Modelling and simulation of biorefinery processes Case study: Kraft pulping process

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School of Chemical Technology | Doctoral thesis (article-based) | Defence date: 2024-08-23
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Authors

Date

2024

Department

Kemian tekniikan ja metallurgian laitos
Department of Chemical and Metallurgical Engineering

Major/Subject

Mcode

Degree programme

Language

en

Pages

73 + app. 45

Series

Aalto University publication series DOCTORAL THESES, 144/2024

Abstract

In the pursuit of a sustainable economy, the transition from petroleum-based to renewable feedstocks like lignocellulose demands a profound understanding of its inherent complex character during chemical processing. However, established modelling approaches for the kraft pulping process omit certain aspects of the hierarchical complexity of the feedstocks in use. Hence, these models must be revisited and gradually substituted by more rigorous approaches that capture the variability across multiple scales. They often overlook the intrinsic variability in feedstock properties, such as chemical composition. While some models exist, they typically focus on predicting average behaviour, e.g., the resulting pulp's kappa number, neglecting the distributed nature of initially presented chemical components within the wood and differences in its fragmentation kinetics. This work proposes novel modelling frameworks to address these limitations, introducing the concept of the distributed character for the chemical components within wood chips and investigating the resulting non-uniform delignification at a fibre level regarding individual fibre kappa number distribution. Furthermore, the frameworks incorporate the threedimensional properties of the anisotropic raw material structure and distinguish between different regions within the wood chip, e.g. early- and latewood regions. Resulting of adjustments regarding the kinetics of the well-established Purdue kraft pulping kinetics, a new kinetic model was developed, considering the heterogeneous nature of the lignin macromolecule with its diverse structures on a monolignol resolution using a graph and network structure, which allows a deeper understanding of the processes during fragmentation. Ultimately, this research aims to contribute to developing more efficient and targetoriented processes for producing bioenergy and biomaterials. Leveraging advanced modelling techniques and discussing the modelling results in the context of recent experimental findings offers insights that can help in decision-making and drive the transition towards a more sustainable future.

Description

Supervising professor

Alopaeus, Ville, Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland

Thesis advisor

Jakobsson, Kaj, D.Sc., Aalto University, Department of Chemical and Metallurgical Engineering, Finland

Keywords

kraft pulping, multiscale modelling, kinetics, distribution, lignocellulose

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Parts

  • [Publication 1]: Bijok, Nicolaus; Fiskari, Juha; Gustafson, Richard R., Alopaeus, Ville. Modelling the kraft pulping process on a fibre scale by considering the intrinsic heterogeneous nature of the lignocellulosic feedstock. Elsevier. Chemical Engineering Journal, volume 438 (2022), page 135548. ISSN 1873-3212.
    Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202203282669
    DOI: 10.1016/j.cej.2022.135548 View at publisher
  • [Publication 2]: Bijok, Nicolaus; Fiskari, Juha; Gustafson, Richard R., Alopaeus, Ville. Chip scale modelling of the kraft pulping process by considering the heterogeneous nature of the lignocellulosic feedstock. Elsevier. Chemical Engineering Research and Design, volume 193 (2023), page 13-27. ISSN 0263-8762.
    Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202304052687
    DOI: 10.1016/j.cherd.2023.03.010 View at publisher
  • [Publication 3]: Bijok, Nicolaus; Alopaeus, Ville. Modelling the fragmentation kinetics of the heterogeneous lignin macromolecule during kraft pulping with stochastic graphs. Elsevier. Chemical Engineering Journal, volume 477 (2023), page 146964, ISSN 1385-8947.
    Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202312117227
    DOI: 10.1016/j.cej.2023.146964 View at publisher

Citation

Permanent link to this item

https://urn.fi/URN:ISBN:978-952-64-1923-7

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[diss] Kemian tekniikan korkeakoulu / CHEM