The aging of bipolar plates in the polymer electrolyte membrane fuel cell was evaluated using different accelerated degradation tests. From previous studies, it is well known that the startups and shutdowns of a polymer electrolyte membrane fuel cell is the primary cause of fuel cell component degradation. Therefore, the aim of these tests was to simulate the number of startups/shutdowns that normally occur during the lifetime of a polymer electrolyte membrane fuel cell, e.g. for automobile applications. The tests were carried out in situ in order to be as realistic and close to operational conditions in real applications as possible. Mechanical stress and degradation normally occurring during polymer electrolyte membrane fuel cell operation was thereby included. The accelerated degradation tests were designed for maximum fuel cell stress, including use of the no purge and the air purge strategy, short cycle duration as well as an increased number of startups/shutdowns. Since the no purge strategy avoids prevention of local H 2/O2 fronts, this strategy was implemented first. Other strategies e g the air purge strategy, where air is used to purge the anode, where also implemented. Parameters influencing the tests were varied and the cathode gas was changed between O2 and air depending on the test. Electrochemical methodology was implemented for the detection of corrosion in the tests and for analysis/ studies of the test results. These techniques include cell voltage/current readings, polarization curves, electrochemical impedance spectroscopy, contact resistance and current density decrease at constant cell voltage. In addition, scanning electron microscope was used to visualize the actual corrosion of the bipolar plates. It was found that implementation of the air purge strategy resulted in localized corrosion, i.e. oxide film formation, on the surface of the bipolar plates increasing both the corrosion resistance and the interfacial contact resistance. / Åldrandet av bipolära plattor i polymerelektrolytbränslecellen undersöktes med hjälp av olika accelererade nedbrytningstest. Från tidigare studier är det känt att uppstarterna och avstängningarna av denna typ av bränslecell är den främsta orsaken till nedbrytningen av bränslecellskomponenterna. Av den anledningen var syftet med dessa test att simulera antalet uppstarter och avstängningar som normalt sker under en polymerelektrolytbränslecells livstid t ex för tillämpningar i fordon. Testen utfördes in situ för att vara så realistiska och så nära driftsförhållandena i verkliga tillämpningar som möjligt. Därmed inkluderades mekanisk påfrestning och nedbrytning som normalt sker under drift i en polymerelektrolytbränslecell. De accelererade nedbrytningstesterna utformades för maximal bränslecellspåfrestning. Detta åstadkoms bl a genom tillämpning av den s k "no purge"och "air purge " strategin, kort cykeltid samt ett utökat antal uppstarter/avstängningar. Eftersom "no purge" strategin eliminerar förebyggandet av H 2/O2 fronter, testades denna strategi först. Andra strategier tillämpades också som t ex "air purge" strategin, där luft fick "rena" anodsidan. Parametrar som påverkar testen varierades och katodgasen skiftades mellan O2 och luft beroende på experimentet. Elektrokemisk metodik användes för att detektera nedbryning i de olika testen och för att studera testresultaten. Dessa tekniker omfattade cellspänning/ -ström mätningar, polarisationskurvor, elektrokemisk impedans spektroskopi, kontaktresistens och strömtäthetsminskning vid konstant cellspänning. Svepelektronmikroskopi användes för att visualisera den fysiska nedbryningen av de bipolära plattorna. Det visade sig att "air purge" strategin gav upphov till korrosion i form av lokal oxidbildning på de bipolära plattornas yta. Detta ökade både korrosionsmotståndet och kontaktresistensen i gränsskiktet.

It is vital that a dry powder inhaler device has the ability to protect the quality of the drug product inside during storage and usage. This is achieved by integrating a drying agent. It is well known that porous material has good moisture sorption properties. These properties are affected by the surface energy and contact area between the adsorbent and in this case surrounding air. In this study three types of adsorbents were studied. The porous materials have been tested by characterization methods such as the BET method and water uptake measurements to identify the most promising type. Methods showed that for low relative humidity levels molecular sieves had the highest water sorption capacity and for higher levels of humidity silica gels including the reference sample, dominated in sorption capacity which also possessed the highest surface area amongst the samples. Molecular sieves were least affected by smaller temperature changes. Based on the results a recommendation is made for the most promising desiccant for dry powder inhalers. It was shown that the reference sample had highest surface area and capacity at 50 % relative humidity. / Det är av yttersta vikt att en torrpulverinhalator har förmågan att skydda läkemedlets kvalitét inuti under förvaring och användning. Detta kan uppnås med ett inbyggt torkmedel. Det är väl känt att porösa material har goda vatten sorptions egenskaper. Dessa egenskaper påverkas av ytenergin och kontaktarean mellan adsorbent och i detta fall omgivande luft. I denna studie har olika material testats genom karaktäriseringsmetoder så som BET-metoden och fuktupptag mätningar för att kunna identifiera det mest lovande alternativet. Metoderna visade att för låg relativ fuktighet visade molekylsikt den största adsorptions kapaciteten och för hög relativ fuktighet dominerar kiselgeler inklusive referensprovet som motsvarar torkmedlet som används idag, och som även visade högst ytarea bland proverna. Molekylsikt var minst påverkad av mindre temperaturändringar. Baserat på resultaten görs en rekommendation för det mest lovande torkmedlet för torrpulverinhalatorer. Referensprovet visade sig ha störst kapacitet i 50% RH och störst ytarea.

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The thesis deals with various ways of utilization of biomass. Chapter 1 compares three biomass types: birch wood Betula sp., marine brown alga Fucus vesiculosus, and terrestrial moss Pleurozium schreberi, as precursors for preparation of biosorbents for removal of copper ions from diluted water solutions. Small sample doses (0.5 g/100ml) of the biosorbents prepared from alga and moss enabled more than 90 % removal of Cu (II) ions from diluted water solutions (5-20 mg/l). The sample from birch wood was less effective. The maximum sorption capacities (Xm) determined from the experimental equilibrium isotherms by applying the Langmuir model showed that the alga had the best copper-binding ability (Xm = 23.4 mg/g), followed by the moss (Xm = 11.1 mg/g), and the sawdust (Xm = 4.9 mg/g). The performance of the biosorbent prepared from birch was not satisfactory. The regeneration of the sorbents from alga and moss was performed using diluted HCl as eluent. No visible damages or performance losses were detected after five sorptiondesorption cycles. Chapter 2 deals with MnOx-Pd/Alumina-La catalysts for abatement of the emissions from wood combustion. Of primary interest is the calcination temperature used in preparation of the catalysts. Several catalysts are prepared using various calcination temperatures, 500, 600, 700 and 800 oC for 4 h in air and their activities and stabilities are compared. The activity tests were performed using gaseous mixtures containing combustibles representative for the flue gases from wood combustion, carbon monoxide (2500 ppm), methane (200 ppm) and naphthalene (50 ppm). The catalytic oxidation tests were performed in presence of 10 % O2, 12 % H20, 12 % CO2 and N2 (balance). The concentrations of the components in the gaseous mixture and the total flow of the mixture correspond to those in the flue gases from combustion (gas flow 2.5 l/min corresponding to a space velocity of approximately 20000 h-1). In presence of the catalysts carbon monoxide (CO) and naphthalene (C10H8) ignite almost simultaneously in the interval 150-200 ºC and are totally converted at temperatures a little above 200 ºC. The light-off temperatures of methane (CH4) are in the interval 600-650 ºC, and total conversion is reached at around 700 ºC. The most suitable calcination temperature for the catalysts prepared here is 700 ºC. Lower temperatures, 500 and 600 ºC, seem to result in formation of less stable catalysts. The catalysts calcined at higher temperature, 800 ºC, have stable performance in repeated tests, but lower activity. Chapter 3 presents results from literature study on corrosion and deposit formation in combustion of biofuels. Contributing to understanding the reasons for corrosion and the methods for its abatement are the primary goals. The scope is limited to deeper insight of the role of chlorine and alkali in combustion of biomass and the possibilities for hampering their corrosive effects. The role of additives decreasing the corrosion and deposit formation as well as the effect of water and the prospective for availability of low-chlorine biofuels have also been examined. / QC 20101105

In order to secure the energy supply to an increasing population and at the same time limit the damage to Earth, i.e. avoiding a fatal climate change as a result of anthropogenic emissions of greenhouse gases (primarily CO2), immediate action is necessary. This includes reducing the energy consumption, increasing the energy conversion efficiency, and using renewable energies. The transport sector is the one most dependent on fossil energy and it stands for a significant part of the energy consumption in the world. For instance, in EU-25 transportation stands for 30 % of the total final energy consumption and relies to 98 % on oil. Being the only renewable energy possible to convert into liquid fuels biomass, as a means for reducing the CO2 emissions from the transport sector, will play an important role in the near future. The conversion of biomass into transportation fuels is preferentially done via gasification followed by the fuel synthesis. The whole production chain from biomass to final fuel is very dependent on R&D, in order to become competitive with the fossil fuels. Fischer-Tropsch (FT) diesel made from biomass is a viable option for reducing the CO2 emissions from transportation since it may be blended with conventional diesel in any concentration. Furthermore, since its composition is almost the same as of petroleum-based diesel (although cleaner) the same distribution system and engines may be used, which facilitates its introduction on the market. This thesis presents the results of the laboratory work performed in 2003 – 2007 at the Department of Chemical Technology, KTH, and at the Department of Chemical Engineering, NTNU (the Norwegian University of Science and Technology) in Trondheim. Part of the work has been performed in close cooperation with the Department of Chemical and Biological Engineering at Chalmers University of Technology. All FT experiments were performed in a fixed-bed reactor at 210 ºC and 20 bar. Pure mixtures of H2, CO and N2 were used as feed to the reactor. Steam was also occasionally introduced. Selectivity to C5+ was used as a measure of the catalysts’ ability to grow long-chain hydrocarbons, which is desirable when diesel is the product aimed for. The first part of the thesis deals with the direct conversion of a H2-poor syngas, which is obtained upon gasification of biomass, into FT hydrocarbons. “H2-poor” means that the H2/CO ratio is lower than what is required by the stoichiometry (~ 2.1) of the FT synthesis (reaction 1). In order to increase the H2/CO ratio to the required one, internal water-gas-shift (WGS) is needed (reaction 2). FT: CO + 2H2  “-CH2-“ + H2O (1) WGS: CO + H2O  CO2 + H2 (2) The H2/CO usage ratio has been used as a measure for the internal WGS activity, it is defined as follows: where S is the selectivity (of total C-containing products), and the factor F indicates the number of H2 moles required for one CO mole to form the product (e.g. for producing high molecular weight n-paraffins, 2 moles of H2 per mole of CO are required). For the fraction C2 – C4, F will have different values depending on the selectivity to C2, C3 and C4, and it also depends on the olefin/paraffin ratios for those hydrocarbons. In order to reach the highest once-through conversion of the syngas, the H2/CO usage ratio should be equal to the inlet H2/CO ratio. The lower the usage ratio, the higher the relative WGS activity. The combined FT and WGS reactions with H2-poor syngas have been tested for 12 wt% Co and 12 wt% Co – 0.5 wt% Re catalysts supported on γ-Al2O3. It was found that with lower H2/CO ratios in the feed, the syngas conversion and the CH4 selectivity decreased, while the C5+ selectivity and olefin/paraffin ratio for C2-C4 increased slightly. The WGS activity was low for all catalysts, implying a H2/CO usage ratio close to the stoichiometric one (2.1), even for inlet H2/CO ratios of 1.5 and 1.0. By incorporating significant amounts of Fe (20 % of total metal) in the Co catalyst referred to above (by co-impregnation) in order to achieve a 12 wt% bimetal loading on γ-Al2O3, a slightly lower usage ratio was obtainable (1.92) for an inlet ratio of 1.0 for dry conditions. Different Fe:Co ratios ranging from 100 % Fe to 100 % Co (12 wt% bimetal) were tested for an inlet H2/CO ratio of 1.0. The characterisation results indicated that Fe was enriched at the surface, hence covering the more FT-active Co sites, even at low percentage Fe. Not even upon significant replacement of Co by Fe (≥ 20 %) were the usage ratios for dry conditions lowered to any significant extent. The WGS reaction at the low temperature used could be boosted by addition of external water. However, since the catalysts with the highest WGS activity had surface enrichment of Fe, high water partial pressures negatively affect the FT rate and also lead to rapid deactivation by re-oxidation of the FT-active iron phases (iron carbides) or by sintering. Surprisingly, also the WGS activity rapidly deactivated at high partial pressures of water, although Fe3O4 is believed to be the WGS-active phase. Possibly, surface oxidation of Fe3O4 into γ-Fe2O3 may take place during these water-rich conditions. The WGS reaction (reaction 2) is thermodynamically favoured at low temperatures. However, the WGS kinetics over the tested catalysts is far too slow at the FT reaction temperature used in typical low-temperature FT (LTFT) applications, with diesel as the desired product. The second part of this thesis deals with the hydrocarbon selectivity over Co-based catalysts in the FT synthesis with stoichiometric H2/CO feed. An alternative catalyst preparation technique, the microemulsion (ME) technique, was used as a complement to the conventional incipient wetness (IW) impregnation. A great deal of effort was put into the development of the synthesis of Co particles of monodisperse size in a ME and the subsequent deposition of these onto a porous support material. By using the ME technique it was possible to prepare relatively small Co particles in a large-pore support such as TiO2, which is not an easy task using the conventional impregnation technique. With the prepared ME catalyst on TiO2 it was possible to study the effect of Co particle size on FT selectivity irrespective of the pore size of the support. It was found that, at least for Co particles above 10 nm, it is not the Co particle size that is the principal parameter determining the selectivity of a catalyst, but rather the physical and/or chemical properties of the support. Due to the smaller Co particle size (~ 12 nm) of the ME-TiO2 catalyst as compared to a corresponding IW catalyst (~ 26 nm) supported on TiO2, the FT activity of the former was 100 % higher as fresh catalyst. After 120 h on stream the ME catalyst still gave 60 % higher rate to C5+ (expressed as gC5+/gcat,h) compared to both an IW-TiO2 and an IW-γ-Al2O3 catalyst, all catalysts having the same composition (12 wt% Co, 0.5 wt% Re). / QC 20101112

To fully understand the elementary reactions behind the ignition of automotive fuels the interaction between the fuel components must be known. The ignition initiation is most often caused by loss of an H radical from a reactive fuel molecule, for example n-heptane. The formed alkyl radical is prone to react with oxygen under lean conditions. However, it can also abstract hydrogen from other fuel molecules, hence activating more unreactive species. This type of reactions is called cooxidation reactions and including it in combustion mechanisms improve ignition delay predictions in a wide range of experiments, for Primary Reference Fuel mixtures and toluene/heptane mixtures. Example of such reactions are C7H15• + C8H18 = C7H16+ C8H17• C7H15OO• + C8H18 = C7H15OOH+ C8H17• Adding cooxidation reactions also significantly improves prediction of the general trend of auto-ignition phasing as function of operating conditions in Homogeneous Charge Compression Ignition, HCCI, engine combustion. The effect of NO addition on engine combustion has also been studied in this work. A novel strategy to control ignition onset in HCCI engines is to retain exhaust gases in the cylinder to control the cylinder temperature. While this not only controls the engine temperature it also introduces NOx in the cylinder. The NO will advance ignition onset by several crank angle degrees at concentrations below 10 ppm. This is because NO activates HO2 in the reaction: HO2• + NO = OH• + NO2. At higher concentrations the ignition onset is not as advanced and in the PRF case even retarded. This is because NO has cool flame-inhibiting effects. Kinetic modelling can also be used to predict combustion efficiency in catalytic combustors for power generation. It was shown that at high pressures the number of free sites decreases which limits the combustion efficiency. Thus a hybrid concept could be used where only a fraction of the air and fuel is burned catalytically. / QC 20101109

A literature study on several properties of poly-L-lactic acid (PLLA) and their effect on the regenerative proper-ties was conducted. Crystallinity, porosity, functionalization and methods for different modifications of PLLAare discussed. PLLA is a biopolymer with the L-conformation of the polymer. The biopolymer has been widelyused in medical applications in the last years. The applications include e.g. bone and tissue scaffolds for re-generative properties. PLLA has shown ability to induce skin regeneration via foreign body reaction (FBR)and subclinical inflammation, hence creating an increased amount of collagen in the dermis layer of the skin.The main modulator of the FBR has been identified as the macrophage response to the biomaterial in vivo.Therefore, it is important to consider macrophage interaction with the biomaterial when developing new ormodifying existing biomaterials. Porosity and particle size have been identified as factors that may affect theintensity of the FBR, but the role of these factors need further elucidation. The changes in surface topographyon the PLLA scaffolds could affect cell adhesion, but the ratio in which the functionalization should be done tothe surface is still unsure. PLLA is a biodegradable polymer and the degradation occurs mainly by hydrolysisin vivo. The degradation rate of the PLLA scaffolds may be altered by modifying the crystallinity and porosityof the material or incorporation of other functional groups in the scaffolds. The degree of crystallinity in thePLLA scaffolds need to be optimized for the best regenerative properties, the favorable results from the studysuggested around 40 %. Too high crystallinity may lead to negative impacts on biocompatibility and cell adhe-sion. To modify PLLA, the most promising techniques are electrospinning, electrospraying, plasma depositionand thermally induced phase separation. These methods were also good from an economic and environmentalpoint of view

Mälsta farm is a small private farm without commercial production located in Knivsta. Theowner’s vision for the farm is to reduce its environmental impact as much as possible andminimize the amount of purchased electricity and to be able to be completely self-sufficientduring shorter periods. To achieve this goal the owner has shown an interest in installing ananaerobic digestion system to produce electricity. The anaerobic system of interest is the Greenanaerobic digestion system provided by ENNUWA. The owner was interested in answering ifthe installation of the system would be economically viable, how much electricity that couldbe produced from the animal manure, food waste and blackwater produced at the farm, as wellas if there are any other available biomasses that can be used.The project was provided to the authors via STUNS Energy. To answer the questions of interestthe authors conducted literature research through Web of Science, Science Direct, GoogleScholar and the Uppsala University Library search engine. The results from the research wereapplied to Mälsta farm and the Green anaerobic digestion system. It was estimated that withthe available biomass at the farm between 2367 and 3956 kWh of electricity could be producedassuming an electrical conversion efficiency of 35%. A simple economic model wasconstructed to estimate the years until return on investment (ROI). The model estimated theyears until ROI for the installation of the GREEN anaerobic digestion system to be between 90and 151 years.

<p>This thesis describes a new general purpose dynamic process simulator applied to a natural gas liquefaction plant. More specifically, the Multi Fluid Cascade Process (MFCP). MFCP is the “Statoil Linde LNG Technology Alliance” - a proprietary and patented process for LNG production. This utilizes plate fin and spiral wound heat exchangers, produced by Linde AG, and Nuovo Pignone’s centrifugal compressors. This LNG technology is now being implemented for the Hammerfest baseload LNG project, Snøhvit.</p><p>The simulator is based on first principle conservation laws for energy and mass, and a simplified quasi-steady state momentum equation. Unit models for the process equipment (tanks/pipes, separation tanks, valves, liquid expanders, pumps, compressors, heat exchangers, and PI controllers) are described using rigorous thermodynamics. Equilibrium is assumed for all unit models, and equilibrium and physical properties are predicted with the Swoave-Redlich-Kwong or the Peng-Robinson equation of state.</p><p>Two different model approaches are compared in this work. One approach conserves energy in an enthalpy state, and the other conserves internal energy, the HP formulation and UV formulation respectively. The HP formulation defines a dynamic state for the pressure, and splits the integration of the fast and slow dynamics. The pressure states and the algebraic flow relations are solved by a fully implicit Euler method, while the internal unit model equation is solved locally with tailormade integration routines. The UV formulation, utilizes an analytical Jacobian, and is integrated with both a 1-stage Rosenbrock and freeware BDF codes.</p><p>The UV formulation generates an analytical Jacobian from physical property partial differentials. These property differentials are calculated from a first order approximation of the equilibrium. The equilibrium equations are linearized in dynamic state variables to produce partial differentials of the internal flash variables.</p><p>The simulator is tested on a portable PC. The full MFCP LNG plant is simulated with a fixed time step of 1.0 seconds, for both the HP and UV formulations.</p><p>The HP formulation has 611 ODE states. The UV formulation uses the 1-stage Rosenbrock method integrating a system with 1025 ODE states. The case simulated is a set point step for the LNG temperature controller. The plant is simulated over 9000 seconds. The major process dynamics are sampled every second, and plotted. The average performance of both formulation is better that 7 times real time. The worst local performance of the UV formulation is 1.7 times faster than the HP formulation, but more than 6 times faster than real time. The HP and UV formulations gave significantly different dynamic predictions.</p><p>The BDF codes proved too slow for practical use on the MFCP configuration.</p><p>The dynamic simulators in industry today are typically using a HP formulation, with precalculated thermodynamic data stored in look-up tables. The simulations of the full LNG plant show that simulators, utilizing EOS equilibrium descriptions, soon will be able to compare with modern industry simulators.</p>

<p>Separation of azeotropic mixtures is a topic of great practical and industrial interest. Most liquid mixtures of organic components form nonideal systems. The presence of some specific groups, particularly polar groups (oxygen, nitrogen, chlorine and fluorine), often results in the formation of azeotropes. Azeotropic mixtures may often be effectively separated by distillation by adding a liquid material (entrainer) to the system.</p><p>For the development of separation processes for azeotropic mixtures, there is a need for insight into the fundamental phenomena of nonideal and azeotropic phase equilibria. This thesis includes a detailed survey on azeotropic phase equilibriumdiagrams of ernarymixtures. Diagram analysis is shown to be an efficient tool for prediction of feasible separations. As a simplifying concept it is proposed that all feasible structures of ternary azeotropic phase equilibrium diagrams can be qualitatively represented by a few elementary cells of which only four have so far been reported to exist. This greatly reduces the complexity of azeotropic istillation analysis and is a key to a simple evaluation of the possibilities and limitations of azeotropic mixtures separation.</p><p>Insights gained from continuous azeotropic distillation is extended to the operation of batch distillation with focus on the dynamics and control of multivessel and extractive batch distillation as processes for separating azeotropic mixtures. Practical implications of this renewed insight for the fine- and specialty chemical industries are given in the concluding pages of the thesis.</p>