A Study of the Influence of Fines and Fibres Length on the Vacuum Filtration of Cellulose Fibres from Recycled Paper Ressources
Author
Sigsgaard, Maria
Term
4. term
Education
Publication year
2009
Abstract
This thesis investigates how fibre size—especially length—and fines influence vacuum filtration of cellulose pulps made from five recycled paper sources, aiming to support dewatering optimization. Fibre size distributions were measured, and pulps from newsprint were compared with printing/copy papers. Laboratory vacuum filtration tests were performed; specific filter-cake resistance was estimated from Ruth plots; the Kozeny–Carman relation was assessed; and mechanical properties of filter cakes were examined, including three-point bending, alongside variation experiments with mixed pulps. Newsprint pulps showed broader size distributions, longer filtration times, higher specific cake resistance, and lower dry-matter content than pulps from printing paper. Large standard deviations in fibre sizes made Kozeny–Carman unreliable for correlating surface area with filtrate flux; instead, a narrower fibre size distribution (typical of printing papers) was associated with faster filtration and better dewatering. Filter cakes from newsprint appeared to carry higher maximum load but were more brittle, while three-point bending showed no clear differences between paper types. Adding small fractions of another pulp (as little as 10% w/w) improved filtration time and cake dryness; a blend of 30% newsprint and 70% printing paper (mean size ~1.08 +/- 0.78 mm) delivered the best overall performance.
Dette speciale undersøger, hvordan fiberstørrelse – især længde – og fines påvirker vakuumfiltrering af cellulosepulpe fra fem forskellige genbrugte papirkilder, med fokus på at optimere afvandingen. Fiberstørrelsesfordelinger blev målt, og pulper fra avispapir blev sammenlignet med skrive- og kopipapir. Der blev gennemført laboratorieforsøg med vakuumfiltrering; den specifikke filterkagemodstand blev beregnet ud fra Ruth-plots; Kozeny–Carman-sammenhængen blev vurderet; og filterkagers mekaniske egenskaber blev testet, herunder tre-punkts bøjning, samt variationsforsøg med blandede pulper. Avispapirpulper havde bredere størrelsesfordelinger, længere filtreringstider, højere specifik filterkagemodstand og lavere tørstofindhold end pulper af kopipapir. Store standardafvigelser i fiberstørrelserne gjorde Kozeny–Carman utilstrækkelig til at korrelere overfladeareal med filtratflux; i stedet blev en smallere fiberstørrelsesfordeling (typisk for kopipapir) forbundet med hurtigere filtrering og bedre afvanding. Filterkager fra avispapir syntes at kunne bære højere maksimal last, men var mere sprøde, mens tre-punkts bøjning ikke viste tydelige forskelle mellem papirtyper. Tilsætning af små mængder af en anden pulpe (ned til 10% w/w) forbedrede filtreringstiden og tørstofindholdet; en blanding med 30% avispapir og 70% kopipapir (gennemsnitsstørrelse ca. 1.08 +/- 0.78 mm) gav den bedste samlede ydeevne.
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