the CREPs project (Production Concepts for Raw Material and Energy Efficient Products) between 2010 and 2014. We also thank the staff at the pilot plant.
Conflict of interest: The authors declare no conflicts of interest.
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