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  • 1.
    Andersson, Jim
    et al.
    Luleå University of Technology, Sweden.
    Umeki, Kentaro
    Luleå University of Technology, Sweden.
    Furusjö, Erik
    Luleå University of Technology, Sweden.
    Kirtania, Kawnish
    Luleå University of Technology, Sweden.
    Weiland, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Multiscale Reactor Network Simulation of an Entrained Flow Biomass Gasifier: Model Description and Validation2017In: Energy Technology, ISSN 2194-4288, Vol. 5, p. 1-12Article 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.
    Bräck, Thomas
    et al.
    Meva Energy, Sweden.
    Weiland, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Pettersson, Esbjörn
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Hedman, Henry
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Sepman, Alexeu
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Replace fossil gas in industrial burners with renewable biogas2018In: The 8th Nordic Wood Biorefinery Conference: NWBC 2018: proceedings / [ed] Hytönen Eemeli, Vepsäläinen Jessica, Espoo: VTT Technical Research Centre of Finland , 2018, p. 73-73Conference paper (Refereed)
  • 3.
    Carlborg, Markus
    et al.
    Umeå University, Sweden.
    Weiland, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Ma, Charlie
    Luleå University of Technology, Sweden.
    Backman, Rainer
    Umeå University, Sweden.
    Landälv, Ingvar
    Luleå University of Technology, Sweden.
    Winikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Exposure of refractory materials during high-temperature gasification of a woody biomass and peat mixture2018In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 38, no 2, p. 777-787Article in journal (Refereed)
    Abstract [en]

    Finding resilient refractory materials for slagging gasification systems have the potential to reduce costs and improve the overall plant availability by extending the service life. In this study, different refractory materials were evaluated under slagging gasification conditions. Refractory probes were continuously exposed for up to 27 h in an atmospheric, oxygen blown, entrained flow gasifier fired with a mixture of bark and peat powder. Slag infiltration depth and microstructure were studied using SEM EDS. Crystalline phases were identified with powder XRD. Increased levels of Al, originating from refractory materials, were seen in all slags. The fused cast materials were least affected, even though dissolution and slag penetration could still be observed. Thermodynamic equilibrium calculations were done for mixtures of refractory and slag, from which phase assemblages were predicted and viscosities for the liquid parts were estimated. © 2017 Elsevier Ltd

  • 4.
    Carvalho, Lara
    et al.
    Luleå University of Technology, Sweden.
    Furusjö, Erik
    Luleå University of Technology, Sweden.
    Ma, Chunyan
    Luleå University of Technology, Sweden.
    Ji, Xiaojan
    Luleå University of Technology, Sweden.
    Lundgren, Joakim
    Luleå University of Technology, Sweden ; International Institute for Applied Systems Analysis (IIASA), Austria.
    Hedlund, Jonas
    Luleå University of Technology, Sweden.
    Grahn, Mattias
    Luleå University of Technology, Sweden.
    Öhrman, Olov
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. IVL – Swedish Environmental Institute, Sweden ; .
    Wetterlund, Elisabeth
    Luleå University of Technology, Sweden ; International Institute for Applied Systems Analysis (IIASA), Austria.
    Alkali enhanced biomass gasification with in situ S capture and a novel syngas cleaning. Part 2: Techno-economic assessment2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 165, p. 471-482Article in journal (Refereed)
    Abstract [en]

    Previous research has shown that alkali addition has operational advantages in entrained flow biomass gasification and allows for capture of up to 90% of the biomass sulfur in the slag phase. The resultant low-sulfur content syngas can create new possibilities for syngas cleaning processes. The aim was to assess the techno-economic performance of biofuel production via gasification of alkali impregnated biomass using a novel gas cleaning system comprised of (i) entrained flow catalytic gasification with in situ sulfur removal, (ii) further sulfur removal using a zinc bed, (iii) tar removal using a carbon filter, and (iv) CO2 reduction with zeolite membranes, in comparison to the expensive acid gas removal system (Rectisol technology). The results show that alkali impregnation increases methanol production allowing for selling prices similar to biofuel production from non-impregnated biomass. It was concluded that the methanol production using the novel cleaning system is comparable to the Rectisol technology in terms of energy efficiency, while showing an economic advantage derived from a methanol selling price reduction of 2–6 €/MWh. The results showed a high level of robustness to changes related to prices and operation. Methanol selling prices could be further reduced by choosing low sulfur content feedstocks.

  • 5.
    Elliott, Douglas C.
    et al.
    Pacific Northwest National Laboratory, US.
    Meier, Dietrich
    Thünen Institute of Wood Research, Germany.
    Oasmaa, Anja
    VTT Technical Research Center of Finland, Finland.
    van De Beld, Bert
    BTG Biomass Technology Group BV, Netherlands.
    Bridgwater, Anthony V.
    Aston University, UK.
    Marklund, Magnus
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Results of the International Energy Agency Round Robin on Fast Pyrolysis Bio-oil Production2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 5, p. 5111-5119Article in journal (Refereed)
    Abstract [en]

    An international round robin study of the production of fast pyrolysis bio-oil was undertaken. A total of 15 institutions in six countries contributed. Three biomass samples were distributed to the laboratories for processing in fast pyrolysis reactors. Samples of the bio-oil produced were transported to a central analytical laboratory for analysis. The round robin was focused on validating the pyrolysis community understanding of production of fast pyrolysis bio-oil by providing a common feedstock for bio-oil preparation. The round robin included: distribution of three feedstock samples, hybrid poplar, wheat straw, and a blend of lignocellulosic biomasses, from a common source to each participating laboratory, preparation of fast pyrolysis bio-oil in each laboratory with the three feedstocks provided, and return of the three bio-oil products (minimum of 500 mL) with operational description to a central analytical laboratory for bio-oil property determination. The analyses of interest were CHN, S, trace element analysis, water, ash, solids, pyrolytic lignin, density, viscosity, carboxylic acid number, and accelerated aging of bio-oil. In addition, an effort was made to compare the bio-oil components to the products of analytical pyrolysis through gas chromatography/mass spectrometry (GC/MS) analysis. The results showed that clear differences can occur in fast pyrolysis bio-oil properties by applying different process configurations and reactor designs in small scale. The comparison to the analytical pyrolysis method suggested that pyrolysis (Py)-GC/MS could serve as a rapid qualitative screening method for bio-oil composition when produced in small-scale fluid-bed reactors. Gel permeation chromatography was also applied to determine molecular weight information. Furthermore, hot vapor filtration generally resulted in the most favorable bio-oil product, with respect to water, solids, viscosity, and carboxylic acid number. These results can be helpful in understanding the variation in bio-oil production methods and their effects on bio-oil product composition.

  • 6.
    Garami, Attila
    et al.
    University of Miskolc, Hungary.
    Toth, Pal
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Csordas, Bernadett
    University of Miskolc, Hungary.
    Palotas, Arpad
    University of Miskolc, Hungary.
    Reaction zone monitoring in biomass combustion2018In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 74, p. 95-106Article in journal (Refereed)
    Abstract [en]

    In this work we demonstrate the utilization of a machine vision-based combustion monitoring system in biomass combustion. The proposed system monitored the location of the reaction zone in a 3 MW, grate-fired biomass boiler operated at varying loads and with fluctuating fuel quality. The system can help guarantee equal primary air supply to different regions of the grate and avoid the elutriation of fly ash by providing information on the location of the reaction zone. Strong correlation was found between the reaction zone boundary location and most process parameters, indicating that the location of the reaction zone can be a useful metric in monitoring and control by providing supplementary measurements to already existing monitoring to avoid over-emissions and improve economics.

  • 7.
    Göktepe, Burak
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Umeki, Kentaro
    Luleå University of Technology, Sweden.
    Hazim, Ammar
    Luleå University of Technology, Sweden.
    Lundström, Staffan
    Luleå University of Technology, Sweden.
    Gebart, Rikard
    Luleå University of Technology, Sweden.
    Soot reduction in an entrained flow gasifier of biomass by active dispersion of fuel particles2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, 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. © 2016.

  • 8.
    Holmgren, Per
    et al.
    Umeå University, Sweden.
    Wagner, David R.
    Umeå University, Sweden.
    Strandberg, Anna
    Umeå University, Sweden.
    Molinder, Roger
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Umeki, Kentaur
    Luleå University of Technology, Sweden.
    Broström, Markus
    Umeå University, Sweden.
    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.

  • 9.
    Johansson, Ann-Christine
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Iisa, Kristiina
    National Renewable Energy Laboratory, US.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Ben, Haoxi
    Renewable Energy Laboratory, US.
    Pilath, Heidi
    Renewable Energy Laboratory, US.
    Deutch, Steve
    Renewable Energy Laboratory, US.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Öhrman, Olov G.W.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Fractional condensation of pyrolysis vapors produced from Nordic feedstocks in cyclone pyrolysis2017In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 123, p. 244-254Article in journal (Refereed)
    Abstract [en]

    Pyrolysis oil is a complex mixture of different chemical compounds with a wide range of molecular weights and boiling points. Due to its complexity, an efficient fractionation of the oil may be a more promising approach of producing liquid fuels and chemicals than treating the whole oil. In this work a sampling system based on fractional condensation was attached to a cyclone pyrolysis pilot plant to enable separation of the produced pyrolysis vapors into five oil fractions. The sampling system was composed of cyclonic condensers and coalescing filters arranged in series. The objective was to characterize the oil fractions produced from three different Nordic feedstocks and suggest possible applications. The oil fractions were thoroughly characterized using several analytical techniques including water content; elemental composition; heating value, and chemical compound group analysis using solvent fractionation, quantitative 13C NMR and 1H NMR and GC x GC − TOFMS. The results show that the oil fractions significantly differ from each other both in chemical and physical properties. The first fractions and the fraction composed of aerosols were highly viscous and contained larger energy-rich compounds of mainly lignin-derived material. The middle fraction contained medium-size compounds with relatively high concentration of water, sugars, alcohols, hydrocarbonyls and acids and finally the last fraction contained smaller molecules such as water, aldehydes, ketones and acids. However, the properties of the respective fractions seem independent on the studied feedstock types, i.e. the respective fractions produced from different feedstock are rather similar. This promotes the possibility to vary the feedstock depending on availability while retaining the oil properties. Possible applications of the five fractions vary from oil for combustion and extraction of the pyrolytic lignin in the early fractions to extraction of sugars from the early and middle fractions, and extraction of acids and aldehydes in the later fractions.

  • 10.
    Johansson, Ann-Christine
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Öhrman, Olov
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Jilvero, Henrik
    Stena Metall, Sweden.
    Co-pyrolysis of woody biomass and plastic waste in both analytical and pilot scale2018In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 134, p. 102-1113Article in journal (Refereed)
    Abstract [en]

    Earlier studies show that co-pyrolysis of biomass and plastics can improve the quantity and quality of the produced pyrolysis oil compared to pyrolysis of the separate feedstocks. In this work three relevant plastic wastes; paper reject, shredder light fraction and cable plastics; were evaluated together with woody biomass (stem wood from spruce and pine) using analytical pyrolysis, Py-GC–MS/FID. One verification experiment was also conducted in a cyclone pyrolyser pilot plant at industrially relevant conditions. The addition of plastic waste to woody biomass pyrolysis was found to significantly affect the composition and properties of the produced pyrolysis products. In analytical pyrolysis experiments, positive synergetic effects were observed in the co-pyrolysis of paper reject and cable plastics together with the stem wood. The yield of reactive oxygenated compounds (ketones, aldehydes and acids) was suppressed while more stable alcohols and esters were promoted. The formation of hydrocarbons was also promoted in the co-pyrolysis of plastics from paper reject and stem wood. The results from the analytical pyrolysis were partly verified in the pilot scale experiment by co-pyrolysing stem wood and paper reject. However, the co-pyrolysis also affected other parameters that cannot be detected in analytical pyrolysis such as higher acidity and viscosity of the oil which highlights the need for undertaking experiments at different scales. The product yields in pilot scale were about the same for the co-pyrolysis case as for pure stem wood. However, a high volatile content of the solid product indicated that the process conditions can be further optimized for co-pyrolysing cases.

  • 11.
    Lestander, Torbjörn A.
    et al.
    SLU Swedish University of Agricultural Sciences, Sweden.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Öhrman, Olov
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Thyrel, Mikael
    SLU Swedish University of Agricultural Sciences, Sweden.
    Characterization of fast pyrolysis bio-oil properties by near-infrared spectroscopic data2018In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 133, p. 9-15Article in journal (Refereed)
    Abstract [en]

    Pyrolysis transforms bulky and heterogeneous lignocellulosic biomass into more easily-handled oils that can be upgraded into bio-based transportation fuels. Existing systems for monitoring pyrolysis processes and characterizing their products rely on slow and time-consuming wet chemical analyses. On-line near-infrared (NIR) spectroscopy could potentially replace such analyses, providing real-time data and reducing costs. To test the usefulness of NIR methods in characterizing pyrolysis oils and processes, biomass from conifers, Salix, and reed canary grass was milled and pyrolyzed at 675, 750, and 775 °C. Two separate pyrolytic fractions (aerosol and condensed) were produced in each experiment, and NIR spectra were collected for each fraction. Multivariate modelling of the resulting data clearly showed that the samples’ NIR spectra could be used to accurately predict important properties of the pyrolysis oils such as their energy values, main organic element (C, H and O) contents, and water content. The spectra also contained predictive information on the samples’ origins, fraction, and temperature treatment, demonstrating the potential of on-line NIR techniques for monitoring pyrolytic production processes and characterizing important properties of pyrolytic oils from lignocellulosic biomass.

  • 12.
    Pedersen, Thomas Helmer
    et al.
    Aalborg University, Denmark.
    Jensen, Claus Uhrenholt
    Steeper Energy ApS, Denmark.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Rosendahl, Lasse Aistrup
    Aalborg University, Denmark.
    Full characterization of compounds obtained from fractional distillation and upgrading of a HTL biocrude2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 202, p. 408-419Article in journal (Refereed)
    Abstract [en]

    Biocrude from hydrothermal liquefaction of biomass provides a sustainable source from which to produce chemicals and fuels. However, just as for fossil crude, the chemical complexity of the biocrude impedes the characterization and hence identification of market potentials for both biocrude and individual fractions. Here, we reveal how fractional distillation of a biocrude can leverage biocrude characterization beyond state-of-the-art and uncover the full biocrude potential. By distillation combined with detailed individual analysis of the distillate fractions and distillation residue, more than 85% of the total biocrude composition is determined. It is demonstrated that a total mass fraction of 48.2% of the biocrude is volatile below 350 °C, comprising mainly value-added marketable ketones, oxygenated aromatics and prospective liquid fuel candidates, which are easily fractionated according to boiling points. Novel, high resolution pyr-GCxGC-MS analysis of the residue indicates a high molecular weight aromatic structure, valuable for bio-materials production or for further processing into fuels. The distillate fractions are mildly hydrotreated to show the fuel and chemical precursor potential of the volatile components. This results in the formation of mainly hydrocarbons and added-value phenolics. This work takes a significant step by going beyond the biocrude as an intermediate bulk energy product and addressing actual applications and pathways to these.

  • 13.
    Persson, H.
    et al.
    KTH Royal Institute of Technology, Sweden.
    Han, T.
    KTH Royal Institute of Technology, Sweden.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Xia, W.
    KTH Royal Institute of Technology, Sweden.
    Evangelopoulos, P.
    KTH Royal Institute of Technology, Sweden.
    Yang, W.
    KTH Royal Institute of Technology, Sweden.
    Fractionation of liquid products from pyrolysis of lignocellulosic biomass by stepwise thermal treatment2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 154, p. 346-351Article in journal (Refereed)
    Abstract [en]

    The thermal properties of cellulose, hemicellulose and lignin can be utilized to improve the characteristics of pyrolysis liquids. In this study, a concept of stepwise pyrolysis to fractionate the liquid based on the thermal properties of the biomass constituents was investigated. Lignocellulosic biomass was thermally treated in two steps: 200–300 °C followed by 550 °C. Derived liquids were studied for GC/MS analysis, water content, acid concentration and a solvent extraction method. Pyrolytic liquid derived from 550 °C after treatment at lower temperatures have a higher relative composition of phenolic compounds compared to one-step pyrolysis (increased from 58 to 90% of GC/MS peak area). Also, compounds known to promote aging, such as acids and carbonyl compounds, are derived at lower temperatures which may suppress aging in the liquid derived downstream at 550 °C. For liquids derived at 550 °C, the total acid number was reduced from 125 in one-step treatment to 14 in two-step treatment. Overall, no significant difference in the total liquid yield (sum of the liquids derived in separated treatments) nor any variations in their collective composition compared to one-step treatment at 550 °C was observed, i.e. stepwise pyrolysis can be utilized for direct fractionation of pyrolytic vapors.

  • 14.
    Sefidari, Hamid
    et al.
    Luleå University of Technology, Sweden.
    Lindblom, Bo
    Luleå University of Technology, Sweden ; LKAB, Sweden.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Nordin, Lars Olof
    LKAB, Sweden.
    Lennartsson, Andreas
    Luleå University of Technology, Sweden.
    Mouzon, Johanne
    Luleå University of Technology, Sweden.
    Bhuiyan, Iftehkar
    Luleå University of Technology, Sweden.
    Öhman, Marcus
    Luleå University of Technology, Sweden.
    The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace. Part II: Thermochemical equilibrium calculations and viscosity estimations2018In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 180, p. 189-206Article in journal (Refereed)
    Abstract [en]

    Fly ash particles from the combustion of solid-fuels together with disintegrated particles arising from iron-ore pellets result in accumulation of deposits on the refractory linings of the grate-kiln induration machine during the iron-ore pelletizing process. The deposits amass in the high-temperature regions of the induration furnace thus disturbing the flow of gas and pellets. Therefore, to tackle the above-mentioned issues, an understanding of deposit formation mechanism is of crucial importance. This study was conducted with the objective of addressing the effect of disintegrated iron-ore pellet dust on deposit formation and the mechanisms behind deposition (slagging) in the grate-kiln process. A comprehensive set of experiments was conducted in a 0.4 MW pilot-scale pulverized-coal- fired furnace where three different scenarios were considered as follows; Case 1 (reference case): Coal was combusted without the presence of pellet dust. Case 2: Natural gas was combusted together with simultaneous addition of pellet dust to the gas stream. Case 3: Coal was combusted together with the addition of pellet dust simulating the situation in the large-scale setup. Fly ash particles and short-term deposits were characterized and deposition was addressed in Part I of this study. In light of the experimental observations (Part I) and the thermochemical equilibrium calculations (Part II), a scheme of ash transformation during the iron-ore pelletizing process was proposed. The dissolution of hematite particles into the Ca-rich-aluminosilicate melt (from the coal-ash constituents) decreased the viscosity and resulted in the formation of stronger (heavily sintered) deposits. Overall, this pilot-scale work forms part of a wider study which aims at deepening the understanding of ash transformation phenomena during the large-scale pelletizing process.

  • 15.
    Sefidari, Hamid
    et al.
    Luleå University of Technology, Sweden.
    Lindblom, Bo
    Luleå University of Technology, Sweden.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Nordin, Lars-Olof
    Luossavaara-Kiirunavaara Aktiebolag (LKAB), Sweden.
    Mouzon, Johanna
    Luleå University of Technology, Sweden.
    Bhuiyan, Iftekhar Uddin
    Luleå University of Technology, Sweden.
    Öhman, Marcus
    Luleå University of Technology, Sweden.
    The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace. Part I: Characterization of process gas particles and deposits2018In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 177, p. 283-298Article in journal (Refereed)
    Abstract [en]

    To initiate the elucidation of deposit formation during the iron-ore pelletization process, a comprehensive set of experiments was conducted in a 0.4 MW pilot-scale pulverized-coal-fired furnace where three different scenarios were considered as follows; Case 1 (reference case): Coal was combusted without the presence of pellet dust. Case 2: Natural gas was combusted together with simultaneous addition of pellet dust to the gas stream. Case 3: Coal was combusted together with the addition of pellet dust simulating the situation in the large-scale grate-kiln setup. Particles and deposits were sampled from 3 positions of different temperature via a water-cooled sampling probe. Three distinct fragmentation modes were identified based on the aerodynamic particle diameter (Dp). The fine mode: Particles with 0.03 < Dp < 0.06 μm. The first fragmentation mode: Particles with 1 < Dp < 10 μm. The second fragmentation mode: Coarse particles (cyclone particles, Dp > 10 μm). A transition from a bimodal PSD (particle size distribution) to a trimodal PSD was observed when pellet dust was added (Case 3) and consequently the elemental bulk composition of the abovementioned modes was changed. The most extensive interaction between pellet dust and coal-ash particles was observed in the coarse mode where a significant number of coal ash globules were found attached to the surface of the hematite particles. The morphology of the sharp-edged hematite particles was changed to smooth-edged round particles which proved that hematite particles must have interacted with the surrounding aluminosilicate glassy phase originating from the coal ash. The short-term deposits collected during coal combustion (Case 1) were highly porous in contrast to the high degree of sintering observed in the experiments with pellet dust addition (Case 3) which is attributed to the dissolution of hematite particles in the aluminosilicate glassy phase. The results suggest that pellet dust itself (Case 2) has low slagging tendency, independent of temperature. However, when coal-ash is present (Case 3), auxiliary phases are added such that tenacious particles are formed and slagging occurs.

  • 16.
    Sepman, Alexey
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Ögren, Yngve
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Qu, Zhechao
    Umeå University, Sweden.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Schmidt, Florian M.
    Umeå University, Sweden.
    Real-time in situ multi-parameter TDLAS sensing in the reactor core of an entrained-flow biomass gasifier2017In: Proceedings of the Combustion Institute, ISSN 1540-7489, E-ISSN 1873-2704, Vol. 36, no 3, p. 4541-4548Article in journal (Refereed)
    Abstract [en]

    Tunable diode laser absorption spectroscopy (TDLAS) was employed to measure several important process parameters at two different locations inside the reactor of an atmospheric air-blown 0.1 MW biomass gasifier. Direct TDLAS at 2298 nm was employed for CO and water calibration-free scanned wavelength modulation spectroscopy at 1398 nm for H2O and gas temperature and direct TDLAS at 770 nm for gaseous elemental potassium K(g) under optically thick conditions which correspond the first in situ measurements of K(g) and temperature in a reactor core and in biomass gasification respectively. Actual average temperatures in the reactor core were significantly higher than the uncorrected thermocouple measurements in the gas stream. The CO concentrations at the lower optical access port were comparable to those obtained by GC at the exhaust. In gasification mode similar H2O values were obtained by the two different TDLAS instruments. The reaction time was faster for peat than for stem wood.

  • 17.
    Sepman, Alexey
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Ögren, Yngve
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Optical techniques for characterizing the biomass particle flow fluctuations in lab- and pilot-scale thermochemical systems2017In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 313, p. 129-134Article in journal (Refereed)
    Abstract [en]

    The work demonstrates the performance of the optical extinction technique for real-time diagnostics of the fluctuations in biomass particle flows. The online measurements of fluctuations of density were used to determine the biomass particle mass flow fluctuations. Biomass flows were produced using laboratory biomass particle feeder (mass flux up to 10 g/min) and the hopper-screw feeding system of the pilot-scale entrained flow rector, mass flux up to 500 g/min, located at SP ETC in Piteå. The experiments showed that the time-averaged extinction appeared to be linearly related to the real particle mass flow. The relatively fast variations in biomass feeding rates measured using the extinction technique were confirmed by fast balance measurements (in laboratory feeder experiments) and by real-time tunable diode laser CO and H2O concentrations measured in the reactor core of the entrained flow gasifier.

  • 18.
    Sjöblom, Magnus
    et al.
    Luleå University of Technology, Sweden.
    Risberg, Per
    KTH Royal Institute of Technology, Sweden.
    Filippova, Alfia
    Luleå University of Technology, Sweden.
    Öhrman, Olov G.W.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Rova, Ulrika
    Luleå University of Technology, Sweden.
    Christakopoulos, Paul
    Luleå University of Technology, Sweden.
    In Situ Biocatalytic Synthesis of Butyl Butyrate in Diesel and Engine Evaluations2017In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 9, no 24, p. 4529-4537Article in journal (Refereed)
    Abstract [en]

    Blending petroleum fuels with biofuels is likely to become increasingly important over the years to come. Butyl butyrate has promising characteristics as a blend component in diesel and can be synthesized by lipase-catalyzed esterification of 1-butanol and butyric acid, which both can be derived from fermentation technologies. In the current study, the enzyme load and reaction temperature were optimized for the production of butyl butyrate with Novozyme 435 (immobilized Candida antarctica lipase B) directly in diesel at a substrate concentration of 1 m using a molar ratio of 1:1 between n-butanol and butyric acid. Optimum conditions were found by using a central composite design at an enzyme load of 12 % of substrate weight and a temperature of 57 °C, giving 90 % yield conversion in 30 min, corresponding to a butyl butyrate productivity of 1.8 mol L−1 h−1. Diesel blended with 5, 10, and 30 % butyl butyrate was tested in a heavy-duty diesel engine under two load cases. The ignition properties of the blended fuels were very similar to pure diesel, making butyl butyrate an interesting diesel substitute. The emission analysis demonstrated lower soot and CO emissions, similar hydrocarbons levels and slightly increased NOx levels compared with using pure diesel. The high activity of lipase in diesel and the compatibility between diesel and butyl butyrate opens up the possibility to develop fuel blending systems where the synthesis of the blend-in component occurs directly in the fuel.

  • 19.
    Sophonrat, Nanta
    et al.
    KTH Royal Institute of Technology, Sweden.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Johansson, Ann-Christine
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Yang, Weihong
    KTH Royal Institute of Technology, Sweden.
    Co-pyrolysis of Mixed Plastics and Cellulose: An Interaction Study by Py-GC×GC/MS2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 10, p. 11078-11090Article in journal (Refereed)
    Abstract [en]

    Understanding of the interaction between cellulose and various plastics is crucial for designing waste-to-energy processes. In this work, co-pyrolysis of polystyrene (PS) and cellulose was performed in a Py-GC×GC/MS system at 450-600 °C with ratios 70:30, 50:50, and 30:70. Polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET) were then added to the mixture with different ratios. It was found that co-pyrolysis of PS and cellulose promotes the formation of aromatic products with a large increase in the yield of ethylbenzene as compared to the calculated value from individual feedstock. This indicates interactions between cellulose and PS pyrolysis products. Observations from experiments including more than one type of plastics indicate that the interactions between different plastics are more pronounced than the interaction between plastics and cellulose.

  • 20.
    Sophonrat, Nanta
    et al.
    KTH Royal Institute of Technology, Sweden.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Zaini, Ilman N.
    KTH Royal Institute of Technology, Sweden.
    Yang, Weihong
    KTH Royal Institute of Technology, Sweden.
    Stepwise pyrolysis of mixed plastics and paper for separation of oxygenated and hydrocarbon condensates2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 229, p. 314-325Article in journal (Refereed)
    Abstract [en]

    Mixed plastics and papers are two of the main fractions in municipal solid waste which is a critical environmental issue today. Recovering energy and chemicals from this waste stream by pyrolysis is one of the favorable options to achieve a circular economy. While pyrolysis products from plastics are mainly hydrocarbons, pyrolysis products from paper/biomass are highly oxygenated. The different nature of the two pyrolysis products results in different treatments and applications as well as economic values. Therefore, separation of these two products by multi-step pyrolysis based on their different decomposition temperatures could be beneficial for downstream processes to recover materials, chemicals and/or energy. In this work, stepwise pyrolysis of mixed plastics and paper waste was performed in a batch type fixed bed reactor using two different pyrolysis temperatures. Neat plastic materials (polystyrene, polyethylene) and cellulose mixtures were used as starting materials. Then, the same conditions were applied to a mixed plastics and paper residue stream derived from paper recycling process. The condensable products were analyzed by GC/MS. It was found that pyrolysis temperatures during the first and second step of 350 and 500 °C resulted in a better separation of the oxygenated and hydrocarbon condensates than when a lower pyrolysis temperature (300 °C) was used in the first step. The products from the first step were derived from cellulose with some heavy fraction of styrene oligomers, while the products from the second step were mainly hydrocarbons derived from polystyrene and polyethylene. This thus shows that stepwise pyrolysis can separate the products from these materials, although with some degree of overlapping products. Indications of interaction between PS and cellulose during stepwise pyrolysis were observed including an increase in char yield, a decrease in liquid yield from the first temperature step and changes in liquid composition, compared to stepwise pyrolysis of the two materials separately. A longer vapor residence time in the second step was found to help reducing the amount of wax derived from polyethylene. Results from stepwise pyrolysis of a real waste showed that oxygenated and acidic products were concentrated in the liquid from the first step, while the product from the second step contained a high portion of hydrocarbons and had a low acid number.

  • 21.
    Strandberg, Anna
    et al.
    Umeå University, Sweden.
    Holmgren, Per
    Umeå University, Sweden.
    Wagner, David R.
    Umeå University, Sweden.
    Molinder, Roger
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Umeki, Kentaro
    Luleå University of Technology, Sweden.
    Broström, Markus
    Umeå University, Sweden.
    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.

  • 22.
    Szamosi, Zoltan
    et al.
    University of Miskolc, Hungary.
    Toth, Pal
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Koos, Tamas
    University of Miskolc, Hungary.
    Baranyai, Viktor Zsolt
    Bay Zoltán Nonprofit Limited for Applied Research, Hungary.
    Szepesi, Gabor L.
    University of Miskolc, Hungary.
    Simenfalvi, Zoltan
    University of Miskolc, Hungary.
    Explosion Characteristics of Torrefied Wheat Straw, Rape Straw, and Vine Shoots Fuels2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 11, p. 12192-12199Article in journal (Refereed)
    Abstract [en]

    Torrefaction is a method for upgrading raw biomass to produce solid fuels that exhibit higher energy density relative to that of the raw material. In countries that produce significant amounts of agricultural residues, torrefaction may facilitate the utilization of waste in the energy sector by adding value to the raw fuel and opening pathways for new applications. In typical scenarios for utilization as fuel, both the raw and torrefied materials are stored in granular form. Dependent upon the properties of the granular material, the risk of dust explosion may be significant. Torrefaction changes the physical and chemical properties of the biomass and, therefore, affect explosion risk and severity. This work investigates the dust explosion characteristics of raw and torrefied agricultural wastes typically produced in Central European countries. The objective is to provide a characterization of these fuels in terms of explosion properties and make recommendations on storage design and safety. Three residues were studied: wheat straw, rape straw, and vine shoots. The samples were characterized in terms of their particle size, proximate and ultimate compositions, calorific properties, thermogravimetric behavior, and standard explosion characteristics. Torrefaction increased the explosivity of all three residues. Of the three samples, wheat straw was the least explosive, which is explained by the lowest amount of open cellular pores generated during torrefaction. Scanning electron microscopy imaging and thermogravimetry results suggested that the amount of open pores is the most significant contributor to the increase of explosivity caused by torrefaction, as opposed to increasing brittleness and fragmentation. For plants switching from using raw residues to torrefied fuels, the required area of typical explosion panels increases by 18-21% in the case of wheat and rape straw and by 26-30% in the case of vine shoots.

  • 23.
    Toth, Pal
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Vikström, Therese
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Molinder, Roger
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Structure of carbon black continuously produced from biomass pyrolysis oil2018In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270Article in journal (Refereed)
    Abstract [en]

    Renewable-based carbon black was produced using pyrolysis oil derived from pine and spruce stem wood as feedstock in a continuous, high-temperature spray process. The particle size, micro- and nanostructure of the carbon black particles were investigated using High Resolution Transmission Electron Microscopy. The effect of process parameters on the structural properties of the product was studied. Conditions that yielded products structurally similar to commercial carbon black were identified. The results indicate that biomass pyrolysis oil can be used as a feedstock to produce renewable-based carbon black in a continuous process that is flexible and scalable. The structural properties of the products depended on process temperature and were consistent with those of commercial carbon black.

  • 24.
    Toth, Pal
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    ֖gren, Yngve
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Vikström, Therese
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Gren, Per
    Luleå university of technology, Sweden.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Spray combustion of biomass fast pyrolysis oil: Experiments and modeling2019In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 237, p. 580-591Article in journal (Refereed)
    Abstract [en]

    In this work, we are the first to report a detailed comparison between the predictions of a current Computational Fluid Dynamics (CFD) model for describing Fast Pyrolysis Oil (FPO) spray combustion and results from a laboratory-scale experiment. The objectives were to assess the predictive power of the CFD model, evaluate its usefulness in a numerical optimization scenario and characterize the spray flame. The spray flame was produced by using an air-assist atomizer piloted by a CH4/air flat-flame. Pyrolysis oil from a cyclone fast pyrolysis plant was combusted. The flame was characterized by using two-color pyrometry, Tunable Diode Laser Absorption Spectroscopy and high-magnification shadowgraphy. Overall, the assessed model correctly predicted flame structure and seemed appropriate for engineering applications, but lacked predictive power in estimating droplet size distributions. Numerical results were the most sensitive to variations in the initial droplet size distribution; however, seemed robust to changes in the multicomponent fuel formulation. Several conclusions were drawn regarding FPO spray combustion itself; e.g., the amount of produced soot in the flames was very low and droplets exhibited microexplosion behavior in a characteristic size-shape regime. 

  • 25.
    Tóth, Pal
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Garami, Attilla
    University of Miskolc, Hungary.
    Csordás, Bernadett
    University of Miskolc, Hungary.
    Image-based deep neural network prediction of the heat output of a step-grate biomass boiler2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 200, p. 155-169Article in journal (Refereed)
    Abstract [en]

    This work investigates the usage of deep neural networks for predicting the thermal output of a 3 MW, grate-fired biomass boiler, based on routinely measured operating parameters and real-time flame imaging. It is hypothesized that flame imaging can provide information regarding the quasi-instantaneous state of combustion, therefore supplementing conventional measurements that generally produce lagging feedback. A deep neural network-based, continuous multistep-ahead prediction scheme was proposed and evaluated by using operational and image data collected through extensive campaigns. It was found that flame imaging increases the accuracy of predictions compared to those obtained by only using operational data. The complexity of biomass combustion was well captured by the proposed deep neural network; furthermore, the deep architecture produced better predictions than shallower ones. The proposed system can reliably predict output water temperatures with errors up to ±1 °C, up to approximately 30 min ahead of the current time.

  • 26.
    Wiinikka, Henrik
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Johansson, Ann-Christine
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Öhrman, Olov G.W.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Fate of inorganic elements during fast pyrolysis of biomass in a cyclone reactor2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 203, p. 537-547Article in journal (Refereed)
    Abstract [en]

    In order to reduce ash related operational problem and particle emissions during pyrolysis oil combustion it is important to produce pyrolysis oil with very low concentration of inorganics. In this paper, the distribution of all major inorganic elements (S, Si, Al, Ca, Fe, K, Mg, Mn, Na, P, Ti and Zn) in the pyrolysis products (solid residue and two fractions of pyrolysis oil) was investigated during pyrolysis of stem wood, bark, forest residue, salix and reed canary grass. The raw materials were pyrolysed in a cyclone reactor and the produced pyrolysis oils were recovered as two oil fractions, a condensed fraction and an aerosol fraction. The inorganic composition of the ingoing raw material, the solid residue and the two pyrolysis oil fractions were analysed with inductively coupled plasma spectrometry techniques. All major inorganic elements, except sulphur, were concentrated in the solid residue. A significant amount of sulphur was released to the gas phase during pyrolysis. For zinc, potassium and iron about 1–10 wt% of the ingoing amount, depending on the raw material, was found in the pyrolysis oil. For the rest of the inorganics, generally less than 1 wt% of the ingoing amount was found in the pyrolysis oil. There were also differences in distribution of inorganics between the condensed and the aerosol oil fractions. The easily volatilized inorganic elements such as sulphur and potassium were found to a larger extent in the aerosol fraction, whereas the refractory elements were found to a larger extent in the condensed fraction. This implies that oil fractionation can be a method to produce oil fractions with different inorganic concentrations which thereafter can be used in different technical applications depending on their demand on the inorganic composition of the pyrolysis oil.

  • 27.
    Wiinikka, Henrik
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technlogy, Sweden.
    Vikström, Therese
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wennebro, Jonas
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Toth, Pal
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Pulverized Sponge Iron, a Zero-Carbon and Clean Substitute for Fossil Coal in Energy Applications2018In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 32, no 9, p. 9982-9989Article in journal (Refereed)
    Abstract [en]

    The direct combustion of recyclable metals has the potential to become a zero-carbon energy production alternative, much needed to alleviate the effects of global climate change caused by the increased emissions of the greenhouse gas CO2. In this work, we show that the emission of CO2 is insignificant during the combustion of pulverized sponge iron compared to that of pulverized coal combustion. The emissions of the other harmful pollutants NOx and SO2 were 25 and over 30 times lower, respectively, than in the case of pulverized coal combustion. Furthermore, 96 wt % of the solid combustion products consisted of micrometer-sized, solid or hollow hematite (α-Fe2O3) spheres. The remaining 4 wt % of products was maghemite (Î-Fe2O3) nanoparticles. According to thermodynamic calculations, this product composition implies near-complete combustion, with a conversion above 98%. The results presented in this work strongly suggest that sponge iron is a clean energy carrier and may become a substitute to pulverized coal as a fuel in existing or newly designed industrial systems.

  • 28.
    Wiinikka, Henrik
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wennebro, Jonas
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Gullberg, Marcus
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Pettersson, Esbjörn
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Weiland, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Pure oxygen fixed-bed gasification of wood under high temperature (>1000 °C) freeboard conditions2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 191, p. 153-162Article in journal (Refereed)
    Abstract [en]

    In this paper, the performance (syngas composition, syngas production and gasification efficiency) of an 18 kW atmospheric fixed bed oxygen blown gasifier (FOXBG) with a high temperature (>1000 °C) freeboard section was compared to that of a pressurized (2–7 bar) oxygen blown entrained flow biomass gasifier (PEBG). Stem wood in the form of pellets (FOXBG) or powder (PEBG) was used as fuel. The experimentally obtained syngas compositions, syngas production rates and gasification efficiencies for both gasification technologies were similar. Efficient generation of high quality syngas (in terms of high concentration and yield of CO and H2 and low concentration and yield of CH4, heavier hydrocarbons and soot) is therefore not specific to the PEBG. Instead, efficient gasification seems to be linked to high reactor process temperatures that can also be obtained in a FOXBG. The high quality of the syngas produced in the FOXBG from fuel pellets is promising, as it suggests that in the future, much of the cost associated with milling the fuel to a fine powder will be avoidable. Furthermore, it is also implied that feedstocks that are nearly impossible to pulverize can be used as un-pretreated fuels in the FOXBG.

  • 29.
    Winikka, Henrik
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Toth, Pal
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Jansson, Kjell
    Stockholm University, Sweden.
    Molinder, Roger
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Broström, Markus
    Umeå University, Sweden.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Lighty, JoAnn S.
    University of Utah, USA.
    Weiland, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Particle formation during pressurized entrained flow gasification of wood powder: Effects of process conditions on chemical composition, nanostructure, and reactivity2018In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 189, p. 1339-1351Article in journal (Refereed)
    Abstract [en]

    The influence of operating condition on particle formation during pressurized, oxygen blown gasification of wood powder with an ash content of 0.4 wt% was investigated. The investigation was performed with a pilot scale gasifier operated at 7 bar(a). Two loads, 400 and 600 kW were tested, with the oxygen equivalence ratio (λ) varied between 0.25 and 0.50. Particle concentration and mass size distribution was analyzed with a low pressure cascade impactor and the collected particles were characterized for morphology, elemental composition, nanostructure, and reactivity using scanning electron microscopy/high resolution transmission electron microscopy/energy dispersive spectroscopy, and thermogravimetric analysis. In order to quantify the nanostructure of the particles and identify prevalent sub-structures, a novel image analysis framework was used. It was found that the process temperature, affected both by λ and the load of the gasifier, had a significant influence on the particle formation processes. At low temperature (1060 °C), the formed soot particles seemed to be resistant to the oxidation process; however, when the oxidation process started at 1119 °C, the internal burning of the more reactive particle core began. A further increase in temperature (> 1313 °C) lead to the oxidation of the less reactive particle shell. When the shell finally collapsed due to severe oxidation, the original soot particle shape and nanostructure also disappeared and the resulting particle could not be considered as a soot anymore. Instead, the particle shape and nanostructure at the highest temperatures (> 1430 °C) were a function of the inorganic content and of the inorganic elements the individual particle consisted of. All of these effects together lead to the soot particles in the real gasifier environment having less and less ordered nanostructure and higher and higher reactivity as the temperature increased; i.e., they followed the opposite trend of what is observed during laboratory-scale studies with fuels not containing any ash-forming elements and where the temperature was not controlled by λ.

  • 30.
    Ögren, Yngve
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Gullberg, Marcus
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wennebro, Jonas
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Toth, Pal
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Influence of oxidizer injection angle on the entrained flow gasification of torrefied wood powder2018In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 181, p. 8-17Article in journal (Refereed)
    Abstract [en]

    In the present work, 5 different axisymmetric burners with different directions of the oxidizer inlets were experimentally tested during oxygen blown gasification of torrefied wood powder. The burners were evaluated under two different O2/fuel ratios at a thermal power of 135 kWth, based on the heating value of torrefied wood powder. The evaluation was based on both conventional methods such as gas chromatography measurements and thermocouples and in-situ measurements using Tunable Diode Laser Absorption Spectroscopy. It was shown that changes in the near burner region influence the process efficiency significantly. Changing the injection angle of the oxidizer stream to form a converging oxidizer jet increased process efficiency by 20%. Besides increased process efficiency, it was shown that improvements in burner design also influence carbon conversion and hydrocarbon production. The burner with the best performance also produced less CH4 and achieved the highest carbon conversion. The effect of generating swirl via rotating the oxidizer jet axes was also investigated. Swirl broadened or removed the impingement area between the fuel and oxidizer jets, however resulting in differences in performance within the measurement uncertainty.

  • 31.
    Ögren, Yngve
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology,Sweden.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Qu, Zhechau
    Umeå University, Sweden.
    Schmidt, Florian M.
    Umeå University, Sweden.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Comparison of Measurement Techniques for Temperature and Soot Concentration in Premixed, Small-Scale Burner Flames2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 10, p. 11328-11336Article in journal (Refereed)
    Abstract [en]

    Optical and intrusive measurement techniques for temperature and soot concentration in hot reacting flows were tested on a small-scale burner in fuel-rich, oxygen-enriched atmospheric flat flames produced to simulate the environment inside an entrained flow reactor. The optical techniques comprised two-color pyrometry (2C-PYR), laser extinction (LE), and tunable diode laser absorption spectroscopy (TDLAS), and the intrusive methods included fine-wire thermocouple thermometry (TC) and electrical low pressure impactor (ELPI) particle analysis. Vertical profiles of temperature and soot concentration were recorded in flames with different equivalence and O2/N2 ratios. The 2C-PYR and LE data were derived assuming mature soot. Gas temperatures up to 2200 K and soot concentrations up to 3 ppmv were measured. Close to the burner surface, the temperatures obtained with the pyrometer were up to 300 K higher than those measured by TDLAS. Further away from the burner, the difference was within 100 K. The TC-derived temperatures were within 100 K from the TDLAS results for most of the flames. At high signal-to-noise ratio and in flame regions with mature soot, the temperatures measured by 2C-PYR and TDLAS were similar. The soot concentrations determined with 2C-PYR were close to those obtained with LE but lower than the ELPI results. It is concluded that the three optical techniques have good potential for process control applications in combustion and gasification processes. 2C-PYR offers simpler installation and 2D imaging, whereas TDLAS and LE provide better accuracy and dynamic range without calibration procedures.

  • 32.
    Ögren, Yngve
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Toth, Pal
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Garami, Attila
    University of Miskolc, Hungary.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Development of a vision-based soft sensor for estimating equivalence ratio and major species concentration in entrained flow biomass gasification reactors2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 226, p. 450-460Article in journal (Refereed)
    Abstract [en]

    A combination of image processing techniques and regression models was evaluated for predicting equivalence ratio and major species concentration (H2, CO, CO2 and CH4) based on real-time image data from the luminous reaction zone in conditions and reactors relevant to biomass gasification. Two simple image pre-processing routines were tested: reduction to statistical moments and pixel binning (subsampling). Image features obtained by using these two pre-processing methods were then used as inputs for two regression algorithms: Gaussian Process Regression and Artificial Neural Networks. The methods were evaluated by using a laboratory-scale flat-flame burner and a pilot-scale entrained flow biomass gasifier. For the flat-flame burner, the root mean square error (RMSE) were on the order of the uncertainty of the experimental measurements. For the gasifier, the RMSE was approximately three times higher than the experimental uncertainty – however, the main source of the error was the quantization of the training dataset. The accuracy of the predictions was found to be sufficient for process monitoring purposes. As a feature extraction step, reduction to statistical moments proved to be superior compared to pixel binning.

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