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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, E-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.
    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.

  • 12.
    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.

  • 13.
    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.

  • 14.
    Hardi, Flabianus
    et al.
    Department of Environmental Science and Technology, Tokyo Institute of Technology.
    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.
    Imai, Akihisa
    Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology.
    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.
    Catalytic hydrothermal liquefaction of biomass with K2CO3 for production of gasification feedstock2018In: Biofuels, ISSN 1759-7269, E-ISSN 1759-7277Article 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.

  • 15.
    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.

  • 16.
    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

  • 17.
    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

  • 18.
    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.

  • 19.
    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 withdifferent 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.

  • 20.
    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.

  • 21.
    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
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory,.
    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.  

  • 22.
    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.

  • 23.
    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.

  • 24.
    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, ISSN 1996-1073, 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.

  • 25.
    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.

  • 26.
    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)
  • 27. 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.

  • 28.
    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.

  • 29.
    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.

  • 30.
    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.

  • 31.
    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)
  • 32.
    Phounglamcheik, Aekjuthon
    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.
    Change in size and density of a biomass char during heterogeneous reactions2018Conference paper (Refereed)
  • 33.
    Phounglamcheik, Aekjuthon
    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.
    Wretborn, Tobias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Biomass pyrolysis with bio-oil recycle to increase energy recovery in biochar2017Conference paper (Refereed)
    Abstract [en]

    ABSTRACT: This study aims at increasing char yield by recycling bio-oil without negative impact on char qualities, i.e. carbon content and heating value. Pyrolysis experiments on spruce and birch chips were carried in a macro-thermogravimetric analyzer. To examine the effect of bio-oil recycle, dried raw woodchips, pure bio-oil, and woodchips impregnated with bio-oil (10, 20 and 25% on mass basis) were compared. The experiments were carried out by introducing sample into the reaction zone with the flow of N2 and at the temperature range of 300 to 600 ˚C. Pyrolysis of the bio-oil impregnated woodchip gave higher char yield than the pyrolysis of raw woodchip. By the 20% (m/m) bio-oil impregnation, char yield increased by 18.9% (spruce) and 19.1% (birch) on average from the raw woodchip pyrolysis. In addition, the char yield from bio-oil impregnated woodchips was higher than the interpolated char yield of raw woodchips and bio-oil, indicating that synergy effect exists by bio-oil impregnation compared with mere recycling of bio-oil. However, high heating rate corresponded to high temperature pyrolysis, i.e. above 400 ˚C, created cavities and breakages on woodchips, which minimized the secondary reaction. Neither carbon content nor heating value of char was influenced by bio-oil impregnation. Energy yield also showed improvement by increasing bio-oil recycling ratio. For example, energy yield of char from woodchips at the temperature of 340 ˚C increased from 48.4% with raw woodchips to 64.5% by woodchips with 25% of bio-oil impregnation.

  • 34.
    Phounglamcheik, Aekjuthon
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wang, Liang
    SINTEF Energy Research .
    Romar, Henrik
    University of Oulu, Research Unit of Applied Chemistry.
    Broström, Markus
    Umeå University, Department of Applied Physics and Electronics.
    Ramser, Kerstin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Skreiberg, Øyvind
    SINTEF Energy Research .
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Effects of pyrolysis oil recycling and reaction gas atmosphere on the physical properties and reactivity of charcoal from wood2018Conference paper (Refereed)
  • 35.
    Phounglamcheik, Aekjuthon
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wretborn, Tobias
    Luleå University of Technology.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Biomass pyrolysis with bio-oil recycle to increase energy recovery2017Conference paper (Refereed)
    Abstract [en]

    This study aims at increasing char yield by recycling bio-oil without negative impact on char qualities, i.e. carbon content and heating value. Pyrolysis experiments on spruce and birch chips were carried in a macro-thermogravimetric analyzer. To examine the effect of bio-oil recycle, dried raw woodchips, pure bio-oil, and woodchips impregnated with bio-oil (10, 20 and 25% on mass basis) were compared. The experiments were carried out by introducing sample into the reaction zone with the flow of N2 and at the temperature range of 300 to 600 ˚C. Pyrolysis of the bio-oil impregnated woodchip gave higher char yield than the pyrolysis of raw woodchip. By the 20% (m/m) bio-oil impregnation, char yield increased by 18.9% (spruce) and 19.1% (birch) on average from the raw woodchip pyrolysis. In addition, the char yield from bio-oil impregnated woodchips was higher than the interpolated char yield of raw woodchips and bio-oil, indicating that synergy effect exists by bio-oil impregnation compared with mere recycling of bio-oil. However, high heating rate corresponded to high temperature pyrolysis, i.e. above 400 ˚C, created cavities and breakages on woodchips, which minimized the secondary reaction. Neither carbon content nor heating value of char was influenced by bio-oil impregnation. Energy yield also showed improvement by increasing bio-oil recycling ratio. For example, energy yield of char from woodchips at the temperature of 340 ˚C increased from 48.4% with raw woodchips to 64.5% by woodchips with 25% of bio-oil impregnation.

  • 36.
    Phounglamcheik, Aekjuthon
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wretborn, Tobias
    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.
    Increasing efficiency of charcoal production with bio-oil recycling2018In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 32, no 9, p. 9650-9658Article in journal (Refereed)
    Abstract [en]

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

  • 37.
    Prabowo, Bayu
    et al.
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama.
    Aziz, Muhammad
    Solutions Research Laboratory, Tokyo Institute of Technology.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Susanto, Herri
    Department of Chemical Engineering, Institut Teknologi Bandung.
    Yan, Mi
    State Key Laboratory of Clean Energy Utilization, Zhejiang University.
    Yoshikawa, Kunio
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama, Tokyo Institute of Technology.
    CO2-recycling biomass gasification system for highly efficient and carbon-negative power generation2015In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 158, p. 97-106, article id 6848Article in journal (Refereed)
    Abstract [en]

    This study explored the feasibility of biomass CO2 gasification as an effective method for implementing the concept of a carbon-negative power system through bioenergy with carbon capturing and storage. A CO2-recycling biomass gasification system was developed and examined using the thermal equilibrium model. Sensitivity analysis was performed by varying the gasifier temperature from 750 to 950 °C, and the turbine inlet temperature (TIT) and turbine exit temperature (TET) of the gas turbine from 1000 to 1200 °C and from 900 to 1000 °C, respectively. The gasifier efficiency was increased by an increase in the CO2 recycling ratio with the more significant trend shown at the lower gasifier temperature. The turbine efficiency decreased as the CO2 recycling ratio to the gasifier increased over a certain limit, a ratio of 0.55 in most cases. A pressure ratio of 2.3 was optimum in terms of turbine efficiency. Under the examined conditions, the optimum conditions for gaining the highest system efficiency, 39.03%, were a recycling ratio of 0.55 and a TET and TIT of 1000 and 1200 °C respectively. The proposed system had 7.57% higher efficiency and exhausted 299.15 g CO2/kW h less CO2 emissions than conventional air gasification. Combined with carbon capturing and storage, the system potentially generates carbon-negative power generation with intensity of around 1.55-kg CO2/kg wet-biomass and a maximum efficiency penalty of 6.89%.

  • 38.
    Prabowo, Bayu
    et al.
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama, Institute of Energy and Power Engineering, Zhejiang University of Technology.
    Aziz, Muhammad
    Solutions Research Laboratory, Tokyo Institute of Technology.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Yan, Mi
    State Key Laboratory of Clean Energy Utilization, Zhejiang University, Institute of Energy and Power Engineering, Zhejiang University of Technology.
    Susanto, Herri
    Institute Technology of Bandung, Department of Chemical Engineering.
    Yoshikawa, Kunio
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama, Tokyo Institute of Technology, Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology.
    Utilization of Rice Husk in the CO2-Recycling Gasification System for the Effective Implementation of Bioenergy with Carbon Capture and Storage (BECCS) Technology2015In: Advances in CO₂ capture, sequestration, and conversion / [ed] Fangming Jin; Liang-Nian He; Yun Hang Hu, Washington, DC: American Chemical Society (ACS), 2015, p. 323-340Conference paper (Refereed)
    Abstract [en]

    A biomass gasification system with CO2-recycling was developed and examined using the thermal equilibrium model. Performance comparison was conducted against the conventional air gasification system. Sensitivity analyses were performed by varying the gasifier temperature from 750 degrees C to 950 degrees C and testing three kinds of rice husk as feedstock: As harvested, naturally dried, or torrefied. The proposed system produced 7.5 % higher efficiency than the conventional air gasification. Moreover, the system exhausted 302 g-CO2/kWh lower emission and in the form of high purity of CO2 stream that is favorable for sequestration process. The recycled CO2 from the gas turbine acted as an effective heat source for the gasifier as well as gasifying agent. The positive effect of CO2-recycling was more prominent at the lower gasifier temperature. The utilization of high quality feedstock, i.e. low moisture content and low O/C ratio, was favorable for optimizing the effect of CO2-recycling on the system efficiency. Under the examined conditions, the optimum conditions for gaining the highest system efficiency, 39,4%, were a gasifier temperature of 850 degrees C with CO2 recycling ratio of 0.87 and the torrefied feedstock. Application of carbon capture and storage process to the system at the optimum condition resulted in 1.75 kg-CO2/kg-dry-biomass negative carbon intensity with merely 6.5% efficiency penalty. These results show that the CO2-recycling gasification system is promising for effectively applying BECCS concept.

  • 39.
    Prabowo, Bayu
    et al.
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama.
    Susanto, Herri
    Department of Chemical Engineering, Institut Teknologi Bandung.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Yan, Mi
    State Key Laboratory of Clean Energy Utilization, Zhejiang University, Institute of Energy and Power Engineering, Zhejiang University of Technology.
    Yoshikawa, Kunio
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama, Tokyo Institute of Technology, Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology.
    Pilot scale autothermal gasification of coconut shell with CO2-O2 mixture2015In: Frontiers in Energy, ISSN 2095-1701, E-ISSN 2095-1698, Vol. 9, no 3, p. 362-370Article in journal (Refereed)
    Abstract [en]

    This paper explored the feasibility and benefit of CO2 utilization as gasifying agent in the autothermal gasification process. The effects of CO2 injection on reaction temperature and producer gas composition were examined in a pilot scale downdraft gasifier by varying the CO2/C ratio from 0.6 to 1.6. O2 was injected at an equivalence ratio of approximately 0.33–0.38 for supplying heat through partial combustion. The results were also compared with those of air gasification. In general, the increase in CO2 injection resulted in the shift of combustion zone to the downstream of the gasifier. However, compared with that of air gasification, the long and distributed high temperature zones were obtained in CO2-O2 gasification with a CO2/C ratio of 0.6–1.2. The progress of the expected CO2 to CO conversion can be implied from the relatively insignificant decrease in CO fraction as the CO2/C ratio increased. The producer gas heating value of CO2-O2 gasification was consistently higher than that of air gasification. These results show the potential of CO2-O2 gasification for producing high quality producer gas in an efficient manner, and the necessity for more work to deeply imply the observation

  • 40.
    Prabowo, Bayu
    et al.
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Yan, Mi
    State Key Laboratory of Clean Energy Utilization, Zhejiang University.
    Nakamura, Masato R.
    Department of Mechanical Engineering and Industrial Design Technology, New York City College of Technology (City Tech), City University of New York (CUNY).
    Castradi, Marco J.
    Department of Chemical Engineering, The City College of New York, City University of New York (CUNY).
    Yoshikawa, Kunio
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama.
    CO2–steam mixture for direct and indirect gasification of rice straw in a downdraft gasifier: Laboratory-scale experiments and performance prediction2014In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 113, p. 670-679Article in journal (Refereed)
    Abstract [en]

    This paper explored the feasibility of CO2 as alternative gasifying agent of steam to obtain higher thermal efficiency in biomass gasification. The effect of the gasifying agent on gas evolution and thermal efficiency was examined by using a lab scale downdraft gasifier. The results were also compared with the output of pyrolysis with N2. The reaction atmosphere in indirect and direct gasification was simulated by carrying out the experiments without and with O2 presence. The reaction conditions were varied in the temperature range from 750 °C to 950 °C by changing the CO2 molar fraction in gasifying agent to the ratio of 0, 30 and 60 vol.% in balance with steam. 40 vol.% of N2 fraction was kept during O2 free experiments, while 31.7 vol.% of N2 and 8.3 vol.% O2 were kept during the experiments with the presence of O2. At all examined condition, gasification yielded more combustible gas than pyrolysis. Furthermore, high CO2 fraction in gasifying agent generally resulted in low H2 yield and high CO yield. These substitutions mostly lowered the energy yield of the producer gas, but in the other hand also reduced the preheating energy of gasifying agent. Thus, optimizations of these changes were investigated for gaining highest thermal efficiency of the gasification process. Highest thermal efficiency of the process without O2 was 52% under N2 (40 vol.%)–CO2 (60 vol.%) atmosphere at the temperature of 850 °C. For the process with O2, where the part of gasifying agent preheating energy supplied by the biomass partial combustion, the highest thermal efficiency was 60% under the CO2 (60 vol.%)–O2 (8.3 vol.%)–N2 (31.7 vol.%) atmosphere at the temperature of 950 °C. CO2 utilization as a gasifying agent potentially increases the thermal efficiency of biomass conversion process compared with pyrolysis or conventional indirect and direct gasification, i.e. pure-steam gasification and O2–steam gasification.

  • 41.
    Samuelsson, Lina N.
    et al.
    Department of Chemical Engineering and Technology, KTH Royal Institute of Technology.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Babler, Matthaus U.
    Department of Chemical Engineering and Technology, KTH Royal Institute of Technology.
    Mass loss rates for wood chips at isothermal pyrolysis conditions: A comparison with low heating rate powder data2017In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 158, p. 26-34Article in journal (Refereed)
    Abstract [en]

    Spruce chips of three different thicknesses were pyrolyzed isothermally in a vertical furnace macro-TGA at 574 to 676K, which is the temperature range relevant for char production. The measured mass loss data was analyzed in terms of mass loss rate, thermal lag and char yield as a function of chip size and pyrolysis temperature. The char yield decreased with increasing temperature and there was no significant difference in char yield as a function of sample thickness, ranging from 1mm to 7mm. Thermal lag was present for all chip sizes above 600K. At 574K the data suggests that chips below 1mm in thickness are decomposing at rates governed by reaction kinetics. An isoconversional kinetic model based on low heating rate data of spruce powder was adopted to analyze the data. The model predicted lower mass loss rates than those measured for the chips, suggesting that the pyrolysis process of wood proceeds through a network of parallel reactions. Despite this, the model could predict the final char yield of the wood chips with an accuracy above 80%. The predictive capability of the isoconversional reaction rate expression is promising since the procedure to derive such a rate expression is straight-forward, compared to the conventional model-fitting methods. The data and modeling approach presented in this work is important to the field of biomass pyrolysis as it covers the temperature range and chip sizes relevant for pyrolysis in multi-staged gasification plants which has been given little attention.

  • 42.
    Strandberg, Anna
    et al.
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Holmgren, Per
    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.
    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
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Effects of pyrolysis conditions and ash formation on gasification rates of biomass char2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 6, p. 6507-6514Article in journal (Refereed)
    Abstract [en]

    Pyrolysis conditions and the presence of ash-forming elements significantly influence char properties and its oxidation or gasification reactivity. In this study, intrinsic gasification rates of char from high heating rate pyrolysis were analyzed with isothermal thermogravimetry. The char particles were prepared from two biomasses at three size ranges and at two temperatures. Reactivity dependence on original particle size was found only for small wood particles that had higher intrinsic char gasification rates. Pyrolysis temperature had no significant effect on char reactivity within the range tested. Observations of ash formation highlighted that reactivity was influenced by the presence of ash-forming elements, not only at the active char sites but also through prohibition of contact between char and gasification agent by ash layer formation with properties highly depending on ash composition.

  • 43.
    Suopajärvi, Hannu
    et al.
    Process Metallurgy Research Unit, University of Oulu.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Mousa, Elsayed
    Swerea MEFOS, Process Integration Department.
    Hedayati, Ali
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Romar, Henrik
    Research Unit of Sustainable Chemistry, University of Oulu.
    Kemppainen, Antti
    Process Metallurgy Research Unit, University of Oulu.
    Wang, Chuan
    Swerea MEFOS, Process Integration Department.
    Phounglamcheik, Aekjuthon
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Tuomikoski, Sari
    Research Unit of Sustainable Chemistry, University of Oulu.
    Norberg, Nicklas
    Future Eco North Sweden AB.
    Andefors, Alf
    Future Eco North Sweden AB.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lassi, Ulla
    Research Unit of Sustainable Chemistry, University of Oulu.
    Fabritius, Timo
    Process Metallurgy Research Unit, University of Oulu.
    Use of biomass in integrated steelmaking: Status quo, future needs and comparison to other low-CO2 steel production technologies2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 213, p. 384-407Article in journal (Refereed)
    Abstract [en]

    This paper provides a fundamental and critical review of biomass application as a reducing agent and fuel in integrated steelmaking. The basis for the review is derived from the current process and product quality requirements that also biomass-derived fuels should fulfill. The availability and characteristics of different sources of biomass are discussed and suitable pretreatment technologies for their upgrading are evaluated. The existing literature concerning biomass application in bio-coke making, blast furnace injection, iron ore sintering and production of carbon composite agglomerates is reviewed and research gaps filled by providing insights and recommendations to the unresolved challenges. Several possibilities to integrate the production of biomass-based reducing agents with existing industrial infrastructures to lower the cost and increase the total efficiency are given. A comparison of technical challenges and CO2 emission reduction potential between biomass-based steelmaking and other emerging technologies to produce low-CO2 steel is made.

  • 44.
    Tanaka, Yasuto
    et al.
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama.
    Mesfun, Sennai
    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.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Tamura, Yutaka
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama, Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1 Ookayama.
    Yoshikawa, Kunio
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama, Tokyo Institute of Technology, Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology.
    Thermodynamic performance of a hybrid power generation system using biomass gasification and concentrated solar thermal processes2015In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 160, p. 664-672Article in journal (Refereed)
    Abstract [en]

    This paper describes the investigation of a hybrid power production system from biomass and solar energy. This paper suggests integration through heat exchanger network as a useful approach to obtain the synergy between biomass and solar. Biomass is first gasified in a bubbling fluidized bed (BFB) gasifier, and then syngas is used in a gas turbine. Excess heat exists in this sub-system and concentrated solar thermal process (CSTP) while there is a demand of steam for generating gasifying agent. Steam Rankine cycle exploits the heat created by these thermal streams to generate power while satisfying the steam demands. Thermodynamic performance was analyzed by process modelling with a semi-kinetic model of BFB gasifier and pinch analyses. The composition and temperature of gasifying agent showed some effect on the overall efficiency of the system. Higher overall efficiency of the system was achieved at higher temperature and higher O2 fraction in the O2-steam mixture as gasifying agent. The increase in thermal input from CSTP had positive effect on overall efficiency of the hybrid system until thermal input from CSTP becomes dominant against thermal stream related to the gasifier and the gas turbine.

  • 45.
    Tanaka, Yasuto
    et al.
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Tamura, Yutaka
    Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama.
    Yoshikawa, Kunio
    Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology.
    Performance of a Hybrid Power Generation System Using Biomass Gasification and Concentrated Solar Thermal Processes2014In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 61, p. 2149-2153Article in journal (Refereed)
    Abstract [en]

    A hybrid power generation system using biomass gasification and concentrated solar thermal processes (CSTP) was proposed. We analysed the system performance of a combined cycle with a bubbling fluidized bed gasifier (BFG) using CO2-H2O-O2 mixture and CSTP using molten salt. BFG was simulated by a semi-kinetic model, applying a continuously stirred tank reactor (CSTR) model for the bed behaviour and a plug flow reactor (PFR) model for the freeboard reactions. Operating conditions of the plant and heat exchanger network were optimized separately. The current paper shows the effects of gasifying agents and heat input from CSTP on system efficiency among examined parameters. Pure steam at the molar ratio of steam to carbon in biomass around 0.5 was optimum gasifying agent in this system. By increasing heat input from CSTP, marginal efficiency of biomass-to-electricity was enhanced by 6.2-6.5% (from 39.9 ∼41.2% to 46.1∼47.5%).

  • 46.
    Toloue Farrokh, Najibeh
    et al.
    Process Metallurgy Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Oulu, Finland.
    Suopajärvi, Hannu
    Process Metallurgy Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Oulu, Finland.
    Mattila, Olli
    Process Metallurgy Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Oulu, Finland.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Phounglamcheik, Aekjuthon
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Romar, Henrik
    Research Unit of Sustainable Chemistry, University of Oulu, P.O. Box 3000, FI-90014, Oulu,.
    Sulasalmi, Petri
    Process Metallurgy Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Oulu.
    Fabritius, Timo
    Process Metallurgy Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Oulu.
    Slow pyrolysis of by-product lignin from wood-based ethanol production: A detailed analysis of the produced chars2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 164, p. 112-123Article in journal (Refereed)
    Abstract [en]

    Slow pyrolysis as a method of producing a high-quality energy carrier from lignin recovered from wood-based ethanol production has not been studied for co-firing or blast furnace (BF) applications up to now. This paper investigates fuel characteristics, grindability, moisture uptake and the flow properties of lignin chars derived from the slow pyrolysis of lignin at temperatures of 300, 500 and 650 °C (L300, L500 and L650 samples respectively) at a heating rate of 5 °C min-1. The lignin chars revealed a high mass and energy yield in the range of 39-73% and 53-89% respectively. Pyrolysis at 500 °C or higher, yielded lignin chars with low H/C and O/C ratios suitable for BF injection. Furthermore, the hydrophobicity of lignin was improved tremendously after pyrolysis. Pyrolysis at high temperatures increased the sphericity of the lignin char particles and caused some agglomeration in L650. Large and less spherical particles were found to be a reason for high permeability, compressibility and cohesion of L300 in contrast to L500 and L650. L300 and L500 chars demonstrated high combustibility with low ignition and burnout temperatures. Also, rheometric analysis showed that L500 has the best flow properties including low aeration energy and high flow function.

  • 47.
    Trubetskaya, Anna
    et al.
    Thermochemical Energy Conversion Laboratory , Umeå University.
    Broström, Markus
    Thermochemical Energy Conversion Laboratory (TEC-Lab), Department of Applied Physics and Electronics, Umeå University.
    Kling, Jens
    Center for Electron Nanoscopy , Technical University of Denmark.
    Brown, Avery
    Chemical Engineering Department, Worcester Polytechnic Institute.
    Tompsett, Geoffrey
    Chemical Engineering Department, Worcester Polytechnic Institute.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Effects of Lignocellulosic Compounds on the Yield, Nanostructure and Reactivity of Soot from Fast Pyrolysis at High Temperatures2017Conference paper (Other academic)
    Abstract [en]

    Gasification offers the utilization of biomass to a wide variety of applications such as heat, electricity, chemicals and transport fuels in an efficient and sustainable manner. High soot yields in the high-temperature entrained flow gasification lead to intensive gas cleaning and can cause a possible plant shut down. The reduction of soot formation increases the overall production system efficiency and improves the economic feasibility and reliability of the gasification plant. The aim of this work is to present the effect of lignocellulosic compoundson the yield, nanostructure and reactivity of soot. Soot was produced from holocelluloses, extractives, two types of organosolv lignin (softwood and wheat straw), and lignin-derived compounds (syringol, guaiacol, p-hydroxyphenol)at temperature of 1250°Cand residence time of 0.17 sand 0.35 sin a drop tube furnace.Soxhlet extraction was performed on soot samples from pyrolysis of both lignin samplesusing acetone and methanol as a solvent.The structure of solid residues was characterized by transmission electron microscopy and Raman spectroscopy. The reactivity of soot inO2oxidation and CO2gasificationwas investigated by thermogravimetric analysis. The present results indicated that soot yields from pyrolysis of ligninfrom softwood and extractives at 1250°C with the residence time of 0.17 swere similaras shown in Figure 1. The highest soot yield was obtained from pyrolysis of wheat straw lignin and quantitatively comparable with the soot yield of hydroquinone. The presence of hydroxyl groups compared to other lignin-derived compounds representing S-and G-lignin types might enhance the soot formation.Lower soot yields were obtained from pyrolysis of cellulose and hemicellulosedue to the lower presence of inherent aromatic rings [1-3].Moreover, the soot yields from pyrolysis of potassium impregnated lignin at 1250°C with the residence time of 0.35 swere significantly lower than that of non-treated lignin samples indicating the catalytic influence of potassium inhibitinggrowth of polycyclic aromatic hydrocarbons, confirming the previous results of Umeki et al. [4]

  • 48.
    Trubetskaya, Anna
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. hermochemical Energy Conversion Laboratory, Umeå University.
    Hofmann Larsen, Flemming
    Department of Food Science, University of Copenhagen.
    Shchukarev, Andrey
    Department of Chemistry, Umeå University.
    Ståhl, Kenny
    Department of Chemistry, Technical University of Denmark.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Potassium and soot interaction in fast biomass pyrolysis at high temperatures2018In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 225, p. 89-94Article in journal (Refereed)
    Abstract [en]

    his study aims to investigate the interaction between potassium and carbonaceous matrix of soot produced from wood and herbaceous biomass pyrolysis at high heating rates at 1250°C in a drop tube reactor. The influence of soot carbon chemistry and potassium content in the original biomass on the CO2 reactivity was studied by thermogravimetric analysis. The XPS results showed that potassium incorporation with oxygen-containing surface groups in the soot matrix did not occur during high temperature pyrolysis. The potassium was mostly found as water-soluble salts such as KCl, KOH, KHCO3 and K2CO3 in herbaceous biomass soot. The low ash-containing pinewood soot was less reactive than the potassium rich herbaceous biomass soot, indicating a dominating role of potassium on the soot reactivity. However, the catalytic effect of potassium on the reactivity remained the same after a certain potassium amount was incorporated in the soot matrix during pyrolysis. Raman spectroscopy results showed that the carbon chemistry of biomass soot also affected the CO2 reactivity. The less reactive pinewood soot was more graphitic than herbaceous biomass soot samples with the disordered carbon structure.

  • 49.
    Trubetskaya, Anna
    et al.
    Mechanical Engineering Department, National University of Ireland Galway.
    Hofmann Larsen, Flemming
    Department of Food Science, University of Copenhagen.
    Shchukarev, Andrey
    Department of Chemistry, Umeå University.
    Ståhl, Kenny
    Department of Chemistry, Technical University of Denmark.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Potassium and soot interaction in fast biomass pyrolysis at high temperatures2018Conference paper (Refereed)
  • 50.
    Trubetskaya, Anna
    et al.
    DTU Chemical Engineering, Technical University of Denmark.
    Jensen, Peter Arendt
    Department of Chemical and Biochemical Engineering, Denmark Technical University.
    Glarborg, Peter
    Department of Chemical and Biochemical Engineering, Denmark Technical University.
    Garcia Llamas, Angel David
    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.
    Kling, Jens
    Center for Electron Nanoscopy , Technical University of Denmark.
    Gardini, Diego
    Center for Electron Nanoscopy , Technical University of Denmark.
    Bates, Richard B.
    MIT, Department of Mechanical Engineering.
    Jensen, Anker Degn
    Department of Chemical and Biochemical Engineering, Denmark Technical University.
    Effects of Biomass Feedstock on the Yield and Reactivity of Soot from Fast Pyrolysis at High Temperatures2016Conference paper (Refereed)
12 1 - 50 of 67
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