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  • 1.
    Andersson, Jim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Landälv, Ingvar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Co-gasification of pyrolysis oil and black liquor for methanol production2015In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 158, p. 451-459Article in journal (Refereed)
    Abstract [en]

    One alternative to reduce the motor fuel production cost and improve the operational flexibility of a black liquor gasification (BLG) plant is to add pyrolysis oil to the black liquor feed and co-gasify the blend. The objective of this study was to investigate techno-economically the possibility to increase methanol production at a pulp mill via co-gasification of pyrolysis oil and black liquor. Gasifying a blend consisting of 50% pyrolysis oil and 50% black liquor on a wet mass basis increases the methanol production by more than 250%, compared to gasifying the available black liquor only. Co-gasification would add extra revenues per produced unit of methanol (IRR > 15%) compared to methanol from unblended BLG (IRR 13%) and be an attractive investment opportunity when the price for pyrolysis oil is less than 70 €/MW h. The economic evaluation was based on a first plant estimate with no investment credit for the recovery boiler and a methanol product value volumetric equivalent to conventional ethanol, both these conditions will not applicable when the technology has been fully commercialized.

  • 2.
    Bach Oller, Albert
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kirtania, Kawnish
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Co-gasification of black liquor and pyrolysis oil at high temperature: Part 1. Fate of alkali elements2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 202, p. 46-55Article in journal (Refereed)
    Abstract [en]

    The catalytic activity of alkali compounds in black liquor (BL) enables gasification at low temperatures with high carbon conversion and low tar and soot formation. The efficiency and flexibility of the BL gasification process may be improved by mixing BL with fuels with higher energy content such as pyrolysis oil (PO). The fate of alkali elements in blends of BL and PO was investigated, paying special attention to the amount of alkali remaining in the particles after experiments at high temperatures. Experiments were conducted in a drop tube furnace under different environments (5% and 0% vol. CO2 balanced with N2), varying temperature (800–1400 °C), particle size (90–200 µm, 500–630 µm) and blending ratio (0%, 20% and 40% of pyrolysis oil in black liquor). Thermodynamic analysis of the experimental cases was also performed.

    The thermodynamic results qualitatively agreed with experimental measurements but in absolute values equilibrium under predicted alkali release. Alkali release to the gas phase was more severe under inert conditions than in the presence of CO2, but also in 5% CO2 most of the alkali was found in the gas phase at T = 1200 °C and above. However, the concentration of alkali in the gasification residue remained above 30% wt. and was insensitive to temperature variations and the amount of PO in the blend. Thermodynamic analysis and experimental mass balances indicated that elemental alkali strongly interacted with the reactor’s walls (Al2O3) by forming alkali aluminates. The experience indicated that adding PO into BL does not lead to alkali depletion during high temperature gasification.

  • 3.
    Bach Oller, Albert
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kirtania, Kawnish
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Co-gasification of black liquor and pyrolysis oil at high temperature: Part 2. Fuel conversion2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 197, p. 240-247Article in journal (Refereed)
    Abstract [en]

    The efficiency and flexibility of the BL gasification process may improve by mixing BL with more energy-rich fuels such as pyrolysis oil (PO). To improve understanding of the fuel conversion process, blends of BL and PO were studied in an atmospheric drop tube furnace. Experiments were performed in varying atmosphere (5% and 0% CO2, balanced by N2), temperature (800–1400 °C), particle size (90–200 μm and 500–630 μm) and blending ratio (0%, 20% and 40% of PO in BL on weight basis). Additionally, pine wood was used as a reference fuel containing little alkali. The addition of PO to BL significantly increased the combined yield of CO and H2 and that of CH4. BL/based fuels showed much lower concentration of tar in syngas than pine wood. Remarkably, the addition of PO in BL further promoted tar reforming in presence of CO2. Unconverted carbon in the gasification residue decreased with increasing fractions of PO. Small fuel particles showed complete conversion at 1000 °C but larger particles did not reach complete conversion even at T = 1400 °C.

  • 4.
    Bjurström, Henrik
    et al.
    ÅF-Industry AB.
    Lind, B.B.
    Swedish Geotechnical Institute.
    Lagerkvist, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Unburned carbon in combustion residues from solid biofuels2014In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 117, no Part A, p. 890-899Article in journal (Refereed)
    Abstract [en]

    Unburned carbon (UC) in 21 combustion residues from solid biofuels has been examined using several methods of analysis (including LOI and TOC) as well as micro-Raman spectroscopy. The concentration of unburned carbon in the residues varied over an order of magnitude and in several samples accounted for about 10% of the ash mass. It was observed that TOC had a poor correlation to organic carbon, especially for fly ashes. LOI at all tested temperatures showed a better correlation than TOC to the organic carbon content, whereas the TOC is better correlated to elemental carbon. LOI550 gave a larger variation and a less complete mobilisation of unburned carbon than LOI at 750 or 975 °C did, but at the highest temperature metal oxidation was notably affecting the mass balance to the extent that some samples gained mass. For this reason, and of the temperatures tested, LOI750 seem to be the most stable indicator for organic remains in the incineration residuals. Most of the unburned carbon is elemental, and only slowly degradable, so the potential emissions of organic compounds from ashes should not be assessed by using a TOC test. The structure of the detected elemental carbon in UC is similar to that of activated carbon, which indicates a potentially large specific surface. This should be borne in mind when assessing the environmental impact of using ash for different purposes, including use as a construction material. Field studies are needed to verify the actual impact as it may depend on environmental conditions.

  • 5. Carlsson, Per
    et al.
    Wiinikka, Henrik
    Energy Technology Centre, Piteå.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Grönberg, Carola
    Energy Technology Centre, Piteå.
    Pettersson, Esbjörn
    Energy Technology Centre, Piteå.
    Lidman, Marcus
    Energy Technology Centre, Piteå.
    Gebart, Rikard
    Energy Technology Centre, Piteå.
    Experimental investigation of an industrial scale black liquor gasifier: 1. Influence of reactor operation parameters on product gas composition2010In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 89, no 12, p. 4025-4034Article in journal (Refereed)
    Abstract [en]

    A novel technology to mitigate the climate changes and improve energy security is Pressurized Entrained flow High Temperature Black Liquor Gasification (PEHT-BLG) in combination with an efficient fuel synthesis using the resulting syngas. In order to optimise the technology for use in a pulp and paper mill based biorefinery, it is of great importance to understand how the operational parameters of the gasifier affect the product gas composition. The present paper is based on experiments where gas samples were withdrawn from the hot part of a 3 MW entrained flow pressurized black liquor gasifier of semi industrial scale using a high temperature gas sampling system. Specifically, the influence of process conditions on product gas composition (CO2, CO, H2, CH4, H2S, and COS) were examined by systematically varying the operational parameters: system pressure, oxygen to black liquor equivalence ratio, black liquor flow rate to pressure ratio and black liquor pre-heat temperature. Due to the harsh environment inside the gasification reactor, gas sampling is a challenging task. However, for the purpose of the current study, a specially designed high temperature gas sampling system was successfully developed and used. The results, obtained from two separate experimental campaigns, show that all of the investigated operational parameters have a significant influence on the product gas composition and present valuable information about to the process characteristics.

  • 6.
    Chelgani, Saeed Chehreh
    et al.
    University of Michigan, Ann Arbor, USA.
    Hower, J. C.
    University of Kentucky, Lexington, USA.
    Relationships between noble metals as potential coal combustion products and conventional coal properties2018In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 226, p. 345-349Article in journal (Refereed)
    Abstract [en]

    Increasing coal consumption has generated million tons of ash and caused various environmental issues. Exploring statistical relationships between concentrations of valuable metals in coal and other coal properties may have several benefits for their commercial extraction as byproducts. This investigation studied relationships between conventional coal concentrations and concentration of noble metals for a wide range (708 samples) of eastern Kentucky coal samples (EKCS) by statistical methods. The results indicate that there are significant positive Pearson correlations (r) > 0.90 among all noble metals (Au, Pt, Pd, Ru and Rh) except for Ag (r < 0.2). The results also showed that the noble metals (except Ag) are associated with the minerals of the coal and have high positive correlations with ash (and high negative correlations with the organic fraction). Modeling through the database demonstrated that the highest Au concentrations in the EKCS occur when Si is between 6000 and 8000 ppm and Fe is below 10000 ppm, and the highest Ag was observed when both Cu and Ni were over 40 ppm. Outcomes suggested that aluminosilicate minerals and pyrite are possibly the main host of noble metals (except Ag) in the EKCS whereas Ag might occur in various forms including organic association, mineral species, and as a native metal.

  • 7.
    Chelgani, Saeed Chehreh
    et al.
    University of Michigan, Ann Arbor, Michigan, USA.
    Matin, S. S.
    Islamic Azad University, Tehran, Iran.
    Hower, James C.
    University of Kentucky, Lexington, Kentucky, USA.
    Explaining relationships between coke quality index and coal properties by Random Forest method2016In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 182, p. 754-760Article in journal (Refereed)
    Abstract [en]

    In this study was shown that random forest (RF) can be used as a sensible new data mining tool for variable importance measurements (VIMs) through various coal properties for prediction of coke quality (Free Swelling Index (FSI)). The VIMs of RF within coal analyses (proximate, ultimate, and petrographic analyses) were applied for the selection of the best predictors of FSI over a wide range of Kentucky coal samples. VIMs assisted by Pearson correlation through proximate, ultimate, and petrographic analyses indicated that volatile matter, carbon, vitrinite, and Rmax (coal rank parameters) are the most effective variables for the prediction of FSI. These important predictors have been used as inputs of RF model for the FSI prediction. Outputs in the testing stage of the model indicated that RF can predict FSI quite satisfactorily; the R2 was 0.93 and mean square error from actual FSIs was 0.15 (had less than interval unit of FSI; 0.5). According to the result, by providing nonlinear inter-dependence approximation among parameters for variable selection and also non-parametric predictive model RF can potentially be further employed as a reliable and accurate technique for the determination of complex relationship through fuel and energy investigations.

  • 8. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Non-coking coal preparation by novel tribo-electrostatic method2008In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 87, no 17-18, p. 3562-3571Article in journal (Refereed)
    Abstract [en]

    A new laboratory fluidised bed tribo-electrostatic separator has been assembled and the beneficiation potential of thermal non-coking coal from Hingula block of Talcher coal field, India, is examined on this separator. The uniqueness of the separator originates from the efficient tribo-electrification of coal material in the cylindrical fluidised bed with internal baffle system. The collecting bins of the material underneath the copper plate electrodes are designed to function as Faraday cups such that the charge polarity and magnitude of particles in each bin can be measured directly. The liberation attributes of coal material is assessed by sink and float analysis of various size fractions. The mineral and maceral composition is determined by XRD and petrographic analysis. The separation tests were conducted at different tribo-charging and applied voltage conditions. The material collected in bins close to positive and negative electrodes show an ash content of 61% and 8% respectively, illustrating differential charge acquisition of mineral rich and coal rich particles during tribo-electrification. The charge results are in good agreement with the ash content of the coal material collected in the bins. The results showed that a clean coal of about 15% ash can be obtained from a coal containing 30% ash with about 70% yield. A better separation results can be achieved by recycling the material. The ash content in the clean coal is however limited by the liberation characteristics of the coal, which is evidenced by the SEM analysis of the particles in different bins. Thus, the tribo-electrostatic method observed to be a promising dry coal preparation technique.

  • 9.
    Eriksson, Gunnar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Grimm, Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Umeå universitet.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Combustion and fuel characterisation of wheat distillers dried grain with solubles (DDGS) and possible combustion applications2012In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 102, p. 208-220Article in journal (Refereed)
    Abstract [en]

    The present transition to a sustainable global energy system requires that biomass is increasingly combusted for heat and power production. Agricultural fuels considered include alkali-rich fuels with high phosphorus content. One such fuel is wheat distiller’s dried grain with solubles (wheat DDGS) from wheat-based ethanol production. Further increases in ethanol production may saturate the current market for wheat DDGS as livestock feed, and fuel uses are therefore considered. Fuel properties of wheat DDGS have been determined. The ash content (5.4. ± 1.6 %wt d.s.) is similar to many agricultural fuels. In comparison to most other biomass fuels the sulphur content is high (0.538 ± 0.232 %wt d.s.), and so are the contents of nitrogen (5.1 ± 0.6 %wt d.s.), phosphorus (0.960. ± 0.073 %wt d.s.) and potassium (1.30 ± 0.35 %wt d.s.). To determine fuel-specific combustion properties, wheat DDGS and mixes between wheat DDGS and logging residues (LR 60 %wt d.s. and DDGS 40 %wt d.s.), and wheat straw (wheat straw 50 %wt d.s., DDGS 50 %wt d.s.) were pelletized and combusted in a bubbling fluidised bed combustor (5 kW) and in a pellets burner combustor (20 kW). Pure wheat DDGS powder was also combusted in a powder burner (150 kW). Wheat DDGS had a high bed agglomeration and slagging tendency compared to other biomass fuels, although these tendencies were significantly lower for the mixture with the Ca-rich LR, probably reflecting the higher first (solid) melting temperatures of K–Ca–Mg-phosphates compared to K-phosphates. Combustion and co-combustion of wheat DDGS resulted in relatively large emissions of fine particles (<1 μm) for all combustion appliances. For powder combustion PMtot was sixteen times higher than from softwood stem wood. While the Cl concentrations of the fine particles from the LR–wheat DDGS-mixture in fluidised bed combustion were lower than from combustion of pure LR, the Cl- and P-concentrations were considerably higher from the wheat DDGS mixtures combusted in the other appliances at higher fuel particle temperature. The particles from powder combustion of wheat DDGS contained mainly K, P, Cl, Na and S, and as KPO3 (i.e. the main phase identified with XRD) is known to have a low melting temperature, this suggests that powder combustion of wheat DDGS should be used with caution. The high slagging and bed agglomeration tendency of wheat DDGS, and the high emissions of fine particles rich in K, P and Cl from combustion at high temperature, mean that it is best used mixed with other fuels, preferably with high Ca and Mg contents, and in equipment where fuel particle temperatures during combustion are moderate, i.e. fluidised beds and possibly grate combustors rather than powder combustors.

  • 10. Eriksson, Gunnar
    et al.
    Kjellström, Björn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundqvist, Björn
    Paulrud, S.
    SLU, Umeå.
    Combustion of wood hydrolysis residue in a 150 kW powder burner2004In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 83, no 11-12, p. 1635-1641Article in journal (Refereed)
    Abstract [en]

    A combustion test has been made with residues from hydrolysis of wood for fuel ethanol production. A 150 kW powder burner was used. Fuel feeding and combustion were stable. The average concentration of CO in the stack gas was 8 mg/MJ, the average concentration of NOx was 59 mg/MJ and the average total hydrocarbon concentration was below 1 ppm, at an average O2-concentration of 4.6%. The low contents of potassium and sodium in the hydrolysis residue make the material attractive as a gas turbine fuel and the conclusion of this test is that direct combustion may be a feasible approach for gas turbine applications.

  • 11.
    Erlich, Catharina
    et al.
    Kungliga tekniska högskolan, KTH.
    Öhman, Marcus
    Björnbom, Emilia
    Kungliga tekniska högskolan, KTH.
    Fransson, Torsten H.
    Umeå university.
    Thermochemical characteristics of sugar cane bagasse pellets2005In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 84, no 5, p. 569-575Article in journal (Refereed)
    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°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.

  • 12.
    Göktepe, Burak
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hazim, Ammar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Soot reduction in an entrained flow gasifier of biomass by active dispersion of fuel particles2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 201, p. 111-117Article in journal (Refereed)
    Abstract [en]

    Soot is an undesired by-product of entrained flow biomass gasification since it has a detrimental effect on operation of the gasifier, e.g. clogging of flow passages and system components and reduction of efficiency. This study investigated how active flow manipulation by adding synthetic jet (i.e. oscillating flow through orifice) in feeding line affects dispersion of fuel particles and soot formation. Pine sawdust was gasified at the conditions similar to pulverized burner flame, where a flat flame of methane-air sub-stoichiometric mixture supported ignition of fuel particles. A synthetic jet flow was supplied by an actuator assembly and was directed perpendicular to a vertical tube leading to the center of the flat flame burner through which pine sawdust with a size range of 63–112 μm were fed into a reactor. Quartz filter sampling and the laser extinction methods were employed to measure total soot yield and soot volume fraction, respectively. The synthetic jet actuator modulated the dispersion of the pine sawdust and broke up particle aggregates in both hot and cold gas flows through generation of large scale vortex structures in the flow. The soot yield significantly reduced from 1.52 wt.% to 0.3 wt.% when synthetic jet actuator was applied. The results indicated that the current method suppressed inception of young soot particles. The method has high potential because soot can be reduced without changing major operation parameters.

  • 13.
    Holmgren, Per
    et al.
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Wagner, David R.
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Strandberg, Anna
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Molinder, Roger
    RISE Energy Technology Center.
    Wiinikka, Henrik
    RISE Energy Technology Center.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Broström, Markus
    Thermochemical Energy Conversion Laboratory (TEC-Lab), Department of Applied Physics and Electronics, Umeå University.
    Size, shape, and density changes of biomass particles during rapid devolatilization2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 206, p. 342-351Article in journal (Refereed)
    Abstract [en]

    Particle properties such as size, shape and density play significant roles on particle flow and flame propagation in pulverized fuel combustion and gasification. A drop tube furnace allows for experiments at high heating rates similar to those found in large-scale appliances, and was used in this study to carry out experiments on pulverized biomass devolatilization, i.e. detailing the first stage of fuel conversion. The objective of this study was to develop a particle conversion model based on optical information on particle size and shape transformation. Pine stem wood and wheat straw were milled and sieved to three narrow size ranges, rapidly heated in a drop tube setup, and solid residues were characterized using optical methods. Different shape descriptors were evaluated and a shape descriptor based on particle perimeter was found to give significant information for accurate estimation of particle volume. The optical conversion model developed was proven useful and showed good agreement with conversion measured using a reference method based on chemical analysis of non-volatilized ash forming elements. The particle conversion model presented can be implemented as a non-intrusive method for in-situ monitoring of particle conversion, provided density data has been calibrated

  • 14.
    Kramb, Jason
    et al.
    Department of Chemistry, Renewable Energy Programme, University of Jyväskylä.
    Konttinen, Jukka
    Department of Chemistry, Renewable Energy Programme, University of Jyväskylä.
    Gómez-Barea, Alberto
    Bioenergy Group, Chemical and Environmental Engineering Department, Escuela Superior de Ingenieros, University of Seville.
    Moilanen, Antero
    VTT Technical Research Centre of Finland, Espoo.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Modeling biomass char gasification kinetics for improving prediction of carbon conversion in a fluidized bed gasifier2014In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 132, p. 107-115Article in journal (Refereed)
    Abstract [en]

    Gasification of biomass in a fluidized bed (FB) was modeled based on kinetic data obtained from previously conducted thermogravimetric analysis. The thermogravimetric analysis experiments were designed to closely resemble conditions in a real FB gasifier by using high sample heating rates, in situ devolatilization and gas atmospheres of H2O/H2 and CO2/CO mixtures. Several char kinetic models were evaluated based on their ability to predict char conversion based on the thermogravimetric data. A modified version of the random pore model was shown to provide good fitting of the char reactivity and suitability for use in a reactor model. An updated FB reactor model which incorporates the newly developed char kinetic expression and a submodel for the estimation of char residence time is presented and results from simulations were compared against pilot scale gasification data of pine sawdust. The reactor model showed good ability for predicting char conversion and product gas composition.

  • 15.
    Marklund, Magnus
    et al.
    Energy Technology Centre, Piteå.
    Tegman, Ragnar
    Chemrec AB, c/o ETC, Piteå.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    CFD modelling of black liquor gasification: identification of important model parameters2007In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 86, no 12-13, p. 1918-1926Article in journal (Refereed)
    Abstract [en]

    Pressurized high temperature black liquor gasification has the potential to significantly improve the efficiency of energy and chemical recovery in the pulping industry and to enable new processes, e.g. production of renewable automotive fuels from the formed synthesis gas. However, the current process is still considered as novel and the interest in validated computer models for scale-up and process optimisation is large. In this paper a sensitivity analysis on the four most important model parameters in the pre-processing ‘droplet composition model' for a proposed CFD model has been performed. It was shown that careful measurements of the amount of sulphur released to the gas phase as H2S during devolatilization and the concentration ratio of Na2S and Na2SO4 in the black liquor char under real process conditions are of great importance for calibration of the model.

  • 16.
    Matin, S. S.
    et al.
    Islamic Azad University, Tehran, Iran.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    Estimation of coal gross calorific value based on various analyses by random forest method2016In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 177, p. 274-278Article in journal (Refereed)
    Abstract [en]

    The last decade has witnessed of increasing the application of random forest (RF) models that are known as an exhibit good practical performance, especially in high-dimensional settings. However, on the theoretical side, their predictive ability markedly remains unexplained, especially in coal preparation. RF as a predictive model can tend to work well with large dimensional databases and rank predictors through its inbuilt variable importance measures. In this study, relationships among ultimate and proximate analyses of 6339 US coal samples from 26 states with gross calorific value (GCV) have been investigated by multivariable regression (MVR) and random forest (RF) models. RF method has been used for the variable importance. Models have shown that the ultimate analysis parameters are the most suitable estimators for GCV and that RF can predict GCV quite satisfactory. Running of the best arranged RF structures for the input sets and assessment of errors have suggested that RF models are suitable for complicated relationships.

  • 17.
    Nordin, Anders
    et al.
    Umeå university.
    Eriksson, Lennart
    Umeå universitet.
    Öhman, Marcus
    NO reduction in a fluidized bed combustor with primary measures and selective non-catalytic reduction a screening study using statistical experimental designs1995In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 74, no 1, p. 128-135Article in journal (Refereed)
    Abstract [en]

    Screening experiments were carried out to study the reduction of NO emissions from a 20 MW circulating fluidized bed (CFB) boiler, equipped with an installation for selective non-catalytic reduction (SNR). The influence of both primary measures and SNR were evaluated, using 25-1 and 25-2 fractional factorial designs for the two fuels, crushed peat and wood waste, respectively. Polynomial models were deducted from statistical analysis of the experiments, and a good agreement between models and measured data was obtained. The evaluation showed that, by using a designed experimental procedure, CFB operating conditions yielding an NO reduction of 60-80% could be identified, with both primary measures and the SNR being of approximately equal importance. Most important factors for the NO reduction were air:fuel ratio, the amount of NH3 added, the load and the fraction of lower secondary air; but the reduction is also influenced by small interaction effects. A discussion of the use of experimental designs for increased understanding and optimization of combustion processes is also given.

  • 18.
    Paulrud, Susanne
    et al.
    Swedish University of Agricultural Sciences.
    Nilsson, Calle
    Swedish University of Agricultural Sciences.
    Öhman, Marcus
    Reed canary-grass ash composition and its melting behaviour during combustion2001In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 80, no 10, p. 1391-1398Article in journal (Refereed)
    Abstract [en]

    Spring harvested reed canary-grass (RCG) with various chemical compositions was combusted in a 180 kW boiler. The ash melting behaviour was studied and the ash was analysed. Estimation of melting behaviour was done by ASTM fusion test, a bench-scale fluidized-bed combustion test (5 kW), and by extracting melting behaviours from the ternary phase diagram SiO2-CaO-K2O. The initial melting temperatures seem to be similar for the different samples; however, for low ash content (3-4% DM) higher portions of melt occurred in the lower temperature range <1200°C and for high ash content fuels (5-10%) more melting occurred in a higher temperature range, >1500°C.

  • 19.
    Risberg, Mikael
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Öhrman, Olov
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Nilsson, Patrik
    Gudmundsson, Anders
    Sanati, Mehri
    Influence from fuel type on the performance of an air-blown cyclone gasifier2014In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 116, p. 751-759Article in journal (Refereed)
    Abstract [en]

    Entrained flow gasification of biomass using the cyclone principle has been proposed in combination with a gas engine as a method for combined heat and power production in small to medium scale (<20 MW). This type of gasifier also has the potential to operate using ash rich fuels since the reactor temperature is lower than the ash melting temperature and the ash can be separated after being collected at the bottom of the cyclone. The purpose of this work was to assess the fuel flexibility of cyclone gasification by performing tests with five different types of fuels; torrefied spruce, peat, rice husk, bark and wood. All of the fuels were dried to below 15% moisture content and milled to a powder with a maximum particle size of around 1 mm. The experiments were carried out in a 500 kWth pilot gasifier with a 3-step gas cleaning process consisting of a multi-cyclone for removal of coarse particles, a bio-scrubber for tar removal and a wet electrostatic precipitator for removal of fine particles and droplets from the oil scrubber (aerosols). The lower heating value (LHV) of the clean producer gas was 4.09, 4.54, 4.84 and 4.57 MJ/N m3 for peat, rice husk, bark and wood, respectively, at a fuel load of 400 kW and an equivalence ratio of 0.27. Torrefied fuel was gasified at an equivalence ratio of 0.2 which resulted in a LHV of 5.75 MJ/N m3 which can be compared to 5.50 MJ/N m3 for wood powder that was gasified at the same equivalence ratio. A particle sampling system was designed in order to collect ultrafine particles upstream and downstream the gasifier cleaning device. The results revealed that the gas cleaning successfully removed >99.9% of the particulate matter smaller than 1 μm.

  • 20.
    Sayan, S.
    et al.
    Bilkent University, Ankara.
    Demirel, B.
    University of Utah.
    Paul, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Methyldecalin hydrocracking over palladium/zeolite-X2000In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 79, no 11, p. 1395-1404Article in journal (Refereed)
    Abstract [en]

    Hydrocracking of methyldecalin over Pd/REX has been studied with surface sensitive techniques in the critical temperature range 325-350°C. Results from in situ characterization of adsorbed species, and post-reaction analysis of the catalyst surface by infrared and photoemission spectroscopies, were related to product distributions. The results are discussed in light of quantum chemical calculations of free and catalyst bound intermediates, following ring-opening reactions. Liquid and gaseous products were detected by infrared and UV/Vis spectroscopies. Apparent activation energies of product formation hydrogen consumption, over a broader temperature range, were derived from previous autoclave experiments. An increase in temperature, 325-350°C, results in a shift from preferred cracking products to aromatics, an enhanced level of light hydrocarbon off-gases, and a higher coverage of carbonaceous residues. The increased level of carbonaceous residues is accompanied by a lowered coverage of the reactant, at the surface. The altered product distribution can be characterized by apparent single activation energies, valid from 300 to 450°C. Methane and aromatics show a similar rapid increase with temperature, hydrogen consumption a more timid increase, indicating a reaction limited by diffusion, and cycloalkane production a modest inverse temperature dependence. Fully hydrogenated ring-opening products represent valuable fuel components, but hydrogen deficiency can instead lead to chemisorbed precursors to coke. Our calculations show that cyclohexane, 1,2-diethyl, 3-methyl has a lower heat of formation than the corresponding surface intermediates, but a small enthalpy advantage can easily be countered by entropy effects at higher temperatures. This balance is critical to the formation of preferred products, instead of catalyst deactivation and aromatics. The theoretical results further show that surface intermediates, where the terminating hydrogen is replaced by a C-O bond, have distinct vibrations around 1150 cm-1.

  • 21.
    Sedlmayer, Irene
    et al.
    BIOENERGY 2020+ GmbH.
    Arshadi, Mehrdad
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Haslinger, Walter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. BIOENERGY 2020+.
    Hofbauer, Hermann
    Technische Universität Wien, Environmental and Bioscience Engineering.
    Larsson, Ida
    RISE Research Institutes of Sweden, Safety, Fire Research.
    Lönnermark, Anders
    RISE Research Institutes of Sweden, Safety, Fire Research.
    Nilsson, Calle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Pollex, Annett
    DBFZ Deutsches Biomasseforschungszentrum gemeinnützige GmbH.
    Schmidl, Christoph
    BIOENERGY 2020+ GmbH.
    Stelte, Wolfgang
    Technical University of Denmark, Center for Bachelor of Engineering Studies.
    Wopienka, Elisabeth
    BIOENERGY 2020+ GmbH.
    Bauer-Emhofer, Waltraud
    BIOENERGY 2020+ GmbH.
    Determination of off-gassing and self-heating potential of wood pellets: Method comparison and correlation analysis2018In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 234, p. 894-903Article in journal (Refereed)
    Abstract [en]

    Several methods for identifying the phenomena of self-heating and off-gassing during production, transportation and storage of wood pellets have been developed in recent years. Research focused on the exploration of the underlying mechanisms, influencing factors or the quantification of self-heating or off-gassing tendencies. The present study aims at identifying a clear correlation between self-heating and off-gassing. Thus, different methods for determining self-heating and off-gassing potentials of wood pellets are compared. Therefore, eleven wood pellet batches from the European market were analyzed. For this investigation, three methods for the determination of self-heating, like isothermal calorimetry, oxi-press and thermogravimetric analysis, and four methods for off-gassing, like volatile organic compound (VOC) emissions measurements, gas phase analysis of stored pellets in a closed container by offline and by glass flask method and determination of fatty and resin acids content, were performed. Results were ranked according to the self-heating and off-gassing tendency providing a common overview of the analyzed pellets batches. Relations between different methods were investigated by Spearman’s correlation coefficient. Evaluation of the results revealed an equal suitability of offline and glass flask methods to predict off-gassing tendency and indicated a very significant correlation with isothermal calorimetry for the identification of self-heating tendency. The thermogravimetric analysis as well as the fatty and resin acids determination proved to be insufficient for the exclusive assessment of self-heating and off-gassing tendency, respectively.

  • 22.
    Seferinoglu, Meryem
    et al.
    MTA, Mineral Research and Exploration Directorate, 06520 Balgat, Ankara.
    Paul, Mehtap
    Luleå tekniska universitet.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Köker, Agah
    MTA, Mineral Research and Exploration Directorate, 06520 Balgat, Ankara.
    Toprak, Selami
    MTA, Mineral Research and Exploration Directorate, 06520 Balgat, Ankara.
    Paul, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Acid leaching of coal and coal-ashes2003In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 82, no 4, p. 1721-1734Article in journal (Refereed)
    Abstract [en]

    Twelve Turkish lignites and the corresponding ashes were leached in sulfuric acid (pH 1.0, 25 oC) for 14 days. Asphaltite from Silopi amended the coals. The conditions mimic treatment in the effluent from bioleaching of sulfidic mineral concentrates, but the results are equally valid for an isolated leaching process. The extended time meant that we approached equilibrium and maximum extraction.The coals have limited neutralizing capacity. H2SO4 (1.0-2.0 l, 1 M) was needed to stabilize 1 kg coal at pH 1.0 (liquid:solid ratio 10:1), but the coal-ashes required 18.0-24.0 l/kg dry solid, which is the neutralizing equivalent to CaO.Leaching of dominant inorganic phases consume acid, but our interest is merely to remove trace elements present as dopants. We removed large fractions of Mg and Mn, but Al, K and Na extractions were limited by the presence of stable minerals and bimetallic oxides. The formation of the latter is driven by combustion at high temperatures. Alumina, normally not stable at pH 1.0, was protected from the effluent by the organic phase in coal. Fe leaching varied and appeared to be a marker for different chemical occurrences in the solids.Cd, V, Zn, U and Th were leached to near 80% from the ashes, but considerably less from the coals. Co and Ni extractions were near 60%, but not always higher from the ashes compared with the coals. Cu yields increase following ashing and reached ca. 60%. Ti, Ba, and Cs were not leached.We suggest that direct acid leaching is of interest to limit the deleterious impact of ash deposits and to recirculate metals from the ash. Ash may partly replace limestone in hydrometallurgical processing, but, more importantly, metal ions extracted from ash may be fed into the metal recovery stages of such processes. It is particularly interesting to leach Co, Cu, Ni and Zn, besides Mn, V and the environmentally hazardous Cd, U and Th. Leaching of whole coals is well motivated for domestic use-lump sizes around 18-50 mm, or slightly smaller, 10 mm, if mandated by practical residence times-where generally no other measures are taken to protect the local environment.

  • 23.
    Sefidari, Hamid
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Razmjoo, Narges
    Strand, Michael
    An experimental study of combustion and emissions of two types of woody biomass in a 12-MW reciprocating-grate boiler2014In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 135, p. 120-129Article in journal (Refereed)
  • 24.
    Trubetskaya, Anna
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Beckmann, Gert
    Retsch Technology GmbH.
    Wadenbäck, Johan
    Amager power plant, HOFOR A/S.
    Holm, Jens Kai
    DONG Energy Thermal Power A/S.
    Velaga, Sitaram
    Luleå University of Technology, Department of Health Sciences, Medical Science.
    Weber, Roman
    Institute of Energy Processes Engineering and Fuel Technology, Clausthal University of Technology.
    One way of representing the size and shape of biomass particles in combustion modeling2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 206, p. 675-683Article, book review (Refereed)
    Abstract [en]

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

  • 25.
    Trubetskaya, Anna
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. hermochemical Energy Conversion Laboratory, Umeå University.
    Hofmann Larsen, Flemming
    Department of Food Science, University of Copenhagen.
    Shchukarev, Andrey
    Department of Chemistry, Umeå University.
    Ståhl, Kenny
    Department of Chemistry, Technical University of Denmark.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Potassium and soot interaction in fast biomass pyrolysis at high temperatures2018In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 225, p. 89-94Article in journal (Refereed)
    Abstract [en]

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

  • 26.
    Tóth, Pál
    et al.
    RISE Bioekonomi/RISE Energy Technology Center AB, Piteå. Institute of Thermal Energy, University of Miskolc, Miskolc, Hungary.
    Ögren, Yngve
    RISE Bioekonomi/RISE Energy Technology Center AB, Piteå, Sweden.
    Sepma, Alexey
    RISE Bioekonomi/RISE Energy Technology Center AB, Piteå, Sweden.
    Vikström, Therese
    RISE Bioekonomi/RISE Energy Technology Center AB, Piteå, Sweden.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Wiinikka, Henrik
    RISE Bioekonomi/RISE Energy Technology Center AB, Piteå, Sweden.
    Spray combustion of biomass fast pyrolysis oil: Experiments and modeling2019In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 237, p. 580-591Article in journal (Refereed)
    Abstract [en]

    In this work, we are the first to report a detailed comparison between the predictions of a current Computational Fluid Dynamics (CFD) model for describing Fast Pyrolysis Oil (FPO) spray combustion and results from a laboratory-scale experiment. The objectives were to assess the predictive power of the CFD model, evaluate its usefulness in a numerical optimization scenario and characterize the spray flame. The spray flame was produced by using an air-assist atomizer piloted by a CH4" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; line-height: normal; font-size: 14.4px; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">CH4/air flat-flame. Pyrolysis oil from a cyclone fast pyrolysis plant was combusted. The flame was characterized by using two-color pyrometry, Tunable Diode Laser Absorption Spectroscopy and high-magnification shadowgraphy. Overall, the assessed model correctly predicted flame structure and seemed appropriate for engineering applications, but lacked predictive power in estimating droplet size distributions. Numerical results were the most sensitive to variations in the initial droplet size distribution; however, seemed robust to changes in the multicomponent fuel formulation. Several conclusions were drawn regarding FPO spray combustion itself; e.g., the amount of produced soot in the flames was very low and droplets exhibited microexplosion behavior in a characteristic size-shape regime.

  • 27.
    Weiland, Fredrik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wiinikka, Henrik
    Hedman, Henry
    Energy Technology Centre, Piteå, SP Energy Technology Center AB.
    Wennebro, Jonas
    SP Energy Technology Center AB.
    Pettersson, Esbjörn
    LTU/ETC, Energy Technology Centre, Piteå, SP Energy Technology Center AB.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Influence of process parameters on the performance of an oxygen blown entrained flow biomass gasifier2015In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 153, p. 510-519Article in journal (Refereed)
    Abstract [en]

    Pressurized, O2 blown, entrained flow gasification of pulverized forest residues followed by methanol production is an interesting option for synthetic fuels that has been particularly investigated in the Nordic countries. In order to optimize gasification plant efficiency, it is important to understand the influence of different operating conditions. In this work, a pressurized O2 blown and entrained flow biomass gasification pilot plant was used to study the effect of four important process variables; (i) the O2 stoichiometric ratio (λ), (ii) the load of the gasifier, (iii) the gasifier pressure, and (iv) the fuel particle size. Commercially available stem wood fuels were used and the process was characterized with respect to the resulting process temperature, the syngas yield, the fuel conversion and the gasification process efficiency. It was found that CH4 constituted a significant fraction of the syngas heating value at process temperatures below 1400 °C. If the syngas is intended for catalytic upgrading to a synthetic motor fuel where CO and H2 are the only important syngas species, the process should be optimized aiming for a process temperature slightly above 1400 °C in order to reduce the energetic losses to CH4 and C6H6. This resulted in a cold gas efficiency (based only on CO and H2) of 70%. The H2/CO ratio was experimentally determined within the range 0.45–0.61. Thus, the syngas requires shifting in order to increase the syngas composition of H2 prior to fuel synthesis.

  • 28.
    Wiinikka, Henrik
    et al.
    Energy Technology Centre, Piteå.
    Carlsson, Per
    Granberg, Fredrik
    Chemrec.
    Löfström, Johan
    Chemrec.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Tegman, Ragnar
    Chemrec.
    Lindblom, Mats
    Chemrec.
    Gebart, Rikard
    Swerea SICOMP AB, Box 271, 941 26, Piteå.
    Design and methodology of a high temperature gas sampling system for pressurized black liquor gasification2010In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 89, no 9, p. 2583-2591Article in journal (Refereed)
    Abstract [en]

    This paper describes the system design and methodology for high temperature gas sampling during pressurized black liquor gasification. The motivation for developing a system that can withstand the harsh conditions in the reactor part of the gasifier (30 bar, 1000 °C, reducing conditions and corrosive environment) comes from an ambition to better understand the various stages in the conversion of the fuel (black liquor) and provide spatially resolved data of the gas composition inside the gasification reactor. Important components in the high temperature sampling system which are all described in detail in the paper, are the syngas sampling line, nitrogen purging system, water cooling line and an aerodynamic quench probe with an anti-clogging shield. Several measurement campaigns have been conducted in the gasifier where the concentration of CO2, CO, H2, CH4, H2S, and COS close to the outlet of the hot reactor have been measured with the high temperature gas sampling system. The results showed that the repeatability of the measured gas composition was excellent and that significant effects on the gas composition from different operating parameters of the gasifier could be found.

  • 29.
    Wiinikka, Henrik
    et al.
    Energy Technology Centre, Piteå.
    Gebart, Rikard
    Energy Technology Centre, Piteå.
    Boman, Christoffer
    Umeå universitet.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Influence of fuel ash composition on high temperature aerosol formation in fixed bed combustion of woody biomass pellets2007In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 86, no 1, p. 181-193Article in journal (Refereed)
    Abstract [en]

    In this work, the influence of fuel ash composition on high temperature aerosol formation during fixed bed combustion of woody biomass (two wood pellets and one bark pellets) were investigated experimentally in a laboratory reactor and theoretically through chemical equilibrium model calculations. For all fuels, the particle mass size distribution in the PM2.5 region was bimodal, with one fine mode and one coarse mode. Early in the flame, the fine mode was dominated by particles from incomplete combustion and these particles were rapidly oxidised in the post flame zone. After the hot flame, the fine mode concentration and the particle diameter increases gradually when the temperature decreases due to condensation of vaporised inorganic matter, K, Na, S, Cl, and Zn. For two of the fuels also P could be found in the fine particles. The coarse mode consisted of carbon, refractory metals and considerable amount of alkali. Further, the initial fuel alkali concentration and the alkali to silicon ratio (K + Na)/Si influenced the amount of vaporised aerosol forming alkali matter. Finally, the present study shows that, combustion temperature and fuel ash composition is of major importance for the formation of high temperature aerosols in fixed bed combustion of woody biomass pellets.

  • 30.
    Wolf, Jens
    et al.
    Department of Chemical Engineering and Technology, Division of Energy Processes, Royal Institute of Technology.
    Anheden, Marie
    Vattenfall Research & Development.
    Yan, Jinyue
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Comparison of nickel- and iron-based oxygen carriers in chemical looping combustion for CO2 capture in power generation2005In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 84, no 7-8, p. 993-1006Article in journal (Refereed)
    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

  • 31. Öhrman, Olov
    et al.
    Häggström, Caroline
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Wiinikka, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Analysis of trace components in synthesis gas generated by black liquor gasification2012In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 102, p. 173-179Article in journal (Refereed)
    Abstract [en]

    The only pressurized black liquor gasifier currently in operation is located in Sweden. The composition of the main components in the gas has been reported previously. The main components are H2, CO, CO2, N2, CH4, and H2S. In the present work, trace components in the gas have been characterized and the results are hereby reported for the first time. Samples were taken at two occasions during a one year period. The benzene concentration in the gas varied only slightly and the average concentration was 158 ppm. Benzene is formed by thermal cracking of the biomass. The COS concentration varied substantially and the average concentration was 47 ppm. The variations may be related to how the quench is operated. A few ppm of C2-hydrocarbons were also observed in the gas and the variation was probably a result of varying oxygen to black liquor ratio. No tars were observed in the gas. However, tar compounds, such as phenanthrene, pyrene, fluoranthene and fluorene were detected in deposits found on the pipe walls after the gas cooler. The concentration of particles in the synthesis gas was very low; <0.1 mg/N m3, which is comparable to the particulate matter in ambient air. Submicron particles were comprised of elements such as C, O, Na, Si, S, Cl, K, and Ca, and these particles probably originated from the black liquor. Larger particles were comprised mainly of Fe, S and Ni and these particles probably resulted from corrosion of steel in the plant pipe-work. In summary, the concentrations of trace components and particles in the gas are quite low.

1 - 31 of 31
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