Canadian Forest Service Publications
Kraft pulp and paper mill utilization options for grey-stage wood. 2008. Radiotis, T.; Berry, R.; Hartley, I.; Todoruk, T Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria B.C. Mountain Pine Beetle Working Paper 2008-09. 73 p.
Available from: Pacific Forestry Centre
Catalog ID: 28782
Lodgepole pine (Pinus contorta) that is attacked and killed by mountain pine beetle (Dendroctonus ponderosae) goes through several stages (red and grey) following the attack. Wood moisture content decreases rapidly, typically to below fibre saturation point. As a consequence, the wood responds differently in both the chipping and pulping processes. Research on beetle-attacked wood has shown that many physical properties are not affected, however wood-water interactions have not been studied in detail. In the two parts of this study, we examine the sorption behaviour of beetle-killed wood in comparison to green wood; and explore the influence of utilization of dry beetle-killed wood on kraft pulping operations and pulp quality.
In the first part, it was found that the sorption of red and grey pine wood was slightly higher than of non-attacked logdepole pine for both the adsorption and desorption cases. The fibre saturation point was considerably higher for the beetle-killed wood: 0.331 for non-attacked lodgepole pine, 0.365 for red wood, and 0.394 for grey wood. The hysteresis was found to be similar over a humidity range between 20 and 80%. Based on the nuclear magnetic resonance studies, the red and grey wood had a higher T2, indicating a looser environment for the molecular motion of the water. This may be a result of the fungi changing the cell-wall structure, demonstrated by a higher fibre saturation point, as well as a higher T2 compared to non-attacked wood.
In the second part, kraft pulping of green-attack, grey and kiln-dried lodgepole pine wood was compared. The dry wood, during chipping, produced a higher proportion of fines and lower fraction of accepts than the wetter green-stage chips. Pre-treatment of the chips with a steam/soak process prior to pulping reduced screening rejects from 1 to 2% (no pre-treatment) to less than 0.5% (on oven-dried. wood basis). Green-stage chips cooked faster, had a 3-4% higher pulp yield, consumed less EA, and had a 3-point higher tear index than grey-stage or kiln-dried chips. These differences were explained through differences in wood composition and are likely caused by tree-to-tree variability rather than mountain pine beetle infestation. In LoSolids® pulping of green/dry chip mixture cooks, tear index decreased linearly by 0.03 mN m2/g for every 1% of dry chips added to the mixture. Furthermore, the liquor circulation flows decreased as the proportion of dry chips increased in the mixture cooks, a consequence of the higher pins and fines content in the dry chips. The changes in pins and fines content have the potential to affect pulping uniformity and cause screen plugging in industrial systems.