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  • 1.
    Boström, Dan
    et al.
    Umeå universitet.
    Boström, Markus
    Umeå universitet.
    Skoglund, Nils
    Umeå universitet.
    Boman, Christoffer
    Umeå universitet.
    Backman, Rainer
    Umeå universitet.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Grimm, Alejandro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Ash transformation chemistry during energy conversion of biomass2010Ingår i: Proceedings of the International Conference on Impact of Fuel Quality on Power production and the Environment, 2010Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    There is relatively extensive knowledge available concerning ash transformation reactions during energy conversion of woody biomass. Traditionally, these assortments have constituted the main resources for heating in Sweden. In recent decades the utilization of these energy carriers has increased, from a low technology residential small scale level to industrial scale (e.g. CHP plants). Along this evolution ash-chemical related phenomena for woody biomass has been observed and studied. So, presently the understanding for these are, if not complete, fairly good. Briefly, from a chemical point of view the ash from woody biomass could be characterized as a silicate dominated systems with varying content of basic oxides and with relatively high degree of volatilization of alkali sulfates and chlorides. Thus, the main ash transformation mechanisms in these systems have been outlined. Here, an attempt to give a general description of the ash transformation reactions of biomass fuels is presented, with the intention to provide guidance in the understanding of ash matter behavior in the utilization of any biomass fuel, primarily from knowledge of the concentrations of ash forming elements but also by considering the physical condition in the specific combustion appliance and the physical characteristic of the biomass fuel. Furthermore, since the demand for CO2-neutral energy resources has increased the last years and will continue to do so in the foreseeable future, other biomasses as for instance agricultural crops has become highly interesting. Globally, the availability of these shows large variation. In Sweden, for instance, which is a relatively spare populated country with large forests, these bio-masses will play a secondary role, although not insignificant. In other parts of the world, more densely populated and with a large agricultural sector, such bio-masses may constitute the main energy bio-mass resource in the future. However, the content of ash forming matter in agricultural bio-mass is rather different in comparison to woody biomass. Firstly, the content is much higher; from being about 0.3 - 0.5% (wt) in stem wood, it can amount to between 2 and 10 %(wt) in agricultural biomass. In addition, the composition of the ash forming matter is different. Shortly, the main difference is due to a much higher content of phosphorus (occasionally also silicon) which has major consequences on the ash-transformation reactions. In many crops, the concentration of phosphorus and silicon is equivalent, which (depending on the concentration levels of basic oxides) may result in a phosphate dominated ash. The properties of this ash are in several aspects different from the silicate dominated woody biomass ash and will consequently behave differently in various types of energy conversion systems. The knowledge about phosphate dominated ash systems has so far been scarce. We have been working with these systems, both with basic and applied research, for about a decade know. Some general experiences and conclusions as well as some specific examples of our research will be presented

  • 2.
    Boström, Dan
    et al.
    Umeå universitet.
    Grimm, Alejandro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Skoglund, Nils
    Umeå universitet.
    Boman, Christoffer
    Umeå universitet.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Broström, Markus
    Umeå universitet.
    Backman, Rainer
    Umeå universitet.
    Ash transformation chemistry during combustion of biomass2012Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 26, nr 1, s. 85-93Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is relatively extensive knowledge available concerning ash transformation reactions during combustion of woody biomass. In recent decades, the use of these energy carriers has increased, from a low-technology residential small-scale level to an industrial scale. Along this evolution, ash chemical-related phenomena for woody biomass have been observed and studied. Therefore, presently the understanding for these are, if not complete, fairly good. However, because the demand for CO2-neutral energy resources has increased recently and will continue to increase in the foreseeable future, other biomasses, such as, for instance, agricultural crops, have become highly interesting. The ash-forming matter in agricultural biomass is rather different in comparison to woody biomass, with a higher content of phosphorus as a distinctive feature. The knowledge about the ash transformation behavior in these systems is far from complete. Here, an attempt to give a schematic but general description of the ash transformation reactions of biomass fuels is presented in terms of a conceptual model, with the intention to provide guidance in the understanding of ash matter behavior in the use of any biomass fuel, primarily from the knowledge of the concentrations of ash-forming elements. The model was organized in primary and secondary reactions. Restrictions on the theoretical model in terms of reactivity limitations and physical conditions of the conversion process were discussed and exemplified, and some principal differences between biomass ashes dominated by Si and P, separately, were outlined and discussed.

  • 3.
    Bozaghian, Marjan
    et al.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Rebbling, Anders
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Larsson, Sylvia H.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology, Biomass Technology Centre.
    Thyrel, Mikael
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Xiong, Shaojun
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Combustion characteristics of straw stored with CaCO3 in bubbling fluidized bed using quartz and olivine as bed materials2018Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 212, s. 1400-1408Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The addition of Ca-containing compounds can reduce mass loss from agricultural biomass during storage. The resulting alkaline environment is detrimental to microorganisms present in the material. Theoretical analysis of Ca-containing biomass suggests that combustion properties are improved with respect to slagging. To validate the theoretical calculations, barley straw was utilized as a typical model agricultural biomass and combustion characteristics of straw pre-treated with 2 and 4 w/w% CaCO3 for combined improvement of storage and combustion properties were determined through combustion at 700 °C in a bench-scale bubbling fluidized-bed reactor (5 kW) using quartz and olivine sand as bed materials. The combustion characteristics were determined in terms of elemental composition and compound identification in bed ash and bed material including agglomerates, fly ash, particulate matter as well as flue gas measurements. The addition of CaCO3 to straw had both positive and negative effects on its combustion characteristics. Both additive levels raised the total defluidization temperature for both quartz and olivine, and olivine proved to be less susceptible than quartz to reactions with alkali. With Ca-additives, the composition of deposits and fine particulate matter changed to include higher amounts of KCl potentially leading to higher risk for alkali chloride-induced corrosion. Flue gas composition was heavily influenced by CaCO3 additives by significantly elevated CO concentrations likely related to increased levels of gaseous alkali compounds. The results suggest that it is necessary to reduce gaseous alkali compounds, e.g. through kaolin or sulphur addition, if alkali-rich straw is to be co-combusted with Ca-rich biomass or large amounts of Ca-additives

  • 4.
    Brännvall, Evelina
    et al.
    Luleå tekniska universitet, Verksamhetsstöd, Externfinansiering. Waste Science and Technology, Luleå University of Technology.
    Nilsson, Malin
    Waste Science and Technology, Luleå University of Technology.
    Sjöblom, Rolf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik. Waste Science and Technology, Luleå University of Technology.
    Skoglund, Nils
    Umeå University. Department of Applied Physics and Electronics.
    Kumpiene, Jurate
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik. Waste Science and Technology, Luleå University of Technology.
    Effect of residue combinations on plant uptake of nutrients and potentially toxic elements2014Ingår i: Journal of Environmental Management, ISSN 0301-4797, E-ISSN 1095-8630, Vol. 132, s. 287-295Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of the plant pot experiment was to evaluate potential environmental impacts of combined industrial residues to be used as soil fertilisers by analysing i) element availability in fly ash and biosolids mixed with soil both individual and in combination, ii) changes in element phytoavailability in soil fertilised with these materials and iii) impact of the fertilisers on plant growth and element uptake.Plant pot experiments were carried out, using soil to which fresh residue mixtures had been added. The results showed that element availability did not correlate with plant growth in the fertilised soil with. The largest concentrations of K (3534mg/l), Mg (184mg/l), P (1.8mg/l), S (760mg/l), Cu (0.39mg/l) and Zn (0.58mg/l) in soil pore water were found in the soil mixture with biosolids and MSWI fly ashes; however plants did not grow at all in mixtures containing the latter, most likely due to the high concentration of chlorides (82g/kg in the leachate) in this ash. It is known that high salinity of soil can reduce germination by e.g. limiting water absorption by the seeds. The concentrations of As, Cd and Pb in grown plants were negligible in most of the soils and were below the instrument detection limit values.The proportions of biofuel fly ash and biosolids can be adjusted in order to balance the amount and availability of macronutrients, while the possible increase of potentially toxic elements in biomass is negligible seeing as the plant uptake of such elements was low. © 2013 Elsevier Ltd.

  • 5.
    Edo, Mar
    et al.
    Department of Chemistry, Umeå University.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gao, Qiuju
    Department of Chemistry, Umeå University.
    Persson, Per-Erik
    VafabMiljö Kommunalförbund, SE-721 87 Västerås.
    Jansson, Stina
    Department of Chemistry, Umeå University.
    Fate of metals and emissions of organic pollutants from torrefaction of waste wood, MSW, and RDF2017Ingår i: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 68, s. 646-652Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Torrefaction of municipal solid waste (MSW), refuse-derived fuel (RDF), and demolition and construction wood (DC) was performed at 220 °C and a residence time of 90 min in a bench-scale reactor. The levels of toxic polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) contained in emission from the torrefaction process were evaluated. In addition, main ash-forming elements and trace metals in the raw feedstock and char were determined. The use of MSW in fuel blends with DC resulted in lower PCDD and PCDF emissions after torrefaction, compared with the RDF blends. The migration of chlorine from the feedstock to the gas phase reduces the chlorine content of the char which may reduce the risk of alkali chloride-corrosion in char combustion. However, trace metals catalytically active in the formation of PCDD and PCDF remain in the char, thereby may promote PCDD and PCDF formation during subsequent char combustion for energy recovery; this formation is less extensive than when the feedstock is used.

  • 6.
    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 applications2012Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 102, s. 208-220Artikel i tidskrift (Refereegranskat)
    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.

  • 7.
    Grimm, Alejandro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Skoglund, Nils
    Umeå universitet.
    Boström, Dan
    Umeå universitet.
    Boman, Christoffer
    Umeå universitet.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Influence of phosphorus on alkali distribution during combustion of logging residues and wheat straw in a bench-scale fluidized bed2012Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 26, nr 5, s. 3012-3023Artikel i tidskrift (Refereegranskat)
  • 8.
    Grimm, Alejandro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Skoglund, Nils
    Umeå university.
    Boström, Dan
    Umeå university.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bed agglomeration characteristics in fluidized quartz bed combustion of phosphorus-rich biomass fuels2011Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 25, nr 3, s. 937-947Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The bed agglomeration characteristics during combustion of phosphorus-rich biomass fuels and fuel mixtures were determined in a fluidized (quartz) bed reactor (5 kW). The fuels studied (separately and in mixtures) included logging residues, bark, willow, wheat straw, and phosphorus-rich fuels, like rapeseed meal (RM) and wheat distillers dried grain with solubles (DDGS). Phosphoric acid was used as a fuel additive. Bed material samples and agglomerates were studied by means of scanning electron microscopy (SEM) in combination with energy-dispersive X-ray spectroscopy (EDX), in order to analyze the morphological and compositional changes of coating/reaction layers and necks between agglomerated bed particles. Furthermore, bed ash particles were separated by sieving from the bed material samples and analyzed with SEM/EDS and powder X-ray diffraction (XRD). For logging residues, bark, and willow, with fuel ash rich in Ca and K but with low contents of P and organically bound Si, the bed layer formation is initiated by reactions of gaseous or liquid K compounds with the surface of the bed material grains, resulting in the formation of a potassium silicate melt. The last process is accompanied by the diffusion/dissolving of Ca into the melt and consequent viscous flow sintering and agglomeration. The addition of high enough phosphorus content to convert the available fuel ash basic oxides into phosphates reduced the amount of K available for the reaction with the quartz bed material grains, thus preventing the formation of an inner bed particle layer in the combustion of logging residues, bark, and willow. Some of the phosphate-rich ash particles, formed during the fuel conversion, adhered and reacted with the bed material grains to form noncontinuous phosphate−silicate coating layers, which were found responsible for the agglomeration process. Adding phosphorus-rich fuels/additives to fuels rich in K and Si (e.g., wheat straw) leads to the formation of alkali-rich phosphate−silicate ash particles that also adhered to the bed particles and caused agglomeration. The melting behavior of the bed particle layers/coatings formed during combustion of phosphorus-rich fuels and fuel mixtures is an important controlling factor behind the agglomeration tendency of the fuel and is heavily dependent on the content of alkaline earth metals in the fuel. A general observation is that phosphorus is the controlling element in ash transformation reactions during biomass combustion in fluidized quartz beds because of the high stability of phosphate compounds.

  • 9.
    Grimm, Alejandro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Skoglund, Nils
    Umeå universitet.
    Eriksson, Gunnar
    Boström, Dan
    Umeå universitet.
    Boman, Christoffer
    Umeå universitet.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Effekter av fosfortillsats vid förbränning av biomassa2010Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Resultaten från försöken visar att fosforrika additiv kan vara intressanta för att reducera beläggningsbildning och högtemperaturkorrosion utan att i någon större omfattning öka slaggnings- och bäddagglomereringstendensen hos typiska biobränslen. För att erhålla en märkbar positiv effekt av kaliumbindning till fosfater krävs att mängden kalcium och magnesium i den slutgiltiga bränslemixen inte är alltför hög relativt mängden fosfor, då framför allt Ca men till viss del även Mg reagerar med P innan K binds in effektivt. Generellt behövs troligen inblandningsgrader motsvarande en molkvot P/(K+Na+2/3Mg+2/3Ca) i bränslemixen som närmar sig 1. För att erhålla en molkvot på 1 i ett typiskt halm-, salix- eller grotbränsle innebär det i praktiken en fosfortillsats motsvarande 12, 4.7 respektive 3.7 gram rent P per kg torrt bränsle.

  • 10.
    He, Hanbing
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Time-Dependent Crack Layer Formation in Quartz Bed Particles during Fluidized Bed Combustion of Woody Biomass2017Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, nr 2, s. 1672-1677Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bed agglomeration during combustion and gasification of woody biomass fuels in quartz beds has been frequently studied, and chemical mechanisms responsible for bed agglomeration have been suggested. However, few studies have focused on the bed material deposition on walls, in cyclones, and return legs in fluidized bed combustion. Part of these bed material depositions originates from sticky fragments of alkali-rich silicates formed after crack formation in older quartz bed particles. The crack layer formation in quartz bed particles in fluidized bed combustion of woody biomass was therefore investigated by collecting bed material samples of different ages from full-scale bubbling and circulating fluidized bed facilities. Scanning electron microscopy/energy-dispersive spectroscopy was used to analyze the crack morphology and composition of the layer surrounding the cracks. For quartz bed particles with an age of some days, a crack in the quartz bed particle was observed in connection to the irregular interface between the inner layer and the core of the bed particle. The crack layer composition is similar for quartz particles with different ages and for samples taken from different fluidized bed techniques. Their composition is dominated by Si, K, Ca, and Na (except O). These crack layers become deeper, wider, and more common as bed particle age increases. The crack layers eventually connect with each other, and the whole quartz particle is transformed into smaller quartz cores surrounded by crack layers, which were observed in particles older than 1 week. From the characterization work, a crack formation process including three phases is proposed on the basis of the presumption that the initial crack layer formation resulted from the presence of induced cracks in the inner quartz bed particle layer. Fragmentation after the third phase is likely responsible for the formation of sticky alkali silicate deposit formation, and a weekly complete exchange of the bed is therefore recommended to avoid problematic deposits in combustion of woody-type biomass in fluidized bed combustion

  • 11.
    He, Hanbing
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Time-dependent layer formation on K-feldspar bed particles during fluidized bed combustion of woody fuels2017Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, nr 11, s. 12848-12856Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Despite frequent reports on layer characteristics on quartz bed particles, few studies have been found focusing on the layer characteristics on K-feldspar bed particles. The layer characteristics of K-feldspar bed particles in fluidized bed combustion of woody biomass was therefore investigated by collecting bed material samples of different ages from large-scale bubbling and circulating fluidized bed facilities. Scanning electron microscopy/energy-dispersive spectroscopy was used to analyze the layer morphology and elemental composition. For particles with an age of 1 day, a thin layer rich in Si, Ca and Al was found. For particles older than some days, an inner more homogenous layer containing cracks and an outer more particle-rich layer were observed. The outer layer was thinner for K-feldspar bed particles sampled from circulating fluidized bed, compared to particles from bubbling fluidized bed. The concentration of Ca in the inner layer increases towards bed particle surface, the molar ratio of Si/Al is maintained, and the molar ratio of K/Al decreases compared to the K-feldspar. The inner layer thickness for quartz and K-feldspar bed particles collected at the same operation conditions was found to be similar. No crack layers, as have been observed in quartz particles, were found in the core of the K-feldspar bed particles. The results suggest that the diffusion and reaction of Ca2+ into/with the feldspar particle play an important role on the inner layer formation process.

  • 12.
    Kuba, Matthias
    et al.
    TU Wien.
    He, Hanbing
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kirnbauer, Freidrich
    Bioenergy 2020+.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Boström, Dan
    Umeå University.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hoffbauer, Herman
    TU Wien.
    Mechanism of Layer Formation on Olivine Bed Particles in Industrial-Scale Dual Fluid Bed Gasification of Wood2016Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, nr 9, s. 7410-7418Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Utilization of biomass as feedstock in dual fluidized bed steam gasification is a promising technology for the substitution of fossil energy carriers. Experience from industrial-scale power plants showed an alteration of the olivine bed material due to interaction with biomass ash components. This change results mainly in the formation of Ca-rich layers on the bed particles. In this paper, a mechanism for layer formation is proposed and compared to the better understood mechanism for layer formation on quartz bed particles. Olivine bed material was sampled at an industrial-scale power plant before the start of operation and at predefined times after the operation had commenced. Therefore, time-dependent layer formation under industrial-scale conditions could be investigated. The proposed mechanism suggests that the interaction between wood biomass ash and olivine bed particles is based on a solid-solid substitution reaction, where Ca2+ is incorporated into the crystal structure. As a consequence, Fe2+/3+ and Mg2+ ions are expelled as oxides. This substitution results in the formation of cracks in the particle layer due to a volume expansion in the crystal structure once Ca2+ is incorporated. The results of this work are compared to relevant published results, including those related to quartz bed particles

  • 13.
    Kuba, Matthias
    et al.
    TU Wien, Institute of Chemical Engineering.
    He, Hanbing
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kirnbauer, Freidrich
    Bioenergy 2020+.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Boström, Dan
    Umeå University, Energy Technology and Thermal Process Chemistry.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hoffbauer, Herman
    TU Wien, Institute of Chemical Engineering.
    Thermal stability of bed particle layers on naturally occurring minerals from dual fluid bed gasification of woody biomass2016Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, nr 10, s. 8277-8285Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of biomass as feedstock for gasification is a promising way of producing not only electricity and heat but also fuels for transportation and synthetic chemicals. Dual fluid bed steam gasification has proven to be suitable for this purpose. Olivine is currently the most commonly used bed material in this process due to its good agglomeration performance and its catalytic effectiveness in the reduction of biomass tars. However, as olivine contains heavy metals such as nickel and chromium, no further usage of the nutrient-rich ash is possible, and additional operational costs arise due to necessary disposal of the ash fractions. This paper investigates possible alternative bed materials and their suitability for dual fluid bed gasification systems focusing on the behavior of the naturally occurring minerals olivine, quartz, and K-feldspar in terms of agglomeration and fracturing at typical temperatures. To this end, samples of bed materials with layer formation on their particles were collected at the industrial biomass combined heat and power (CHP) plant in Senden, Germany, which uses olivine as the bed material and woody biomass as feedstock. The low cost logging residue feedstock contains mineral impurities such as quartz and K-feldspar, which become mixed into the fluidized bed during operation. Using experimental and thermochemical analysis, it was found that the layers on olivine and K-feldspar showed a significantly lower agglomeration tendency than quartz. Significant fracturing of particles or their layers could be detected for olivine and quartz, whereas K-feldspar layers were characterized by a higher stability. High catalytic activity is predicted for all three minerals once Ca-rich particle layers are fully developed. However, quartz may be less active during the buildup of the layers due to lower amounts of Ca in the initial layer formation

  • 14.
    Kumpiene, Jurate
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Brännvall, Evelina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Wolters, Martin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Cirba, Stasys
    Department of Mathematical Modelling, Vilnius Gediminas Technical University.
    Aksamitauskas, Vladislovas Ceslovas
    Department of Geodesy and Cadastre, Vilnius Gediminas Technical University.
    Phosphorus and cadmium availability in soil fertilized with biosolids and ashes2016Ingår i: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 151, s. 124-132Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The recycling of hygienized municipal sewage sludge (biosolids) to soil as the source of phosphorus (P) is generally encouraged. The use of biosolids, however, has some concerns, such as the presence of elevated concentrations of potentially toxic trace elements, and the possible presence of pathogens, hormones and antibiotics. Organic substances are destroyed during combustion whereas trace elements could partly be separated from P in different ash fractions. Biomass combustion waste (ash) can instead be considered as an alternative P source. This study evaluates and compares the impact of biosolids and their combustion residues (ashes), when used as fertilizers, on P and Cd solubility in soil, plant growth and plant uptake of these elements. Biosolids were also amended with K and Ca to improve the composition and properties of P in ashes, and incinerated at either 800 °C or 950 °C. Combustion of biosolids improved the Cd/P ratio in ashes by 2-5 times, compared with the initial biosolids. The low Cd content in ashes (4-9 mg Cd (kg P)-1) makes this material a particularly attractive alternative to mineral fertilizers. Significantly higher pore water P (as well as total N) was measured in soils containing biosolids, but plants produced a higher biomass in soil fertilized with ashes. The K and Ca amendments prior to biosolids combustion generally decreased the total Cd in ash, but had little effect on P and Cd uptake and biomass growth. Similarly, the combustion temperature had negligible effect on these factors as well

  • 15.
    Marie, Rönnbäck
    et al.
    SP.
    Gustavsson, Lennart
    SP.
    Hermansson, Sven
    SP.
    Skoglund, Nils
    Umeå universitet.
    Fagerström, Jonathan
    Umeå universitet.
    Boman, Christoffer
    Umeå universitet.
    Backman, Rainer
    Umeå universitet.
    Näzelius, Ida-Linn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Grimm, Alejandro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Förbränningskaraktärisering och förbränningsteknisk utvärdering av olika pelletbränslen (FUP): Syntes2011Rapport (Övrigt vetenskapligt)
  • 16.
    Piotrowska, Patricia
    et al.
    Åbo Akademi.
    Grimm, Alejandro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Skoglund, Nils
    Umeå universitet.
    Boman, Christoffer
    Umeå universitet.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Zevenhoven, Maria
    Åbo Akademi.
    Boström, Dan
    Umeå universitet.
    Hupa, Mikko
    Åbo Akademi.
    Systematic studies on defluidization temperatures of rapeseed cake and bark mixtures2011Konferensbidrag (Övrigt vetenskapligt)
  • 17.
    Piotrowska, Patrycja
    et al.
    Åbo Akademi.
    Grimm, Alejandro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Skoglund, Nils
    Energy Technology and Thermal Process Chemistry, Umeå University.
    Boman, Christoffer
    Energy Technology and Thermal Process Chemistry, Umeå University.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Zevenhoven, Maria
    Åbo Akademi.
    Boström, Dan
    Energy Technology and Thermal Process Chemistry, Umeå University.
    Hupa, Mikko
    Åbo Akademi.
    Fluidized bed combustion of mixtures of rapeseed cake and bark: the resulting bed agglomeration characteristics2012Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 26, nr 4, s. 2028-2037Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The bed agglomeration characteristics resulting from the combustion of 11 mixtures of rapeseed cake and spruce bark were studied in a bench-scale bubbling fluidized-bed reactor (5 kW). The objective was to determine the defluidization temperatures and the prevailing bed agglomeration mechanism as functions of the fuel mixture. Controlled fluidized-bed agglomeration tests were performed for each mixture with quartz sand as the bed material. The total defluidization temperatures and the initial defluidization temperatures were determined based on the measured pressure and temperature profiles in the bed. After combustion, bottom ash samples, agglomerates, and fly ash samples were analyzed by means of scanning electron microscope combined with energy dispersive X-ray detector (SEM-EDX). The composition of the ash-forming matter produced by the combustion of rapeseed cake is significantly different from that produced by the combustion of bark, resulting in different bed agglomeration tendencies. Bark contains ash-forming matter dominated by calcium, with some silicon and potassium, whereas rapeseed cake is rich in phosphorus, potassium, and sodium. The total defluidization temperature for pure bark was above 1045 °C, whereas, for rapeseed cake, defluidization occurred during combustion (800 °C). During the combustion of bark, the formation of a potassium-rich layer on the silica-bed grains was found to be a crucial for the formation of agglomerates. The low defluidization temperature for the rapeseed cake can be attributed to the formation of sticky ash, which is dominated by phosphates. Two main phosphate forms were observed in the neck between the silica grains: calcium–potassium/sodium phosphates, and magnesium–potassium phosphates. As the proportion of bark increased, the Ca/P ratio increased in the fuel mixture, and the formation of high-temperature melting phosphates in the ash was favored. However, the addition of bark also favored the formation of a potassium-rich layer on the silica bed material, leading to the coexistence of both bed agglomeration mechanisms. In the present work, mixtures with a minimum of 60 wt % bark resulted in significantly increased defluidization temperatures and reduced bed agglomeration tendencies, compared to what occurs in rapeseed cake monocombustion.

  • 18.
    Piotrowska, Patrycja
    et al.
    Åbo Academy.
    Skoglund, Nils
    Umeå university.
    Grimm, Alejandro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Boman, Christoffer
    Umeå university.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Zevenhoven, Maria
    Åbo Academy.
    Boström, Dan
    Umeå university.
    Hupa, Mikko
    Åbo Academy.
    Systematic studies of ash composition during the co-combustion of rapeseed cake and bark2012Ingår i: Proceedings of the 21st International Conference on Fluidized Bed Combustion, 2012, s. 219-226Konferensbidrag (Refereegranskat)
  • 19.
    Qu, Zhechao
    et al.
    Thermochemical Energy Conversion Laboratory (TEC-Lab), Department of Applied Physics and Electronics, Umeå University.
    Holmgren, Per
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wagner, David R.
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Broström, Markus
    Thermochemical Energy Conversion Laboratory (TEC-Lab), Department of Applied Physics and Electronics, Umeå University.
    Schmidt, Florian M.
    Umeå University, Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics.
    Distribution of temperature, H2O and atomic potassium during entrained flow biomass combustion: Coupling in situ TDLAS with modeling approaches and ash chemistry2018Ingår i: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 188, s. 488-497Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tunable diode laser absorption spectroscopy (TDLAS) is employed for simultaneous detection of gas temperature, water vapor (H2O) and gas-phase atomic potassium, K(g), in an atmospheric, research-scale entrained flow reactor (EFR). In situ measurements are conducted at four different locations in the EFR core to study the progress of thermochemical conversion of softwood and Miscanthus powders with focus on the primary potassium reactions. In an initial validation step during propane flame operation, the measured axial EFR profiles of H2O density-weighted, path-averaged temperature, path-averaged H2O concentration and H2O column density are found in good agreement with 2D CFD simulations and standard flue gas analysis. During biomass conversion, temperature and H2O are significantly higher than for the propane flame, up to 1500 K and 9%, respectively, and K(g) concentrations between 0.2 and 270 ppbv are observed. Despite the large difference in initial potassium content between the fuels, the K(g) concentrations obtained at each EFR location are comparable, which highlights the importance of considering all major ash-forming elements in the fuel matrix. For both fuels, temperature and K(g) decrease with residence time, and in the lower part of the EFR, K(g) is in excellent agreement with thermodynamic equilibrium calculations evaluated at the TDLAS-measured temperatures and H2O concentrations. However, in the upper part of the EFR, where the measured H2O suggested a global equivalence ratio smaller than unity, K(g) is far below the predicted equilibrium values. This indicates that, in contrast to the organic compounds, potassium species rapidly undergo primary ash transformation reactions even if the fuel particles reside in an oxygen-deficient environment

  • 20.
    Rebbling, Anders
    et al.
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Näzelius, Ida-linn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Piotrowska, Patrycja
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Boman, Christoffer
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Boström, Dan
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Waste Gypsum Board and Ash-Related Problems during Combustion of Biomass: 2. Fixed Bed2016Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, nr 12, s. 10705-10713Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper is the second of two describing the use of shredded waste gypsum board (SWGB) as an additive during combustion of biomass. The focus of this paper is to determine whether SWGB can be used as a fuel additive providing CaO and SO2/SO3 for mitigation of ash-related operational problems during combustion of biomass and waste derived fuels in grate fired fixed bed applications. The former study in this series was performed in a fluidized bed and thus allow for comparison of results. Gypsum may decompose at elevated temperatures and forms solid CaO and gaseous SO2/SO3 which have been shown to reduce problems with slagging on the fixed bed and alkali chloride deposit formation. Three different biomasses, spruce bark (SB), reed canary grass (RG), and wheat straw (WS), were combusted with and without addition of SWGB in a residential pellet burner (20 kWth). Waste derived fuel with and without the addition of SWGB was combusted in a large scale grate-fired boiler (25 MWth). The amount of added SWGB varied between 1 and 4 wt %. Ash, slag, and particulate matter (PM) were sampled and subsequently analyzed with scanning electron microscopy/ energy dispersive spectroscopy and X-ray diffraction. Decomposition of CaSO4 originating from SWGB was observed as elevated SO2 emissions in both the large scale and small scale facilities and significantly higher than was observed in the fluidized bed study. Slag formation was significantly reduced due to formation of calcium-silicates in small scale application, but no conclusive observations regarding calcium reactivity could be made in the large scale application. In the small scale study the formation of K2SO4 was favored over KCl in PM, while in the large scale study K3Na(SO4)2 and K2Zn2(SO4)3 increased. It is concluded that SWGB can be used as a source of CaO and SO2/SO3 to mitigate slag formation on the grate and chloride-induced high temperature corrosion and that fixed bed applications are likely more suitable than bubbling fluidized beds when using SWGB as an additive.

  • 21.
    Reyes, Diana Carolina Albán
    et al.
    Department of Chemistry, Umeå University.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Svedberg, Anna
    Domsjö Fabriker AB.
    Eliasson, Bertil
    Department of Chemistry, Umeå University.
    Sundman, Ola
    Department of Chemistry, Umeå University.
    The influence of different parameters on the mercerisation of cellulose for viscose production2016Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, nr 2, s. 1061-1072Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A quantitative analysis of degree of transformation from a softwood sulphite dissolving pulp to alkalised material and the yield of this transformation as a function of the simultaneous variation of the NaOH concentration, denoted [NaOH], reaction time and temperature was performed. Samples were analysed with Raman spectroscopy in combination with multivariate data analysis and these results were confirmed by X-ray diffraction. Gravimetry was used to measure the yield. The resulting data were related to the processing conditions in a Partial Least Square regression model, which made it possible to explore the relevance of the three studied variables on the responses. The detailed predictions for the interactive effects of the measured parameters made it possible to determine optimal conditions for both yield and degree of transformation in viscose manufacturing. The yield was positively correlated to the temperature from room temperature up to 45 °C, after which the relation was negative. Temperature was found to be important for the degree of transformation and yield. The time to reach a certain degree of transformation (i.e. mercerisation) depended on both temperature and [NaOH]. At low temperatures and high [NaOH], mercerisation was instantaneous. It was concluded that the size of fibre particles (mesh range 0.25–1 mm) had no influence on degree of transformation in viscose processing conditions, apparently due to the quick reaction with the excess of NaOH.

  • 22.
    Skoglund, Nils
    et al.
    Energy Technology and Thermal Process Chemistry, Umeå University.
    Boström, Dan
    Energy Technology and Thermal Process Chemistry, Umeå University.
    Brännvall, Evelina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Kumpiene, Jurate
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Grimm, Alejandro
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Återvinning av fosfor och energi ur avloppsslam genom termisk behandling i fluidiserad bädd; Slutrapport NWI Dp 4, Januari 20132013Rapport (Övrigt vetenskapligt)
  • 23.
    Skoglund, Nils
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bäfver, Linda
    SP Sveriges Tekniska Forskningsinstitut, SP Energiteknik, Pöyry SwedPower AB.
    Fahlström, Johan
    Rang-Sells Miljökonsult AB.
    Holmén, Erik
    ENA Energy AB.
    Renström, Caroline
    Pöyry SwedPower AB.
    Fuel design in co-combustion of demolition wood chips and municipal sewage sludge2016Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 141, nr 2, s. 196-201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Municipal sewage sludge (MSS) is a waste stream resource which contains both energy and elements such as phosphorus which could be recycled. If these two aspects of this waste stream resource are to be used to their full potential the sludge should not be used in landfills or road construction. There is some use of sludge in agriculture today but not all MSS produced is suitable for direct use on arable land due to its content of potentially harmful elements, pathogens or anthropogenic chemicals. By combusting sludge that is not used directly in agriculture the problematic organic content could be destroyed. The combustion process also produces an ash that possibly could be used either directly in agriculture or as a raw material for recovering phosphorus and energy could be recovered. Building mono-combustion plants for sewage sludge is not economically feasible in all parts of the world so it is of interest to investigate how MSS can be introduced together with other fuels in existing infrastructure which already have extensive cleaning systems for potentially harmful elements.To investigate this possible path, demolition wood chips (DWC) were co-combusted with municipal sewage sludge (MSS) in a grate-fired combined heat and power plant running at 50% capacity producing 25 MWth and 9 MWel. The amount of MSS that was suitable to introduce in blends was determined using a “fuel fingerprint” based on the composition of the raw materials. Thermodynamic equilibrium calculations were made to evaluate potential problems with slagging based on the ash content prior to the combustion experiments. The fuels were introduced as a reference case with only demolition wood and pre-blended fuel mixtures in two ratios; 65 w/w-% DWC/35 w/w-% MSS and 55 w/w-% DWC/45 w/w-% MSS and were fired for 12 h. The high water content of the MSS affected how much MSS that could be introduced without compromising the heat and power production.The fuel blends worked nicely for 12 h of continuous combustion with small adjustments where the primarily the air inlet configuration was changed. The main problems encountered related to cleaning of the flue gases and to some extent ash removal. The bed ash and fly ash produced was analysed both using ICP-AES (elemental) and XRD (speciation) and the bottom ash was subjected to ash melting tests. The major nutrient phosphorus was mainly found in bottom ash (80 w/w-%) as whitlockites with some hydroxyapatite whereas fly ash (20 w/w-%) contained larger amounts of hydroxyapatite, especially for the reference fuel. The amount of alkali chloride in the fly ash was reduced in favour of alkali sulphate formation.

  • 24.
    Skoglund, Nils
    et al.
    Umeå universitet.
    Grimm, Alejandro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Återvinning av fosfor och energi ur avloppsslam genom termisk behandling i fluidiserad bädd – Utvärdering och optimering av prestanda för slutprodukten2012Rapport (Övrigt vetenskapligt)
  • 25.
    Skoglund, Nils
    et al.
    Umeå universitet.
    Grimm, Alejandro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Boström, Dan
    Umeå universitet.
    Effects on ash chemistry when co-firing municipal sewage sludge and wheat straw in a fluidised bed: influence on the ash chemistry by fuel mixing2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Municipal sewage sludge (MSS) is of interest for co-combustion with problematic fuels, such as agricultural residues, due to its high content of inorganic elements which may improve combustion properties of such problematic fuels. Ash transformation when co-combusting MSS with the agricultural residue wheat straw was examined using a bench-scale bubbling fluidised bed (5 kW). Wheat straw pellets were combusted with MSS both in a co-pelletized form and co-firing of separate fuel particles. This was done to examine whether there is any advantage to either approach of introducing MSS together with a problematic fuel.Co-combusting wheat straw with MSS changed the bed agglomeration characteristics from being caused by the formation of low-temperature melting potassium silicates in the fuel ash to being caused by a higher-temperature melting bed ash. This shift in ash chemistry had a significant positive effect on the initial defluidisation temperature. The cyclone ash and fine particulate matter changed from being dominated by alkali in general and alkali chlorides in specific to an increased phosphate and sulphate formation which reduces the risk of alkali-related fouling and corrosion. The influence of aluminosilicates may also play a role in the improvement of fuel ash behaviour.

  • 26.
    Skoglund, Nils
    et al.
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Grimm, Alejandro
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Boström, Dan
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Effects on ash chemistry when co-firing municipal sewage sludge and wheat straw in a fluidized bed: influence on the ash chemistry by fuel mixing2013Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, nr 10, s. 5725-5732Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Municipal sewage sludge (MSS) is of interest for co-combustion with problematic fuels, such as agricultural residues, because of its high content of inorganic elements, which may improve combustion properties of such problematic fuels. Ash transformation when co-combusting MSS with the agricultural residue wheat straw was examined using a bench-scale bubbling fluidized bed (5 kW). Wheat straw pellets were combusted with MSS in both a co-pelletized form and co-firing of separate fuel particles. This was performed to examine whether there is any advantage to either approach of introducing MSS together with a problematic fuel. Co-combusting wheat straw with MSS changed the bed agglomeration characteristics from being caused by the formation of low-temperature melting potassium silicates in the fuel ash to being caused by a higher temperature melting bed ash. This shift in ash chemistry had a significant positive effect on the initial defluidization temperature. The cyclone ash and fine particulate matter changed from being dominated by alkali in general and alkali chlorides in specific to an increased phosphate and sulfate formation, which reduces the risk of alkali-related fouling and corrosion. The influence of aluminosilicates may also play a role in the improvement of fuel ash behavior.

  • 27.
    Skoglund, Nils
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Werner, Kajsa
    Thermochemical Energy Conversion Laboratory (TEC-Lab), Department of Applied Physics and Electronics, Umeå University.
    Nylund, Göran M.
    Department of Marine Sciences - Tjärnö, University of Gothenburg.
    Pavia, Henrik
    Department of Marine Sciences - Tjärnö, University of Gothenburg.
    Albers, Eva
    Division Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology.
    Broström, Markus
    Thermochemical Energy Conversion Laboratory (TEC-Lab), Department of Applied Physics and Electronics, Umeå University.
    Combustion of seaweed: A fuel design strategy2017Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 165, s. 155-161Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The high ash content and varying ash composition in algal biomass is often mentioned as problematic if to be used for thermal energy conversion. This paper suggests an approach where detailed information on ash composition and predicted ash formation reactions are basis for successful remedies enabling the use of fuels considered to be difficult. The procedure is demonstrated on seaweed (Saccharina latissima) cultivated for biorefinery purposes. The ash composition of the seaweed was found suitable for co-combustion with Miscanthus x giganteus, an energy crop high in alkali and silicon. Fuel mixtures were combusted in a bubbling fluidized bed reactor and ash samples were analyzed by SEM-EDS and XRD. The results showed that Ca from the seaweed was very reactive and thus efficient in solving the silicate melting problems. The fuel design approach was proven successful and the potential for using otherwise difficult seaweed fuels in synergetic co-combustion was demonstrated.

  • 28.
    Skoglund, Nils
    et al.
    Umeå universitet.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Återvinning av fosfor genom förbränning av rötslam2012Ingår i: Svenskt Vatten, ISSN 1651-0674, Vol. 2012, nr 6, s. 26-26Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 29.
    Skoglund, Nils
    et al.
    Umea University, Applied Physics & Electronics.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Boström, Dan
    Umeå University, Energy Technology and Thermal Process Chemistry.
    Ash transformation reactions for phosphorus-rich biomass and waste streams2017Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 254, artikel-id 25Artikel i tidskrift (Refereegranskat)
  • 30.
    Skoglund, Nils
    et al.
    Umeå University. Department of Applied Physics and Electronics.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Grimm, Alejandro
    Boström, Dan
    Umeå University. Department of Applied Physics and Electronics.
    Combustion of Biosolids in a Bubbling Fluidized Bed: Part I: Main Ash Forming Elements and Ash Distribution with a Focus on Phosphorus2014Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 28, nr 2, s. 1183-1190Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This is the first in a series of three papers describing combustion of biosolids in a 5-kW bubbling fluidized bed, the ash chemistry, and possible application of the ash produced as a fertilizing agent. This part of the study aims to clarify whether the distribution of main ash forming elements from biosolids can be changed by modifying the fuel matrix, the crystalline compounds of which can be identified in the raw materials and what role the total composition may play for which compounds are formed during combustion. The biosolids were subjected to low-temperature ashing to investigate which crystalline compounds that were present in the raw materials. Combustion experiments of two different types of biosolids were conducted in a 5-kW benchscale bubbling fluidized bed at two different bed temperatures and with two different additives. The additives were chosen to investigate whether the addition of alkali (K2CO3) and alkaline-earth metal (CaCO3) would affect the speciation of phosphorus, so the molar ratios targeted in modified fuels were P:K = 1:1 and P:K:Ca = 1:1:1, respectively. After combustion the ash fractions were collected, the ash distribution was determined and the ash fractions were analyzed with regards to elemental composition (ICP-AES and SEM-EDS) and part of the bed ash was also analyzed qualitatively using XRD. There was no evidence of zeolites in the unmodified fuels, based on low-temperature ashing. During combustion, the biosolid pellets formed large bed ash particles, ash pellets, which contained most of the total ash content (54%–95% (w/w)). This ash fraction contained most of the phosphorus found in the ash and the only phosphate that was identified was a whitlockite, Ca9(K,Mg,Fe)(PO4)7, for all fuels and fuel mixtures. With the addition of potassium, cristobalite (SiO2) could no longer be identified via X-ray diffraction (XRD) in the bed ash particles and leucite (KAlSi2O6) was formed. Most of the alkaline-earth metals calcium and magnesium were also found in the bed ash. Both the formation of aluminum-containing alkali silicates and inclusion of calcium and magnesium in bed ash could assist in preventing bed agglomeration during co-combustion of biosolids with other renewable fuels in a full-scale bubbling fluidized bed.

  • 31.
    Wagner, David R.
    et al.
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Holmgren, Per
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. 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.
    Design and validation of an advanced entrained flow reactor system for studies of rapid solid biomass fuel particle conversion and ash formation reactions2018Ingår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, nr 6, artikel-id 065101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The design and validation of a newly commissioned entrained flow reactor is described in the present paper. The reactor was designed for advanced studies of fuel conversion and ash formation in powder flames, and the capabilities of the reactor were experimentally validated using two different solid biomass fuels. The drop tube geometry was equipped with a flat flame burner to heat and support the powder flame, optical access ports, a particle image velocimetry (PIV) system for in situ conversion monitoring, and probes for extraction of gases and particulate matter. A detailed description of the system is provided based on simulations and measurements, establishing the detailed temperature distribution and gas flow profiles. Mass balance closures of approximately 98% were achieved by combining gas analysis and particle extraction. Biomass fuel particles were successfully tracked using shadow imaging PIV, and the resulting data were used to determine the size, shape, velocity, and residence time of converting particles. Successful extractive sampling of coarse and fine particles during combustion while retaining their morphology was demonstrated, and it opens up for detailed time resolved studies of rapid ash transformation reactions; in the validation experiments, clear and systematic fractionation trends for K, Cl, S, and Si were observed for the two fuels tested. The combination of in situ access, accurate residence time estimations, and precise particle sampling for subsequent chemical analysis allows for a wide range of future studies, with implications and possibilities discussed in the paper.

  • 32.
    Wagner, Katharina
    et al.
    Bioenergy 2020+ GmbH.
    Kuba, Mathias
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Bioenergy 2020+ GmbH.
    Häggström, Gustav
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    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.
    Hofbauer, Hermann
    Institute of Chemical, Environmental & Bioscience Engineering, TU Wien.
    Influence of phosphorus on the layer formation on k-feldspar during fluidized bed combustion and gasification2018Ingår i: European biomass conference and exhibition proceedings, E-ISSN 2282-5819, Vol. 26thEUBCE, s. 486-492Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Today, mainly wood-based feedstocks are used in thermo-chemical biomass conversion since they have a comparably high heating value and contain a small amount of ash. Fluidized beds allow a greater variety of fuels to be used, since they are rather flexible regarding their fuel input. The use of biogenic waste streams (chicken manure, horse manure, etc.) and sewage sludge would not only increase the fuel diversity in fluidized beds but might also enhance the usability of side products. The contained essential nutrients like phosphorus, potassium, calcium, etc. in these fuels are enriched in the ash after thermochemical conversion. Thus, in the near future it may be possible to apply this ash as secondary resource for fertilizer. Especially the recovery of phosphorus is of importance due to the imminent phosphorus scarcity. Due to its tendency to react with ash forming elements in fuels, phosphorus influences the ash chemistry severely. Especially the agglomeration and layer formation on bed materials during biomass combustion and gasification is highly dependent on the predominant ash forming elements. Phosphorus therefore has a significant impact on those mechanisms. Until now, the behavior of phosphorus-rich fuels in fluidized beds has not been studied in much detail. To develop a basic understanding of the behavior, phosphorus-rich feedstock was combusted in a bench-scale fluidized bed reactor. Ash layers on bed particles, which were formed during these experiments, were studied and compared to results with phosphorus-lean fuels. Furthermore, layer formation of phosphorus-rich and phosphorus-lean fuels from dual fluid bed gasification were compared to those from fluidized bed combustion. The studied layers on bed materials showed significant amounts of phosphorus. The data also indicates a change in layer formation as soon as phosphorus is present. An increased catalytic activity due ash-layer formation was observed for both phosphorus-rich and phosphorus-lean feedstock, independent from the presence of phosphorus in the ash layer

  • 33.
    Öhman, Marcus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Boström, Dan
    Umeå universitet.
    Skoglund, Nils
    Umeå universitet.
    Grimm, Alejandro
    Boman, Christoffer
    Umeå universitet.
    Kofod-Hansen, Marie
    Torvforsk.
    Minskade askrelaterade driftsproblem genom inblandning av torv i åkerbränslen2010Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Torvbränslen används ofta i kombination med trädbränslen i värme- och kraftvärmeverk. Den kombinationen har visat sig ge förbränningstekniska fördelar kanske främst minskad risk för askrelaterade driftsproblem. Erfarenheter saknas dock vad gäller eventuella positiva sameldningseffekter/erfoderliga inblandningsgrader av torv i många kommande åkerbränslen såsom salix, rörflen och halm. Projektets mål har därför varit att: i) bestämma vilka typiska inblandningsgrader av torv i olika åkerbränslen (halm, salix och rörflen) som krävs för att uppnå positiva effekter m a p slaggning, beläggningsbildning/(högtemperaturkorrosion) och bäddagglomerering, samt ii) demonstrera möjligheterna att minska uppkomsten av askrelaterade driftsproblem i förbränningsanläggningar genom inblandning av torv till intressanta åkerbränslen. Termokemiska modellberäkningar utfördes för att bestämma effekter av torvinblandning till halm, salix och rörflen med hög och låg askhalt på reduktionen av slaggnings-, beläggningsbildnings-/(korrosion)- och bäddagglomereringsrisken vid förbränning. Dessa resultat och tidigare utförda försök i bänkskala låg sedan till grund för valda bränslekombinationer, torvinblandningsgrader och torvprov i de sedan utförda demonstrationsförsöken. Dessa demonstrationsförsök utfördes i en rosteranläggning på 4 MW (rörflen/rörflensmixar och salix/salixmixar) och i en pelletsbrännare/-panna i bänkskala (20 kW) (halm/halmmixar). Resultaten visar att inblandning av typisk starrbaserad bränntorv i salix och rörflen med låg askhalt ger positiva effekter vad avser bäddagglomerering och beläggningsbildning/(korrosion) i pannors konvektionsdelar redan vid relativt låga inblandningsgrader (15 vikts-% på TS basis). En starrbaserad bränntorv med relativt högt Ca/Si förhållande bör väljas för sameldning med salix i rosteranläggningar för att inte öka slaggningsrisken. Samma torvtyp kan också i rosteranläggningar nyttjas i sameldning med rörflen med låg askhalt (relativt låga inblandningsgrader räcker d v s 15 vikts-% på TS basis) och vetehalm (höga inblandningsgrader krävs d v s upp mot 40 vikts-% på TS basis) för att reducera slaggningsrisken. Vid val av torvslag för att maximera de ovanstående positiva effekterna vid förbränning kan därför en allmän rekommendation göras att torvar med hög askhalt (starrinnehållande torv), och gärna med högt inslag av svavel, ger de bästa sameldningsegenskaperna med det tilläget att vid rostereldning bör en torv med relativt högt Ca/Si förhållande väljas (gärna upp mot 1 på vikts-% basis). Rörflen med hög askhalt förväntas inte ge upphov till några större problem med beläggnings- och slaggnings-/bäddagglomereringsproblem och är därför i första hand inte intressant att samelda med torv utifrån ett askrelaterat driftsproblemperspektiv. För att reducera beläggningstendensen till låga nivåer vid sameldning med vetehalm krävs troligen så höga nivåer att detta inte är praktiskt intressant.

  • 34.
    Örberg, Håkan
    et al.
    Sveriges Lantbruksuniversitet.
    Skoglund, Nils
    Umeå universitet.
    Grimm, Alejandro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Teknikutveckling för ökad etablering och nyttjande av rörflen: demonstrationsförsök i fullskala2010Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Resultaten visar att energigräset rörflen kan utgöra ett kompletterande bränsle till det skogsbränsle och den torv som idag används i svenska värme- och kraftvärmeanläggningar. En inblandning av rörflen med ca 10 % på energibasis i en bränslemix som för övrigt består av 10-20 % carextorv och 70-80 % träbränsle har i demonstrationsförsök visat goda resultat. Denna bränslemix har vid fullskaliga förbränningsförsök i fluidiserande bädd (Hedensbyn,CFB 98 MW) under sammanlagt 4 dygn inte gett upphov till störningar eller negativa effekter på utrustning eller ökade utsläpp i rökgaserna i form av partiklar eller gasformiga emissioner. Vid simulerade påverkan på överhettare i form av kylda sonder har även konstaterats att beläggningstillväxten varit oförändrad och ej givit upphov till ökad korrosion. Inblandning i bränslemixen har skett med hackad rörflen (40-50 mm) i torvdelen för att en jämn inblandning kunde åstadkommas. Rörflensmaterialet har levererats i samband med skörden så att det hackats direkt på fältet med exakthack kopplad till vagn eller med containerhantering. Vid leverans under vår och försommar har rörflenen hållit mycket låg fukthalt med ett medel på 11,3 % fukt. Jämförande studier har gjorts med system där rörflen vid skörden under vår pressats till storbalar för vidare transport till terminal eller gårdscentrum. Detta system har visat sig mindre effektivt jämfört med direkthackning på fältet och transport av hackat material till värmeverk. En fördel med storbalssystemet är dock att det möjliggör mer kostnadseffektiv lagring utan att t.ex. fukthalten höjs under lagringstiden. Även vägtransport från terminal eller gårdscentrum till värmeverk har visat sig mer effektivt med storbalar jämfört med hackat material. Vid lastning av stora fyrkantsbalar (90x120x220 cm) på lastbil med släp uppnåddes i stort sett dubbla lastvikten jämfört med hackad rörflen (20,9 ton jmf. m. 11,0 ton). För de något mindre anläggningarna av typen rosterpannor som provats (0,6 och 4 MW) har den briketterade formen av rörflen använts för att uppnå en jämn och koncentrerad bränslematning. Även här har en blandning av rörflen och torv visat sig användbar och speciellt för rörflen med låg askhalt har torvinblandning på 15 vikts-% av gett minskad tendens till sintring av askan. Rörflen med hög askhalt (utan torvinblandning) har kunnat sameldas med träbränsle utan risk för sintrad aska i dessa anläggningar. Tillverkningen av briketter för försöken, sammanlagt ca 35 ton, varav hälften med inblandning av torv har genomförts utan störningar och med bra kvalité på briketterna.

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