Modelling the kraft pulping process on a fibre scale by considering the intrinsic heterogeneous nature of the lignocellulosic feedstock

Nicolaus Bijok*, Juha Fiskari, Richard R. Gustafson, Ville Alopaeus

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

13 Citations (Scopus)
100 Downloads (Pure)

Abstract

Renewable raw materials such as lignocellulose are inherently complex and demanding in chemical processing compared to petroleum-based feedstocks. This article addresses the challenge of developing a general model framework for modelling lignocellulosic feedstock on a fibre scale, considering its inherent heterogeneous nature in terms of the fundamental chemical component distribution in addition to its anisotropic structural properties. The presented model is tested and validated for the well-established kraft pulping process. Simulations and parameter estimation are carried out to investigate the kappa number distribution of softwood fibres during kraft pulping by using experimental data from the literature showing non-uniform delignification. A moving grid discretisation method for the distributed concentration variables is used to predict the reaction of the wood solids. The results suggest that an inherent fundamental chemical component distribution can be hypothesised as one source of the non-uniform delignification. The model indicates that a Gaussian distribution can be assumed for the initial lignin concentration within softwood. In addition, an investigation of the lignin kinetics suggests that the reactivity of lignin during kraft pulping decreases as the delignification progresses.

Original languageEnglish
Article number135548
Number of pages10
JournalChemical Engineering Journal
Volume438
Early online date8 Mar 2022
DOIs
Publication statusPublished - 15 Jun 2022
MoE publication typeA1 Journal article-refereed

Keywords

  • Chemical pulp
  • Digester
  • Distribution
  • Kappa number
  • Lignin reactivity
  • Uniformity

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