Defibration of wood chips during delignification
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School of Chemical Engineering |
Master's thesis
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Date
2010
Department
Major/Subject
Puunjalostuksen kemia
Mcode
Puu-19
Degree programme
Language
en
Pages
iii + 65 + [3]
Series
Abstract
In this thesis work, the possibility of producing softwood craft pulp without mechanical disintegration in the fiber line was investigated. Delignification was extended in two oxygen stages to achieve normal kappa level before bleaching. Cooking chip thickness had only little impact on delignification performance. The defibration point was found at 3 hour cooking at cooking temperature 150°C and EA charge of 17.5%. Kappa number at this point was 80 and yield was 50%. A two-stage oxygen delignification was applied after the tested cooking. The results suggested that an intermediate washing was not necessary between the oxygen stages. Up to 75% of Pignin could be removed in O<sub>1</sub>/O<sub>2</sub> stages. Kappa number of 4 hour cooked pulp after O<sub>1</sub>/O<sub>2</sub> was 15. The total yield of 4 hour cooked pulp arrived at 47%. At the defibration point the value was around 48%. The rejects content after O<sub>1</sub>/O<sub>2</sub> stage was close to zero. In addition, contents of phenolic lignin in pulp samples were measured by reflectance UVNis spectrometer.Description
Supervisor
Vuorinen, TapaniThesis advisor
Engström, JohanKeywords
kraft cooking, oxygen delignification, defibration