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  • 1.
    Hosseinian, Aida
    et al.
    Water, Energy and Environmental Engineering Research Unit, Faculty of Technology, University of Oulu, 90014, Oulu, Finland.
    Pettersson, Anita
    University of Borås, Faculty of Textiles, Engineering and Business. Swedish Centre for Resource Recovery.
    Ylä-Mella, Jenni
    Water, Energy and Environmental Engineering Research Unit, Faculty of Technology, University of Oulu, 90014, Oulu, Finland.
    Pongrácz, Eva
    Water, Energy and Environmental Engineering Research Unit, Faculty of Technology, University of Oulu, 90014, Oulu, Finland.
    Phosphorus recovery methods from secondary resources, assessment of overall benefits and barriers with focus on the Nordic countries2023In: Journal of Material Cycles and Waste Management, ISSN 1438-4957, E-ISSN 1611-8227Article in journal (Refereed)
    Abstract [en]

    Phosphorus (P) recovery and recycling play a crucial role in improving resource efficiency, sustainable nutrient management and moving toward circular economy. Increasing demand for fertilizers, signs of geopolitical constraints, and high discharge of P to waterbodies are the other reasons to pursue the circularity of P. Various research have been carrying out and several processes have been developed for P-recovery from different resources. However, there is still a huge unexplored potential for P-recovery specially in the regional framework from the four main P-rich waste resources: food waste, manure, mining waste, and sewage sludge. This study reviews recovery methods of P from these secondary resources comprehensively. Additionally, it analyzes the Nordic viewpoint of P-cycle by evaluating Nordic reserves, demands, and secondary resources to gain a systematic assessment of how Nordic countries could move toward circular economy of P. Results of this study show that secondary resources of P in Nordic countries have the potential of replacing mineral fertilizer in these countries to a considerable extent. However, to overcome the challenges of P-recovery from studied resources, policymakers and researchers need to take decisions and make innovation along each other to open the new possibilities for Nordic economy.

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  • 2.
    Kharrazi, S. M.
    et al.
    Department of Natural Resources, Isfahan University of Technology, Isfahan 84156-83111, Iran.
    Soleimani, M.
    Department of Natural Resources, Isfahan University of Technology, Isfahan 84156-83111, Iran.
    Jokar, M.
    Department of Natural Resources, Isfahan University of Technology, Isfahan 84156-83111, Iran.
    Richards, Tobias
    University of Borås, Faculty of Textiles, Engineering and Business.
    Pettersson, Anita
    University of Borås, Faculty of Textiles, Engineering and Business.
    Mirghaffari, N.
    Department of Natural Resources, Isfahan University of Technology, Isfahan 84156-83111, Iran.
    Pretreatment of lignocellulosic waste as a precursor for synthesis of high porous activated carbon and its application for Pb (II) and Cr (VI) adsorption from aqueous solutions2021In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 180, p. 299-310Article in journal (Refereed)
    Abstract [en]

    Effects of Elm tree sawdust pretreatments using alkali and alkaline earth metals (NaCl, KCl, CaCl2, MgCl2 and Elm tree ash) and deashing solutions (water, HCl, HNO3 and aqua regia) before the carbonization process on the porosity of produced activated carbons and Pb (II) and Cr (VI) adsorption were studied. The activated carbons were characterized by pore size distribution, surface area, FTIR, and SEM-EDX analysies. Based on the results, HCl leaching pretreatment of the biomass increased the activated carbon adsorption capacity of Cr (VI) from 114 to 190 mg g−1. The treatment of biomass with alkali and alkali earth metal salts, especially MgCl2, remarkably increased the activated carbon adsorption capacity of Pb (II) from 233 to 1430 mg g−1. The results indicated that Pb (II) adsorption was attributed to both the mesoporous structure of activated carbon and the abundance of Mg on the activated carbon's surface. On the other hand, the micropores played a major role in Cr (VI) adsorption capacity. The development of the micro- or mesoporous structure of activated carbons through pretreatment of lignocellulosic precursor could be an approach for providing high performance activated carbons for Pb (II) and Cr (VI) removal from aqueous solutions.

  • 3.
    Moradian, Farzad
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    A. Tchoffor, Placid
    SP Technical Research Institute of Sweden.
    O. Davidsson, Kent
    SP Technical Research Institute of Sweden.
    Pettersson, Anita
    University of Borås, Faculty of Textiles, Engineering and Business.
    Backman, Rainer
    Umeå University.
    Thermodynamic equilibrium prediction of bed agglomeration tendency in dual fluidized-bed gasification of forest residues2016In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 154Article in journal (Refereed)
    Abstract [en]

    Dual fluidized-bed (DFB) gasification is one of the recently developed technologies for production of heat, power, transportation fuels and synthetic chemicals through steam gasification of biomass. Bed agglomeration is a serious ash-related problem that should be taken into account when biomass-based fuels are selected for fluidized-bed gasification and combustion. This study developed a thermodynamic equilibrium model to assess the risk of bed agglomeration in gasification and combustion reactors of a DFB gasifier using biomass (forest residues) as feedstock. The modelling approach combined thermodynamic equilibrium calculations with chemical fractionation technique to predict the composition and melting behaviour of the fuel-derived ash as well as bed particles coating layer in the gasification and combustion reactors. FactSage was employed for the thermodynamic equilibrium calculations. The modelling results were then compared with experimental data obtained from a full-scale DFB gasifier to estimate the reliability and validity of the predictive model. In general, a good agreement was found between the modelling results and experimental observations. For the forest residues as feedstock and olivine as bed material, the modelling results indicate a low risk of bed agglomeration in the DFB gasifier, as long as the dominant temperature in the combustion zone is below 1020 °C. In contrast, quartz as bed material in the DFB gasifier was shown to significantly increase the risk of bed agglomeration through coating-induced agglomeration mechanism. © 2016 Elsevier B.V.

  • 4.
    Moradian, Farzad
    et al.
    University of Borås, School of Engineering.
    Pettersson, Anita
    University of Borås, School of Engineering.
    Herstad Svärd, Solvie
    Richards, Tobias
    Co-combustion of animal waste in a commercial waste-to-energy BFB boiler2013In: Energies, E-ISSN 1996-1073, Vol. 6, no 12, p. 6170-6187Article in journal (Refereed)
    Abstract [en]

    Co-combustion of animal waste, in waste-to-energy boilers, is considered a method to produce both heat and power and to dispose of possibly infected animal wastes. This research conducted full-scale combustion tests to identify the impact of changed fuel composition on a fluidized-bed boiler. The impact was characterized by analyzing the deposit formation rate, deposit composition, ash composition, and emissions. Two combustion tests, denoted the reference case and animal waste case, were performed based on different fuel mixes. In the reference case, a normal solid waste fuel mix was combusted in the boiler, containing sorted industry and household waste. In the animal waste case, 20 wt% animal waste was added to the reference fuel mix. The collected samples, comprising sampling probe deposits, fuel mixes, bed ash, return sand, boiler ash, cyclone ash and filter ash, were analyzed using chemical fractionation, SEM-EDX and XRD. The results indicate decreased deposit formation due to animal waste co-combustion. SEM-EDX and chemical fractionation identified higher concentrations of P, Ca, S, and Cl in the bed materials in the animal waste case. Moreover, the risk of bed agglomeration was lower in the animal waste case and also a decreased rate of NOx and SO2 emissions were observed.

  • 5.
    Moradian, Farzad
    et al.
    University of Borås, School of Engineering.
    Pettersson, Anita
    University of Borås, School of Engineering.
    Richards, Tobias
    University of Borås, School of Engineering.
    Bed Agglomeration Characteristics during Cocombustion of Animal Waste with Municipal Solid Waste in a Bubbling Fluidized-Bed Boiler: A Thermodynamic Modeling Approach2014In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 28, no 3, p. 2236-2247Article in journal (Refereed)
    Abstract [en]

    ABSTRACT: Full-scale waste combustion tests showed that adding animal waste (AW) to municipal solid waste (MSW) prevented bed agglomeration, and the reason for this fi nding was not fully understood. This study uses thermodynamic modeling to investigate the composition of equilibrium products for two combustion scenarios: monocombustion of MSW (the reference case) and cocombustion of AW with MSW (the AW case). The modeling was performed using FactSage, and experimental data obtained during the full-scale combustion tests were used as input data for the calculations. The results of equilibrium modeling, together with information extracted from ternary phase diagrams, suggest higher bed temperature as the primary cause for formation of bed agglomerates in the reference case. In addition, melt-induced agglomeration is suggested as the bed agglomeration mechanism in this case. In the AW case, however, reduced bed temperature, as well as enriched calcium phosphate and sulfate in the bottom ashes are considered to signi fi cantly decrease the slagging tendency.

  • 6.
    Moradian, Farzad
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Pettersson, Anita
    University of Borås, Faculty of Textiles, Engineering and Business.
    Richards, Tobias
    University of Borås, Faculty of Textiles, Engineering and Business.
    Thermodynamic Equilibrium Model Applied to Predict Fouling Tendency in a Commercial Fluidized-Bed Boiler, Combusting Solid Waste2015In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 29, no 5, p. 3483-3494Article in journal (Refereed)
    Abstract [en]

    A thermodynamic equilibrium model, combined with an advanced fuel analysis, was applied to predict the fouling tendency in a commercial bubbling fluidized-bed (BFB) boiler, combusting a mixture of solid waste. In order to enhance the performance of the model, further modifications were made, considering the combustion pattern in the fluidized-bed system and also the temperature profile in the combustion zone. The modeling was performed using Factsage, and experimental data obtained during the full-scale measurements were used as input for the model, simulating the deposit formation in the real boiler. The simulation results were then compared with the results obtained during the full-scale combustion tests to estimate the accuracy and validity of the applied model. The thermodynamic equilibrium modeling proved to be a reliable tool for predicting the fouling in the BFB boiler, thus determining the fraction of the melt in the deposited salts formed on the heat transfer surfaces during the flue gas condensation. The calculations showed that the ratio of the SO2 to alkali chloride concentration in the flue gas was the decisive factor that affected the rate of the deposit formation in the boiler. Both the simulation and the experimental results indicated that lower bed temperatures and cocombustion of P-rich fuels decrease the deposition buildup in the boiler. © 2015 American Chemical Society.

  • 7.
    Nordin, Andreas
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Strandberg, Anna
    Department of Applied Physics and Electronics, Umeå University, SE-901 87 Umeå, Sweden.
    Elbashir, Sana
    Swedish Centre for Resource Recovery, University of Borås, SE-501 90 Borås, Sweden.
    Åmand, Lars-Erik
    Skoglund, Nils
    Department of Applied Physics and Electronics, Umeå University, SE-901 87 Umeå, Sweden.
    Pettersson, Anita
    University of Borås, Faculty of Textiles, Engineering and Business.
    Co-Combustion of Municipal Sewage Sludge and Biomass in a Grate Fired Boiler for Phosphorus Recovery in Bottom Ash2020In: Energies, E-ISSN 1996-1073, Vol. 13, no 7Article in journal (Refereed)
    Abstract [en]

    Phosphorus has been identified as a critical element by the European Union and recycling efforts are increasingly common. An important phosphorus-containing waste stream for recycling is municipal sewage sludge (MSS), which is used directly as fertilizer to farmland. However, it contains pollutants such as heavy metals, pharmaceutical residues, polychlorinated bi-phenyls (PCBs) and nano-plastics. The interest in combustion of MSS is continuously growing, as it both reduces the volume as well as destroys the organic materials and could separate certain heavy metals from the produced ashes. This results in ashes with a potential for either direct use as fertilizer or as a suitable feedstock for upgrading processes. The aim of this study was to investigate co-combustion of MSS and biomass to create a phosphorus-rich bottom ash with a low heavy metal content. A laboratory-scale fixed-bed reactor in addition to an 8 MWth grate-boiler was used for the experimental work. The concentration of phosphorus and selected heavy metals in the bottom ashes were compared to European Union regulation on fertilizers, ash application to Swedish forests and Swedish regulations on sewage sludge application to farmland. Element concentrations were determined by ICP-AES complemented by analysis of spatial distribution with SEM-EDS and XRD analysis to determine crystalline compounds. The results show that most of the phosphorus was retained in the bottom ash, corresponding to 9-16 wt.% P2O5, while the concentration of cadmium, mercury, lead and zinc was below the limits of the regulations. However, copper, chromium and nickel concentrations exceeded these standards.

  • 8.
    Oluoti, Kehinde
    et al.
    University of Borås, School of Engineering.
    Megwai, Godswill
    Pettersson, Anita
    University of Borås, School of Engineering.
    Richards, Tobias
    Nigerian Wood Waste: A Dependable and Renewable Fuel Option for Power Production2014In: World Journal of Engineering and Technology, ISSN 2331-4222, Vol. 2, p. 234-248Article in journal (Refereed)
    Abstract [en]

    Being an oil - rich country, Nigeria’s energy supply is primarily fossil - based. The unequal distribu - tion of oil wealth, along with agitation for self - determination and resource control, has led to the sabotage of oil installations. This, in turn, has affected all services running on the energy supply from these installations, leading to incessant or total sh ut - down of such facilities. Power generated using biomass - based renewable energy technologies is a promising option in limiting the coun - try’s dependence on fossil energy for power generation. The most important part of this option is on - site power generation via mini - grid systems. The power thus produced is utilized with the excess being fed into the national grid based on Feed - in - Tariff (F.i.T.) requirements and techni - calities. The important factors to be considered in the propagation of a mini - g rid option are ex - amined in this study. Furthermore, the study shows that about 1.3 TWh of electricity can be gener - ated from the 1.8 million tonnes per year of wood waste produced by the lumber industry in Nige - ria. Power generation through the utiliza tion of biomass has however proved to be a possible path in achieving economic, social and environmental sustainability in the country. Economic studies show that for small - scale power generation, internal combustion engines and Stirling engines are econom ically feasible. Steam turbines and gas turbines are mostly used in medium/large - scale biomass power generators, especially in proximity to biomass waste resources. Micro gas turbine power technology can also be applied on a small scale despite its high to tal investment capital.

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  • 9.
    Persson, Nils-Krister
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Baghaei, Behnaz
    University of Borås, Faculty of Textiles, Engineering and Business.
    Bashir, Tariq
    University of Borås, Faculty of Textiles, Engineering and Business.
    Brorström, Björn
    University of Borås, Faculty of Textiles, Engineering and Business.
    Hedegård, Lars
    University of Borås, Faculty of Textiles, Engineering and Business.
    Carlson Ingdahl, Tina
    University of Borås, Faculty of Textiles, Engineering and Business.
    Larsson, Jonas
    University of Borås, Faculty of Textiles, Engineering and Business.
    Lindberg, Ulla
    University of Borås, Faculty of Textiles, Engineering and Business.
    Löfström, Mikael
    University of Borås, Faculty of Textiles, Engineering and Business.
    Oudhuis, Margaretha
    University of Borås, Faculty of Textiles, Engineering and Business.
    Pal, Rudrajeet
    University of Borås, Faculty of Textiles, Engineering and Business.
    Pettersson, Anita
    University of Borås, Faculty of Textiles, Engineering and Business.
    Påhlsson, Birgitta
    University of Borås, Faculty of Textiles, Engineering and Business.
    Kumar Ramamoorthy, Sunil
    University of Borås, Faculty of Textiles, Engineering and Business.
    Richards, Tobias
    University of Borås, Faculty of Textiles, Engineering and Business.
    Skrifvars, Mikael
    University of Borås, Faculty of Textiles, Engineering and Business.
    Worbin, Linda
    University of Borås, Faculty of Textiles, Engineering and Business.
    Åkesson, Dan
    University of Borås, Faculty of Textiles, Engineering and Business.
    Re: en ny samhällssektor spirar2016Report (Other academic)
    Abstract [sv]

    Resurser och hållbarhet är nära förknippade. Hållbarhet innebär att hushålla med resurser - materiella, miljömässiga och mänskliga. Och hushållning är per definition kärnan i ekonomi. Man börjar alltmer se framväxten av en hel arsenal av verktyg och förhållnings- och angreppssätt för att bygga hållbarhet. Detta förenas av ett synsätt att det som hitintills setts  om avfall och värdelöst, och rent utav besvärligt att ta hand om, nu blir en värdefull resurs. Det glömda och gömda kommer åter. Faktum är att många ord och begrepp kring detta börjar på just åter- eller re- . Internationellt talar man om Redesign, Recycling, Remake, Recycle, Recraft, Reuse, Recreate, Reclaim, Reduce, Repair, Refashion.

    Vad är då allt detta? Ja, vill man dra det långt, är det inte mindre än framväxten av ett nyvunnet sätt att tänka, ja av en ny samhällssektor, en bransch och en industri,  sammanbundet av filosofin att återanvändningen, spillminskningen, vidarebruket, efterlivet anses som viktiga faktorer för ett miljömedvetet samhälle. Re: blir paraplytermen för detta. I denna antologi av forskare från skilda discipliner vid Högskolan i Borås lyfts ett antal av dessa begrepp inom Re: fram.

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  • 10.
    Pettersson, Anita
    University of Borås, School of Engineering.
    Characterisation of Fuels and Fly Ashes from Co-Combustion of Biofuels and Waste Fuels in a Fluidised Bed Boiler. A Phosphorus and Alkali Perspective2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the efforts to create sustainable production of heat and power and to reduce the net CO2 emissions to the atmosphere, alternative fuels are today being utilised. These fuels are, for example, biofuels and waste derived fuels such as different residues from the agricultural sector and the pulp and paper industry, municipal sewage sludge and municipal sorted solid waste. These fuels put new demands on the combustion facilities due to their chemical composition and this in turn calls for methods of prediction for the evaluation of their combustion behaviour. Most significant for the majority of these fuels are the high alkali and chlorine concentrations which cause bed agglomeration, deposit formation and corrosion on heat transfer surfaces. These problems can be solved if sufficient knowledge is obtained of the specific fuel or fuel mix. In this work, chemical fractionation, a step by step leaching method, was used on fuels, fuel mixes and fly ashes from co-combustion in a fluidised bed combustor. In addition, XRD and SEM-EDX were used for the fuel and fly ash characterisation. Different alkali chloride reducing additives i.e. kaolin, zeolites and sulphur were investigated as was the influence of various bed materials: silica sand, olivine sand and blast furnace slag (BFS). Some of the new, alternative fuels, such as municipal sewage sludge and meat and bone meal (MBM) contain high concentrations of phosphorus which is a very important nutrient essential in many biological processes. Phosphorus rock used as raw material in the phosphate industry is a depleting natural resource estimated to last for only 30-200 years according to different sources. The combustion of municipal sewage sludge enriches the phosphorus in the ashes while hazardous components such as pathogens and organic pollutants are rendered harmless after combustion. However, toxic heavy metals are also enriched in the ashes. One aim of the work was to find a sufficiently effective and low cost method for phosphorus extraction from fly ashes derived from municipal sewage sludge combustion. Two types of municipal sewage sludges were investigated using different chemicals for the phosphorus cleaning step in the waste water treatment plants. The first sewage sludge derived from a plant using iron sulphate as flocculant to precipitate phosphorus as iron phosphate. The second sludge meanwhile came from a plant using aluminium sulphate as flocculant to precipitate phosphorus as aluminium phosphate. Both sewage sludges were dewatered prior to combustion and co-combusted with wood pellets. At pH 1 nearly all the phosphorus was released from the fly ash derived from the sewage sludge where aluminium sulphate was used as a phosphorus precipitation agent. Iron sulphate as precipitant inhibited the phosphorus extraction from the ashes, resulting in only 50-80% of the phosphorus being released. Furthermore, the mobility of heavy metals to the leachates was investigated to establish whether the leachates were suitable as fertilisers. Only minor fractions of Pd, Hg, Cr, Cu, Mn, Co, Ni, As, Sb, V and Zn were found in the leachates, all well within the legislated limitations for fertilisers. However, one exception was Cd that was nearly totally dissolved in the leachate. Thus a decadmiation of the leachate is necessary prior to any utilisation of the ashes and reuse of phosphorus as fertiliser.

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  • 11.
    Pettersson, Anita
    et al.
    University of Borås, School of Engineering.
    Elled, Anna-Lena
    University of Borås, School of Engineering.
    Möller, A
    Steenari, B-M
    Åmand, L-E
    The impact of zeolites during co-combustion of municipal sewage sludge with alkali and chlorine rich fuels2009In: Proceedings of the 20th International Conference on Fluidized Bed Combustion, Springer Berlin Heidelberg , 2009, p. 902-909Conference paper (Refereed)
  • 12.
    Pettersson, Anita
    et al.
    University of Borås, School of Engineering.
    Herstad Svärd, Solvie
    Moradian, Farzad
    University of Borås, School of Engineering.
    Slaktavfall och kadaver förbättrar förbränningsmiljön vid avfallsförbränning i BFB-pannor- ett Waste Refinery projekt2012In: Återvinnare för industrin 2012Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Kadaver och visst slakteriavfall är klassat med smittorisk sedan utbrottet av ”galna ko-sjukan” på 1990-talet. Detta betyder att det måste behandlas termiskt t.ex. brännas. I början av 2000-talet togs det därför fram en metod i Sverige för att bearbeta de animaliska restprodukterna till ett biobränsle för energiproduktion. Men vilka krav ställer det på pannorna?

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  • 13.
    Pettersson, Anita
    et al.
    University of Borås, School of Engineering.
    Karlfeldt Fedje, Karin
    Andersson, Sven
    Modin, Oskar
    Frändegård, Per
    Metallutvinning med fokus på Zn från avfallsflygaska med hjälp av sura processvatten, WR582013Report (Other academic)
  • 14.
    Pettersson, Anita
    et al.
    University of Borås, School of Engineering.
    Moradian, Farzad
    University of Borås, School of Engineering.
    Niklasson, Fredrik
    Herstad Svärd, Solvie
    Richards, Tobias
    University of Borås, School of Engineering.
    Examples of Full scale tests on BFB Waste to Energy boilers (WtE) with direct impact on the future operation of the facility2012Conference paper (Other academic)
    Abstract [en]

    The growing problem with municipal solid waste has helped to accelerate de development of Waste to Energy plants (WtE). However, WtE-plants have problems with agglomeration, deposition and corrosion. And at the same time new waste streams are considered for combustion. Co-combustion has sometimes proven to have positive effects on the combustion environment. In this project full scale tests were performed on two twin 20 MWth WtE Bubbling Fluidized Bed (BFB) boilers in Borås, Sweden. The aim of the research was to investigate if a lowered bed temperature by means of flue gas recirculation or addition of animal waste to the normal waste mix (NWM) could improve the boiler performance. The bed temperature was decreased from 870°C, the boiler design temperature, to around 750°C. The animal waste is a pumpable slurry consisting of crushed carcasses and slaughterhouse waste classified with risk of infection because of BSE (Bovine spongiforme encephalopathy or the mad cow disease). The result shoved both decreased deposit formation rate and decreased agglomeration tendency of the bed. And in the case with animal waste addition the NOx emission was reduced with 50% compared to ordinary performance. Furthermore the ammonia addition for NOx reduction was also cut by half in this case.

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  • 15.
    Pettersson, Anita
    et al.
    University of Borås, School of Engineering.
    Niklasson, Fredrik
    Moradian, Farzad
    University of Borås, School of Engineering.
    Comparison of ashes and deposits obtained by RDF combustion in a BR-boiler applying different bed temperatures2010Conference paper (Refereed)
    Abstract [en]

    Chemical fractionation and SEM-EDX was used for characterisation of ashes and deposits from different combustion tests in a commercial 20 MW bubbling fluidized bed (BFB) boiler. The fuel combusted was a mix of sorted MSW (Municipal Solid Waste) and industrial waste often referred to as RDF (Refuse Derived Fuel) mostly containing combustible material as paper, plastics and wood. This fuel type often contains a lot of alkali and chlorine and is therefore considered as a risk fuel prone to cause bed agglomeration, deposit formation and corrosion. In order to investigate the impact of the bed temperature on the alkali and chlorine distribution in the boiler combustion tests were performed. The bed temperature for this boiler is designed to be in the range 850-900°C. In this investigation however the bed temperature was reduced to 700-750°C. Two deposit probes, each carrying two rings made of high alloy steel, were used for collection of deposits during combustion. In addition, samples taken on the bed ash, return sand, return shaft ash, cyclone ash and textile filter ash were analysed. By reducing the bed temperature the need for fresh bed sand was reduced and the fly ash flow decreased. In addition, the agglomerates found in the tests with the normal bed temperature disappeared totally when the bed temperature was reduced. The deposits formed on the bed ash and on the return sand particles were found to consist of compounds with melting temperatures between 675 and 801C, which could explain the difference in agglomeration tendency.

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  • 16.
    Pettersson, Anita
    et al.
    University of Borås, School of Engineering.
    Niklasson, Fredrik
    Moradian, Farzad
    University of Borås, School of Engineering.
    Reduced bed temperature in a commercial waste to energy boiler: Impact on ash and deposit formation2013In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 105, p. 28-36Article in journal (Refereed)
    Abstract [en]

    Waste combustion for power production is associated with many problems due to the composition and inhomogeneity of the fuel stream. A reduction of alkaline and chlorine products in the superheater region should ease these problems significantly. Ashes and deposits from different combustion tests in a commercial 20 MWth bubbling fluidised bed (BFB) boiler were characterised by XRD and SEM-EDX. The fuel combusted was a mix of sorted municipal solid waste (MSW) and industrial waste, often referred to as RDF (refuse derived duel). These waste fuels often contain more alkali and chlorine than does biomass and are therefore considered risky fuels prone to causing bed agglomeration, deposit formation, and corrosion. The aim of this study was to investigate whether a lowered bed temperature could change alkali and chlorine distribution in the boiler to reduce corrosion and deposit formation. The boiler used was designed for a bed temperature in the range of 850–900 °C, which in this investigation was decreased by approximately 150 °C. Data were collected through deposit measurements and solid sampling. The lowered bed temperature resulted in reduced demand for fresh sand, decreased agglomeration, and reduced rates of deposit formation.

  • 17.
    Pettersson, Anita
    et al.
    University of Borås, School of Engineering.
    Zevenhoven, Maria
    Steenari, Britt-Marie
    Åmand, Lars-Erik
    Application of chemical fractionation methods for characterisation of biofuels, waste derived fuels and CFB co-combustion fly ashes2008In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 87, no 15-16, p. 3183-3193Article in journal (Refereed)
    Abstract [en]

    In the important efforts to decrease the net CO2 emissions to the atmosphere, new, alternative fuels are being included in the fuel mixes used in utility boilers. However, these fuels have ash properties that are different from those of the traditionally used fuels and in some cases technical problems, such as ash fouling and corrosion occur due to this. Therefore, diagnostic and predictive methods are developed and used to avoid such problems. Determination of the chemical association forms of important elements, such as potassium and sodium, in the fuel by chemical fractionation is a method well defined for coal and biofuels, such as wood pellets, bark and forest residues. Chemical fractionation is a step by step leaching method extracting water soluble salts in the first step, ion exchangeable elements, such as organically associated sodium, calcium and magnesium in the second step and acid soluble compounds such as carbonates and sulfates in the third step. The solid residue fraction consists of silicates, oxides, sulfides and other minerals. The compound extracted in the two first steps is considered reactive in the combustion with a few exceptions. In this work, it has been applied to some waste fuels, i.e. sewage sludge, straw and refuse derived fuel (RDF), as well as to coal and wood. The present work also includes results from combustion tests in a fluidised bed boiler where three blends of the investigated fuels were used. The fractionation results for the fuel blends are weighted results of the fractionations of the pure fuels discussed above which are compared with fractionations of their corresponding fly ashes. The co-combustion strategy gave very good results in reducing ash problems. Possible chemical mechanisms involved are discussed in the article.

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  • 18.
    Pettersson, Anita
    et al.
    University of Borås, School of Engineering.
    Åmand, Lars-Erik
    Steenari, Britt-Marie
    Chemical fractionation for the characterisation of fly ashes from co-combustion of biofuels using different methods for alkali reduction2009In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 88, no 9, p. 1758-1772Article in journal (Refereed)
    Abstract [en]

    Chemical fractionation, SEM-EDX and XRD was used for characterisation of fly ashes from different co-combustion tests in a 12 MW circulating fluidized bed boiler. The fuels combusted were wood pellets as base fuel and straw pellets as co-fuel in order to reach a fuel blend with high alkali and chlorine concentrations. This fuel blend causes severe problems with both agglomeration of bed material if silica sand is used and with deposits in the convection section of the boiler. Counter measures to handle this situation and avoiding expensive shut downs, tests with alternative bed materials and additives were performed. Three different bed materials were used; silica sand, Olivine sand and blast furnace slag (BFS) and different additives were introduced to the furnace of the boiler; Kaolin, Zeolites and Sulphur with silica sand as bed material. The results of the study are that BFS gives the lowest alkali load in the convection pass compared with Silica and Olivine sand. in addition less alkali and chlorine was found in the fly ashes in the BFS case. The Olivine sand however gave a higher alkali load in the convection section and the chemical fractionation showed that the main part of the alkali in the fly ashes was soluble, thus found as KCl which was confirmed by the SEM-EDX and XRD. The comparison of the different additives gave that addition of Kaolin and Zeolites containing aluminium-silicates captured 80% of the alkali in the fly ash as insoluble alkali-aluminium-silikates and reduced the KCl load on the convection section. Addition of sulphur reduced the KCl load in the flue gas even more but the K2SO4 concentration was increased and KCl was found in the fly ashes anyhow. The chemical fractionation showed that 65% of the alkali in the fly ashes of the Sulphur case was soluble. (C) 2009 Elsevier Ltd. All rights reserved.

  • 19.
    Pettersson, Anita
    et al.
    University of Borås, School of Engineering.
    Åmand, Lars-Erik
    Steenari, Britt-Marie
    Leaching of ashes from co-combustion of sewage sludge and wood, Part I: Recovery of phosphorus2008In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 32, no 3, p. 224-235Article in journal (Refereed)
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  • 20.
    Pettersson, Anita
    et al.
    University of Borås, School of Engineering.
    Åmand, Lars-Erik
    Steenari, Britt-Marie
    Leaching of ashes from co-combustion of sewage sludge and wood-Part II: The mobility of meatals during phosphorus extraction2008In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 32, no 3, p. 236-244Article in journal (Refereed)
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  • 21.
    Tchoffor, Placid
    et al.
    SP Technical Research Institute of Sweden, SE-501 15 Borås, Sweden.
    Moradian, Farzad
    University of Borås, Faculty of Textiles, Engineering and Business.
    Pettersson, Anita
    University of Borås, Faculty of Textiles, Engineering and Business.
    Kent, Davidsson
    SP Technical Research Institute of Sweden, SE-501 15 Borås, Sweden.
    Thunman, Henrik
    Chalmers University of Technology, 412 58 Gothenburg, Sweden.
    Influence of Fuel Ash Characteristics on the Release of Potassium, Chlorine, and Sulfur from Biomass Fuels under Steam-Fluidized Bed Gasification Conditions2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, p. 10435-10442Article in journal (Refereed)
    Abstract [en]

    Steam-fluidized bed gasification of biomass, which produces combustible gases from which transportation fuels can be synthesized, is a promising option for replacing the use of fossil fuels in the transportation sector. Similar to other thermal conversion processes, the release of potassium (K), chlorine (Cl), and sulfur (S) from biomass fuels to the gas phase during this process may be conducive to ash-related problems. Catalytic tar and char conversion by K has also been observed. In addition to operational conditions, the extent to which these elements are released to the gas phase may be affected by fuel ash characteristics such as the ash composition and the speciation (or association) of ash-forming elements in the fuel matrix. In the present work, the influence of these fuel ash characteristics on the extent to which K, Cl, and S are released from biomass fuels to the gas phase was studied under steam-fluidized bed gasification. The aim was to assess whether these fuel ash characteristics provide information that could be useful in making a quick judgment as to what extent K, Cl, and S would be released to the gas phase. To this end, the release of K, Cl, and S from forest residues and wheat straw during devolatilization and steam gasification of the char was quantified in a laboratory-scale bubbling fluidized bed reactor. The speciation of these elements in the virgin fuels was studied with chemical fractionation. The results reveal that the extent to which S is released from biomass fuels to the gas phase mainly depends on its speciation in the fuel matrix. While both the ash composition (mainly the Cl/K molar ratio) of the fuel and the speciation of K in the fuel matrix are relevant for the release of K, they appear to be unimportant with respect to the release of Cl.

  • 22.
    Usino, David
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Supriyanto, Supriyanto
    University of Borås, Faculty of Textiles, Engineering and Business.
    Ylitervo, Päivi
    University of Borås, Faculty of Textiles, Engineering and Business.
    Pettersson, Anita
    University of Borås, Faculty of Textiles, Engineering and Business.
    Richards, Tobias
    University of Borås, Faculty of Textiles, Engineering and Business.
    Influence of temperature and time on initial pyrolysis of cellulose and xylan2020In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. Volume 147, no 104782Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate the effects of temperature and reaction time on the primary pyrolysis of cellulose and xylan. Fast pyrolysis of cellulose and xylan was carried out with a micropyrolyser connected to a gas chromatograph-mass spectrometer/flame ionisation detector (GC–MS/FID) to separate and identify volatile components, both qualitatively and quantitatively. This set-up meant a minimum amount of secondary reactions, low impact of the heating period and at the same time provided rapid and accurate analyses. The two biomass components investigated were: cellulose and hemicellulose (represented by xylan). They were pyrolysed during 0.5, 1, 2 and 5 s (s) and within a temperature range of 400–600 °C. The results showed that levoglucosan (1, 6-anhydro β-D-glucopyranose) is the main chemical compound released during cellulose pyrolysis. It increased with increasing temperature and time. The main volatile compounds produced from pyrolysis of xylan are: 1-hydroxy-2-butanone, 4-hydroxy-5, 6-dihydro-(2 H)-pyran-2-one, 1-hydroxy-2-propanone (acetol), acetaldehyde and hydroxyacetaldehyde (HAA). HAA was the most abundant chemical compound released during xylan pyrolysis, increasing with higher temperatures and time. Acetol and acetaldehyde also showed similar behaviour. The chemical compounds released from cellulose and xylan fast pyrolysis are primary products and assumed to be produced directly from both cellulose and xylan molecules and not from secondary degradation. In this study, possible reaction routes during biomass primary pyrolysis are also suggested based on the product distribution from the thermal decomposition of cellulose and xylan.

  • 23.
    Vali, Naeimeh
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Combres, Aurélie
    University of Borås, Faculty of Textiles, Engineering and Business.
    Hosseinian, Aida
    Water, Energy and Environmental Engineering Research Unit, Faculty of Technology, University of Oulu, 90014 Oulu, Finland.
    Pettersson, Anita
    University of Borås, Faculty of Textiles, Engineering and Business.
    The Effect of the Elemental Composition of Municipal Sewage Sludge on the Phosphorus Recycling during Pyrolysis, with a Focus on the Char Chemistry—Modeling and Experiments2023In: Separations, E-ISSN 2297-8739, Vol. 10, no 1, article id 31Article in journal (Refereed)
    Abstract [en]

    The present study investigates how the original sewage sludge characteristics influence the composition of sewage sludge-based chars for land applications. Sewage sludge from two different wastewater treatment plants in Sweden was pyrolyzed at 500, 700, and 900 °C, and the resulting chars were analyzed. Thermodynamic equilibrium calculations (TEC), together with chemical fractionation, were implemented to simulate the char after the pyrolysis process at different temperatures. The results showed that, in general, for both the municipal sewage sludge (MSS), phosphorus (P) was significantly retained in the char at various temperatures. However, no specific correlation could be found between the pyrolysis temperature and the amount of P remaining. With regard to the heavy metals removed from the char after the pyrolysis reaction, the concentrations of copper, chromium, lead, nickel, zinc, and cadmium were below the limits of the Swedish regulations for farmland application.

     

      

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  • 24.
    Vali, Naeimeh
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Åmand, Lars-Erik
    University of Borås, Faculty of Textiles, Engineering and Business.
    Combres, Aurélie
    Richards, Tobias
    University of Borås, Faculty of Textiles, Engineering and Business.
    Pettersson, Anita
    University of Borås, Faculty of Textiles, Engineering and Business.
    Pyrolysis of municipal sewage sludge to investigate char and phosphorous yield together with heavy-metal removal—experimental and by thermodynamic calculations2021In: Energies, E-ISSN 1996-1073, Vol. 14, no 5, article id 1477Article in journal (Refereed)
    Abstract [en]

    Sewage sludge is regarded as a potential source for soil fertilizer However, the direct utilization of sewage sludge in agricultural land is restricted since it also contains heavy metals, pathogens, and toxic compounds. Pyrolysis of the sewage sludge destroys the organic pollutants and partly volatilizes the heavy metals. In this study, pyrolysis of sewage sludge was carried out in order to determine the optimum residence time and temperature to recover the phosphorous and remove heavy metals from the resultant sewage sludge char (SSC). Pyrolysis was conducted on dried sewage sludge (DSS) by means of thermogravimetric analysis (TGA) and high-temperature oven with an N2-atmosphere. Microwave Plasma-Atomic Emission Spectroscopy (MP-AES) was used to determine the concentration of P and trace elements in the resulting solid char fraction. A combination of chemical fractionation (step-by-step leaching) of the DSS and thermodynamic equilibrium calculations were utilized to estimate the availability of phosphorous and removal of heavy metals in the SSC fraction at different temperatures. The results from the thermodynamics calculation were in line with the measured chemical composition of the SSC. Furthermore, the energy contents of the SSC obtained at different temperatures were measured. The pyrolysis evaluation results indicate that phosphorous was enriched in the char, while lead, zinc, and cadmium were significantly removed.

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