Hydrothermal conversion of biomass

Dragan Knezevic

Research output: ThesisPhD Thesis - Research UT, graduation UTAcademic

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Abstract

This thesis presents research of hydrothermal conversion of biomass (HTC). In this process, hot compressed water (subcritical water) is used as the reaction medium. Therefore this technique is suitable for conversion of wet biomass/ waste streams. By working at high pressures, the evaporation of water and high energy consumption that it requires can be avoided. The main focus of this work was HTC process aiming at production of transportation fuel intermediates. For this study, a new experimental technique using quartz capillary batch reactors has been developed, allowing determination of the yields of gas, liquid and solid products, and their subsequent analysis. The study was performed using glucose, a biomass model compound, and complex feedstocks, wood and pyrolysis oil. Important HTC features have been studied such as, undesired char formation, deoxygenation, and mechanism and kinetics of formation of different lumped product classes. Special attention is also given to products of the initial glucose decomposition and the kinetics of their formation. Complete mass and elemental balances obtained in this work significantly complement the literature findings on the reaction mechanism of HTC. Two distinct mechanisms of char formation are identified and two mechanisms of deoxygenation (dehydration and decarboxylation) are discussed. The observed trends in the product formation rates and yields are used to obtain an engineering reaction model for decomposition of glucose, which can be adapted for the use with complex feedstocks. Finally, a bench scale continuous reactor setup for HTC is proposed and several features of the setup have been tested separately in cold-flow, such as, feeding of biomass water slurries with a piston autoclave and a lifting fluidized bed, heat transfer, fluid bed operation and state of mixing of liquid and solid phases in continuous operations.
Original languageEnglish
Awarding Institution
  • University of Twente
Supervisors/Advisors
  • van Swaaij, Willibrordus P.M., Supervisor
  • Kersten, Sascha R.A., Supervisor
Award date3 Sep 2018
Place of PublicationEnschede
Publisher
Print ISBNs978-90-365-2871-9
DOIs
Publication statusPublished - 3 Sep 2009

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Biomass
Glucose
Feedstocks
Water
Decomposition
Bioconversion
Kinetics
Autoclaves
Slurries
Batch reactors
Liquids
Dehydration
Pistons
Fluidized beds
Quartz
Wood
Evaporation
Pyrolysis
Energy utilization
Heat transfer

Keywords

  • IR-67359

Cite this

Knezevic, D. (2009). Hydrothermal conversion of biomass. Enschede: University of Twente. https://doi.org/10.3990/1.9789036528719
Knezevic, Dragan. / Hydrothermal conversion of biomass. Enschede : University of Twente, 2009. 151 p.
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Knezevic, D 2009, 'Hydrothermal conversion of biomass', University of Twente, Enschede. https://doi.org/10.3990/1.9789036528719

Hydrothermal conversion of biomass. / Knezevic, Dragan.

Enschede : University of Twente, 2009. 151 p.

Research output: ThesisPhD Thesis - Research UT, graduation UTAcademic

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AB - This thesis presents research of hydrothermal conversion of biomass (HTC). In this process, hot compressed water (subcritical water) is used as the reaction medium. Therefore this technique is suitable for conversion of wet biomass/ waste streams. By working at high pressures, the evaporation of water and high energy consumption that it requires can be avoided. The main focus of this work was HTC process aiming at production of transportation fuel intermediates. For this study, a new experimental technique using quartz capillary batch reactors has been developed, allowing determination of the yields of gas, liquid and solid products, and their subsequent analysis. The study was performed using glucose, a biomass model compound, and complex feedstocks, wood and pyrolysis oil. Important HTC features have been studied such as, undesired char formation, deoxygenation, and mechanism and kinetics of formation of different lumped product classes. Special attention is also given to products of the initial glucose decomposition and the kinetics of their formation. Complete mass and elemental balances obtained in this work significantly complement the literature findings on the reaction mechanism of HTC. Two distinct mechanisms of char formation are identified and two mechanisms of deoxygenation (dehydration and decarboxylation) are discussed. The observed trends in the product formation rates and yields are used to obtain an engineering reaction model for decomposition of glucose, which can be adapted for the use with complex feedstocks. Finally, a bench scale continuous reactor setup for HTC is proposed and several features of the setup have been tested separately in cold-flow, such as, feeding of biomass water slurries with a piston autoclave and a lifting fluidized bed, heat transfer, fluid bed operation and state of mixing of liquid and solid phases in continuous operations.

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Knezevic D. Hydrothermal conversion of biomass. Enschede: University of Twente, 2009. 151 p. https://doi.org/10.3990/1.9789036528719