Open access publications in the SLU publication database

Abstract

The aim of this study was to investigate how the xylan content is changed within a wood chip and within the fiber cell walls at different positions of the chip during cooking. It was hoped that such information would give an understanding regarding the critical factors for xylan deposition within the cell wall and possible ways of affecting strength delivery of the pulp.

Two sets of cooking trials were performed; one Ref-pulp and one with beech xylan addition in the impregnation stage (10g/L). The cooks were interrupted at specific times and the chips taken out and analyzed for chemical composition and distribution of wood polymers within the chips as well as within the fiber cell walls. The pulps produced with beech-xylan addition had about 2 % higher xylan content at the end of cooking compared to the Ref-pulp.

Results indicated that the chips already contained an increased amount of xylan after 10 minutes of impregnation when beech xylan was added to the cooking liquor. However, only chips at the end of the cook showed a substantial increase in xylan sorption. During cooking, a large gradient in lignin content was noted between the surface and the inside of the chips which always showed higher lignin content even at the end of the cook. A progressive increase in xylan content was also noted in the chips as cooking proceeded. From the studies made it was not possible however, to determine if the addition of xylan led to any increased xylan content within the fibre walls. In cooks with beech xylan added during early stages, an increase in xylan was noted in the fibre lumen areas. In later stages and with increased delignification, increased xylan content was also noted between fibres in degraded middle lamellae regions.