Effect of Kraft Cooking Conditions on the Chemical Composition of the Surface and Bulk of Spruce Fibers

Abstract

Journal of Wood Chemistry and TechnologyPublication details, including instructions for authors and subscription information: Abstract: By varying cooking temperature, alkali charge, ionic strength, and cooking time in Kraft pulping of spruce chips, pulps ranging between kappa numbers 20-80 were obtained. The unbleached Kraft pulp fibers were subjected to mechanical peeling in order to separate the surface material from the bulk of the fibers and the carbohydrate composition and lignin content of the two fractions were analyzed. As expected, the lignin and xylan contents were higher on the fiber surface than in the fiber wall. The percentage of xylan on the fiber surface was fairly constant, independent of different pulping conditions or degree of delignification. The lignin proportion on the fiber surface gradually decreased with decreasing kappa number. At a given kappa number, pulping at a higher temperature resulted in less lignin on the fiber surface, probably because of the higher solubility of lignin at higher temperature. Cooking at lower alkali charge also resulted in lower lignin content on the fiber surface at a given kappa number. In this case, there was more time available for degradation of the surface lignin since the lower alkali charge resulted in longer cooking time needed to reach a certain kappa number.

Micro/nano-structural evolution in spruce wood during soda pulping

“…This requires a better knowledge regarding different process steps in a pulp mill and how these influence the main product, the paper pulp. The most important operation in the paper pulp process is the pulping, where the partial fragmentation and dissolution of lignin and hemicelluloses takes place and the individual fibers are liberated from the wood matrix (Gellerstedt 2009;Gierer 1980;Gustafson et al 1983;Jansson and Brännvall 2014;Kwasniewski and Theliander 2001). It is, therefore, of no surprise that a vast number of publications elaborating on the main reaction pathways involved in this operation and the final fiber properties as functions of process conditions can be found in the literature (e.g.…”

High-alkali low-temperature polysulfide pulping (HALT) of Scots pine

“…In a highly diluted pulping system, it was demonstrated that, without any clear indication of redeposition to the fibre wall, during extended pulping, the decrease in the dissolved AX fraction was coupled with a parallel increase in the detected BL hydroxy acid amount (Paananen et al, 2013). Conversely, at industrial liquor-to-wood ratios around 4-6, xylan in particular is shown to redeposit on fibre surfaces (Li Jansson and Brännvall, 2014) and also locate on the outer fibre wall after pulping (Vaaler, 2008). Therefore, it seems that certain AX adsorption occurred during pulping at 60% EA charge, but not until the point of fibre liberation and dissolution of the middle lamella lignin at around K-60.…”

Pembuatan Pulp Untuk Kertas Bungkus Dari Bahan Serat Alternatif

“…Kadar alfa-selulosa dan holoselulosa tertinggi adalah pada serat daun nenas, sedangkan terendah pada kayu terentang. Bahan serat dengan kadar alfa-selulosa dan holoselulosa tertinggi sekiranya diolah menjadi pulp berpengaruh positif terhadap rendemen pulp (Sjostrom, 1994;Jansson & Brannvall, 2013).…”