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Title
Kraft pulping combined with green liquor pre-extraction of beech wood
Authors
MARIA FISEROVA ELENA OPALENA and MARTA MAHOLANYIOVA
Received
September 17, 2012
Published
Volume 47 Issue 7-8 July-August
Keywords
beech wood, pre-extraction, hemicelluloses, kraft pulping, viscosity, strength properties
Abstract
Beech wood chips were extracted with green kraft liquor at different alkali charges of 1, 2, 3 and 4% on dry wood mass
and with hot water. The extractions were performed at 160 °C and different time to achieve 10% wood mass loss. The
total content of monosugars in hydrolysed extracts decreased with increasing green liquor charge, but lignin and
insoluble solids content increased. The kraft pulp yields from pre-extracted chips with 2, 3 and 4% green liquor charge
were similar with those from original wood chips. Effective alkali charges in the pulping process were about 1% to
3.5% lower than in control kraft pulping and reduced with increasing green liquor charge in the extraction process. The
addition of AQ in the extraction or pulping process increased pulp yield, especially in extraction. Limiting viscosity
numbers of the pulps from chips pre-extracted with green liquor were slightly higher than those of control kraft pulps.
Tensile, burst and tear strength of the pulp handsheets from chips pre-extracted with 2, 3 and 4% green liquor charge
were the same as or slightly higher than those for original wood chips. The optimal green liquor charge in the extraction
process was 2% or 3%, in terms of extraction and pulping process effectiveness.
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