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  • 1.
    Andersson, Jim
    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.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kirtania, Kawnish
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Multiscale Reactor Network Simulation of an Entrained Flow Biomass Gasifier: Model Description and Validation2017In: Energy Technology, ISSN 2194-4288, Vol. 5, no 8, p. 1484-1494Article in journal (Refereed)
    Abstract [en]

    This paper describes the development of a multiscale equivalent reactor network model for pressurized entrained flow biomass gasification to quantify the effect of operational parameters on the gasification process, including carbon conversion, cold gas efficiency, and syngas methane content. The model, implemented in the commercial software Aspen Plus, includes chemical kinetics as well as heat and mass transfer. Characteristic aspects of the model are the multiscale effect caused by the combination of transport phenomena at particle scale during heating, pyrolysis, and char burnout, as well as the effect of macroscopic gas flow, including gas recirculation. A validation using experimental data from a pilot-scale process shows that the model can provide accurate estimations of carbon conversion, concentrations of main syngas components, and cold gas efficiency over a wide range of oxygen-to-biomass ratios and reactor loads. The syngas methane content was most difficult to estimate accurately owing to the unavailability of accurate kinetic parameters for steam methane reforming.

  • 2.
    Bach Oller, Albert
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kirtania, Kawnish
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    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.
    Co-gasification of black liquor and pyrolysis oil at high temperature: Part 1. Fate of alkali elements2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 202, p. 46-55Article in journal (Refereed)
    Abstract [en]

    The catalytic activity of alkali compounds in black liquor (BL) enables gasification at low temperatures with high carbon conversion and low tar and soot formation. The efficiency and flexibility of the BL gasification process may be improved by mixing BL with fuels with higher energy content such as pyrolysis oil (PO). The fate of alkali elements in blends of BL and PO was investigated, paying special attention to the amount of alkali remaining in the particles after experiments at high temperatures. Experiments were conducted in a drop tube furnace under different environments (5% and 0% vol. CO2 balanced with N2), varying temperature (800–1400 °C), particle size (90–200 µm, 500–630 µm) and blending ratio (0%, 20% and 40% of pyrolysis oil in black liquor). Thermodynamic analysis of the experimental cases was also performed.

    The thermodynamic results qualitatively agreed with experimental measurements but in absolute values equilibrium under predicted alkali release. Alkali release to the gas phase was more severe under inert conditions than in the presence of CO2, but also in 5% CO2 most of the alkali was found in the gas phase at T = 1200 °C and above. However, the concentration of alkali in the gasification residue remained above 30% wt. and was insensitive to temperature variations and the amount of PO in the blend. Thermodynamic analysis and experimental mass balances indicated that elemental alkali strongly interacted with the reactor’s walls (Al2O3) by forming alkali aluminates. The experience indicated that adding PO into BL does not lead to alkali depletion during high temperature gasification.

  • 3.
    Bach Oller, Albert
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kirtania, Kawnish
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    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.
    Co-gasification of black liquor and pyrolysis oil at high temperature: Part 2. Fuel conversion2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 197, p. 240-247Article in journal (Refereed)
    Abstract [en]

    The efficiency and flexibility of the BL gasification process may improve by mixing BL with more energy-rich fuels such as pyrolysis oil (PO). To improve understanding of the fuel conversion process, blends of BL and PO were studied in an atmospheric drop tube furnace. Experiments were performed in varying atmosphere (5% and 0% CO2, balanced by N2), temperature (800–1400 °C), particle size (90–200 μm and 500–630 μm) and blending ratio (0%, 20% and 40% of PO in BL on weight basis). Additionally, pine wood was used as a reference fuel containing little alkali. The addition of PO to BL significantly increased the combined yield of CO and H2 and that of CH4. BL/based fuels showed much lower concentration of tar in syngas than pine wood. Remarkably, the addition of PO in BL further promoted tar reforming in presence of CO2. Unconverted carbon in the gasification residue decreased with increasing fractions of PO. Small fuel particles showed complete conversion at 1000 °C but larger particles did not reach complete conversion even at T = 1400 °C.

  • 4.
    Bach-Oller, Albert
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Fursujo, Erik
    RISE Bioeconomy, Drottning Kristinas väg 61, Stockholm, Sweden.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Effect of potassium impregnation on the emission of tar and soot from biomass gasification2019In: Energy Procedia, ISSN 1876-6102, Vol. 158, p. 619-624Article in journal (Refereed)
    Abstract [en]

    Entrained flow gasification of biomass has the potential to generate synthesis gas as a source of renewable chemicals, electricity, and heat. Nonetheless, formation of tar and soot is a major challenge for continuous operation due to the problems they cause at downstream of the gasifier. Our previous studies showed the addition of alkali in the fuel can bring significant suppression of such undesirable products.

    The present work investigated, in a drop tube furnace, the effect of potassium on tar and soot formation (as well as on its intermediates) for three different types of fuels: an ash lean stemwood, a calcium rich bark and a silicon rich straw. The study focused on an optimal method for impregnating the biomass with potassium. Experiments were conducted for different impregnation methods; wet impregnation, spray impregnation, and solid mixing to investigate different levels of contact between the fuel and the potassium.

    Potassium was shown to catalyze both homogenous and heterogeneous reactions. Wet and spray impregnation had similar effects on heterogeneous reactions (in char conversion) indicating that there was an efficient molecular contact between the potassium and the organic matrix even if potassium was in the form of precipitated salts at a micrometer scale. On the other hand, potassium in the gas phase led to much lower yields of C2 hydrocarbons, heavy tars and soot. These results revealed that potassium shifted the pathways related to tar and soot formation, reducing the likelihood of carbon to end up as soot and heavy tars by favouring the formation of lighter compounds such as benzene. A moderate interaction between the added potassium and the inherent ash forming elements were also observed: Potassium had a smaller effect when the fuel was naturally rich in silicon.

    The combined results open the door to a gasification process that incorporates recirculation of naturally occurring potassium to improve entrained flow gasification of biomass.

  • 5.
    Bach-Oller, Albert
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. RISE Bioeconomy, Stockholm, Sweden.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    On the role of potassium as a tar and soot inhibitor in biomass gasification2019In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 254, article id 113488Article in journal (Refereed)
    Abstract [en]

    The work investigates in a drop tube furnace the effect of potassium on carbon conversion for three different types of fuels: an ash lean stemwood, a calcium-rich bark and a silicon-rich straw. The study focuses on an optimal method for impregnating the biomass with potassium. The experiments are conducted for 3 different impregnation methods; wet impregnation, spray impregnation, and dry mixing to investigate different levels of contact between the fuel and the potassium. Potassium is found to catalyse both homogenous and heterogeneous reactions. All the impregnation methods showed a significant effect of potassium on heterogeneous reactions (char conversion). The fact that dry mixing of potassium in the biomass shows an effect reveals the existence of a gas-induced mechanism that supply and distributes potassium on the char particles. Concerning the effect of potassium on homogenous reactions, it is found that potassium in the gas phase leads to much lower yields of C2 hydrocarbons, heavy tars and soot. The results indicate that potassium reduces the likelihood of light aromatic to progress toward heavier polyaromatic hydrocarbons clusters, thereby inhibiting the formation of soot-like material. A moderate interaction between the added potassium and the inherent ash forming elements is also observed: Potassium has a smaller effect when the fuel is naturally rich in silicon. The combined results are of interest for the design of a gasification process that incorporates recirculation of naturally occurring potassium to improve entrained flow gasification of biomass.

  • 6.
    Bach-Oller, Albert
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. RISE Bioeconomy.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Reduction of tar and soot in biomass gasification with potassium: Effect of impregnation method and inherent inorganic speciesManuscript (preprint) (Other academic)
  • 7.
    Biswas, Amit
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rudolfsson, Magnus
    Swedish University of Agricultural Sciences, Unit of Biomass Technology and Chemistry, Umeå.
    Broström, Markus
    Umeå University. Department of Applied Physics and Electronics.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Effect of pelletizing conditions on combustion behaviour of single wood pellet2014In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 119, p. 79-84Article in journal (Refereed)
    Abstract [en]

    This paper presents how pelletizing die temperature and moisture content affect combustion behaviour of single wood pellet. Pine wood particles with two different moisture contents (i.e. 1 wt.% and 12 wt.%) were pelletized in a laboratory-scale single pelletizer (single die pellets) at die temperature of 20, 100, 150 and 200 °C. The pellets were combusted in a laboratory scale furnace at 800 °C. Time required for single pellet combustion generally increased with both increase of pelletizing temperature and moisture content of biomass. In addition, combustion behaviour of single die pellets was significantly different than those produced in a pilot scale pelletizing plant (semi-industrial scale pellet). That difference was due to variation in physical properties of pellets (e.g. density, and morphology).

  • 8.
    Biswas, Amit
    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.
    Simplification of devolatilization models for thermally-thick particles: differences between wood logs and pellets2015In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 274, p. 181-191Article in journal (Refereed)
    Abstract [en]

    Many phenomena affects devolatilization of relatively large wood particles, e.g. wood pellets and logs, including mass and heat transfer, chemical reactions and physical transformation such as shrinkage. Many studies investigated the importance of these phenomena through detailed mathematical models at particle scale, but the models need to be simplified at a certain degree to be implemented into large-scale simulation for gasifiers and boilers. This paper first presents how each physical and chemical parameter should be modelled for wood logs (low density and anisotropic) and wood pellets (high density and isotropic) through parametric studies with a detailed particle simulation. They required different sub-models for effective thermal conductivity and heat of reactions due to the difference in isotropy of particles between pellets and logs. Then, we demonstrated that a constitutive equation, i.e. analytical solution of the shrinking core model, is sufficient to express devolatilization rate of thermally-thick particles at the temperature of 1173 K with proper sub-models of physical and chemical parameters. The constitutive equation agreed better with experimental data of wood log than wood pellets, mainly because of the error caused during the consideration of the effect of convective cooling of char layer on thermal conductivity. Both detailed and simplified particle models were validated with the experimental data in an isothermal macro thermogravimeter allowing devolatilization of large particles

  • 9.
    Biswas, Amit
    et al.
    Division of Energy and Furnace Technology, Department of Materials Science and Engineering, Royal Institute of Technology.
    Umeki, Kentaro
    Division of Energy and Furnace Technology, Department of Materials Science and Engineering, Royal Institute of Technology.
    Yang, Weihong
    Division of Energy and Furnace Technology, Department of Materials Science and Engineering, Royal Institute of Technology.
    Blasiak, Wlodzimierz
    Division of Energy and Furnace Technology, Department of Materials Science and Engineering, Royal Institute of Technology.
    Change of pyrolysis characteristics and structure of woody biomass due to steam explosion pretreatment2011In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 92, no 10, p. 1849-1854Article in journal (Refereed)
    Abstract [en]

    Steam explosion (SE) pretreatment has been implemented for the production of wood pellet. This paper investigated changes in biomass structure due to implication of steam explosion process by its pyrolysis behavior/ characteristics. Salix wood chip was treated by SE at different pretreatment conditions, and then pyrolysis characteristic was examined by thermogravimetric analyzer (TGA) at heating rate of 10 K/min. Both pyrolysis characteristics and structure of biomass were altered due to SE pretreatment. Hemicellulose decomposition region shifted to low temperature range due to the depolymerization caused by SE pretreatment. The peak intensities of cellulose decreased at mild pretreatment condition while they increased at severe conditions. Lignin reactivity also increased due to SE pretreatment. However, severe pretreatment condition resulted in reduction of lignin reactivity due to condensation and re-polymerization reaction. In summary, higher pretreatment temperature provided more active biomass compared with milder pretreatment conditions. © 2011 Elsevier B.V. All rights reserved.

  • 10.
    Chan, Fan Liang
    et al.
    Catalysis for Green Chemicals Group, Department of Chemical Engineering, Monash University.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Tanksale, Akshat
    Catalysis for Green Chemicals Group, Department of Chemical Engineering, Monash University.
    Kinetic Study of Catalytic Steam Gasification of Biomass by Using Reactive Flash Volatilisation2015In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 7, no 8, p. 1329-1337Article in journal (Refereed)
    Abstract [en]

    Reactive flash volatilisation is an autothermal process to convert biomass into tar-free synthesis gas under steam-rich conditions. This article studies the kinetics of reactive flash volatilisation by using Ni, Pt[BOND]Ni, Ru[BOND]Ni, Re[BOND]Ni, and Rh[BOND]Ni catalysts supported on alumina. The rates of mass loss of cellulose, xylan, and lignin were measured and compared with those of the synthetic biomass mixture and pinewood sawdust. The kinetic parameters were calculated with and without catalysts by using a wire-mesh isothermal thermogravimetric analyser in an equimolar steam/N2 atmosphere and high heating rates of 8.6×102, 1.1×103, and 1.3×104 °C min−1 at 700, 750, and 800 °C, respectively. The results revealed three distinct regimes of the rate of mass loss: pyrolytic decomposition, reforming, and char gasification. The catalysts increased the rate of mass loss in the reforming regime. Rh[BOND]Ni and Ru[BOND]Ni supported catalysts showed higher reforming rates than other catalysts. This study provides direct evidence of the in situ catalytic removal of tar during gasification of biomass

  • 11.
    Chishty, Muhammad Aqib
    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.
    Risberg, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wingren, Anders
    Meva Energy, Backa Bergögata, 42246 Hisingsbacka, Sweden.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Numerical simulation of a biomass cyclone gasifier: Effects of operating conditions on gasifier performance2021In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 218, article id 106861Article in journal (Refereed)
    Abstract [en]

    In Nordic countries, biomass gasification in a cyclone gasifier combined with a gas engine has been employed to generate small scale heat and power. Numerical simulations were carried out to analyze the effect of different operating conditions on the functioning of the gasifier. Reynolds-Averaged Navier-Stokes equations are solved together with the eddy-break up combustion model in conjunction with a modified k − ϵ model to predict the temperature and the flow field inside the gasifier. Results were compared with the experimental measurements in a 4.4 MW cyclone gasifier constructed by Meva Energy AB at Hortlax, Piteå, Sweden. The predicted results were in good agreement with the experimental data and the model provides detailed information about the gas compositions, cold gas efficiency and temperature field. Furthermore, the model allows different operating scenarios to be examined in an efficient manner such as the number of inlets, fuel to air velocity difference (slip-velocity) and moisture content in the fuel feedstock. The cold gas efficiency, composition of product gases and outlet temperature were monitored for each test case. These findings help to understand the importance of geometry modification, feedstock contents and make it possible to scale-up the gasifier for future applications.

  • 12.
    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.

  • 13.
    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.

  • 14.
    Das, Oisik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Mensah, Rhoda Afriyie
    School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China.
    George, Gejo
    Research and Post Graduate Department of Chemistry, St. Berchmans College, Changanacherry, Kerala, India.
    Jiang, Lin
    School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China.
    Xu, Qiang
    School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China.
    Neisiany, Rasoul Esmaeely
    Department of Materials and Polymer Engineering, Faculty of Engineering, Hakim Sabzevari University, Sabzevar, 9617976487, Iran.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Jose E, Tomal
    Research and Post Graduate Department of Chemistry, St. Berchmans College, Changanacherry, Kerala, India.
    Phounglamcheik, Aekjuthon
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hedenqvist, Mikael S.
    Department of Fibre and Polymer Technology, Polymeric Materials Division, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm100 44, Sweden.
    Restás, Ágoston
    Department of Fire Protection and Rescue Control, National University of Public Service, H-1011 Budapest, Hungary.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Försth, Michael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Berto, Filippo
    Department of Mechanical Engineering, Norwegian University of Science and Technology, Trondheim, 7491, Norway.
    Flammability and mechanical properties of biochars made in different pyrolysis reactors2021In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 152, article id 106197Article in journal (Refereed)
    Abstract [en]

    The effect of pyrolysis reactors on the properties of biochars (with a focus on flammability and mechanical characteristics) were investigated by keeping factors such as feedstock, carbonisation temperature, heating rate and residence time constant. The reactors employed were hydrothermal, fixed-bed batch vertical and fixed-bed batch horizontal-tube reactors. The vertical and tube reactors, at the same temperature, produced biochars having comparable elemental carbon content, surface functionalities, thermal degradation pattern and peak heat release rates. The hydrothermal reactor, although, a low-temperature process, produced biochar with high fire resistance because the formed tarry volatiles sealed water inside the pores, which hindered combustion. However, the biochar from hydrothermal reactor had the lowest nanoindentation properties whereas the tube reactor-produced biochar at 300 °C had the highest nanoindentation-hardness (290 Megapascal) and modulus (ca. 4 Gigapascal) amongst the other tested samples. Based on the inherent flammability and mechanical properties of biochars, polymeric composites’ properties can be predicted that can include them as constituents.

  • 15.
    Dossow, Marcel
    et al.
    Technical University of Munich, Chair of Energy Systems, Boltzmannstr. 15 85748 Garching b. München Germany.
    Klüh, Daniel
    Technical University of Munich, Campus Straubing for Biotechnology and Sustainability, Professorship of Regenerative Energy Systems, Schulgasse 16 Straubing 93415 Germany.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Technical University of Munich, Chair of Energy Systems, Boltzmannstr. 15 85748 Garching b. München Germany.
    Gaderer, Matthias
    Technical University of Munich, Campus Straubing for Biotechnology and Sustainability, Professorship of Regenerative Energy Systems, Schulgasse 16 Straubing 93415 Germany.
    Spliethoff, Hartmut
    Technical University of Munich, Chair of Energy Systems, Boltzmannstr. 15 85748 Garching b. München Germany.
    Fendt, Sebastian
    Technical University of Munich, Chair of Energy Systems, Boltzmannstr. 15 85748 Garching b. München Germany.
    Electrification of gasification-based biomass-to-X processes - a critical review and in-depth assessment2023In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706Article, review/survey (Refereed)
    Abstract [en]

    To address the impacts of climate change, it is imperative to significantly decrease anthropogenic greenhouse gas emissions. Biomass-based chemicals and fuels will play a crucial role in substituting fossil-based feedstocks and reducing emissions. Gasification-based biomass conversion processes with catalytic synthesis producing chemicals and fuels (Biomass-to-X, BtX) are an innovative and well-proven process route. Since biomass is a scarce resource, its efficient utilization by maximizing product yield is key. In this review, the electrification of BtX processes is presented and discussed as a technological option to enhance chemical and fuel production from biomass. Electrified processes show many advantages compared to BtX and electricity-based processes (Power-to-X, PtX). Electrification options are classified into direct and indirect processes. While indirect electrification comprises mostly the addition of H2 from water electrolysis (Power-and-Biomass-to-X, PBtX), direct electrification refers to power integration into specific processing steps by converting electricity into the required form of energy such as heat, electrochemical energy or plasma used (eBtX). After the in-depth review of state-of-the-art technologies, all technologies are discussed in terms of process performance, maturity, feasibility, plant location, land requirement, and dynamic operation. H2 addition in PBtX processes has been widely investigated in the literature with process simulations showing significantly increased carbon efficiency and product yield. Similar studies on direct electrification (eBtX) are limited in the literature due to low technological maturity. Further research is required on both, equipment level technology development, as well as process and system level, to compare process options and evaluate performance, economics, environmental impact and future legislation.

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  • 16.
    Furusjö, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kirtania, Kawnish
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Jafri, Yawer
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Oller, Albert Bach
    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.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Landälv, Ingvar
    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.
    Pettersson, Esbjörn
    SP ETC.
    Co-gasification of pyrolysis oil and black liquor - a new track for production of chemicals and transportation fuels from biomass2015Conference paper (Refereed)
    Abstract [en]

    Pressurized oxygen-blown entrained flow black liquor (BL) gasification, the Chemrec technology, has been demonstrated in a 3 MWth pilot plant in Piteå, Sweden for more than 25,000 h. The plant is owned and operated by Luleå University of Technology since 2013. It is well known that catalytic activity of alkali metals is important for the high reactivity of black liquor, which leads to a highly efficient BL gasification process. The globally available volume of BL is however limited and strongly connected to pulp production. By co-gasifying pyrolysis oil (PO) with BL it is possible to utilize the catalytic activity also for PO conversion to syngas. Adding PO leads to larger feedstock flexibility with the possibility of building larger biofuels plants based on BL gasification technology. This presentation summarizes new results from research activities aimed at developing and assessing the PO/BL co-gasification process. Results from laboratory experiments with PO/BL mixtures show that pyrolysis behavior and char gasification reactivity are similar to pure BL. This means that the decrease in the alkali metal concentration due to the addition of PO in the mixture does not decrease the reactivity. Pure PO is much less reactive. Mixing tests show that the fraction of PO that can be mixed into BL is limited by lignin precipitation as a consequence of PO acidity. Pilot scale PO/BL co-gasification experiments have been executed following design and construction of a new feeding system to allow co-feeding of PO with BL. The results confirm the conclusions from the lab scale study and prove that the co-gasification concept is practically applicable. Process performance of the pilot scale co-gasification process is similar to gasification of BL only with high carbon conversion and clean syngas generation. This indicates that the established BL gasification technology can be used for co-gasification of PO and BL without major modifications.

  • 17.
    Gebart, Rikard
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bengtsson, Per-Erik
    Lund University.
    Schmidt, Florian
    Umeå University.
    Wiinikka, Henrik
    RISE-ETC.
    Broström, Markus
    Umeå University.
    Backman, Rainer
    Umeå University.
    Carlborg, Markus
    Umeå University.
    Hellström, J. Gunnar I.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Weiland, Fredrik
    RISE-ETC.
    SFC – Annual Summary from Bio4Gasification (B4G)2020Report (Other (popular science, discussion, etc.))
  • 18.
    Ghasemi Monfared, Zahra
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hellström, J. Gunnar I.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    The Impact of Discrete Element Method Parameters on Realistic Representation of Spherical Particles in a Packed Bed2024In: Processes, E-ISSN 2227-9717, Vol. 12, no 1, article id 183Article in journal (Refereed)
    Abstract [en]

    Packed bed reactors play a crucial role in various industrial applications. This paper utilizes the Discrete Element Method (DEM), an efficient numerical technique for simulating the behavior of packed beds of particles as discrete phases. The focus is on generating densely packed particle beds. To ensure the model accuracy, specific DEM parameters were studied, including sub-step and rolling resistance. The analysis of the packed bed model extended to a detailed exploration of void fraction distribution along radial and vertical directions, considering the impact of wall interactions. Three different samples, spanning particle sizes from 0.3 mm to 6 mm, were used. Results indicated that the number of sub-steps significantly influences void fraction precision, a key criterion for comparing simulations with experimental results. Additionally, the study found that both loosely and densely packed beds of particles could be accurately represented by incorporating appropriate values for rolling friction. This value serves as an indicator of both inter-particle friction and friction between particles and the walls. An optimal rolling friction coefficient has been thereby suggested for the precise representation for the densely packed bed of spherical char particles.

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  • 19.
    Guo, Ning
    et al.
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU – Norwegian University of Science and Technology, Trondheim, Norway.
    Llamas, Angel David Garcia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Li, Tian
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU – Norwegian University of Science and Technology, Trondheim, Norway.
    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.
    Løvås, Terese
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU – Norwegian University of Science and Technology, Trondheim, Norway.
    Computational fluid dynamic simulations of thermochemical conversion of pulverized biomass in a dilute flow using spheroidal approximation2020In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 271, article id 117495Article in journal (Refereed)
    Abstract [en]

    A drag force model for spheroids, referred as the spheroid model, was implemented in OpenFOAM, in order to better predict the thermochemical conversion of pulverized biomass. Our previous work has found that the spheroid model predicts more dispersed results in terms of particle velocities and local concentrations comparing to other conventional particle models under non-reactive conditions. This work takes the spheroid model one step further, by validating against experiments performed under reactive conditions with a newly implemented heat transfer model for spheroids as well as updated devolatilization kinetic parameters. In addition, simulations were conducted in a configuration similar to a pilot-scale entrained flow gasifier for more realistic scenarios. Particle mass and axial velocity development were compared accordingly using four different modelling approaches with increasing complexity. When compared with models of spheroidal shape assumptions, the sphere and simplified non-sphere model predict 61% and 43% longer residence times, respectively. The combination of the spheroid shape assumption with the heat transfer model for spheroids tends to promote drying and devolatilization. On the other hand, the traditional spherical approach leads to longer particle residence times. These opposing effects are believed to be a major contributing factor to the fact that no significant differences among modelling approaches were found in terms of syngas production at the outlet. Furthermore, particle orientation information was reported in both experiments and simulations under reactive conditions. Its dependency on gas velocity gradient under reactive conditions is similar to what was reported under non-reactive conditions.

  • 20.
    Göktepe, Burak
    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.
    Does distance among biomass particles affect soot formation in an entrained flow gasification process?2016In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 141, no 1, p. 99-105Article in journal (Refereed)
    Abstract [en]

    Soot creates technical challenges in entrained flow biomass gasification processes, e.g. clogging of flow passages, fouling on system components and reduced efficiency of gasification. This paper demonstrates a novel soot reduction method in a laboratory-scale entrained flow reactor by forced dispersion of biomass particles. Gasification of small biomass particles was done in a flat flame burner where a steady stream of biomass was sent. The flat flame burner was operated with a premixed sub-stoichiometric methane–air flame to simulate the conditions in an entrained flow gasifier. The dispersion of biomass particles was enhanced by varying the flow velocity ratio between particle carrier gas and the premixed flame. Primary soot particles evolved with the distance from the burner exit and the soot volume fraction was found to have a peak at a certain location. Enhanced particle separation diminished the peaks in the soot volume fraction by 35–56% depending on the particle feeding rates. The soot volume fraction was found to decrease towards an asymptotic value with increasing inter-particle distance.

  • 21.
    Göktepe, Burak
    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.
    Hazim, Ammar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Soot reduction in an entrained flow gasifier of biomass by active dispersion of fuel particles2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 201, p. 111-117Article in journal (Refereed)
    Abstract [en]

    Soot is an undesired by-product of entrained flow biomass gasification since it has a detrimental effect on operation of the gasifier, e.g. clogging of flow passages and system components and reduction of efficiency. This study investigated how active flow manipulation by adding synthetic jet (i.e. oscillating flow through orifice) in feeding line affects dispersion of fuel particles and soot formation. Pine sawdust was gasified at the conditions similar to pulverized burner flame, where a flat flame of methane-air sub-stoichiometric mixture supported ignition of fuel particles. A synthetic jet flow was supplied by an actuator assembly and was directed perpendicular to a vertical tube leading to the center of the flat flame burner through which pine sawdust with a size range of 63–112 μm were fed into a reactor. Quartz filter sampling and the laser extinction methods were employed to measure total soot yield and soot volume fraction, respectively. The synthetic jet actuator modulated the dispersion of the pine sawdust and broke up particle aggregates in both hot and cold gas flows through generation of large scale vortex structures in the flow. The soot yield significantly reduced from 1.52 wt.% to 0.3 wt.% when synthetic jet actuator was applied. The results indicated that the current method suppressed inception of young soot particles. The method has high potential because soot can be reduced without changing major operation parameters.

  • 22.
    Hardi, Flabianus
    et al.
    Department of Environmental Science and Technology, Tokyo Institute of Technology, G5-8, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502, Japan.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Unit of Climate and Sustainable Cities, IVL Swedish Environmental Research Institute, Box 210 60, 100 31 Stockholm, Sweden.
    Kirtania, Kawnish
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Department of Chemical Engineering, Bangladesh University of Engineering and Technology, Dhaka – 1000, Bangladesh.
    Imai, Akihisa
    Department of Environmental Science and Technology, Tokyo Institute of Technology, G5-8, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502, Japan.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Yoshikawa, Kunio
    Department of Environmental Science and Technology, Tokyo Institute of Technology, G5-8, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502, Japan.
    Catalytic hydrothermal liquefaction of biomass with K2CO3 for production of gasification feedstock2021In: Biofuels, ISSN 1759-7269, E-ISSN 1759-7277, Vol. 12, no 2, p. 149-160Article in journal (Refereed)
    Abstract [en]

    The introduction of alkali catalyst during hydrothermal liquefaction (HTL) improves conversion and allows the aqueous liquid product to be used as gasification feedstock. This study investigates the effect of reaction temperature (240–300°C), sawdust mass fraction (9.1–25%) and reaction time (0–60 min) during K2CO3-catalytic HTL of pine sawdust. The highest biomass conversion (75.2% carbon conversion and 83.0% mass conversion) was achieved at a reaction temperature of 270°C, 9.1% sawdust mass fraction and 30 min reaction time; meanwhile, the maximum aqueous product (AP) yield (69.0% carbon yield and 73.5% mass yield) was found at a reaction temperature of 300°C, 9.1% sawdust mass fraction and 60 min reaction time. Based on the main experimental results, models for carbon and mass yields of the products were developed according to face-centered central composite design using response surface methodology. Biomass conversion and product yields had a positive correlation with reaction temperature and reaction time, while they had an inverse correlation with sawdust mass fraction. Further investigation of the effects of biomass/water and biomass/K2CO3 ratios revealed that both high water loading and high K2CO3 loading enhanced conversion and AP yield.

  • 23.
    Hardi, Flabianus
    et al.
    Department of Environmental Science and Technology, Tokyo Institute of Technology.
    Imai, Akihisa
    Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology.
    Theppitak, Sarut
    Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology.
    Kirtania, Kawnish
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    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.
    Yoshikawa, Kunio
    Department of Environmental Science and Technology and ‡Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology.
    Gasification of Char Derived from Catalytic Hydrothermal Liquefaction of Pine Sawdust under a CO2 Atmosphere2018In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 32, no 5, p. 5999-6007Article in journal (Refereed)
    Abstract [en]

    The integration between K2CO3 catalytic hydrothermal liquefaction (HTL) and gasification is explored to improve the gasification process. In this study, the CO2 gasification characteristics and the activation energies of the chars derived from four kinds of HTL products, black liquor (BL), and virgin pine sawdust (PS) are investigated non-isothermally using a thermogravimetric analyzer. The complete conversion of BL char and HTL product chars was achieved at lower temperatures (1150 K) than that of PS char (1300 K). BL char showed the highest derivative thermogravimetric (DTG) peak, an indicator of high reactivity, followed by HTL product chars and PS char. HTL liquid product chars exhibited the lowest DTG peak temperature (1023–1058 K), which is advantageous for the low-temperature gasification. The activation energies were calculated isoconversionally using the Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Starink approximations. On the basis of the KAS method, the range of the activation energy for the HTL aqueous product char sample was 127–259 kJ/mol, which was wider than that for BL char (171–190 kJ/mol). The HTL process can improve the gasification feedstock reactivity, and the use of the HTL liquid product allows for the gasification at a low temperature.

  • 24.
    Hazim, Ammar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Göktepe, Burak
    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.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Active fuel particles dispersion by synthetic jet in an entrained flow gasifier of biomass: Cold flow2016In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 302, p. 275-282Article in journal (Refereed)
    Abstract [en]

    Pulverized fuel (PF) burners play a key role for the performance of PF fired gasification and combustion plants, by minimizing pollutant emission, fuel consumption and hence fuel costs. However, fuel diversity in power generation plants imposes limitations on the performance of existing PF burners, especially when burning solid fuel particles with poor flowability like biomass sawdust. In the present study, a vertically downward laminar flow was laden with biomass particles at different particle mass loading ratios, ranging from 0.47 to 2.67. The particle laden flow was forced by a synthetic jet actuator over a range of forcing amplitudes, 0.35–1.1 kPa. Pulverized pine particles with a sieve size range of 63–112 μm were used as biomass feedstock. Two-phase particle image velocimetry was applied to measure the velocity of the particles and air flow at the same time. The results showed that the synthetic jet had a large influence on the flow fields of both air and powdered pine particles, via a convective effect induced by vortex rings that propagate in the flow direction. The particle velocity, particle dispersion and hence inter-particle distance increased with increasing forcing amplitude. Moreover, particles accumulated within a specific region of the flow, based on their size. The effect on particle dispersion was more pronounced in the forced flows with low mass loading ratios

  • 25.
    He, Qing
    et al.
    Institute of Clean Coal Technology, East China University of Science and Technology, 200237, Shanghai, PR China.
    Guo, Qinghua
    Institute of Clean Coal Technology, East China University of Science and Technology, 200237, Shanghai, PR China.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ding, Lu
    Institute of Clean Coal Technology, East China University of Science and Technology, 200237, Shanghai, PR China; Shanghai Institute of Pollution Control and Ecological Security, 200092, Shanghai, PR China.
    Wang, Fuchen
    Institute of Clean Coal Technology, East China University of Science and Technology, 200237, Shanghai, PR China.
    Yu, Guangsuo
    Institute of Clean Coal Technology, East China University of Science and Technology, 200237, Shanghai, PR China; State Key Laboratory of High-Efficiency Coal Utilization and Green Chemical Engineering, Ningxia University, 750021, Yinchuan, Ningxia, PR China.
    Soot formation during biomass gasification: A critical review2021In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 139, article id 110710Article in journal (Refereed)
    Abstract [en]

    Biomass gasification is a promising technology in current and future low carbon energy systems. Soot formation is a great technical challenge for the industrialization of biomass gasification that is inevitable at high temperature and fuel rich conditions. In this review, a comprehensive summary of soot formation in biomass gasification is provided with special focus on entrained flow technologies. The topics covered the state of the art knowledge of soot formation in different gasifiers, the fundamental knowledge, experimental methods and recent control strategies. Soot generation and oxidation mechanism are discussed while the relationship between soot, tar and char in biomass gasification are analyzed in detail. Reaction models for soot formation coupled to the gasification process are introduced, including (semi-)empirical and detailed models. Effect of biomass components and ash forming elements on soot formation are highlighted. This is followed by a detailed description of in-situ and ex-situ experimental measurements, such as the optical diagnostics, aerosol particle mass analyzer and mass spectrometer. Soot formation characteristics and properties in different types of gasifiers are then addressed in detail with an emphasis of entrained flow gasifiers. Finally, the soot control strategies in biomass gasification are reviewed and evaluated. This review concludes by summarizing the available knowledge and challenges in soot formation during biomass gasification.

  • 26.
    Holmgren, Per
    et al.
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Wagner, David R.
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Strandberg, Anna
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Molinder, Roger
    RISE Energy Technology Center.
    Wiinikka, Henrik
    RISE Energy Technology Center.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Broström, Markus
    Thermochemical Energy Conversion Laboratory (TEC-Lab), Department of Applied Physics and Electronics, Umeå University.
    Size, shape, and density changes of biomass particles during rapid devolatilization2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 206, p. 342-351Article in journal (Refereed)
    Abstract [en]

    Particle properties such as size, shape and density play significant roles on particle flow and flame propagation in pulverized fuel combustion and gasification. A drop tube furnace allows for experiments at high heating rates similar to those found in large-scale appliances, and was used in this study to carry out experiments on pulverized biomass devolatilization, i.e. detailing the first stage of fuel conversion. The objective of this study was to develop a particle conversion model based on optical information on particle size and shape transformation. Pine stem wood and wheat straw were milled and sieved to three narrow size ranges, rapidly heated in a drop tube setup, and solid residues were characterized using optical methods. Different shape descriptors were evaluated and a shape descriptor based on particle perimeter was found to give significant information for accurate estimation of particle volume. The optical conversion model developed was proven useful and showed good agreement with conversion measured using a reference method based on chemical analysis of non-volatilized ash forming elements. The particle conversion model presented can be implemented as a non-intrusive method for in-situ monitoring of particle conversion, provided density data has been calibrated

  • 27.
    Jayawickrama, Thamali Rajika
    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.
    Haugen, Nils Erland L.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Department of Thermal Energy, SINTEF Energy Research, Kolbjørn Hejes vei 1 A, 7491 Trondheim, Norway.
    Babler, Matthaus U.
    Department of Chemical Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    The effects of Stefan flow on the flow surrounding two closely spaced particles2023In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 166, article id 104499Article in journal (Refereed)
    Abstract [en]

    The aim of the work was to study the effects of neighboring particles with uniform Stefan flow in particle–fluid flows. Particle-resolved numerical simulations were carried out for particles emitting a uniform Stefan flow into the bulk fluid. The bulk fluid was uniform and isothermal. The Stefan flow volume emitted from the two particles is equal, such that it represents idealized conditions of reacting particles. Particles were located in tandem arrangement and particle distances were varied between 1.1 and 10 particle diameters (). Three particle Reynolds numbers were considered during the simulations ( and 14), which is similar to our previous studies. Three Stefan flow velocities were also considered during simulations to represent inward, outward, and no Stefan flow. The drag coefficient of the particles without Stefan flow showed that the results fit with previous studies on neighbor particle effects. When the particle distance is greater than 2.5 diameters (), the effects of Stefan flow and neighboring particles are independent of each other. I.e. an outward Stefan flow decreases the drag coefficient () while an inward Stefan flow increases it and the upstream particle experience a higher  than the downstream particle. When , the effect of Stefan flow is dominant, such that equal and opposite pressure forces act on the particles, resulting in a repelling force between the two neighboring particles. The pressure force showed a large increase compared to the viscous force at these distances. The effect of Stefan flow is weakened at higher Reynolds numbers. A model was developed for the calculation of the drag coefficient. The model, which reproduce the results from the numerical simulations presented above, is a product of independent models that describe the effects of both neighboring particles and two distinguished effects of the Stefan flow.

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  • 28.
    Jayawickrama, Thamali Rajika
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Haugen, N.E.L
    SINTEF Energy Research, N-7465 Trondheim, Norway.
    Babler, M.U.
    Department of Chemical Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Effect of Stefan flow on drag coefficient of reactive spherical particles in gas flow2018In: THMT-18. Turbulence Heat and Mass Transfer 9 Proceedings of the Ninth International Symposium On Turbulence Heat and Mass Transfer, Begell House, 2018, p. 1089-1092Conference paper (Refereed)
    Abstract [en]

    Particle laden flows with reactive particles are common in industrial applications. Chemical reactions inside the particle or deposition at the surface can generate additional flow phenomena that affect the heat, mass and momentum transfer between the particle and bulk flow. This work aims at investigating the effect of Stefan flow on the drag coefficient of a spherical particle immersed in a uniform flow. Fully resolved 3D simulations were carried out for particle Reynolds numbers based on the free stream velocity ranging from 0.5 to 3. Simulations are carried out in foam-extend CFD software, using the Immersed Boundary(IB) method for treating fluid-solid interactions. The simulations were validated against data for particles without reactive flow, and against the analytical solution for Stefan flow around a particle in a quiescent fluid. We found that in the considered range of Reynolds number the drag coefficient decreases linearly with in increase in Stefan flow velocity.

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  • 29.
    Jayawickrama, Thamali Rajika
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Haugen, Nils Erland L.
    Department of Energy and Process Engineering, Norwegian University of Science and Technology, Kolbjørn Hejes vei 1 B, 7491 Trondheim, Norway. Department of Thermal Energy, SINTEF Energy Research, Kolbjørn Hejes vei 1 A, 7491 Trondheim, Norway.
    Babler, Matthaus U.
    Department of Chemical Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
    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.
    The effect of Stefan flow on Nusselt number and drag coefficient of spherical particles in non-isothermal gas flow2021In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 140, article id 103650Article in journal (Refereed)
    Abstract [en]

    A Stefan flow can be generated during a phase change or reactions of a particle immersed in a fluid. This study investigates the effect of Stefan flow on the exchange of momentum (drag coefficient (CD)) and heat transfer (Nusselt number (Nu)) between the particle and bulk-fluid. Fully resolved simulations were carried out for a flow near a spherical particle immersed in a uniform bulk flow. The immersed boundary method is used for implementing fluid-solid interactions and the particle is considered as a static boundary with fixed boundary conditions. In a non-isothermal flow, the changes in thermophysical properties at the boundary layer played a role in the variation of CD and Nu by a Stefan flow further. The previously developed model for the drag coefficient of a spherical particle in a uniform isothermal flow was modified for a uniform non-isothermal flow. The model is developed based on physical interpretation. A new model is developed for the Nusselt number for a spherical particle with a uniform Stefan flow combining available models in literature. The models are validated for Stefan Reynolds number −8⩽Resf,p⩽25 and particle Reynolds number of 2⩽Ref⩽30 in gas flow (i.e. Pr≈0.7).

  • 30.
    Jayawickrama, Thamali Rajika
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Haugen, Nils Erland L.
    Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim, Norway.Department of Thermal Energy, SINTEF Energy Research, Trondheim, Norway.
    Babler, Matthaus U.
    Department of Chemical Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    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.
    The effect of Stefan flow on the drag coefficient of spherical particles in a gas flow2019In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 117, p. 130-137Article in journal (Refereed)
    Abstract [en]

    Particle laden flows with reactive particles are common in industrial applications. Chemical reactions inside the particle can generate a Stefan flow that affects heat, mass and momentum transfer between the particle and the bulk flow. This study aims at investigating the effect of Stefan flow on the drag coefficient of a spherical particle immersed in a uniform flow under isothermal conditions. Fully resolved simulations were carried out for particle Reynolds numbers ranging from 0.2 to 14 and Stefan flow Reynolds numbers from (-1) to 3, using the immersed boundary method for treating fluid-solid interactions. Results showed that the drag coefficient decreased with an increase of the outward Stefan flow. The main reason was the change in viscous force by the expansion of the boundary layer surrounding the particle. A simple model was developed based on this physical interpretation. With only one fitting parameter, the performance of the model to describe the simulation data were comparable to previous empirical models.

  • 31.
    Khasevani, Sepideh Gholizadeh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Nikjoo, Dariush
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Chaxel, Cécile
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Sarmad, Shokat
    Wallenberg Wood Science Center, Department of Chemistry Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University, SE-90871 Umeå, Sweden.
    Mikkola, Jyri-Pekka
    Wallenberg Wood Science Center, Department of Chemistry Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University, SE-90871 Umeå, Sweden; Industrial Chemistry & Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, FI-20500 Åbo-Turku, Finland.
    Concina, Isabella
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Empowering Adsorption and Photocatalytic Degradation of Ciprofloxacin on BiOI Composites: A Material-by-Design Investigation2023In: ACS Omega, E-ISSN 2470-1343, Vol. 8, no 46, p. 44044-44056Article in journal (Refereed)
    Abstract [en]

    Binary and ternary composites of BiOI with NH2-MIL-101(Fe) and a functionalized biochar were synthesized through an in situ approach, aimed at spurring the activity of the semiconductor as a photocatalyst for the removal of ciprofloxacin (CIP) from water. Experimental outcomes showed a drastic enhancement of the adsorption and the equilibrium (which increased from 39.31 mg g–1 of bare BiOI to 76.39 mg g–1 of the best ternary composite in 2 h time), while the kinetics of the process was not significantly changed. The photocatalytic performance was also significantly enhanced, and the complete removal of 10 ppm of CIP in 3 h reaction time was recorded under simulated solar light irradiation for the best catalyst of the investigated batch. Catalytic reactions supported by different materials obeyed different reaction orders, indicating the existence of different mechanisms. The use of scavengers for superoxide anion radicals, holes, and hydroxyl radicals showed that although all these species are involved in CIP photodegradation, the latter play the most crucial role, as also confirmed by carrying out the reaction at increasing pH conditions. A clear correlation between the reduction of BiOI crystallite sizes in the composites, as compared to the bare material, and the material performance as both adsorbers and photocatalyst was identified. 

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  • 32.
    Kirtania, Kawnish
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Axelsson, Joel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kinetic study of catalytic gasification of wood char impregnated with different alkali salts2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 118, p. 1055-1065Article in journal (Refereed)
    Abstract [en]

    Different concentrations (0.1 and 1 M K+/Na+) of salt solutions (K2CO3, Na2CO3, NaOH and NaCl) were used to impregnate alkali in sawdust. After devolatilization, char samples were gasified at different temperatures (750–900 °C) under CO2 in a macro-thermogravimetric analyzer for gasification kinetics. Morphologically, three classes of chars could be identified. Chars experiencing the highest catalytic influence were in Class-2 (0.5 M K2CO3 and 1 M NaOH) with a swollen and molten surface. In contrast, Class-1 (wood char like) and Class-3 (with salt deposits) chars showed moderate and low catalytic effect on gasification reactivity respectively. It is believed to be related to char surface swelling and alkali salt used. At 850 °C or below, the reactivity increased linearly (Class-1 and Class-3 Char) with initial alkali content up to 2200 mmol alkali/kg of char (except for NaCl). The same reaction rate was maintained until 3600 mmol/kg of char of alkali loading (Class-2) and then decreased. However, no trend was observed at 900 °C due to drastic change in reactivity of the samples, probably due to alkali transformation. Among the salts, K2CO3 (0.5 M) was found to be the most suitable for catalytic gasification due to its high catalytic activity in combination with relatively low carbon leaching.

  • 33.
    Kirtania, Kawnish
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Axelsson, Joel
    Luleå University of Technology.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Furusjö, Erik
    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.
    Alkali catalyzed gasification of solid biomass: influence on fuel conversion and tar/soot reduction2016In: Proceedings of the 24th European Biomass Conference and Exhibition, Amsterdam: ETA Florence Renewable Energies , 2016, p. 533-536Conference paper (Refereed)
    Abstract [en]

    Based on char gasification experiments in an isothermal thermogravimetric analyzer, a suitable concentration of alkali salt (K2CO3) was chosen for impregnation due to almost five-fold increase in gasification reactivity and relatively low amount of carbon leaching during impregnation. Furthermore, an optimum method for wet alkali impregnation was proposed based on the several tests performed by varying temperature and time. To study the catalytic effect on tar and soot yield, untreated and impregnated woody biomass were gasified under entrained flow condition between 900 oC and 1200 oC. Impregnation leads to 70% lower tar yield from gasification around 1000 oC and 1100 oC. The lowest amount of soot was detected for the same temperature range whereas the soot yield was one order of magnitude higher for untreated biomass. For tar, this influence became insignificant at a higher temperature (1200 oC). This defines the suitable temperature range for alkali catalyzed gasification without the loss of catalytic activity.

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  • 34.
    Kirtania, Kawnish
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Häggström, Gustav
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Broström, Markus
    Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory, Umeå University, 90187 Umeå, Sweden.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Cogasification of Crude Glycerol and Black Liquor Blends: Char Morphology and Gasification Kinetics2017In: Energy Technology, ISSN 2194-4296, Vol. 5, no 8, p. 1272-1281Article in journal (Refereed)
    Abstract [en]

    This study assesses the feasibility of black liquor/glycerol blends as potential gasification feedstock. The char gasification reactivity and kinetics were studied at T = 750 °C, 800 °C, 850 °C and 900 °C for 20% and 40% blends of glycerol with black liquor. Three qualities of glycerol were used including two industrial grade crude glycerols. Gasification rates were similar for all blends, indicating sufficient alkali metal catalysis also for the char blends (Alkali/C atomic ratio between 0.45 and 0.55). The blends with the most impure glycerol (containing K) were found to have the lowest activation energies (~120 kJ/mol) and reaction times for char gasification indicating fuel properties suitable for gasification. Char particles from different blends showed similar surface morphology as black liquor chars with even surface distribution of alkali elements. A loss of alkali (mainly, K) from the fuel blends during pyrolysis indicated the necessity to perform gas-phase studies of alkali release. Overall, these results encourage the use of glycerol as a potential gasification feedstock for catalytic gasification based bio-refineries.  

  • 35.
    Kramb, Jason
    et al.
    Department of Chemistry, Renewable Energy Programme, University of Jyväskylä.
    Konttinen, Jukka
    Department of Chemistry, Renewable Energy Programme, University of Jyväskylä.
    Gómez-Barea, Alberto
    Bioenergy Group, Chemical and Environmental Engineering Department, Escuela Superior de Ingenieros, University of Seville.
    Moilanen, Antero
    VTT Technical Research Centre of Finland, Espoo.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Modeling biomass char gasification kinetics for improving prediction of carbon conversion in a fluidized bed gasifier2014In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 132, p. 107-115Article in journal (Refereed)
    Abstract [en]

    Gasification of biomass in a fluidized bed (FB) was modeled based on kinetic data obtained from previously conducted thermogravimetric analysis. The thermogravimetric analysis experiments were designed to closely resemble conditions in a real FB gasifier by using high sample heating rates, in situ devolatilization and gas atmospheres of H2O/H2 and CO2/CO mixtures. Several char kinetic models were evaluated based on their ability to predict char conversion based on the thermogravimetric data. A modified version of the random pore model was shown to provide good fitting of the char reactivity and suitability for use in a reactor model. An updated FB reactor model which incorporates the newly developed char kinetic expression and a submodel for the estimation of char residence time is presented and results from simulations were compared against pilot scale gasification data of pine sawdust. The reactor model showed good ability for predicting char conversion and product gas composition.

  • 36.
    Kreitzberg, Thobias
    et al.
    Institute of Heat and Mass Transfer, RWTH Aachen University, Aachen, Germany.
    Phounglamcheik, Aekjuthon
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Haugen, Nils Erland L.
    Department of Thermal Energy, SINTEF Energy Research, Trondheim, Norway.
    Kneer, Reinhold
    Institute of Heat and Mass Transfer, RWTH Aachen University, Aachen, Germany.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    A Shortcut Method to Predict Particle Size Changes during Char Combustion and Gasification under regime II Conditions2022In: Combustion Science and Technology, ISSN 0010-2202, E-ISSN 1563-521X, Vol. 194, no 2, p. 272-291Article in journal (Refereed)
    Abstract [en]

    In most industrial applications, combustion and gasification of char progresses under regime II conditions. Unlike in other regimes, both particle size and density change simultaneously in regime II due to non-uniform consumption of carbon inside the particles. In this work, mathematical predictions of diameter changes in regime II were made by a one-dimensional simulation tool, where transient species balances are resolved locally inside the particle. This simulation is computationally expensive and usually not appropriate for the implementation in comprehensive CFD simulations of combustion or gasification processes. To overcome this restraint, an alternative shortcut method with affordable computation time has been developed and validated against the detailed model. This method allows the calculation of diameter changes during combustion and gasification from precalculated effectiveness factors. Additionally, the change of particle size has been investigated experimentally in a single particle converter setup. Therein, particles are fixed on a sample holder placed in the hot flue gas of a flat flame burner. Size and temperature trends are optically assessed by a 3CCD camera.

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  • 37.
    Kuba, Matthias
    et al.
    BEST – Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, 8010, Graz, Austria. Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Getreidemarkt 9/166, 1060, Vienna, Austria.
    Fürsatz, Katharina
    BEST – Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, 8010, Graz, Austria.
    Janisch, Daniel
    Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Getreidemarkt 9/166, 1060, Vienna, Austria.
    Aziaba, Kouessan
    Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Getreidemarkt 9/166, 1060, Vienna, Austria.
    Chlebda, Damian
    Jagiellonian University, ul. Gronostajowa 2, 30-387, Kraków, Poland.
    Łojewska, Joanna
    Jagiellonian University, ul. Gronostajowa 2, 30-387, Kraków, Poland.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hofbauer, Hermann
    Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Getreidemarkt 9/166, 1060, Vienna, Austria.
    Surface characterization of ash-layered olivine from fluidized bed biomass gasification2021In: Biomass Conversion and Biorefinery, ISSN 2190-6815, E-ISSN 2190-6823, Vol. 11, no 1, p. 29-38Article in journal (Refereed)
    Abstract [en]

    The present study aims to present a comprehensive characterization of the surface of ash-layered olivine bed particles from dual fluidized bed gasification. It is well known from operation experience at industrial gasification plants that the bed material is activated during operation concerning its positive influence on gasification reactions. This is due to the built up of ash layers on the bed material particles; however, the chemical mechanisms are not well understood yet. Olivine samples from long-term operation in an industrial-scale gasification plant were investigated in comparison to fresh unused olivine. Changes of the surface morphology due to Ca-enrichment showed a significant increase of their surface area. Furthermore, the Ca-enrichment on the ash layer surface was distinctively associated to CaO being present. The presence of CaO on the surface was proven by adsorption tests of carbon monoxide as model compound. The detailed characterization contributes to a deeper understanding of the surface properties of ash layers and forms the basis for further investigations into their influence on gasification reactions.

  • 38.
    Llamas, Angel David Garcia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Guo, Ning
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU - Norwegian University of Science and Technology, Trondheim, Norway.
    Li, Tian
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU - Norwegian University of Science and Technology, Trondheim, Norway.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Løvås, Terese
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU - Norwegian University of Science and Technology, Trondheim, Norway.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Morphology and volume fraction of biomass particles in a jet flow during devolatilization2020In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 278, article id 118241Article in journal (Refereed)
    Abstract [en]

    Particle size, aspect ratio (AR, defined here as major over minor dimension), orientation and volume fraction have been measured for a stream of pulverized biomass particles undergoing devolatilization. Milling of raw biomass for thermochemical conversion yields elongated particles with high AR. Particle shape affects the heat and mass transfers and motion of particles within a jet, potentially shifting the particle group regimes. Therefore, the effects of carrier gas flow and fuel AR on the devolatilization behavior of biomass particles streams have been addressed experimentally. Two shapes of dried Norwegian Spruce have been used: one nearly equant (AR = 1.8 ± 0.64) and the other elongated (AR = 3.8 ± 2.9), both derived from the same sieve size of 200–250 μm. Experiments were performed in a laboratory-scale flat-flame assisted laminar drop tube reactor, where similar mass flows of particles (10–16 g⋅h−1) were injected with two different flow rates of CO2 to a high temperature flame zone (methane flame at O2-to-fuel equivalence ratio of λ = 0.63). Time and space-averaged measurements of particle morphology and velocity during conversion were obtained with 2D particle tracking velocimetry (PTV) together with image analysis. Carrier gas flow acted as thermal ballast, affecting the heating rate to the gas and particles. Heterogeneity in morphological changes was observed, and the behavior was affected by heating rate, particle shape and carrier gas flows. This paper describes phenomena relevant for the understanding of biomass devolatilization under very fast heating rates, such as shrinking, transient swelling, spherodization and lateral migration, and relates them to differences in heating rate and particle shape.

  • 39.
    Llamas, Ángel David García
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Guo, Ning
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU - Norwegian University of Science and Technology, Trondheim, Norway.
    Li, Tian
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU - Norwegian University of Science and Technology, Trondheim, Norway;RISE Fire Research, Tiller 7092, Norway.
    Gebart, Rikard
    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.
    Rapid change of particle velocity due to volatile gas release during biomass devolatilization2022In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 238, article id 111898Article in journal (Refereed)
    Abstract [en]

    Our earlier study showed significant differences in average particle velocity between simulation and experimental results for devolatilizing biomass particles in an idealised entrained flow reactor [N. Guo et al., Fuel, 2020]. This indicates that the simulations do not accurately describe the physicochemical transformations and fluid dynamic processes during devolatilization. This article investigates the reasons for these discrepancies using time-resolved analyses of the experimental data and complementary modelling work. The experiments were conducted in a downdraft drop-tube furnace with optical access, which uses a fuel-rich flat flame (CH4 O2 CO2) to heat the particles. Gas flow was characterized using particle image velocimetry, equilibrium calculations and thermocouple measurements. High-speed images of devolatilizing Norway spruce (Picea Abies) particles were captured and analysed using time-resolved particle tracking velocimetry methods. The data were used to estimate the balance of forces and fuel conversion. Thrust and “rocket-like” motions were frequently observed, followed by quick entrainment in the gas flow. Rocketing particles were, on average, smaller, more spherical and converted faster than their non-rocketing counterparts. These differences in conversion behaviour could be captured by a particle-size dependent, 0-D devolatilization model, corrected for non-isothermal effects. The results from this investigation can provide a basis for future modelling and simulation work relevant for pulverized firing technologies.

  • 40.
    Lotfian, Samira
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Ahmed, Hesham
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. Central Metallurgical Research and Development Institute (CMRDI) Cairo, Egypt.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Samuelsson, Caisa
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Conversion Characteristics of Alternative Reducing Agents for the Bath Smelting Processes in an Oxidizing Atmosphere2019In: Journal of Sustainable Metallurgy, ISSN 2199-3823, Vol. 5, no 2, p. 230-239Article in journal (Refereed)
    Abstract [en]

    The amount of plastic-containing materials, such as shredder residue material, which is generated after the processing of electronic equipment waste, is increasing. One interesting option for the sustainable management of these materials, instead of incineration or landfilling, is recycling through injection in a bath smelting process, such as zinc fuming. In this way, the plastic material could partially substitute coal as a reductant in the process. In such processes, shredder residue material is injected alongside air into the furnace at temperatures up to 1250 °C. Once the material is injected, it undergoes several conversion steps, including ignition, devolatilization, and char oxidation. In this study, the conversions of shredder residue material and other pure plastic materials were investigated using a drop tube furnace and an optical single-particle burner. The effect of particle size on the conversion time of each material was studied. The conversion time of the particles increases as the particle size increases, although the relationship is not linear. The results indicate that plastic materials with a particle size range of 1–7 mm have a considerably longer conversion time than that of coal used in the conventional processes.

  • 41.
    Mesfun, Sennai
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Anderson, Jan-Olof
    Process Energy Engineering, Solvina, SE-42130 Västra Frölunda.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Integrated SNG Production in a Typical Nordic Sawmill2016In: Energies, E-ISSN 1996-1073, Vol. 9, no 5, article id 333.Article in journal (Refereed)
    Abstract [en]

    Advanced biomass-based motor fuels and chemicals are becoming increasingly important to replace fossil energy sources within the coming decades. It is likely that the new biorefineries will evolve mainly from existing forest industry sites, as they already have the required biomass handling infrastructure in place. The main objective of this work is to assess the potential for increasing the profit margin from sawmill byproducts by integrating innovative downstream processes. The focus is on the techno-economic evaluation of an integrated site for biomass-based synthetic natural gas (bio-SNG) production. The option of using the syngas in a biomass-integrated gasification combined cycle (b-IGCC) for the production of electricity (instead of SNG) is also considered for comparison. The process flowsheets that are used to analyze the energy and material balances are modelled in MATLAB and Simulink. A mathematical process integration model of a typical Nordic sawmill is used to analyze the effects on the energy flows in the overall site, as well as to evaluate the site economics. Different plant sizes have been considered in order to assess the economy-of-scale effect. The technical data required as input are collected from the literature and, in some cases, from experiments. The investment cost is evaluated on the basis of conducted studies, third party supplier budget quotations and in-house database information. This paper presents complete material and energy balances of the considered processes and the resulting process economics. Results show that in order for the integrated SNG production to be favored, depending on the sawmill size, a biofuel subsidy in the order of 28–52 €/MWh SNG is required.

  • 42.
    Mesfun, Sennai
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Andersson, Jan Olof
    Process Energy Engineering, Solvina, SE-42130 Västra Frölunda.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Integrated SNG production in a typical Nordic sawmill2015In: ECOS 2015: 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems , 2015Conference paper (Refereed)
    Abstract [en]

    Advanced biomass based motor fuels and chemicals are becoming increasingly important to replace fossil energy sources within the coming decades. It is likely that the new biorefineries will evolve mainly from existing forest industry sites as they already have the required biomass handling infrastructure in place. The main objective of this work is to assess the potential for increasing the profit margin from sawmill byproducts by integrating innovative downstream processes. The focus is on the techno-economic evaluation of an integrated site for bio-SNG production. The option of using the syngas in a b-IGCC for the production of electricity (instead of SNG) is also considered for comparison. The process flowsheets that are used to analyse the energy and material balances are modelled in MATLAB and Simulink. A mathematical process integration model of a typical Nordic sawmill is used to analyse the effects on the energy flows in the overall site as well as to evaluate the site economics. Different plant sizes have been considered in order to assess the economy-of-scale effect. The technical data required as input are collected from the literature and, in some cases, from experiments. The investment cost is evaluated on the basis of conducted studies, third party supplier budget quotations and in-house database information. This paper presents complete material and energy balances of the considered processes and the resulting process economics.

  • 43.
    Moilanen, Antero
    et al.
    VTT Technical Research Centre of Finland, Espoo.
    Lehtinen, Jere
    VTT Technical Research Centre of Finland, Espoo.
    Kurkela, Minna
    VTT Technical Research Centre of Finland, Espoo.
    Muhola, Mirja
    VTT Technical Research Centre of Finland, Espoo.
    Tuomi, Sanna
    VTT Technical Research Centre of Finland, Espoo.
    Carlsson, Per
    Energy Technology Centre, Piteå.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Güell, Berta Matas
    SINTEF.
    Sandquist, Judit
    SINTEF.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Andersson, Jim
    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.
    Ma, Charlie
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kurkela, Esa
    VTT Technical Research Centre of Finland, Espoo.
    Wiinikka, Henrik
    Wang, Liang
    SINTEF.
    Backman, Rainer
    Umeå university, Åbo Akademi, Energy Technology and Thermal Process Chemistry, Umeå University.
    Biomass gasification fundamentals to support the development of BTL in forest industry2015Report (Other academic)
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  • 44. Namioka, Tomoaki
    et al.
    Miyazaki, Mitsuo
    Morohashi, Yoshiaki
    Umeki, Kentaro
    Yoshikawa, Kunio
    Modeling and Analysis of Batch-Type Thermal Sludge Pretreatment for Optimal Design2008In: Journal of Environment and Engineering, ISSN 1880-988X, Vol. 3, no 1, p. 170-181Article in journal (Refereed)
    Abstract [en]

    We present a model to simulate the increase in sludge temperature during batch-type thermal pretreatment of sewage sludge. The semi-theoretical model is based on energy balance as a function of operating conditions, including non-ideal factors determined by fitting. The model was verified by comparison with the results of bench-scale runs. It predicted the relationship between the operating conditions and steam input with sufficient accuracy. The test plant needed more energy input than the ideal during operation owing to the influence of the heat capacity of the apparatus. To optimize the scale of the apparatus, we simulated the treatment of 10 t of sludge. The energy input was minimized with 10 runs of a 1-t apparatus if the heat capacity of the ancillary apparatus exceeds a certain threshold, and 5 runs with a 2-t apparatus if the heat capacity is below the threshold. The influence of the boiler's performance on energy input is small, but its effect on the heat-up rate of the sludge is large. A boiler with sufficient equivalent evaporation and rated pressure will shorten the operating time.

  • 45.
    Oller, Albert Bach
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    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.
    Fuel conversion characteristics of black liquor and pyrolysis oil mixture for efficient gasification with inherent catalyst2014In: European biomass conference and exhibition proceedings, 2014Conference paper (Refereed)
    Abstract [en]

    This paper describes the technical feasibility of a catalytic co-gasification process using a mixture of black liquor (BL) and pyrolysis oil (PO). A technical concern is if gasifiers can be operated at low temperature (~1000 ºC) without problems of tar, soot or char, as is the case for pure BL due to the catalytic effect of fuel alkali. Hence, we investigated fuel conversion characteristics of BL/PO mixture: conversion of single droplet in flame, and char gasification reactivity. 20wt.% (BP20) and 30wt.% (BP30) were selected for weight fraction of PO because of lignin precipitation in BP30. Single droplet was devolatilized and gasified in a methane flame with a flat flame burner at various droplet sizes. Conversion time and swelling ratio were investigated with imaging. They were more sensitive to initial droplet size and reaction atmosphere than the mixing of BL and PO. Char gasification reactivity was measured in an isothermal thermogravimeter (iTG) at T=880–940 ºC and PCO2=1 bar. Both BP20 and BP30 showed complete char conversion and there was no statistically significant difference in char reactivity among BP20, BP30 and BL. These results show that PO can be co-gasified in BL gasification process without major changes in the operation.

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  • 46.
    Oller, Albert Bach
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    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.
    Fuel conversion characteristics of black liquor and pyrolysis oil mixtures: Efficient gasification with inherent catalyst2015In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 79, p. 155-165Article in journal (Refereed)
    Abstract [en]

    Alkali metals inherent in black liquor (BL) have strong catalytic activity during gasification. A catalytic co-gasification process based on BL with pyrolysis oil (PO) has the potential to be a part of efficient and fuel-flexible biofuel production systems. The objective of the paper is to investigate how adding PO into BL alters fuel conversion under gasification conditions. First, the conversion times of single fuel droplet were observed in a flat flame burner under different conditions. Fuel conversion times of PO/BL mixtures were significantly lower than PO and comparable to BL. Initial droplet size (300–1500 μm) was the main variable affecting devolatilization, indicating control by external heat transfer. Char oxidation was affected by droplet size and the surrounding gas composition. Then, the intrinsic reactivity of char gasification was measured in an isothermal thermogravimetric analyser at T = 993–1133 K under the flow of CO2–N2 mixtures. All the BL-based samples (100% BL, 20% PO/80% BL, and 30% PO/70% BL on mass basis) showed very high char conversion. Conversion rate of char gasification for PO/BL mixtures was comparable to that of pure BL although the fraction of alkali metal in char decreased because of mixing. The reactivities of BL and BL/PO chars were higher than the literature values for solid biomass and coal chars by several orders of magnitude. The combined results suggest that fuel mixtures containing up to 30% of PO on mass basis may be feasible in existing BL gasification technology.

  • 47.
    Oller, Albert Bach
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kirtania, Kawnish
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    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.
    Characterization of tar and soot formation for an improved co-gasification of black liquor and pyrolysis oil2015Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    Black liquor (BL) gasification is a proven process with very low tar generation at lower temperature than other entrained-flow biomass gasification processes. Recently, BL gasification technology was further expanded to increase feedstock flexibility by co-gasifying pyrolysis oil (PO) with BL. Economic advantage was shown by a techno-economic study. Our previous lab-scale studies using a thermo-gravimetric analyzer and a flat flame burner showed high char reactivity of sample mixture (30wt.% blend of PO into BL) as alkali content in BL kept high catalytic activity despite being diluted by the addition of PO. However, tar and soot formation from this new feedstock remained unknown. In this study, we investigated how the reaction conditions affect the formation of tar and soot to understand their formation mechanism and to suggest suitable operation conditions for the industrial processes. Experiments were carried out with fuel blends containing between 0 and 40wt.% of PO in BL using a laminar entrained flow reactor under the flow of N2/CO2. The effects of operating parameters were evaluated by varying temperature (1073-1673 K), partial pressure of CO2 (0-20 kPa), particle size (90-200 μm and 500-630 μm) and residence time. High temperature (i.e. 1673 K), high heating rate and short residence time experiments were performed to mimic industrial-scale conditions. Soot yield was under detection limit while low amounts of tar (mainly benzene) were formed at low temperature and decreased as the temperature increased. Addition of PO maintained the yields of tar and soot very low while it increased the syngas yield. Overall, this study demonstrated the feasibility of co-gasification of PO and BL and provided valuable information about tar formation under different operating conditions.

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  • 48.
    Phounglamcheik, Aekjuthon
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bäckebo, Markus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Robinson, Ryan
    Global Technology, Höganäs AB, Höganäs, Sweden.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    The significance of intraparticle and interparticle diffusion during CO2 gasification of biomass char in a packed bed2022In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 310, article id 122302Article in journal (Refereed)
    Abstract [en]

    This study investigates the influences of intraparticle and interparticle diffusions on the reaction rates of char gasification in a packed bed without forced convective flows. The main objective is to elucidate how the dominant scales of mass diffusion resistance change based on particle size distributions (PSD). CO2 gasification rates were measured by thermogravimetric analyses (TGA) of spruce char produced from pilot-scale reactors. Experimental setups using two TGA devices highlighted the effects on different rate-limiting steps. Effects of intraparticle diffusion were investigated with a single layer of monodispersed particles between 75 µm and 6.3 mm using a commercial TGA. Effects of interparticle diffusion were investigated with a packed bed of monodispersed and polydispersed particles using a macro-TG. At the particle scale, gasification rate decreased with the increase of particle size when the reaction was controlled by intraparticle diffusion. This effect can be described by the effectiveness factor with Thiele modulus. At the bed scale, void fraction and tortuosity of the packed bed are influential parameters on diffusivity of CO2 through the bed channels. Due to its non-sphericity of the char particles, the bed of relatively large particles had high void fraction and the presence of smaller particles were essential to lower the bed void size. Consequently, smaller size fraction in the PSD had a major impact on the diffusion resistance at bed scale. It means that the diffusion resistances at particle and bed scales are sensitive to different size fractions in the PSD. It allows one to tweak the overall reaction rates in packed beds by manipulating the PSD if the dominant mass transport mechanism is diffusion.

  • 49.
    Phounglamcheik, Aekjuthon
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Johnson, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kienzl, Norbert
    BEST—Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, 8010 Graz, Austria.
    Strasser, Christoph
    BEST—Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, 8010 Graz, Austria.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Self-Heating of Biochar during Postproduction Storage by O2 Chemisorption at Low Temperatures2022In: Energies, E-ISSN 1996-1073, Vol. 15, no 1, article id 380Article in journal (Refereed)
    Abstract [en]

    Biochar is attracting attention as an alternative carbon/fuel source to coal in the process industry and energy sector. However, it is prone to self-heating and often leads to spontaneous ignition and thermal runaway during storage, resulting in production loss and health risks. This study investigates biochar self-heating upon its contact with O2 at low temperatures, i.e., 50–300 °C. First, kinetic parameters of O2 adsorption and CO2 release were measured in a thermogravimetric analyzer using biochar produced from a pilot-scale pyrolysis process. Then, specific heat capacity and heat of reactions were measured in a differential scanning calorimeter. Finally, a one-dimensional transient model was developed to simulate self-heating in containers and gain insight into the influences of major parameters. The model showed a good agreement with experimental measurement in a closed metal container. It was observed that char temperature slowly increased from the initial temperature due to heat released during O2 adsorption. Thermal runaway, i.e., self-ignition, was observed in some cases even at the initial biochar temperature of ca. 200 °C. However, if O2 is not permeable through the container materials, the temperature starts decreasing after the consumption of O2 in the container. The simulation model was also applied to examine important factors related to self-heating. The results suggested that self-heating can be somewhat mitigated by decreasing the void fraction, reducing storage volume, and lowering the initial char temperature. This study demonstrated a robust way to estimate the cooling demands required in the biochar production process.

  • 50.
    Phounglamcheik, Aekjuthon
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Pitchot, Romain
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Andefors, Alf
    Future Eco North Sweden AB.
    Norberg, Niclas
    Future Eco North Sweden AB.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Production of metallurgical charcoal from biomass pyrolysis: pilot-scale experiment2018Conference paper (Refereed)
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