Ändra sökning
Avgränsa sökresultatet
12 1 - 50 av 54
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Ahmadi, Mozhgan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Knoef, Harrie
    Van De Beld, Bert
    Liliedahl, Truls
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Engvall, Klaus
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Development of a PID based on-line tar measurement method: Proof of concept2013Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 113, s. 113-121Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, a proof of concept was conducted for an on-line tar analyzer based on photo ionization detection (PID). Tar model compounds (naphthalene, acenaphthene, acenaphthylene, fluorene, indane and indene) were used for the initial investigation of the analysis method. It was found that the analysis method has a high sensitivity and a linear behavior was observed between the PID response and the tar concentration over a wide concentration span. The on-line tar analysis method was successfully validated against the solid phase adsorption (SPA) method using a real producer gas.

  • 2.
    Andersson, Robert
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Boutonnet, Magali
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Järås, Sven
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Effect of CO2 in the synthesis of mixed alcohols from syngas over a K/Ni/MoS2 catalyst2013Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 107, s. 715-723Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An unsupported K-Ni-MoS2 catalyst for higher alcohol synthesis from syngas (H-2/CO) has been studied during 360 h on stream. It shows a gradual increase in activity with time on stream and some possible reasons for this are discussed in the paper. The main focus of this paper was to study the on the effect of CO2-containing syngas, relative CO2-free syngas under identical reaction conditions and identical inlet H-2 and CO partial pressures (340 degrees C, 100 bar, GHSV = 6920 ml/(g(cat) h)). The effect of increased partial pressure of H-2 and CO was also studied, and to a minor extent also the effect of changed gas hourly space velocity (GHSV). Under the studied conditions, addition of CO2 was found to greatly decrease total product yield, while the selectivities to alcohol and hydrocarbons (C%, CO2-free), respectively, were unchanged. CO2 addition, however, led to a great change in the distribution within the alcohol and hydrocarbon groups. With CO2 added the methanol selectivity increased much while selectivity to longer alcohols decreased. For hydrocarbons the effect is the same, the selectivity to methane is increased while the selectivity to longer hydrocarbons is decreased. It has earlier been shown that product selectivities are greatly affected by syngas conversion level (correlated to outlet concentration of organic products, i.e. alcohols, hydrocarbons etc.) which can be altered by changes in space velocity or temperature. This means that alcohol selectivity is decreased in favor of increased hydrocarbon selectivity and longer alcohol-to-methanol ratio when syngas conversion is increased. At first it might be thought that the selectivity changes occurring when CO2 is present in the feed, just correlate to a decreased organic product concentration in the reactor and that the selectivities with CO2-containing and CO2-free syngas would be identical under constant concentration of organic products in the reactor. However, CO2-addition studies where space velocity was varied showed that significantly lower alcohol selectivity (mainly ethanol selectivity) and increased hydrocarbon selectivity (mainly methane) were found at similar organic outlet concentrations as when CO2-free syngas was feed. Comparing addition of extra H-2 or extra CO, it was found that a high H-2/CO ratio (H-2/CO = 1.52 tested in our case) favors maximum product yield, especially methanol formation, while a lower H-2/CO ratio (H-2/CO = 0.66 tested in our case) leads to higher yield of higher alcohols simultaneously minimizing hydrocarbon and methanol formation.

  • 3.
    Andersson, Robert
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Boutonnet, Magali
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Järås, Sven
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Higher alcohols from syngas using a K/Ni/MoS2 catalyst: Trace sulfur in the product and effect of H2S-containing feed2014Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 115, s. 544-550Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two types of experiments have been performed related to the higher alcohol synthesis from syngas over a K-Ni-MoS2 catalyst which beforehand has been operated for 1000 h on stream in sulfur-free syngas. In the first experimental part, sulfur-free syngas was used as feed and the condensed liquid product was found to contain 67 ppmw sulfur, while the sulfur concentration in the gas was 19 ppmv. The gas phase was found to contain mainly COS and H2S, while the liquid phase contained methanethiol (13.8 ppmw S), ethanethiol (10.6 ppmw S), dimethyl sulfide (21.3 ppmw S), ethyl methyl sulfide (12.2 ppmw S), unidentified sulfur compounds (7.9 ppmw S) together with some dissolved COS (0.5 ppmw S) and H2S (1.2 ppmw S). In the second experimental part, the effect of feeding syngas containing 170 ppm H2S compared to a sulfur-free syngas was studied, while all products were carefully monitored online. The presence of H2S in the syngas was found to increase CO conversion, but the largest change was found in product selectivity. The hydrocarbon selectivity greatly increased at the expense of alcohol selectivity, while the alcohol distribution shifted towards longer alcohols (increased C2+OH/MeOH ratio). From product yields it became clear that most of the increased CO conversion with H2S in the feed was due to increased methane formation (and CO2 formation due to the water-gas shift reaction). The presence of H2S in the feed greatly increased the concentration of all sulfur compounds. Together with COS, formation of thiols (methanethiol and ethanethiol) was especially favored by the presence of H2S. The thioether concentration also increased, however, to a much lower extent.

  • 4. Andrae, Johan C. G.
    Development of a detailed kinetic model for gasoline surrogate fuels2008Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 87, nr 10-11, s. 2013-2022Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A detailed chemical kinetic model to describe the autoignition of gasoline surrogate fuels is presented consisting of the fuels isooctane, n-heptane, toluene, diisobutylene and ethanol. Model predictions have been compared with shock tube ignition delay time data for surrogates of gasoline over practical ranges of temperature and pressure, and the model has been found to be sensitive to both changes in temperature and pressure. Moreover, the model can qualitatively predict the observed synergistic and antagonistic non-linear blending behaviour in motor octane number (MON) for different combinations of primary reference fuels (PRFs) and non-PRFs by correlating calculated autoignition delay times from peak pressures and temperatures in the MON test to experimental MON values. The reasons for the blending behaviour are interpreted in terms autoignition chemistry.

  • 5.
    Baina, Fabiola
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Malmquist, Anders
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Alejo, Lucio
    Fransson, Torsten H.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Extended operability of a commercial air-staged burner using a synthetic mixture of biomass derived gas for application in an externally fired micro gas turbine2015Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 150, s. 664-671Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biomass gasification converts solid biomass into a gaseous fuel that is more versatile and can be used in many applications. However, biomass gasification gas contains some contaminants and inert compounds. The contaminants can cause several problems in the downstream equipment and undesirable emissions while the inert compounds can affect the lower heating value of the gas. Because of these characteristics, there have been difficulties in finding a conversion technology using biomass gasification gas for heat and power generation. In this regard, externally fired gas turbines open a possibility for this combustible gas since due to its configuration, combustion takes place outside the conventional gas turbine cycle. For this reason, combustion studies of biomass derived gas are important. In this work the operability of a commercial air-staged natural gas burner is shown in terms of CO, UHC, and NOX emissions using a synthetic mixture of biomass gasification gas. Two fuel gas mixtures simulating the composition of biomass gasification gas are injected in the combustor. Each fuel gas contains different injection rates of benzene in order to represent tars and to understand their effect on the combustion performance. Additionally, the equivalence ratio is varied in a range of lean conditions in order to find an optimum operation point for the burner studied. The results showed that the presence of polyaromatic hydrocarbons such as benzene reduced the CO concentrations in the exhaust gas while it increased the concentrations of unburned hydrocarbons (UHC) at equivalence ratios lower than 0.68. Additionally, NOX emissions showed a relatively constant trend over the range of equivalence ratios studied for both fuels. It was also observed that NOX emissions increase with the addition of benzene in the fuel gas. An optimum point with regards CO and UHC concentrations was found for the fuels tested.

  • 6.
    Bellais, Michel
    et al.
    KTH, Tidigare Institutioner, Kemiteknik.
    Davidsson, K.O.
    Liliedahl, Truls
    KTH, Tidigare Institutioner, Kemiteknik.
    Sjöström, Krister
    KTH, Tidigare Institutioner, Kemiteknik.
    Pettersson, J. B. C.
    Pyrolysis of large wood particles: a study of shrinkage importance in simulations2003Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 82, nr 12, s. 1541-1548Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Shrinkage models have been developed and included in a model for the pyrolysis of large wood particles. Shrinkage is modelled in three different ways: uniform shrinkage, shrinking shell and shrinking cylinders. These models and a reference model without shrinkage are compared with experimental data for mass loss versus time during pyrolysis of birch cylinders at different temperatures. In the experiments a wood particle was introduced into a pyrolysis furnace held at constant temperature. The particle mass and volume were recorded using a balance and a video camera. Uniform shrinkage slows down the pyrolysis whereas shrinking shell and cylinder models enhance the pyrolysis rate. The effect was sufficiently small to be neglected given the uncertainty about some wood physical properties.

  • 7.
    Bellais, Michel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Sjöström, Krister
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Svenson, J.
    Pettersson, J. B. C.
    Omrane, Alaa
    KTH.
    Ossler, F.
    Aldén, M.
    Fast drying of large wood particles under pyrolysing conditions: experimental study and modellingIngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153Artikel i tidskrift (Övrigt vetenskapligt)
  • 8.
    Binti Munajat, Nur Farizan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Erlich, Catharina
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Fransson, Torsten H.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Correlation of laminar flame speed and lean blowoff limit with the fuel composition of gasified biomassIngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The composition of the product gas produced from a biomass gasification process varies largely depending on several operational factors. The present study gathers the combustion information of different fuel mixtures that resemble the wide range of product gases from biomass gasification process. Two combustion parameters that are laminar flame speed, SL and lean blowoff limit, ERblowoff have been studied as functions of the content of H2 in the fuel mixture as well as the ratios of CO/H2, hydrocarbons/H2 and diluents/H2. From the plotted graphs, mathematical correlations between the parameter studied and the component of the gas mixture have been derived. The equations developed can be used to calculate the laminar flame speed and blowoff equivalent ratio for a wide range of gasified biomass. The graphs show that the H2 content and diluents/H2 ratio have the greatest influence on the laminar flame speed of the gas mixture and higher effect compared to the influence by the ratio of CO/H2 and hydrocarbons/H2. For the lean blowoff limit, the descending order of influence is the ratio of diluents/H2, H2 content and the ratio of CO/H2. While no importance on the lean blowoff limit is observed for the ratio of hydrocarbons/H2.

  • 9.
    Binti Munajat, Nur Farizan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Erlich, Catharina
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Fransson, Torsten H.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Influence of water vapour and tar compound on combustion of simulated gasified biomassIngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Gasification is a thermo‐chemical process which converts biomass fuel into a gaseous mixture, gasified biomass, which can be used in various prime movers. For heat and power generation, using gasified biomass in a combustion device, for example, can give lower undesired emission compared to direct combustion of solid biomass. However, with regards to its variety in composition and lower heating value, the combustion behaviour of gasified biomass may differ from natural gas. The main objective of this study is to investigate the influence of water and tar compound on the combustion of simulated gasified biomass, which mainly contains CO, H2, CH4, CO2, N2. The combustion tests are conducted at atmospheric pressure in a premixed combustor. At a fixed input thermal load, CO and NOx emission levels, combustion temperature, and blowoff characteristics of gasified biomass are observed while varying the volume fraction of water (H2O) or benzene (C6H6) vapours in the fuel mixture. With low H2O level in the fuel mixture, the combustion temperature is almost constant, while NOx emission is decreased compared to dry gasified biomass. On the contrary, the combustion temperature decreases and NOx emission is almost constant at higher H2O content. A temperature limit was observed where CO emission could be maintained at low concentration. The blowoff limit was shifted to higher equivalence ratio. The blowoff temperature was first slightly decreased at lower H2O level and raised when H2O level is further increased. With the content of C6H6, the combustion temperature and NOx emission enhanced, while CO emission was reduced. The blowoff occurs at slightly higher equivalence ratio and temperature compared to gasified biomass without C6H6. The study shows that the presence of H2O and C6H6 in gasified biomass may give positive effects on the emission characteristics during combustion, but also that there are limits for these effects.

  • 10.
    Cardozo Rocabado, Evelyn
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. Facultad de Ciencias y Tecnología (FCyT), Universidad Mayor de San Simon (UMSS), Cochabamba, Bolivia.
    Erlich, Catharina
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Alejo, Lucio
    Universidad Mayor de San Simon.
    Fransson, Torsten
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Combustion of agricultural residues: An experimental study for small-scale applications2014Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 115, s. 778-787Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Energy services could be greatly improved by using of residues from local food industries in small-scale combustion units. Wood pellets are a reliant and proven fuel to be used in small-scale combustion units. However, these units should preferably be able to use different types of biomass depending what it is locally available. Therefore, studies have been focused on exploring the suitability of using agricultural residues for small-scale heat and power generation using direct combustion. This study targets to compare the combustion of different agricultural residues in a single unit designed for wood pellets. The different biomass fuels used are circle divide 6 mm and circle divide 8 mmwood pellets, circle divide 6 mmbagasse pellets, circle divide 6 mmsunflower husk (SFH) pellets and Brazil nut (BN) shells. The results reveal a decrease in the fuel power input, higher oxygen levels in the flue gases and shorter cycles for ash removal when using the agricultural residues. The excess air ratio was calculated based on a mass balance and compared with a standard equation showing a good agreement. CO and NO emission levels as well as the relative conversion of fuel-C to CO were higher for the BN shells and SFH pellets in comparison to the other biomass types. SO2 emission was estimated based on the analysis of unburned sulfur in ash and mass balances; the higher estimated levels corresponded to the BN shells and SFH pellets. All the biomass sorts presented over 95% relative conversion of fuel-C to CO2. Wood pellets and BN shells presented the highest amount of unburned carbon in ash relative to the fuel-C. The relative conversion of fuel-N to NO and fuel-S to SO2 were higher for wood pellets. Bagasse pellets showed similar emission levels and relative conversion efficiency to wood pellets.

  • 11.
    Cifuentes, Luis
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. Univ Duisburg Essen, Chair Fluid Dynam, Inst Combust & Gasdynam IVG, D-47057 Duisburg, Germany..
    Fooladgar, Ehsan
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Duwig, Christophe
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Chemical Explosive Mode Analysis for a Jet-in-Hot-Coflow burner operating in MILD combustion2018Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 232, s. 712-723Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Large Eddy Simulations (LES) of Moderate and Intense Low oxygen Dilution (MILD) combustion of a Jet-in-HotCoflow (JHC) burner were performed using detailed chemistry. On the contrary to traditional flames, where heat release is occurring in very thin fronts, MILD combustion occurs in the distributed reaction regime where the reaction zone is broad, thus, this paper applies a direct Arrhenius closure with detailed chemistry to resolve important details of the fuel oxidation reactions. Comparisons of LES results are in good agreement with experiments, demonstrating that the simulations capture the intermediate species and finite reaction rate effects. A Chemical Explosive Mode Analysis (CEMA) was used to determine the flame structure and to detect the pre-and post-ignition regions, including the contributions to the CEMs analyzing the Explosion Index (EI) and Participation Index (PI). To the best of our knowledge, a detailed study of CEMA on MILD or flameless regime has never been reported. The flame structure was clearly visualized with CEMA, as well as the lean and the rich flame fronts. Different flame zones close to the anchoring points of these turbulent lifted flames were selected and the analysis demonstrates the contributions of dominant chemical species, such as HO2 and O. The reactions related to the dominant local CEM were obtained to highlight the nature of the stabilization in these highly diluted operating conditions.

  • 12.
    Edwards, Ylva
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Väg- och banteknik.
    Tasdemir, Yuksel
    Yozgat Faculty of Engineering and Architecture, Erciyes University, Yozgat, Turkey.
    Isacsson, Ulf
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Väg- och banteknik.
    Rheological effects of commercial waxes and polyphosphoric acid in bitumen 160/220: low temperature performance2006Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 85, nr 7-8, s. 989-997Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effects of adding three commercial waxes and a polyphosphoric acid to three bitumens of 160/220 penetration grade were studied using different types of laboratory equipment, such as dynamic shear rheometer (DSR), bending beam rheometer (BBR), differential scanning calorimeter (DSC), force ductilometer (FD) as well as equipment for determining conventional parameters like penetration, softening point and Fraass breaking point. The paper deals with low-temperature effects, which could influence the thermal cracking resistance of asphalt concrete pavements. The results show that magnitude and type of effect on bitumen rheology depend on the bitumen itself as well as type and amount of additive used. Bitumen composition was found to be of decisive importance. Adding polyethylene wax or polyphosphoric acid, especially to nonwaxy 160/220-penetration grade bitumen, showed positive effects on the rheological behaviour at low temperatures.

  • 13.
    Erlich, Catharina
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Björnbom, Emilia
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Bolado, David
    Giner, Marian
    Fransson, Torsten
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Pyrolysis and gasification of pellets from sugar cane bagasse and wood2006Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 85, nr 10-11, s. 1535-1540Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wood pellets have become a popular form of biomass for power generation and residential heating due to easier handling both for transportation and for feeders in the treatment units, improved conversion and storage possibilities. The research on wood pellets as fuel has also been intensified during the past decade. However, other biomass sorts in pellet form, such as sugar cane bagasse, have not yet been extensively studied, especially not physical effects on the pellets during thermal treatment. Bagasse and wood pellets of different origin and sizes, shredded bagasse and wood chips have been studied in a thermogravimetric equipment to compare the effects of sort, origin, size and form of biomass during slow pyrolysis and steam gasification. Physical parameters such as decrease of volume and mass during treatment, as well as pyrolysis and gasification rates are of primary interest in the study. An important observation from the study is that for pellets the char density decreased during pyrolysis to a minimum around 450 degrees C, but thereafter increased with continued heating. The wood chips behaved differently with a continuous char density decrease during pyrolysis. Another conclusion from the work is that the size of the pellet has larger impact on the shrinkage behaviour throughout the conversion than the raw material, which the pellet is made of.

  • 14.
    Erlich, Catharina
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Öhman, Marcus
    Umeå Universitet.
    Björnbom, Emilia
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Fransson, Torsten
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Thermochemical characteristics of sugar cane bagasse pellets2005Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 84, nr 5, s. 569-575Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pelletisation facilitates utilisation of sugar cane bagasse as a fuel and storage for year-round electricity generation. The present work determines thermochemical characteristics of bagasse pellets of different sizes and origins, using various temperatures (600, 750 and 900 degrees C) and gas flow rates (4, 7 and 10 L/min) with varying concentrations of oxygen (5, 10 and 15 %) in mixtures with nitrogen. Of major interest are the effects of raw material, origin and size of pellets, and the treatment conditions on the rate of pyrolysis and the structure and reactivity of char in combustion. The char yield of the larger pellets of high-ash content bagasse was practically independent of treatment conditions. Smaller pellets gave better mechanical stability of the char but lower reactivity.

  • 15.
    Gonzalez, Angelica V.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Karatzas, Xanthias
    Scania CV AB.
    Pettersson, Lars J.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Autothermal reforming of Fischer-Tropsch diesel over alumina and ceria-zirconia supported catalysts2013Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 107, s. 162-169Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Autothermal reforming (ATR) of synthetic Fischer-Tropsch diesel has been carried out to evaluate the fuel reformer and the catalyst performance at realistic operating conditions. Hydrogen was produced via ATR in a full-scale reformer (ID = 84 mm, L = 400 mm) at 650-750 degrees C. The two monolithic catalysts were sequentially located in the reformer and simultaneously tested. The catalysts were composed of 1:1 wt% Rh:Pt as active metals; CeO2, MgO, Y2O3, and La2O3 were used as promoters. The first catalytic monolith was supported on delta-Al2O3 and the second on CeO2-ZrO2. Fresh samples were characterized by N-2-BET, XRD and H-2-TPR analyses. Catalyst activity was evaluated at O-2/C similar to 0.34-0.45 and H2O/C similar to 2-3. Results show an increased catalyst activity after the second monolithic catalyst due to the effect of steam reforming, water-gas shift reaction (WGS) and higher catalyst reducibility of RhxOy species on the CeO2-ZrO2 mixed oxide as a result of the improved redox properties. Hydrogen concentrations of 42 vol% and fuel conversion of 98% after the CeO2-ZrO2-supported catalyst was obtained at O-2/C = 0.42 and H2O/C = 2.5.

  • 16.
    H. Moud, Pouya
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik. KTH.
    Kantarelis, Efthymios
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    J. Andersson, Klas
    Engvall, Klas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Biomass pyrolysis gas conditioning over an iron-based catalyst for mild deoxygenation and hydrogen production2017Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 211, s. 149-158Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Bio-crude is a renewable source for production of valuable energy carriers. Prior to its utilization, a conditioning step of the raw pyrolysis gas can be beneficial before the bio-crude is converted via catalytic hydrodeoxygenation (HDO) into liquid hydrocarbon products, or via steam reforming (SR) to synthesis gas/hydrogen. An experimental small industrial scale study for the chemistry of atmospheric pressure pyrolysis gas conditioning resulting in bio-crude deoxygenation and a hydrogen-rich gas using an iron-based catalyst without addition of hydrogen or steam is presented and discussed. Following a short catalyst stabilization period with fluctuating bed temperatures, the catalyst operated near 450°C at a space velocity of 1100 h-1 for 8 hours under stable conditions during which no significant catalyst deactivation was observed. Experimental results indicate a 70-80% reduction of acetic acid, methoxy phenols, and catechol, and a 55-65% reduction in non-aromatic ketones, BTX, and heterocycles. Alkyl phenols and phenols were least affected, showing a 30-35% reduction. Conditioning of the pyrolysis gas resulted in a 56 % and a 18 wt% increase in water and permanent (dry) gas yield, respectively, and a 29 % loss of condensable carbon. A significant reduction of CO amount (-38 %), and production of H2 (+1063 %) and CO2 (+36 %) over the catalyst was achieved, while there was no or minimal change in light hydrocarbon content. Probing the catalyst after the test, the bulk phase of the catalyst was found to be magnetite (Fe3O4) and the catalyst exhibited significant water gas shift (WGS) reaction activity. The measured gas composition during the test was indicative of no or very limited Fischer-Tropsch (FT) CO /CO2 hydrogenation activity and this infers that also the active surface phase of the catalyst during the test was Fe-oxide, rather than Fe-carbide. The results show that iron-based materials are potential candidates for application in a pyrolysis gas pre-conditioning step before further treatment or use, and a way of generating a hydrogen-enriched gas without the need for bio-crude condensation.

  • 17.
    Han, Tong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sophonrat, Nanta
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Tagami, Ayumu
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Sevastyanova, Olena
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Mellin, P.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik. KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Characterization of lignin at pre-pyrolysis temperature to investigate its melting problem2019Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 235, s. 1061-1069Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Technical lignin particles melt under relatively low temperature. This results in the problem in the continuous feeding and fluidization during lignin pyrolysis, which in turn limits its utilization on a large scale. In this study, two most available types of lignin have been used to investigate the lignin melting problem, which are Kraft lignin (KL) from pulping process and hydrolysis lignin (HL) from bio-ethanol production process. Elemental composition, thermal property and thermally decomposed derivatives of each sample are tested by elemental analyzer, TGA, DSC, and Py-GC/MS. Morphology, structure and crystal change before and after heat treatment are tested by microscopy, FTIR and XRD. All results suggest that lignin structure determines its melting properties. Kraft lignin from pulping process contains a less cross-linked structure. It melts under heating. On the other hand, hydrolysis lignin from hydrolysis process contains a highly crossed-linked and condensed structure. It does not melt before decomposition under heat treatment. Modifying lignin structure is suggested for the resolution of technical lignin melting problem.

  • 18.
    Han, Tong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sophonrat, Nanta
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Tagami, Ayumu
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. Nippon Paper Ind Co Ltd, Res Lab, Kita Ku, Tokyo 1140002, Japan..
    Sevastyanova, Olena
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Mellin, Pelle
    Swerea KIMAB AB, S-16407 Kista, Sweden..
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Characterization of lignin at pre-pyrolysis temperature to investigate its melting problem2019Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 235, s. 1061-1069Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Technical lignin particles melt under relatively low temperature. This results in the problem in the continuous feeding and fluidization during lignin pyrolysis, which in turn limits its utilization on a large scale. In this study, two most available types of lignin have been used to investigate the lignin melting problem, which are Kraft lignin (KL) from pulping process and hydrolysis lignin (HL) from bio-ethanol production process. Elemental composition, thermal property and thermally decomposed derivatives of each sample are tested by elemental analyzer, TGA, DSC, and Py-GC/MS. Morphology, structure and crystal change before and after heat treatment are tested by microscopy, FTIR and XRD. All results suggest that lignin structure determines its melting properties. Kraft lignin from pulping process contains a less cross-linked structure. It melts under heating. On the other hand, hydrolysis lignin from hydrolysis process contains a highly crossed-linked and condensed structure. It does not melt before decomposition under heat treatment. Modifying lignin structure is suggested for the resolution of technical lignin melting problem.

  • 19. Ilieva, L.
    et al.
    Petrova, P.
    Tabakova, T.
    Pantaleo, G.
    Montes, V.
    Sobczak, J. W.
    Lisowski, W.
    Kaszkur, Z.
    Boutonnet, Magali
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Venezia, A. M.
    Pure hydrogen production via PROX over gold catalysts supported on Pr-modified ceria2014Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 134, s. 628-635Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two series of Pr-doped (5 and 10 at.% Pr) cerium oxides were synthesized by impregnation (IM) and microemulsion method (ME). The Au catalysts (3 wt.%) supported on these oxides were tested in PROX. The samples were characterized by XRD, XPS and TPR measurements. At the operating temperature of the fuel cells (80-120 degrees C) gold catalysts on Pr-doped ceria supports synthesized by IM method exhibited much higher PROX activity as compared to the case of ME method. The observed different catalytic behavior was attributed to the different support preparation affecting the gold particle sizes and the mixed support features. In the case of mixed supports synthesized by IM the size of gold particles established by XRD is smaller and the supply of oxygen evidenced by the obtained TPR results is higher as compared to the gold catalysts on the ME prepared mixed supports. The higher gold dispersion as well as the more defective structure assumed by higher microstrain parameter of ceria lattice (XRD data) due to Pr-doping by IM method, improved both the reducibility and the PROX activity up to 120 degrees C.

  • 20.
    Kalisz, Sylwester
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Pronobis, Marek
    Investigations on fouling rate in convective bundles of coal-fired boilers in relation to optimization of sootblower operation2005Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 84, nr 7-8, s. 927-937Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The article deals with results of full-scale investigations on fouling in convective bundles of chosen types of coal-fired boilers. The boilers tested were: conventional pulverized-coal fired two-pass boilers (two types), a single-pass subcritical (a tower shape) boiler and CFB boiler. Mechanisms of deposit formation and basics of deposit modeling are shortly discussed. An own approach to predict build-up of loose powdery sediments was developed on the basis of the results of full-scale measurements. The correlation for maximum fouling time was obtained by statistical processing of measurement data and is applied in optimization of sootblower system operation. The obtained correlation depends on the following variables: geometric properties of the bundle, fly ash size distribution and basic parameters of the flue gases-all of them are easily accessible in boiler operation.

  • 21.
    Kantarelis, Efthymios
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Blasiak, Wlodzimierz
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Effect of zeolite to binder ratio on product yields and composition during catalytic steam pyrolysis of biomass over transition metal modified HZSM52014Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 122, s. 119-125Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Catalytic pyrolysis of biomass over metal modified zeolites (multifunctional catalysts) is a very promising route for production of hydrocarbons and less oxygenated liquid feedstock suitable for fuels and/or chemicals. In this work the effect of zeolite to binder ratio (Z/B) of a metal modified HZSM5, on products yields and composition during steam pyrolysis of biomass has been investigated. Increased zeolite content resulted in lower liquid yield and increased coke formation; however, more deoxygenated liquids obtained at higher zeolite loadings. Char yield is not significantly affected by the zeolite content. Declining catalytic activity is observed at longer time on stream because of coke deposition. While acidic function of the catalyst deoxygenates carboxylic acids and carbonyls, metal functions seem to selectively convert phenols and methoxy phenols. Competitive steam adsorption on the acid sites of the zeolite seems to lower the conversion to aromatics. The high availability of acid sites, at higher zeolite loading, increases aromatics concentration exponentially. Increased yields of hydrogenated products have been obtained indicating that the Ni-V/HZSM5 catalyst exhibits some hydrogenation activity.

  • 22.
    Laurell Lyne, Åsa
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Wallqvist, Viveca
    SP Technical Research Institute of Sweden, Box 5607, SE-114 86 Stockholm, Sweden .
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Adhesive surface characteristics of bitumen binders investigated by Atomic Force Microscopy2013Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 113, s. 248-256Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bitumen is a complex hydrocarbon whose composition-structure-property relationship is not well-understood. In this paper, microphase-separated topographic morphologies of unaged penetration grade 70/100 bitumen binders have been visualized by means of AFM QNM, and the relationship to local mechanical properties has been demonstrated. AFM QNM is a surface force mapping technique which measures parameters such as topography, adhesion and elastic modulus simultaneously. The resulting data can then be presented as images representing individual or overlaid parameters, e. g. topographic images with an adhesion overlay or topographic images with a modulus overlay. AFM QNM results show that the adhesive forces measured in the region surrounding (peri phase) the periodic topographic features resembling 'bees' (catana phase) and the region in the 'bee' areas are lower than the adhesive force measured in the smooth matrix (para phase). Likewise it was observed that Young's moduli in the region surrounding (peri phase) the 'bees' (catana phase) and in the 'bees' are higher than Young's modulus of the smooth matrix (para phase).

  • 23.
    Li, Jun
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Bonvicini, Giorgio
    Biagini, Enrico
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Tognotti, Leonardo
    Characterization of high-temperature rapid char oxidation of raw and torrefied biomass fuels2015Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 143, s. 492-498Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The promising properties of torrefied biomass provide a valid co-firing option for large percentage biomass utilization in existing coal-fired boilers. Torrefied biomass is expected to have a better combustion stability than raw biomass and similar to that of coal. The present work will characterizes the oxidation properties of torrefied biomass char and compare with that of raw biomass char. The studied two chars are produced from raw and torrefied biomass in an Isothermal Plug Flow Reactor (IPFR) at high temperature and high heating rate, a sufficient residence time is applied for the completion of the high temperature devolatilization. Char oxidation tests are carried out in the IPFR by varying temperature, oxygen concentration and residence time. The reactivity of two studied chars are analyzed and compared with referenced biomass char and coal char, and the impact of torrefaction on char reactivity is also discussed in this paper. Finally, the char oxidation kinetic parameters are determined using a parameter optimization method, and the obtained kinetics are examined by comparing the experimental and predicted mass conversions.

  • 24.
    Li, Jun
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Bonvicini, Giorgio
    Tognotti, Leonardo
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Blasiak, Wlodzimierz
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    High-temperature rapid devolatilization of biomasses with varying degrees of torrefaction2014Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 122, s. 261-269Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Torrefied biomass is a coal-like fuel that can be burned in biomass boilers or co-fired with coal in co-firing furnaces. To make quantitative predictions regarding combustion behavior, devolatilization should be accurately described. In this work, the devolatilization of three torrefied biomasses and their parent material were tested in an isothermal plug flow reactor, which is able to rapidly heat the biomass particles to a maximum temperature of 1400 degrees C at a rate of 10(4) degrees C/s, similar to the conditions in actual power plant furnaces. During every devolatilization test, the devolatilized biomass particles were collected and analyzed to determine the weight loss based on the ash tracer method. According to the experimental results, it can be concluded that biomass decreases its reactivity after torrefaction, and the deeper of torrefaction conducted, the lower the biomass reactivity. Furthermore, based on a two-competing-step model, the kinetic parameters were determined by minimizing the difference between the modeled and experimental results based on the least-squares objective function, and the predicted weight losses exhibited a good agreement with experimental data from biomass devolatilization, especially at high temperatures. It was also detected that CO and H-2 are the primary components of the released volatile matters from the devolatilization of the three torrefied biomasses, in which CO accounts for approximately 45-60%, and H-2 accounts for 20-30% of the total volatile species.

  • 25.
    Li, Jun
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Blasiak, Wlodzimierz
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Ponzio, Anna
    Volumetric combustion of biomass for CO2 and NOx reduction in coal-fired boilers2012Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 102, s. 624-633Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To meet the urgent environmental targets, substituting coal with biomass has been considered to be an effective and promising method over the last decades. In this paper, a new concept of volumetric combustion is proposed and further developed to achieve 100% fuel switching to biomass in large scale coal-fired boilers. Volumetric combustion not only changes the in-furnace flow but also affects the combustion reactions by the intensive mixing and internal recirculation of the flue gases. Firstly, the volumetric combustion properties of the wood pellets were investigated experimentally. An Aspen model was then used to thermodynamically describe and study the volumetric combustion with three different types of fuel, and the emission properties of CO2 and NOx were compared. Finally, two applications of volumetric combustion were discussed. It is concluded that the wood pellets ignited and combusted much faster than the coal pellets and had a larger combustion volume when combusted under lower oxygen concentration conditions, and the ignition time was almost independent of the oxygen concentration when the oxidizer was preheated to 1000 degrees C. In addition, the NOx emissions decreased as the recirculation ratio of the flue gas increased, and as the percentage of biomass used in co-firing increased, the amount of flue gas that needs to be recycled for reduction of NOx decreased. Thus, the volumetric combustion is beneficial as it reduces the operation cost of NOx reduction. The volumetric combustion would be an attractive technology for co-firing a large proportion of biomass in coal-fired boilers with high boiler efficiency and effective emissions reduction.

  • 26.
    Mellin, Pelle
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Kantarelis, Efthymios
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Computational fluid dynamics modeling of biomass fast pyrolysis in a fluidized bed reactor, using a comprehensive chemistry scheme2014Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 117, nr Part A, s. 704-715Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The CFD modeling for fast pyrolysis has previously focused on the major pyrolysis products; liquid, charand gas. This paper introduces a new approach to biomass pyrolysis; integrating a complex scheme of reactions including formation of such components as levoglucosan. The 3-D simulation takes into account the complex breakdown of each biomass subcomponent, the fluid dynamics of the process as well as the heat and momentum transfer of three Eulerian phases.

    The pyrolysis products include reference species that reflects the composition of the bio oil, gas fraction and char fraction. A number of reactions are in addition applied to account for the thermal cracking of tar compounds and the final compositions are compared to experimental yields. The results show that the predicted pyrolysis products reflect the experimental yields satisfactorily, apart from the water content which is under predicted. Most importantly though, the approach is computationally feasible and it should be useful for future work.

  • 27.
    Moud, Pouya H.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Andersson, K. J.
    Lanza, Roberto
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Pettersson, J. B. C.
    Engvall, Klas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Effect of gas phase alkali species on tar reforming catalyst performance: Initial characterization and method development2015Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 154, s. 95-106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In thermochemical conversion of biomass to synthesis gas and biofuels, the effect of varying gas phase alkali concentrations on tar reforming catalyst performance in combination with gas phase sulfur and chlorine is largely unknown. The current study demonstrates a new methodology for investigating gas phase alkali adsorption and presents results for early stage adsorption on a Ni-based catalyst under realistic industrial conditions. The experiments were carried out using pine pellets as feedstock in a setup consisting of a 5 kW atmospheric bubbling fluidized bed gasifier, a high temperature hot gas filter and a catalytic reactor - all operating at 850 °C. A potassium chloride solution was atomized with an aerosol generator, and the produced submicrometer KCl particles were continuously introduced to the catalytic reactor where they rapidly evaporated to form KCl (g). The accurate dosing of gas-phase alkali was combined with elimination of transient effects in catalytic performance due to catalyst sintering and S adsorption, and results for K uptake in relation to sulfur uptake were obtained. Different KCl levels in the gas phase demonstrates different initial uptake of K on the catalyst surface, which at low K coverage (θK) is approximately linearly proportional to time on stream. The results also show a clear suppressing effect of sulfur adsorption on potassium uptake. Indications of a slow approach to K equilibration on the catalyst were observed. The potential of the developed methodology for detailed studies under close to industrial conditions is discussed.

  • 28.
    Moud, Pouya H.
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Kantarelis, Efthymios
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Processteknologi.
    Andersson, Klas J.
    Engvall, Klas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Processteknologi.
    Biomass pyrolysis gas conditioning over an iron-based catalyst for mild deoxygenation and hydrogen production2018Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 211, s. 149-158Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bio-crude is a renewable source for production of valuable energy carriers. Prior to its utilization, a conditioning step of the raw pyrolysis gas can be beneficial before the bio-crude is converted via catalytic hydrodeoxygenation (HDO) into liquid hydrocarbon products, or via steam reforming (SR) to synthesis gas/hydrogen. An experimental small industrial-scale study for the chemistry of atmospheric pressure pyrolysis gas conditioning resulting in bio-crude deoxygenation and a hydrogen-rich gas is presented and discussed. This study is performed using an iron-based catalyst without addition of hydrogen or steam. Following a short catalyst stabilization period with fluctuating bed temperatures, the catalyst operated near 450 °C at a space velocity of 1100 h−1 for 8 h under stable conditions during which no significant catalyst deactivation was observed. Experimental results indicate a 70–80% reduction of acetic acid, methoxy phenols, and catechol, and a 55–65% reduction in non-aromatic ketones, BTX, and heterocycles. Alkyl phenols and phenols were least affected, showing a 30–35% reduction. Conditioning of the pyrolysis gas resulted in a 56% and an 18 wt% increase in water and permanent (dry) gas yield, respectively, and a 29% loss of condensable carbon. A significant reduction of CO amount (−38%), and production of H2(+1063%) and CO2 (+36%) over the catalyst was achieved, while there was no or minimal change in light hydrocarbon content. Probing the catalyst after the test, the bulk phase of the catalyst was found to be magnetite (Fe3O4) and the catalyst exhibited significant water gas shift (WGS) reaction activity. The measured gas composition during the test was indicative of no or very limited Fischer-Tropsch (FT) CO/CO2 hydrogenation activity, and this infers that the active surface phase of the catalyst during the test also was Fe-oxide, rather than Fe-carbide. The results show that iron-based materials are potential candidates for application in a pyrolysis gas pre-conditioning step before further treatment or use, and a way of generating a hydrogen-enriched gas without the need for bio-crude condensation.

  • 29.
    Nemanova, Vera
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Abedini, Araz
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Liliedahl, Truls
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Engvall, Klas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Co-gasification of petroleum coke and biomass2014Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 117, nr Part A, s. 870-875Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gasification may be an attractive alternative for converting heavy oil residue - petroleum coke into valuable synthetic gas. Due to the low reactivity of petroleum coke, it is maybe preferable to convert it in combination with other fuels such as biomass. Co-gasification of petroleum coke and biomass was studied in an atmospheric bubbling fluidised bed reactor and a thermogravimetric analyser (TGA) at KTH Royal University of Technology. Biomass ash in the blends was found to have a catalytic effect on the reactivity of petroleum coke during co-gasification. Furthermore, this synergetic effect between biomass and petcoke was observed in the kinetics data. The activation energy Ea determined from the Arrhenius law for pure petcoke steam gasification in the TGA was 121.5 kJ/mol, whereas for the 50/50 mixture it was 96.3, and for the 20/80 blend - 83.5 kJ/mol.

  • 30.
    Norberg Samuelsson, Lina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Moriana, Torró Rosana
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Bäbler, Matthäus U.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Engvall, Klas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Model-free rate expression for thermal decomposition processes: The case of microcrystalline cellulose pyrolysis2015Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 143, s. 438-447Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We explore the possibility to derive a completely model-free rate expression using isoconversional methods. The Friedman differential method (Friedman, 1964) and the incremental integral method by Vyazovkin (2001) were both extended to allow for an estimation of not only the apparent activation energy but also the effective kinetic prefactor, defined as the product of the pre-exponential factor and the conversion function. Analyzing experimental thermogravimetric data for the pyrolytic decomposition of microcrystalline cellulose, measured at six different heating rates and three different initial sample masses (1.5-10 mg), revealed the presence of secondary char forming reactions and thermal lag, both increasing with increased sample mass. Conditioning of the temperature function enables extraction of more reliable prefactors and we found that the derived kinetic parameters show weak dependence on initial sample mass. Finally, by successful modeling of quasi-isothermal experimental curves, we show that the discrete rate expression estimated from linear heating rate experiments enables modeling of the thermal decomposition rate without any assumptions regarding the chemical process present. These findings can facilitate the design and optimization of industrial isothermal biomass fed reactors.

  • 31.
    Nordgreen, Thomas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Liliedahl, Truls
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Sjöström, Krister
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Metallic iron as a tar breakdown catalyst related to atmospheric, fluidised bed gasification of biomass2006Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 85, nr 06-maj, s. 689-694Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tar formation is a major drawback when biomass is converted in a gasifier to obtain gas aimed for utilisation in power production plants or for production of chemicals. Catalytic cracking is an efficient method to diminish the tar content in the gas mixture. In this study, the capability of metallic iron and iron oxides to catalytically crack tars has been experimentally examined. To obtain metallic iron, small grains of hematite (Fe2O3) were placed in a secondary reactor downstream the gasifier and reduced in situ prior to catalytic operation. The fuel used in the atmospheric fluidised bed gasifier was Swedish birch with a moisture content of approximately 7 wt%. The influence of temperature in the range 700-900 degrees C and), values (i.e. equivalence ratio, ER) between 0 and 0.20 have been investigated. In essence, the results show that raising the temperature in the catalytic bed to approximately 900 degrees C yields almost 100% tar breakdown. Moreover, increasing the). value also improves the overall tar cracking activity. The iron oxides did not demonstrate any catalytic activity.

  • 32.
    Nordgreen, Thomas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Nemanova, Vera
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Engvall, Klas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Sjöström, Krister
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Iron-based materials as tar depletion catalysts in biomass gasification: Dependency on oxygen potential2012Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 95, nr 1, s. 71-78Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A study has been performed using experimental iron based granules as a tar breakdown catalyst in a biomass gasification gas. Previous examinations established that metallic iron located in a separate catalytic bed reactor has a stronger influence on the tar content and composition in the product gas than their corresponding iron oxides. The results from the present study show that tar diminution in the product gas is dependent on temperature, catalyst material and oxygen potential. Typically, values of 50-75% tar reduction were achieved when varying the catalytic bed temperature between 750 and 850 degrees C. Also, the oxidation state of the catalyst material has an influence on the tar content and gas composition in the gas. When changing the gasification temperature from 800 degrees C to 850 degrees C the oxygen potential in the producer gas also changes, resulting in a transition from oxidative to reductive conditions in the gas. This implies that when the gasification temperature is 800 degrees C, the catalyst is transformed from its metallic state to the iron oxide, wustite. Consequently, the tar reduction capacity of the catalyst is reduced by approximately 20%. In view of the overall results it can be concluded that the catalysts in their metallic states in general exhibits a better tar cracking capacity than their corresponding oxides. The iron material used is sintered iron powders manufactured at Hoganas AB, Sweden. The iron materials were dispensed in the metallic state.

  • 33. Payri, R.
    et al.
    Gimeno, J.
    Cuisano, J.
    Arco, Javier
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Hydraulic characterization of diesel engine single-hole injectors2016Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 180, s. 357-366Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Due to world trend on the emission regulations and greater demand of fuel economy, the research on advanced diesel injector designs is a key factor for the next generation diesel engines. For that reason, it is well established that understanding the effects of the nozzle geometry on the spray development, fuel-air mixing, combustion and pollutants formation is of crucial importance to achieve these goals. In the present research, the influence of the injector nozzle geometry on the internal flow characteristics is studied. For this purpose, ten single-hole diesel injectors differing in the orifices degree of conicity (five cylindrical, five conical) but with similar nozzle flow capacity have been characterized geometrically (measurements of nozzle outlet section) and hydraulically. The mass flow and momentum flux rates have been measured for a wide range of experimental conditions. Special attention is given to study the cavitation phenomenon since the cylindrically-shaped nozzle orifices are expected to propitiate cavitation due to abrupt changes in flow direction. The study has been carried out with two different fuels: n-dodecane and commercial diesel, thereby the effect of the fuel properties is also analyzed. The results show that the measured nozzle outlet diameters are higher than the nominal specification for both nozzle types. As expected, the onset of cavitation on the cylindrical nozzles has been identified causing a reduction on the injected mass for all tested conditions. The effective diameter for the cylindrical nozzles have been found to be around 175 μm (geometrical diameter ≈212 μm) and around 185 μm (geometrical diameter ≈191 μm) for the conical ones. Finally, the higher density of diesel with respect to n-dodecane have resulted on mass flow rates around 8% over the n-dodecane values for the same test conditions.

  • 34.
    Persson, Mikael
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Matsuura, H.
    Sridhar, S.
    Visualization of Carbon Particles in Reactive Gas and Slag EnvironmentsIngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153Artikel i tidskrift (Refereegranskat)
  • 35.
    Ponzio, Anna
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Senthoorselvan, Sivalingam
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Blasiak, Wlodzimierz
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Eriksson, O.
    Nitrogen release during thermochemical conversion of single coal pellets in highly preheated mixtures of oxygen and nitrogen2009Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 88, nr 6, s. 1127-1134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this investigation, single coal particles (pellets) were combusted in highly preheated oxidants (8731273 K) with oxygen concentrations ranging from 0% to 100%, using a small scale' batch reactor. In base of the experimental results, the influence of oxygen concentration and oxidizer temperature on total mass conversion, the release of fuel nitrogen and the fraction of fuel nitrogen that is oxidized to NOx, is discussed. For oxygen concentration 5-21%, the rate of the thermochemical conversion was shown to be almost independent oxygen concentration when oxidant temperatures of 1073-1273 K were used. The opposite was true for an oxidant temperature of 873 K. Thus there appears to be an oxidant temperature above which devolatilisation is controlled by convective heat transfer rather than reaction. Further it was shown that the release of fuel nitrogen was promoted by an increased oxygen concentration (from 5% to 21% at 1273 K) and an increase of oxidant temperature (from 1073 K to 1273 K at 21% oxygen). An estimate of the devolatilisation of nitrogen from the measured pellet temperature indicated that the devolatilisation of nitrogen is significantly delayed with respect to other components. In fact, during the very initial part of the thermochemical conversion, most released nitrogen appeared to follow the route via char rather than via devolatilisation. Favorable conditions for No reduction thanks to a prompt devolatilisation contemporarily to a release of fuel nitrogen via the char route was believed to be one of the explanation for the evidenced low ratios between NOx emissions and fuel nitrogen released, particularly in the beginning of the experiment. The fact that the amount of released fuel nitrogen that is oxidized to NOx was shown to decrease with increasing oxidant temperatures from 1073 K to 1273 K supports this interpretation, though a higher temperature of the oxidant creates higher devolatilisation rates.

  • 36.
    Ponzio, Anna
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Senthoorselvan, Sivalingam
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Blasiak, Wlodzmierz
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Eriksson, Ola
    LKAB, Kiruna.
    Ignition of single coal particles in high-temperature oxidizers with various oxygen concentrations2008Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 87, nr 6, s. 974-987Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this investigation, coal pellets were combusted using a high temperature oxidizer with varying oxygen concentration, using a small scale batch reactor able to preheat the oxidizer to 1273 K. In base of the experimental results, the influence of oxygen concentration on the ignition mechanism, the solid temperature inside the particle at the moment of ignition, the mass lost at the moment of the ignition and ignition time is analyzed and discussed. A theoretical basis for the division of the conditions tested into three ignition regimes is developed and a formula for the prediction of the ignition time directly from the material and oxidizer temperature and oxygen concentration is proposed.

  • 37.
    Samuelsson, Lina N.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Bäbler, Matthaus U.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Moriana, Rosana
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    A single model-free rate expression describing both non-isothermal and isothermal pyrolysis of Norway Spruce2015Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 161, s. 59-67Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A strictly isoconversional rate expression has been derived for pyrolysis of biomass. This rate expression, derived from non-isothermal thermogravimetric experiments using heating rates 2-10 K/min, can successfully predict the conversion rates of experimental data at heating rates 1-100 K/min and quasiisothermal experiments at 539-650 K. The methodology used is based on an extension of the incremental integral method by Vyazovkin (2001). Being able to derive an intrinsic reaction rate expression from non-isothermal data, without any assumption regarding the chemical processes present, opens up for the possibility to model industrial pyrolysis reactors, with a variety of temperature profiles.

  • 38.
    Tang, Bing
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Väg- och banteknik.
    Isacsson, Ulf
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Väg- och banteknik.
    Chemical characterization of oil-based asphalt release agents and their emissions2006Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 85, nr 9, s. 1232-1241Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Four commercial asphalt release agents were chemically characterized using different analytical methods. Functional groups and molecular weight distributions were determined by fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), gel permeation chromatography (GPC) and mass spectrometry (MS). General compositions of the agents were obtained as petroleum hydrocarbons, fatty acid methyl esters (FAMEs), fatty acids and glycerides using gas chromatography-mass spectrometry (GC-MS) and MS probe inlet method. The contents of health related analytes, such as aromatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs), were determined. Asphalt release agents emission was investigated using thermogravimetric analysis (TGA) and headspace solid-phase microextraction (HS-SPME) The emission proneness as well as emission level of aromatic hydrocarbons from these agents were compared. The results obtained were used for ranking the agents with regard to health hazards.

  • 39.
    Umeki, Kentaro
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Biswas, Amit Kumar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Blasiak, Wlodzimierz
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Yoshikawa, Kunio
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Validity and Limitation of the shrinking core model for the apparent pyrolysis rate of wood particleIngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153Artikel i tidskrift (Övrigt vetenskapligt)
  • 40. Valtorta, D.
    et al.
    Poulikakos, L.
    Partl, Manfred
    EMPA, Swiss Federal Laboratories for Material Testing and Research, Switzerland.
    Mazza, E.
    Rheological Properties of Polymer Modified Bitumen from Long-term Field Tests2007Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 86, nr 7-8, s. 938-948Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The possibility to monitor aging of pavements and bituminous binders directly on the operative field, under their typical environmental conditions, can contribute to better understand the factors influencing the aging process, can be used for material optimization and to improve the performance behavior of bituminous binders. The high frequency torsional rheometer (HFTR) described in this paper is a useful device to study the time evolution of the theological properties of bituminous binders during field tests. In comparison with prevailing rheometers, the HFTR is inexpensive and, due to its portability and operative frequency (5 kHz) that allows measurements to be unaffected by traffic induced low frequencies, is a useful tool for continuous monitoring of field tests. The HFTR device and the measurement technique are described in this paper. The extraction of the theological parameters from the experiments is made through analytical and finite element models that reproduce the particular conditions of the field tests. In this study, the long-term aging of an asphaltic plug joint of a highway bridge is investigated with an HFTR over three consecutive years of exposure to environmental conditions. The evolution of the theological properties of the plug joint material, containing styrene-butadiene-styrene polymer modified bitumen, is quantified in terms of the complex shear modulus G*, showing a progressive material hardening and an increase in the temperature susceptibility of the binder

  • 41.
    Velasco, Jorge A.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Fernandez, Cristhian
    Lopez Nina, Luis Gagarin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi. UMSA Universidad Mayor de San Andres, Bolivia.
    Cabrera, Saul
    Boutonnet, Magali
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Järås, Sven G.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Catalytic partial oxidation of methane over nickel and ruthenium based catalysts under low O2/CH4 ratios and with addition of steam2015Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 153, s. 192-201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Catalytic partial oxidation (CPO) of methane to synthesis gas at low O2/CH4 ratios and in the presence of steam was investigated over nickel and ruthenium catalysts supported on hydrotalcite-derived materials. The influence of catalyst properties and composition on activity, temperature profile and deactivation by carbon formation was examined. All catalyst presented high methane conversions, close to the values predicted by thermodynamic equilibrium and such conversions increased in proportion to the metal surface of the catalyst tested. The temperature profiles at O2/CH4 = 0.2 and H2O/CH4 = 0.3 and a constant exit temperature of 700 °C varied depending on the catalyst type; it was possible to examine catalyst deactivation from the change in the shape of the profile of each catalyst. Since the O2/CH4 and H2O/CH4 ratios were low, the risk or potential for carbon formation was thermodynamically favorable along the entire catalytic bed; however, this potential was qualitatively higher when the temperature profile of the catalyst presented a pronounced maximum peak at the inlet of the reactor. During catalytic reaction tests and methane decomposition experiments, the ruthenium catalyst did not formed appreciable amounts of carbon while a bimetallic catalyst (Ni and Ru) form only small amounts (in comparison with the nickel catalysts). For the ruthenium catalyst, a higher O2/CH4 ratio favored conversions closer to the equilibrium value. The observations presented in this work indicate that during the CPO of methane, at low O2/CH4 ratios and in the presence of steam, the catalyst properties and composition will have a substantial influence on the extent of the combustion and reforming reactions along the catalytic bed. This will in turn define the temperature profile, and therefore the risk or potential for carbon formation; this risk might effectively be overcome by the use of ruthenium-containing catalysts.

  • 42.
    Vriesman, Peter
    et al.
    KTH, Tidigare Institutioner, Kemiteknik.
    Heginuz, Eloise
    KTH, Tidigare Institutioner, Kemiteknik.
    Sjöström, Krister
    KTH, Tidigare Institutioner, Kemiteknik.
    Biomass gasification in a laboratory-scale AFBG: influence of the location of the feeding point on the fuel-N conversion2000Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 79, nr 11, s. 1371-1378Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of the feeding point on the conversion of fuel-nitrogen (fuel-N) was studied in an atmospheric fluidized bed gasifier. A comparison between feeding into the bed and feeding from the top of the reactor was made for different temperatures and equivalence ratios. Special emphasis was given to the distribution of fuel-N into NH3, HCN and char. The results show no influence of the feeding point on the nitrogen conversion to HCN and on the amount of nitrogen in char. Top feeding, however, results in lower conversion of fuel-N to NH3. The feeding points, and therefore the contact between the fuel particles and the surrounding oxygen-containing gas, as well as the oxygen concentration itself, are of great importance for the formation and destruction of NH3.

  • 43. Wolf, J.
    et al.
    Anheden, M.
    Yan, Jinyue
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Comparison of nickel- and iron-based oxygen carriers in chemical looping combustion for CO2 capture in power generation2005Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 84, nr 7-8, s. 993-1006Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In chemical looping combustion (CLC), a solid oxygen carrier circulates between two fluidised bed reactors and transports oxygen from the combustion air to the fuel: thus, the fuel is not mixed with air and an inherent CO2 separation occurs. In this paper, CLC is integrated in a natural gas fired combined cycle (NGCC). In this system, nickel- and iron-based oxygen carriers are compared regarding the system's electrical and exergy efficiencies. Furthermore, the feasibility of CLC in two interconnected pressurised fluidised bed reactors (IPFBR) is studied for both oxygen carriers. The hypothetical layout plus dimensions of the IPFBR is presented for a capacity of 800 MW input of natural gas. Finally, top-firing is proposed as an option to overcome the apparent limitation in operating temperature of the reactor equipment and/or the oxygen carriers. The results indicate that there is no significant difference in the system's efficiency if both oxygen carriers could operate at the same temperature. However, CLC seems easier to be technically realised in an IPFBR with a nickel-based oxygen carrier.

  • 44.
    Yu, Q. Z.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Brage, Claes O.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Chen, G. X.
    Sjöström, Krister
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    The fate of fuel-nitrogen during gasification of biomass in a pressurised fluidised bed gasifier2007Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 86, nr 4, s. 611-618Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The distribution of fuel-nitrogen in gases, tar and char from gasification of biomass in a pressurised fluidised bed gasifier was investigated. Four species of biomass: birch, Salix, Miscanthus and Reed canary grass were gasified at 0.4 MPa and 900 degrees C. Oxygen-enriched nitrogen was used as fluidising agent. As a reference, gasification of Daw Mill coal was also carried out under the same experimental conditions. The experimental results illustrate that both the nature of the original fuels and the chemical structure of the nitrogen in the fuel have influence on the distribution of fuel-nitrogen in gases (NH3, HCN, NO), tar and char under the employed experimental conditions. The present work also shows that the types of nitrogen heterocyclic compounds (NHCs) in the tar from different kinds of biomass are the same and the major compound is pyridine. However, the distribution of the various NHCs in the tar from the four species of biomass varies: the higher the content of fuel-nitrogen, the higher the concentration of two-ring NHCs in the tar. An effective method for extracting NHCs from the acidic absorption of the product gas was introduced in the present work. The method makes use of solid phase extraction (SPE) by a silica-based C-18 tube to extract the NHCs which subsequently were analysed by gas chromatography (GC) with flame ionisation detection (FID). The recovery and reproducibility of the SPE technique for NHCs is discussed.

  • 45.
    Yu, Q. Z.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Brage, Claes O.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Nordgreen, Thomas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Sjöström, Krister
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Effects of Chinese dolomites on tar cracking in gasification of birch2009Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 88, nr 10, s. 1922-1926Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To minimize tar in the producer gas from birch gasification at 700, 750 and 800 degrees C, four Chinese dolomites (Zhenjiang, Nanjing, Shanxi, Anhui) and a Swedish dolomite (Sala) used as reference were studied in a laboratory-scale atmospheric fluidized bed gasifier. The gasifier was equipped with a downstream fixed catalyst bed. The results imply that all dolomites but Anhui dolomite effectively decompose tar into gases. Anhui dolomite showed a low catalytic capacity to crack tar produced at 700 and 800 degrees C. The influence of various ratios of steam to biomass on tar content in the producer gas after passing over dolomite was studied. The tar cracking efficiency of the dolomites did not improve significantly with the ratio of steam to biomass in the region 0.11-0.52.

  • 46. Yu, Xinhai
    et al.
    Wen, Zhenzhong
    Li, Hongliang
    Tu, Shan-Tung
    Yan, Jinyue
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Transesterification of Pistacia chinensis oil for biodiesel catalyzed by CaO-CeO2 mixed oxides2011Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 90, nr 5, s. 1868-1874Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study investigates the use of CaO-CeO2 mixed oxides as solid base catalysts for the transesterification of Pistacia chinensis oil with methanol to produce biodiesel. These CaO-CeO2 mixed-oxide catalysts were prepared by an incipient wetness impregnation method and characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. The cerium improved the heterogeneous catalytic stability remarkably due to the defects induced by the substitution of Ca ions for Ce ions on the surface. The best catalyst was determined to be C0.15-973 (with a Ce/Ca molar ratio of 0.15 and having been calcined at 973 K), considering its catalytic and anti-leaching abilities. The effects of reaction parameters such as the methanol/oil molar ratio, the amount of catalyst amount and the reaction temperature were also investigated. For the C0.15-973 regenerated after five reuses, the biodiesel yield was 91%, which is slightly less than that of the fresh sample. The test results revealed that the CaO-CeO2 mixed oxides have good potential for use in the large-scale biodiesel production.

  • 47. Yu, Xinhai
    et al.
    Wen, Zhenzhong
    Lin, Ying
    Tu, Shan-Tung
    Wang, Zhengdong
    Yan, Jinyue
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Intensification of biodiesel synthesis using metal foam reactors2010Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 89, nr 11, s. 3450-3456Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study presents a technology for continuous and high-efficiency alkali-catalyzed biodiesel synthesis using a metal foam reactor combined with a passive mixer. A metal foam reactor with higher pore density produces smaller droplets that result in higher efficiency of biodiesel synthesis. Compared with conventional stirred reactors, the time for high methyl ester conversion can be shortened remarkably by the use of metal foam reactors. Experimental results reveal that a metal foam reactor of 50 pores per inch exhibits an energy consumption per gram biodiesel of 1.01 J g(-1), merely 1.69% and 0.77% of energy consumption of the zigzag micro-channel and conventional stirred reactors, respectively. Moreover, biodiesel yield per reactor for the metal foam reactor is approximately 60 times that of the zigzag micro-channel reactor, thus overcoming the problem of numbering up an excessive number of reactors in the application. These results indicate the great potential of metal foam reactors in small-fuel biodiesel processing plants for distributive applications.

  • 48.
    Zanzi Vigouroux, Rolando
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Sjöström, Krister
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Björnbom, Emilia
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk reaktionsteknik.
    Rapid high-temperature pyrolysis of biomass in a free-fall reactor1996Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 75, nr 5, s. 545-550Artikel i tidskrift (Refereegranskat)
  • 49. Zevenhoven-Onderwater, M.
    et al.
    Backman, R.
    Skrifvars, B. J.
    Hupa, M.
    Liliedahl, Truls
    KTH, Tidigare Institutioner, Kemiteknik.
    Rosén, Christer
    KTH, Tidigare Institutioner, Kemiteknik.
    Sjöström, Krister
    KTH, Tidigare Institutioner, Kemiteknik.
    Engvall, Klas
    Hallgren, A.
    The ash chemistry in fluidised bed gasification of biomass fuels. Part II: Ash behaviour prediction versus bench scale agglomeration tests2001Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 80, nr 10, s. 1503-1512Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper is part II in a series of two. Ash behaviour modelling of the gasification of four biomass fuels is compared with pilot-scale experiments carried out in a pressurised fluidised bed gasifier at the Royal Institute of Technology (KTH) and an atmospheric test rig of Termiska Processer AB (TPS). Experiments were provocative with respect to agglomeration of the bed material. Thus, in the experiments, the agglomeration was allowed to happen without any corrective changes in the operation. Small-scale experiments showed clear defluidisation in five cases. Some degree of bed disturbance or agglomeration occurred in seven out of 13 cases. In nine of these cases, agglomerates were also found in the samples analysed with SEM/EDX analyses. In six out of 13 cases, the thermodynamic multi-phase multi-component equilibrium calculations were in agreement with SEM/EDX analysis, i.e. predicted fort-nation of agglomerates. In two cases, no or small amounts of agglomerates were predicted, nor were these found with SEM/EDX analysis. In two cases out of 13, the modelling predicted some degree of agglomeration while no agglomerates could be detected with SEM/EDX analysis. However, in these cases, agglomerates were found in the pilot-scale experiments. Thus it is shown that the thermodynamic multi-phase multi-component equilibrium calculations are a useful prediction tool for the formation of agglomerates in (pressurised) fluidised bed gasification of biomass fuels thereby enhancing the understanding of the chemistry involved.

  • 50. Zevenhoven-Onderwater, Maria
    et al.
    Backman, Rainer
    Skrifvars, Bengt-Johan
    Hupa, Miko
    Liliendahl, Truls
    Rosén, Christer
    Sjöström, Krister
    Engvall, Klas
    KTH, Tidigare Institutioner (före 2005), Kemiteknik.
    Hallgren, Anders
    KTH, Tidigare Institutioner (före 2005), Kemiteknik.
    The ash chemistry in fluidised bed gasification of biomass fuels. Part I: Predicting the chemistry of melting ashes and ash-bed material interaction2001Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 80, nr 10, s. 1489-1502Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper is part I in a series of two describing the modelling of the ash-chemistry of seven biomass fuels under reducing, pressurised conditions in fluidised bed gasification by means of thermodynamic multi-phase multi-component equilibrium (TPCE) calculations. The fuels considered were Salix, a Scandinavian forest residue, Miscanthus, Reed Canary Grass, Eucalyptus, Arundo Donax and Lucerne. The composition and amount of phases have been calculated for the gasification of the fuel as such and in presence of an excess amount of calcite, dolomite, magnesium olivine sand and sand by using TPCE calculations in a temperature interval of 600-900°C and a pressure of 10 bar. It was found that interaction of inorganic compounds released from the fuels with bed material is a prerequisite for the formation of bed agglomerates. The presence of an excess of dolomite decreased the amount of alkali components in the bed, thereby increasing the amount of alkali components volatilised. A silica bed, however, binds most alkali released from the fuel, retaining it in the bed as low melting alkali silicates. The chances of experiencing operating problems due to bed agglomeration may increase hereby significantly. Calculations at atmospheric pressure show that the amounts of melt present will be smaller when compared to pressurised conditions, thereby decreasing the chances of bed agglomeration. In a pressurised gasifier using calcite or dolomite as bed material a small amount of an alkali carbonate rich melt can be expected at temperatures above 620°C with each of the seven biomass fuels fired. In silica-rich cases such as when firing Miscanthus, Reed Canary Grass, Arundo Donax or using a Si-rich bed material a melt can be expected at temperatures above 770°C. The amount of melt is rather high, i.e. 12-100% of the original ash formed. In the case of a magnesium olivine sand bed an alkali melt can be expected at 620°C. At temperatures above 800°C, a silicate melt can form as well. The amount of melt was hi gh, i.e. 60-300% of the original ash formed, showing a significant contribution of the bed material.

12 1 - 50 av 54
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf