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  • 1. Trubetskaya, Anna
    Publisher’s Note to Modeling the influence of potassium content and heating rate on biomass pyrolysis [Appl. Energy J. 194 (2017) 199–211]2017Other (Other academic)
  • 2.
    Trubetskaya, Anna
    et al.
    Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Bygning 229, Kgs. Lyngby 2800, Denmark.
    Arendt Jensen, Peter
    Degn Jensen, Anker
    Glarborg, Peter
    Hofmann Larsen, Flemming
    Larsen Andersen, Mogens
    Characterization of free radicals by electron spin resonance spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures2016In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 94, p. 117-129Article in journal (Refereed)
    Abstract [en]

    The concentration and type of free radicals from the decay (termination stage) of pyrolysis at slow and fast heating rates and at high temperatures (above 1000 degrees C) in biomass char have been studied. A room temperature electron spin resonance spectroscopy study was conducted on original wood, herbaceous biomass, holocelluloses, lignin and their chars, prepared at high temperatures in a wire mesh reactor, an entrained flow reactor, and a tubular reactor. The radical concentrations in the chars from the decay stage range up between 7.10(16) and 1.5.10(18) spins g(-1). The results indicated that the biomass major constituents (cellulose, hemicellulose, lignin) had a minor effect on remaining radical concentrations compared to potassium and silica contents. The higher radical concentrations in the wheat straw chars from the decay stage of pyrolysis in the entrained flow reactor compared to the wood chars were related to the decreased mobility of potassium in the char matrix, leading to the less efficient catalytic effects of potassium on the bond-breaking and radical re-attachments. The high Si levels in the rice husk caused an increase in the char radical concentration compared to the wheat straw because the free radicals were trapped in a char consisting of a molten amorphous silica at heating rates of 10(3)-10(4) K s(-1). The experimental electron spin resonance spectroscopy spectra were analyzed by fitting to simulated data in order to identify radical types, based on g-values and line widths. The results show that at high temperatures, mostly aliphatic radicals (g = 2.0026-2.0028) and PAH radicals (g = 2.0027-2.0031) were formed.

  • 3.
    Trubetskaya, Anna
    et al.
    Division of Energy Science, Luleå University of Technology, 97187 Luleå, Sweden.
    Beckmann, Gert
    Wadenbäck, Johan
    Holm, Jens Kai
    Velaga, Sitaram P.
    Weber, Roman
    One way of representing the size and shape of biomass particles in combustion modeling2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 206, p. 675-683Article in journal (Other academic)
    Abstract [en]

    This study aims to provide a geometrical description of biomass particles that can be used in combustion models. The particle size of wood and herbaceous biomass was compared using light microscope, 2D dynamic imaging, laser diffraction, sieve analysis and focused beam reflectance measurement. The results from light microscope and 2D dynamic imaging analysis were compared and it showed that the data on particle width, measured by these two techniques, were identical. Indeed, 2D dynamic imaging was found to be the most convenient particle characterization method, providing information on both the shape and the external surface area. Importantly, a way to quantify all three dimensions of biomass particles has been established. It was recommended to represent a biomass particle in combustion models as an infinite cylinder with the volume-to-surface ratio (V/A) measured using 2D dynamic imaging.

  • 4.
    Trubetskaya, Anna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kling, Jens
    Brown, Avery
    Tompsett, Geoffrey
    Umeki, Kentaro
    Effects of Lignocellulosic Compounds on the Yield, Nanostructure and Reactivity of Soot from Fast Pyrolysis at High Temperatures2017Conference paper (Other academic)
  • 5.
    Trubetskaya, Anna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hofmann Larsen, Flemming
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ståhl, Kenny
    Umeki, Kentaro
    Potassium and soot interaction in fast biomass pyrolysis at high temperatures2018In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 225, p. 89-94Article in journal (Refereed)
    Abstract [en]

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

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