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Biocarbon for fossil coal replacement
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.ORCID iD: 0000-0001-8372-4386
2018 (English)Licentiate thesis, comprehensive summary (Other academic)Alternative title
Biokol for ersättning av fossil kol (Swedish)
Abstract [en]

This research aims to provide a full view of knowledge in charcoal production for fossil coal replacement. Charcoal from biomass is a promising material to replace fossil coal, which is using as heating source or reactant in the industrial sector. Nowadays, charcoal with quality comparable to fossil coal is produced by high-temperature pyrolysis, but efficiency of the production is relatively low due to the trade-off between charcoal property and yield by pyrolysis temperature. Increasing charcoal yield by means of secondary char formation in pyrolysis of large wood particles is the primary method considering in this work. This research has explored increasing efficiency of charcoal production by bio-oil recycling and CO2 purging. These proposed techniques significantly increase concentration and extend residence time of volatiles inside particle of woodchip resulting extra charcoal. Characterization of charcoals implies negligible effect of these methods on charcoal properties such as elemental composition, heating value, morphological structure, and chemical structure. Besides, reactivity of charcoal slightly increased when these methods were applied. A numerical model of pyrolysis in a rotary kiln reactor has been developed to study the effect of design parameters and conditions in reactor scale. The simulation results showed fair prediction of temperature profiles and products distribution along the reactor length. Nonetheless, to deliver full knowledge in charcoal production, further works are planned to be done at the end of this doctoral research.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2018.
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keywords [en]
Biomass pyrolysis, charcoal, bio-oil recycling, CO2 utilization, reactivity, rotary drum
National Category
Energy Engineering Chemical Engineering Engineering and Technology
Research subject
Energy Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-71324ISBN: 978-91-7790-242-3 (print)ISBN: 978-91-7790-243-0 (electronic)OAI: oai:DiVA.org:ltu-71324DiVA, id: diva2:1258253
Presentation
2018-12-11, Lueå University of Technology, Luleå, 10:56 (English)
Opponent
Supervisors
Available from: 2018-10-25 Created: 2018-10-24 Last updated: 2019-04-03Bibliographically approved
List of papers
1. Modeling and pilot plant runs of slow biomass pyrolysis in a rotary kiln
Open this publication in new window or tab >>Modeling and pilot plant runs of slow biomass pyrolysis in a rotary kiln
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2017 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 207, p. 123-133Article in journal (Refereed) Published
Abstract [en]

Pyrolysis of biomass in a rotary kiln finds application both as an intermediate step in multistage gasification as well as a process on its own for the production of biochar. In this work, a numerical model for pyrolysis of lignocellulosic biomass in a rotary kiln is developed. The model is based on a set of conservation equations for mass and energy, combined with independent submodels for the pyrolysis reaction, heat transfer, and granular flow inside the kiln. The pyrolysis reaction is described by a two-step mechanism where biomass decays into gas, char, and tar that subsequently undergo further reactions; the heat transfer model accounts for conduction, convection and radiation inside the kiln; and the granular flow model is described by the well known Saeman model. The model is compared to experimental data obtained from a pilot scale rotary kiln pyrolyzer. In total 9 pilot plant trials at different feed flow rate and different heat supply were run. For moderate heat supplies we found good agreement between the model and the experiments while deviations were seen at high heat supply. Using the model to simulate various operation conditions reveals a strong interplay between heat transfer and granular flow which both are controlled by the kiln rotation speed. Also, the model indicates the importance of heat losses and lays the foundation for scale up calculations and process optimization.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-64494 (URN)10.1016/j.apenergy.2017.06.034 (DOI)000417229300012 ()
Conference
8th International Conference on Applied Energy (ICAE2016), Bejing, Oct 8-11, 2016
Note

Konferensartikel i tidskrift

Available from: 2017-06-26 Created: 2017-06-26 Last updated: 2018-10-24Bibliographically approved
2. Increasing efficiency of charcoal production with bio-oil recycling
Open this publication in new window or tab >>Increasing efficiency of charcoal production with bio-oil recycling
2018 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 32, no 9, p. 9650-9658Article in journal (Refereed) Published
Abstract [en]

Charcoal from biomass is a promising alternative for fossil coal. Although its quality increases at high pyrolysis temperature, charcoal yield decreases, meaning lower economic performances of charcoal production processes. This work aims at demonstrating potential methods to increase charcoal yield while keeping its quality at satisfying levels. We suggested the recycling of bio-oil from pyrolysis process as a primary measure. In addition, we also investigated in detail the consequence of utilizing CO2 instead of N2 as reaction media under practical conditions (i.e. thick particles). An experimental investigation was carried out in a macro-thermogravimetric (macro-TG) reactor. Sample (woodchips, bio-oil, and woodchips embedded with bio-oil) was exposed to the reaction temperature either instantaneously (isothermal condition) or by slow heating (slow pyrolysis) in controlled gas flows of N2 and CO2. The results showed that char yield increases with the bio-oil recycling on wood chips at all pyrolysis temperatures (300–700 °C). By 20% of bio-oil embedding on wood chips, charcoal yield increased by 18.3% on average. The increase of charcoal yield was not only because of the increase in reactants, but also due to the synergetic effect between bio-oil and wood chips upon physical contact. Bio-oil recycling had negligible effects on the property of charcoal, such as carbon content and heating value. Although CO2 did not affect primary pyrolysis, it had effects on mass transfer processes. As a result, significantly higher char yield was obtained from pyrolysis in CO2 than in N2 by ensuring a good contact of volatiles and solid surface (i.e. usage of thick particles and slow heating). This study suggests that we can achieve high charcoal yield while maintaining the similar charcoal property by bio-oil recycling, CO2 purging, use of thick particles, and slow heating.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-70583 (URN)10.1021/acs.energyfuels.8b02333 (DOI)000445711700071 ()2-s2.0-85052873835 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-15 (johcin) 

Available from: 2018-08-24 Created: 2018-08-24 Last updated: 2018-10-24Bibliographically approved

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