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  • 1.
    Sefidari, Hamid
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Luossavaara-Kiirunavaara Aktiebolag (LKAB), Luleå, Sweden.
    Wiinikka, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. RISE ETC (Energy Technology Centre) AB, Piteå, Sweden.
    Lindblom, Bo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Luossavaara-Kiirunavaara Aktiebolag (LKAB), Luleå, Sweden.
    Nordin, Lars Olof
    Luossavaara-Kiirunavaara Aktiebolag (LKAB), Luleå, Sweden.
    Wu, G
    GTT Technologies, Herzogenrath, Germany.
    Yazhenskikh, E
    Institute of Energy and Climate Research, Microstructure and Properties of Materials (IEK-2), Forschungszentrum Jülich GmbH, Jülich, Germany.
    Müller, M
    Institute of Energy and Climate Research, Microstructure and Properties of Materials (IEK-2), Forschungszentrum Jülich GmbH, Jülich, Germany.
    Ma, C
    Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory, Umeå University, Umeå, Sweden.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Comparison of high-rank coals with respect to slagging/deposition tendency at the transfer-chute of iron-ore pelletizing grate-kiln plants: A pilot-scale experimental study accompanied by thermochemical equilibrium modeling and viscosity estimations2019In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 193, p. 244-262Article in journal (Refereed)
    Abstract [en]

    Iron-ore pelletizing plants use high-rank coals to supply the heat necessary to process ores. Ash material from coal, in combination with iron-ore dust originating from the disintegration of the pellets, can cause deposition/slagging which often leads to severe production losses and damage. Deposition/slagging is most prominent in the hot areas of the grate-kiln setup and is more severe at the inlet of the rotary-kiln, i.e., the transfer-chute. Following on from our previous work, high-rank bituminous coals with potential for use in the pelletizing process were combusted in a pilot-scale (0.4 MW) pulverized-coal fired experimental combustion furnace (ECF). The fly-ash particles and short-term deposits were characterized to shed light on the observed difference in slagging/deposition tendencies of the coals. Global thermodynamic equilibrium modeling, in combination with viscosity estimates, was used to interpret the experimental findings and investigate the effect of the coal-ash composition upon deposition/slagging. This approach was carried out with and without the presence of Fe2O3-rich pellet-dust under oxidizing conditions within the temperature range at the transfer-chute of iron-ore pelletizing rotary-kilns. Based on the findings, a Qualitative Slagging Indicator (QSI) was proposed that can help pre-screen new solid fuels for potential slagging issues. The proposed QSI highlights the following: (1) an inverse relationship between viscosity and slagging/deposition tendency of the coals was observed (2) as viscosity decreases (either with increasing temperature or due to the change in the coal-ash composition), stronger deposits will form that will complicate the mechanical removal of the deposited layer. It was therefore inferred that low viscosity molten phases facilitate deposition/slagging, which is exacerbated by the presence of fluxing agents (e.g., CaO, MgO, K2O, Na2O, and Fe2O3) in the deposits. The low viscosity coal-ash-induced molten phases are also more likely to interact with the Fe2O3-rich pellet-dust that results in further decreases in viscosity, thereby intensifying depositions. The results from this work complement the on-going research by our group to elucidate and alleviate ash-related problems in industrial grate kilns.

  • 2.
    Wagner, Katharina
    et al.
    Bioenergy 2020+ GmbH,Vienna, Austria. Institute of Chemical, Environmental & Bioscience Engineering, Technische Universität Wien, Vienna, Austria.
    Häggström, Gustav
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Bioenergy 2020+ GmbH,Vienna, Austria. Institute of Chemical, Environmental & Bioscience Engineering, Technische Universität Wien, Vienna, Austria.Thermochemical Energy Conversion Laboratory, Umeå University,Umeå, Sweden.
    Priscak, Juraj
    Bioenergy 2020+ GmbH,Vienna, Austria. Institute of Chemical, Environmental & Bioscience Engineering, Technische Universität Wien, Vienna, Austria.
    Kuba, Matthias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Bioenergy 2020+ GmbH,Vienna, Austria. Institute of Chemical, Environmental & Bioscience Engineering, Technische Universität Wien, Vienna, Austria.Thermochemical Energy Conversion Laboratory, Umeå University, Umeå, Sweden.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hofbauer, Hermann
    Institute of Chemical, Environmental & Bioscience Engineering, Technische Universität Wien, Vienna, Austria.
    Layer formation mechanism of K-feldspar in bubbling fluidized bed combustion of phosphorus-lean and phosphorus-rich residual biomass2019In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 248, p. 545-554Article in journal (Refereed)
    Abstract [en]

    The use of phosphorus-rich fuels in fluidized bed combustion is one probable way to support both heat and power production and phosphorus recovery. Ash is accumulated in the bed during combustion and interacts with the bed material to form layers and/or agglomerates, possibly removing phosphorus from the bed ash fraction. To further deepen the knowledge about the difference in the mechanisms behind the ash chemistry of phosphorus-lean and phosphorus-rich fuels, experiments in a 5 kW bench-scale-fluidized bed test-rig with K-feldspar as the bed material were conducted with bark, wheat straw, chicken manure, and chicken manure admixtures to bark and straw. Bed material samples were collected and studied for layer formation and agglomeration phenomena by scanning electron microscopy combined with energy dispersive X-ray spectrometry. The admixture of phosphorus-rich chicken manure to bark changed the layer formation mechanism, shifting the chemistry to the formation of phosphates rather than silicates. The admixture of chicken manure to straw reduced the ash melting and agglomeration risk, making it possible to increase the time until defluidization of the fluidized bed occurred. The results also highlight that an increased ash content does not necessarily lead to more ash melting related problems if the ash melting temperature is high enough.

  • 3.
    Faust, Robin
    et al.
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Hannl, Thomas Karl
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Berdugo Vilches, Teresa
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Kuba, Matthias
    Bioenergy2020+ GmbH, Güssing, Austria.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Seemann, Martin
    Department of Space, Earth and Environment, Chalmers University of Technology, Gothenburg, Sweden.
    Knutsson, Pavleta
    Department of Space, Earth and Environment, Chalmers University of Technology, Gothenburg, Sweden.
    Layer Formation on Feldspar Bed Particles during Indirect Gasification of Wood. 1. K-Feldspar2019In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029Article in journal (Refereed)
    Abstract [en]

    The choice of bed material for biomass gasification plays a crucial role for the overall efficiency of the process. Olivine is the material conventionally used for biomass gasification due to the observed activity of olivine toward cracking of unwanted tars. Despite its catalytic activity, olivine contains high levels of chromium, which complicates the deposition of used bed material. Feldspar has shown the same activity as olivine when used as a bed material in biomass gasification. As opposed to olivine, feldspar does not contain environmentally hazardous compounds, which makes it a preferred alternative for further applications. The interaction of bed material and ash heavily influences the properties of the bed material. In the present study interactions between feldspar and main ash compounds of woody biomass in an indirect gasification system were investigated. Bed material samples were collected at different time intervals and analyzed with SEM-EDS and XRD. The obtained analysis results were then compared to thermodynamic models. The performed study was divided in two parts: in part 1 (the present paper), K-rich feldspar was investigated, whereas Na-rich feldspar is presented in part 2 of the study (DOI: 10.1021/acs.energyfuels.9b01291). From the material analysis performed, it can be seen that, as a result of the bed materials’ interactions with the formed ash compounds, the latter were first deposited on the surface of the K-feldspar particles and later resulted in the formation of Ca- and Mg-rich layers. The Ca enriched in the layers further reacted with the feldspar, which led to its diffusion into the particles and the formation of CaSiO3 and KAlSiO4. Contrary to Ca, Mg did not react with the feldspar and remained on the surface of the particles, where it was found as Mg- or Ca-Mg-silicates. As a result of the described interactions, layer separation was noted after 51 h with an outer Mg-rich layer and an inner Ca-rich layer. Due to the development of the Ca- and Mg-rich layers and the bed material–ash interactions, crack formation was observed on the particles’ surfaces.

  • 4.
    Hannl, Thomas Karl
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Faust, Robin
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Kuba, Matthias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Bioenergy2020+ GmbH, Güssing, Austria. Institute of Chemical, Environmental & Bioscience Engineering, TU Vienna, Vienna, Austria. Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Knutsson, Pavleta
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Berdugo Vilches, Teresa
    Department of Space, Earth, and Environment, Chalmers University of Technology, Gothenburg, Sweden.
    Seemann, Martin
    Department of Space, Earth, and Environment, Chalmers University of Technology, Gothenburg, Sweden.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Layer Formation on Feldspar Bed Particles during Indirect Gasification of Wood. 2. Na-Feldspar2019In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029Article in journal (Refereed)
    Abstract [en]

    Selecting a suitable bed material for the thermochemical conversion of a specific feedstock in a fluidized bed system requires identification of the characteristics of potential bed materials. An essential part of these characteristics is the interaction of the bed material with feedstock ash in a fluidized bed, which leads to layer formation and morphology changes. For this purpose, the interaction of feldspar bed material with the main ash-forming elements in wood ash (Ca, K, Mg, Si) in an indirect gasification system was analyzed using SEM-EDS, XRD, and thermodynamic modeling. In part 1 of this work (DOI: 10.1021/acs.energyfuels.9b01291), the layer formation on K-feldspar dominated by Ca reaction and ash deposition was investigated. The aim of this second part of the work was to determine the time-dependent layer formation on Na-feldspar and compare the results with the findings for K-feldspar. Interaction of Na-feldspar with ash-derived elements resulted in different layers on Na-feldspar: K reaction layers, where K replaced Na and Si shares decreased; Ca reaction layers, where Ca enriched and reacted with the Na-feldspar; and ash deposition layers, where wood ash elements accumulated on the surface. Ca reaction layers were formed first and became continuous on the surface before K reaction layers and ash deposition layers were detected. Cracks and crack layer formation in the Na-feldspar particles were found after several days of operation. The layer compositions and growth rates indicate that the diffusion of Ca and K plays an essential role in the formation of Ca reaction and K reaction layers. The reaction with Ca and the crack formation coincide with the interaction previously found for quartz and K-feldspar. In contrast to K-feldspar, Na-feldspar showed high potential for reaction with K. The findings indicate that the reaction of Na-feldspar with ash-derived K makes Na-feldspar a less stable bed material than K-feldspar during the thermochemical conversion of K-rich feedstocks in a fluidized bed system.

  • 5.
    Wagner, Katharina
    et al.
    Bioenergy 2020+ GmbH, Güssing, Austria.Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria.
    Häggström, Gustav
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Mauerhofer, Anna Magdalena
    Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria.
    Kuba, Matthias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Bioenergy 2020+ GmbH, Güssing, Austria. Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria.Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden .
    Skoglund, Nils
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hofbauer, Hermann
    Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria.
    Layer formation on K-feldspar in fluidized bed combustion and gasification of bark and chicken manure2019In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 127, article id 105251Article in journal (Refereed)
    Abstract [en]

    Understanding layer formation on bed materials used in fluidized beds is a key step for advances in the application of alternative fuels. Layers can be responsible for agglomeration-caused shut-downs but they can also improve the gas composition in fluidized bed gasification. Layers were observed on K-feldspar (KAlSi3O8) impurities originating from the combined heat and power plant Senden which applies the dual fluidized bed (DFB) steam gasification technology. Pure K-feldspar was therefore considered as alternative bed material in DFB steam gasification. Focusing on the interactions between fuel ash and bed material, K-feldspar was tested in combustion and DFB steam gasification atmospheres using different fuels, namely Ca-rich bark, Ca- and P-rich chicken manure, and an admixture of chicken manure to bark. The bed particle layers formed on the bed material surface were characterized using combined scanning electron microscopy and energy-dispersive X-ray spectroscopy; area mappings and line scans were carried out for all samples. The obtained data show no essential influence of operational mode on the layer-formation process. During the combustion and DFB steam gasification of Ca-rich bark, a layer rich in Ca formed while K was diffusing out of the layer. The use of Ca- and P-rich chicken manure inhibited the diffusion of K, and a layer rich in Ca and P formed. The addition of P to bark via chicken manure also changed the underlying layer-formation processes to reflect the same processes as observed for pure chicken manure.

  • 6.
    Wagner, Katharina
    et al.
    Bioenergy 2020+ GmbH.
    Kuba, Mathias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Bioenergy 2020+ GmbH.
    Häggström, Gustav
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hofbauer, Hermann
    Institute of Chemical, Environmental & Bioscience Engineering, TU Wien.
    Influence of phosphorus on the layer formation on k-feldspar during fluidized bed combustion and gasification2018In: European biomass conference and exhibition proceedings, E-ISSN 2282-5819, Vol. 26thEUBCE, p. 486-492Article in journal (Refereed)
    Abstract [en]

    Today, mainly wood-based feedstocks are used in thermo-chemical biomass conversion since they have a comparably high heating value and contain a small amount of ash. Fluidized beds allow a greater variety of fuels to be used, since they are rather flexible regarding their fuel input. The use of biogenic waste streams (chicken manure, horse manure, etc.) and sewage sludge would not only increase the fuel diversity in fluidized beds but might also enhance the usability of side products. The contained essential nutrients like phosphorus, potassium, calcium, etc. in these fuels are enriched in the ash after thermochemical conversion. Thus, in the near future it may be possible to apply this ash as secondary resource for fertilizer. Especially the recovery of phosphorus is of importance due to the imminent phosphorus scarcity. Due to its tendency to react with ash forming elements in fuels, phosphorus influences the ash chemistry severely. Especially the agglomeration and layer formation on bed materials during biomass combustion and gasification is highly dependent on the predominant ash forming elements. Phosphorus therefore has a significant impact on those mechanisms. Until now, the behavior of phosphorus-rich fuels in fluidized beds has not been studied in much detail. To develop a basic understanding of the behavior, phosphorus-rich feedstock was combusted in a bench-scale fluidized bed reactor. Ash layers on bed particles, which were formed during these experiments, were studied and compared to results with phosphorus-lean fuels. Furthermore, layer formation of phosphorus-rich and phosphorus-lean fuels from dual fluid bed gasification were compared to those from fluidized bed combustion. The studied layers on bed materials showed significant amounts of phosphorus. The data also indicates a change in layer formation as soon as phosphorus is present. An increased catalytic activity due ash-layer formation was observed for both phosphorus-rich and phosphorus-lean feedstock, independent from the presence of phosphorus in the ash layer

  • 7.
    Sefidari, Hamid
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lindholm, Bo
    Luossavaara-Kiirunavaara Aktiebolag (LKAB).
    Wiinikka, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. RISE ETC (Energy Technology Centre) AB.
    Nordin, Lars Olof
    Loussavaara-Kiirunavaara Limited, Luleå.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bhuiyan, Iftekhar Uddin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    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]

    o 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.

  • 8.
    Sefidari, Hamid
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lindblom, Bo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Luossavaara-Kiirunavaara Aktiebolag (LKAB).
    Wiinikka, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. RISE ETC (Energy Technology Centre) AB.
    Nordin, Lars Olof
    Loussavaara-Kiirunavaara Limited, Luleå.
    Lennartsson, Andreas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bhuiyan, Iftekhar Uddin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    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.

  • 9.
    Sundberg, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. RISE Research Institutes of Sweden, Department of Energy and Circular Economy, Borås, Sweden.
    Hermansson, Sven
    RISE Research Institutes of Sweden, Department of Energy and Circular Economy, Borås, Sweden. Södra Skogsägarna Ekonomisk Förening, Skogsudden, Växjö, Sweden.
    Tullin, Claes
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Traceability of bulk biomass: Application of radio frequency identification technology on a bulk pellet flow2018In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 118, p. 149-153Article in journal (Refereed)
    Abstract [en]

    Radio frequency identification (RFID) technology has been used since the 1950s in a wide range of applications. In the energy sector, there is a potential to use the technology to follow biomass fuels throughout a supply chain. In addition to logistic information, the RFID tags can be used to convey vital information of the fuel properties directly to the energy plant to be used at the moment of combustion. A detailed knowledge of the fuel composition at the moment it reaches the furnace can be used to improve energy efficiency, reduce emissions and limit problems with fouling and slagging. In this work, RFID technology was used in three separate trials to trace wood pellets, from the production site to the furnace. In the trials, RFID tags were added to batches of pellets containing 5% or 100% peat. In this way it was possible to follow the shift in pellet quality from standard pellets (100% wood) to the pellets containing the RFID tags by monitoring the change in flue gas composition. From the results it can be concluded that RFID tags indeed can be used to convey logistic information and thus information of fuel quality parameters throughout a supply chain for wood pellets. However, work on optimization is needed to design the RFID carrier properly to mix well with the pellets as illustrated in a separate trial. Finally, an economic estimate indicates that the marginal cost to implement a RFID system would be less than 1% of the total production cost of wood pellets.

  • 10.
    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.

  • 11.
    Skoglund, Nils
    et al.
    Umea University, Applied Physics & Electronics.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå University, Energy Technology and Thermal Process Chemistry.
    Ash transformation reactions for phosphorus-rich biomass and waste streams2017In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 254, article id 25Article in journal (Refereed)
  • 12.
    Xiong, Shaojun
    et al.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Bozaghian, Marjan
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Lestander, Torbjörn A.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Samuelsson, Robert
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Hellqvist, Sven
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Calcium oxide as an additive for both conservation and improvement of the combustion properties of energy grass: A preliminary study2017In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 99, p. 1-10Article in journal (Refereed)
    Abstract [en]

    Degradation of biomass is one of the major reasons for high costs of feedstock collection, transport, and storage, which is largely associated with biomass moisture and microbial activities. Our concept is to add calcium oxide (CaO) to the biomass already when it is collected and in its natural (wet) condition. When a suitable quantity of CaO is added to moistened biomass, an alkali microenvironment will be formed with a pH exceeding 9, based on the reaction CaO + H2O ↔ Ca(OH)2. As a consequence, microbial activities are largely inhibited. The Ca(OH)2 will then successively react with CO2, following the reaction Ca(OH)2 + CO2 ↔ CaCO3 + H2O. The CaCO3 will reside in the feedstock throughout the entire production chain and end up as an additive/sorbent to improve combustion by decreasing slagging. Two experiments were conducted and proved the concept works for at least reed canary grass, but, as expected, the strength of the effect was dependent on the CaO dosage and initial biomass moisture.

  • 13.
    Näzelius, Ida-Linn
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå University, Energy Technology and Thermal Process Chemistry.
    Rebbing, Anders
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Boman, Christoffer
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Fuel Indices for Estimation of Slagging of Phosphorus-Poor Biomass in Fixed Bed Combustion2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 1, p. 904-915Article in journal (Refereed)
    Abstract [en]

    The market for solid biofuels will grow rapidly during the coming years and there will be a great demand for raw materials. This will force the existing fuel base to also cover wooden materials of lower qualities as well as agricultural raw materials and residues, which often show unfavorable ash melting temperatures. This may lead to combustion related problems. Thus, for the utilization of lower quality fuels, it is important to be able to predict potential fuel ash related problems such as slagging. In light of this, the first objective of the present paper was to evaluate the applicability of previously defined indices for slagging of biomass fuels (phosphorus-poor) in fixed bed combustion. The evaluation showed that none of the previously suggested indices in the literature are suitable for qualitative (nor quantitative) prediction of slagging during fixed bed combustion of P-poor biomass fuels. Hence, a second objective was to develop improved novel fuel indices that can be applied to estimate the slagging of phosphorus-poor biomass in fixed bed combustion. The novel fuel indices give a qualitative prediction of the slagging tendency in biomass fixed bed combustion but still needs additional work to further extend the compositional range as well as to fine-tune the indices’ boundaries.

  • 14.
    He, Hanbing
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Time-Dependent Crack Layer Formation in Quartz Bed Particles during Fluidized Bed Combustion of Woody Biomass2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 2, p. 1672-1677Article in journal (Refereed)
    Abstract [en]

    Bed agglomeration during combustion and gasification of woody biomass fuels in quartz beds has been frequently studied, and chemical mechanisms responsible for bed agglomeration have been suggested. However, few studies have focused on the bed material deposition on walls, in cyclones, and return legs in fluidized bed combustion. Part of these bed material depositions originates from sticky fragments of alkali-rich silicates formed after crack formation in older quartz bed particles. The crack layer formation in quartz bed particles in fluidized bed combustion of woody biomass was therefore investigated by collecting bed material samples of different ages from full-scale bubbling and circulating fluidized bed facilities. Scanning electron microscopy/energy-dispersive spectroscopy was used to analyze the crack morphology and composition of the layer surrounding the cracks. For quartz bed particles with an age of some days, a crack in the quartz bed particle was observed in connection to the irregular interface between the inner layer and the core of the bed particle. The crack layer composition is similar for quartz particles with different ages and for samples taken from different fluidized bed techniques. Their composition is dominated by Si, K, Ca, and Na (except O). These crack layers become deeper, wider, and more common as bed particle age increases. The crack layers eventually connect with each other, and the whole quartz particle is transformed into smaller quartz cores surrounded by crack layers, which were observed in particles older than 1 week. From the characterization work, a crack formation process including three phases is proposed on the basis of the presumption that the initial crack layer formation resulted from the presence of induced cracks in the inner quartz bed particle layer. Fragmentation after the third phase is likely responsible for the formation of sticky alkali silicate deposit formation, and a weekly complete exchange of the bed is therefore recommended to avoid problematic deposits in combustion of woody-type biomass in fluidized bed combustion

  • 15.
    He, Hanbing
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Time-dependent layer formation on K-feldspar bed particles during fluidized bed combustion of woody fuels2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 11, p. 12848-12856Article in journal (Refereed)
    Abstract [en]

    Despite frequent reports on layer characteristics on quartz bed particles, few studies have been found focusing on the layer characteristics on K-feldspar bed particles. The layer characteristics of K-feldspar bed particles in fluidized bed combustion of woody biomass was therefore investigated by collecting bed material samples of different ages from large-scale bubbling and circulating fluidized bed facilities. Scanning electron microscopy/energy-dispersive spectroscopy was used to analyze the layer morphology and elemental composition. For particles with an age of 1 day, a thin layer rich in Si, Ca and Al was found. For particles older than some days, an inner more homogenous layer containing cracks and an outer more particle-rich layer were observed. The outer layer was thinner for K-feldspar bed particles sampled from circulating fluidized bed, compared to particles from bubbling fluidized bed. The concentration of Ca in the inner layer increases towards bed particle surface, the molar ratio of Si/Al is maintained, and the molar ratio of K/Al decreases compared to the K-feldspar. The inner layer thickness for quartz and K-feldspar bed particles collected at the same operation conditions was found to be similar. No crack layers, as have been observed in quartz particles, were found in the core of the K-feldspar bed particles. The results suggest that the diffusion and reaction of Ca2+ into/with the feldspar particle play an important role on the inner layer formation process.

  • 16.
    Ma, Charlie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Carlborg, Markus
    Energy Technology and Thermal Process Chemistry, Department of Applied Physics and Electronics, Umeå University.
    Hedman, Henry
    SP Energy Technology Center AB.
    Wennebro, Jonas
    SP Energy Technology Center AB.
    Weiland, Fredrik
    SP Energy Technology Center AB.
    Wiinikka, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. SP Energy Technology Center AB.
    Backman, Rainer
    Energy Technology and Thermal Process Chemistry, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ash Formation in Pilot-Scale Pressurized Entrained-Flow Gasification of Bark and a Bark/Peat Mixture2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 12, p. 10543-10554Article in journal (Refereed)
    Abstract [en]

    Pressurized entrained-flow gasification (PEFG) of bark and a bark/peat mixture (BPM) was carried out in a pilot-scale reactor (600 kWth, 7 bar(a)) with the objective of studying ash transformations and behaviors. The bark fuel produced a sintered but nonflowing reactor slag, while the BPM fuel produced a flowing reactor slag. Si was enriched within these slags compared to their original fuel ash compositions, especially in the bark campaign, which indicated extensive ash matter fractionation. Thermodynamically, the Si contents largely accounted for the differences in the predicted solidus/liquidus temperatures and melt formations of the reactor slags. Suspension flow viscosity estimations were in qualitative agreement with observations and highlighted potential difficulties in controlling slag flow. Quench solids from the bark campaign were mainly composed of heterogeneous particles resembling reactor fly ash particles, while those from the BPM campaign were flowing slags with likely chemical interactions with the wall refractory. Quench effluents and raw syngas particles were dominated by elevated levels of K that, along with other chemical aspects, indicated KOH(g) and/or K(g) were likely formed during PEFG. Overall, the results provide information toward development of woody biomass PEFG and indicate that detailed understanding of the ash matter fractionation behavior is essential.

  • 17.
    Kuba, Matthias
    et al.
    TU Wien.
    He, Hanbing
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kirnbauer, Freidrich
    Bioenergy 2020+.
    Skoglund, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hoffbauer, Herman
    TU Wien.
    Mechanism of Layer Formation on Olivine Bed Particles in Industrial-Scale Dual Fluid Bed Gasification of Wood2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 9, p. 7410-7418Article in journal (Refereed)
    Abstract [en]

    Utilization of biomass as feedstock in dual fluidized bed steam gasification is a promising technology for the substitution of fossil energy carriers. Experience from industrial-scale power plants showed an alteration of the olivine bed material due to interaction with biomass ash components. This change results mainly in the formation of Ca-rich layers on the bed particles. In this paper, a mechanism for layer formation is proposed and compared to the better understood mechanism for layer formation on quartz bed particles. Olivine bed material was sampled at an industrial-scale power plant before the start of operation and at predefined times after the operation had commenced. Therefore, time-dependent layer formation under industrial-scale conditions could be investigated. The proposed mechanism suggests that the interaction between wood biomass ash and olivine bed particles is based on a solid-solid substitution reaction, where Ca2+ is incorporated into the crystal structure. As a consequence, Fe2+/3+ and Mg2+ ions are expelled as oxides. This substitution results in the formation of cracks in the particle layer due to a volume expansion in the crystal structure once Ca2+ is incorporated. The results of this work are compared to relevant published results, including those related to quartz bed particles

  • 18.
    He, Hanbing
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå universitet, Energy Technology and Thermal Process Chemistry, Umeå University, Umeå university.
    Backman, Rainer
    Umeå university, Åbo Akademi, Energy Technology and Thermal Process Chemistry, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Mechanism of Quartz Bed Particle Layer Formation in Fluidized Bed Combustion of Wood-Derived Fuels2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 3, p. 2227−2232-Article in journal (Refereed)
    Abstract [en]

    Agglomeration is among one of the major problems in the operation of fluidized bed boilers. The formation of bed particle layers is thought to play an important role on the occurrence of agglomeration in wood-fired fluidized (quartz) beds. In spite of frequent experimental reports on the quartz bed particle layer characteristics, the underlying bed layer formation process has not yet been presented. By combining our previously experimental results on layer characteristics for samples with durations from 4 h to 23 days, with phase diagrams, thermochemical equilibrium calculations, and a diffusion model, a mechanism of quartz bed particle layer formation was proposed. For younger bed particles (

  • 19.
    Kuba, Matthias
    et al.
    TU Wien, Institute of Chemical Engineering.
    He, Hanbing
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kirnbauer, Freidrich
    Bioenergy 2020+.
    Skoglund, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå University, Energy Technology and Thermal Process Chemistry.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hoffbauer, Herman
    TU Wien, Institute of Chemical Engineering.
    Thermal stability of bed particle layers on naturally occurring minerals from dual fluid bed gasification of woody biomass2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 10, p. 8277-8285Article in journal (Refereed)
    Abstract [en]

    The use of biomass as feedstock for gasification is a promising way of producing not only electricity and heat but also fuels for transportation and synthetic chemicals. Dual fluid bed steam gasification has proven to be suitable for this purpose. Olivine is currently the most commonly used bed material in this process due to its good agglomeration performance and its catalytic effectiveness in the reduction of biomass tars. However, as olivine contains heavy metals such as nickel and chromium, no further usage of the nutrient-rich ash is possible, and additional operational costs arise due to necessary disposal of the ash fractions. This paper investigates possible alternative bed materials and their suitability for dual fluid bed gasification systems focusing on the behavior of the naturally occurring minerals olivine, quartz, and K-feldspar in terms of agglomeration and fracturing at typical temperatures. To this end, samples of bed materials with layer formation on their particles were collected at the industrial biomass combined heat and power (CHP) plant in Senden, Germany, which uses olivine as the bed material and woody biomass as feedstock. The low cost logging residue feedstock contains mineral impurities such as quartz and K-feldspar, which become mixed into the fluidized bed during operation. Using experimental and thermochemical analysis, it was found that the layers on olivine and K-feldspar showed a significantly lower agglomeration tendency than quartz. Significant fracturing of particles or their layers could be detected for olivine and quartz, whereas K-feldspar layers were characterized by a higher stability. High catalytic activity is predicted for all three minerals once Ca-rich particle layers are fully developed. However, quartz may be less active during the buildup of the layers due to lower amounts of Ca in the initial layer formation

  • 20.
    Rebbling, Anders
    et al.
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Näzelius, Ida-linn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Piotrowska, Patrycja
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Skoglund, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boman, Christoffer
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Boström, Dan
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Waste Gypsum Board and Ash-Related Problems during Combustion of Biomass: 2. Fixed Bed2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 12, p. 10705-10713Article in journal (Refereed)
    Abstract [en]

    This paper is the second of two describing the use of shredded waste gypsum board (SWGB) as an additive during combustion of biomass. The focus of this paper is to determine whether SWGB can be used as a fuel additive providing CaO and SO2/SO3 for mitigation of ash-related operational problems during combustion of biomass and waste derived fuels in grate fired fixed bed applications. The former study in this series was performed in a fluidized bed and thus allow for comparison of results. Gypsum may decompose at elevated temperatures and forms solid CaO and gaseous SO2/SO3 which have been shown to reduce problems with slagging on the fixed bed and alkali chloride deposit formation. Three different biomasses, spruce bark (SB), reed canary grass (RG), and wheat straw (WS), were combusted with and without addition of SWGB in a residential pellet burner (20 kWth). Waste derived fuel with and without the addition of SWGB was combusted in a large scale grate-fired boiler (25 MWth). The amount of added SWGB varied between 1 and 4 wt %. Ash, slag, and particulate matter (PM) were sampled and subsequently analyzed with scanning electron microscopy/ energy dispersive spectroscopy and X-ray diffraction. Decomposition of CaSO4 originating from SWGB was observed as elevated SO2 emissions in both the large scale and small scale facilities and significantly higher than was observed in the fluidized bed study. Slag formation was significantly reduced due to formation of calcium-silicates in small scale application, but no conclusive observations regarding calcium reactivity could be made in the large scale application. In the small scale study the formation of K2SO4 was favored over KCl in PM, while in the large scale study K3Na(SO4)2 and K2Zn2(SO4)3 increased. It is concluded that SWGB can be used as a source of CaO and SO2/SO3 to mitigate slag formation on the grate and chloride-induced high temperature corrosion and that fixed bed applications are likely more suitable than bubbling fluidized beds when using SWGB as an additive.

  • 21.
    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)
  • 22.
    Kuba, Matthias
    et al.
    Bioenergy 2020+ GmbH.
    He, Hanbing
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kirnbauer, Friedrich
    Bioenergy 2020+ GmbH.
    Boström, Dan
    Umeå universitet, Energy Technology and Thermal Process Chemistry, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hofbauer, Hermann
    Vienna University of Technology, Institute of Chemical Engineering.
    Deposit build-up and ash behavior in dual fluid bed steam gasification of logging residues in an industrial power plant2015In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 139, p. 33-41Article in journal (Refereed)
    Abstract [en]

    A promising way to substitute fossil fuels for production of electricity, heat, fuels for transportation and synthetic chemicals is biomass steam gasification in a dual fluidized bed (DFB). Using lower-cost feedstock, such as logging residues, instead of stemwood, improves the economic operation. In Senden, near Ulm in Germany, the first plant using logging residues is successfully operated by Stadtwerke Ulm. The major difficulties are slagging and deposit build-up. This paper characterizes inorganic components of ash forming matter and draws conclusions regarding mechanisms of deposit build-up. Olivine is used as bed material. Impurities, e.g., quartz, brought into the fluidized bed with the feedstock play a critical role. Interaction with biomass ash leads to formation of potassium silicates, decreasing the melting temperature. Recirculation of coarse ash back into combustion leads to enrichment of critical fragments. Improving the management of inorganic streams and controlling temperature levels is essential for operation with logging residues.

  • 23.
    Paulrud, Susanne
    et al.
    SP Sveriges Tekniska Forskningsinstitut, SP Energiteknik.
    Hjörndede, Anders
    SP Sveriges Tekniska Forskningsinstitut, SP Energiteknik.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ready-made fuel mix of straw, wood chips and additive, from the terminal to the CHP-plant2015Conference paper (Other academic)
  • 24.
    Näzelius, Ida-Linn
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Fagerström, Jonathan
    Energy Technology and Thermal Process Chemistry, Umeå University, Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Boman, Christoffer
    Energy Technology and Thermal Process Chemistry, Umeå University, Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Boström, Dan
    Energy Technology and Thermal Process Chemistry, Umeå University, Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Slagging in Fixed bed Combustion of Phosphorus-Poor Biomass: Critical Ash Forming Processes and Compositions2015In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 29, no 2, p. 894-908Article in journal (Refereed)
    Abstract [en]

    Slagging in combustion facilities are not welcomed, as it may cause technical and operational problems as well as extra costs. Increased understanding of the critical slagging sub-processes makes it easier to suggest semi-empirical models and fuel indexes for prediction of slagging tendency of different fuels. That could open the biomass market for potentially more troublesome raw materials. The objective of this work was to determine critical ash forming processes and compositions in fixed bed combustion of phosphorus-poor biomass fuels. This was achieved by performing a systematic review of data and experience gathered from combustion experiments in a small grate burner of 36 different biomasses, chemical analysis of their bottom ashes and slags. The paper presents a discussion of the slagging tendency in phosphorus-poor biomass by combining three different slagging classifications ending up with a proposed starting point for a new slagging index. The slag (ash particles > 3.15 mm) formed during the combustion experiments has been described according to fraction of fuel ash that forms slag (wt-%), visual sintering category (1-4) and viscosity predictions. The results explain that both the fraction of melt and its viscosity is critical for the slag formation process in phosphorus-poor biomasses. Additionally, fuels with low Si/K ratio along with higher Ca concentration may form a low viscous carbonate melt not prone to form slag. Increased Si and lowered Ca concentration will increase the amount of formed silicate melt formed as well as its viscosity, thus resulting in a more sticky melt.

  • 25.
    Hermansson, Sven
    et al.
    SP Sveriges Tekniska Forskningsinstitut, SP Energiteknik.
    Hjörnhede, Anders
    SP Sveriges Tekniska Forskningsinstitut, SP Energiteknik.
    Ryde, Daniel
    Sjögren, Per-Olof
    Boman, Christoffer
    Energy Technology and Thermal Process Chemistry, Umeå University, Umeå universitet.
    Fagerström, Jonathan
    Energy Technology and Thermal Process Chemistry, Umeå University, Umeå universitet.
    Rebbling, Anders
    Umeå university.
    Olwa, Joseph
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Nockhammar, Per
    Svensson, Mattias
    Småskalig biokraftvärme från externeldad gasturbin: systemstudier, värmeväxling och turbinstyrning2015Report (Other academic)
  • 26.
    Ma, Charlie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Backman, Rainer
    Umeå university, Åbo Akademi, Energy Technology and Thermal Process Chemistry, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Thermochemical equilibrium study of slag formation during pressurized entrained-flow gasification of woody biomass2015In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 29, no 7, p. 4399-4406Article in journal (Refereed)
    Abstract [en]

    The potential slag formation behavior during pressurized entrained-flow gasification (PEFG) of woody biomass has been studied from a thermodynamic perspective with respect to compositional, temperature, and pressure variations. An ash transformation scheme was proposed on the basis of the melt formation potential that arises when gaseous K species are present with Si and Ca. Databases and models in FactSage 6.4 were used to carry out thermochemical equilibrium calculations within ChemSheet. It was found that increasing pressure and increasing Si content expanded the range of operating conditions that are conducive of melt formation, while increasing temperature and increasing Ca content diminished the range. The results from the calculations compared qualitatively well to experimental results and provide further information needed in the development of PEFG reactors for woody biomass

  • 27.
    Piotrowska, Patrycja
    et al.
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Rebbling, Anders
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Lindberg, Daniel
    Åbo Akademi, Process Chemistry Centre, Åbo Akademi University.
    Backman, Rainer
    Umeå university, Åbo Akademi, Energy Technology and Thermal Process Chemistry, Umeå University, Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå universitet, Energy Technology and Thermal Process Chemistry, Umeå University, Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Waste gypsum bpard and ash related problems during combustion of biomass: Part 1 : fluidized bed2015In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 29, no 2, p. 877-893Article in journal (Refereed)
    Abstract [en]

    This paper is the first in a series of two describing the use of waste gypsum boards as an additive during combustion of biomass. This paper is focusing on experiments performed in a bench-scale bubbling fluidized-bed reactor (5 kW). Three biomass fuels were used; i.e. wheat straw (WS), reed canary grass (RC), and spruce bark (SB), with and without addition of shredded waste gypsum board (SWGB). The objective of this work was to determine the effect of SWGB addition on biomass ash transformation reactions during fluidized bed combustion. The combustion was carried out in a bed of quartz sand at 800 °C or 700 °C for 8 hours. After the combustion stage a controlled fluidized-bed agglomeration test was carried out to determine the defluidization temperature. During combustion experiments outlet gas composition was continuously measured by means of FT-IR. At the same place in the flue gas channel particulate matter (PM) was collected with a 13-stage Dekati low-pressure impactor. Bottom and cyclone fly ash samples were collected after the combustion tests. In addition, during the combustion tests a 6-hour deposit sample was collected with an air-cooled (430 °C) probe. All ash samples were analyzed by means of scanning electron microscope combined with energy dispersive X-ray spectrometer (SEM-EDS) for elemental composition and with X-ray powder diffractometer (XRD) for the detection of crystalline phases. Decomposition of CaSO4 originating from SWGB was mainly observed during combustion of reed canary grass at 800 °C. The decomposition was observed as doubled SO2 emissions. No significant increase of SO2 during combustion of SB and WS was observed. However, the interaction of SWGB particles with WS and SB ash forming matter, mainly potassium containing compounds, led to the formation of K2Ca2(SO4)3

  • 28.
    Skoglund, Nils
    et al.
    Umeå University. Department of Applied Physics and Electronics.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Grimm, Alejandro
    Boström, Dan
    Umeå University. Department of Applied Physics and Electronics.
    Combustion of Biosolids in a Bubbling Fluidized Bed: Part I: Main Ash Forming Elements and Ash Distribution with a Focus on Phosphorus2014In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 28, no 2, p. 1183-1190Article in journal (Refereed)
    Abstract [en]

    This is the first in a series of three papers describing combustion of biosolids in a 5-kW bubbling fluidized bed, the ash chemistry, and possible application of the ash produced as a fertilizing agent. This part of the study aims to clarify whether the distribution of main ash forming elements from biosolids can be changed by modifying the fuel matrix, the crystalline compounds of which can be identified in the raw materials and what role the total composition may play for which compounds are formed during combustion. The biosolids were subjected to low-temperature ashing to investigate which crystalline compounds that were present in the raw materials. Combustion experiments of two different types of biosolids were conducted in a 5-kW benchscale bubbling fluidized bed at two different bed temperatures and with two different additives. The additives were chosen to investigate whether the addition of alkali (K2CO3) and alkaline-earth metal (CaCO3) would affect the speciation of phosphorus, so the molar ratios targeted in modified fuels were P:K = 1:1 and P:K:Ca = 1:1:1, respectively. After combustion the ash fractions were collected, the ash distribution was determined and the ash fractions were analyzed with regards to elemental composition (ICP-AES and SEM-EDS) and part of the bed ash was also analyzed qualitatively using XRD. There was no evidence of zeolites in the unmodified fuels, based on low-temperature ashing. During combustion, the biosolid pellets formed large bed ash particles, ash pellets, which contained most of the total ash content (54%–95% (w/w)). This ash fraction contained most of the phosphorus found in the ash and the only phosphate that was identified was a whitlockite, Ca9(K,Mg,Fe)(PO4)7, for all fuels and fuel mixtures. With the addition of potassium, cristobalite (SiO2) could no longer be identified via X-ray diffraction (XRD) in the bed ash particles and leucite (KAlSi2O6) was formed. Most of the alkaline-earth metals calcium and magnesium were also found in the bed ash. Both the formation of aluminum-containing alkali silicates and inclusion of calcium and magnesium in bed ash could assist in preventing bed agglomeration during co-combustion of biosolids with other renewable fuels in a full-scale bubbling fluidized bed.

  • 29.
    Fagerström, Jonathan
    et al.
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Rebbling, Anders
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Olwa, Joseph
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Steinvall, Erik
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Boström, Dan
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boman, Christoffer
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Control Strategies for Reduction of Alkali Release during Grate Combustion of Biomass: Influence of Process Parameters and Fuel Additives in a 40 kW Reactor2014Conference paper (Refereed)
  • 30.
    Fagerström, Jonathan
    et al.
    Umeå University. Department of Applied Physics and Electronics.
    Näzelius, Ida-Linn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Gilbe, Carl
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå University. Department of Applied Physics and Electronics.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boman, Christoffer
    Umeå University. Department of Applied Physics and Electronics.
    Influence of peat ash composition on particle emissions and slag formation in biomass grate co-combustion2014In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 28, no 5, p. 3403-3411Article in journal (Refereed)
    Abstract [en]

    Co-combustion by fuel blending of peat and biomass has shown positive effects on operational problems. However, peat ash compositions vary considerably, and this has been shown to affect the potential for operational problems in different fuel-blending situations. The present work used three different peat types with the objective to elucidate how the variation in peat ash composition influences both particle emissions and slag formation during co-combustion with three different biomasses in a small-scale pellet boiler. Estimations of potassium release and slag formation were performed and discussed in relation to fuel composition in the (K2O + Na2O)–(CaO + MgO)–(SiO2) system. All tested peat types reduced the fine particle emissions by capturing potassium into the bottom ash as one or several of the following forms: slag, sulfates, chlorides, and alumina silicates. However, there were considerable differences between the peat types, presumably depending upon both their content and mineral composition of silicon, calcium, aluminum, and sulfur. Some general important and beneficial properties of peat type in co-combustion situations with biomass are defined here, but the specific blending proportion of peat should be decided on an individual basis for each scenario based on the relative contents in the fuel mixture of the most relevant ash-forming elements.

  • 31.
    Paulrud, Susanne
    et al.
    SP Sveriges Tekniska Forskningsinstitut, SP Energiteknik.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lagring/torkning av salix-effekt på slaggnings och beläggningstendens vid förbränning2014Report (Other academic)
  • 32.
    Carlborg, Marcus
    et al.
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Boström, Dan
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Backman, Rainer
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Reactions Between Ash Forming Elements and Two Mullite Based Refractories in Entrained Flow Gasification of Wood2014Conference paper (Refereed)
  • 33.
    Carlsson, Per
    et al.
    Energy Technology Centre, Piteå.
    Ma, Charlie
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Molinder, Roger
    Energy Technology Centre, Piteå.
    Weiland, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wiinikka, Henrik
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Öhrman, Olov
    Energy Technology Centre, Piteå.
    Slag Formation During Oxygen Blown Entrained-Flow Gasification of Stem Wood2014In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 28, no 11, p. 6941−6952-, article id 28Article in journal (Refereed)
    Abstract [en]

    Stem wood powders were fired in a mullite-lined pilot-scale oxygen-blown pressurized entrained-flow gasifier. During repeated campaigns involving increases in fuel load and process temperature, slag formations that eventuated in the blockage of the gasifier outlet were observed. These slags were retrieved for visual and chemical characterization. It was found that the slags had very high contents of Al and, in particular, high Al/Si ratios that suggest likely dissolution of the mullite-based refractory of the gasifier lining due to interactions with the fuel ash. Possible causes for the slag formation and behavior are proposed, and practical implications for the design of future stem wood entrained-flow gasifiers are also discussed

  • 34.
    Ma, Charlie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Carlborg, Marcus
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Backman, Rainer
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Slag Formation during Pressurized Entrained-flow Gasification of Woody Biomass: A Thermochemical Equilibrium Study2014Conference paper (Refereed)
  • 35. Hermansson, Sven
    et al.
    Backeus, Sofia
    Boman, Christoffer
    Gulliksson, Hans
    Larsson, Sylvia
    Strand, Michael
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Testbädd Mellanskalig Biorbränsleförbränning: en förstudie2014Report (Other academic)
  • 36.
    He, Hanbing
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Energy Technology and Thermal Process Chemistry, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Time dependence of bed particle layer formation in fluidized quartz bed combustion of wood-derived fuels2014In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 28, no 6, p. 3841-3848Article in journal (Refereed)
    Abstract [en]

    Formation of sticky layers on bed particles has been considered as a prerequisite for bed agglomeration in fluidized bed combustion of wood-derived fuels. The present investigation was undertaken to determine the quartz bed particle layer formation process in fluidized bed combustion of wood-derived fuels. Bed material samples from three different appliances, bench-scale bubbling fluidized bed, full-scale bubbling fluidized bed, and full-scale circulating fluidized bed, at different sampling times from startup with a fresh bed were collected. Scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD) were used to explore layer morphology and chemical composition and to gain information on crystalline phases of the layers and coatings. Significant differences in layer morphology and composition were found for quartz bed particles with different ages. For bed samples with operational duration of less than 1 day, only one thin Ca-, Si-, O-, and K-rich homogeneous quartz bed particle layer that has a relatively high K/Ca molar ratio was found. For quartz bed particles with an age from around 1 day to 2 weeks, an outer more particle-rich coating layer was also found. During the initial days of this period, the layer growth rate was high but decreased over time, and decreasing K/Ca and increasing Ca/Si molar ratios in the inner bed particle layer were observed. For bed particles with age between 2 and 3 weeks, a much lower layer growth rate was observed. At the same time, the Ca/Si molar ratio reached high values and the K concentration remained on a very low level. In addition to these layer formation processes mentioned, also an inner–inner/crack layer was also formed in the circulating fluidized bed quartz bed particles simultaneously with the inner bed particle layer.

  • 37.
    Piotrowska, Patrycja
    et al.
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Rebbling, Anders
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Näzelius, Ida-Linn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Grimm, Alejandro
    Boström, Dan
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Waste Gypsum Board as a Fuel Additive in Combustion of Grass and Waste Derived Fuel – Bench- and Full-scale Studies.2014Conference paper (Refereed)
  • 38.
    Nordgren, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hedman, Henry
    Energy Technology Centre, Piteå.
    Padban, Nader
    Vattenfall Research & Development.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ash transformations in pulverised fuel co-combustion of straw and woody biomass2013In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 105, p. 52-58Article in journal (Refereed)
    Abstract [en]

    Ash transformation processes have been studied during co-firing of wheat straw and pine stem wood and softwood bark. Pilot-scale trials in a 150 kW pulverised-fuel-fired burner were performed. Thermodynamic equilibrium calculations were made to support the interpretation of the results. The results show that fast reactions involving gaseous ash compounds are favored at the expense of reactions where condensed components participate. Accordingly, the conditions promote gas phase reactions resulting in the formation of chlorides, sulfate and carbonates whereas reactions involving condensed reactants are suppressed. Both the slagging and fouling propensity of all co-firing mixes was reduced compared to that for pure straw. For the wood/straw mixes this was mainly due to a dilution of the ash forming elements of straw whereas for straw/bark, an additional effect from interaction between the fuel ash components was observed to primarily reduce slagging. In general it can be concluded that under powder combustion conditions equilibrium are approached selectively and that the ash matter are strongly fractionated. The general results in this paper are useful for straw-fired power stations looking for alternative co-firing fuels.

  • 39.
    Ma, Charlie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Weiland, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hedman, Henry
    Energy Technology Centre, Piteå.
    Boström, Dan
    Umeå universitet.
    Backman, Rainer
    Umeå universitet.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Characterization of Reactor Ash Deposits from Pilot-Scale Pressurized Entrained-Flow Gasification of Woody Biomass2013In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 11, p. 6801−6814-Article in journal (Refereed)
    Abstract [en]

    Pressurized entrained-flow gasification of renewable forest residues has the potential to produce high-quality syngas suitable for the synthesis of transport fuels and chemicals. The ash transformation behavior during gasification is critical to the overall production process and necessitates a level of understanding to implement appropriate control measures. Toward this end, ash deposits were collected from inside the reactor of a pilot-scale O2-blown pressurized entrained-flow gasifier firing stem wood, bark, and pulp mill debarking residue (PMDR) in separate campaigns. These deposits were characterized with environmental scanning electron microscopy equipped with energy-dispersive X-ray spectrometry and X-ray diffractometry. The stem wood deposit contained high levels of calcium and was comparatively insubstantial. The bark and PMDR fuels contained contaminant sand and feldspar particles that were subsequently evident in each respective deposit. The bark deposit consisted of lightly sintered ash aggregates comprising presumably a silicate melt that enveloped particles of quartz and, to a lesser degree, feldspars. Discontinuous layers likely to be composed of alkaline-earth metal silicates were found upon the aggregate peripheries. The PMDR deposit consisted of a continuous slag that contained quartz and feldspar particles dispersed within a silicate melt. Significant levels of alkaline-earth and alkali metals constituted the silicate melts of both the bark and PMDR deposits. Overall, the results suggest that fuel contaminants (i.e., quartz and feldspars) play a significant role in the slag formation process during pressurized entrained-flow gasification of these woody biomasses.

  • 40.
    Jonsson, Carrie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wiinikka, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lindblom, Bo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Stjernberg, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Comparison of particle and deposit formation between a full-scale grate-kiln plant (40 MW) and a pilot-scale pulverised coal-fired furnace (400 kW)2013Conference paper (Refereed)
    Abstract [en]

    The iron ore pelletizing industry utilizes the grate-kilnprocess to dry and sinter the pellets into finished product.The grate-kiln process has a known deposit formation issuethat needs to be further understood. Combustion ofpulverised coal in the rotary kiln generates fly ash particles;in addition to that, particles generated from disintegratediron ore pellets are also entrained in the process gas stream.The combined effect of both sources of particles cantherefore contribute to the deposit formation in the process.In this work, particle- and deposit formation were studiedboth from a full-scale grate-kiln plant (40 MW) and from apilot-scale pulverised coal fired furnace (400 kW). Particleswere collected with a water-cooled probe with nitrogen gasas dilution medium at the tip of the probe. The particleswere separated simultaneously with a pre-cyclone and a 13stages low-pressure impactor during samplings. Depositswere collected with a refractory plate which was attachedat the tip of a water-cooled probe, exposed to the hightemperature (>1100 °C) process gas stream. Particles anddeposits were characterized with an environmentalscanning electron microscope and a scanning electronmicroscope that equipped with energy dispersivespectroscopy detector. A comparison of particle and depositcharacteristics between the grate-kiln plant and the pilotscale pulverised coal fired furnace is presented in this paper,with focus on the potential influence of disintegrated ironore pellets on the particle- and deposit formation process.

  • 41.
    Jonsson, Carrie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Stjernberg, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Wiinikka, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lindblom, Bo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Deposit formation in a grate-kiln plant for iron-ore pellet production: Part 1: Characterization of process gas particles2013In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 10, p. 6159-6170Article in journal (Refereed)
    Abstract [en]

    Slag formation in the grate-kiln process is a major problem for iron-ore pellet producers. It is therefore important to understand the slag formation mechanism in the grate-kiln production plant. This study initiated the investigation by in situ sampling and identifying particles in the flue gas from a full-scale 40 MW grate-kiln production plant for iron-ore pelletizing. Particles were sampled from two cases of combustion with pulverized coal and heavy fuel oil. The sampling location was at the transfer chute that was situated between the traveling grate and the rotary kiln. The particle-sampling system was set up with a water-cooled particle probe equipped with nitrogen gas dilution, cyclone, and low-pressure impactor. Sub-micrometer and fine particles were size-segregated in the impactor, while coarse particles (>6 μm) were separated with a cyclone before the impactor. Characterization of these particles was carried out with environmental scanning electron microscopy (ESEM), and the morphology of sub-micrometer particles was studied with transmission electron microscopy (TEM). The results showed that particles in the flue gas consisted principally of fragments from iron-ore pellets and secondarily of ashes from pulverized coal and heavy fuel oil combustions. Three categories of particle modes were identified: (1) sub-micrometer mode, (2) first fragmentation mode, and (3) second fragmentation mode. The sub-micrometer mode consisted of vaporized and condensed species; relatively high concentrations of Na and K were observed for both combustion cases, with higher concentrations of Cl and S from heavy fuel oil combustion but higher concentrations of Si and Fe and minor P, Ca, and Al from coal combustion. The first fragmentation mode consisted of both iron-ore pellet fines and fly ash particles; a significant increment of Fe (>65 wt %) was observed, with higher concentrations of Ca and Si during heavy fuel oil combustion but higher concentrations of Si and Al during coal combustion. The second fragmentation mode consisted almost entirely of coarse iron-ore pellet fines, predominantly of Fe (90 wt %). The particles in the flue gas were dominantly iron-ore fines because the second fragmentation mode contributed >96 wt % of the total mass of collected particles.

  • 42.
    Stjernberg, Jesper
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Jonsson, Carrie
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wiinikka, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lindblom, Bo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Deposit formation in a grate-kiln plant for iron-ore pellet production: Part 2: Characterization of deposits2013In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 10, p. 6171-6184Article in journal (Refereed)
    Abstract [en]

    Buildup of deposit material in chunks on refractory linings caused by combustion of various fuels is a well-known problem. This study characterizes the short-term deposits on refractory material in a grate–kiln process, carried out through in situ measurements using a water-cooled probe with a part of a refractory brick mounted in its end. Sampling was carried out during combustion of both oil and coal. A significant difference in deposition rates was observed; deposition during oil firing was negligible compared to coal firing. The deposits are mainly hematite particles embedded in bonding phase, mainly comprising Si, Al, Fe, Ca, and O. Moreover, it was found that the prevailing flue-gas direction determines the formation of the deposits on the probe and that inertial impaction controls the deposition rate. However, this rate can also be affected by the amount of air-borne particles present in the kiln.

  • 43.
    Widman, Susanne
    et al.
    Umeå universitet.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Broström, Markus
    Umeå universitet.
    Early release of NH3 from nitrogen rich fuels: a TG-FTIR study2013In: Proceedings of the 21st EU BC&E - Copenhagen 2013, Florence, Italy, 2013, p. 974-976Conference paper (Other academic)
  • 44.
    Skoglund, Nils
    et al.
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Grimm, Alejandro
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Effects on ash chemistry when co-firing municipal sewage sludge and wheat straw in a fluidized bed: influence on the ash chemistry by fuel mixing2013In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 10, p. 5725-5732Article in journal (Refereed)
    Abstract [en]

    Municipal sewage sludge (MSS) is of interest for co-combustion with problematic fuels, such as agricultural residues, because of its high content of inorganic elements, which may improve combustion properties of such problematic fuels. Ash transformation when co-combusting MSS with the agricultural residue wheat straw was examined using a bench-scale bubbling fluidized bed (5 kW). Wheat straw pellets were combusted with MSS in both a co-pelletized form and co-firing of separate fuel particles. This was performed to examine whether there is any advantage to either approach of introducing MSS together with a problematic fuel. Co-combusting wheat straw with MSS changed the bed agglomeration characteristics from being caused by the formation of low-temperature melting potassium silicates in the fuel ash to being caused by a higher temperature melting bed ash. This shift in ash chemistry had a significant positive effect on the initial defluidization temperature. The cyclone ash and fine particulate matter changed from being dominated by alkali in general and alkali chlorides in specific to an increased phosphate and sulfate formation, which reduces the risk of alkali-related fouling and corrosion. The influence of aluminosilicates may also play a role in the improvement of fuel ash behavior.

  • 45.
    Näzelius, Ida-Linn
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå universitet.
    Boman, Christoffer
    Umeå universitet.
    Hedman, Henry
    Energy Technology Centre, Piteå.
    Samuelsson, Robert
    Sveriges Lantbruksuniversitet.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Influence of peat addition to woody biomass pellets on slagging characteristics during combustion2013In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 7, p. 3997-4006Article in journal (Refereed)
    Abstract [en]

    Upgraded biofuels such as pellets, briquettes, and powder are today commonly used in small as well as large scale appliances. In order to cover an increasing fuel demand new materials such as bark, whole tree assortments, and peat are introduced. These materials have higher ash content which is why they are potentially more problematic compared with stem wood. In general, few studies can be found regarding cocombustion of peat and biomass and in particular where the slagging tendencies are discussed. The overall objective of this study was therefore to determine the influence of peat addition to woody biomass pellets on slagging characteristics. Two different peat assortments (peat A and B) were copelletized separately in four different dry matter levels (0–5–15–30 wt %) into stem wood and energy wood, respectively. Peat A was a traditional Scandinavian fuel peat, with a high ash and Si content (carex), and peat B had a low ash content and relatively high Ca/Si ratio (sphagnum) chosen for its special characteristics. The produced pellets were combusted in a commercial underfed pellet burner (15 kW) installed in a reference boiler. The collected deposits (bottom ash and slag) from the combustion experiments were chemically characterized by scanning electron microscopy (SEM) combined with energy-dispersive X-ray analysis (EDS) and X-ray diffraction (XRD) regarding the elemental distribution and morphology and phase composition, respectively. In addition, the bottom ashes were characterized according to inductively coupled plasma atomic emission spectroscopy (ICP-AES). To interpret the experimental findings chemical equilibrium model calculations were performed. The slagging tendency increased when adding peat into the woody biomasses. Especially sawdust with its relatively low ash and Ca content was generally more sensitive for the different peat assortments. Cofiring with the relatively Si and ash rich peat A resulted in the most severe slagging tendency. A significant increment of the Si, Al, and Fe content and a significant decrement of the Ca content in the slag could be seen when increasing the content of peat A in both woody biomasses. The slagging tendency increased when adding peat A because high temperature melting Ca–Mg oxides react to form more low temperature melting Ca/Mg–Al–K silicates. The slagging tendency was significantly lower when adding the more ash poor peat B, with relatively high Ca/Si ratio, into the woody biomass fuels compared with the peat A mixtures. The slag from the peat B mixings had a slightly higher Ca content compared with the Si content and a clearly higher content of Ca compared with the peat A mixtures. There were still Ca–Mg oxides left in the bottom ash i.e. a less amount of sticky low temperature melting K-silicate rich melt was formed when peat B was added to the woody biomasses.

  • 46.
    Rebbling, Anders
    et al.
    Umeå universitet.
    Piotrowska, Patrycja
    Umeå universitet.
    Boström, Dan
    Umeå universitet.
    Näzelius, Ida-Linn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Krossade gipsplattor som bränsleadditiv vid fastbränsleeldning för minskad risk av askrelaterade driftsproblem - etapp 2 fullskaleförsök i avfallseldad rosterpanna (25 MWt); Slutrapport NWI Dp 4, December 20132013Report (Other academic)
  • 47.
    Piotrowska, Patrycja
    et al.
    Energy Technology and Thermal Process Chemistry, Umeå University.
    Grimm, Alejandro
    Boström, Dan
    Energy Technology and Thermal Process Chemistry, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Krossade gipsplattor som bränsleadditiv vid fastbränsleeldning för minskad risk för askrelaterade driftsproblem - etapp 1 termokemiska modellberäkningar och bänkskaleförsök.: Slutrapport NWI Dp 4, Mars 20132013Report (Other academic)
  • 48.
    Olwa, Joseph
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Pettersson, Esbjörn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Boström, Dan
    Umeå universitet.
    Okure, Mackay
    Makerere University.
    Kjellström, Björn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Potassium retention in updraft gasification of wood2013In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 11, p. 6718−6724-Article in journal (Refereed)
    Abstract [en]

    The release of compounds of K with producer gas during biomass gasification is known to play significant roles in fouling and high-temperature corrosion in boilers and high-temperature heat exchangers as well as blades in gas turbines that use producer gas as fuel. These phenomena are a major setback in the application of biomass fuel in combination with advanced process conditions. Updraft gasification provides gas filtering by the fuel bed with a gas cooling effect, conditions anticipated to create an avenue for K retention in the gasifier. The objective of this study was to determine the K retention potential of such gasifiers during wood gasification. Samples for the determination of the fate of K compounds included in the feedstock were collected from the generated producer gas using Teflon filters and gas wash bottles and also from wall deposits and ash residues. Analyses of samples were carried out using inductively coupled plasma–atomic emission spectrometry/mass spectrometry and X-ray diffraction methods. The finding was that about 99% of K was retained in the gasifier. K was found in the ash samples as a crystalline phase of K2Ca(CO3)2(s) (fairchildite). A possible reaction mechanism leading to the formation of K2Ca(CO3)2 is discussed in the paper. The 1% K understood as released, equivalent to 1200 ppbw content of K entrained in the producer gas stream, exceeds a known limit for application of the gas in conventional gas turbines. This would suggest application of the gas in an externally fired gas turbine system, where some limited K and other depositions in the heat exchanger can be relatively easy to handle.

  • 49.
    Carlborg, Markus
    et al.
    Umeå universitet.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Backman, Rainer
    Umeå universitet.
    Reactions between ash and ceramic lining in entrained flow gasification of wood: exposure studies and thermodynamic considerations2013In: Proceedings of the 21st EU BC&E - Copenhagen 2013, Florence Italy, 2013, p. 446-449Conference paper (Other academic)
    Abstract [en]

    Gasification of biomass in the entrained flow process requires temperatures above 1000°C and pressures above 20 bar. Together with the ash forming elements, a harsh environment is created inside these reactors and degradation of construction material is likely to occur. This will lead to unplanned stops and increased maintenance work resulting in economic loss. In this work, two refractory materials (63 and 83 weight percent alumina) were exposed to synthetic ash composed of K2CO3, CaCO3 and SiO2 to study chemical attack on and interactions with the refractory materials. The exposure went on for 7 days in 1050°C and CO2­atmosphere in a muffle furnace. It was found that potassium (K) is the most active element in attack of the refractories and is transported fastest in the material. A melt composed of K, Ca and Si was formed that prevented penetration of K but it also dissolved aluminum from the refractory materials. X­ray diffraction showed that the crystalline phases leucite, kalsilite, kaliophilite, K(2­x)Al(2­x) SixO4 and wollastonite had formed. Formations of new phases in refractories will cause stress and eventually failure within refractories.

  • 50.
    Skoglund, Nils
    et al.
    Energy Technology and Thermal Process Chemistry, Umeå University.
    Boström, Dan
    Energy Technology and Thermal Process Chemistry, Umeå University.
    Brännvall, Evelina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Kumpiene, Jurate
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Grimm, Alejandro
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Återvinning av fosfor och energi ur avloppsslam genom termisk behandling i fluidiserad bädd; Slutrapport NWI Dp 4, Januari 20132013Report (Other academic)
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