Softwood (Picea abies) sawdust was hotwater- extracted with two multi-phase processes (160- 180°C, 100-280 min, and liquor-to-wood ratio 5 l/kg) corresponding to P-factors of ~780 (yield 80.0%) and ~4580 (yield 72.4%). The pre-treated materials were then pulped with the soda-AQ cooking (170°C, NaOH charge 20%, AQ charge 0.1%, 30-150 min, and liquor-to-wood ratio 5 l/kg), resulting in a yield range of 36.1-61.4% (for reference cooks without pre-extraction 47.9-60.0%). It was observed that the pre-extraction under moderate conditions enhanced the dissolution especially of largemolar- mass lignin during cooking, and the total amount of the dissolved lignin was also higher than that removed from the material pre-extracted under harsh conditions. Additionally, in the former case the pulps with rather good properties (high yield and low amount of pulp rejects) were obtained, whereas in the latter case, a pronounced degradation of pulp carbohydrates to aliphatic acids was observed resulting in lower pulp properties.
- Aliphatic acids
- Hot-water pre-treatment
- Molar-mass distribution
- Norway spruce
Lehto, J., Alén, R., & Kleen, M. (2016). Sulfur-free pulping of hot-water-extracted spruce sawdust. Nordic Pulp and Paper Research Journal, 31(1), 41-48. https://doi.org/10.3183/NPPRJ-2016-31-01-p041-048