Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Role of surface morphology in bed particle layer formation on quartz bed particles in fluidized bed combustion of woody biomass
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.ORCID iD: 0000-0003-1203-0410
Department of Applied Physics and Electronics, Umeå University, SE-90187 Umeå, Sweden.ORCID iD: 0000-0002-5777-9241
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0001-7395-3302
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
Show others and affiliations
2024 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 357, no part A, article id 129702Article in journal (Refereed) Published
Abstract [en]

The influence of quartz bed particle surface morphology on the bed particle layer and crack layer formation process in fluidized bed combustion of woody biomass was investigated in this work. Bed material samples were collected at different sampling times from the startup with a fresh bed in industrial scale bubbling fluidized bed (BFB) and circulating fluidized bed (CFB) boilers, both utilizing woody biomass. X-ray microtomography (XMT) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) were employed to characterize bed particle layers and crack layers in the samples. Results showed that there is a noticeable difference between the bed layer characteristics over the so-called “concave” and “convex”-shaped morphologies on the bed particle surface with respect to layer formation. The concave areas are mainly covered with a thin inner layer, whilst the convex display a comparably thick inner layer and an outer layer. In addition, 3D images of the particles revealed that the crack layers mainly originate from concave areas where the particle is less protected by an outer bed particle layer in conjunction with cracks in the inner layer.

Place, publisher, year, edition, pages
Elsevier Ltd , 2024. Vol. 357, no part A, article id 129702
Keywords [en]
Bed material, Industrial-scale, Time-resolved, X-ray tomography
National Category
Energy Engineering
Research subject
Energy Engineering; Experimental Mechanics; Fluid Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-101365DOI: 10.1016/j.fuel.2023.129702ISI: 001070700200001Scopus ID: 2-s2.0-85170026881OAI: oai:DiVA.org:ltu-101365DiVA, id: diva2:1797933
Funder
Swedish Energy Agency, no. 46533-1
Note

Validerad;2023;Nivå 2;2023-09-18 (joosat);

CC BY 4.0 License;

For correction, see: Valizadeh A., Skoglund N., Forsberg F., Lycksam H., Öhman M., (2024). Corrigendum to “Role of surface morphology in bed particle layer formation on quartz bed particles in fluidized bed combustion of woody biomass” [Fuel 357(Part A) (2024) 129702]. Fuel. 364 131320. doi https://doi.org/10.1016/j.fuel.2024.131320

Available from: 2023-09-18 Created: 2023-09-18 Last updated: 2024-04-19Bibliographically approved
In thesis
1. Role of Surface Morphology on Bed Particle Layer Formation During Thermal Conversion of Woody Biomass in Fluidized Beds
Open this publication in new window or tab >>Role of Surface Morphology on Bed Particle Layer Formation During Thermal Conversion of Woody Biomass in Fluidized Beds
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bed particle layer formation is a crucial aspect of fluidized bed conversion of woody biomass, which can positively and negatively impact the process performance. The layer formation may lead to issues such as bed agglomeration and bed material deposition or reduced oxygen transport capacity of oxygen carriers. However, bed layer formation may positively affect the product gas composition in gasification. While extensive research has been conducted on the interactions between the ash-forming constituents from various wood-derived fuels and different bed materials, the influence of the bed particle surface properties on the bed layer characteristics remains largely unexplored in the existing literature.

This thesis thoroughly studied the role of bed particle surface morphology on the bed layer formation and its characteristics across different bed particle types within various fluidized bed conversion processes of woody biomass. The bed particle samples were collected from different bench-scale, semi-industrialscale, and industrial-scale conversion units at different time intervals from the start-up to assess the bed particle layer formation process throughout the bed particle age in different conversion processes of woody biomass. Natural sand bed samples (consisting mainly of quartz and K-feldspar) were taken from a 30 MWth bubbling fluidized bed (BFB30) combustion unit and a 90 MWth circulating fluidized bed (CFB90) combustion unit. K-feldspar and olivine were obtained from a dual fluidized bed (DFB12-4) indirect gasification unit comprising a 12 MWth circulating fluidized bed combustor and a 2-4 MWth bubbling fluidized bed gasifier. Different types of ilmenite samples were taken from a 5 kWth bench-scale bubbling fluidized bed (BFB5) and a 12 MWth circulating fluidized bed (CFB12) combustion unit. Additionally, quartz and natural sand samples (comprising mainly quartz, K-feldspar, and Na-feldspar) were gathered from three different industrial fast pyrolysis plants. Bed particles found in the samples were subjected to different analysis methods. Scanning electron microscopy (SEM), coupled with energy dispersive spectroscopy (EDS), served as a primary tool for obtaining information regarding the morphology and elemental composition of different layers present on the surface of bed particles and inside the bed particle core. In instances where layers were too thin to be adequately examined via SEM/EDS, transmission electron microscopy (TEM) was employed as a complementary analysis method. X-ray microtomography (XMT) was also utilized to explore the distribution of bed particle layers on the particle surfaces. This method facilitated both qualitative and quantitative assessments, including observation of the surface morphology of the bed particles, analysis of the bed layer distribution on the bed particle surface, along with measurements of bed particle layer thickness and the volume fraction of various features throughout the bed particles.

Comprehensive analysis of the results from different characterization techniques showed that for all studied bed particles, regardless of their chemical composition, the inner layer (i.e., the Ca-reaction layer) was thicker on convex areas and thinner or entirely missing in the concave regions. The outer layer, mainly consisting of Ca compounds (i.e., the ash-deposition layer), was more likely to be found on the convex areas of the bed particle surface. Overall, the total bed particle layer thickness (inner and outer layer) was larger on the convex areas compared to the concaves. Consequently, the concave regions can facilitate mass transfer to and from the bed particle core even after the full development of the Ca-rich inner layer. Therefore, in the case of using quartz and Na-feldspar particles where there was a high chemical potential to react with fuel-derived gaseous alkali, the inner-inner layer and the crack layers (together referred to as the K-reaction layers) were connected to concaves on the bed particle surface. For the studied oxygen carrier (i.e., ilmenite), where most of the convex regions at the bed particle surface were covered with the Ca-rich layer, Fe could still migrate to the bed particle surface through concaves.

Bed particle layer characteristics observed in the fast pyrolysis plants were, to some extent, different compared to those in the combustion and gasification of woody biomass. In general, the layers were considerably thinner in the fast pyrolysis process, with a similar exposure time compared to combustion and gasification. Crack layers were not detected in quartz and Na-feldspar bed particles in any of the studied fast pyrolysis plants, and the inner layer had a lower Ca concentration than that in the combustion or gasification. Further, only the Ca-reaction layer was identified on feldspar bed particles. However, the distribution pattern of the bed particle layers at different morphologies on the bed particle surface resembled that in combustion and gasification.

The findings indicated that apart from the chemical composition, the surface morphology of the bed particles plays a vital role in determining their performance throughout the fuel conversion process in the fluidized bed. Specifically, as the crack layer formation in quartz bed particles is linked to the concave-shaped areas on the bed particle surface, quartz bed particles characterized by fewer concaves experience less fragmentation during the conversion process. Conversely, when employing ilmenite as an oxygen carrier, the presence of concaves on the particle surface facilitates the outward migration of Fe over prolonged exposures, albeit potentially compromising the structural integrity of the bed materials. Thus, a trade-off exists between achieving a desired oxygen-carrying capacity and maintaining structural integrity over extended durations. Previous studies have suggested that the formation of a Ca-rich layer on bed particles can positively influence the composition of the product gas in the gasification process. Results from this work showed that the Ca-rich layer on bed particles intended for gasification, such as K-feldspar and olivine, is thicker and more evenly distributed on particles possessing a surface morphology featuring more frequent convex shapes.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2024
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-105164 (URN)978-91-8048-546-3 (ISBN)978-91-8048-547-0 (ISBN)
Public defence
2024-06-11, E632, Luleå University of Technology, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2024-04-19 Created: 2024-04-19 Last updated: 2024-05-21Bibliographically approved

Open Access in DiVA

fulltext(23227 kB)125 downloads
File information
File name FULLTEXT01.pdfFile size 23227 kBChecksum SHA-512
c0435537669e003e33ca0e422f71bbc48c95487903cf9a90dd1e832afb7aa71351a52ad17a915b0bf0f4f8d8d047d8f8402b5388938dcce8d2234c1b696e0fc7
Type fulltextMimetype application/pdf

Other links

Publisher's full textScopus

Authority records

Valizadeh, AliForsberg, FredrikLycksam, HenrikÖhman, Marcus

Search in DiVA

By author/editor
Valizadeh, AliSkoglund, NilsForsberg, FredrikLycksam, HenrikÖhman, Marcus
By organisation
Energy ScienceFluid and Experimental Mechanics
In the same journal
Fuel
Energy Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 125 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 539 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf