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  • 1. Abbasalizadeh, Aida
    et al.
    Malfliet, Annelies
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sietsma, Jilt
    Yang, Yongxiang
    Electrochemical Extraction of Rare Earth Metals in Molten Fluorides: Conversion of Rare Earth Oxides into Rare Earth Fluorides Using Fluoride Additives2017In: JOURNAL OF SUSTAINABLE METALLURGY, ISSN 2199-3823, Vol. 3, no 3, 627-637 p.Article in journal (Refereed)
    Abstract [en]

    In the present research on rare earth extraction from rare earth oxides (REOs), conversion of rare earth oxides into rare earth fluorides with fluoride fluxes is investigated in order to overcome the problem of low solubility of the rare earth oxides in molten fluoride salts as well as the formation of oxyfluorides in the fluorination process. Based on thermodynamic calculations, a series of experiments were performed for converting the rare earth oxides into rare earth fluorides using AlF3, ZnF2, FeF3, and Na3AlF6 as fluorinating agents in a LiF-Nd2O3 system. The formation of neodymium fluoride as a result of the reactions between these fluxes and neodymium oxide is confirmed. The rare earth fluoride thus formed can subsequently be processed through the electrolysis route in the same reactor, and rare earth metal can be produced as the cathodic deposit. In this concept, the REO dissolution in molten fluorides would become unnecessary due to the complete conversion of the oxide into the fluoride, REF3. The results of XRD and EPMA analysis of the reacted samples indicate that AlF3, ZnF2, and FeF3 can act as strong fluorinating agents for the neodymium oxide giving rise to a complete conversion of neodymium oxide into neodymium fluoride.

  • 2. Abbasalizadeh, Aida
    et al.
    Malfliet, Annelies
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sietsma, Jilt
    Yang, Yongxiang
    Electrochemical Recovery of Rare Earth Elements from Magnets: Conversion of Rare Earth Based Metals into Rare Earth Fluorides in Molten Salts2017In: Materials transactions, ISSN 1345-9678, E-ISSN 1347-5320, Vol. 58, no 3, 400-405 p.Article in journal (Refereed)
    Abstract [en]

    In the present work, selective extraction of rare earth (RE) metals from NdFeB magnets is investigated by studying the effects of various fluxes, viz. AlF3, ZnF2, FeF3 and Na3AlF6 in the LiF-NdFeB system. The aim is to convert RE from RE magnet into the fluoride salt melt. The results show the complete selective separation of neodymium (also dysprosium) from the magnet and formation of rare earth fluoride, leaving iron and boron unreacted. The formed rare earth fluoride can subsequently be processed in the same reactor through an electrolysis route so that RE can be deposited as a cathode product. The results of XRD and EPMA analysis of the reacted samples indicate that AlF3, ZnF2 and FeF3 can act as strong fluorinating agents for extraction of rare earth from NdFeB magnet, converting the RE to REF3. The results confirm the feasibility of the rare earth metals recovery from scrap NdFeB magnet as raw material. The fluoride conversion- electrolysis route suggested in the present work enables the extraction of rare earth metals in a single step using the above-mentioned fluxes.

  • 3. Abel, S
    et al.
    Bäbler, Matthäus
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Arpagaus, C
    Mazzotti, M
    Stadler, J
    Two-fraction and three-fraction continuous simulated moving bed separation of nucleosides2004In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1043, no 2, 201-210 p.Article in journal (Refereed)
    Abstract [en]

     A new experimental set-up and a new simulated moving bed (SMB) operation are presented in this work. A desktop SMB unit developed as a modification of the commercial AKTA(TM) explorer working platform has been utilized for the separation of different mixtures of nucleosides. Both two fraction and three fraction SMB separations have been carried out, the latter made possible by the adoption of a new SMB configuration and operating mode (three fraction SMB, 3F-SMB, operation). Experiments demonstrate the feasibility of the 3F-SMB operation, and confirm the trends predicted based on considerations about retention of the components to be separated along the unit. 

  • 4.
    Ahlawat, Paramvir
    KTH, School of Chemical Science and Engineering (CHE).
    Modellering och implementering av simultan dubbel gradient kromatografi2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Polypeptides are becoming an important component of the antibiotic therapeutics. The production demand of therapeutic polypeptides is increasing and there is a significant interest in developing more efficient production processes. In pharmaceutical industries, polypeptides are produced as a crude mixture. Reverse phase high performance liquid chromatography (RP HPLC) is used as a typical separation technique to purify the target polypeptide from other impurities. Currently organic modifier gradients are used to elute product peptides separately from impurities. In this work, we add a second, simultaneous counter-ion gradient, in the hope of increasing separation performance and call it double gradient reverse phase chromatography. A general procedure of the model-based optimization of a polypeptide crude mixture purification process was followed to evaluate the effects of the double gradients on industrial chromatographic process. The target polypeptide elution profile was modeled with a bi-Langmuir adsorption equilibrium isotherm. The isotherm parameters of the target polypeptide were estimated by the inverse method. The model parameters of the impurities were regressed from experimental data. The variations of the isotherm parameters with the modifier concentration and counter-ion concentration were taken into account of the adsorption model. After model calibration and validation by comparison with suitable experimental data, Pareto optimization of the process were carried out to analyze the differences between single gradient chromatography and double gradient chromatography. It was observed that the additional linear gradient of counter-ion concentration did not improve the separation process. Conclusively we were able to demonstrate the concept of double gradient reverse phase chromatography within limited time and possible least experimental efforts.

  • 5.
    Alevanau, Aliaksandr
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Study of pyrolysis and gasification of biomass from the self-organization perspective2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis focuses on the analysis of kinetics of i) low-temperature pyrolysis of gaseous hydrocarbons, ii) high-temperature steam gasification of char of wood pellets (>700oC), iii) high temperature pyrolysis of straw pellets in an atmosphere of argon and steam, and iv) high temperature pyrolysis of slices of transversally cut wooden sticks. The results of the kinetic measurements in the high-temperature cases are approximated using a least-square based optimization software, which was specially developed to analyse kinetics prone for deviation from the Arrhenius law.In the thesis a general analysis of the researched materials and kinetics of their pyrolysis and gasification is presented from the self-organization perspective. The energy transfer phenomena in both the pyrolysis and gasification processes of biomass are discussed with an emphasis on an analysis of basic phenomena involving the self-organized dynamics on fractal structures in the chosen biomass samples.

  • 6.
    Alvfors, Per
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Arnell, Jenny
    IVL.
    Berglin, Niklas
    Innventia.
    Björnsson, Lovisa
    LU.
    Börjesson, Pål
    LU.
    Grahn, Maria
    Chalmers/SP.
    Harvey, Simon
    Chalmers.
    Hoffstedt, Christian
    Innventia.
    Holmgren, Kristina
    IVL.
    Jelse, Kristian
    IVL.
    Klintbom, Patrik
    Kusar, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Lidén, Gunnar
    LU.
    Magnusson, Mimmi
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Pettersson, Karin
    Chalmers.
    Rydberg, Tomas
    IVL.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Stålbrand, Henrik
    LU.
    Wallberg, Ola
    LU.
    Wetterlund, Elisabeth
    LiU.
    Zacchi, Guido
    LU.
    Öhrman, Olof
    ETC Piteå.
    Research and development challenges for Swedish biofuel actors – three illustrative examples: Improvement potential discussed in the context of Well-to-Tank analyses2010Report (Other academic)
    Abstract [en]

    Currently biofuels have strong political support, both in the EU and Sweden. The EU has, for example, set a target for the use of renewable fuels in the transportation sector stating that all EU member states should use 10% renewable fuels for transport by 2020. Fulfilling this ambition will lead to an enormous market for biofuels during the coming decade. To avoid increasing production of biofuels based on agriculture crops that require considerable use of arable area, focus is now to move towards more advanced second generation (2G) biofuels that can be produced from biomass feedstocks associated with a more efficient land use. Climate benefits and greenhouse gas (GHG) balances are aspects often discussed in conjunction with sustainability and biofuels. The total GHG emissions associated with production and usage of biofuels depend on the entire fuel production chain, mainly the agriculture or forestry feedstock systems and the manufacturing process. To compare different biofuel production pathways it is essential to conduct an environmental assessment using the well-to-tank (WTT) analysis methodology. In Sweden the conditions for biomass production are favourable and we have promising second generation biofuels technologies that are currently in the demonstration phase. In this study we have chosen to focus on cellulose based ethanol, methane from gasification of solid wood as well as DME from gasification of black liquor, with the purpose of identifying research and development potentials that may result in improvements in the WTT emission values. The main objective of this study is thus to identify research and development challenges for Swedish biofuel actors based on literature studies as well as discussions with the the researchers themselves. We have also discussed improvement potentials for the agriculture and forestry part of the WTT chain. The aim of this study is to, in the context of WTT analyses, (i) increase knowledge about the complexity of biofuel production, (ii) identify and discuss improvement potentials, regarding energy efficiency and GHG emissions, for three biofuel production cases, as well as (iii) identify and discuss improvement potentials regarding biomass supply, including agriculture/forestry. The scope of the study is limited to discussing the technologies, system aspects and climate impacts associated with the production stage. Aspects such as the influence on biodiversity and other environmental and social parameters fall beyond the scope of this study. We find that improvement potentials for emissions reductions within the agriculture/forestry part of the WTT chain include changing the use of diesel to low-CO2-emitting fuels, changing to more fuel-efficient tractors, more efficient cultivation and manufacture of fertilizers (commercial nitrogen fertilizer can be produced in plants which have nitrous oxide gas cleaning) as well as improved fertilization strategies (more precise nitrogen application during the cropping season). Furthermore, the cultivation of annual feedstock crops could be avoided on land rich in carbon, such as peat soils and new agriculture systems could be introduced that lower the demand for ploughing and harrowing. Other options for improving the WTT emission values includes introducing new types of crops, such as wheat with higher content of starch or willow with a higher content of cellulose. From the case study on lignocellulosic ethanol we find that 2G ethanol, with co-production of biogas, electricity, heat and/or wood pellet, has a promising role to play in the development of sustainable biofuel production systems. Depending on available raw materials, heat sinks, demand for biogas as vehicle fuel and existing 1G ethanol plants suitable for integration, 2G ethanol production systems may be designed differently to optimize the economic conditions and maximize profitability. However, the complexity connected to the development of the most optimal production systems require improved knowledge and involvement of several actors from different competence areas, such as chemical and biochemical engineering, process design and integration and energy and environmental systems analysis, which may be a potential barrier.

  • 7.
    Andersson, Joakim
    KTH, School of Chemical Science and Engineering (CHE).
    Lifetime estimation of lithium-ion batteries for stationary energy storage system2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the continuing transition to renewable inherently intermittent energy sources like solar- and wind power, electrical energy storage will become progressively more important to manage energy production and demand. A key technology in this area is Li-ion batteries. To operate these batteries efficiently, there is a need for monitoring of the current battery state, including parameters such as state of charge and state of health, to ensure that adequate safety and performance is maintained. Furthermore, such monitoring is a step towards the possibility of the optimization of battery usage such as to maximize battery lifetime and/or return on investment. Unfortunately, possible online measurements during actual operation of a lithium-ion battery are typically limited to current, voltage and possibly temperature, meaning that direct measurement of battery status is not feasible. To overcome this, battery modeling and various regression methods may be used. Several of the most common regression algorithms suggested for estimation of battery state of charge and state of health are based on Kalman filtering. While these methods have shown great promise, there currently exist no thorough analysis of the impact of so-called filter tuning on the effectiveness of these algorithms in Li-ion battery monitoring applications, particularly for state of health estimation. In addition, the effects of only adjusting the cell capacity model parameter for aging effects, a relatively common approach in the literature, on overall state of health estimation accuracy is also in need of investigation.

    In this work, two different Kalman filtering methods intended for state of charge estimation: the extended Kalman filter and the extended adaptive Kalman filter, as well as three intended for state of health estimation: the dual extended Kalman filer, the enhanced state vector extended Kalman filer, and the single weight dual extended Kalman filer, are compared from accuracy, performance, filter tuning and practical usability standpoints. All algorithms were used with the same simple one resistor-capacitor equivalent circuit battery model. The Li-ion battery data used for battery model development and simulations of filtering algorithm performance was the “Randomized Battery Usage Data Set” obtained from the NASA Prognostics Center of Excellence. 

    It is found that both state of charge estimators perform similarly in terms of accuracy of state of charge estimation with regards to reference values, easily outperforming the common Coulomb counting approach in terms of precision, robustness and flexibility. The adaptive filter, while computationally more demanding, required less tuning of filter parameters relative to the extended Kalman filter to achieve comparable performance and might therefore be advantageous from a robustness and usability perspective. Amongst the state of health estimators, the enhanced state vector approach was found to be most robust to initialization and was also least taxing computationally. The single weight filter could be made to achieve comparable results with careful, if time consuming, filter tuning. The full dual extended Kalman filter has the advantage of estimating not only the cell capacity but also the internal resistance parameters. This comes at the price of slow performance and time consuming filter tuning, involving 17 parameters. It is however shown that long-term state of health estimation is superior using this approach, likely due to the online adjustment of internal resistance parameters. This allows the dual extended Kalman filter to accurately estimate the SoH over a full test representing more than a full conventional battery lifetime. The viability of only adjusting the capacity in online monitoring approaches therefore appears questionable. Overall the importance of filter tuning is found to be substantial, especially for cases of very uncertain starting battery states and characteristics.

  • 8.
    Arnau, Laurent
    KTH, School of Chemical Science and Engineering (CHE).
    Techno-Economic Feasibility Study for the Production of Microalgae Based Plant Biostimulant2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Microalgae are considered as a potential feedstock for many promising applications. Some active substances in microalgae have plant biostimulation effects potentially useful in agriculture. However, to produce such a microalgal biomass, specific microalgae cultivation and post-treatment processes must be designed to preserve active substances. A particular focus is provided on cultivation (tubular photobioreactor) and different plausible post-treatment scenarios for microalgae separation (flocculation and centrifugation) and preservation (sterilization and drying). For each step, yield and energy consumption are modeled using data taken from literature or lab and pilot scale experiments. Industrial equipment for scale-up process is also studied by comparing existing systems. These models enable to make an economic evaluation of the whole process and to study its profitability for each scenario. The breakeven price is calculated as a function of the production rate. Several parameters are suggested to improve system efficiency and profitability at the end of this study. However, a better microalgae characterization and more experiments on potential post-treatment systems are required to improve the accuracy of the model.

  • 9.
    Astorsdotter, Jennifer
    KTH, School of Chemical Science and Engineering (CHE).
    Dewatering Cellulose Nanofibril Suspensions through Centrifugation2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cellulose nanofibrils (CNF) is a renewable material with unique strength properties. A difficulty in CNF production is that CNF suspensions contain large amounts of water. If CNF suspension volume can be decreased by dewatering facilitated by centrifugation, then transportation costs and storage costs can be reduced. The aim of this thesis is to investigate the impact various parameters have on CNF centrifugation dewatering and identify optimal conditions for maximal water removal.

    A laboratory study was conducted using four materials; 2.0 w% enzymatically treated CNF (CNF1), 1.9 w% carboxymethylated CNF (CNF2) and two commercial samples (1.9 w% CNFA and 1.8 w% CNFB). The main method was analytical centrifugation up to 2330 g. Parameters tested were initial concentration before centrifugation, temperature, NaCl addition, pH, and applied solid compressive pressure (g-force and surface weight). In addition to centrifugation experiments the four materials were characterized with laser diffraction, UV-vis absorption, Dynamic light scattering, and dry weight measurements.

    Analysis of the experimental data collected show that increase in initial concentration give a higher final concentration, but less water is removed. Furthermore, temperature changes have no effect on separation of CNF and water. At an applied solid compressive pressure of 3 kPa and initial concentration at 1.5 w% the concentrations 5.5 w%, 1.5 w%, 4.0 w%, and 4.3 w% can be reach for CNF1, CNF2, CNFA, and CNFB respectively. After extrapolation of polynomial functions fitted to experimental data an applied solid compressive pressure of 22 kPa and initial concentration at 1:5 w%, the concentrations 9.1 w%, 1.5 w%, 6.9 w%, and 7.9 w% are predicted for CNF1, CNF2, CNFA, and CNFB respectively. The thickening of CNF suspensions achieved and predicted in this thesis implies possibilities for large amounts of water removal, e.g. the water content in a CNF1 suspension is reduced from 65.7 litres/kg CNF to 10.0 litres/kg CNF at the solid compressive pressure 22 kPa. The concentrations at 22 kPa are determined by extrapolation from experimental data <3 kPa solid compressive pressure. The carboxymethylated CNF2 can not be dewatered unless it is diluted or if salt or pH is adjusted. This is directly correlated to the electrostatic forces in the suspension and the Debye length. Addition of salt or lowered pH also eliminate any concentration gradients in diluted and centrifuged CNF2 suspensions.

  • 10.
    Baldassarre, Venezia
    KTH, School of Chemical Science and Engineering (CHE).
    Fischer-Tropsch Synthesis on ZrO2-promoted Co/Al2O3 Catalysts: Effect of Catalyst Support Preparation Methods2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Alumina is considered to be an effective catalyst support in the Fischer-Tropsch synthesis, owing to its favourable mechanical properties. However, if cobalt is deposited over alumina, the formation of active phase-support species decreases the catalyst reducibility and can be detrimental to the reaction performance. Recently, according to some reports, zirconia has attracted attention as a cobalt catalyst promoter for improving reducibility, activity and C5+ selectivity.

    This experimental work is aimed at studying the influence of zirconia promotion on cobalt-based catalysts. Two different support preparation methods were investigated: the pH-controlled precipitation of the zirconia promoter over a gamma alumina carrier from a one-phase and from a microemulsion solution. Two microemulsion systems were used: the water-in-oil and the oil-in-water techniques. The zirconia loading target over alumina was 20 wt% for all the promoted carriers. The cobalt active phase was deposited via the incipient wetness impregnation, reaching a concentration of 12 wt% over all the catalysts, including on a non-promoted one. Moreover, a further support was prepared using the oil-in-water microemulsion technique and impregnated with 15 wt% Co.

    X-ray diffraction, N2 adsorption and H2 chemisorption characterisations revealed comparable catalyst porosities and cobalt dispersions. Furthermore, TPR analyses showed that reducibility is not influenced by the addition of zirconia.

    The catalyst activation treatment was performed under pure hydrogen at 1 atm, 350 °C for 16 h. The syngas flow, passing through a fixed bed reactor, was first set to 250 NmL/min and then decreased until 30%, 40% and 50% CO conversion values were reached. The catalytic test results revealed an increase in activity and enhancement of C5+ selectivity for the catalyst prepared by pH-controlled precipitation of zirconia from the ordinary solution, relative to the non-promoted one. On the other hand, the “microemulsion” catalysts showed a significant decrease in turnover frequency compared to the Co/Al2O3 catalyst performance. Selectivity to C5+ and CH4 were respectively enhanced and reduced by promoting the catalyst with zirconia, for each conversion step. Olefin-to-paraffin content ratio in the fraction of C2, C3 and C4, along with the deactivation trend, were also analysed and discussed.

  • 11.
    Barrientos, Javier
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    González, N.
    Lualdi, Matteo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    The effect of catalyst pellet size on nickel carbonyl-induced particle sintering under low temperature CO methanation2016In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 514, 91-102 p.Article in journal (Refereed)
    Abstract [en]

    Abstract The present work aims to evaluate the effect of catalyst pellet size on deactivation due to nickel carbonyl-induced particle sintering. For that purpose, a γ-Al2O3-supported nickel catalyst was prepared and tested under low temperature and high CO partial pressure. A total of four different pellet sizes were employed in the present study. It was found that the deactivation rate decreases with increasing pellet size. A very severe deactivation was observed when using small pellets. Large pellets exhibited instead a more stable performance. This difference in catalyst stability was explained by X-ray diffraction analyses which revealed that the growth of the nickel particles was very severe when using small pellets. An evaluation of heat and mass transfer phenomena in these four pellets was also conducted. It was found that, under the present low temperature reaction conditions, the temperature at the catalyst external surface can greatly differ from that in the bulk gas when using sufficiently large pellets. It was also shown that, for large pellets, the major part of the interior of the catalyst is exposed to negligible CO partial pressures and high temperatures, fact that can reduce the potential for nickel carbonyl formation.

  • 12.
    Barrientos, Javier
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Montes, V.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Further insights into the effect of sulfur on the activity and selectivity of cobalt-based Fischer–Tropsch catalysts2016In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 275, 119-126 p.Article in journal (Refereed)
    Abstract [en]

     A sulfur poisoning study was performed by ex situ poisoning of a platinum-promoted cobalt/alumina catalyst with different sulfur amounts. The poisoned catalyst samples were tested at relevant Fischer–Tropsch reaction conditions and at the same CO conversion in order to evaluate the effect of sulfur on catalyst activity and product selectivity. It was found that the activity and the selectivity to long-chain hydrocarbons decrease with increasing sulfur content. Moreover, it was found that sulfur has no significant effect on the CO2 selectivity. It was also shown that sulfur significantly enhances olefin hydrogenation. Finally, a deactivation model relating the catalyst activity and the sulfur to cobalt active site ratio was proposed and used to describe the experimental results.

  • 13.
    Becker, Sebastian
    KTH, School of Chemical Science and Engineering (CHE).
    Inverkan av olika joner och jonconcentrationer på porstorleksfördelningen i trämassa-fibrer2011Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The basic ingredient of paper is the individual wood fibers. The property of the fibers depends on a variety of factors e.g., method of pulp production and processing. The final sheet quality depends in part on how the fibers interface between each other and therefore factors that affect the fiber size are of interest.

    The flexibility of the fibers depends in part on the pore water i.e., the fiber swelling. The sheet becomes less flexible at low water content which gives a loss in strength. Thus it becomes desirable to increase the water uptake.

    The experimental investigation described in this report consists of exposing the wood fibers to different ions and ionic strength and then measure the pore size by thermoporosimetry where a DSC (Differential Scanning Calorimeter) is used. DSC measures the freezing point of water in the pores of the wood fibers. As the freezing point varies with the pore size the size distribution can be determined.

    The results show that there are complications with thermoporosimetry measurements at different ion concentrations. The strength of the ionic solutions will contribute to a fictitious pore volume, which makes analysis difficult to interpret.

  • 14.
    Bertini, Lorenzo
    KTH, School of Chemical Science and Engineering (CHE).
    Modeling and Optimization of a Fuel Cell Hybrid System2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this project was the modeling, optimization and prediction of a hybrid system composed of a fuel cell, a dc-dc converter and a supercapacitor in series. Lab tests were performed for each device to understand their behavior, and then each one was modeled using software (Simulink). The validation of the model was done by comparing its results with measured data; finally the model was used for the optimization and the prediction of the hybrid system

  • 15.
    BHANDARI, SHASHANK
    KTH, School of Chemical Science and Engineering (CHE).
    Design of a solvent recovery system in a pharmaceutical manufacturing plant2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Solvents play a crucial role in the Active Pharmaceutical Ingredient (API) manufacturing and are used in large quantities. Most of the industries incinerate the waste solvents or send it to waste management companies for destruction to avoid waste handling and cross-contamination. It is not a cost effective method and also hazardous to the environment. This study has been performed at AstraZeneca’s API manufacturing plant at Sodertalje, Sweden. In order to find a solution, a solvent recovery system is modeled and simulated using ASPEN plus and ASPEN batch modeler. The waste streams were selected based on the quantity and cost of the solvents present in them. The solvent mixture in the first waste stream was toluene-methanol in which toluene was the key-solvent whereas in the second waste stream, isooctane-ethyl acetate was the solvent mixture in which isooctane was the key-solvent. The solvents in the waste stream were making an azeotrope and hence it was difficult to separate them using conventional distillation techniques. Liquid-Liquid Extraction with water as a solvent followed by batch distillation was used for the first waste stream and Pressure Swing Distillation was used for the second waste stream. The design was optimized based on cost analysis and was successful to deliver 96.1% toluene recovery with 99.5% purity and 83.6% isooctane recovery with 99% purity. The purity of the solvents was decided based on the quality conventions used at AstraZeneca so that it can be recovered and recycled in the same system. The results were favorable with a benefit of €335,000 per year and preventing nearly one ton per year carbon dioxide emissions to the environment. A theoretical study for the recovery system of toluene-methanol mixture was performed. The proposed design was an integration of pervaporation to the batch distillation. A blend of polyurethane / poly(dimethylsiloxane) (PU / PDMS) membrane was selected for the separation of methanol and toluene mixture. The results of preliminary calculations show 91.4% toluene recovery and 72% methanol recovery with desired purity.

  • 16.
    Bi, Ran
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Huang, Shan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. Linnaus University, Sweden.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Isolation of exceedingly low oxygen consuming fungal strains able to utilize lignin as carbon sourceIn: Cellulose Chemistry and Technology, ISSN 0576-9787Article in journal (Refereed)
  • 17.
    Bi, Ran
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Spadiut, Oliver
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Brumer, Harry
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Isolation and identification of microorganisms from soil able to live on lignin as acarbon source and to produce enzymes which cleave the β-o-4 bond in a lignin model compound2012In: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 46, no 3-4, 227-242 p.Article in journal (Refereed)
    Abstract [en]

    Several strains of fungi were isolated and identified from Scandinavian soil using agar plates with lignin as a carbon source. The strains grew significantly faster on this medium than on control plates without lignin. Different types of technical lignins were used, some of which contained trace amounts of sugars, even if the increased growth rate seemed not related to the sugar content. Some strains were cultivated in shaking flask cultures with lignin as a carbon source, with lignin apparently consumed by microbes - while accumulation of the microorganism biomass occurred. The cell-free filtrates of these cultures could reduce the apparent molecular weights of lignosulphonates, while the culture filtrate of one strain could cleave the beta-O-4 bond in a lignin model compound.

  • 18.
    BIN HANNAN, KHALID
    KTH, School of Chemical Science and Engineering (CHE).
    Organiska kväveföreningars påverkan på vätebehandlingsanläggningens prestanda2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Various distillates are treated with hydrogen gas during hydrotreatment in the presence of catalyst in order to reduce the sulfur and aromatic content of the product. Optimal hydrotreater performance is essential for producing Nynas specialty oils, in order to fulfill the planned production volume and to meet the product specification. Loss of catalyst activity is inevitable during the production. To adjust for the impact of catalyst deactivation, different process variables are manipulated. Different distillates affect the catalyst in different ways due to the variation in distillate composition. Distillates with higher organic nitrogen content and running at a lower temperature tend to deactivate the catalyst more due to the adsorption of nitrogen compounds on the active sites of the catalyst and their slow nature of desorption.

    In this master thesis, different catalyst deactivation mechanisms with a focus on nitrogen deactivation have been studied. Since nitrogen is not normally measured at Nynas, nitrogen content of different distillates and products and how these values change during operation was not known. Different distillates, blend of distillates and different products were measured to estimate roughly the typical nitrogen value of the distillates and products. The temperature data inside the reactors were analyzed to calculate and plot WABT (weighted average bed temperature) during different product runs and to see whether there is a correlation between the nitrogen content of the feed and operation severity (increase in WABT). Historical process data from hydrotreater unit 2 (mostly from 2013-2014) were analyzed with a view to finding out signs of catalyst deactivation. Similar product runs were also analyzed and compared to see how the catalysts performed at different periods of time. A kinetic model, based on HDS kinetics, has been used for following up two product runs. To do so, sulfur content of the feed and product were measured. Aromatic content of the product was also measured to see whether the product was on specification.

    .From the calculation and plotting of WABTs, it could be seen that there is an increase in WABT during the product runs operating at lower temperatures and with higher nitrogen content. From the comparison of two P3 product runs at two different time periods, it could be seen that ∆T development over one bed (amount of reaction over the bed) was much lower at one time. This can possibly be a sign of catalyst deactivation since it contributed to lesser amount of reaction over the bed.

    From the calculations by using the kinetic model, it could be seen that the actual temperatures were higher than the predicted temperatures. The increase in WABTs could also be noticed. These observations can possibly be coupled with nitrogen deactivation of the catalysts.  However, more tests are required to verify whether the temperature differences were significant or not. Other parameters which are also important from product selling point of view such as viscosity, color, flash point, acid number etc. and have not been covered in this degree project need to be taken into consideration before making further conclusions.

  • 19.
    Biswas, Amit Kumar
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Thermochemical behavior of pretreated biomass2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mankind has to provide a sustainable alternative to its energy related problems. Bioenergy is considered as one of the potential renewable energy resources and as a result bioenergy market is also expected to grow dramatically in future. However, logistic issues are of serious concern while considering biomass as an alternative to fossil fuel. It can be improved by introducing pretreated wood pellet.

    The main objective of this thesis is to address thermochemical behaviour of steam exploded pretreated biomass. Additionally, process aspects of torrefaction were also considered in this thesis. Steam explosion (SE) was performed in a laboratory scale reactor using Salix wood chips. Afterwards, fuel and thermochemical aspects of SE residue were investigated. It was found that Steam explosion pretreatment improved both fuel and pellet quality. Pyrolysis of SE residue reveals that alerted biomass composition significantly affects its pyrolysis behaviour. Contribution from depolymerized components (hemicellulose, cellulose and lignin) of biomass was observed explicitly during pyrolysis. When devolatilization experiment was performed on pellet produced from SE residue, effect of those altered components was observed. In summary, pretreated biomass fuel characteristics is significantly different in comparison with untreated biomass. On the other hand, Process efficiency of torrefaction was found to be governed by the choice of appropriate operating conditions and the type of biomass.

  • 20.
    Biswas, Amit Kumar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Yang, Weihong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Devolatilization characteristics of steam explosion pretreated wood pelletIn: Fuel processing technology, ISSN 0378-3820Article in journal (Other academic)
  • 21.
    Biswas, Amit Kumar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Yang, Weihong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Steam pretreatment of Salix to upgrade biomass fuel for wood pellet production2011In: Fuel processing technology, ISSN 0378-3820, Vol. 92, no 9, 1711-1717 p.Article in journal (Refereed)
    Abstract [en]

    Steam explosion (SE) pretreatment is served to separate the main components of woody biomass. In general there is a noticeable gap in literature in terms of application of steam explosion process to upgrade biomass fuel for wood pellet production. In order to study the influence of steam explosion pretreatment on biomass fuel, Salix wood chips was used as raw material. Four different SE experiments were performed by varying two key process factors; time and temperature. Elementary quality and ash properties of the pretreated residue were investigated. Moreover, physical and thermochemical properties of the pellet, produced from the residue, were also investigated. Reduction in ash content especially in alkali metals was observed in steam treated residue. Pretreatment of biomass also enhanced carbon content and reduced oxygen amount in the fuel which enhanced the heating value of the fuel. Moreover, pretreatment enhanced pellet density, impact resistance, and abrasive resistance of pellet. However, small degradation in ash fusion characteristics and char reactivity was also observed as the severity of the process increased.

  • 22.
    Brandin, Jan
    et al.
    Linnaeus University.
    Hulteberg, Christian
    LTH, Lund University.
    Kusar, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    A review of thermo-chemical conversion of biomass into biofuels-focusing on gas cleaning and up-grading process steps2017Report (Other academic)
    Abstract [en]

    It is not easy to replace fossil-based fuels in the transport sector, however, an appealing solution is to use biomass and waste for the production of renewable alternatives. Thermochemical conversion of biomass for production of synthetic transport fuels by the use of gasification is a promising way to meet these goals.

    One of the key challenges in using gasification systems with biomass and waste as feedstock is the upgrading of the raw gas produced in the gasifier. These materials replacing oil and coal contain large amounts of demanding impurities, such as alkali, inorganic compounds, sulphur and chlorine compounds. Therefore, as for all multi-step processes, the heat management and hence the total efficiency depend on the different clean-up units. Unfortunately, the available conventional gas filtering units for removing particulates and impurities, and also subsequent catalytic conversion steps have lower optimum working temperatures than the operating temperature in the gasification units.

    This report focuses on on-going research and development to find new technology solutions and on the key critical technology challenges concerning the purification and upgrading of the raw gas to synthesis gas and the subsequent different fuel synthesis processes, such as hot gas filtration, clever heating solutions and a higher degree of process integration as well as catalysts more resistant towards deactivation. This means that the temperature should be as high as possible for any particular upgrading unit in the refining system. Nevertheless, the temperature and pressure of the cleaned synthesis gas must meet the requirements of the downstream application, i.e. Fischer-Tropsch diesel or methanol.

    Before using the gas produced in the gasifier a number of impurities needs to be removed. These include particles, tars, sulphur and ammonia. Particles are formed in gasification, irrespective of the type of gasifier design used. A first, coarse separation is performed in one or several cyclone filters at high temperature. Thereafter bag-house filters (e.g. ceramic or textile) maybe used to separate the finer particles. A problem is, however, tar condensation in the filters and there is much work performed on trying to achieve filtration at as high a temperature as possible.

    The far most stressed technical barriers regarding cleaning of the gases are tars. To remove the tar from the product gas there is a number of alternatives, but most important is that the gasifier is operated at optimal conditions for minimising initial tar formation. In fluid bed and entrained flow gasification a first step may be catalytic tar cracking after particle removal. In fluid bed gasification a catalyst, active in tar cracking, may be added to the fluidising bed to further remove any tar formed in the bed. In this kind of tar removal, natural minerals such as dolomite and olivine, are normally used, or catalysts normally used in hydrocarbon reforming or cracking. The tar can be reformed to CO and hydrogen by thermal reforming as well, when the temperature is increased to 1300ºC and the tar decomposes. Another method for removing tar from the gas is to scrub it by using hot oil (200-300ºC). The tar dissolves in the hot oil, which can be partly regenerated and the remaining tar-containing part is either burned or sent back to the gasifier for regasification.

    Other important aspects are that the sulphur content of the gas depends on the type of biomass used, the gasification agent used etc., but a level at or above 100 ppm is not unusual. Sulphur levels this high are not acceptable if there are catalytic processes down-stream, or if the emissions of e.g. SO2 are to be kept down. The sulphur may be separated by adsorbing it in ZnO, an irreversible process, or a commercially available reversible adsorbent can be used. There is also the possibility of scrubbing the gas with an amine solution. If a reversible alternative is chosen, elementary sulphur may be produced using the Claus process.

    Furthermore, the levels of ammonia formed in gasification (3,000 ppm is not uncommon) are normally not considered a problem. When combusting the gas, nitrogen or in the worst case NOx (so-called fuel NOx) is formed; there are, however, indications that there could be problems. Especially when the gasification is followed by down-stream catalytic processes, steam reforming in particular, where the catalyst might suffer from deactivation by long-term exposure to ammonia.

    The composition of the product gas depends very much on the gasification technology, the gasifying agent and the biomass feedstock. Of particular significance is the choice of gasifying agent, i.e. air, oxygen, water, since it has a huge impact on the composition and quality of the gas, The gasifying agent also affects the choice of cleaning and upgrading processes to syngas and its suitability for different end-use applications as fuels or green chemicals.

    The ideal upgraded syngas consists of H2 and CO at a correct ratio with very low water and CO2 content allowed. This means that the tars, particulates, alkali salts and inorganic compounds mentioned earlier have to be removed for most of the applications. By using oxygen as the gasifying agent, instead of air, the content of nitrogen may be minimised without expensive nitrogen separation.

    In summary, there are a number of uses with respect to produced synthesis gas. The major applications will be discussed, starting with the production of hydrogen and then followed by the synthesis of synthetic natural gas, methanol, dimethyl ether, Fischer-Tropsch diesel and higher alcohol synthesis, and describing alternatives combining these methods. The SNG and methanol synthesis are equilibrium constrained, while the synthesis of DME (one-step route), FT diesel and alcohols are not. All of the reactions are exothermal (with the exception of steam reforming of methane and tars) and therefore handling the temperature increase in the reactors is essential. In addition, the synthesis of methanol has to be performed at high pressure (50-100 bar) to be industrially viable.

    There will be a compromise between the capital cost of the whole cleaning unit and the system efficiency, since solid waste, e.g. ash, sorbents, bed material and waste water all involve handling costs. Consequently, installing very effective catalysts, results in unnecessary costs because of expensive gas cleaning; however the synthesis units further down-stream, especially for Fischer-Tropsch diesel, and DME/methanol will profit from an effective gas cleaning which extends the catalysts life-time. The catalyst materials in the upgrading processes essentially need to be more stable and resistant to different kinds of deactivation.

    Finally, process intensification is an important development throughout chemical industries, which includes simultaneous integration of both synthesis steps and separation, other examples are advanced heat exchangers with heat integration in order to increase the heat transfer rates. Another example is to combine exothermic and endothermic reactions to support reforming reactions by using the intrinsic energy content. For cost-effective solutions and efficient application, new solutions for cleaning and up-grading of the gases are necessary.

  • 23.
    Bryngelsson, Mårten
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Hansson, Anders
    Energy policy on shaky ground?: A study of CCS-scenarios2009In: Energy Procedia, ISSN 1876-6102, no 1, 4673-4680 p.Article in journal (Refereed)
    Abstract [en]

    Scenarios play an important role for the societal acceptance of CCS. This paper looks into influential reports containing CCS scenarios and analyses results, key assumptions and drivers for CCS' deployment. Significant uncertainties regarding CCS' development were in several cases excluded or marginalized. Despite these shortcomings, scenarios support a massive deployment of CCS and reflect an undivided optimism. If CCS would fail to meet the high expectations a backlash could follow. Indications were found that new scenarios including uncertainties are needed to balance this over-optimism. So-called unpleasant scenarios are often valuable in helping decision makers develop flexible strategies and policies.

  • 24.
    Bryngelsson, Mårten
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Lindfeldt, Erik G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Heller, Jan
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    The modelling of a hybrid combined cycle with pressurised fluidised bed combustion and CO2 capture2009In: International journal of greenhouse gas control, ISSN 1750-5836, Vol. 3, no 3, 255-262 p.Article in journal (Refereed)
    Abstract [en]

    This study investigates the possibility of capturing CO2 from flue gas under pressurised conditions, which could prove to be beneficial in comparison to working under atmospheric conditions. Simulations of two hybrid combined cycles with pressurised fluidised bed combustion and CO2 capture are presented. CO2 is captured from pressurised flue gas by means of chemical absorption after the boiler but before expansion. The results show a CO2 capture penalty of approximately 8 percentage points (including 90% CO2 capture rate and compression to 110 bar), which makes the efficiency for the best performing cycle 43.9%. It is 5.2 percentage points higher than the most probable alternative, i.e. using a natural gas fired combined cycle and a pulverised coal fired condensing plant separately with the same fuel split ratio. The largest part of the penalty is associated with the lower mass flow of flue gas after CO2 capture, which leads to a decrease in work output in the expander and potential for feed water heating. The penalty caused by the regeneration of absorbent is quite low, since the high pressure permits the use of potassium carbonate, which requires less regeneration heat than for example the more commonly proposed monoethanolamine. Although the efficiencies of the cycles look promising it will be important to perform a cost estimate to be able to make a fair comparison with other systems. Such a cost estimate has not been done in this study. A significant drawback of these hybrid cycles in that respect is the complex nature of the systems that will have a negative effect on the economy.

  • 25.
    Bryngelsson, Mårten
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Westermark, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    CO2 capture pilot test at a pressurized coal fired CHP plant2009In: Energy Procedia, ISSN 1876-6102, Vol. 1, no 1, 1403-1410 p.Article in journal (Refereed)
    Abstract [en]

    CO2 capture from pressurized flue gas using a variation of the hot potassium carbonate process has been demonstrated at a pilot plant with authentic flue gas from the Vartan combined heat and power plant in Stockholm. The plant has served as a proof of concept installation, and has confirmed that: i) the pre-treatment of the flue gas is adequate for protecting the absorbent from degradation, ii) the CO2 capture efficiency is high (> 98 %), iii) no harmful components are fed to the gas turbine, and iv) absorbent degradation is low (0.85 mole percent/month).

  • 26.
    Bryngelsson, Mårten
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Westermark, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Feasibility study of CO2 removal from pressurized flue gas in a fully fired combined cycle: the Sargas project2005In: Proceedings of the 18th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS, 2005, 703-710 p.Conference paper (Refereed)
    Abstract [en]

    In this article a novel concept for CO2 removal from power plants is discussed from a systems perspective. The main advantage of the process is that the investment cost and the power penalty for CO2 removal can be substantially reduced compared to conventional combined cycles. The proposed technical solution comprises fully fired combined cycle, which minimizes the amount of flue gas. Furthermore, the CO2 absorption is performed at pressurized conditions prior to the expansion, which further enhances the CO2 removal. The modification of the power cycle and integration of absorption stages makes CO2 removal equipment much more compact and allows the use Of CO2 absorbents with lower heat demand for the regeneration. The partial pressure of CO2 is above atmospheric pressure and removal efficiencies above 95% can be obtained with potassium carbonate absorption (the Benfield process). The treated flue gas is then reheated and re-humidified before the expansion in the gas turbine.

    A Norwegian consortium has developed the concept and feasibility studies have been performed for 100 MW and 400 MW power plants based on natural gas in Norway. The produced carbon dioxide is intended for storage in the Norwegian oil and gas fields in order to enhance the oil recovery. The suggested localizations of the power plants have been chosen accordingly. The design study is based on the same gas turbine and steam cycle as used in the commercial Pressurized Fluidized Bed Combustion (PFBC) cycle. PFBC plants are presently fired with coal but the fluid bed combustor for coal will be replaced by a gas combustor if natural gas is used. A key advantage is that the process can be built solely from commercially available components.

    This report is an assessment of the features, capabilities, advantages and future possibilities of the suggested power cycle with integrated CO2 removal. A power plant for 100 MW power output and based on natural gas is considered suitable as a first demonstration plant to be built in Hammerfest, Norway. A permit application has been turned in. For such a demonstration plant the process simulations have indicated that an efficiency of about 40% can be obtained, including the penalties from CO2 capture and compression. Further improvements, e.g. supercritical steam cycle or more advanced gas turbine increases the efficiency and for a 400 MW power cycle a net efficiency of about 44-48% has been simulated (including CO2 capture and compression). The cycle may also be suitable for CO2 removal from coal-fired plants.

  • 27.
    Brännvall, Elisabet
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Jansson, Zheng
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Characterisation of dissolved spruce xylan in kraft cooking2011In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 26, no 4, 380-385 p.Article in journal (Refereed)
    Abstract [en]

    Xylan dissolved during kraft cooking and later redeposited on fibre surfaces has been demonstrated to affect paper strength properties. Earlier studies have demonstrated that it is the xylan characteristics, rather than simply the amount of xylan, that influence the strength-enhancing effect of xylan. To use xylan optimally, it is useful to understand xylan’s beneficial characteristics and how cooking conditions affect them.

    In this study, spruce chips were kraft cooked under various cooking conditions and the xylan in the black liquor was characterized. We found that dissolved spruce xylan had a much higher amount of bound lignin than found in previous studies of xylan dissolved from hardwoods. The ionic strength of the cooking liquor affected the amount of dissolved xylan as well as the uronic acid content of the xylan.

  • 28.
    Bäbler, Matthäus
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    A collision efficiency model for flow-induced coagulation of fractal aggregates2008In: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 54, no 7, 1748-1760 p.Article in journal (Refereed)
    Abstract [en]

    A model for flow-induced collisions of fractal aggregates is developed. The model is based on the analysis of the relative trajectories between a pair of aggregates that takes into account their hydrodynamic and their colloidal interactions. Regarding the former, the aggregates are modeled as permeable spheres where the Brinkman equation is used to describe the flow inside the aggregates. Interparticle forces are incorporated by considering the forces between the primary particles in the two aggregates that are the nearest. The model results in a collision efficiency that depends on the masses of the colliding aggregates, the fractal dimension, and a nondimensional Hamaker constant characterizing the interparticle forces. The collision efficiency model is used to investigate the dynamics of a suspension undergoing coagulation. Significant deviations with respect to existing collision efficiency models are evidenced. 

  • 29.
    Bäbler, Matthäus
    ETH Zurich.
    Modelling of aggregation and breakage of colloidal aggregates in turbulent flows: Diss., Eidgenössische Technische Hochschule ETH Zürich, Nr. 17139, 20072007Doctoral thesis, monograph (Other academic)
  • 30.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Mazzotti, Marco
    Soos, Miroslav
    Morbidelli, Massimo
    Breakup and aggregation in turbulently stirred vessels2009In: 13th European Conference on Mixing, 2009Conference paper (Refereed)
    Abstract [en]

    The breakup and aggregation of small solid particle aggregates in hetero-geneous °ows is modeled through a multizonal population balance model. Breakupand aggregation are described through comprehensive rate expressions that takeinto account the local properties of the turbulent °ow. Two approaches are pursuedto de¯ne the zones: in the ¯rst approach the zones are prede¯ned and computational°uid dynamics is used to compute the zone properties. In the second approach thezone properties are directly ¯tted to experimental data. Model results compare wellwith experiments for the aggregation of a polystyrene latex in a stirred tank evenwhen only two zones are used.

  • 31.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Morbidelli, M.
    Analysis of the aggregation-fragmentation population balance equation with application to coagulation2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 316, no 2, 428-441 p.Article in journal (Refereed)
    Abstract [en]

    Coagulation of small particles in agitated suspensions is governed by aggregation and breakage. These two processes control the time evolution of the cluster mass distribution (CMD) which is described through a population balance equation (PBE). In this work, a PBE model that includes an aggregation rate function, which is a superposition of Brownian and flow induced aggregation, and a power law breakage rate function is investigated. Both rate functions are formulated assuming the clusters are fractals. Further, two modes of breakage are considered: in the fragmentation mode a particles splits into w ≥ 2 fragments of equal size, and in the erosion mode a particle splits into two fragments of different size. The scaling theory of the aggregation-breakage PBE is revised which leads to the result that under the negligence of Brownian aggregation the steady state CMD is self-similar with respect to a non-dimensional breakage coefficient θ. The self-similarity is confirmed by solving the PBE numerically. The self-similar CMD is found to deviate significantly from a log-normal distribution, and in the case of erosion it exhibits traces of multimodality. The model is compared to experimental data for the coagulationof a polystyrene latex. It is revealed that the model is not flexible enough to describecoagulation over an extended range of operation conditions with a unique set of parameters. In particular, it cannot predict the correct behavior for both a variation in the solid volume fraction of the suspension and in the agitation rate (shear rate).

  • 32.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Morbidelli, M.
    Baldyga, Jerzy
    Modelling the breakup of solid aggregates in turbulent flows2008In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 612, 261-289 p.Article in journal (Refereed)
    Abstract [en]

    The breakup of solid aggregates suspended in a turbulent flow is considered. The aggregates are assumed to be small with respect to the Kolmogorov length scale and the flow is assumed to be homogeneous. Further, it is assumed that breakup is caused by hydrodynamic stresses acting on the aggregates, and breakup is therefore assumed to follow a first-order kinetic where K-B(x) is the breakup rate function and x is the aggregate mass. To model K-B(x), it is assumed that an aggregate breaks instantaneously when the surrounding flow is violent enough to create a hydrodynamic stress that exceeds a critical value required to break the aggregate. For aggregates smaller than the Kolmogorov length scale the hydrodynamic stress is determined by the viscosity and local energy dissipation rate whose fluctuations are highly intermittent. Hence, the first-order breakup kinetics are governed by the frequency with which the local energy dissipation rate exceeds a critical value (that corresponds to the critical stress). A multifractal model is adopted to describe the statistical properties of the local energy dissipation rate, and a power-law relation is used to relate the critical energy dissipation rate above which breakup occurs to the aggregate mass. The model leads to an expression for K-B(x) that is zero below a limiting aggregate mass, and diverges for x -> infinity. When simulating the breakup process, the former leads to an asymptotic mean aggregate size whose scaling with the mean energy dissipation rate differs by one third from the scaling expected in a non-fluctuating flow.

  • 33.
    Bäbler, Matthäus
    et al.
    Swiss Fed Inst Technol, Inst Proc Engn.
    Moussa, Amgad S.
    Soos, Miroslav
    Morbidelli, Massimo
    Structure and Kinetics of Shear Aggregation in Turbulent Flows: I. Early Stage of Aggregation2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 16, 13142-13152 p.Article in journal (Refereed)
    Abstract [en]

    Aggregation of rigid colloidal particles leads to fractal-like structures that are characterized by a fractal dimension d(f) which is a key parameter for describing aggregation processes. This is particularly true in shear aggregation where d(f) strongly influences aggregation kinetics. Direct measurement of d(f) in the early stages of shear aggregation is however difficult, as the aggregates are small and few in number. An alternative method for determining d(f) is to use an aggregation model that when fitted to the time evolution of the cluster mass distribution allows for estimating d(f). Here, we explore three such models, two of which are based on an effective collision sphere and one which directly incorporates the permeable structure of the aggregates, and we apply them for interpreting the initial aggregate growth measured experimentally in a turbulent stirred tank reactor. For the latter, three polystyrene latexes were used that differed only in the size of the primary particles (d(p) = 420, 600, and 810 nm). It was found that all three models describe initial aggregation kinetics reasonably well using, however, substantially different values for 4 To discriminate among the models, we therefore also studied the regrowth of preformed aggregates where d(f) was experimentally accessible. It was found that only the model that directly incorporates the permeable structure of the aggregates is able to predict correctly this second type of experiments. Applying this model to the initial aggregation kinetics, we conclude that the actual initial fractal dimension is d(f) = 2.07 +/- 0.04 as found from this model.

  • 34.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Sefcik, J
    Morbidelli, M
    Baldyga, J
    Hydrodynamic interactions and orthokinetic collisions of porous aggregates in the Stokes regime2006In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 18, no 1, 013302- p.Article in journal (Refereed)
    Abstract [en]

    The hydrodynamic interaction of two neutrally buoyant porous aggregates is investigated under creeping flow conditions for the case where the undisturbed velocity of the surrounding flow field is a linear function of position. In this framework, the relative velocity between two aggregates is given by the deformation of the undisturbed flow expressed through the rate of strain and the angular velocity of the flow field, and by two flow-independent hydrodynamic functions, typically referred to as A and B, which account for the disturbance of the flow field due to the presence of the particles [G. K. Batchelor and J. T. Green, J. Fluid Mech. 56, 375 (1972)]. In the present paper, the analysis of thehydrodynamic interaction that is known for the case of two impermeable, solid particles is extended to the case of porous aggregates by applying Brinkman's equation to describe the flow within the aggregates. A reflection scheme is applied to calculate A and B and the obtained expressions are applied to interpret the orthokinetic aggregation ofaggregates in diluted suspensions, where the collision frequency is computed using the method of relative trajectories of a pair of aggregates.

  • 35.
    Cameli, Fabio
    KTH, School of Chemical Science and Engineering (CHE).
    Microbial Fuel Cell for Waste Water Treatment2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Microbial Fuel Cell is a novel technology that can be used for a waste water treatment in order to simultaneously remove carbonaceous matter and nitrogen while producing electrical power.

    Even if it is not an established technology so far, MFC could be a cost effective option for waste water treatment and the major challenge of this process will be the device scale-up. Exoelectrogenic bacteria are capable of converting the chemical energy of organic matter into electrical energy by transferring the electrons produced in the oxidation to the anode electrode.

    This project focused on developing a single device for nitrification, denitrification and carbon removal. Two double air-cathode single chamber MFCs are used to test the feasibility of this process that could replace the biological unit in a waste water treatment train.

    The cells tested in this study were manufactured with the purpose of achieving a high surface area on both the anode electrode (vitreous carbon foam) and the air-cathode electrodes (metallic mesh with diffusion layer and active layer) with different catalysts for the reduction reaction (cobalt and platinum). The bacterial biofilm growth is a fundamental step and the cells Open Circuit Potential was monitored during all the start-up period to determine the microorganism acclimation: a three days lag period was observed in both cells before the potential rise. The second cell was forced to reach higher voltage through an anode polarization and that seems to positively affect the biofilm stability at lower voltages transferring a greater amount of electrons and hence obtaining a higher current and power generation. For this reason after three weeks of inoculation the second cell reached an open circuit potential of 0.76 V which is a promising value for such a system.

    Electrochemical and biological tests were conduced in order to test the power production of the cell and the substrate removal from the waste water. Polarization curves were used to evaluate power generation (and the maximum production under a specific external load) and the cell voltage trend which is characterized by activation and ohmic losses: 32 mW/ and 41 mW/  are the power density normalized by cathode surface (72 ) reached by respectively first and second cell. The experimental conditions were varied from low to high temperature and from low to high inlet flow rate but the most affecting phenomenon seems to be the biofilm formation since significant voltage drops were noticed after long closed circuit operation. Higher cell voltage characterized the second cell thanks to more active cathode (platinum catalyst used) and more negative bacterial biofilm but a bigger drop in current generation over time affects the system performance and the most reliable reason is the shorter acclimation time compared to the first cell.

    Cyclic voltammetry tests were carried out on both electrodes to study the potential range of activity and determine an optimal operational voltage despite of mass transport or kinetic limitations.

    Substrate removal tests at different retention times in power generation conditions (external load 100 Ω) showed a relatively high total nitrogen consumption (maximum 72.2 %) for the first cell while lower values were achieved by the second system meaning that a longer acclimation period is beneficial for nitrifying and denitrifying bacteria to thrive on the cathode biofilm.

    Effluent pH level are almost similar to the initial values probably because of nitrification and denitrification protons offset.

  • 36.
    Carlsson, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Stenman, David
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Merényi, Gabor
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Reitberger, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    A comparative study on the degradation of cotton linters induced by carbonate and hydroxyl radicals generated from peroxynitrite2005In: Holzforschung, ISSN 0018-3830, Vol. 59, no 2, 132-142 p.Article in journal (Refereed)
    Abstract [en]

    Carbonate (CO3.(-)) and hydroxyl (HO.) radicals were chemically produced in cotton linter suspensions using peroxynitrite as a radical precursor. Both radicals could degrade cotton linters, as shown by viscosity and GPC-SEC measurements. As evidenced by the viscosity measurements, the presence of oxygen during the cotton linter treatments slightly increased cellulose degradation by both radicals. For the carbonate radical, more than 90% of the viscosity losses could be recovered by reductive NaBH4 treatment before measuring the viscosity, whereas only approximately 40% of the viscosity was recovered after hydroxyl radical degradation and subsequent NaBH4 treatment. This indicates that carbonate radicals mainly abstract H-atoms adjacent to hydroxyl groups, i.e., at C-2, C-3 and C-6. This intramolecular selectivity may reflect a polar effect, whereby hydrogen atom abstractions from these positions are favoured. In addition, abstraction at C-6 would be sterically and statistically favoured.

  • 37.
    Cazot, Mathilde
    KTH, School of Chemical Science and Engineering (CHE).
    Empirical Modeling of a full-iron redox flow battery2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The need for energy storage is growing to reduce the carbon footprint of electricity

    production. Among the conceivable storage solutions, the redox flow battery (RFB) is

    one of the most promising. The best-researched type is the vanadium flow battery, but

    extensive research is underway to develop a cheaper and more compact system. The full-

    iron redox flow battery is an attractive alternative. A testing module has been developed,

    in order to study the influence of different operating parameters on the system output.

    The experiments highlight that the electrode compression, the stacking of single cells and

    the charge and discharge rates are design key factors and need a precise optimization. A

    35% electrode compression is a good trade-off between pump power losses and low contact

    resistances inside the cell. Single cells undergo a higher self-discharge when they are piled

    up; it is the direct effect of a power leakage called shunt current. The stack design must

    be thought with caution to lessen this power loss. The cycling profile also influence the

    battery performance. The findings confirm that optimizing the charge and discharge rates

    can prolong the system lifespan.

  • 38.
    Chavez Varela, Camila
    KTH, School of Chemical Science and Engineering (CHE).
    Elektrokemisk sensor för styrning av bränslecell2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Telecommunication stations for surveillance, wireless communication nodes, and other applications require a main energy source, energy storage unit and a back-up energy system. In the last years, fuel cells have become a good replacement for diesel generators in remote and off-grid applications. Fuel cells provide several advantages like high energy efficiency, no moving parts, silent, scaling is a function of their surface area instead of volume, and reliability. Among the disadvantages there are equipment cost, and difficulties in hydrogen storage. Simplifying the control system of the hydrogen feed control will lower the equipment costs and allow the use of this technology for remote applications where the system is mainly fed by renewable sources, like solar panels, and constant maintenance represents an issue.

    For this purpose the present work investigates the use of a single air-breathing micro fuel cell, used as a sensor cell that can serve to control a fuel cell energy backup system. First the sensor cell was tested under different conditions of temperature, hydrogen humidity, flooding, and hydrogen inlet flow in order to determine optimum operation conditions. Then the sensor cell was connected to the hydrogen outlet of a single cell or stack, receiving the remaining hydrogen that was not consumed by the stack. Further tests were performed by modifying the hydrogen flow, resistance value, and stack current output. During the experiments the sensor cell voltage was monitored. The results show that the micro fuel cell delivers a cell voltage signal sensible to the hydrogen inlet flow, which means it can be used to control the operation of a fuel cell stack. The sensibility of the voltage signal can be modified by means of the resistance connected to its circuit. The stability in time of the voltage signal was achieved by setting the sensor cell to 45 °C or higher.

  • 39. Codan, Lorenzo
    et al.
    Bäbler, Matthäus
    Institute of Process Engineering, ETH Zurich.
    Mazzotti, Marco
    Phase Diagram of a Chiral Substance Exhibiting Oiling Out in Cyclohexane2010In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 10, no 9, 4005-4013 p.Article in journal (Refereed)
    Abstract [en]

    This work investigates the ternary phase diagram of the enantiomers of ethyl-2-ethoxy-3-(4-hydroxyphenyl)propanoate (EEHP) in cyclohexane. The enantiomers of EEHP form aconglomerate, and both the pure enantiomer and the racemic mixture exhibit stable oilingout in cyclohexane. Our analysis shows that the ternary phase diagram of such a system assumes a unique structural evolution around the onset temperature of oiling out; that is, we found that the onset of oiling out strictly occurs through the emergence of a second liquid phase of racemic composition. Furthermore, we found that the further evolution of the ternary phase diagram, i.e., above the onset temperature of oiling out, is dictated by the properties of the phase diagrams pure enantiomer/solvent and racemic mixture/solvent. Our theoretical considerations are in excellent agreement with experimental measurements of EEHP in cyclohexane. 

  • 40.
    Cornell, Ann
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Chlorate cathodes and electrode design2014In: Encyclopedia of applied electrochemistry / [ed] R.F. Savinell,K. Ota,G. Kreysa, Springer, 2014, 175-181 p.Chapter in book (Refereed)
  • 41.
    Cornell, Ann
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Chlorate synthesis cells and technology2014In: Encyclopedia of applied electrochemistry / [ed] R.F. Savinell, K. Ota, G. Kreysa, Springer, 2014, 181-187 p.Chapter in book (Refereed)
  • 42.
    Cornell, Ann
    et al.
    KTH, School of Chemical Science and Engineering (CHE).
    Simonsson, Daniel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Ruthenium Dioxide as Cathode Material for Hydrogen Evolution in Hydroxide and Chlorate Solutions1993In: Chlor-Alkali and Chlorate Production/New Mathematical and Computational Methods in Electrochemical Engineering / [ed] T. Jeffrey, K. Ota, J. Fenton och H. Kawamoto, Pennington, New Jersey, USA: The Electrochemical Society , 1993, 191- p.Chapter in book (Refereed)
  • 43.
    Cuvilas, Carlos Alberto
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Mild Wet Torrefaction and Characterization of Woody Biomass from Mozambique for Thermal Applications2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mozambique has vast forestry resources and also considerable biomass waste material such as bagasse, rice husks, sawdust, coconut husks and shells, cashew nut shell and lump charcoal waste. The potential of the total residues from the agricultural sector and the forest industry is estimated to be approximately 13 PJ. This amount of energy covers totally the production of charcoal which amounted to approximately 12.7 PJ in 2006. Although biomass is an attractive renewable source of energy, it is generally difficult to handle, transport, storage and use due to its lower homogeneity, its lower energy density and the presence of non-combustible inorganic constituents, which leads to different problems in energy conversion units such as deposition, sintering, agglomeration, fouling and corrosion. Therefore, a pretreatment of the biomass to solve these problems could lead to a change of current biomass utilization situation. The aim of this study is to convert Mozambican woody biomass residue into a solid biochar that resembles low-grade coal.

    In this work the current energy situation in Mozambique has been reviewed, and the available and potential renewable sources including residues from agricultural crops and forest industry as energy have been assessed. It was found that the country is endowed with great potential for biofuel, solar, hydro and wind energy production. However, the production today is still far from fulfilling the energy needs of the country, and the majority of people are still not benefiting from these resources. Charcoal and firewood are still the main sources of energy and will continue to play a very important role in the near future. Additionally, enormous amounts of energy resources are wasted, especially in the agricultural sector. These residues are not visible on national energy statistics. The chemical composition and the fuelwood value index (FVI) showed that by failing to efficiently utilise residues from Afzelia quanzensis, Millettia stuhlmannii and Pterocarpus angolensis, an opportunity to reduce some of the energy related problems is missed. An evaluation of effect of a mild wet torrefaction pretreatment showed that the chemical composition of the biochar is substantially different than the feedstock. The use of diluted acid as catalysts improves the biochar quality, namely in terms of the energy density and ash characteristics; however, the increment of the S content in the final product should be considered for market acceptance (because the fuels have a maximum allowance for S concentration). The thermal behaviour of the untreated and treated biomass was also investigated. The pyrolytic products of umbila and spruce were affected by the treatment and catalyst in terms of yield and composition of the vapours.

  • 44.
    Deng, Tengfei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Study of Lime Dissolution Under Forced Convection2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 3, 578-586 p.Article in journal (Refereed)
    Abstract [en]

    Dissolution of different CaO cubes under force convection in liquid CaO-"FeO"-SiO2 slag was studied at 1873 K (1600 A degrees C). A linear relationship between normalized lengths and time was obtained after the experiment. It was evidently observed that the removal of the interface layer(s) including 2CaO center dot SiO2 by shear stress was the main mechanism for the dissolution. A stirring rate of approximately 100 rpm was found to be efficient to remove the interface layer(s). The limes with different structures had different dissolution rates.

  • 45. Ehrl, Lyonel
    et al.
    Soos, Miroslav
    Morbidelli, Massimo
    Bäbler, Matthäus
    Institute of Process Engineering, Dept. of Mechanical and Process Engineering, ETH Zurich.
    Dependence of Initial Cluster Aggregation Kinetics on Shear Rate for Particles of Different Sizes Under Turbulence2009In: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 55, no 12, 3076-3087 p.Article in journal (Refereed)
    Abstract [en]

    Initial aggregation kinetics for three particle sizes and broad range of Péclet numbers were investigated under turbulent conditions in stirred tank. This allowed us to observe the transition from diffusion-controlled to purely shear-induced aggregation. The evolution of the root-mean-square radius of gyration, zero-angle intensity of scattered light, and obscuration was obtained by small-angle static light scattering. For a given particle sizethe measured evolution of all integral quantities obtained for various volume averageshear rates (G), scales with a dimensionless time, τexp = αexp × (G) × φ × t. The experimentally obtained aggregation efficiency αexp, follows the power law αexp = Pe-n, where Pe is the primary particle Péclet number. With increasing particle size a decrease in n is observed in accordance with theory and literature data. As previously predicted by population balance equation simulations three aggregationregimes were observed experimentally.

  • 46.
    Ek, Mattias
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Shu, Q. F.
    van Boggelen, J.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    A new approach towards dynamic modelling of dephosphorisation in converter process2012In: Ironmaking & steelmaking, ISSN 0301-9233, Vol. 39, 77-84 p.Article in journal (Refereed)
    Abstract [en]

    A new approach was made to model the dephosphorisation process in a 300 tons basic oxygen furnace converter with three argon gas inlets. The main feature of the new approach was to utilise the velocity vectors obtained by computational fluid dynamics (CFD) simulation in a standalone model. The CFD simulation was carried out using commercial software COMSOL Multiphysics. In the standalone model, the steel melt domain was sliced into 1000 cells. The calculated velocity vector in each cell was assumed constant. Based on the imported velocity vectors from the CFD calculation, the mass transfer of carbon and phosphorus was calculated by taking into account the slag-metal reactions. The mass exchange between slag and metal was considered to be dominated by the metal droplet formation due to the oxygen jet. The convergence of the model calculation and the promising comparison between the model prediction and the industrial data strongly suggested that the proposed approach would be a powerful tool in dynamic process control. As a preliminary step, the model only simulated the process after the formation of slag-metal-gas emulsion. Note that the present work is intended to establish a structure of the model. More precise descriptions of other process aspects need to be included before the model can be practically employed in a dynamic controlling system.

  • 47.
    El Azab, Ahmad
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Modeling of Biofuel Combustion2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Fortum Scandinavia’s future challenge is to develop the district heating system to be able to meet costumers and societies demand for affordable and sustainable heating. One way to reach those goals is to use biofuels in the coal-fired power and heating plant KVV6 at Värtaverket in Stockholm. Different types of biofuels could be used but it is important to understand their combustion processes and the chemical characteristics of the biofuels. During this project olive stone cross, palm shell kernel (PKS), lignin and the liquid biofuel crude glycerol where tested in a lab-scale combustor fitted with a quartz cylinder. The combustion process was filmed and the results showed that palm shell kernel is a very promising fuel to be used instead of coal, with glycerol used as a substituted for water to make paste, which is needed to be able to pump the fuel in to the PFBC at KVV6. The biofuels where also tested for alkali where the results showed that PKS have very low amounts of alkali while the glycerol have very high amounts which would be unfavorable in the PFBC at KVV6. Olive stone cross and lignin are also good substitutes for coal but they do have higher amounts of alkali compared to PKS.

  • 48.
    Elm Svensson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Nanomaterials for high-temperature catalytic combustion2007Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Catalytic combustion is a promising technology for power applications, especially gas turbines. By using catalytic combustion ultra low emissions of nitrogen oxides (NOX), carbon monoxide (CO) and unburned hydrocarbons (UHC) can be reached simultaneously, which is very difficult with conventional combustion technologies. Besides achieving low emission levels, catalytic combustion can stabilize the combustion and thereby be used to obtain stable combustion with low heating-value gases. This thesis is focused on the high temperature part of the catalytic combustor. The level of performance demanded on this part has been proven hard to achieve. In order to make the catalytic combustor an alternative to the conventional flame combustor, more stable catalysts with higher activity have to be developed.

    The objective of this work was to develop catalysts with higher activity and stability, suitable for the high-temperature part of a catalytic combustor fueled by natural gas. A microemulsion-based preparation method was developed for this purpose in an attempt to increase the stability and activity of the catalysts. Supports known for their stability, magnesia and hexaaluminate, were prepared using the new method. The microemulsion method was also used to impregnate the prepared material with the more active materials perovskite (LaMnO3) and ceria (CeO2). It was shown that the microemulsion method could be used to prepare catalysts with better activity compared to the conventional methods. Furthermore, by using the microemulsion to apply active materials onto the support a significantly higher activity was obtained than when using conventional impregnation techniques.

    Since the catalysts will operate in the catalytic combustor for extended periods of time under harsh conditions, an aging study was performed. One of the most stable catalysts reported in the literature, LMHA (manganese-substituted lanthanum hexaaluminate), was included in the study for comparison purposes. The results show that LMHA deactivated much more strongly compared to several of the catalysts consisting of ceria supported on lanthanum hexaaluminate prepared by the developed microemulsion method.

  • 49.
    El-Seedi, Hesham R.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. Uppsala University, Sweden.
    Azeem, Muhammad
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. COMSATS Institute of Information Technology, Pakistan.
    Khalil, Nasr S.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. Agricultural Research Centre, Egypt.
    Sakr, Hanem H.
    Khalifa, Shaden A. M.
    Awang, Khalijah
    Saeed, Aamer
    Farag, Mohamed A.
    AlAjmi, Mohamed F.
    Pålsson, Katinka
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Essential oils of aromatic Egyptian plants repel nymphs of the tick Ixodes ricinus (Acari: Ixodidae)2017In: Experimental & applied acarology, ISSN 0168-8162, E-ISSN 1572-9702, Vol. 73, no 1, 139-157 p.Article in journal (Refereed)
    Abstract [en]

    Due to the role of Ixodes ricinus (L.) (Acari: Ixodidae) in the transmission of many serious pathogens, personal protection against bites of this tick is essential. In the present study the essential oils from 11 aromatic Egyptian plants were isolated and their repellent activity against I. ricinus nymphs was evaluated Three oils (i.e. Conyza dioscoridis L., Artemisia herba-alba Asso and Calendula officinalis L.) elicited high repellent activity in vitro of 94, 84.2 and 82%, respectively. The most active essential oil (C. dioscoridis) was applied in the field at a concentration of 6.5 A mu g/cm(2) and elicited a significant repellent activity against I. ricinus nymphs by 61.1%. The most repellent plants C. dioscoridis, C. officinalis and A. herba-alba yielded essential oils by 0.17, 0.11 and 0.14%, respectively. These oils were further investigated using gas chromatography-mass spectrometry analysis. alpha-Cadinol (10.7%) and hexadecanoic acid (10.5%) were the major components of C. dioscoridis whereas in C. officinalis, alpha-cadinol (21.2%) and carvone (18.2%) were major components. Artemisia herba-alba contained piperitone (26.5%), ethyl cinnamate (9.5%), camphor (7.7%) and hexadecanoic acid (6.9%). Essential oils of these three plants have a potential to be used for personal protection against tick bites.

  • 50.
    Faramarzi, Simin
    KTH, School of Chemical Science and Engineering (CHE).
    Effect of Alternative Fuels on SCR Chemistry2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the time line of world industrial age, the most important era begins in the late 18th century when the use of fossil fuels was growing intensively. This approach has continued and developed up to the 20th century. Besides, this trend has had side effects like polluting environment. Air pollution is one of the critical issues nowadays that stems from using hydrocarbon fuels.

    One type of the problematic compounds in polluting air is nitrogen oxides that can be produced in combustion process from engines and industrial plants. Different solutions have been suggested to remove air polluting compounds. One method for removing nitrogen oxides is using the mechanism of Selective Catalytic Reduction in silencer of engines. This method has become practical in trucks’ engines.

    Therefore, research on SCR chemistry is important for improving the usage of this method in removing nitrogen oxides. SCR has its own problems when used in trucks. One of the problems is formation of white clumps on pipe wall of silencers using SCR which can cause back pressure in the engines and costs a lot to remove them from engines.

     This report evaluates the effect of alternative fuels on SCR chemistry .Different parameters affecting deposit formation are studied and evaluated. Ethanol is one of the controversial fuels used in engines and acetic acid is one its byproducts. Also, urea and its by products are important materials in SCR chemistry, too. Consequently, the first part of the report studies the influence of acetic acid and Ferrite steel, one of the usual steels in silencers of engines, on urea, biuret and cyanuric acid decomposition. The instruments used in the first part include TGA-DSC (Thermo Gravimetric Analysis-Differential Scanning Calorimetric) which is connected to FTIR (Fourier Transform Infrared Spectroscopy).In the second part of the report, the effect of diesel exhaust and ethanol exhaust on cyanuric acid evaporation rate is evaluated. Cyanuric acid is the main compound forming deposit in silencers. The instrument used in the second part is TGA. The third part consists surveying effect of Adblue, aqueous solution of urea, and additivised Adblue, surfactant added Adblue to improve its efficiency, in a patented rig that is scaled down of a silencer of truck.

    The most important result for the first part includes the effect of Ferrite steel treated with acetic acid that accelerated the decomposition of cyanuric acid. This result can be investigated more in order to be used in silencers to accelerate the decomposition rate of clumps formed. In the second part, it is found out that cyanuric acid evaporates faster under ethanol exhaust than diesel exhaust. The third part’s results shows that in the current assembly of pipes in the rig, Additivised Adblue loses its improved efficiency which is an interesting result for engine welding in order to avoid this type of connection in engines.

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