Sulfur-free pulping of hot-water-extracted spruce sawdust

Joni Lehto (Corresponding Author), Raimo Alén, Marjatta Kleen

Research output: Contribution to journalArticleScientificpeer-review

6 Citations (Scopus)


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.
Original languageEnglish
Pages (from-to)41-48
JournalNordic Pulp and Paper Research Journal
Issue number1
Publication statusPublished - 2016
MoE publication typeA1 Journal article-refereed


  • Aliphatic acids
  • Carbohydrates
  • Extractives
  • Hemicelluloses
  • Hot-water pre-treatment
  • Lignin
  • Molar-mass distribution
  • Norway spruce


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