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| 2. |
- Trubetskaya, Anna, et al.
(författare)
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Comparison of high temperature chars of wheat straw and rice husk with respect to chemistry, morphology and reactivity
- 2016
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 86, s. 76-87
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Tidskriftsartikel (refereegranskat)abstract
- Fast pyrolysis of wheat straw and rice husk was carried out in an entrained flow reactor at high-temperatures (1000–1500) °C. The collected char was analyzed using X-ray diffractometry, N2-adsorption, scanning electron microscopy, particle size analysis with CAMSIZER XT, 29Si and 13C solid-state nuclear magnetic resonance spectroscopy and thermogravimetric analysis to investigate the effect of inorganic matter on the char morphology and oxygen reactivity. The silicon compounds were dispersed throughout the turbostratic structure of rice husk char in an amorphous phase with a low melting temperature (≈730 °C), which led to the formation of a glassy char shell, resulting in a preserved particle size and shape of chars. The high alkali content in the wheat straw resulted in higher char reactivity, whereas the lower silicon content caused variations in the char shape from cylindrical to near-spherical char particles. The reactivities of pinewood and rice husk chars were similar with respect to oxidation, indicating less influence of silicon oxides on the char reactivity.
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| 3. |
- Trubetskaya, Anna, et al.
(författare)
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Effect of fast pyrolysis conditions on biomass solid residues at high temperatures
- 2016
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Ingår i: Fuel processing technology. - Amsterdam : Elsevier. - 0378-3820 .- 1873-7188. ; 143, s. 118-129
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Tidskriftsartikel (refereegranskat)abstract
- Fast pyrolysis of wood and straw was conducted in a drop tube furnace (DTF) and compared with corresponding data from a wire mesh reactor (WMR) to study the influence of temperature (1000-1400)°C, biomass origin (pinewood, beechwood, wheat straw, alfalfa straw), and heating rate (103 °C/s, 104 °C/s) on the char yield and morphology. Scanning electron microscopy (SEM), elemental analysis, and ash compositional analysis were applied to characterize the effect of operational conditions on the solid residues (char, soot) and gaseous products. The char yield from fast pyrolysis in the DTF setup was 3 to 7% (daf) points lower than in the WMR. During fast pyrolysis pinewood underwent drastic morphological transformations, whereas beechwood and straw samples retained the original porous structure of the parental fuel with slight melting on the surface. The particle size of Danish wheat straw char decreased in its half-width with respect to the parental fuel, whereas the alfalfa straw char particle size remained unaltered at higher temperatures. Soot particles in a range from 60 to 300 nm were obtained during fast pyrolysis. The soot yield from herbaceous fuels was lower than from wood samples, possibly due to differences in the content of lignin and resin acids.
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| 7. |
- Trubetskaya, Anna, et al.
(författare)
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Effects of several types of biomass fuels on the yield, nanostructure and reactivity of soot from fast pyrolysis at high temperatures
- 2016
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Ingår i: Applied Energy. - Oxford : Elsevier. - 0306-2619 .- 1872-9118. ; 171, s. 468-482
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Tidskriftsartikel (refereegranskat)abstract
- This study presents the effect of biomass origin on the yield, nanostructure and reactivity of soot. Soot was produced from wood and herbaceous biomass pyrolysis at high heating rates and at temperatures of 1250 and 1400 °C in a drop tube furnace. The structure of solid residues was characterized by electron microscopy techniques, X-ray diffraction and N2 adsorption. The reactivity of soot was investigated by thermogravimetric analysis. Results showed that soot generated at 1400 °C was more reactive than soot generated at 1250 °C for all biomass types. Pinewood, beechwood and wheat straw soot demonstrated differences in alkali content, particle size and nanostructure. Potassium was incorporated in the soot matrix and significantly influenced soot reactivity. Pinewood soot particles produced at 1250 °C had a broader particle size range (27.2–263 nm) compared to beechwood soot (33.2–102 nm) and wheat straw soot (11.5–165.3 nm), and contained mainly multi-core structures.
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| 8. |
- Trubetskaya, Anna, et al.
(författare)
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Influence of fast pyrolysis conditions on yield and structural transformation of biomass chars
- 2015
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 140, s. 205-214
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Tidskriftsartikel (refereegranskat)abstract
- Fast pyrolysis of biomass (wood, straw, rice husk) and its major components (cellulose, hemicellulose, lignin) was conducted in a wire mesh reactor. The aim of this study was to understand the influence of temperature (350-1400 ∗ C), heating rate (10-3000 ∗ C/s), particle size (0.05-2 mm) and holding time (1-4 s) on the char morphology and char yield. Scanning electron microscopy (SEM) and elemental analysis were conducted to determine the effect of operating conditions on char softening and melting during pyrolysis. The char yield decreased with heating rate for rates ≤ 600 ∗ C/s; above this value a similar biomass char yield was obtained. The potassium content affected the char yield stronger than other minerals, while the distribution of the three major biomass constituents (cellulose, hemicellulose, lignin) affected the char yield only to a minor degree. Moreover, it was found that the heat treatment temperature had a larger influence on the char yield than the heating rate. Scanning electron microscopy indicated different types of biomass char plasticization influenced by the applied temperatures, heating rates, particle sizes and holding times, except for the rice husk char that formed chars with a structure similar to the parental fuel at all conditions. The less severe morphological changes of rice husk char were attributed to a high silica content.
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| 9. |
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| 10. |
- Berdugo Vilches, Teresa, 1985, et al.
(författare)
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Shedding light on the governing mechanisms for insufficient CO and H2 burnout in the presence of potassium, chlorine and sulfur
- 2020
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 273
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Tidskriftsartikel (refereegranskat)abstract
- Based on the experiences of insufficient burnout in industrial fluidized bed furnaces despite adequate mixing and availability of oxidizer, the influence of potassium on CO and H2 oxidation in combustion environments was investigated. The combustion environments were provided by a laminar flame burner in a range relevant to industrial furnaces, i.e. 845 °C to 1275 °C and excess air ratios ranging from 1.05 to 1.65. Potassium, in the form of KOH, was homogeneously introduced into the hot gas environments to investigate its effect on the radical pool. To quantitatively determine key species that are involved in the oxidation mechanism (CO, H2, KOH, OH radicals, K atoms), a combination of measurement systems was applied: micro-gas chromatography, broadband UV absorption spectroscopy and tunable diode laser absorption spectroscopy. The inhibition effect of potassium on CO and H2 oxidation in excess air was experimentally confirmed and attributed to the chain-terminating reaction between KOH, K atoms and OH radicals, which enhanced the OH radical consumption. The addition of chlorine or sulfur could reduce the concentrations of KOH and K atoms and consequently eliminated the inhibition on CO and H2 oxidation. Existing kinetic mechanisms underestimate the inhibiting effect of potassium and they fail to predict the effect of temperature on CO and H2 concentration when potassium and sulfur co-exist. This work advances the need to revise existing kinetic mechanisms to fully capture the interplay of K and S in the oxidation of CO and H2 in industrial fluidized bed furnaces.
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