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  • 1.
    Claesson, Frida
    et al.
    University of Borås, School of Engineering.
    Skrifvars, B-J
    Elled, Anna-Lena
    University of Borås, School of Engineering.
    Johansson, A
    Chemical characterization of waste fuel for fluidized bed combustion2009Conference paper (Refereed)
    Abstract [en]

    Combustible waste is very heterogeneous and the variation in chemical composition is of great significance for the performance of the combustors in terms of boiler availability and power efficiency. For example, the content of alkali, Chlorine and sulfur affect agglomeration, fouling and corrosion mechanisms, which often limits the steam data and requires counteracts such as soot blowing and outages. An increased knowledge on favorable levels and ratios of fuel components are therefore highly important when developing waste combustors, both existing and future. However, to be able to make good predictions of reactions, reliable fuel analyses are a necessity and they are difficult to perform because of the heterogeneity of waste. As a consequence, it is also difficult to complete pro-active measure to reduce unwanted reactions. This work has investigated the composition of the fuel during one year in a 40 MW commercial BFB waste plant. Twelve samples have been performed in order to estimate the variation of key components. The fuel samples were analyzed chemically for alkali and several other components of interest, such as Cl and S. Moreover, thermo-chemical multi-phase equilibrium calculations were performed for prediction of the chemical composition of the furnace in the temperature range 400-1000 ºC. In this temperature range NaCl and PbClx are formed as well as gas phase HCl and solid silicates. Furthermore, the calculations show that the chemistry is very sensitive to the input chemical composition, suggesting that already a minor shift in fuel mineral matter may change the behavior of the fuel radically in terms of its fouling and corrosion tendency.

  • 2.
    Dahlby, Mikael
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Gustafson Sjöberg, Robin
    University of Borås, Faculty of Textiles, Engineering and Business.
    Studie av ventilation i simhall: Med fokus på klorbaserade luftföroreningar2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Public baths contributes significantly to the promotion of public health and wellbeing. To be able to supply a pleasant experience for bathers, a high quality of water and air is required. To avoid spreading of pathogens between bathers, Chlorine is used as a central component for disinfecting the water. Chlorine residues such as Trichloramine affect human health and are concentrated above the water surface and will remain in the breathing zone unless the pollution is carried away by air movement.Nolhaga public bath is undergoing a renovation and this report is a study of the new ventilation system which has been installed. To investigate the air flow pattern in the hall a CAD model of the space was created. CFD software was used to simulate airflow in the model. Results have also been compared with a smoke test, performed in a similar building. In addition to the suggested solution a different approach, with additional exhaust air vents placed at floor level, has been tested.The results show that the air speeds over the water surface are within the given recommendations. The air has a tendency to move around in the room with a recirculating behaviour where the supply air follows the roof to the back wall and then returns over the surface of the water. This kind of behaviour might be beneficial for removing Trichloramines if exhaust air vents are placed near the air supply units. This method uses the air movement to remove pollutants where the concentration is highest and removes them from the building. Performed smoke test gave only vague indications that the simulation results can be linked to actual air movement due to the small amount of information it provided.Due to the lack of time, knowledge and experience in the field, the uncertainty of the achieved results is great. Additional work in CFD and ventilation of public baths is required to enhance credibility of results.

  • 3. Davidsson, K.O.
    et al.
    Åmand, L.-E.
    Elled, A.-L.
    University of Borås, School of Engineering.
    Leckner, B.
    Effect of Cofiring Coal and Biofuel with sewage Sludge on Alkali Problems in a Circulating Fluidized Bed Boilder2007In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 21, no 6, p. 3180-3188Article in journal (Refereed)
    Abstract [en]

    Cofiring experiments were performed in a 12 MW circulating fluidized bed boiler. The fuel combinations were biofuel (wood+straw), coal+biofuel, coal+sewage sludge+biofuel, and sewage sludge+biofuel. Limestone or chlorine (PVC) was added in separate experiments. Effects of feed composition on bed ash and fly ash were examined. The composition of flue gas was measured, including on-line measurement of alkali chlorides. Deposits were collected on a probe simulating a superheater tube. It was found that the fuel combination, as well as addition of limestone, has little effect on the alkali fraction in bed ash, while chlorine decreases the alkali fraction in bed ash. Sewage sludge practically eliminates alkali chlorides in flue gas and deposits. Addition of enough limestone to coal and sludge for elimination of the SO2 emission does not change the effect of chlorine. Chlorine addition increases the alkali chloride in flue gas, but no chlorine was found in the deposits with sewage sludge as a cofuel. Cofiring of coal and biofuel lowers the alkali chloride concentration in the flue gas to about a third compared with that of pure biofuel. This is not affected by addition of lime or chlorine. It is concluded that aluminum compounds in coal and sludge are more important than sulfur to reduce the level of KCl in flue gas and deposits.

  • 4. Davidsson, K.O.
    et al.
    Åmand, L.-E.
    Steenari, B.-M.
    Elled, A.-L.
    University of Borås, School of Engineering.
    Eskilsson, D.
    Leckner, B.
    Countermeasures against alkali-related problems during combustion of biomass in a circulating fluidized bed boiler2008In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 63, no 21, p. 5314-5329Article in journal (Refereed)
    Abstract [en]

    The purpose of this work was to study different ways to mitigate alkali-related problems during combustion of biomass in circulating fluidized beds. Wood chips and wood pellets were fired together with straw pellets, while the tendency to agglomerate and form deposits was monitored. In addition to a reference case, a number of countermeasures were applied in related tests. Those were addition of elemental sulphur, ammonium sulphate and kaolin to a bed of silica sand, as well as use of olivine sand and blast-furnace slag as alternative bed materials. The agglomeration temperature, composition and structure of bed-ash samples were examined. The flue-gas composition, including gaseous alkali chlorides, was measured in the hot flue gases and in the stack. Particles in the flue gas were collected and analysed for size distribution and composition. Deposits were collected on a probe in hot flue gases and their amount and composition were analysed. Addition of kaolin was found to be the best method to counteract the agglomeration problem. The deposition problem is effectively counteracted with addition of ammonium sulphate, while kaolin is too expensive to be used commercially against deposits, and sulphur is less effective than ammonium sulphate.

  • 5.
    Dessne, Petter
    et al.
    University of Borås, School of Business and IT.
    Fachina, Vicente
    University of Borås, School of Business and IT.
    Golmen, Lars G.
    University of Borås, School of Business and IT.
    Miller, Alan K.
    University of Borås, School of Business and IT.
    Panchal, C. B.
    University of Borås, School of Business and IT.
    Hammar, Linus
    University of Borås, School of Business and IT.
    Jamaluei, Zahra Yadali
    University of Borås, School of Business and IT.
    Duckers, Les
    University of Borås, School of Business and IT.
    Blanchard, Richard
    University of Borås, School of Business and IT.
    Banerjee, Subhashish
    University of Borås, School of Business and IT.
    Baird, Jim
    University of Borås, School of Business and IT.
    Johnson, Ted
    University of Borås, School of Business and IT.
    Bharathan, Desikan
    University of Borås, School of Business and IT.
    Lever, Harold
    University of Borås, School of Business and IT.
    Yu, Jason C. S.
    University of Borås, School of Business and IT.
    Chen, W.
    University of Borås, School of Business and IT.
    OTEC matters 20152015Report (Other academic)
    Abstract [en]

    For mankind as a whole, and in many respects, the world is becoming a better place each year. In both rich and poor countries the standard of living has improved steadily for a very long time. This progress has a serious drawback, the negative effects on Earth’s climate. It is clear that the only way we can live sustainably is by consuming much less. However, this is not enough: there is an undeniable need for new energy sources. As the world’s population grows, many countries will also face more severe shortages of food and of fresh, disease-free water. Most developing countries are situated in tropical regions and are therefore hit hard by increasing tropical storms and similar weather-based disasters, adding to these problems. Ocean Thermal Energy Conversion (OTEC) technology has been proven to be an ideal candidate for addressing and resolving all of these problems for small island developing states (SIDS), and a few months ago, the EU set aside€72 million euros for constructing OTEC plants outside Martinique. Built on a much larger scale, OTEC can, as the only technology known to man, supply the world with its total energy and fresh water needs, increase seafood production many times over, and cooling off parts of the sea surface when they become too hot – all this without any atmospheric emissions. Thus, it is with great excitement that this very first issue of the only journal dedicated to OTEC is being published. The publication covers many facets of OTEC and related matters, such as OTEC technology, sustainability including gender and other social studies, renewable energy, marine biology, metallurgy, and research on developing countries. The publication is aimed at two different audiences, scientists directly or indirectly involved with OTEC technology, and a more diverse group of people consisting of scientists from non-technical fields, industry people, politicians, investors, educators, and more. This volume is published as part of the publication series of the University of Borås, a progressive Swedish university with a high interest in and knowledge about sustainability.

  • 6.
    Dessne, Petter
    et al.
    University of Borås, School of Business and IT.
    Golmen, Lars
    Johnson, Ted
    Bharathan, Desikan
    Lever, Harold
    Ny havsteknik kan lösa miljöproblem2014In: Svenska Dagbladet, ISSN 1101-2412, no 2014-02-08Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Debattartikel som förespråkar miljötekniken OTEC för att förse stora delar av världen med energi och färskvatten.

  • 7.
    Eboh, Francis Chinweuba
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Ahlström, Peter
    University of Borås, Faculty of Textiles, Engineering and Business.
    Richards, Tobias
    University of Borås, Faculty of Textiles, Engineering and Business.
    Estimating the specific chemical exergy of municipal solid waste2016In: Energy Science & Engineering, ISSN 2050-0505, Vol. 4, no 3, p. 217-231Article in journal (Refereed)
  • 8.
    Eboh, Francis Chinweuba
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business. Resource Recovery.
    Ahlström, Peter
    Richards, Tobias
    Estimating the specific exergy of municipal solid waste2016In: Energy Science & Engineering, ISSN 2050-0505, Vol. 4, no 3, p. 217-231Article in journal (Refereed)
    Abstract [en]

    A new model for predicting the specific chemical exergy of municipal solid waste (MSW) is presented; the model is based on the content of carbon, hydrogen, oxygen, nitrogen, sulfur, and chlorine on a dry ash-free basis (daf). The proposed model was obtained from estimations of the higher heating value (HHV) and standard entropy of MSW using statistical analysis. The ultimate analysis of 56 different parts of MSW was used for the derivation of the HHV expression. In addition, 30 extra parts were used for validation. One hundred and seventeen relevant organic substances that represented the main constituents in MSW were used for derivation of the standard entropy of solid waste. The substances were divided into different waste fractions, and the standard entropies of each waste fraction and for the complete mixture were calculated. The specific chemical exergy of inorganic matter in the waste was also investigated by considering the inorganic compounds in the ash. However, as a result of the extremely low value calculated, the exergy of inorganic matter was ignored. The results obtained from the HHV model show a good correlation with the measured values and are comparable with other recent and previous models. The correlation of the standard entropy of the complete waste mixture is less accurate than the correlations of each individual waste fraction. However, the correlations give similar results for the specific chemical exergy, indicating that HHV has a greater impact when estimating the specific exergy of solid waste than entropy.

  • 9.
    Eboh, Francis Chinweuba
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business. Swedish Centre for Resource Recovery.
    Ahlström, Peter
    University of Borås, Faculty of Textiles, Engineering and Business. Swedish Centre for Resource Recovery.
    Richards, Tobias
    University of Borås, Faculty of Textiles, Engineering and Business. Swedish Centre for Resource Recovery.
    Exergy Analysis of Solid Fuel-Fired Heat and Power Plants: A Review2017In: Energies, ISSN 1996-1073, E-ISSN 1996-1073Article in journal (Refereed)
    Abstract [en]

    The growing demand for energy is particularly important to engineers with respect to how the energy produced by heat and power plants can be used efficiently. Formerly, performance evaluation of thermal power plants was done through energy analysis. However, the energy method does not account for irreversibilities within the system. An effective method to measure and improve efficiency of thermal power plant is exergy analysis. Exergy analysis is used to evaluate the performance of a system and its main advantage is enhancement of the energy conversion process. It helps identify the main points of exergy destruction, the quantity and causes of this destruction, as well as show which areas in the system and components have potential for improvements. The current study is a comprehensive review of exergy analyses applied in the solid fuels heat and power sector, which includes coal, biomass and a combination of these feedstocks as fuels. The methods for the evaluation of the exergy efficiency and the exergy destruction are surveyed in each part of the plant. The current review is expected to advance understanding of exergy analysis and its usefulness in the energy and power sectors: it will assist in the performance assessment, analysis, optimization and cost effectiveness of the design of heat and power plant systems in these sectors.

  • 10.
    Eboh, Francis Chinweuba
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Ahlström, Peter
    University of Borås, Faculty of Textiles, Engineering and Business.
    Richards, Tobias
    University of Borås, Faculty of Textiles, Engineering and Business.
    Method of Estimating Absolute Entropy of Municipal Solid Waste2016In: World Academy of Science, Engineering and Technology, International Journal of Environmental, Chemical, Ecological, Geological and Geophysical Engineering, E-ISSN 2010-3778, Vol. 10, no 7, p. 689-694Article in journal (Refereed)
    Abstract [en]

    Entropy, as an outcome of the second law of thermodynamics, measures the level of irreversibility associated with any process. The identification and reduction of irreversibility in the energy conversion process helps to improve the efficiency of the system. The entropy of pure substances known as absolute entropy is determined at an absolute reference point and is useful in the thermodynamic analysis of chemical reactions; however, municipal solid waste (MSW) is a structurally complicated material with unknown absolute entropy. In this work, an empirical model to calculate the absolute entropy of MSW based on the content of carbon, hydrogen, oxygen, nitrogen, sulphur, and chlorine on a dry ash free basis (daf) is presented. The proposed model was derived from 117 relevant organic substances which represent the main constituents in MSW with known standard entropies using statistical analysis. The substances were divided into different waste fractions; namely, food, wood/paper, textiles/rubber and plastics waste and the standard entropies of each waste fraction and for the complete mixture were calculated. The correlation of the standard entropy of the complete waste mixture derived was found to be somsw= 0.0101C + 0.0630H + 0.0106O + 0.0108N + 0.0155S + 0.0084Cl (kJ.K-1.kg) and the present correlation can be used for estimating the absolute entropy of MSW by using the elemental compositions of the fuel within the range of 10.3%  C 95.1%, 0.0%  H  14.3%, 0.0%  O  71.1%, 0.0  N  66.7%, 0.0%  S  42.1%, 0.0%  Cl  89.7%. The model is also applicable for the efficient modelling of a combustion system in a waste-to-energy plant.

  • 11.
    Elled, A.-L.
    University of Borås, School of Engineering.
    Combustion of sludge with wood in a fluidised bed boiler- the fate of trace elements and sulphur performance2005Report (Other academic)
  • 12.
    Elled, Anna-Lena
    University of Borås, School of Engineering.
    Co-combustion of biomass and waste fuels in a fluidised bed boiler: fuel synergism2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The objective of this work was to study co-combustion of biomass and waste fuels in a circulating fluidised bed boiler and to detect synergy effects with respect to flue gas composition and ash formation during boiler operation. It was also the aim to perform supplementary thermodynamic equilibrium calculations in order to support the experimental results. The base fuel used was either wood or bark pellets and the additional fuels included municipal sewage sludge, sludge from the pulp and paper industry and demolition wood. In some of the tests, additives were supplied to the boiler to enhance any effects from substances of special interest. Examples of such additives are zinc oxide, PVC, ammonium sulphate, kaolin and zeolites. The 12 MWth circulating fluidised bed boiler situated at Chalmers University of Technology was central to the investigation. All combustion tests were performed in this boiler and it provided operating data, flue gas composition and samples of fuel, ash and deposits under required combustion conditions. Great effort was put into the analyses of ashes and deposits and in excess of conventional techniques, time-of-flight secondary ion mass spectrometer (TOF-SIMS), scanning electron microscopy energy dispersive x-ray (SEM EDX) and x-ray diffraction (XRD) were applied to several of the samples to create a more complete scan of the constituents. The thermodynamic equilibrium calculations were performed using the computer program FactSage and the module EQUILIB. The thermodynamic data was collected from the database FACT. The focus of the investigation was directed towards three main areas: sulphur capture performance by lime addition to the bed, distribution of heavy metals in ashes and flue gas, and formation of deposits on heat transfer surfaces in the convective pass and the use of municipal sewage sludge as a preventive additive. The relatively high content of phosphorus in municipal sewage sludge interferes with the sulphur capture by lime and decreases the sulphur capture performance. Phosphorus reacts with calcium, which otherwise is available for reaction with sulphur, and forms compounds such as calcium phosphates. The formation was supported by equilibrium calculations and proved by analysing the ashes with TOF-SIMS. The decreased lime efficiency must be taken into account when sulphur capture strategies are decided for the reduction of SO2 emissions from co-combustion of municipal sewage sludge. Further, the use of bark pellets as base fuel during co-combustion with sulphur containing wastes reduces the sulphur emissions due to their relatively high content of calcium and potassium in connection with its low content of sulphur. The supply of heavy metals to the combustion increases dramatically when wood is replaced by municipal sewage sludge under otherwise constant conditions. The heavy metals are to a large extent recovered in the ash and captured by the flue gas cleaning system. Even the most volatile species, such as mercury, are captured and enriched in the fine fly ash. The effective metal capture is partly due to the sludge ash and partly to the bag filter. The amount of ash in the boiler increases with the sludge and the fine fly ash fraction constitutes a high particle surface area which enhances the capture of volatile metals. Further, the ash contains large amounts of several elements known to retain trace elements such as aluminium, calcium, carbon and silicon. Especially the presence of zeolites in the sludge is likely to contribute to the capture of mercury. Further, the enrichment ratios of metals in the filter ash indicate the necessity of including bag-filters in the flue gas cleaning system in order to achieve sufficient removal of toxic heavy metals. Zinc, and its effect on deposit formation, was given special attention since the metal is commonly present in demolition wood. The result showed that combustion of demolition wood contaminated with zinc alone generates only a modest amount of deposits. Demolition wood contaminated with both zinc and chlorine gives rise to more severe deposit formation. The main reason for this is the formation of alkali chlorides but also zinc chlorides in the flue gas. The formation of zinc chlorides is, under reducing conditions, thermodynamically favoured between 450 and 850°C. Under oxidising conditions, the formation is initiated at 400°C and gradually increased with the temperature. Municipal sewage sludge is not only a waste that must be disposed of, it can also be regarded as an additive to prevent deposit formation during combustion of high alkali biomass. The sludge reduces the concentration of KCl in the flue gas, impedes the deposit formation and eliminates the content of chlorine in the deposits. The occurrence is clear of though the fuel is contaminated with chlorine. The effect is partly due to sulphation of potassium and partly to potassium sequestration by the sludge ash.

  • 13.
    Elled, Anna-Lena
    et al.
    University of Borås, School of Engineering.
    Åmand, Lars-Erik
    University of Borås, School of Engineering.
    Andersson, Bengt-Åke
    University of Borås, School of Engineering.
    Leckner, B.
    University of Borås, School of Engineering.
    Phosphorus in ash from co-combustion of municipal sewage sludge with wood in a CFB boiler: A comparison of experimental data with predictions by a thermodynamic equilibrium model2005Conference paper (Refereed)
    Abstract [en]

    Combustion tests have been carried out in a circulating fluidised bed (CFB) boiler co-firing wood and municipal, digested and mechanical dewatered sewage sludge from two Swedish wastewater treatment plants, using either iron sulphate or aluminium sulphate as precipitating chemicals. Experimental data on the concentration of various phosphorous compounds in the ashes are compared with theoretical equilibrium predictions. A clear relationship is not found between the employed precipitation chemical and the formation of phosphorous compounds in the ash. Hematite (Fe2O3(s)) is predicted to be the stable iron compound, and even in the sludge precipitated by iron sulphate, the aluminium content is sufficient to form aluminium phosphate (AlPO4(s)) in similar amounts as in the sludge precipitated by aluminium sulphate. Lime addition to the bed gives a decreased formation of AlPO4(s) in favour of calcium orthophosphate (Ca3(PO4)2(s)), which interferes with the sulphur capture efficiency of lime.

  • 14.
    Elled, Anna-Lena
    et al.
    University of Borås, School of Engineering.
    Åmand, Lars-Erik
    Eskilsson, David
    The fate of zinc during combustion of demolition wood in a fluidized bed boiler2007In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 22, no 3Article in journal (Refereed)
    Abstract [en]

    Demolition wood can be used as a fuel in heat and power plants. However, it may contain elevated amounts of zinc, originating from white paint, which can cause problems related to deposit formation and corrosion on heat transfer surfaces. In this work, combustion tests with zinc addition were carried out in a fluidized bed boiler to investigate its effect on deposit formation. Thermodynamic equilibrium calculations were performed to complement the experimental data. The results show that combustion of demolition wood only contaminated with zinc generates a modest amount of deposit. Combustion of demolition wood contaminated with both zinc and chlorine promotes the deposit formation due to the increased amount of submicron particles in the flue gas. The thermodynamic equilibrium analyses show further that reducing conditions increase the release of zinc to the flue gas. On the other hand, in the case of oxidizing conditions, the retention of zinc in the ash is strong. Zinc, in combination with chlorine, gives rise to formation of zinc chloride in the flue gas. The formation is, at reducing conditions, thermodynamically favored between 450 and 850 °C. At oxidizing conditions, the formation is initiated at 400 °C and gradually increased with the temperature.

  • 15.
    Elled, Anna-Lena
    et al.
    University of Borås, School of Engineering.
    Åmand, Lars-Erik
    Leckner, Bo
    Andersson, Bengt-Åke
    University of Borås, School of Engineering.
    The fate of trace elements in fluidised bed combustion of sewage sludge and wood2006In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 86, no 5-6, p. 843-852Article in journal (Refereed)
    Abstract [en]

    Combustion tests have been carried out in a fluidised bed boiler to investigate the fate of trace elements during co-combustion of wood and municipal sewage sludge. The approach was to collect fuel and ash samples and to perform thermodynamic equilibrium calculations for gasification (reducing) and combustion (oxidising) conditions. Trace elements are found in the ash. Even most of the highly volatile Hg is captured in the bag filter ash. The bag filter ash offers higher surface area than the secondary cyclone ash and enhances the capture of Hg. There is no obvious correlation between capture and parameters investigated (sludge precipitation agent and lime addition). As, Cd, Hg, Pb, Se, Sb and Tl are predicted by equilibrium calculations to be volatile in the combustion chamber under oxidising conditions and Hg even at the filter temperature (150°C). Reducing conditions promote, in some case more than others, the volatility of As, Cd, Pb, Sb, Se, Tl and Zn. The opposite effect was observed for Cu and Ni. Data points to the necessity of including bag-filter in the gas cleaning system in order to achieve good removal of toxic trace elements.

  • 16.
    Elled, Anna-Lena
    et al.
    University of Borås, School of Engineering.
    Åmand, L.-E.
    Leckner, B.
    Andersson, Bengt-Åke
    University of Borås, School of Engineering.
    Influence of phosphorus on sulphur capture during co-firing of sewage sludge with wood or bark in a fluidised bed2006In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 85, no 12, p. 1671-1678Article in journal (Refereed)
    Abstract [en]

    Interference from phosphorus on sulphur capture during co-firing of sludge with wood has been investigated in a circulating fluidised bed boiler. Chemical equilibrium analyses were performed on the combustion system to complement the experimental results. It was found that the relatively high content of phosphorus in municipal sewage sludge interferes with the sulphur capture by occupying calcium, which otherwise would be available for reaction with sulphur. This fact must be taken into account when sulphur capture strategies are decided for reduction of sulphur dioxide emissions from sewage sludge as an additional fuel.

  • 17.
    Ericsson, Daniel
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Lagergren, Ida
    University of Borås, Faculty of Textiles, Engineering and Business.
    Lutens kretslopp på Södra Cell Värö2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Rapporten handlar om lutens kretslopp på Södra Cell Värö, dess betydelse för pappersmassaproduktionen samt riskerna som finns vid användning av lut. Lut används när pappersmassa framställs på Södra Cell Värö (sulfatprocess). Kokeriet kokar träflis, tunnlut (svartlut) och vitlut. Luten tillsätts för att lösa upp ligninet i träfibrerna. Lignin är som ett lim som håller ihop träfibrerna. Lutvätskan som lämnar kokeriet kallas för tunnlut och indunstningen torkar tunnluten i flera steg. När luten har torkats kallas den för brännlut (tjocklut) och förbränns i sodapannan. Smältan från sodapannan blandas med svaglut och bildar grönlut. I grönluten tillsätts bränd kalk och bildar kalkmjölk. Ur kalkmjölken separeras vitlut och mesa. Vitluten återinförs till kokeriet och kretsloppet fortsätter. Luten har stor betydelse för produktionen av pappersmassa på Södra Cell Värö. Om någon del i lutkretsloppet inte fungerar tvingas hela fabriken att stanna. Användning av lut är inte riskfritt. Lut är ett frätande ämne och det räcker med små kvantiteter för att orsaka stor skada. Därför är det viktigt att rätt skyddsutrustning används och respekt visas. Om Södra Cell Värö inte skulle använda lut skulle tillverkningsprocessen se annorlunda ut. Mekanisk process eller sulfitprocess skulle användas istället. Fördelarna med att använda lut är att kvalitén på pappersmassan blir bättre. Därför får pappersmassan ett större användningsområde. Nackdelarna med att använda lut är dels risken för olyckor, dels att vedutbytet endast är 50 %. Syftet med rapporten är att ge läsaren lärdom om hur lutens kretslopp fungerar och lutens betydelse på ett massabruk som Södra Cell Värö samt informera om vilka risker det finns vid arbete med lut.

  • 18.
    Johansson, Andreas
    University of Borås, School of Engineering.
    Siktning av avfall2008Other (Other academic)
  • 19.
    Johansson, Andreas
    University of Borås, School of Engineering.
    Waste refinery -joint initiatives towards improved energy recovery from waste2008In: Proceedings of World Bioenergy, conference & Exhibition on Biomass for Energy, oral sessions., 2008, p. 45-49Conference paper (Other academic)
  • 20.
    Johansson, Andreas
    et al.
    University of Borås, School of Engineering.
    Eskilsson, David
    Johansson, Linda
    Wikström-Blomqvist, Evalena
    Andersson, Bengt-Åke
    University of Borås, School of Engineering.
    Johnsson, Anders
    Combustion of Demanding Waste Fractions in a 10 MWe Waste-toEnergy Plant2007In: In Proceeding of ISWA/NVRD World Congress 2007, 2007Conference paper (Other academic)
  • 21.
    Johansson, Andreas
    et al.
    University of Borås, School of Engineering.
    Johnsson, Filip
    Niklasson, Fredrik
    Åmand, Lars-Erik
    Dynamics of furnace process in a CFB boiler2007In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 62, no 1-2, p. 550-560Article in journal (Refereed)
    Abstract [en]

    With the aim of understanding the dynamics of combustion, this work examines simultaneous fluctuations in fluid dynamic parameters and gas composition measured in a CFB furnace operated with coal as a fuel. The fluid dynamic parameters investigated are pressure and air flow entering the furnace. Gas composition was recorded by a zirconia-cell probe and a gas suction probe connected to a mass spectrometer having a high time resolution (10 Hz). The principal fluctuations detected are around I Hz and below 0.3 Hz. The fluctuations below 0.3 Hz mostly originate from variations in the fuel-feed rate. These variations create periods of reducing conditions caused by a momentarily high fuel input accompanied by a pressure rise in the furnace and a reduction of the air feed, which occurs concurrent with the release of an enhanced quantity of volatiles. Modelled pressure fluctuations based on the relation between volatile release and pressure in the furnace give similar pressure fluctuations as the measured pressure fluctuations, with respect to amplitude and characteristic time scale of the fluctuations. There is also a correlation between reducing conditions and the concentration of hydrocarbons. (c) 2006 Elsevier Ltd. All rights reserved.

  • 22.
    Johansson, Michael
    University of Borås, Faculty of Textiles, Engineering and Business.
    Hantering av IFC-exporter från Revit till IDA2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    It is extremely important to be able to export models directly from Revit to IDA for the energy simulations to be efficient. This report has a background description about how the IFC-format has been developed and how it is structured. However, the focus in the report is on how Revit can be implanted in the workflow, where both export and troubleshooting from Revit are described. IFC is the standard today to export data between various parts during the construction process and it is a format that is program independent, which means that it works across different applications. The current version of IFC is IFC4, but IFC2x3 is still the most used version since not every program has support for the new IFC4 format. It is extensive to figure out which data IDA requires for energy simulations, therefore this report contains both a tutorial for export settings and a file for automatic set correct export settings in Revit. To succeed with the energy simulations a requirement is that the space in the building is enclosed with walls, floor and roof, otherwise extreme thermal bridges will cause incorrect simulations. Therefore, there are several workarounds described in this report to correct these problems, including problems with windows, doors and problems with storage facilities . The description in this report is written with the assumption that the user do not have any experience with Revit. The guides were tested on a class of high school students that are studying the course CADCAD02. The result showed that when a problem occurs with a model it can easily be solved with the support from this report. Further differences between simulations in Revit and IDA were tested. The same model was simulated in eight different places and the standard deviation was calculated, this gave the coefficient range ±4 %, i.e. a simulation in IDA should not differ more than 4 % from the simulation in Revit. Similar results were found with the simulations of windows and doors, even though the difference was slightly lower.

  • 23.
    Manhica, Fabiao
    et al.
    University of Borås, School of Engineering.
    Lucas, Carlos
    Richards, Tobias
    University of Borås, School of Engineering.
    Wood Consumption and Analysis of the Bread Baking Process in Wood-Fired Bakery Ovens2012In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 5, no 47, p. 63-72Article in journal (Refereed)
    Abstract [en]

    Combustion of biomass in small-scale furnaces is used widely in different applications. The technology used is often “fixed grate” combustion in small batch furnaces. The efficiency of such a furnace is often low, which results in a high environmental impact. The aim of this work was to analyse the performance of the existing wood-fired bakery ovens that can be used to improve the efficiency. The data collected from 15 semi-direct and 3 indirect bakeries consisted of: the dimensions of the oven, the temperature profiles of the combustion chamber and the baking oven, the baking time and the bread quality. It was found that as much as 60 tons/day of green wood are consumed in the bread baking process in the area investigated. Two types of bakery ovens are used most commonly: indirect and semi-direct. The specific consumption was found to be 0.55 and 0.90 kg of wood per kg of wheat flour baked for the indirect and the semi-direct respectively. The analyses of the bread baked show that the variation of the temperature profile during the baking process influences the quality of the bread produced.

  • 24.
    Moradian, Farzad
    University of Borås, School of Engineering.
    Co-Combustion of Municipal Solid Waste and Animal Waste: Experiment and Simulation Studies2013Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Co-combustion of animal carcasses and slaughterhouse waste products (animal waste), which are classed as high-risk infectious waste, has been considered as a “fuel opportunity” for waste-to-energy boilers. In this study, the impact of co-combustion of animal waste with municipal solid waste (MSW) on operational issues such as bed agglomeration, deposit formation and emission was investigated, employing experimental and theoretical methods. In the experimental section, a series of full-scale tests in a bubbling fluidised-bed boiler were carried out, to determine the effects of animal waste co-combustion on the issues addressed. Two combustion scenarios were considered, identified as the reference (Ref) case and the animal waste (AW) case. In the Ref case, a solid-waste fuel mix, consisting of sorted and pretreated industry and household waste was combusted. In the AW case, 20 wt% AW was added to the reference fuel mix. The collected samples, which included super-heater deposits, fuel mixes and bed and fly ashes, were analysed, using chemical fractionation, SEM-EDX and XRD. In addition, the flue gases´ emission rate were continuously analysed, using FTIR spectrometry. The results showed positive effects from co-combustion of AW, indicating decreased deposit formation and lower risk of bed agglomeration, as well as reduced emissions of NOx and SO2. Moreover, it was found that the concentrations of P, Ca, S and Cl were enriched in the bed materials. In the theoretical section, thermodynamic calculations, with respect to experimental data, were performed to provide greater understanding of the ash transformation behaviour and the related melting temperature. The calculations mainly focused on bed agglomeration, where addition of AW to the MSW considerably reduced the risk of agglomeration. The results of equilibrium products and phase diagram information for the bed ashes suggested melt-induced agglomeration as a possible cause of the formation of sticky layers on the bed particle in the Ref case. Moreover, it was concluded that higher amounts of calcium phosphate and sulfates increased the first melting temperature of the bed ashes in the AW case.

  • 25.
    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.

  • 26.
    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.

  • 27.
    Oluoti, Kehinde
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Pettersson, Anita
    Richards, Tobias
    University of Borås, Faculty of Textiles, Engineering and Business.
    Investigating the morphology and reactivity of chars from Triplochiton scleroxylon pyrolysed under varied conditions2016In: Bioresource technology, E-ISSN 3736-3751, Vol. 208, p. 94-99Article in journal (Refereed)
    Abstract [en]

    The astronomical increase in global energy demand makes locating energy sources other than fossil fuels worthwhile. The use of tropical biomass wood waste as a renewable energy source was investigated in this study. The thermal conversion analysis of Albizia gummifera (ayinre) was carried out in a thermobalance reactor via steam gasification under varying temperature (700 to 1000 °C) and steam partial pressure (0.020 to 0.050 MPa). The experimental data was evaluated using three gas-solid reaction models. The modified volume reaction model (mVRM) gave the overall highest coefficient of determination (0.9993) and thereby the best conversion prediction. The observed char activation constant rates (from paired reaction conditions) indicated, on average, an increase in reactivity as the parameters increased. The results showed that the activation energy of the mVRM gave the lowest value (32.54 kJ/mpI) compared with those of the shrinking core model (SCM) and the volume reaction model (VRM) (49.29 and 49.89 kJ/mol, respectively).

  • 28.
    Oluoti, Kehinde
    et al.
    University of Borås, School of Engineering.
    Richards, Tobias
    University of Borås, School of Engineering.
    Doddapaneni, Tharaka
    Kanagasabapathi, DhipanKumar
    Evaluation of the Pyrolysis and Gasification Kinetics of Tropical Wood Biomass2014In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 9, no 2, p. 2179-2190Article in journal (Refereed)
    Abstract [en]

    Two tropical biomass species, teak (Tectona grandis) and obobo (Guarea thompsonii), were obtained in the form of sawmill waste from Nigeria and evaluated to determine their potential for gasification. Pyrolysis and gasification kinetics of the samples were investigated using a thermogravimetric analyser (TGA) at temperatures of 900 oC and 1,000 oC. Four iso-conversional methods, one peak temperature method, and two model-fitting methods were employed to determine the kinetic parameters, i.e. the apparent activation energy Ea, and pre-exponential factor A. Values of the gasification kinetic rate constant K were determined using two gas-solid reaction models: the volumetric reaction model (VRM) and the shrinking core model (SCM). The values obtained for all three kinetic parameters showed good agreement with values derived for samples of non-tropical wood.

  • 29.
    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.

  • 30.
    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?

  • 31.
    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.

  • 32.
    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.

  • 33.
    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.

  • 34.
    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.

  • 35.
    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)
  • 36.
    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)
  • 37.
    Rajendran, Karthik
    et al.
    University of Borås, School of Engineering.
    Kankanala, Harshavardhan R.
    Lundin, Magnus
    University of Borås, School of Engineering.
    Taherzadeh, Mohammad J.
    University of Borås, School of Engineering.
    Process simulation model for biogas production2013Conference paper (Other academic)
  • 38.
    Richards, Tobias
    University of Borås, Faculty of Textiles, Engineering and Business.
    Opportunities for thermal waste treatment2016In: Journal of Fundamentals of Renewable Energy and Applications, ISSN 2090-4533, E-ISSN 2090-4541, p. 70-72Article in journal (Refereed)
    Abstract [en]

    Thermal waste treatment faces many challenges of high ash related compounds from waste fuels.Vagaries in its composition that are very heterogeneous lead to problems faced during incinerationapart of course high energy consumption. However, new technologies and techniques have becomemore efficient addressing some of these problems too. Despite this, it is advisable to use this treatmentonly for waste streams which can not be effectively treated through other alternate techniques.

1 - 38 of 38
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