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  • 1.
    Albán Reyes, Diana Carolina
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden .
    Svedberg, Anna
    Eliasson, Bertil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sundman, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    The influence of different parameters on the mercerisation of cellulose for viscose production2016Ingår i: Cellulose, 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 A degrees 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.

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  • 2.
    Almqvist, Jonna
    et al.
    SP Processum.
    Westin, Gunnar
    SP Processum.
    Öberg, Christian
    Umeå universitet.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Luleå University of Technology, Department of Department of Engineering Sciences and Mathematics, Energy Science.
    Samförbränning av bioslam från massaindustrin i bubblande fluidiserad bädd2016Rapport (Övrig (populärvetenskap, debatt, mm))
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  • 3.
    Boman, Christoffer
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Schmidt, Florian M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Ash transformation chemistry in biomass fixed beds with focus on slagging and aerosols: 20 years of research and new developments2017Ingår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 254Artikel i tidskrift (Övrigt vetenskapligt)
  • 4.
    Borén, Eleonora
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Department of Water Supply, Sanitation and Environmental Engineering, IHE Delft Institute for Water Education, Delft, The Netherlands.
    Lindgren, Robert
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Carlborg, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Kaolin as fuel additive in grate combustion of biomass to mitigate ash related problems and particle emissions2022Ingår i: Proceedings of the 28th International Conference on the Impact of Fuel Quality on Power Production and the Environment / [ed] Markus Broström, Department of Applied Physics and Electronics, Umeå University , 2022Konferensbidrag (Refereegranskat)
    Abstract [en]

    Bioenergy is a fundamental part in sustainable development but use of novel fuel feedstocks potentiallymore sustainable may also bring associated ash-related challenges in practical operation that could bemitigated by co-conversion or additives. Kaolin, a clay mineral, is an additive known to be beneficialfor reduction of slagging tendencies and particulate matter formation in combustion of traditionalwoody-type biomass but its impact on thermal conversion of other biomasses still warrantsinvestigation. The aim of the present work is therefore to investigate how thermal conversion of atypical K-Ca-rich woody-type biomass, poplar, and a K-Si-rich annual crop, grass, is affected by kaolinaddition in fixed bed combustion. Additivation levels were calculated according to amount of alkaliintroduced with the two feedstocks, and incorporated by co-pelletization, in the case of poplar, anadditional blending d method was tested, by powder coating of pellets The results show that kaolinaddition improved the bottom ash characteristics, especially for grass, but the main differencesbetween feedstocks were found in particulate matter and flue gas composition. The particulate matterconcentrations were reduced with kaolin addition due to removal of gaseous K compounds which inturn caused higher SOx and HCl concentrations due to the lower amount of gaseous alkali for reaction.Further, initially high CO levels observed for both fuel feedstocks were reduced with the addition ofkaolin where co-pelletization with poplar proved more effective than powder coating the fuel particlesurfaces. This suggests that high concentrations of gaseous K-compounds may impact conversion ofthe carbonaceous matrix negatively.

  • 5.
    Boström, Dan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Grimm, Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Ash transformation chemistry during energy conversion of biomass2010Ingår i: Impacts of Fuel Quality on Power Production & Environment: 29/08/2010 - 03/09/2010, Impacts of Fuel Quality , 2010Konferensbidrag (Refereegranskat)
    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.

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  • 6.
    Boström, Dan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Ash transformation chemistry during combustion of biomass, theory and technical applications2017Ingår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 254Artikel i tidskrift (Övrigt vetenskapligt)
  • 7.
    Boström, Dan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Grimm, Alejandro
    Luleå Univ Technol, Div Energy Sci, SE-97187 Luleå, Sweden.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Luleå Univ Technol, Div Energy Sci, SE-97187 Luleå, Sweden.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    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.

  • 8.
    Bozaghian Bäckman, Marjan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Rebbling, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Kuba, Matthias
    BEST Bioenergy and Sustainable Technologies GmbH, Graz, Austria; Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria.
    Larsson, Sylvia H.
    Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Energy Engineering, Division of Energy Science, Luleå University of Technology, SE-971 87 Luleå, Sweden.
    Bed material performance of quartz, natural K-feldspar, and olivine in bubbling fluidized bed combustion of barley straw2024Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 364, artikel-id 130788Artikel i tidskrift (Refereegranskat)
    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.

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  • 9.
    Bozaghian Bäckman, Marjan
    et al.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology, Ume.
    Strandberg, Anna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    De La Fuente, Teresa
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology, Umeå, Sweden.
    Karjalainen, Mikko
    Luke Natural Resources Institute Finland, Kokkola, Finland.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Thyrel, Mikael
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology, Umeå, Sweden.
    Bergström, Dan
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology, Umeå, Sweden.
    Larsson, Sylvia H.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology, Umeå, Sweden.
    Does mechanical screening improve fuel properties?: Effects of mechanical screening of stored logging residue chips on ash chemistry and other parameters relevant for combustion2019Konferensbidrag (Refereegranskat)
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    poster
  • 10. Bozaghian, Marjan
    et al.
    Rebbling, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Larsson, Sylvia H.
    Thyrel, Mikael
    Xiong, Shaojun
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering, S-971 87 Luleå, Sweden.
    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 degrees 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 de fluidization 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.

  • 11.
    Bozaghian, Marjan
    et al.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Rebbling, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Larsson, Sylvia H.
    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
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Combustion characteristics of barley straw stored with CaCO3 using olivine and quartz as bed materials in fluidized bed combustion2017Konferensbidrag (Övrigt vetenskapligt)
  • 12.
    Bozaghian, Marjan
    et al.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Rebbling, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Larsson, Sylvia H.
    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
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Combustion characteristics of barley straw stored with CaCO3 using quartz and olivine as bed materials in fluidized-bed combustion2017Konferensbidrag (Övrigt vetenskapligt)
  • 13.
    Brännvall, Evelina
    et al.
    Luleå Tekniska Universitet.
    Nilsson, Malin
    Luleå Tekniska Universitet.
    Sjöblom, Rolf
    Luleå Tekniska Universitet.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Kumpiene, Jurate
    Luleå Tekniska Universitet.
    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 (3534 mg/l), Mg (184 mg/l), P (1.8 mg/l), S (760 mg/l), Cu (0.39 mg/l) and Zn (0.58 mg/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 (82 g/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.

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  • 14.
    Bäfver, Linda
    et al.
    Pöyry SwedPower.
    Renström, Caroline
    Pöyry SwedPower.
    Fahlström, Johan
    Ragn-Sells.
    Enfält, Patrik
    EasyMining Sweden.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Holmén, Erik
    ENA Energi.
    Slambränsleblandningar: Förbränning och fosforutvinning2013Rapport (Övrigt vetenskapligt)
    Abstract [en]

    For sustainable phosphorus recycling, the phosphorus in sewage sludge needs to be recovered, as it is a major phosphorus-source. However, all sludge is not suitable for direct recycling on agricultural land, e.g. when the content of heavy metals is too high. To achieve an increased recycling of phosphorus from sewage sludge there is a need of research and development of alternative methods to return the phosphorus from sewage sludge to agricultural land.

    The aim of the project is to show that sewage sludge can be co-combusted with demolition wood in existing boilers, and that the ash can be processed for extraction of phosphorus, together with valuable by-products from the process. Further effects of the project will be the development of new knowledge about combustion with a high sludge to demolition wood ratio in a grate boiler (up to 45 % sludge with respect to wet mixture), which has not been studied in full-scale combustion earlier. The project's goal is to demonstrate mixing and combustion of fuel mixtures of sludge and demolition wood, and subsequent extraction of phosphorus from ash. The target groups for this work are energy companies, suppliers of grate boilers, municipalities, wastewater treatment plants and authorities.

    The project involves the mixing of sewage sludge and demolition wood, combustion-tests of the fuel mixtures and laboratory experiments on bottom ash and fly ash for phosphorus extraction using EasyMining Sweden's method for phosphorus extraction from ash. Extensive analyses have been carried out on fuel, bottom ash and fly ash, as well as thermodynamic equilibrium calculations on the formed compounds containing phosphorus.

    The experience of preparing sludge fuel mixtures shows that the mixtures should be prepared in the near future to when they are to be combusted, to avoid a composting process in the fuel. The project shows that it is possible to combust sludge fuel mixtures with an admixture of up to 45 % sludge relative wet fuel, in an existing grate boiler during one day. However, to combust sludge fuel mixtures over a longer period of time and at a higher load, modifications of the de-ashing system and the flue gas cleaning system are needed. The results indicate a reduced tendency of slagging on the fuel bed at the combustion of sludge mixtures. The analyses of the fly ash showed a trend towards less corrosive ash at combustion of sludge mixtures. The phosphorus content in the ash in this work was 3-4 %. For process economics and from the phosphorus extraction point, as high phosphorus content as possible in the ash is preferable. Higher phosphorus content can be accomplished by mixing sludge with a fuel with lower ash content than demolition wood, co-combustion with a fuel with higher phosphorus content than demolition wood, or by increasing the percentage of sewage sludge in the fuel mixture. Still, a higher proportion of sludge in the mixture would require a higher dry matter content of the sludge in order to get proper combustion conditions. It is primarily bottom ash that is suitable for phosphorus extraction using Easy Mining Sweden's method. If fly ash are to be used for phosphorus extraction, an optimization of the dissolution conditions is required, which was not included in this project. In this project, phosphorus is extracted as ammonium phosphate. The purity of ammonium phosphate is very high, which means that unwanted substances and heavy metals in sewage sludge will not be returned to contaminate fields.

  • 15.
    Edo Gimenez, Mar
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Energy Engineering, Department of Engineering Sciences & Mathematics, Luleå University of Technology, Luleå, Sweden.
    Gao, Qiuju
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Persson, Per-Erik
    Jansson, Stina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    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.

  • 16.
    Elbashir, Sana
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Thermodynamic modelling assisted three-stage solid state synthesis of high purity β-Ca3(PO4)22024Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 238, artikel-id 112679Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A three-stage solid state synthesis assisted by thermodynamic modelling was developed to prepare highly pure (>99 %) beta tricalcium phosphate (β-TCP) powder. The optimal synthesis temperature was experimentally determined to be 1000 °C in good agreement with the theoretical calculations. The synthesis design described here has substantially improved the product quality and eliminated the presence of secondary phosphate phases compared to one- and two-stage methods investigated in this work. A comprehensive characterization of the material's structural, vibrational, and morphological characteristics was conducted. Rietveld refinement of the X-ray diffraction data confirmed the high purity of the samples. The crystal structure of the prepared β-TCP was determined and the refined unit cell parameters agreed well with the reference values. From infrared and Raman spectral analyses, the characteristics of β-TCP were observed and discussed in details. Furthermore, the morphology and elemental composition of the products were examined and found to be homogenous and impurity free. The reproducibility of the material was scrutinized and showed no significant data variations. Using our three-stage synthesis method, it is possible to produce β-TCP powder of high purity with consistent repeatability.

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  • 17.
    Elbashir, Sana
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Ramstedt, Madeleine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Thyrel, Mikael
    Sveriges Lantbruksuniversitet, Institutionen för skogens biomaterial och teknologi.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Structural Study On The Chemical Environment Surrounding Phosphorus In Ash Fractions Suitable For Nutrient Recovery2022Ingår i: ESPC4 & PERM5 2022 – Book of Abstracts, 2022Konferensbidrag (Refereegranskat)
    Abstract [sv]

    Nutrient recovery is an integral part of sustainable clean energy production where one of the most important nutrients is phosphorus (P). Phosphorus recovery from biomass and waste ashes has been a hot topic for research and development activities for decades. However, the chemical speciation of heavy metals (HM) that may be included in recovered phosphates is yet to be resolved. Numerous trial and error approachs have been applied to lower the amount of HM content by fuel design and/or additives. Nevertheless, the connection between P and HM is theses complex phosphate systems on the atomic level is not fully understood. Therefore, exploring if HM are associated with phosphates is paramount for creating a naturallink between sustainable energy production and primary production of biomass.

    This study aims to examine the formation of different phosphates found in ashes and the potential inclusion of HM in their structures. The inclusion of Zn and Cu in whitlockite phosphates is investigated by powder X-ray diffraction and FTIR/RAMAN spectroscopy to identify possibilities and challenges with direct application of P-rich ash fractions as a nutrient source for plants. These measurements will be complemented by synchrotron-based X-rayabsorption spectroscopy analysis in future work.

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    poster
  • 18.
    Eriksson, Gunnar
    et al.
    Swedish Univ Agr Sci, Dept Forest Resource Management, S-90183 Umea, Sweden.
    Grimm, Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Combustion and fuel characterisation of wheat distillers dried grain with solubles (DDGS) and possible combustion 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 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 the mixture of LR and wheat DDGS 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.

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  • 19.
    Falk, Joel
    et al.
    Energy Engineering, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Hannl, Thomas Karl
    Energy Engineering, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. BEST-Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, Graz, Austria; Institute of Chemical, Environmental & Bioscience Engineering, TU Vienna, Vienna, Austria.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Energy Engineering, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Thermodynamic Equilibrium Study on the Melting Tendency of the K-Ca-Mg-P-Si-O System with Relevance to Woody and Agricultural Biomass Ash Compositions2022Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 36, nr 13, s. 7035-7051Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A major challenge in the combustion of biomass fuels is the heterogeneity of ash-forming elements, which may cause a wide range of ash-related problems. Understanding the melting tendency of the coarse ash fractions is necessary to mitigate agglomeration and slagging. This work aims to evaluate the melting tendency of the K-Ca-Mg-Si-P-O system by use of thermodynamic equilibrium calculations. The formation of condensed phases were systematically assessed in a combustion atmosphere, varying temperatures, and composition. Compositional ranges were based on fuel ash data extracted from the Phyllis 2 database. The speciation and degree of polymerization of phosphates, silicates, and melts were evaluated and indicated a systematic variation in composition. The melt fraction was predicted as a function of temperature and composition. The melting tendency was modeled for three systems, i.e., a P-dominated, a Si-dominated, and a mixed Si-P system. Four ratios between K2O, CaO, MgO, SiO2, and P2O5 were found to have a large effect on the melting tendency of the ash mixtures: the ratio between network formers (SiO2, P2O5), K2O to total network modifiers, CaO to CaO + MgO, and the ratio of network formers to total ash oxides. This modeling approach showed qualitative agreement with ash-related issues seen in previous lab-scale experiments in bubbling fluidized bed and fixed bed combustion. Practical implications of the results are discussed from the perspective of fuel design with the aim of preventing ash-related problems. This study presents a novel method of applying thermodynamic equilibrium calculations for a broad range of compositions and shows potential for predicting ash-related issues related to the melting of coarse ash fractions.

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  • 20.
    Falk, Joel
    et al.
    Energy Engineering, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Hannl, Thomas Karl
    Energy Engineering, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Öhman, Marcus
    Energy Engineering, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Hedayati, Ali
    Energy Engineering, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. BEST−Bioenergy and Sustainable Technologies GmbH, Graz, Austria; Institute of Chemical, Environmental & Bioscience Engineering, TU Vienna, Vienna, Austria.
    Ash transformation during fixed-bed co-combustion of sewage sludge and agricultural residues with a focus on phosphorus2023Ingår i: ACS Omega, E-ISSN 2470-1343, Vol. 8, nr 14, s. 13162-13176Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work investigates the ash transformation during fixed-bed co-combustion of sewage sludge mixtures with the agricultural residues wheat straw and sunflower husks, focusing on the fate of phosphorus (P) in the resulting ash fractions. The study aims to determine suitable process parameters for fixed-bed combustion of fuels previously investigated in single-pellet experiments. The pure fuels and fuel mixtures were combusted in a 20 kWth residential pellet burner while monitoring the flue gas composition, temperature, and particulate matter formation. Subsequently, the different ash fractions were collected and characterized by CHN, SEM/EDS, and XRD analysis. The results showed that co-combustion of sewage sludge and agricultural residues reduced the formation of particulate matter as well as the formation of slag. Co-combustion of sewage sludge with either agricultural residue resulted in a change in phosphate speciation, displaying higher shares of Ca and lower shares of Fe and Al in the formed orthophosphates as well as amorphous phases containing higher shares of K. The formation of K-bearing phosphates was hindered by the spatial association of P with Ca and Fe in the sewage sludge, the incorporation of available K in K-Al silicates, and the depletion of K in the P-rich melt phase. Compared to mono-combustion, co-combustion experiments showed the potential for improving the combustion performance and reducing the risk of slag formation. The outcome suggests that co-combustion is a feasible path to integrate waste streams in fixed-bed energy conversion with simultaneous formation of phosphates enabling P recovery.

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  • 21.
    Falk, Joel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Grimm, Alejandro
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Difference in phosphate speciation between sewage sludge and biomass ash from fluidized bed combustion2018Ingår i: 27th International Conference of Impacts of Fuel Quality on Power Production and the Environment, September 23–28 September, 2018, Lake Louise, Canada, 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    The role of phosphorus in biomass combustion is a topic that has become increasingly relevantin recent years. Due to the demand for new sources of renewable energy and recovery of phosphorus from waste streams such as sewage sludge, research into the behavior of phosphorus during combustion is necessary for a continued development. This study aims to investigate potential differences in phosphate behavior during co-combustion of sewage sludge compared to other phosphorus-rich biomass or additives. The investigation was carried out in a bench scale bubbling fluidized bed, co-combusting six biomass blends of similar ash composition and combustion conditions but with different phosphorus association (logging residues (LR) or wheat straw (WS) with sewage sludge (SS), dried distiller’s grain (DG), or phosphoric acid (PA)). After combustion, bed ash samples, fly ash deposits and cyclone ash were collected and analyzed for elemental composition (SEM-EDS) and phase composition (XRD). Based on the XRD phase analyses, a significant difference in phosphate speciation were foundbetween biomass blends containing SS compare to DG or PA. Only two phosphate phases were identified in the ash from SS blends compared to a large variety of phosphates in ash from DG or PA blends. The difference in speciation could not be explained by a difference in ash fractionation as the elemental composition of the analyzed ash fractions were similar. Rather, the results indicate that the behavior of phosphorus in SS may be different to that in DG or PA.

  • 22. Falk, Joel
    et al.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Grimm, Alejandro
    Ohman, Marcus
    Systematic Evaluation of the Fate of Phosphorus in Fluidized Bed Combustion of Biomass and Sewage Sludge2020Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 34, nr 4, s. 3984-3995Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Comprehensive knowledge concerning the behavior of phosphorus (P) during combustion is necessary to enable more efficient recovery of P from combustion ashes for agricultural purposes. To this end, parameters that influence the distribution and speciation of P in combustion ashes are important because they may influence which ash fractions are suitable for P recovery. This study aims to determine the fate of P as a result of fuel ash composition and chemical association in the fuel during fluidized bed combustion by a systemic review of previous work. The synthesis was performed by comparing scanning electron microscopy–energy-dispersive X-ray spectroscopy and X-ray diffraction chemical analyses of bed ash, fly ash particles, and deposits from fluidized bed combustion of different blends of P-poor (logging residues or wheat straw) and P-rich (sewage sludge, dried distiller’s grain with solubles, or phosphoric acid) fuels and additives. The blends were produced to have a similar ash composition but with a different P source. The distribution of P among ash fractions indicated that P is mainly found in the coarse ash fractions (bed and cyclone ash), irrespective of fuel ash composition or chemical association in the fuel. The chemical speciation of P in coarse ash fractions differed between biomass blends containing sewage sludge compared to blends with phosphoric acid or dried distiller’s grain with solubles. Phosphates in the ash from the two sewage sludge blends included predominantly Ca with minor inclusion of other cations. In contrast, ashes from the blends with phosphoric acid or dried distiller’s grain with solubles contained phosphates with a significant amount of K, Ca, and Mg. The difference in phosphate speciation could not solely be explained by the combustion conditions and the elemental composition of the ash fractions. These results show that it is necessary to consider the chemical association of P in the fuel to predict the type of phosphates that will form in fluidized bed combustion ashes.

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  • 23. Falk, Joel
    et al.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Grimm, Alejandro
    Öhman, Marcus
    Fate of Phosphorus in Fixed Bed Combustion of Biomass and Sewage Sludge2020Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 34, nr 4, s. 4587-4594Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The recovery of phosphorus (P) from societal waste streams, such as sewage sludge, could make a significant contribution to alleviating the global dependency upon non-renewable phosphate sources, such as phosphate rock. This study aims to determine the effect of fuel ash composition, chemical association, and combustion technology on the fate of P in ashes from the combustion of sewage sludge and biomass blends to enable more efficient P recovery from combustion ashes. Experiments were performed in a fixed bed pellet burner (20 kW), combusting two sewage sludge blends and three biomass blends of similar fuel ash composition but with different P source (sewage sludge, dried distiller's grain with solubles, or phosphoric acid). Slag, bottom ash, and particulate matter samples were collected and analyzed by scanning electron microscopy-energy-dispersive X-ray spectroscopy and X-ray diffraction for morphology and elemental and crystalline phase composition and compared to results from experiments in fluidized bed combustion using the same fuel blends reported separately. The distribution and elemental composition of ash fractions indicated that sub-micrometer particles contained a minor share of fuel P, with the significant share of fuel P found in the slag and bottom ash fractions. No apparent difference in phosphate speciation could be observed between the slag and bottom ash from sewage sludge blends and biomass blends, with a range of crystalline Ca, Mg, and K phosphates detected in the ash. By comparison, only Ca-rich phosphates were detected in the ashes from the combustion of the sewage sludge blends in the bench-scale fluidized bed. The difference in P speciation between the technologies was attributed to a difference in the process temperature between the two technologies. In comparison to fluidized bed combustion, fixed bed combustion favored the formation of (Ca, Mg)-K phosphates rather than Ca phosphates for similar fuel blends.

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  • 24.
    Faust, Robin
    et al.
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, 412 96 Gothenburg, Sweden.
    Fürsatz, Katharina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. BEST – Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, Graz, Austria; TU Wien, Institute of Chemical, Environmental and Bioscience Engineering (ICEBE), Getreidemarkt 9/166, Vienna, Austria.
    Aonsamang, Panida
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, 412 96 Gothenburg, Sweden.
    Sandberg, Marcus
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, 412 96 Gothenburg, Sweden.
    Kuba, Matthias
    BEST – Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, Graz, Austria; TU Wien, Institute of Chemical, Environmental and Bioscience Engineering (ICEBE), Getreidemarkt 9/166, Vienna, Austria.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Knutsson, Pavleta
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, 412 96 Gothenburg, Sweden.
    Early layer formation on K-feldspar during fluidized bed combustion with phosphorus-rich fuel2023Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 331, artikel-id 125595Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    K-feldspar was utilized as bed material for fluidized bed combustion of bark, chicken manure, and their mixture. Bed samples were extracted after 4 and 8 h and the samples were analyzed with scanning electron microscopy to study the impact of P-rich chicken manure on the bed material. The results were compared to fixed bed exposures with different orthophosphates to investigate their influence in detail. The fresh bed material used for this study exhibited an uneven surface with many cavities which facilitated the deposition and retention of the fuel ash. Utilizing pure chicken manure as fuel led to the formation of Ca- and P-rich particles which accumulated in these cavities. At the same time, larger ash particles were formed which consisted of the elements found in chicken manure ash. The co-combustion of bark and chicken manure led to the interaction of the two ash fractions and the formation of a thicker ash layer, which consisted of elements from both fuel ashes, namely Ca, P, Si, K and S. The layer appeared to be partially molten which could be favorable for the deposition of ash particles and thereby the formation of a mixed Ca/K-phosphate. Fixed bed exposures of the K-feldspar particles with Na3PO4 or K3PO4 caused particle agglomeration which means presence of alkali-phosphates should be limited. The co-combustion of bark with chicken manure showed promising results both regarding a shift from Ca-phosphates to more bioavailable Ca/K-phosphates and an acceleration in ash layer formation. The formation of an ash layer after only 4 h of exposure with the mixture of bark and chicken manure could be advantageous for catalytic activation of the bed material.

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  • 25.
    Faust, Robin
    et al.
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, Gothenburg, Sweden.
    Valizadeh, Ali
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Qiu, Ren
    Chalmers University of Technology, Department of Physics, Kemigården 1, Gothenburg, Sweden.
    Tormachen, Alyona
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, Gothenburg, Sweden.
    Maric, Jelena
    Division of Energy Technology, Department of Space, Earth, Environment (SEE), Chalmers University of Technology, Gothenburg, Sweden.
    Vilches, Teresa Berdugo
    Division of Energy Technology, Department of Space, Earth, Environment (SEE), Chalmers University of Technology, Gothenburg, Sweden.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Seemann, Martin
    Division of Energy Technology, Department of Space, Earth, Environment (SEE), Chalmers University of Technology, Gothenburg, Sweden.
    Halvarsson, Mats
    Chalmers University of Technology, Department of Physics, Kemigården 1, Gothenburg, Sweden.
    Öhman, Marcus
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Knutsson, Pavleta
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, Gothenburg, Sweden.
    Role of surface morphology on bed material activation during indirect gasification of wood2023Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 333, artikel-id 126387Artikel i tidskrift (Refereegranskat)
    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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  • 26.
    Grimm, Alejandro
    et al.
    Lulea Univ Technol, Dept Engn Sci & Math, SE-97187 Lulea, Sweden.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Lulea Univ Technol, Dept Engn Sci & Math, SE-97187 Lulea, Sweden.
    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)
    Abstract [en]

    The influence of phosphorus on the alkali distribution in fluidized (quartz) bed combustion using two different typical biomasses (logging residues and wheat straw) was studied. Phosphoric acid (H3PO4) was used as an additive. The produced ash fractions were analyzed for morphology and elemental composition by scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), and crystalline phases by powder X-ray diffraction (P-XRD). For both fuel assortments tested, a reduction of volatilized deposit and fine particle-forming matter, containing mainly KCl, was achieved by adding phosphorus. For the wheat straw, this effect was considerable at medium and high phosphorus addition. As a consequence, an increased amount of potassium was found in the coarse ash particle fractions, principally as CaKPO4, KMgPO4, and CaK2P2O7, at the same time that the levels of HCl and SO2 in the flue gases increased. Generally, the addition of phosphorus to the studied biomasses changed the alkali distribution from being dominated by amorphous K-silicate coarse ash fractions and fine particulate KCl, to a system dominated by crystalline coarse ash of K-Ca/Mg-phosphates and fine particulate K2SO4. This implies that the fouling and high-temperature corrosion observed in industrial-scale combustion of problematic biofuels can possibly be reduced by employing additives rich in reactive phosphorus, on the condition that the higher concentrations of acidic gases can be tolerated. In order to achieve these effects, the relationship between alkali and alkaline-earth metals (i.e., (K + Na)/(Ca + Mg)) in the overall fuel ash must be considered. With respect to this, the formation of low-temperature-melting alkali-rich phosphates should not be promoted, to avoid potential increases in bed agglomeration tendencies and phosphorus release from the bed.

  • 27.
    Grimm, Alejandro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    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.

  • 28.
    Grimm, Alejandro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Diaz, Maryori
    Eriksson, Gunnar
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Effects of phosphorus addition by additives or co-firing on the ash transformation processes such as bed agglomerations and deposit formation during combustion of ash-rich biomass fuels2009Ingår i: 17th European Biomass Conference & Exhibition - Proceedings: From Research to Industry and Markets, 2009Konferensbidrag (Refereegranskat)
  • 29.
    Grimm, Alejandro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Eriksson, Gunnar
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    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.

  • 30.
    Hannl, Thomas Karl
    et al.
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Häggström, Gustav
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Hedayati, Ali
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria; BEST - Bioenergy and Sustainable Technologies GmbH, Graz, Austria.
    Kuba, Matthias
    Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria; BEST - Bioenergy and Sustainable Technologies GmbH, Graz, Austria.
    Öhman, Marcus
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Ash transformation during single-pellet gasification of sewage sludge and mixtures with agricultural residues with a focus on phosphorus2022Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 227, artikel-id 107102Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The recovery of phosphorus (P) from sewage sludge ashes has been the focus of recent research due to the initiatives for the use of biogenic resources and resource recovery. This study investigates the ash transformation chemistry of P in sewage sludge ash during the co-gasification with the K-Si- and K-rich agricultural residues wheat straw and sunflower husks, respectively, at temperatures relevant for fluidized bed technology, namely 800 °C and 950 °C. The residual ash was analyzed by ICP­AES, SEM/EDS, and XRD, and the results were compared to results of thermochemical equilibrium calculations. More than 90% of P and K in the fuels were retained in the residual ash fraction, and significant interaction phenomena occurred between the P-rich sewage sludge and the K-rich ash fractions. Around 45–65% of P was incorporated in crystalline K-bearing phosphates, i.e., K-whitlockite and CaKPO4, in the residual ashes with 85–90 wt% agricultural residue in the fuel mixture. In residual ashes of sewage sludge and mixtures with 60–70 wt% agricultural residue, P was mainly found in Ca(Mg,Fe)-whitlockites and AlPO4. Up to about 40% of P was in amorphous or unidentified phases. The results show that gasification provides a potential for the formation of K-bearing phosphates similar to combustion processes.

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  • 31. Hannl, Thomas Karl
    et al.
    Sefidari, Hamid
    Kuba, Matthias
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. BEST - Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, AT-8010, Graz, Austria; Institute of Chemical, Environmental & Bioscience Engineering, TU Vienna, AT-1060 Vienna, Austria.
    Öhman, Marcus
    Thermochemical equilibrium study of ash transformation during combustion and gasification of sewage sludge mixtures with agricultural residues with focus on the phosphorus speciation2021Ingår i: Biomass Conversion and Biorefinery, ISSN 2190-6815, E-ISSN 2190-6823, Vol. 11, nr 1, s. 57-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The necessity of recycling anthropogenically used phosphorus to prevent aquatic eutrophication and decrease the economic dependency on mined phosphate ores encouraged recent research to identify potential alternative resource pools. One of these resource pools is the ash derived from the thermochemical conversion of sewage sludge. This ash is rich in phosphorus, although most of it is chemically associated in a way where it is not plant available. The aim of this work was to identify the P recovery potential of ashes from sewage sludge co-conversion processes with two types of agricultural residues, namely wheat straw (rich in K and Si) and sunflower husks (rich in K), employing thermodynamic equilibrium calculations. The results indicate that both the melting behavior and the formation of plant available phosphates can be enhanced by using these fuel blends in comparison with pure sewage sludge. This enhanced bioavailability of phosphates was mostly due to the predicted formation of K-bearing phosphates in the mixtures instead of Ca/Fe/Al phosphates in the pure sewage sludge ash. According to the calculations, gasification conditions could increase the degree of slag formation and enhance the volatilization of K in comparison with combustion conditions. Furthermore, the possibility of precipitating phosphates from ash melts could be shown. It is emphasized that the results of this theoretical study represent an idealized system since in practice, non-equilibrium influences such as kinetic limitations and formation of amorphous structures may be significant. However, applicability of thermodynamic calculations in the prediction of molten and solid phases may still guide experimental research to investigate the actual phosphate formation in the future.

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  • 32.
    Hannl, Thomas Karl
    et al.
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria; BEST - Bioenergy and Sustainable Technologies GmbH, Graz, Austria.
    Priščák, Juraj
    Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria; BEST - Bioenergy and Sustainable Technologies GmbH, Graz, Austria.
    Öhman, Marcus
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Kuba, Matthias
    Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria; BEST - Bioenergy and Sustainable Technologies GmbH, Graz, Austria.
    Bubbling fluidized bed co-combustion and co-gasification of sewage sludge with agricultural residues with a focus on the fate of phosphorus2024Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 357, artikel-id 129822Artikel i tidskrift (Refereegranskat)
    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.

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  • 33. He, Hanbing
    et al.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Öhman, Marcus
    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.

  • 34. He, Hanbing
    et al.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå SE-971 87, Sweden.
    Öhman, Marcus
    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 focused on the layer characteristics of K-feldspar bed particles. The layer characteristics of K-feldspar bed particles were therefore investigated by collecting bed material samples of different ages from fluidized bed combustion of woody fuels in large-scale bubbling and circulating fluidized bed facilities. Scanning electron microscopy/energy-dispersive spectroscopy was used to analyze the layer morphology and elemental composition. Bed particles aged 1 day displayed a thin layer rich in Si, Ca, and Al. Inner layers had a more homogeneous composition than the outer layers, which instead were more heterogeneous and sometimes contained discernible fuel ash particles. The outer layer was thinner for K-feldspar bed particles sampled from circulating fluidized bed, as compared to particles from bubbling fluidized bed. The concentration of Ca in the inner layer increases toward the bed particle surface, the molar ratio of Si/Al is maintained, and the molar ratio of K/Al decreases as 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 in the inner layer formation process.

  • 35.
    Hedayati, Ali
    et al.
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Falk, Joel
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Boren, Eleonora
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Lindgren, Robert
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Ash Transformation during Fixed-Bed Combustion of Agricultural Biomass with a Focus on Potassium and Phosphorus2022Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 36, nr 7, s. 3640-3653Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, ash transformation during fixed-bed combustion of different agricultural opportunity fuels was investigated with a special focus on potassium (K) and phosphorus (P). The fuel pellets were combusted in an underfed fixed-bed pellet burner. Residual ashes (bottom ash and slag) and particulate matter were collected and characterized by scanning electron microscopy-energy-dispersive X-ray spectroscopy, X-ray diffraction, inductively coupled plasma, and ion chromatography. The interpretation of the results was supported by thermodynamic equilibrium calculations. For all fuels, almost all P (>97%) was found in residual-/coarse ash fractions, while K showed different degrees of volatilization, depending on fuel composition. During combustion of poplar, which represents Ca-K-rich fuels, a carbonate melt rich in K and Ca decomposed into CaO, CO2, and gaseous K species at sufficiently high temperatures. Ca5(PO4)3OH was the main P-containing crystalline phase in the bottom ash. For wheat straw and grass, representing Si-K-rich fuels, a lower degree of K volatilization was observed than for poplar. P was found here in amorphous phosphosilicates and CaKPO4. For wheat grain residues, representing P-K-rich fuels, a high degree of both K and P retention was observed due to the interaction of K and P with the fuel-bed constituents, i.e., char, ash, and slag. The residual ash was almost completely melted and rich in P, K, and Mg. P was found in amorphous phosphates and different crystalline phases such as KMgPO4, K2CaP2O7, K2MgP2O7, and K4Mg4(P2O7)3. In general, the results therefore imply that an interaction between ash-forming elements in a single burning fuel particle and the surrounding bed ash or slag is important for the overall retention of P and K during fuel conversion in fixed-bed combustion of agricultural biomass fuels.

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  • 36.
    Hedayati, Ali
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Lindgren, Robert
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Ash transformation during single-pellet combustion of agricultural biomass fuels – focus on K and P2018Konferensbidrag (Övrigt vetenskapligt)
  • 37.
    Hedayati, Ali
    et al.
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Lindgren, Robert
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Kienzl, Norbert
    BEST - Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, Graz, Austria.
    Öhman, Marcus
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Ash Transformation during Single-Pellet Combustion of Agricultural Biomass with a Focus on Potassium and Phosphorus2021Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 35, nr 2, s. 1449-1464Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, ash transformation and release of critical ash-forming elements during single-pellet combustion of different types of agricultural opportunity fuels were investigated. The work focused on potassium (K) and phosphorus (P). Single pellets of poplar, wheat straw, grass, and wheat grain residues were combusted in a macro-thermogravimetric analysis reactor at three different furnace temperatures (600, 800, and 950 °C). In order to study the transformation of inorganic matters at different stages of the thermal conversion process, the residues were collected before and after full devolatilization, as well as after complete char conversion. The residual char/ash was characterized by scanning electron microscopy-energy-dispersive X-ray spectroscopy, X-ray diffraction, inductively coupled plasma, and ion chromatography, and the interpretation of results was supported by thermodynamic equilibrium calculations. During combustion of poplar, representing a Ca-K-rich woody energy crop, the main fraction of K remained in the residual ash primarily in the form of K2Ca(CO3)2 at lower temperatures and in a K-Ca-rich carbonate melt at higher temperatures. Almost all P retained in the ash and was mainly present in the form of hydroxyapatite. For the Si-K-rich agricultural biomass fuels with a minor (wheat straw) or moderate (grass) P content, the main fraction of K remained in the residual ash mostly in K-Ca-rich silicates. In general, almost all P was retained in the residual ash both in K-Ca-P-Si-rich amorphous structures, possibly in phosphosilicate-rich melts, and in crystalline forms as hydroxyapatite, CaKPO4, and calcium phosphate silicate. For the wheat grain, representing a K-P-rich fuel, the main fraction of K and P remained in the residual ash in the form of K-Mg-rich phosphates. The results showed that in general for all studied fuels, the main release of P occurred during the devolatilization stage, while the main release of K occurred during char combustion. Furthermore, less than 20% of P and 35% of K was released at the highest furnace temperature for all fuels.

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  • 38.
    Hedayati, Ali
    et al.
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Sefidari, Hamid
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden; RISE ETC (Energy Technology Centre) AB, Box 726, Piteå, Sweden.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kienzl, Norbert
    BEST – Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, Graz, Austria.
    Öhman, Marcus
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Ash transformation during single-pellet gasification of agricultural biomass with focus on potassium and phosphorus2021Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 217, artikel-id 106805Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Agricultural biomasses and residues can play an important role in the global bioenergy system but their potential is limited by the risk of several ash-related problems such as deposit formation, slagging, and particle emissions during their thermal conversion. Therefore, a thorough understanding of the ash transformation reactions is required for this type of fuels. The present work investigates ash transformation reactions and the release of critical ash-forming elements with a special focus on K and P during the single-pellet gasification of different types of agricultural biomass fuels, namely, poplar, grass, and wheat grain residues. Each fuel was gasified as a single pellet at three different temperatures (600, 800, and 950 °C) in a Macro-TGA reactor. The residues from different stages of fuel conversion were collected to study the gradual ash transformation. Characterization of the residual char and ash was performed employing SEM-EDS, XRD, and ICP with the support of thermodynamic equilibrium calculations (TECs). The results showed that the K and P present in the fuels were primarily found in the residual char and ash in all cases for all studied fuels. While the main part of the K release occurred during the char conversion stage, the main part of the P release occurred during the devolatilization stage. The highest releases – less than 18% of P and 35% of K – were observed at the highest studied temperature for all fuels. These elements were present in the residual ashes as K2Ca(CO3)2 and Ca5(PO4)3OH for poplar; K-Ca-rich silicates and phosphosilicates in mainly amorphous ash for grass; and an amorphous phase rich in K-Mg-phosphates for wheat grain residues.

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  • 39.
    Hermassi, Mehrez
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Chemical Engineering Department, East Barcelona Engineering School, Barcelona TECHUPC, Sant Adrià de Besòs, Spain.
    Granados, M.
    Valderrama, C.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Ayora, C.
    Cortina, J.L.
    Impact of functional group types in ion exchange resins on rare earth element recovery from treated acid mine waters2022Ingår i: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 379, nr Part 2, artikel-id 134742Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ion-exchange (IX) resins incorporating single functional groups (sulfonic or amino-phosphonic) and two functional groups (sulfonic and phosphonic) were evaluated for selective recovery of Rare Earth Elements (REEs) from acidic mine waters (AMW). The composition of AMW solution, complexing properties of the functional group, and acidity were investigated as key parameters for concentration and separation of REEs from transition elements (TEs). Fe has to be removed from AMW to enable REE recovery and here the AMW was treated with NaOH solutions to reach pH 3.9 where Fe(III) was selectively removed (≤99%) by precipitation of schwertmannite. Single functional IX resin containing a sulfonic group displayed a higher REE recovery efficiency and separation ratio than observed for the bi-functional resin (sulfonic/phosphonic). Concentration factors for REEs between 30 and 40 were achieved using regeneration cycles with H2SO4. The performance of the aminophosphonic resin showed lower separation factors for REEs from TEs than the two resins containing sulfonic groups. IX resins performance was improved by tuning the acidity to match the functional group reactivity, where pH adjustment to the range of 0.5–2.0 provided the highest REE/TE separation factor for the single sulfonic resin followed by the bifunctional resin. The integration of an elution cycle using Na2-EDTA/NH4Cl mixtures strongly increases the concentration factors of REE and Light REE (LREE) concentration factors of up to 260 were achieved for the single functional sulfonic resin.

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  • 40.
    Holmgren, Per
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Slag Formation during Entrained Flow Gasification: Calcium-Rich Bark Fuel with KHCO3 Additive2020Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 34, nr 6, s. 7112-7120Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Slag property management is of utmost importance for successful operation of entrained flow gasifiers. The present study investigates the influence of potassium introduced as KHCO3 on the ash and slag formation of softwood bark, a calcium-rich fuel, during entrained flow gasification. The bark contained only minor mineral inclusions causing the ash composition to be dominated by calcium and potassium. Wood bark with and without KHCO3 additive was gasified between 850 and 1400 degrees C at O-2 stoichiometric ratio (lambda) 0.6. The ash particles collided with a flat impact probe inside the hot reactor at particle impact angles set to 90 degrees, 60 degrees, and 30 degrees. The reactor and probe allowed long-distance microscope data collection close to the probe surface. Particle deposition was optically monitored and resulting deposits were analyzed by SEM-EDS and XRD. Thermodynamic equilibrium and viscosity calculations were used to assist interpretation of experimental results. The predicted temperature window for liquid carbonate formation was experimentally verified, but the melt fraction of the deposit was too low to cause efficient flow and removal of ash from the probe under the prevailing experimental conditions. At higher temperatures, spherical particles indicated lower ash melting temperatures than expected from the bulk ash composition, and a detailed mechanism was proposed.

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  • 41.
    Häggström, Gustav
    et al.
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Fürsatz, Katharina
    Bioenergy2020+ GmbH, Güssing, Austria; Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria.
    Kuba, Matthias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden; Bioenergy2020+ GmbH, Güssing, Austria; Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Fate of phosphorus in fluidized bed cocombustion of chicken litter with wheat straw and bark residues2020Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 34, nr 2, s. 1822-1829Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study aims to determine the fate of P during fluidized bed co-combustion of chicken litter (CL) with K-rich fuels [e.g., wheat straw (WS)] and Ca-rich fuels (bark). The effect of fuel blending on phosphate speciation in ash was investigated. This was performed by chemical characterization of ash fractions to determine which phosphate compounds had formed and identify plausible ash transformation reactions for P. The ash fractions were produced in combustion experiments using CL and fuel blends with 30% CL and WS or bark (B) at 790–810 °C in a 5 kW laboratory-scale bubbling fluidized bed. Potassium feldspar was used as the bed material. Bed ash particles, cyclone ash, and particulate matter (PM) were collected and subjected to chemical analysis with scanning electron microscopy–energy-dispersive X-ray spectrometry (SEM–EDS) and X-ray diffraction. P was detected in coarse ash fractions only, that is, bed ash, cyclone ash, and coarse PM fraction (>1 μm); no P could be detected in the fine PM fraction (<1 μm). SEM–EDS analysis showed that P was mainly present in K–Ca–P-rich areas for pure CL as well as in the ashes from the fuel blends of CL with WS or B. In the WS blend, P was found together with Si in these areas. The crystalline compound containing P was hydroxyapatite in all cases as well as whitlockite in the cases of pure CL and WS blend, of which the latter compound has been previously identified as a promising plant nutrient. The ash fractions from CL and bark blend only contained P in hydroxyapatite. Co-combustion of CL together with WS appears to be promising for P recovery, and ashes with this composition could be further studied in plant growth experiments.

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  • 42.
    Häggström, Gustav
    et al.
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Hannl, Thomas Karl
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Hedayati, Ali
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Kuba, Matthias
    BEST-Bioenergy and Sustainable Technologies GmbH, Graz, Austria; Institute of Chemical, Environmental and Bioscience Engineering, Tu Vienna, Vienna, Austria.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. BEST-Bioenergy and Sustainable Technologies GmbH, Graz, Austria; Institute of Chemical, Environmental and Bioscience Engineering, Tu Vienna, Vienna, Austria.
    Öhman, Marcus
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Single Pellet Combustion of Sewage Sludge and Agricultural Residues with a Focus on Phosphorus2021Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 35, nr 12, s. 10009-10022Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recycling of phosphorus in combination with increased utilization of bioenergy can mitigate material and global warming challenges. In addition, co-combustion of different fuels can alleviate ash-related problems in thermal conversion of biomass. The aim of this study is to investigate the ash transformation reactions of mainly P in co-combustion of P-rich sewage sludge (SS) with K-rich sunflower husks (SH) and K-And Si-rich wheat straw (WS). Single pellets of 4 mixtures (10 and 30 wt % SS in WS and 15 and 40 wt % SS in SH) and pure SS were combusted in an electrically heated furnace at process temperatures relevant for fluidized bed combustion (800 and 950 °C). Collected ash fractions were analyzed by inductively coupled plasma techniques, ion chromatography, scanning electron microscopy-energy-dispersive X-ray spectroscopy, and X-ray diffraction. Thermodynamic equilibrium calculations were performed to interpret the results. Over 90% of K and P was found to be captured within the residual ash with 30-70% P in crystalline K-bearing phosphates for mixtures with low amounts of SS (WSS10 and SHS15). The significant share of K and P in the amorphous material could be important for P recovery. For the lower percentage mixtures of SS (WSS10 and SHS15), P in crystalline phases was mainly found in K-whitlockite and CaKPO4. For the higher percentage SS mixtures, most of P was found in whitlockites associated with Fe and Mg, and no crystalline phosphates containing K were detected. For P recovery, co-combustion of the lower SS mixtures is favorable, and they are suggested to be further studied concerning the suitability for plant growth.

  • 43. Häggström, Gustav
    et al.
    Karl Hannl, Thomas
    Holmgren, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Fate of phosphorus in pulverized fuel co-combustion of sewage sludge and agricultural residues2023Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 335, artikel-id 127059Artikel i tidskrift (Refereegranskat)
    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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  • 44.
    Ismail, Norafiqah
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Zhou, Qiuyueming
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Wang, Qian
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Cui, Zhaoliang
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Tavajohi, Naser
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Dibasic esters as green solvents for PVDF membrane preparation2023Ingår i: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 25, nr 18, s. 7259-7272Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solvent toxicity is a major barrier to sustainable fabrication of polymeric membranes. This study introduces three dibasic esters (DBEs) as alternative membrane fabrication solvents that are biodegradable, non-carcinogenic, non-corrosive, and non-hazardous. The use of DBEs in fabrication processes shifts the monotectic point in the phase diagram of PVDF/solvent systems towards higher polymer concentrations, enabling membrane formation by liquid–liquid phase inversion to produce a bicontinuous structure that confers outstanding performance. The best-performing membrane prepared in this way had an exceptional flux of 42.40 kg m−2 h−1 and a high rejection rate (>99%) in the decontamination of synthetic nuclear wastewater. Compared to membranes prepared previously using toxic and non-toxic solvents, membranes fabricated in DBEs exhibited superior mechanical performance due to their bicontinuous structure, which effectively distributes external forces throughout the membrane. Moreover, DBEs are cheaper than toxic conventional solvents and are readily available in bulk, making them attractive options for industrial-scale membrane production.

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  • 45.
    Kuba, Matthias
    et al.
    Technische Universität Wien, Institute of Chemical Engineering.
    He, Hanbing
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Kirnbauer, Friedrich
    Technische Universität Wien, Institute of Chemical Engineering.
    Skoglund, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Hofbauer, Hermann
    Technische Universität Wien, Institute of Chemical Engineering.
    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.

  • 46.
    Kuba, Matthias
    et al.
    Technische Universität Wien, Institute of Chemical Engineering.
    He, Hanbing
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Kirnbauer, Friedrich
    Technische Universität Wien, Institute of Chemical Engineering.
    Skoglund, Nils
    Luleå University of Technology, Energy Engineering, Division of Energy Science, Luleå, Sweden.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Hofbauer, Hermann
    Technische Universität 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.

  • 47.
    Kuba, Matthias
    et al.
    BEST Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, Graz, Austria; TU Wien, Institute of Chemical, Environmental and Bioscience Engineering, Vienna, Austria.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Hofbauer, Hermann
    TU Wien, Institute of Chemical, Environmental and Bioscience Engineering, Vienna, Austria.
    A review on bed material particle layer formation and its positive influence on the performance of thermo-chemical biomass conversion in fluidized beds2021Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 291, artikel-id 120214Artikel, forskningsöversikt (Refereegranskat)
    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.

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  • 48.
    Kumpiene, Jurate
    et al.
    Luleå University of Technology.
    Brännvall, Evelina
    Luleå University of Technology.
    Wollters, Martin
    Skoglund, Nils
    Energy Engineering, Department of Engineering Sciences & Mathematics, Luleå University of Technology, SE-97187 Luleå, Sweden.
    Čirba, Stasys
    Aksamitauskas, Vladislovas Česlovas
    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.

  • 49.
    Li, Gule.
    et al.
    Centre for Energy Technology, School of Chemical Engineering and Advanced Materials, The University of Adelaide, Adelaide, Australia.
    Nathan, Graham J.
    Centre for Energy Technology, School of Mechanical Engineering, The University of Adelaide, Adelaide, Australia.
    Kuba, Matthias
    BEST Bioenergy and Sustainable Technologies GmbH, Inffeldgasse 21b, Graz, Austria; Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Getreidemarkt 9/166, Vienna, Austria.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Ashman, Peter J.
    Centre for Energy Technology, School of Chemical Engineering and Advanced Materials, The University of Adelaide, Adelaide, Australia.
    Saw, Woei L.
    Centre for Energy Technology, School of Chemical Engineering and Advanced Materials, The University of Adelaide, Adelaide, Australia.
    Agglomeration of olivine with potassium- or silicon-rich agricultural residues under conditions relevant to dual fluidized bed gasification2022Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 36, nr 23, s. 14253-14266Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The agglomeration characteristics of olivine- and potassium (K)-rich grape marc or silicon (Si)-rich wheat straw were studied in a laboratory-scale fluidized reactor and compared under air combustion, steam gasification, or CO2 gasification atmospheres at temperatures relevant to a dual fluidized bed gasifier. Agglomeration with grape marc is found to be induced mostly by the formation of adhesive K-rich layers onto the olivine, a process that is significantly augmented in a steam atmosphere compared to that in the air or CO2. The formation of an initial K-rich outer layer, which is caused by the mere physical attachment of K-species onto the olivine surface, facilitated the formation of an inner layer. This inner layer exhibits chemical reactions between grape marc ash and olivine, with the ash elements involved in the chemical reactions differing between combustion and steam gasification environments. Agglomeration with a wheat straw is most significant under air combustion conditions and depends primarily on the temperature rather than on the atmosphere.

  • 50.
    Ma, Charlie
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Carlborg, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Structures and diffusion motions of K and Ca in biomass ash slags from molecular dynamics simulations2021Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 302, artikel-id 121072Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ash slag formations that can occur in combustion and gasification of solid fuels often consist of silicate melts that can cause operational problems, e.g., bed agglomeration or slag build-up. This study aims to better understand the underlying molecular structures and motions that bring about viscosity variations in biomass ash slags that are rich in Ca and K. Aspects of slag structure, diffusivity, and cation motion in the molten CaO–K2O–SiO2 system were acquired from molecular dynamics simulations. These results are discussed in relation to viscosity values found in literature. Among the structural characteristics of the silicate network, the simulations showed that the local structures of both Ca and K were affected by composition, with stronger integration of Ca within the silicate network than K. The formation of larger ring structures due to network depolymerisation occurred with increasing diffusivity and lower viscosity, but small rings prevailed due to clusters of Si and O atoms that formed cohesive structures. Both Ca and K showed hopping motions as they diffused through the network, especially in high viscosity compositions. These cations exhibited preferential migration to positions previously occupied by the same species, as a means of moving around the network-forming Si and O atoms that diffused slower. The diffusivity of K ions was facilitated by transport in percolation channels. The presence of slower-diffusing Ca ions occupied positions that could otherwise have contributed to K diffusivity. This work contributes towards understanding of ash slags in thermochemical processes by exploring network modifier mobility in silicate slags.

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