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  • 1.
    Dal Belo Takehara, Marcelo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Experimental analysis of a pulverized biomass-fired entrained flow reactor under imposed acoustic oscillations2022Licentiate thesis, comprehensive summary (Other academic)
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  • 2.
    Dal Belo Takehara, Marcelo
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Chishty, Muhammad Aqib
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Pulverized biomass flame under imposed acoustic oscillations: Flame morphology and emission characteristics2022In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 238, article id 107484Article in journal (Refereed)
    Abstract [en]

    Forced intermittent combustion with periodical variations of pressure, velocity, and air-fuel ratios is a promising method to increase efficiency and reduce emissions from combustion and gasification applications. In this work, flame characteristics and emissions from a pulverized biomass burner are investigated under oscillations induced by an acoustically-driven synthetic jet. Instantaneous images of incandescent light emitted from flame were captured using high-speed cameras. The images were analyzed to identify the liftoff distance, flame length, and shape. The flame liftoff distance decreased under excited conditions, notably at high forcing amplitude applied to small particle size distribution (63-112 μm). In such conditions, acoustic forcing increases particle dispersion as presented in the previous work, providing conditions for earlier ignition due to enhanced fuel-air mixing besides reducing CO emissions. Flue gas emissions were influenced mainly by the particle size distribution, from which the 63-112 μm particle size presented the lowest values of CO and highest levels of NO emissions. The results presented stable flame edge positions for the particle size of 63-112 μm, while wide range particle distributions (0–600, 0-400 μm) had strong fluctuations, indicating high flame instability. The experimental work adds new insights regarding acoustic excitation in swirl burners, which could be used to optimize pulverized fuel combustion.

  • 3.
    Dal Belo Takehara, Marcelo
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Llamas, Angel David Garcia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Chishty, Muhammad Aqib
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Effect of acoustic perturbation on particle dispersion in a swirl-stabilized pulverized fuel burner: Cold-flow conditions2022In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 228, article id 107142Article in journal (Refereed)
    Abstract [en]

    Inter-particle distance and particle dispersion during gasification of biomass have been found to significantly affect soot emission. Consequently, enhanced particle dispersion decreases energy losses and the risk for blockages of downstream equipment, increasing the efficiency and reliability of entrained flow reactors (EFRs). In this work, we investigated the interactions between imposed acoustic oscillations and particle dispersion under non-reacting conditions in a co-axial burner for a lab-scale EFR. A flow of air, laden with pulverized stem wood particles (Norwegian Spruce) of three different sizes (63–112 μm, 200–250 μm, and 500–600 μm), was forced axially through the burner center tube at Reynolds numbers ranged from 800 to 1700, and loading ratio of 0.7–4.2. The influences on particle dispersion from variations of the Strouhal number (0.12–0.6), the pressure amplitude at synthetic jet cavity (0.5–4.0 kPap-p), the swirl number (0–2.3), and the center jet velocity (1.9–3.9 m s−1) were investigated. Post-processed shadowgraph images revealed the influence of acoustic perturbations, which generate large structures with high particle concentration for both swirling and non-swirling conditions. Time-averaged contour maps showed a significantly higher particle dispersion, quantified as dispersion angle, for higher values of forcing amplitude and swirl numbers, with a stronger influence from the forcing amplitude, especially at lower Stokes number.

  • 4.
    Dal Belo Takehara, Marcelo
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Investigation of oxygen-enriched biomass flames in a lab-scale entrained flow reactor2024In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 366, article id 131343Article in journal (Refereed)
    Abstract [en]

    Oxygen-enriched air combustion of pulverized biomass fuel is an effective method to improve char combustion and improve flame stability. Moreover, understanding the impact of O2 addition is an important step toward oxyfuel combustion, one of the most promising technologies for bioenergy with carbon capture and storage (BECCS). Our previous studies focused on flow manipulation methods, e.g., swirling co-flow and acoustic forcing, to enhance particle dispersion during biomass combustion and gasification. This work aims to extend the understanding of the effect of different manipulation methods on oxygen-enriched combustion at different levels in a lab-scale entrained flow reactor. This methodology combines the analysis of visible flame characteristics, CO and NO gas emissions, and coarse particle emissions characterization with thermogravimetric analysis and particle size distribution by dynamic imaging. The results indicated that oxygen-enriched combustion leads to lower liftoff distance and higher flame brightness. Moreover, oxygen-enriched combustion presented coarse particle emissions with finer particle size distribution and lower carbon content. The acoustic forcing further decreased the flame liftoff and decreased CO emissions, increasing combustion efficiency under conditions with similar equivalence ratios and lower momentum flux at the secondary air.

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  • 5.
    Purnomo, Victor
    et al.
    Division of Energy and Materials, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg 412 58, Sweden.
    Dal Belo Takehara, Marcelo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Faust, Robin
    Division of Energy and Materials, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg 412 58, Sweden.
    Ejjeta, Lidiya Abdisa
    Division of Energy and Materials, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg 412 58, Sweden.
    Leion, Henrik
    Division of Energy and Materials, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg 412 58, Sweden.
    New approach for particle size and shape analysis of iron-based oxygen carriers at multiple oxidation states2024In: Particuology, ISSN 1674-2001, E-ISSN 2210-4291, Vol. 90, p. 493-503Article in journal (Refereed)
    Abstract [en]

    One of the crucial issues in the chemical looping technology lies in its bed material: the oxygen carrier. Particle size analysis of an oxygen carrier is important since in a fluidized bed the material can only work well within a specific size range. While the favorable size ranges for oxygen carrier materials have already been reported, none of the published studies has analyzed the particle size and shape of oxygen carriers in detail. Furthermore, the effect of oxygen carriers' oxidation degree on such properties has not been considered either. This study aimed to report the particle size and shape analysis of five iron-based oxygen carriers, one natural ore, one synthetic material, and three residue products, at different oxidation degrees using dynamic image analysis (DIA). The oxygen carriers were prepared at different mass conversion degrees in a fluidized bed batch reactor. The size distribution, sphericity, and aspect ratio of the oxygen carrier particles were examined experimentally using a Camsizer instrument. Our results show that the DIA method was successfully able to analyze the particle size and shape of our oxygen carriers with satisfying accuracy for comparison. The oxidation state of the investigated materials seems to only affect the particle size and shape of oxygen carriers to a minor extent. However, exposures to redox cycles in a fluidized bed reactor may alter the particle size and shape of most oxygen carriers.

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