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  • 1.
    Ahmadi, Mozhgan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Brage, Claes O.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Knoef, H.
    Van De Beld, B.
    Development of an on-line tar measurement method based on photo ionization technique2011In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 176, no 1, p. 250-252Article in journal (Refereed)
    Abstract [en]

    This paper presents work in progress for development of an on-line method based on PID (Photo Ionization Detector) for quantitative measurement of tar from biomass gasification. To calibrate the method the PID signals are compared to quantitative data of individual tar compounds obtained by an established reference method. The measured response factors for the model tar compounds demonstrated very good linearity. The PID approach was tested on-line with real producer gases from an atmospheric fluidized bed gasifier operated at 800-900 °C. The results suggest that PID can be used for continuous on-line tar measurement of product gases from biomass gasification.

  • 2.
    Ahmadi, Mozhgan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Brage, Claes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Develompent of an online tar measuring method using ionization potential2010Conference paper (Refereed)
  • 3.
    Ahmadi, Mozhgan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Brage, Claes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Knoef, Harri A.M.
    Van de Beld, Bert
    Development of an online tar measuring method for quantitative analysis of biomass producer gas2009Conference paper (Refereed)
  • 4.
    Alvfors, Per
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Arnell, Jenny
    IVL.
    Berglin, Niklas
    Innventia.
    Björnsson, Lovisa
    LU.
    Börjesson, Pål
    LU.
    Grahn, Maria
    Chalmers/SP.
    Harvey, Simon
    Chalmers.
    Hoffstedt, Christian
    Innventia.
    Holmgren, Kristina
    IVL.
    Jelse, Kristian
    IVL.
    Klintbom, Patrik
    Kusar, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Lidén, Gunnar
    LU.
    Magnusson, Mimmi
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Pettersson, Karin
    Chalmers.
    Rydberg, Tomas
    IVL.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Stålbrand, Henrik
    LU.
    Wallberg, Ola
    LU.
    Wetterlund, Elisabeth
    LiU.
    Zacchi, Guido
    LU.
    Öhrman, Olof
    ETC Piteå.
    Research and development challenges for Swedish biofuel actors – three illustrative examples: Improvement potential discussed in the context of Well-to-Tank analyses2010Report (Other academic)
    Abstract [en]

    Currently biofuels have strong political support, both in the EU and Sweden. The EU has, for example, set a target for the use of renewable fuels in the transportation sector stating that all EU member states should use 10% renewable fuels for transport by 2020. Fulfilling this ambition will lead to an enormous market for biofuels during the coming decade. To avoid increasing production of biofuels based on agriculture crops that require considerable use of arable area, focus is now to move towards more advanced second generation (2G) biofuels that can be produced from biomass feedstocks associated with a more efficient land use. Climate benefits and greenhouse gas (GHG) balances are aspects often discussed in conjunction with sustainability and biofuels. The total GHG emissions associated with production and usage of biofuels depend on the entire fuel production chain, mainly the agriculture or forestry feedstock systems and the manufacturing process. To compare different biofuel production pathways it is essential to conduct an environmental assessment using the well-to-tank (WTT) analysis methodology. In Sweden the conditions for biomass production are favourable and we have promising second generation biofuels technologies that are currently in the demonstration phase. In this study we have chosen to focus on cellulose based ethanol, methane from gasification of solid wood as well as DME from gasification of black liquor, with the purpose of identifying research and development potentials that may result in improvements in the WTT emission values. The main objective of this study is thus to identify research and development challenges for Swedish biofuel actors based on literature studies as well as discussions with the the researchers themselves. We have also discussed improvement potentials for the agriculture and forestry part of the WTT chain. The aim of this study is to, in the context of WTT analyses, (i) increase knowledge about the complexity of biofuel production, (ii) identify and discuss improvement potentials, regarding energy efficiency and GHG emissions, for three biofuel production cases, as well as (iii) identify and discuss improvement potentials regarding biomass supply, including agriculture/forestry. The scope of the study is limited to discussing the technologies, system aspects and climate impacts associated with the production stage. Aspects such as the influence on biodiversity and other environmental and social parameters fall beyond the scope of this study. We find that improvement potentials for emissions reductions within the agriculture/forestry part of the WTT chain include changing the use of diesel to low-CO2-emitting fuels, changing to more fuel-efficient tractors, more efficient cultivation and manufacture of fertilizers (commercial nitrogen fertilizer can be produced in plants which have nitrous oxide gas cleaning) as well as improved fertilization strategies (more precise nitrogen application during the cropping season). Furthermore, the cultivation of annual feedstock crops could be avoided on land rich in carbon, such as peat soils and new agriculture systems could be introduced that lower the demand for ploughing and harrowing. Other options for improving the WTT emission values includes introducing new types of crops, such as wheat with higher content of starch or willow with a higher content of cellulose. From the case study on lignocellulosic ethanol we find that 2G ethanol, with co-production of biogas, electricity, heat and/or wood pellet, has a promising role to play in the development of sustainable biofuel production systems. Depending on available raw materials, heat sinks, demand for biogas as vehicle fuel and existing 1G ethanol plants suitable for integration, 2G ethanol production systems may be designed differently to optimize the economic conditions and maximize profitability. However, the complexity connected to the development of the most optimal production systems require improved knowledge and involvement of several actors from different competence areas, such as chemical and biochemical engineering, process design and integration and energy and environmental systems analysis, which may be a potential barrier.

  • 5.
    Bellais, Michel
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Davidsson, K.O.
    Liliedahl, Truls
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Pettersson, J. B. C.
    Pyrolysis of large wood particles: a study of shrinkage importance in simulations2003In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 82, no 12, p. 1541-1548Article in journal (Refereed)
    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.

  • 6.
    Bellais, Michel
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Liliedahl, Truls
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Influence of different shrinkage models and fuel geometry on heat transfer during rapid pyrolysis of solid biofuels2002In: Proceedings of the Finnish-Swedish FlameDays: Adapting Combustion Technology to New Fuels and Fuel Mixtures,september 2002, Vaasa, Finland: The Finnish and Swedish National Committees of The International Flame Research Foundation, IFRF, 2002Conference paper (Refereed)
  • 7.
    Bellais, Michel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    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 modellingIn: Fuel, ISSN 0016-2361, E-ISSN 1873-7153Article in journal (Other academic)
  • 8. Brage, C.
    et al.
    Yu, Q. Z.
    Chen, G. X.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Tar evolution profiles obtained from gasification of biomass and coal2000In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 18, no 1, p. 87-91Article in journal (Refereed)
    Abstract [en]

    The tar content of the product gases from gasification of biomass is one of the major factors affecting the subsequent process stages. In this work, evolution profiles of the main tar constituents, i.e. benzene, toluene, indene, naphthalene and phenol were obtained during about 1 h gasification runs of biomass and coal in a pressurised fluidised-bed at 700 and 900 degrees C, 0.4 MPa. Sampling and analysis was achieved, using the solid-phase adsorption (SPA) method, previously developed in our laboratory. Our main objectives were: (1) to illustrate the usefulness of the SPA method; (2) to shed new light on the main factors governing tar evolution. It was found that temperature and the type of feedstock used mainly affected tar yields. For both biomass and coal the concentration of tar products decreased with increasing run time at a rate that was fastest initially. This behaviour, which was much more pronounced for coal, provides evidence that char catalytically affects tar evolution. Accordingly, char accumulates in the bed to a various extent depending on fuel and gradually approaching steady state. Biomass char, contrary to coal char, is readily oxidised during gasification, and thus only small steady-state amounts are available to catalyse tar cracking reactions.

  • 9.
    Brage, Claes
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Yu, Qizhuang
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    An new method for the analysis of heavy tar in raw producer gases from biomass gasifiers2007In: Proceeding of the 15th European Biomass Conferense, Berlin, Germany, 7-11 May 2007, 2007Conference paper (Refereed)
  • 10. Davidsson, K. O.
    et al.
    Pettersson, J. B. C.
    Bellais, Michel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    The Pyrolysis Kinetics of a Single Wood Particle2008In: Progress in Thermochemical Biomass Conversion, Wiley-Blackwell, 2008, p. 1129-1142Chapter in book (Other academic)
    Abstract [en]

    Experimental results from birchwood and pinewood pyrolysis in a new single particle reactor are presented. Apparent lunetic parameters for the mass-loss of wood particles (5-800 mg) at temperatures from 300 to 860°C are determined. Kinetic parameters for the evolution of CO, CO2, H2O, H2 and CH4, are also established. The drylng process was examined and it was found that drying and pyrolysis increasingly overlap in time as temperature rises and that the overlap is substantial above 450 °C.

  • 11. Davidsson, K. O.
    et al.
    Pettersson, J. B. C.
    Bellais, Michel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, Superseded Departments, Chemical Engineering and Technology.
    The pyrolysis kinetics of a single wood particle2001In: IEA bioenergy, Vol. 2, p. 1129-1142Article in journal (Refereed)
  • 12.
    Engvall, Klas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kusar, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Pettersson, Lars J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Upgrading of raw gas from biomass and waste gasification: Challenges and opportunities2011In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 54, no 13-15, p. 949-959Article, review/survey (Refereed)
    Abstract [en]

    The depletion of fossil fuel-based resources and concerns for increasing emissions of CO2 call for newways of producing environmentally- friendly substitutes for motor fuels and chemicals. Thermo-chemical conversion of biomass andwaste using gasification is a strong candidate tomeet these challenges. For efficient and cost-effective application of this technique, novel solutions for hot gas cleaning are needed. This review highlights some important areas for improvement of upgrading technologies for pressurised fluidised bed gasification systems using biomass as a fuel.

  • 13.
    Gustavsson, Catrin
    et al.
    KTH, Superseded Departments, Pulp and Paper Technology.
    Sjöstrom, Karin
    KTH, Superseded Departments, Pulp and Paper Technology.
    Al-Dajani, Wafa
    KTH, Superseded Departments, Pulp and Paper Technology.
    The influence of cooking conditions on the bleachability and chemical structure of kraft pulps1999In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 14, no 1, p. 71-81Article in journal (Refereed)
    Abstract [en]

    The purpose of this investigation was primarily td investigate how variations in cooking conditions in the kraft pulping of softwood influence the subsequent bleaching, and secondly to study the relationship between the bleaching response and the chemical structure of the pulp. The cooking variables studied were hydroxide ion concentration, hydrogen sulfide ion concentration and cooking temperature. The pulps had the same kappa number after the cook, about 20, and were oxygen delignified to about kappa number 8 before bleaching. The influence of the cooking variables on the TCF-bleachability was studied in an AZQP*- and in a QPQP*-sequence (A=acid treatment, Z=ozone stage, Q=chelating agent stage, P*=peroxide stage with the addition of magnesium ions). All three cooking variables studied influenced the TCF-bleachability, but to different extents. The bleachability was improved by increased temperature for low chemical charges, but not at higher chemical charges. When [HS-] was increased the QPQP*-bleachability was improved but the AZQP*-bleachability was not affected. When [HO-] was varied a bleachability maximum was seen for the intermediate hydroxide ion concentration. The content of hexenuronic acid in the pulp after cooking could be reduced by using high initial [HO-], low initial [HS-] and a long cooking time. A high content of beta-O-4 structures in the unbleached residual lignin was found to contribute to a better bleachability of the pulp. However, the phenolic hydroxyl content could not be related to the bleaching response.

  • 14. Knoef, Harri A.M
    et al.
    Van de Beld, Bert
    Ahmadi, Mozhgan
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Brage, Claes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Development of an online tar measuring method for quantitative analysis of biomass producer gas2009In: Proceedings of the 17th European Biomass conference & Exhibition, 2009Conference paper (Refereed)
  • 15.
    Liliedahl, Truls
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Rosén, Christer
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Defluidisation of fluidised beds during gasification of biomass2011In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 35, no SUPPL. 1, p. S63-S70Article in journal (Refereed)
    Abstract [en]

    Defluidisation and agglomeration during fluidised bed gasification of biomass is analysed and discussed. It is argued that the agglomeration and defluidisation processes, in principle, closely resemble those that determine the behaviour of glass during glass processing. Crucial properties for working with glass melts are the viscosity, stickiness, surface tension, etc. It is, however, (very) difficult to theoretically quantify these properties through thermodynamics or other theoretical means. Hence it will be problematic to theoretically predict agglomeration and defluidisation. Models for predicting defluidisation must therefore probably be of an empirical nature. As a consequence of this, a number of fluidised bed gasification tests were empirically analysed with respect to defluidisation. In total 145 tests were evaluated; of these 51 defluidised or exhibited some kind of bed disturbance. A number of fuels and bed materials were included in the analysis using a multivariate statistical approach.Based on the analysis an empirical regression equation for predicting the defluidisation temperature during fluidised bed gasification is suggested.

  • 16. Link, Siim
    et al.
    Arvelakis, Stelios
    Paist, Aadu
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Atmospheric fluidized bed gasification of untreated and leached olive residue, and co-gasification of olive residue, reed, pine pellets and Douglas fir wood chips2012In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 94, p. 89-97Article in journal (Refereed)
    Abstract [en]

    The fluidized bed gasification of untreated and pre-treated olive residue and pre-treated olive residue mixed with reed, pine pellets and Douglas fir wood chips is studied. Leaching is used as a pre-treatment process targeted on the elimination of alkali metals such as K and Na as well as chlorine to reduce/eliminate the ash-related problems during gasification. The leaching pre-treatment process could affect the producer gas composition toward the lower or higher yield of CO and H-2 of the producer gas depending on the moisture content of parent fuels. The lower total tar yield of the producer gas in the case of leached olive residue was observed compared to untreated olive residue. At the same time, there are present wider varieties of different tar components in the producer gas of the leached olive residue compared to the untreated one. The distinctions in tar composition and content between the leached and untreated olive residue are attributed to the alkali and alkali earth metal and chorine chemistry affected by leaching pre-treatment. The addition of woody fuels and reed at elevated proportions resulted in the lower LHV value compared to the leached olive residue. The tar content of the producer gas is seen to increase adding reed and woody fuels to the leached olive residue, i.e. the producer gas contained additional variety of tar components whereas phenol becomes one of the key components determining the total tar content, apart from benzene, toluene and naphthalene. This is seen to be due to the higher cellulose, hemicelluloses, lignin as well as higher chlorine content of the reed and woody fuels compared to the leached olive residue. The olive residue is seen to be better fuel for gasification compared with woody fuels and reed. Even more, we believe that the leached olive residue is better compared to all other tested fuel/mixtures in this study. It is seen that the proportions of different fuels in the mixture play role in the composition of the producer gas.

  • 17.
    Myrén, Carin
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Hörnell, Christina
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Björnbom, Emilia
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Catalytic tar decomposition of biomass pyrolysis gas with a combination of dolomite and silica2002In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 23, no 3, p. 217-227Article in journal (Refereed)
    Abstract [en]

    In this study the catalytic effects of dolomite and silica on biomass tar decomposition were investigated. The concentration of naphthalene is of particular interest since it is the most difficult compound to decompose when dolomite is used as catalyst. The two catalysts were tested in different combinations to see whether synergetic effects on the cracking of naphthalene could be found. Thermal and catalytic cracking were carried out at 700-900degreesC under ambient pressure in a fixed bed reactor using a tar-rich gas obtained from pyrolysis of different biomass materials. Characterisation of light components of tars using the solid phase adsorption method was also performed. Experimental results indicate that when a pure silica is placed in a layer above the dolomite, considerably less naphthalene and total light tar remains after cracking.

  • 18.
    Neeft, J.P.A
    et al.
    ECN The Netherlands.
    van Pasen, S.V.B.
    ECN The Netherlands.
    Knoef, Harri A.M
    BTG The Netherlands.
    Buffinga, G.J.
    BTG The Netherlands.
    Zielke, Uve
    DTI Denmark.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Brage, Claes
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Hassler, P.
    Verenum Switzerland.
    Suomalainen, M.
    VTT Finland.
    Dorrington, M.A.
    CRE Group UK.
    Thomas, L.
    CRE Group UK.
    Tar guideline. A standard method for measurement of tars and particles in biomass producer gases2002In: 12th Eurpoean Conference on Biomass for Energy, Industry and Climate Protection, 2002Conference paper (Refereed)
  • 19.
    Nemanova, Vera
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Brundu, M.
    Nordgreen, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Biomass gasification in an atmospheric fluidised bed: Probability to employ metallic iron as a tar reduction catalyst.2009In: 17th European Biomass Conference, 2009Conference paper (Refereed)
  • 20.
    Nemanova, Vera
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Nordgreen, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Biomass gasification in an atmospheric fluidised bed: Tar reduction with experimental iron-based granules from Höganäs AB, Sweden2011In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 176, no 1, p. 253-257Article in journal (Refereed)
    Abstract [en]

    The present study investigates the effect of several experimental iron-based granules on biomass tar decomposition. The iron-based materials were provided by Höganäs AB and were all in their metallic state when they were applied in a secondary catalytic reactor. Bark-free birch was employed as fuel in an atmospheric fluidised bed reactor, and the tar concentration and gas composition in the producer gas were measured before and after the catalytic bed. The results demonstrate a clear tar reduction capacity for all the tested iron-based materials.

  • 21.
    Nordgreen, Thomas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Elemental iron as a tar breakdown catalyst in conjunction with atmospheric fluidized bed gasification of biomass: A thermodynamic study2006In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 20, no 3, p. 890-895Article in journal (Refereed)
    Abstract [en]

    Metallic iron as a catalyst for tar cracking in biomass gasification has been investigated. Based on previous studies showing that iron must be in its elemental form to catalyze the tar breakdown reactions, thermodynamic calculations suggest the existence of an operating window where iron is neither oxidized nor contaminated by carbon deposits. A straightforward biomass gasification model has been derived and used in conjunction with thermodynamics for making plots that illustrate the mentioned operating window, which is achievable under real conditions. Experiments made under these specific calculated conditions confirm that elemental iron effectively acts as a tar breakdown catalyst, resulting in an improved gas yield and a decrease in tar concentration. The desired operating window is governed mainly by adjusting the oxygen input (i.e., the equivalence ratio) and the temperature.

  • 22.
    Nordgreen, Thomas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Metallic iron as a tar breakdown catalyst related to atmospheric, fluidised bed gasification of biomass2006In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 85, no 06-maj, p. 689-694Article in journal (Refereed)
    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.

  • 23.
    Nordgreen, Thomas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Nemanova, Vera
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Iron-based materials as tar depletion catalysts in biomass gasification: Dependency on oxygen potential2012In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 95, no 1, p. 71-78Article in journal (Refereed)
    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.

  • 24.
    Nordgreen, Thomas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Partial oxidation of methane in a biomass gasification gas2007In: Proceedings of the 15th EU BC&E - Berlin 2007, 2007Conference paper (Refereed)
  • 25. Romey, I.
    et al.
    Adorni, M.
    Wartmann, J.
    Herdin, G.
    Beran, R.
    Sjöström, Krister
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Rosén, Christer
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Concept for a Decentralised Combined Heat and Power Generation Unit for Biomass Gasification2001In: Progress in Thermochemical Biomass Conversion, Wiley-Blackwell, 2001, p. 499-508Chapter in book (Other academic)
    Abstract [en]

    The development of an improved process for decentralised combined heat and power generation from biomass gasification was the main goal of this project. Based on gasification tests performed in a bench-scale pressurised fluidised gasifier a concept for an allothermal gasification unit was made. Air-blown as well as steam-blown tests were carried out considering three different kinds of biomass (birch, salix, and crushed pelletised straw) against a wide spectrum of operation conditions with different bed-materials (silica sands, magnesite and dolomite). The aim of the gas quality optimisation was the production of a fuel gas (syngas) with a high H2 and low tar content suitable for a gas engine. The tar content was measured with SPA method and a gravimetric method. The tests were performed at the Royal Institute of Technology, Stockholm, in close co-operation with the University of Essen. Jenbacher AG designed a new type of cylinder head for the direct feeding of the hot pressurised syngas into the gas engine in co-operation with the Technical University of Graz. Taking the results obtained into account a concept of decentralised combined heat and power generation (CHP) unit with an electrical power output of 1 MW was set up.

  • 26. Simell, P.
    et al.
    Ståhlberg, P.
    Kurkela, E.
    Albrecht, J.
    Deutsch, S.
    Sjöström, Krister
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Provisional protocol for the sampling and anlaysis of tar and particulates in the gas from large-scale biomass gasifiers. Version 19982000In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 18, no 1, p. 19-38Article in journal (Refereed)
    Abstract [en]

    This paper presents tar sampling protocols for pressurised and atmospheric large scale gasification processes. Methods for constructing sampling lines either to on-line analysers or into sampling systems are described. The tar sampling system consists of a heated probe, a particulate filter and a series of impinger bottles. Dichloromethane is used as the tar absorbing solvent. The solvent containing bottles are placed in a cold bath so that gradual cooling of the sampled gas from about 0 degrees C to the final temperature -79 degrees C takes place in them. Recommendations for suitable sampling gas flow rates and gas temperatures are given. Tar characterisation methods based on different garvimetric measurements and GC analysis are described.

  • 27.
    Sjöstrom, Karin
    KTH, Superseded Departments, Pulp and Paper Technology.
    Influence of ionic strength on kraft cooking and subsequent TCF-bleaching1999In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 14, no 3, p. 226-235Article in journal (Refereed)
    Abstract [en]

    The TCF-bleachability of softwood kraft pulps produced with different ionic strength profiles has been investigated. In addition, the relationship between the bleaching response and some of the chemical structures in the pulp were studied. The ionic strength was changed by adding NaCl(s) at two alternative positions in the cook: after the pretreatment, or in the final part of the cook to give three different process variants. All cooks began with a standardized hydrogen sulfide ion pretreatment stage at low alkalinity. Pulps at two different kappa number levels, about 21 and 16, were investigated. After further delignification in an oxygen stage, the bleachability was studied with a QPQP*-sequence (Q=chelating agent stage, P=peroxide-stage, *=Mg ions addition). Pulping with a higher ionic strength led to a lower delignification cation rate and thus a greater hydroxide ion consumption to reach a given kappa number. The results also show an increasing light absorption coefficient/kappa number ratio for unbleached pulps with increasing ionic strength in the cook. The degree of delignification in the oxygen stage was higher with a higher ionic strength in the cook. The bleachability as well as the yield and the process selectivity were improved by a low ionic strength in the cook for all the three investigated process variants.

  • 28.
    Sjöstrom, Karin
    KTH, Superseded Departments, Pulp and Paper Technology.
    Kraft cooking with varying alkali concentration: Influence on TCF-bleachability1998In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 13, no 1, p. 57-63Article in journal (Refereed)
    Abstract [en]

    The TCF-bleachability of softwood pulps produced by kraft pulping processes with varying alkali concentrations was investigated. The cooks began with a hydrogen sulfide ion pretreatment at low alkalinity, i.e. simulating a black liquor preimpregnation. The alkalinity in the cooks was varied in three different ways: already at the beginning of the cook, both at 40 % sulfidity and at a HS- concentration of 0.3 mol/l (2-stage cooks), and in the final part of a modified kraft cook (4-stage cooks) simulating an ITC (Isothermal cooking) cook. The pulps had the same kappa number after the cook, about 17, and were oxygen delignified before bleaching. The influence of the alkali concentration profile in the cook on the bleachability was studied with a QPQP*-sequence (Q=chelating agent stage, P*=peroxide-stage with the addition of 0.05 % Mg ions). The bleachability (pulp brightness achieved for a given consumption of bleaching agent per kappa number) was found to reach a maximum for pulps with a residual alkali concentration in the vicinity of 0.5 mol/l. The bleachability was however affected to only a minor extent by the alkali concentration during the cook. The hexeneuronic acid content was found to decrease with increasing alkali concentration and this was taken into consideration when calculating the chemical consumption per amount of lignin. The process selectivity (pulp viscosity at a given brightness) decreased with increasing residual alkali. The bleachability was not improved by conducting the cook with a levelled out active cooking chemical profile, when the comparison was made at the same residual alkali concentration, but the selectivity was improved.

  • 29.
    Sjöstrom, Karin
    et al.
    KTH, Superseded Departments, Pulp and Paper Technology.
    Teder, Ants
    Changes in light absorption coefficient spectra as a result of TCF bleaching1999In: Paperi ja puu, ISSN 0031-1243, Vol. 81, no 2, p. 130-137Article in journal (Refereed)
    Abstract [en]

    Light absorption coefficient, k, spectra in the wavelength range from 200 to 700 nm have been determined for a number of modified kraft and alkaline sulfite pulps after O, OAZ and OAZQP* bleaching (O=oxygen, A=acid treatment, Z=ozone, Q=complexing agent, P*=peroxide stage with Mg addition). The different pulp types have earlier shown differences in bleachability and selectivity when bleached in an OAZQP* sequence and also in other sequences. However, the reason for the differences in bleachability are not fully understood. In this paper, the changes in k spectra after the different bleaching stages for the different pulp types are shown, and the differences are discussed, The accuracy in the determination of k is also discussed and why it is preferable to measure k rather than brightness. There were no significant differences between the shape of the k spectra for the different pulp types that could explain the known differences in bleachability between the pulp types. However, the levels of the k spectra after the oxygen stage could be correlated to the known differences in bleachability between the pulps, The k spectra for the ASAM pulp, the pulp that has shown best bleachability, was significantly lower compared to the other investigated pulps. Ozone and peroxide bleached pulps showed k spectra of approximately the same shape as the oxygen-delignified pulps. In this study, k values as high as about 10 m(2)/kg were correctly measured. At higher k values, the light scattering coefficient (s) began to deviate due to too high a light absorption. Dilution, i.e. mixing the pulp with a brighter pulp of lower and known k value so that the k value of the mixture does not exceed 10 m2/kg is a way of circumventing the problem. However, there are also some limitations with the pulp mixing method, which are discussed.

  • 30.
    Sjöstrom, Karin
    et al.
    KTH, Superseded Departments, Pulp and Paper Technology.
    Teder, Ants
    KTH, Superseded Departments, Pulp and Paper Technology.
    Changes within the modified kraft process aiming to improve TCF bleachability1999In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 25, no 5, p. 176-182Article in journal (Refereed)
    Abstract [en]

    the investigated process modifications were: presulphonation, postsulphonation, polysulphide pretreatment and polysulphide pretreatment combined with a postsulphonation. The influence of the degree of delignification in the cook, on the selectivity and bleachability, was also investigated. The pulps were produced from softwood chips and were oxygen delignified before bleaching according to an AZQP sequence. All the investigated process variants had better process selectivity (pulp viscosity at a given brightness) and the pulps produced with a postsulphonation showed better bleachability, than the reference pulp. The bleachability and the process selectivity was improved by interrupting the cook at a higher kappa number and instead extending the delignification in the oxygen stage.

  • 31.
    Sjöström, Karin
    KTH, Superseded Departments, Pulp and Paper Technology.
    Some aspects on TCF-bleachability of softwood alkaline pulps1999Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The bleachability of softwood oxygen delignified pulps has been studied, i.e. the ease (requirement of bleaching chemicals) with which the pulps can be brightened to a target brightness in totally chlorine free (TCF) bleaching stages, including hydrogen peroxide, ozone and chelating agent stages. Different cooking processes have been compared and the influence of different pre- and post-treatments on the kraft process has been investigated. The influence of different cooking parameters in the kraft cook on the bleachability has also been studied, as well as the influence on the bleachability of the kappa number of the pulp after the cook and after the oxygen stage.

    Pulps produced by alkaline sulfite processes, ASAM and MSSAQ, showed better bleachability and process selectivity(viscosity at a given brightness) than pulps produced by the modified kraft process. The bleachability of the modified kraftpulps could be improved by a post sulfonation.

    The bleachability was improved by terminating the cook at a higher kappa number level, when oxygen delignifying to the same kappa number level before bleaching. Improvements are also achieved by starting the oxygen stage from the same kappa number and extending the oxygen delignification to a lower kappa number level. The process selectivity and the yield are improved in the same way.

    The QPQP*-bleachability (P*=peroxide stage with the addition of magnesium ions) was improved by changing the cooking conditions in a kraft cook leading to a shorter cooking time, i.e. by increasing the hydroxide ion concentration, the hydrogen sulfide ion concentration, or the cooking temperature or by decreasing the sodium ion concentration. Exceptions could be seen for very high [HO-], where the bleachability even deteriorated, and when the temperature was increased at very high chemical charges, where no more improvement was achieved.

    The pulp with the best QPQP*-bleachability in a series of pulps had a lower light absorption coefficient (k)/lignin content (kappa number corrected for the hexenuronic acid contribution (kappa**)) ratio already after the cook as well as after the oxygen stage and a higherβ-O-4 content after the cook. A decreasedk/kappa** ratio after the cook is most probably due to less redeposition of dark dissolved organic material from the black liquor when the residual hydroxide ion concentration is increased. The degree of delignification in a subsequent oxygenstage becomes lower for the pulp with a lowerk/kappa** ratio after the cook and the metal ion content in the pulps was lower. Additives like, for example sulfite reduce the redeposition of lignin and lead to a brighter pulp.

    The changes leading to improved bleachability for a pulp are not always followed by improved yield and process selectivity. The hydrogen sulfide ion concentration and the sodium ion concentration influenced the yield and selectivity positively in the same way as the bleachability. Increased hydroxide ion concentration and temperature, however, lead to lower yield andpoorer selectivity. Thus for an optimal product a compromise between a good bleachability and high yield and good strength properties must be chosen.

     

  • 32.
    Sjöström, Krister
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Liliedahl, Truls
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Gasification of Biofuels2002Conference paper (Refereed)
  • 33. Svenson, J.
    et al.
    Pettersson, J. B. C.
    Omrane, Alaa
    KTH.
    Ossler, F.
    Aldén, M.
    Bellais, Michel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Surface temperature of wood particles during pyrolysis2006In: Science in thermal and chemical biomass conversion, CPL Press , 2006, p. 1174-Conference paper (Other academic)
  • 34.
    Teder, Ants
    et al.
    KTH, Superseded Departments, Pulp and Paper Technology.
    Sjöstrom, Karin
    KTH, Superseded Departments, Pulp and Paper Technology.
    A comparison of bleachability in TCF sequences for alkaline sulphite and kraft pulps1996In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 22, no 8, p. J296-J300Article in journal (Refereed)
    Abstract [en]

    The bleachability in different totally chlorine-free (TCF) bleaching sequences was investigated for two types of alkaline sulphite pulps, ASAM and MSSAQ, and compared with that of pulps produced by different new and industrially applied modified kraft pulping processes. The TCF sequences included oxygen, ozone, peroxide and complexing agent stages. The alkaline sulphite pulps were found to be easier to bleach in terms of the consumption of oxidative agents required to reach a given brightness than the pulps produced by the different modified kraft pulping processes. The relationship between pulp brightness and pulp viscosity was also much better for the sulphite pulps, although the new types of kraft pulps are gradually approaching the level of the alkaline sulphite pulps in this respect. There was no significant difference between the ASAM (alkaline sulphite anthraquinone methanol) and the two-stage MSSAQ (minisulphide sulphite anthraquinone) processes.

  • 35.
    Valero, David
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Liliedahl, Truls
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Tar cracking capability of iron in biomass gasification2002Conference paper (Refereed)
  • 36.
    Vriesman, Peter
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Heginuz, Eloise
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Biomass gasification in a laboratory-scale AFBG: influence of the location of the feeding point on the fuel-N conversion2000In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 79, no 11, p. 1371-1378Article in journal (Refereed)
    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.

  • 37.
    Yu, Q. Z.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Brage, Claes O.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Chen, G. X.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    The fate of fuel-nitrogen during gasification of biomass in a pressurised fluidised bed gasifier2007In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 86, no 4, p. 611-618Article in journal (Refereed)
    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.

  • 38.
    Yu, Q. Z.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Brage, Claes O.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Nordgreen, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Effects of Chinese dolomites on tar cracking in gasification of birch2009In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 88, no 10, p. 1922-1926Article in journal (Refereed)
    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.

  • 39.
    Zanzi, Rolando
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology. KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, Superseded Departments, Chemical Engineering and Technology. KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Björnbom, Emilia
    KTH, Superseded Departments, Chemical Engineering and Technology. KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Reaction Engineering.
    Rapid pyrolysis of agricultural residues at high temperature2002In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 23, no 5, p. 357-366Article in journal (Refereed)
    Abstract [en]

    This paper deals with rapid pyrolysis of agricultural residues such as olive waste and straw at high temperature (800 -1000degreesC) in a free-fall reactor at pilot scale. The conditions are of interest for gasification in fluidized beds where rapid pyrolysis plays an important role as first stage. The objective of the work is to study the effect of the process conditions such as heating rate, temperature and particle size on the product distribution, gas composition and char reactivity. A higher temperature and smaller particles increase the heating rate resulting in a decreased char yield. The cracking of the hydrocarbons with an increase in the hydrogen content is favoured by a higher temperature and by using smaller particles. Wood gives more volatiles and less char than straw and olive waste. The higher ash content in agricultural residues favours the charring reactions. The higher lignin content in olive waste results in a higher char yield in comparison with straw. Chars from olive waste and straw are more reactive in gasification than chars from birch because of the higher ash content.

  • 40. Zevenhoven-Onderwater, M.
    et al.
    Backman, R.
    Skrifvars, B. J.
    Hupa, M.
    Liliedahl, Truls
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Rosén, Christer
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Sjöström, Krister
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Engvall, Klas
    Hallgren, A.
    The ash chemistry in fluidised bed gasification of biomass fuels. Part II: Ash behaviour prediction versus bench scale agglomeration tests2001In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 80, no 10, p. 1503-1512Article in journal (Refereed)
    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.

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