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  • 1.
    Andersson, Jim
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Furusjö, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Landälv, Ingvar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Co-gasification of pyrolysis oil and black liquor for methanol production2015Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 158, s. 451-459Artikkel i tidsskrift (Fagfellevurdert)
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kirtania, Kawnish
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Furusjö, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Co-gasification of black liquor and pyrolysis oil at high temperature: Part 1. Fate of alkali elements2017Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 202, s. 46-55Artikkel i tidsskrift (Fagfellevurdert)
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kirtania, Kawnish
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Furusjö, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Co-gasification of black liquor and pyrolysis oil at high temperature: Part 2. Fuel conversion2017Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 197, s. 240-247Artikkel i tidsskrift (Fagfellevurdert)
    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 tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Unburned carbon in combustion residues from solid biofuels2014Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 117, nr Part A, s. 890-899Artikkel i tidsskrift (Fagfellevurdert)
    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.
    Bozaghian Bäckman, Marjan
    et al.
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University, SE-901 87 Umeå, Sweden; Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden.
    Rebbling, Anders
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University, SE-901 87 Umeå, Sweden.
    Kuba, Matthias
    BEST Bioenergy and Sustainable Technologies GmbH, Graz 8010, Austria; Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna 1060, Austria.
    Larsson, Sylvia H.
    Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University, SE-901 87 Umeå, Sweden.
    Bed material performance of quartz, natural K-feldspar, and olivine in bubbling fluidized bed combustion of barley straw2024Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 364, artikkel-id 130788Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present study investigates how three different silicate-based bed materials behave in bubbling fluidized bed combustion of a model agricultural residue with respect to ash composition, namely barley straw. Quartz, natural K-feldspar, and olivine were all used in combustion at 700 °C, and the resulting layer formation and bed agglomeration characteristics were determined. Based on this, a general reaction model for bed ash from agricultural residues was proposed, taking into account the reactivity of the different silicates investigated towards the main ash-forming elements K, Ca, and Si. The proposed reaction model links bed material interaction with K-rich bed ash to the degree of polymerization of the silicate bed material, where addition reactions occur in systems with high polymerization, predominately in quartz, and substitution reactions dominate for depolymerized silicates such as K-feldspar and olivine.

    Fulltekst (pdf)
    fulltext
  • 6. 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 composition2010Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 89, nr 12, s. 4025-4034Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 7.
    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 properties2018Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 226, s. 345-349Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 8.
    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 method2016Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 182, s. 754-760Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 9.
    Dal Belo Takehara, Marcelo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Investigation of oxygen-enriched biomass flames in a lab-scale entrained flow reactor2024Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 366, artikkel-id 131343Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Oxygen-enriched air combustion of pulverized biomass fuel is an effective method to improve char combustion and improve flame stability. Moreover, understanding the impact of O2 addition is an important step toward oxyfuel combustion, one of the most promising technologies for bioenergy with carbon capture and storage (BECCS). Our previous studies focused on flow manipulation methods, e.g., swirling co-flow and acoustic forcing, to enhance particle dispersion during biomass combustion and gasification. This work aims to extend the understanding of the effect of different manipulation methods on oxygen-enriched combustion at different levels in a lab-scale entrained flow reactor. This methodology combines the analysis of visible flame characteristics, CO and NO gas emissions, and coarse particle emissions characterization with thermogravimetric analysis and particle size distribution by dynamic imaging. The results indicated that oxygen-enriched combustion leads to lower liftoff distance and higher flame brightness. Moreover, oxygen-enriched combustion presented coarse particle emissions with finer particle size distribution and lower carbon content. The acoustic forcing further decreased the flame liftoff and decreased CO emissions, increasing combustion efficiency under conditions with similar equivalence ratios and lower momentum flux at the secondary air.

    Fulltekst (pdf)
    fulltext
  • 10. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Non-coking coal preparation by novel tribo-electrostatic method2008Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 87, nr 17-18, s. 3562-3571Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 11.
    Edison, Thomas Nesakumar Jebakumar Immanuel
    et al.
    School of Chemical Engineering, Yeungnam University, Gyeongsan, Gyeongbuk 38541, Republic of Korea.
    Atchudan, Raji
    School of Chemical Engineering, Yeungnam University, Gyeongsan, Gyeongbuk 38541, Republic of Korea.
    Namachivayam, Karthik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Chandrasekaran, Sundaram
    Guangxi Key Laboratory of Electrochemical and Magneto-chemical, Functional Materials, College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541004, PR China.
    Perumal, Suguna
    School of Chemical Engineering, Yeungnam University, Gyeongsan, Gyeongbuk 38541, Republic of Korea.
    Raja, Pandian Bothi
    School of Chemical Sciences, Universiti Sains Malaysia, Gelugor, 11800 Pulau Pinang, Malaysia.
    Perumal, Veeradasan
    Centre of Innovative Nanostructures and Nanodevices (COINN), Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak Darul Ridzuan, Malaysia. Department of Mechanical Engineering, Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak Darul Ridzuan, Malaysia.
    Lee, Yong Rok
    School of Chemical Engineering, Yeungnam University, Gyeongsan, Gyeongbuk 38541, Republic of Korea.
    Deep eutectic solvent assisted electrosynthesis of ruthenium nanoparticles on stainless steel mesh for electrocatalytic hydrogen evolution reaction2021Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 297, artikkel-id 120786Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Deep eutectic solvents (DES) are considered as a green non-toxic electrolyte for the replacement of cyanide based toxic electrolytes towards the electrodeposition of noble metal and alloy nanoparticles on conducting surfaces. In this work, ruthenium nanoparticles (RuNPs) are electrochemically synthesized over cathodically treated stainless-steel mesh (CSS) by applying the cathodic current of −15 mA/cm2 using ruthenium chloride and deep eutectic mixture consists of choline chloride/urea as electrolyte. The resulting material is abbreviated as RuNPs@CSS and are characterized by surface analytical tools such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning elctron microscopy with energy dispersive spectrum (FE-SEM with EDS). Further, the electrocatalytic hydrogen evolution reaction (HER) activity of RuNPs@CSS is accessed and compared with state of art Pt electrode using open circuit potential (OCP), linear sweep voltammetry (LSV), Tafel plot and electrochemical impedance spectroscopy (EIS) measurements in 0.5 M H2SO4. The calculated HER's onset potential and over potential @ −10 mA/cm2 of RuNPs@CSS are about −0.0273 and −0.0657 V vs. RHE, which are very close to the bare Pt values. The EIS results suggested that, RuNPs@CSS possess excellent conductivity, which decrease the charge transfer resistance and enhances the HER. This study proved that the electrodeposited RuNPs@SS is better replacement for Pt based electrocatalysts towards acidic HER.

  • 12.
    Eriksson, Gunnar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Grimm, Alejandro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Skoglund, Nils
    Umeå universitet.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Combustion and fuel characterisation of wheat distillers dried grain with solubles (DDGS) and possible combustion applications2012Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 102, s. 208-220Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 13. Eriksson, Gunnar
    et al.
    Kjellström, Björn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lundqvist, Björn
    Paulrud, S.
    SLU, Umeå.
    Combustion of wood hydrolysis residue in a 150 kW powder burner2004Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 83, nr 11-12, s. 1635-1641Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 14.
    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 pellets2005Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 84, nr 5, s. 569-575Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 15.
    Faust, Robin
    et al.
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, 412 96 Gothenburg, Sweden.
    Valizadeh, Ali
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Qiu, Ren
    Chalmers University of Technology, Department of Physics, Kemigården 1, Gothenburg, SE-41296, Sweden.
    Tormachen, Alyona
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, 412 96 Gothenburg, Sweden.
    Maric, Jelena
    Division of Energy Technology, Department of Space, Earth, and Environment (SEE), Chalmers University of Technology, Gothenburg, 41296, Sweden.
    Berdugo Vilches, Teresa
    Division of Energy Technology, Department of Space, Earth, and Environment (SEE), Chalmers University of Technology, Gothenburg, 41296, Sweden.
    Skoglund, Nils
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University, SE-901 87 Umeå, Sweden.
    Seemann, Martin
    Division of Energy Technology, Department of Space, Earth, and Environment (SEE), Chalmers University of Technology, Gothenburg, 41296, Sweden.
    Halvarsson, Mats
    Chalmers University of Technology, Department of Physics, Kemigården 1, Gothenburg, SE-41296, Sweden.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Knutsson, Pavleta
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, 412 96 Gothenburg, Sweden.
    Role of Surface Morphology on Bed Material Activation during Indirect Gasification of Wood2023Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 333, Part 1, artikkel-id 126387Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Olivine and alkali-feldspar were utilized in separate campaigns in an indirect dual fluidized bed gasification campaign with woody biomass as fuel. After three days, both bed materials were reported to be active towards tar removal and exhibited oxygen-carrying abilities and had formed an ash layer consisting of an outer ash deposition layer and an inner interaction layer.

    X-ray microtomography analysis concluded that a preferred deposition of ash happens onto convex regions of the bed particles, which results in an increase in thickness of the ash layer over convex regions. This effect is most pronounced for the outer layer which is a product of ash deposition. The inner layer exhibits a homogeneous thickness and is probably formed by interaction of Ca from the outer layer with the particles. Transmission electron microscopy revealed the presence of Fe and Mn on the surface of the particles in a solid solution with Mg. The oxygen-carrying effect which is found for aged particles is therefore attributed to the presence of Fe and Mn on the surface of aged particles. Alkali were found on the surface of both particles which are likely contributing to the catalytic activity of the material towards tar removal.

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  • 16.
    Guo, Ning
    et al.
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU – Norwegian University of Science and Technology, Trondheim, Norway.
    Llamas, Angel David Garcia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Li, Tian
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU – Norwegian University of Science and Technology, Trondheim, Norway.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Løvås, Terese
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU – Norwegian University of Science and Technology, Trondheim, Norway.
    Computational fluid dynamic simulations of thermochemical conversion of pulverized biomass in a dilute flow using spheroidal approximation2020Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 271, artikkel-id 117495Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A drag force model for spheroids, referred as the spheroid model, was implemented in OpenFOAM, in order to better predict the thermochemical conversion of pulverized biomass. Our previous work has found that the spheroid model predicts more dispersed results in terms of particle velocities and local concentrations comparing to other conventional particle models under non-reactive conditions. This work takes the spheroid model one step further, by validating against experiments performed under reactive conditions with a newly implemented heat transfer model for spheroids as well as updated devolatilization kinetic parameters. In addition, simulations were conducted in a configuration similar to a pilot-scale entrained flow gasifier for more realistic scenarios. Particle mass and axial velocity development were compared accordingly using four different modelling approaches with increasing complexity. When compared with models of spheroidal shape assumptions, the sphere and simplified non-sphere model predict 61% and 43% longer residence times, respectively. The combination of the spheroid shape assumption with the heat transfer model for spheroids tends to promote drying and devolatilization. On the other hand, the traditional spherical approach leads to longer particle residence times. These opposing effects are believed to be a major contributing factor to the fact that no significant differences among modelling approaches were found in terms of syngas production at the outlet. Furthermore, particle orientation information was reported in both experiments and simulations under reactive conditions. Its dependency on gas velocity gradient under reactive conditions is similar to what was reported under non-reactive conditions.

  • 17.
    Göktepe, Burak
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hazim, Ammar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Soot reduction in an entrained flow gasifier of biomass by active dispersion of fuel particles2017Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 201, s. 111-117Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 18.
    Hannl, Thomas Karl
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Skoglund, Nils
    Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, AT-1060 Vienna, Austria; BEST - Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, AT-8010 Graz, Austria; Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University, SE-901 87 Umeå, Sweden.
    Priščák, Juraj
    Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, AT-1060 Vienna, Austria; BEST - Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, AT-8010 Graz, Austria.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kuba, Matthias
    Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, AT-1060 Vienna, Austria; BEST - Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, AT-8010 Graz, Austria.
    Bubbling fluidized bed co-combustion and co-gasification of sewage sludge with agricultural residues with a focus on the fate of phosphorus2024Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 357, nr part B, artikkel-id 129822Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, the fate of the ash-forming elements during bubbling fluidized bed combustion and gasification of P-rich sewage sludge (SS) and mixtures with either Si-K-rich wheat straw (WS) or K-Ca-rich sunflower husks (SH) were investigated. The focus of the study was assessing the feasibility of using fuel blends in fluidized bed systems and potential P recovery from the resulting ashes. The used fuels were pure SS and mixtures including 90 wt.% WS (WSS) and 85 wt.% SH (SHS). The analyzed operating conditions were combustion (930–960 °C, λ: 1.2–1.5) and gasification (780–810 °C, λ: 0.4–0.7) in a 5 kW bench-scale reactor. Residual ash and char fractions were collected from different parts of the 5 kW bubbling fluidized bed (bed, cyclone, filter) and analyzed by CHN, SEM/EDS, XRD, and ICP-AES.

    The conversion of the fuel mixtures achieved a steady state under the used process conditions except for the combustion of WSS, which led to the formation of large bed agglomerates with the bed material. The morphology of ash samples after combustion showed that SS fuel pellets mostly maintained their integrity during the experiment. In contrast, the ash and char particles from fuel mixtures were fragmented, and larger quantities were found in the cyclone, the filter, or on interior reactor surfaces. The fate of P was dominated by crystalline Ca-dominated whitlockites in all ash fractions, partially including K for the fuel mixtures SHS and WSS. 76–81 % of ingoing P was found in the bed residue after combustion and gasification of the SS-fuel. After conversion of the fuel mixtures SHS and WSS, the share was lower at 22–48 %, with larger shares of P in the entrained fractions (25–34 %). The quantity of identified crystalline compounds was lower after gasification than combustion, likely due to the limited interaction of ash-forming elements in the residual CHN matrix. Altogether, the results show that fuel mixtures of sewage sludge with agricultural residues could expand the fuel feedstock and enable P recovery. This may be used in the fuel and process design of upscaled fluidized bed processes or systems employing both combustion and gasification.

    Fulltekst (pdf)
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  • 19.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    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 devolatilization2017Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 206, s. 342-351Artikkel i tidsskrift (Fagfellevurdert)
    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

  • 20.
    Häggström, Gustav
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Swerim AB, Box 812, SE-971 25, Luleå, Sweden.
    Hannl, Thomas Karl
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Holmgren, Per
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Broström, Markus
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Skoglund, Nils
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Fate of phosphorus in pulverized fuel co-combustion of sewage sludge and agricultural residues2023Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 335, artikkel-id 127059Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The fate of phosphorus concerning its distribution in the thermal process and chemical speciation was studied during the co-combustion of sewage sludge with wheat straw and sunflower husks in powder combustion conditions. Co-combustion experiments were performed in a lab-scale entrained flow reactor (EFR) at 1000 °C and 1400 °C. SEM-EDS and ICP-OES analyses were used for studies of deposits collected on a probe, bottom ash, and particulate matter samples collected during experiments. Deposition probe samples were further studied and interpreted using powder X-ray diffraction (XRD) and thermochemical equilibrium calculations (TECs). The inorganic material in the different fuel particles mainly interacted through a molten phase observed on deposition probes. Crystalline P was mainly identified in β-Ca3(PO4)2 whitlockites. TECs support the experimental findings and suggest that a mostly homogenous melt occurs at 1400 °C, whereas Fe-oxides and Ca-phosphates precipitate during the cooling of the formed deposits. It was found that <5 % of incoming P was collected in fine particulate matter (<1 µm), indicating that the majority of P can be found in deposits and bottom ash. This outcome implies that P recovery efforts should be focused on these ash fractions.

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  • 21.
    Jayawickrama, Thamali Rajika
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Haugen, Nils Erland L.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Department of Thermal Energy, SINTEF Energy Research, Kolbjørn Hejes vei 1 A, 7491 Trondheim, Norway.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Technical University of Munich, Chair of Energy Systems, Boltzmannstr. 15, 85748 Garching b. München, Germany.
    On the inaccuracies of point-particle approach for char conversion modeling2024Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 370, artikkel-id 131743Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Char conversion is a complex phenomenon that involves not only heterogeneous reactions but also external and internal heat and mass transfer. Reactor-scale simulations often use a point-particle approach (PP approach) as sub-models for char conversion because of its low computational cost. Despite a number of simplifications involved in the PP approach, there are very few studies that systematically investigate the inaccuracies of the PP approach. This study aims to compare and identify when and why the PP approach deviates from resolved-particle simulations (RP approach). Simulations have been carried out for CO2 gasification of a char particle under zone II conditions (i.e., pore diffusion control) using both PP and RP approaches. Results showed significant deviations between the two approaches for the effectiveness factor, gas compositions, particle temperature, and particle diameter. The most significant sources of inaccuracies in the PP approach are negligence of the non-uniform temperature inside the particle and the inability to accurately model external heat transfer. Under the conditions with low effectiveness factors, the errors of intra-particle processes were dominant while the errors of external processes became dominant when effectiveness factors were close to unity. Because it assumes uniform internal temperature, the models applying the PP approach always predict higher effectiveness factors than the RP approach, despite its accurate estimation of intra-particle mass diffusion effects. As a consequence, the PP approach failed to predict the particle size changes accurately. Meanwhile, no conventional term for external heat transfer could explain the inaccuracy, indicating the importance of other sources of errors such as 2D/3D asymmetry or penetration of external flows inside the particles.

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  • 22.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Modeling biomass char gasification kinetics for improving prediction of carbon conversion in a fluidized bed gasifier2014Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 132, s. 107-115Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 23.
    Kuba, Matthias
    et al.
    BEST Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, 8010 Graz, Austria. TU Wien, Institute of Chemical, Environmental and Bioscience Engineering, Getreidemarkt 9/166, 1060 Vienna, Austria.
    Skoglund, Nils
    Thermochemical Energy Conversion Laboratory, Umeå University, SE-901 87 Umeå, Sweden.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hofbauer, Hermann
    TU Wien, Institute of Chemical, Environmental and Bioscience Engineering, Getreidemarkt 9/166, 1060 Vienna, Austria.
    A review on bed material particle layer formation and its positive influence on the performance of thermo-chemical biomass conversion in fluidized beds2021Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 291, artikkel-id 120214Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Bed material particle layer formation plays a significant role in thermo-chemical conversion of biomass. The interaction between biomass ash and bed material in fluidized bed conversion processes has been described for a variety of different applications and spans from fundamental research of formation mechanisms to effects of this layer formation on long-term operation in industrial-scale. This review describes the current state of the research regarding the mechanisms underlying layer formation and the positive influence of bed material particle layer formation on the operation of thermo-chemical conversion processes. Thus, the main focus lies on its effect on the catalytic activity towards gasification reactions and the impact on oxygen transport in chemical looping combustion. The review focuses on the most commonly investigated bed materials, such as quartz, feldspar or olivine. While the most relevant results for both the underlying mechanisms and the subsequently observed effects on the operation are presented and discussed, knowledge gaps where further research is necessary are identified and described.

  • 24.
    Llamas, Angel David Garcia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Guo, Ning
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU - Norwegian University of Science and Technology, Trondheim, Norway.
    Li, Tian
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU - Norwegian University of Science and Technology, Trondheim, Norway.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Løvås, Terese
    Department of Energy and Process Engineering, Faculty of Engineering, NTNU - Norwegian University of Science and Technology, Trondheim, Norway.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Morphology and volume fraction of biomass particles in a jet flow during devolatilization2020Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 278, artikkel-id 118241Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Particle size, aspect ratio (AR, defined here as major over minor dimension), orientation and volume fraction have been measured for a stream of pulverized biomass particles undergoing devolatilization. Milling of raw biomass for thermochemical conversion yields elongated particles with high AR. Particle shape affects the heat and mass transfers and motion of particles within a jet, potentially shifting the particle group regimes. Therefore, the effects of carrier gas flow and fuel AR on the devolatilization behavior of biomass particles streams have been addressed experimentally. Two shapes of dried Norwegian Spruce have been used: one nearly equant (AR = 1.8 ± 0.64) and the other elongated (AR = 3.8 ± 2.9), both derived from the same sieve size of 200–250 μm. Experiments were performed in a laboratory-scale flat-flame assisted laminar drop tube reactor, where similar mass flows of particles (10–16 g⋅h−1) were injected with two different flow rates of CO2 to a high temperature flame zone (methane flame at O2-to-fuel equivalence ratio of λ = 0.63). Time and space-averaged measurements of particle morphology and velocity during conversion were obtained with 2D particle tracking velocimetry (PTV) together with image analysis. Carrier gas flow acted as thermal ballast, affecting the heating rate to the gas and particles. Heterogeneity in morphological changes was observed, and the behavior was affected by heating rate, particle shape and carrier gas flows. This paper describes phenomena relevant for the understanding of biomass devolatilization under very fast heating rates, such as shrinking, transient swelling, spherodization and lateral migration, and relates them to differences in heating rate and particle shape.

  • 25.
    Magalhães, Duarte
    et al.
    Mechanical Engineering Department, Middle East Technical University, Ankara, Turkey.
    Gürel, Kaan
    Mechanical Engineering Department, Middle East Technical University, Ankara, Turkey.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Pisano, Italo
    Department of Chemical Sciences, University of Limerick, Limerick, Ireland; Celignis Biomass Analysis Laboratory, Holland Road, Castletroy, Co. Limerick, Ireland.
    Leahy, J.J.
    Department of Chemical Sciences, University of Limerick, Limerick, Ireland.
    Kazanç, Feyza
    Mechanical Engineering Department, Middle East Technical University, Ankara, Turkey.
    Trubetskaya, Anna
    Department of Chemical Sciences, University of Limerick, Limerick, Ireland.
    Prediction of yields and composition of char from fast pyrolysis of commercial lignocellulosic materials, organosolv fractionated and torrefied olive stones2021Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 289, artikkel-id 119862Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigated the fast pyrolysis behaviour of torrefied olive stones, fractionated olive stones and lignocellulosic commercial compounds. Olive stones were reacted in a continuous industrial torrefaction unit. The olive stones were also fractionated into their main components in an organosolv reactor at temperatures from 170 to 190 °C in both the presence and absence of an acidic catalyst. All samples were reacted in a wire mesh reactor at different temperatures (800–1150 °C) and heating rates (400–1150 °C/s), and the solid product was characterised for its yield, morphology, and elemental composition. The char yields from fast pyrolysis of commercially available cellulose, hemicelluloses, and lignin were compared with yields of fractionated olive stones. A model was developed to compare the measured yields of olive stones with the predicted yields using fractionated or commercial components. The presence of acid during fractionation had a stronger effect than the temperature, particularly on the lignin fraction. The fractionated lignocellulosic compounds provided more accurate predictions of the char yields of olive stones, as compared to the commercial lignocellulosic compounds. The fractionation at 180 °C without acid catalyst gave the cellulose, hemicellulose, and lignin with highest degree of purity and resulted in the most accurate predictions of the experimental yields of olive stones. The results showed that interactions between the lignocellulosic components were not significant. The char yield of each fractioned compound and non-treated olive stones could be accurately predicted from the lignocellulosic content which has importance for biorefinery applications in which each fraction is used as a value-added product.

  • 26.
    Marklund, Magnus
    et al.
    Energy Technology Centre (ETC), Piteå, Sweden.
    Tegman, Ragnar
    Chemrec AB, c/o ETC, Piteå, Sweden.
    Gebart, Rikard
    Energy Technology Centre (ETC), Piteå, Sweden.
    CFD modelling of black liquor gasification: Identification of important model parameters2007Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 86, nr 12-13, s. 1918-1926Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 27.
    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 method2016Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 177, s. 274-278Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 28.
    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 designs1995Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 74, nr 1, s. 128-135Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 29.
    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 combustion2001Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 80, nr 10, s. 1391-1398Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 30.
    Phounglamcheik, Aekjuthon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bäckebo, Markus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Robinson, Ryan
    Global Technology, Höganäs AB, Höganäs, Sweden.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    The significance of intraparticle and interparticle diffusion during CO2 gasification of biomass char in a packed bed2022Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 310, artikkel-id 122302Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigates the influences of intraparticle and interparticle diffusions on the reaction rates of char gasification in a packed bed without forced convective flows. The main objective is to elucidate how the dominant scales of mass diffusion resistance change based on particle size distributions (PSD). CO2 gasification rates were measured by thermogravimetric analyses (TGA) of spruce char produced from pilot-scale reactors. Experimental setups using two TGA devices highlighted the effects on different rate-limiting steps. Effects of intraparticle diffusion were investigated with a single layer of monodispersed particles between 75 µm and 6.3 mm using a commercial TGA. Effects of interparticle diffusion were investigated with a packed bed of monodispersed and polydispersed particles using a macro-TG. At the particle scale, gasification rate decreased with the increase of particle size when the reaction was controlled by intraparticle diffusion. This effect can be described by the effectiveness factor with Thiele modulus. At the bed scale, void fraction and tortuosity of the packed bed are influential parameters on diffusivity of CO2 through the bed channels. Due to its non-sphericity of the char particles, the bed of relatively large particles had high void fraction and the presence of smaller particles were essential to lower the bed void size. Consequently, smaller size fraction in the PSD had a major impact on the diffusion resistance at bed scale. It means that the diffusion resistances at particle and bed scales are sensitive to different size fractions in the PSD. It allows one to tweak the overall reaction rates in packed beds by manipulating the PSD if the dominant mass transport mechanism is diffusion.

  • 31.
    Priščák, Juraj
    et al.
    BEST—Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, A-8010 Graz, Austria; TU Wien, Institute of Chemical, Environmental and Bioscience Engineering (ICEBE), Getreidemarkt 9/166, 1060 Vienna, Austria.
    Valizadeh, Ali
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hofbauer, Hermann
    TU Wien, Institute of Chemical, Environmental and Bioscience Engineering (ICEBE), Getreidemarkt 9/166, 1060 Vienna, Austria.
    Kuba, Matthias
    BEST—Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, A-8010 Graz, Austria; TU Wien, Institute of Chemical, Environmental and Bioscience Engineering (ICEBE), Getreidemarkt 9/166, 1060 Vienna, Austria.
    Effect of time-dependent layer formation on the oxygen transport capacity of ilmenite during combustion of ash-rich woody biomass2023Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 353, artikkel-id 129068Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Oxygen carrier aided combustion (OCAC) is a novel technology that aims to enhance combustion of heterogenous fuels by replacing the inert bed material with an active oxygen carrier. One of the promising oxygen carriers is natural ilmenite which shows decent oxygen transport capacity and mechanical stability under OCAC operating conditions. However, interactions between ilmenite and woody biomass ash lead to the formation of a calcium-rich ash layer, which affects the ability of the oxygen carrier (OC) to transfer oxygen throughout the boiler and subsequently decreases the combustion efficiency. This paper focuses on the time-dependent morphological and compositional changes in ilmenite bed particles and the consequence effects on the oxygen transport capacity and reactivity of ilmenite. Ilmenite utilized in this study was investigated in a 5 kW bubbling fluidized bed combustion unit, utilizing ash-rich bark pellets as fuel. A negative effect of iron migration on the oxygen transport capacity was observed in ilmenite bed particles after 6 h of operation in the bubbling fluidized bed reactor. The decrease in the oxygen transport capacity of ilmenite was found to correlate with the increased exposure time in the fluidized bed reactor and was caused by the migration and subsequent erosion of Fe from the ilmenite particles. On the other hand, the older bed particles show an increase in reaction rate, presumably due to the catalytic activity of the calcium-enriched outer layer on the bed particle surface.

  • 32.
    Risberg, Mikael
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Öhrman, Olov G. W.
    Energy Technology Centre in Piteå, Box 726, SE-941 28 Piteå, Sweden.
    Gebart, B. Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Nilsson, Patrik
    Lund University, Faculty of Engineering, Ergonomics and Aerosol Technology, P.O. Box 118, SE-221 00 Lund, Sweden.
    Gudmundsson, Anders
    Lund University, Faculty of Engineering, Ergonomics and Aerosol Technology, P.O. Box 118, SE-221 00 Lund, Sweden.
    Sanati, Mehri
    Lund University, Faculty of Engineering, Ergonomics and Aerosol Technology, P.O. Box 118, SE-221 00 Lund, Sweden.
    Influence from fuel type on the performance of an air-blown cyclone gasifier2014Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 116, s. 751-759Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 33.
    Sayan, S.
    et al.
    Bilkent University, Chemistry, Bilkent–Ankara, Turkey.
    Demirel, B.
    University of Utah, Chemical and Fuels Engineering, Salt Lake City, UT, USA.
    Paul, Jan
    Hacettepe University, Chemistry, Beytepe–Ankara, Turkey.
    Methyldecalin hydrocracking over palladium/zeolite-X2000Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 79, nr 11, s. 1395-1404Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 34.
    Schneider, Christoph
    et al.
    Karlsruhe Institute of Technology, Engler-Bunte-Institute, Fuel Technology, EBI ceb, Engler-Bunte-Ring 1, 76131 Karlsruhe, Germany.
    Walker, Stella
    Karlsruhe Institute of Technology, Engler-Bunte-Institute, Fuel Technology, EBI ceb, Engler-Bunte-Ring 1, 76131 Karlsruhe, Germany.
    Phounglamcheik, Aekjuthon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kolb, Thomas
    Karlsruhe Institute of Technology, Engler-Bunte-Institute, Fuel Technology, EBI ceb, Engler-Bunte-Ring 1, 76131 Karlsruhe, Germany. Karlsruhe Institute of Technology, Institute for Technical Chemistry, ITC vgt, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
    Effect of calcium dispersion and graphitization during high-temperature pyrolysis of beech wood char on the gasification rate with CO22021Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 283, artikkel-id 118826Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents thermal deactivation of beech wood chars during secondary pyrolysis in a drop-tube reactor. Pyrolysis temperature was varied between 1000 °C and 1600 °C at a constant residence time of 200 ms. The effect of pyrolysis conditions on initial conversion rate R0 during gasification, graphitization of the carbon matrix and ash morphology was investigated. Gasification experiments for the determination of R0 were conducted in a thermogravimetric analyzer using pure CO2 at 750 °C and isothermal conditions. A linear decrease in initial conversion rate R0 was observed between 1000 °C and 1400 °C. However, a strong increase of R0 at 1600 °C was encountered. Micropore surface area of the secondary chars showed no correlation with the initial conversion rate R0 during gasification with CO2. Graphitization of the carbon matrix was determined using X-ray diffraction and Raman spectroscopy suggesting the growth of aromatic clusters and graphite-like structures for increasing pyrolysis temperatures up to 1600 °C. Furthermore, CaO dispersion was analyzed quantitatively and qualitatively using temperature-programmed reaction at 300 °C as well as SEM/TEM. CaO dispersion DCaO decreases steadily between 1000 °C and 1400 °C whereas a strong increase can be observed at 1600 °C, which is in good accordance with the development of the initial conversion rate R0 as a function of pyrolysis temperature. SEM/TEM images indicate the formation of a thin CaO layer at 1600 °C that is presumably responsible for the strong increase in initial conversion rate R0 at this temperature. When excluding the catalytic activity of CaO via formation of the ratio R0 DCaO−1, increasing graphitization degree has a linear negative influence on char reactivity at pyrolysis temperatures between 1000 °C and 1400 °C.

  • 35.
    Sedlmayer, Irene
    et al.
    BIOENERGY 2020+ GmbH.
    Arshadi, Mehrdad
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Haslinger, Walter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. 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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    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 analysis2018Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 234, s. 894-903Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 36.
    Seferinoğlu, Meryem
    et al.
    Luleå tekniska universitet. MTA, Mineral Research and Exploration Directorate, Balgat, Ankara, Turkey.
    Paul, Mehtap
    Luleå tekniska universitet.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Köker, Agah
    MTA, Mineral Research and Exploration Directorate, Balgat, Ankara, Turkey.
    Toprak, Selami
    MTA, Mineral Research and Exploration Directorate, Balgat, Ankara, Turkey.
    Paul, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Acid leaching of coal and coal-ashes2003Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 82, nr 4, s. 1721-1734Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 37.
    Sefidari, Hamid
    et al.
    Department of Bioenergy Technology, Linnaeus University, SE-351 95 Växjö, Sweden.
    Razmjoo, Narges
    Department of Bioenergy Technology, Linnaeus University, SE-351 95 Växjö, Sweden.
    Strand, Michael
    Department of Bioenergy Technology, Linnaeus University, SE-351 95 Växjö, Sweden.
    An experimental study of combustion and emissions of two types of woody biomass in a 12-MW reciprocating-grate boiler2014Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 135, s. 120-129Artikkel i tidsskrift (Fagfellevurdert)
  • 38.
    Trubetskaya, Anna
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    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 tekniska universitet, Institutionen för hälsovetenskap, Medicinsk vetenskap.
    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 modeling2017Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 206, s. 675-683Artikkel i tidsskrift (Fagfellevurdert)
    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.

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  • 39.
    Trubetskaya, Anna
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. 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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Potassium and soot interaction in fast biomass pyrolysis at high temperatures2018Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 225, s. 89-94Artikkel i tidsskrift (Fagfellevurdert)
    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.

    Fulltekst (pdf)
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  • 40.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Wiinikka, Henrik
    RISE Bioekonomi/RISE Energy Technology Center AB, Piteå, Sweden.
    Spray combustion of biomass fast pyrolysis oil: Experiments and modeling2019Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 237, s. 580-591Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 41.
    Valizadeh, Ali
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Skoglund, Nils
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University, SE-90187 Umeå, Sweden.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lycksam, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    A comparative study in 3D of bed particle layer characteristics in quartz and K-feldspar from fluidized bed combustion of woody biomass using X-ray microtomography2023Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 342, artikkel-id 127707Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bed particle layer and crack layer characteristics at different ages were studied for quartz and K-feldspar bed particles from a 30 MWth bubbling fluidized bed and a 90 MWth circulating fluidized bed, both using woody biomass as fuel. X-ray microtomography (XMT) was utilized to determine the bed particle layer distribution on the bed particles' surface. For each bed particle type, the average bed particle layer thickness as well as average volume fractions of the bed particle layer and crack layers to the entire bed particle volume were determined at three different bed particle ages by utilizing XMT analysis. Comparison of the two different bed particle types showed that K-feldspar retains a thinner bed particle layer in both conversion processes compared to quartz. Crack layers were observed extensively in quartz bed particles to the extent of 19.3 vol% and 32.1 vol% after 13 days in the BFB and the CFB, respectively, which could cause deposition of the bed particle fragments. On the contrary, K-feldspar has almost no tendency toward forming crack layers.

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  • 42.
    Valizadeh, Ali
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Skoglund, Nils
    Department of Applied Physics and Electronics, Umeå University, SE-90187 Umeå, Sweden.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lycksam, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Role of surface morphology in bed particle layer formation on quartz bed particles in fluidized bed combustion of woody biomass2024Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 357, nr part A, artikkel-id 129702Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of quartz bed particle surface morphology on the bed particle layer and crack layer formation process in fluidized bed combustion of woody biomass was investigated in this work. Bed material samples were collected at different sampling times from the startup with a fresh bed in industrial scale bubbling fluidized bed (BFB) and circulating fluidized bed (CFB) boilers, both utilizing woody biomass. X-ray microtomography (XMT) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) were employed to characterize bed particle layers and crack layers in the samples. Results showed that there is a noticeable difference between the bed layer characteristics over the so-called “concave” and “convex”-shaped morphologies on the bed particle surface with respect to layer formation. The concave areas are mainly covered with a thin inner layer, whilst the convex display a comparably thick inner layer and an outer layer. In addition, 3D images of the particles revealed that the crack layers mainly originate from concave areas where the particle is less protected by an outer bed particle layer in conjunction with cracks in the inner layer.

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    fulltext
  • 43.
    Wartha, Eva-Maria
    et al.
    TU Wien, Institute of Chemical, Environmental and Bioscience Engineering, Getreidemarkt 9/166, 1060 Vienna, Austria.
    Haugen, Nils Erland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. SINTEF Energi A.S., Sem Saelands vei 11, 7034 Trondheim, Norway.
    Karchniwy, Ewa
    SINTEF Energi A.S., Sem Saelands vei 11, 7034 Trondheim, Norway.
    Bösenhofer, Markus
    TU Wien, Institute of Chemical, Environmental and Bioscience Engineering, Getreidemarkt 9/166, 1060 Vienna, Austria; K1-Met GmbH, Area 4 - Simulation and Analyses, Stahlstrasse 14, BG 88, 4020 Linz, Austria.
    Harasek, Michael
    TU Wien, Institute of Chemical, Environmental and Bioscience Engineering, Getreidemarkt 9/166, 1060 Vienna, Austria.
    Løvås, Terese
    Department of Energy and Process Engineering, Norwegian University of Science and Technology, Kolbjørn Hejes vei 1B, 7034 Trondheim, Norway.
    The effect of turbulence on the conversion of coal under blast furnace raceway conditions2023Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 331, nr Part 2, artikkel-id 125840Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main production route for steel in Europe is still via the blast furnace. Computational fluid dynamics (CFD) can be used to analyze the process virtually and thus improve its performance. Different reducing agents can be used to (partially) substitute the coke and consequently reduce overall emissions. To analyze different reducing agents effectively using CFD, their conversion process has to be modeled accurately. Under certain conditions, coal particles can cluster as the result of turbulence effects, which further reduces the mass transfer to the coal surface and consequently the conversion rate. We analyze the effect of turbulence under blast furnace raceway conditions on the conversion of coal particles and on the overall burnout. The model is applied in RANS to polydisperse particle systems and this is then compared to the simplified monodisperse assumption. Additionally, the model is extended by adding gasification reactions. Overall, we find that the turbulent effects on coal conversion are significant under blast furnace raceway conditions and should be considered in further simulations. Furthermore, we show that an a-priori assessment is difficult because the analysis via averaged quantities is impractical due to a strong variation of conditions in the furnace. Therefore, the effects of turbulence need to be correlated to the regions of conversion.

  • 44.
    Weiland, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. SP Energy Technology Center AB, Box␣726, S-941 28, Piteå, Sweden.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. SP Energy Technology Center AB, Box␣726, S-941 28, Piteå, Sweden.
    Hedman, Henry
    SP Energy Technology Center AB, Box␣726, S-941 28, Piteå, Sweden.
    Wennebro, Jonas
    SP Energy Technology Center AB, Box␣726, S-941 28, Piteå, Sweden.
    Pettersson, Esbjörn
    SP Energy Technology Center AB, Box␣726, S-941 28, Piteå, Sweden.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Influence of process parameters on the performance of an oxygen blown entrained flow biomass gasifier2015Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 153, s. 510-519Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 45.
    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 gasification2010Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 89, nr 9, s. 2583-2591Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 46.
    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 pellets2007Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 86, nr 1, s. 181-193Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 47.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Comparison of nickel- and iron-based oxygen carriers in chemical looping combustion for CO2 capture in power generation2005Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 84, nr 7-8, s. 993-1006Artikkel i tidsskrift (Fagfellevurdert)
    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

  • 48.
    Öhrman, Olov
    et al.
    Energy Technology Centre in Piteå, Box 726, 941 28 Piteå, Sweden.
    Häggström, Caroline
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Wiinikka, Henrik
    Energy Technology Centre in Piteå, Box 726, 941 28 Piteå, Sweden.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Analysis of trace components in synthesis gas generated by black liquor gasification2012Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 102, s. 173-179Artikkel i tidsskrift (Fagfellevurdert)
    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.

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