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Träfflista för sökning "L773:2190 6823 OR L773:2190 6815 srt2:(2011-2014)"

Sökning: L773:2190 6823 OR L773:2190 6815 > (2011-2014)

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1.
  • Berguerand, Nicolas, 1978, et al. (författare)
  • Producer Gas Cleaning in a Dual Fluidized Bed - a Comparative Study of Performance with Ilmenite and a Manganese Oxide as Catalysts
  • 2012
  • Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 2:3, s. 8-252
  • Tidskriftsartikel (refereegranskat)abstract
    • Secondary catalytic gas conditioning is one strategy to eliminate tars formed in a producer gas during biomass gasification. However, most catalysts tend to lose their tar reforming activity after short period of operation due to carbon formation. A novel technique for catalytic gas cleaning based on two interconnected fluidized beds has been investigated; this technique can be applied to all types of gasifiers. The idea is to reform the tar components into useful molecules - even at high tar contents - by means of a circulating catalyst. More precisely, the producer gas is cleaned with catalyst in one of the reactors, referred to as the fuel reactor (FR), while the catalyst is continuously regenerated in another reactor, the air reactor (AR). The system described here is coupled with the Chalmers 2-4 MWth biomass gasifier while the AR is fed with nitrogen-diluted air. The effect of different catalysts on both the tar content and the gas composition was investigated. Some of the tested materials do not only reform tars, they also influence the H2/CO-ratio in a beneficial manner; in particular, ratios closer to 3 in the reformed gas are favorable if subsequent methanation is implemented. In this paper, comparative results based on testing with manganese- and iron-based catalysts are presented. The former is a manufactured catalyst while the latter is a natural ore. Results suggest that both show satisfying ability for regeneration from carbon deposits. Higher temperature enhances tar decomposition during experiment with both catalysts. Moreover, the iron-based catalyst enhances water gas shift activity, which in turns impacts the total amount of produced gas. On the other hand, the manganese-based catalyst seems to display higher propensity for tar conversion.
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3.
  • Heyne, Stefan, 1979, et al. (författare)
  • Exergy-based comparison of indirect and direct biomass gasification technologies within the framework of bio-SNG production
  • 2013
  • Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 3:4, s. 337-352
  • Tidskriftsartikel (refereegranskat)abstract
    • Atmospheric indirect steam-blown and pressurised direct oxygen-blown gasification are the two major technologies discussed for large-scale production of synthetic natural gas from biomass (bio-SNG) by thermochemical conversion. Published system studies of bio-SNG production concepts draw different conclusions about which gasification technology performs best. In this paper, an exergy-based comparison of the two gasification technologies is performed using a simplified gasification reactor model. This approach aims at comparing the two technologies on a common basis without possible bias due to model regression on specific reactor data. The system boundaries include the gasification and gas cleaning step to generate a product gas ready for subsequent synthesis. The major parameter investigated is the delivery pressure of the product gas. Other model parameters include the air-to-fuel ratio for gasification as well as the H2/CO ratio in the product gas. In order to illustrate the thermodynamic limits and sources of efficiency loss, an ideal modelling approach is contrasted with a model accounting for losses in, e.g. the heat recovery and compression operations. The resulting cold-gas efficiencies of the processes are in the range of 0.66–0.84 on a lower heating value basis. Exergy efficiencies for the ideal systems are from 0.79 to 0.84 and in the range of 0.7 to 0.79 for the systems including losses. Pressurised direct gasification benefits from higher delivery pressure of the finished gas product and results in the highest exergy efficiency values. Regarding bio-SNG synthesis however, a higher energetic and exergetic penalty for CO2 removal results in direct gasification exergy efficiency values that are below values for indirect gasification. No significant difference in performance between the technologies can be observed based on the model results, but a challenge identified for process design is efficient heat recovery and cogeneration of electricity for both technologies. Furthermore, direct gasification performance is penalised by incomplete carbon conversion in contrast to performance of indirect gasification concepts.
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4.
  • Lind, Fredrik, 1978, et al. (författare)
  • Manganese oxide as catalyst for tar cleaning of biomass-derived gas
  • 2012
  • Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 2:2, s. 133 - 140
  • Tidskriftsartikel (refereegranskat)abstract
    • The possibilities to upgrade raw gas with the use of a manganese oxide have been investigated in an application for secondary tar cleaning of biomass derived gas. Experiments were conducted in a reactor system where a novel technique that combines tar cleaning with catalyst regeneration is applied. Raw gas from the Chalmers non-catalytic steam biomass gasifier - containing roughly 32 gtar/Nm3gas - was fed to the tar cleaning reactor. The tar reforming qualities of the manganese oxide were evaluated in the reactor system using a mixture of 23 wt% catalysts in silica sand at the temperatures 700 and 800°C. Experiments showed that the catalyst was continuously regenerated from carbon deposits and that the total amount of tars was decreased by as much as 44,5% at a gas residence time of 0.4 s in the bed. The catalyst showed activity in water-gas shift reaction and the H2/CO-ratio increased from 0.6 in the raw gas to a peak value of 1 in the reformed gas at 800°C. Only a slight decrease in methane and acetylene content was observed for both operating temperatures.
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5.
  • Nilsson, Patrik, et al. (författare)
  • Laboratory evaluation of a gasifier particle sampling system using model compounds of different particle morphology
  • 2011
  • Ingår i: Biomass Conversion & Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 1:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The objective of this work was to design and evaluate an experimental setup to be used for field studies of particle formation in biomass gasification processes. The setup includes a high-temperature dilution probe and a denuder to separate solid particles from condensable volatile material. The efficiency of the setup to remove volatile material from the sampled stream and the influence from condensation on particles with different morphologies is presented. In order to study the sampling setup model, aerosols were created with a nebulizer to produce compact and solid KCl particles and a diffusion flame burner to produce agglomerated and irregular soot particles. The nebulizer and soot generator was followed by an evaporation–condensation section where volatile material, dioctylsebacete (DOS), was added to the system as a tar model compound. The model aerosol particles were heated to 200°C to create a system containing both solid particles and volatile organic material in gas phase. The heated aerosol particles were sampled and diluted at the same temperature with the dilution probe. Downstream the probe, the DOS was adsorbed in the denuder. This was achieved by slowly decreasing the temperature of the diluted sample towards ambient level in the denuder. Thereby the supersaturation of organic vapors was reduced which decreased the probability for tar condensation and nucleation of new particles. Both the generation system and the sampling technique gave reproducible results. A DOS collection efficiency of >99% was achieved if the denuder inlet concentration was diluted to less than 1–6 mg/m3 depending on the denuder flow rate. Concentrations higher than that lead to significant impact on the resulting KCl size distribution. The choice of model compounds was done to study the effect from the particle morphology on the achieved particle characteristics after the sampling setup. When similar amounts of volatile material condensed on soot agglomerates and compact particles, a substantially smaller growth in mobility diameter was found for soot compared with compact KCl.
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6.
  • Salomon, Marianne, et al. (författare)
  • Pelletization : an alternative for polygeneration in the palm oil industry
  • 2013
  • Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 3:3, s. 213-229
  • Tidskriftsartikel (refereegranskat)abstract
    • Agricultural residues continue to attract interest for energy recovery purposes as a renewable, CO2 neutral and increasingly cost-competitive alternative to traditional fossil fuels. Furthermore, some of these residues, like palm oil residues, represent a disposal problem for the processing industries, or they are not used efficiently. Several palm oil mills (POM) lack efficient energy systems and thus there is a considerable potential for improvement. These factors represent a strong driving force for the development of innovative polygeneration plants with combined electricity, heat and refined fuel production based on conversion of solid residues. This paper aims at analyzing the use of agro-industrial residues as fuel. For that, we propose different technology configurations based on the case of a small-scale palm oil mill in Colombia processing 30 tons of fresh fruit bunch per hour. The technology configurations include steam cycles using backpressure turbines, condensing-extraction turbines and also gasification-gas engine cycles in hybrid configurations. The possibilities to produce pellets from the residues from palm oil were also analyzed. The steam cycle base operational parameters were 20 bar and 350 °C. However, more advanced steam conditions (40 bar) were also considered and evaluated. All the analyses performed included a maximum of 60 % of the empty fruit bunch (EFB) produced in the POM for energy purposes due to its value as natural fertilizer in the palm oil plantations. The results show that the POM under study and other POMs that use electricity from the national grid have the capacity of being self-sufficient to cover of all their energy needs using the solid residues available. This means that POMs that currently only generate the required heat for the process can generate the electricity required and in some cases even an excess of energy that could be sold to other users with an adequate use of the residues available. Furthermore, based on the modeling done in Aspen Utilities Planner® it is shown that it is possible to cover the demand of the POM, the required energy demand for EFB preparation included possible pelletization of these residues and even generate an excess of electricity. In several of the configurations, excess electricity generation could be achieved in the range of 0.5–8 MW.
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7.
  • Tunå, Per, et al. (författare)
  • Regenerative reverse-flow reactor system for cracking of producer gas tars
  • 2014
  • Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 4:1, s. 43-51
  • Tidskriftsartikel (refereegranskat)abstract
    • The gas produced in a biomass gasifier contains high amounts of tars which have to be removed prior to downstream utilization. Calcined dolomite is catalytically active for tar cracking reactions and resistant to sulfur poisoning. In this study, calcined dolomite was used as bed material in a reverse-flow reactor for cracking of tars in a model synthesis gas. 1-methylnaphthalene was used as model tar compound at a concentration of 15,000 mg/Nm3. The reactor system was operated at temperatures between 700 and 850 °C in the active zone. Total tar conversion was over 95 % for the system under reverse-flow conditions at the highest temperature. Already at the lowest temperature, up to 78 % of the 1-methylnaphthlene was converted, but mainly to other more stable tar compounds such as naphthalene and benzene, reaching a total tar conversion of only 23 %. To produce tar-free gas, higher temperatures are thus needed. The use of very high temperatures does, however, lead to a significant decrease in the specific area of the dolomite, as shown by BET surface measurements. The dolomite was further characterized with x-ray diffraction and energy dispersive spectroscopy.
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8.
  • Wetterlund, Elisabeth, et al. (författare)
  • Optimal use of forest residues in Europe under different policies-second generation biofuels versus combined heat and power
  • 2013
  • Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 3:1, s. 3-16
  • Tidskriftsartikel (refereegranskat)abstract
    • The European Union has set a 10 % target for the share of renewable energy in the transportation sector for 2020. To reach this target, second generation biofuels from, for example, forest residues are expected to replace around 3 % of the transport fossil fuel consumption. However, forest residues could also be utilised in the heat and electricity sectors where large amounts of fossil fuels can be replaced, thus reducing global fossil CO2 emissions. This study investigates the use of forest residues for second generation biofuel (ethanol or methanol) or combined heat and power (CHP) production at the European level, with focus on the influence of different economic policy instruments, such as carbon cost or biofuel policy support. A techno-economic, geographically explicit optimisation model is used. The model determines the optimal locations of bioenergy conversion plants by minimising the cost of the entire supply chain. The results show that in order to reach a 3 % second generation biofuel share, a biofuel support comparable to today's tax exemptions would be needed. With a carbon cost applied, most available forest residues would be allocated to CHP production, with a substantial resulting CO2 emission reduction potential. The major potential for woody biomass and biofuel production is found in the region around the Baltic Sea, with Italy as one of the main biofuel importers.
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