Author(s):
Margarido, M. 
; Anjos, O. ; Silva Perez, P. ; Mortha, G.
Date: 2010
Persistent ID: http://hdl.handle.net/10400.11/1973
Origin: Repositório Científico do Instituto Politécnico de Castelo Branco
Subject(s): Kraft cooking; Softwoods; Lignin content; Polysaccharides content; Hexenuronic acids
Description
The main goal of this paper is to observe de differences of behaviour between six softwoods species
during the kraft cooking sequence, knowing that morphological, physicochemical and hygroscopic
characters are different. Six wood species (Scots pine, maritime pine, Aleppo pine, black pine,
Douglas fir and Spruce) were analysed separately.
Different parameters were evaluated (Lignin content, Polysaccharides content (cellulose and
hemicelluloses), Yield, Hexenuronic acids) and for each wood species three temperatures (150ºC,
160ºC and 170ºC) and different cooking times, allowing to study the behaviour of the wood species.
Common cooking conditions were applied and temperature program included cold impregnation, a
plateau at 110°C during 2.5 hours to perform initial delignification separately followed by a second
plateau at cooking temperature. Non-uniform cooking behaviour was observed; chestnut and oak
trees consumed much more caustic soda and had a lower yield in the initial phase of the cook. It was
possible conclude that in a genera way, the behaviour of the six softwoods is highly homogeneous, for
the three temperatures studied.
Data analysis was made with Principal component analysis (PCA) and ANOVA. The results of PCA
show that all parameters: Yield (Y), Klason lignin (L), cellulose content (C), and effective residual alkali
(EA) are well correlated. The cellulose content was negatively correlated with the other factors. The
hexenuronic acids (HA) and hemicelluloses content was well correlated witch other. The coking time in
the 2nd plateau influence all factors. Moreover, the three different temperatures are very similar they
present statically differences with Tukey’s test (P<0.05). For the highest cooking time all parameter
present lower values. The time on the 2nd plateau do not influence the yield and the delignification.
