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  • 1.
    Johansson, Ann-Christine
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Iisa, Kristiina
    National Renewable Energy Laboratory, USA.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Ben, Haoxi
    National Renewable Energy Laboratory, USA.
    Pilath, Heidi
    National Renewable Energy Laboratory, USA.
    Deutch, Steve
    National Renewable Energy Laboratory, USA.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Öhrman, Olov G.W.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Fractional condensation of pyrolysis vapors produced from Nordic feedstocks in cyclone pyrolysis2017In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 123, p. 244-254Article in journal (Refereed)
    Abstract [en]

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

  • 2.
    Johansson, Ann-Christine
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Öhrman, Olov G.W.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Experiences of pilot scale cyclone pyrolysis2017In: European Biomass Conf. Exhib. Proc., ETA-Florence Renewable Energies , 2017, no 25thEUBCE, p. 952-955Conference paper (Refereed)
    Abstract [en]

    Fast pyrolysis is a promising thermochemical technology for converting biomass to energy, chemicals, and fuels. At RISE ETC, an industrially relevant pyrolysis pilot plant has been designed, constructed, and operated since 2011. The pilot plant is based on an externally heated cyclone reactor where both the pyrolysis reaction and the separation of products take place. The reactor design has shown to be beneficial since it produces oil with relatively low concentrations of inorganics. Pyrolysis of different Nordic biomasses, both forestry and agricultural, have been studied using the pilot plant and the results indicate that it is especially suitable for low grade fuels. The oil is collected in two separate steps, and the received two oil fractions have different chemical and physical properties, which opens up the possibility to use selected fractions in targeted applications. Oil fractionation has also been studied further in a separate fractional condensation system and the results show that it is possible to separate larger energy-rich lignin-derived material; medium-sized; and light water soluble compounds already in the oil collection step. The pilot plant has worked as a platform for pyrolysis research and for building up competence in the pyrolysis area. 

  • 3.
    Johansson, Ann-Christine
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Öhrman, Olov
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Jilvero, Henrik
    Stena Metall, Sweden.
    Co-pyrolysis of woody biomass and plastic waste in both analytical and pilot scale2018In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 134, p. 102-1113Article in journal (Refereed)
    Abstract [en]

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

  • 4.
    Johansson, Ann-Christine
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Wiinikka, Henrik
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Sandström, Linda
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Marklund, Magnus
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Öhrman, Olov G. W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Narvesjö, Jimmy
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Characterization of pyrolysis products produced from different Nordic biomass types in a cyclone pilot plant2016In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 146, p. 9-19Article in journal (Refereed)
    Abstract [en]

    Pyrolysis is a promising thermochemical technology for converting biomass to energy, chemicals and/or fuels. The objective of the present paper was to characterize fast pyrolysis products and to study pyrolysis oil fractionation. The products were obtained from different Nordic forest and agricultural feedstocks in a pilot scale cyclone pyrolysis plant at three different reactor temperatures. The results show that the main elements (C, H and O) and chemical compositions of the products produced from stem wood, willow, forest residue and reed canary grass are in general terms rather similar, while the products obtained from bark differ to some extent. The oil produced from bark had a higher H/Ceff ratio and heating value which can be correlated to a higher amount of pyrolytic lignin and extractives when compared with oils produced from the other feedstocks. Regardless of the original feedstock, the composition of the different pyrolysis oil fractions (condensed and aerosol) differs significantly from each other. However this opens up the possibility to use specifically selected fractions in targeted applications. An increased reactor temperature generally results in a higher amount of water and water insoluble material, primarily as small lignin derived oligomers, in the produced oil.

  • 5.
    Lestander, Torbjörn A.
    et al.
    SLU Swedish University of Agricultural Sciences, Sweden.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Öhrman, Olov
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Thyrel, Mikael
    SLU Swedish University of Agricultural Sciences, Sweden.
    Characterization of fast pyrolysis bio-oil properties by near-infrared spectroscopic data2018In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 133, p. 9-15Article in journal (Refereed)
    Abstract [en]

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

  • 6.
    Molinder, Roger
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Sandström, Linda
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Wiinikka, Henrik
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Characteristics of Particles in Pyrolysis Oil2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 11, p. 9456-9462Article in journal (Refereed)
    Abstract [en]

    Particles filtered out of pyrolysis oil produced through fast pyrolysis of stem wood, willow, reed canary grass, bark, and forest residue were characterized using scanning electron microscopy and energy-dispersive spectroscopy with the aim of identifying particle categories and discussing transport mechanisms of particles and inorganics into the oil. Particles filtered out of both the condensed and the aerosol fractions of the oil displayed three types of morphology: (i) char-like structures (1-15 μm), (ii) spheres (100 nm to 1 μm), and (iii) irregularly shaped residue (50-500 nm). The char-like structures were identified as char. The spheres and irregularly shaped residue shared morphology and composition with tar balls and organic particles with inorganic inclusions. These particles could have formed either during the fast pyrolysis stage or through precipitation from the oil during storage. All particles consisted mainly of C and O but also small amounts of inorganics. The particles from the aerosol fraction of the oil had higher inorganics content than the particles from the condensed fraction. The results were discussed, and suggested transport mechanisms of inorganics into particles were presented.

  • 7.
    Pedersen, Thomas Helmer
    et al.
    Aalborg University, Denmark.
    Jensen, Claus Uhrenholt
    Steeper Energy ApS, Denmark.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Rosendahl, Lasse Aistrup
    Aalborg University, Denmark.
    Full characterization of compounds obtained from fractional distillation and upgrading of a HTL biocrude2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 202, p. 408-419Article in journal (Refereed)
    Abstract [en]

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

  • 8.
    Persson, H.
    et al.
    KTH Royal Institute of Technology, Sweden.
    Han, T.
    KTH Royal Institute of Technology, Sweden.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Xia, W.
    KTH Royal Institute of Technology, Sweden.
    Evangelopoulos, P.
    KTH Royal Institute of Technology, Sweden.
    Yang, W.
    KTH Royal Institute of Technology, Sweden.
    Fractionation of liquid products from pyrolysis of lignocellulosic biomass by stepwise thermal treatment2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 154, p. 346-351Article in journal (Refereed)
    Abstract [en]

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

  • 9.
    Sandström, Linda
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Johansson, Ann-Christine
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Wiinikka, Henrik
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Öhrman, Olov G. W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Marklund, Magnus
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Pyrolysis of Nordic biomass types in a cyclone pilot plant — Mass balances and yields2016In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 152, p. 274-284Article in journal (Refereed)
    Abstract [en]

    Fast pyrolysis of biomass results in a renewable product usually denoted pyrolysis oil or bio-oil, which has been suggested to be used as a direct substitute for fuel oil or as a feedstock for production of transportation fuels and/or chemicals. In the present work, fast pyrolysis of stem wood (originated from pine and spruce), willow, reed canary grass, brown forest residue and bark has been performed in a pilot scale cyclone reactor. The experiments were based on a biomass feeding rate of 20 kg/h at three different reactor temperatures. At the reference condition, pyrolysis of stem wood, willow, reed canary grass, and forest residue resulted in organic liquid yields in the range of 41 to 45% w/w, while pyrolysis of bark resulted in lower organic liquid yields. Two fractions of pyrolysis oil were obtained, denoted as the condensed and the aerosol fraction. Most of the water soluble molecules were collected in the condensed fraction, whereas the yield of water insoluble, heavy lignin molecules was higher in the aerosol fraction. Based on the results of the present work, willow, reed canary grass and forest residue are considered as promising raw materials for production of pyrolysis oil in a cyclone reactor.

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

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

  • 11.
    Sophonrat, Nanta
    et al.
    KTH Royal Institute of Technology, Sweden.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Zaini, Ilman N.
    KTH Royal Institute of Technology, Sweden.
    Yang, Weihong
    KTH Royal Institute of Technology, Sweden.
    Stepwise pyrolysis of mixed plastics and paper for separation of oxygenated and hydrocarbon condensates2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 229, p. 314-325Article in journal (Refereed)
    Abstract [en]

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

  • 12.
    Wiinikka, Henrik
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Johansson, Ann-Christine
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Öhrman, Olov G.W.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Fate of inorganic elements during fast pyrolysis of biomass in a cyclone reactor2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 203, p. 537-547Article in journal (Refereed)
    Abstract [en]

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

  • 13.
    Winikka, Henrik
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Toth, Pal
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Jansson, Kjell
    Stockholm University, Sweden.
    Molinder, Roger
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Broström, Markus
    Umeå University, Sweden.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Lighty, JoAnn S.
    University of Utah, USA.
    Weiland, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Particle formation during pressurized entrained flow gasification of wood powder: Effects of process conditions on chemical composition, nanostructure, and reactivity2018In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 189, p. 1339-1351Article in journal (Refereed)
    Abstract [en]

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

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