In der vorliegenden Arbeit werden verschiedene Simulationsansätze angewandt um die Hydrodynamik in einem neu entwickelten Wirbelschichtvergaser zu untersuchen. Die Ansätze umfassen a) entdimensionalisierter Ähnlichkeitskennzahlen und empirischer Gleichungen, b) 1D Simulationen mittels ASPEN Plus®, c) 3D CFD Simulationen mittels Ansys Fluent® zur detaillierten Abbildung der zu erwartenden Hydrodynamik. Vor- und Nachteile der jeweiligen Ansätze sowie Klassen von ermittelbaren Simulationsdaten werden diskutiert. Ein Schwerpunkt der Arbeit liegt in der Identifizierung geeigneter Experimente aus der Literatur, auf Basis von Ähnlichkeitskennzahlen, um die Simulationen zu validieren. Die Vergasersimulationen zeigen, dass sich erwartungsgemäß ein aus hydrodynamischer Sicht gestufter Prozess ausbildet. Die entstehenden Zonen lassen sich als Festbett, blasenbildende Wirbelschicht, Jet-Wirbelschicht mit Rezirkulationszelle und strähnenbildende, zirkulierende Wirbelschicht identifizieren und entsprechen demnach dem Verfahrensanspruch.:1 INTRODUCTION 1 1.1 Market Situation 1 1.2 Objective Work 3 1.3 Structure of this Work 4 2 FUNDAMENTAL CONSIDERATIONS 5 2.1 Fundamentals of Gasification and Gasifiers 5 2.1.1 Counter-Current Fixed-Bed Gasifiers 7 2.1.2 Fluidized-Bed Gasifiers 9 2.1.3 Entrained-Flow Gasifiers 10 2.1.4 Technology Development Trends 11 2.1.5 Conclusion 12 2.2 Fundamentals of Fluidized-Bed Systems 13 2.2.1 Particle Characterization 13 2.2.2 Types of Fluidized Beds and Key Parameters 15 2.2.3 Fast-Fluidized Beds 18 2.2.4 Jetting-Fluidized Beds 19 2.2.5 Spouted Beds 24 2.2.6 Conclusion 27 3 APPROACHES TO ASSESS FLUIDIZED BEDS 28 3.1 Empirical Simulation 28 3.1.1 Nondimensional groups 28 3.1.2 Conclusion 36 3.2 Simulation with ASPEN Plus® 36 3.3 CFD Simulation 38 3.3.1 Modelling Approaches for Numerical Simulation of Fluidized Beds 38 3.3.2 Two Fluid Model (TFM) 40 3.3.3 Kinetic Theory of Granular Flow (KTGF) 44 3.3.4 Conclusion 46 4 COORVED GASIFICATION CONCEPT 48 4.1 Concept of Staged Conversion 48 4.1.1 Drawbacks of Conventional Fluidized-Bed Gasifiers 48 4.1.2 Basic Concept COORVED Gasifier 49 4.1.3 COORVED – Fixed-Bed Zone 49 4.1.4 COORVED – Bubbling-Bed Zone 50 4.1.5 COORVED – Jetting-Bed Zone 50 4.1.6 COORVED – Fast-Bed Zone 51 4.1.7 Conclusion 51 4.2 Test Facility and Reactor Design 52 4.3 Cold Flow Test Unit 53 4.4 Reference Cases 54 4.4.1 Solids Characterization 54 4.4.2 Gas Phase Properties 54 5 COORVED REACTOR IN FLOW REGIME DIAGRAMS 56 5.1 Reh Diagram for the Reference Case 56 5.2 Reh Diagram for Experimental Campaigns and CFD Case 57 5.3 Regime Diagrams for the Jetting-Bed Zone 60 5.4 Conclusion 61 6 CFD SIMULATION OF COORVED REACTOR 62 6.1 Verification of Multiphase CFD Setup 62 6.1.1 Parallelization 64 6.1.2 Pressure Drop and Minimum Fluidization Velocity 65 6.1.3 Conclusion 67 6.2 Grid Study 68 6.2.1 Pressure Drop 69 6.2.2 Voidage Profiles 69 6.2.3 Velocity Profiles 71 6.2.4 Conclusion 72 6.3 Validation Experiment Bubbling Bed and Fast Bed 72 6.3.1 Experimental Setup Holland 73 6.3.2 Simulation Setup 75 6.3.3 Results 77 6.3.4 Conclusion 84 6.4 Validation Experiment Jetting Bed 85 6.4.1 Experimental Setup 85 6.4.2 Simulation Setup 87 6.4.3 Results 88 6.4.4 Conclusion 95 6.5 CFD Simulation COORVED 96 6.5.1 Computational Grid 97 6.5.2 Cold Flow, Single Phase Jet 97 6.5.3 CFD setup 99 6.5.4 Results 99 6.5.5 Conclusion 103 7 ASPEN PLUS® SIMULATION OF THE COORVED GASIFIER 105 7.1 Validation Experiment Bubbling Bed and Fast Bed 105 7.2 COORVED Simulation 107 7.3 Conclusion 108 8 SUMMARY 109 9 OUTLOOK 114 9.1 Modeling Tools 114 9.2 COORVED Development 114 10 APPENDIX 115 11 REFERENCES 120

Nowadays, manufacturing technologies become more and more aware of efficiency and sustainability. One of them is the so called 3D printing. While 3D printing is often linked to plastic, the truth is there are many other materials that are being tested which could have several improvements over plastics.One of these options is stone or concrete, which is more suitable the architecture and artistic fields. However, due to its nature, this new technology involves the use of new techniques when compared to the more commonly used 3D printers. This implies that it could interesting to know how much energy efficient these techniques are and how can they be improved in future revisions.This thesis is an attempt to disclose and analyze the different devices that make up one of these printers and with this information, build a model that accurately describes its behavior.For this purpose, the power is measured at many points and later it is analyzed and fitted to a predefined function. After the fitting has been done, an error is calculated to show how accurate the model is when compared to the original data.It was found that many of these devices produce power spikes due to its nonlinear behavior. This behavior is usually related to switching, and can avoided with different devices.Finally, some advice is given focused on future research and revisions, which could be helpful for safety, efficiency and quality. / Numera blir tillverkningstekniken alltmer medveten om effektivitet och hållbarhet. En av dem är den så kallade 3D­utskriften. Medan 3D­utskrift ofta är kopplad till plast, är verkligheten att det finns många andra material som testas, vilket kan ha flera förbättringar över plast.Ett av dessa alternativ är sten eller betong, vilket är mer lämpligt inom arkitektur och konstnärliga fält. På grund av sin natur inbegriper denna nya teknik användningen av nya tekniker jämfört med de vanligare 3D­skrivarna. Detta innebär att det kan vara intressant att veta hur mycket mer energieffektiva dessa tekniker är och hur de kan förbättras i framtida revisioner.Denna avhandling är ett försök att studera och analysera de olika enheter som utgör en av dessa skrivare och med denna information, bygga en modell som exakt beskriver dess beteende.För detta ändamål mäts effekten på många punkter och senare analyseras och anpassas den till en fördefinierad funktion. Efter anpassning har gjorts beräknas felet för att visa hur exakt modellen är jämfört med originaldata.Det visade sig att många av dessa enheter producerar spännings­spikar på grund av dess olinjära beteende. Detta beteende är vanligtvis relaterat till omkoppling och kan undvikas med olika enheter.Slutligen ges några råd om framtida forskning och revideringar, vilket kan vara till hjälp för säkerhet, effektivitet och kvalitet.

This doctoral work was developed in the frame of bone tissue engineering, dealing with the fabrication of scaffolds for the regeneration of bones. At this purpose, calcium phosphates derived from natural sources are very interesting because they are more similar to the bone mineral and possess better bioactivity. Indeed, the bone mineral is different from synthetic hydroxyapatite as it is non-stoichiometric, nanosized, it presents a high degree of disorder and contains many additional ions and impurities such as CO32-, Mg2+, Sr2+, Na+, etc. These characteristics can be easily obtained by synthesizing hydroxyapatite from natural sources, such as corals, starfishes, seashells, animal bones, bird eggshells etc. The natural sources used in the present work are three types of biogenic calcium carbonate, i.e. calcium carbonate that is produced by living organisms in the form of aragonite or calcite. Among the different sources, three biogenic calcium carbonates were chosen: cuttlefish (Sepia Officinalis) bones, mussel (Mytilus Galloprovincialis) shells and chicken eggshells. Besides their abundance and availability, they were selected because of their different composition: aragonite in cuttlebones, calcite in eggshells and a mixture of aragonite and calcite in mussel shells. After the first chapter, which is a theoretical introduction, this thesis is divided into other five chapters. Chapter 2 contains a careful characterization of the three biogenic raw materials while Chapter 3 deals with the synthesis of hydroxyapatite starting from these natural sources. The process developed here takes place entirely at nearly room temperature, which allows the organic part of the biological materials to be preserved. This synthesis process is basically a wet mechanosynthesis followed by a mild heat treatment (up to 150°C). The study focuses on the influence of several process parameters on the synthesis efficiency: temperature, milling time, pH and raw material. The temperature used to dry the slurry after the wet ball-milling was found to be the most important parameter, the higher the temperature the faster the conversion of CaCO3 into hydroxyapatite. Moreover, aragonite was found to transform more easily into hydroxyapatite with respect to calcite, and also to follow a different reaction path. The synthesis process described in Chapter 3 allowed to produce different bio-derived powders that were found to be non-stoichiometric, nanosized, carbonated hydroxyapatites, containing also additional ions, especially Mg2+ in the eggshell-derived material and Sr2+ in the cuttlebone-derived one. These powders were then used as a starting point for the studies presented in the next three chapters. Chapter 4 shows a very preliminary evaluation of the interaction with human cells in vitro. First, the as-synthesized powders were consolidated by uniaxial pressing and sintering at temperatures between 900°C and 1100°C and their crystallographic composition was analyzed. Then, after having established the non-cytotoxicity of the sintered pellets, osteoblasts from human osteosarcoma cell line were seeded on the pellets and their behavior after 1, 3 and 5 days of culture was observed by confocal microscopy. In general, all materials promoted good cell adhesion and proliferation, especially the eggshell-derived one. At this point, the bio-derived materials were found to induce a good cellular response but, in order to foster the regeneration of bones, a scaffold must also contain a large amount of interconnected porosity. Among the numerous methods to fabricate porous structures, additive manufacturing is surely very attractive due many advantages, such as the possibility of customizing the shape based on tomography images from the patients, the fact that no mold is needed and the freedom of fully designing the porosity. Indeed, not only the size and the amount of porosity are important, but also the shape of the pores and their position and orientation have a deep effect on the interaction with the cells. Therefore, Chapter 5 and Chapter 6 deal with the fabrication of scaffolds by 3D printing, following two different approaches. In the study presented in Chapter 5, the powders synthesized from cuttlebones, mussel shells and eggshells were used in combination with a thermoplastic polymer (PCL, polycaprolactone) to obtain bioactive composites. Composite materials made of 85 wt% PCL and 15 wt% bio-derived hydroxyapatite were used to fabricate porous scaffolds by extrusion 3D printing. The biological in vitro tests showed that the composite scaffolds possess better bioactivity than the pure PCL ones, especially those containing mussel shell- and cuttlebone-derived powders, which promoted the best cell adhesion, proliferation and metabolic activity of human osteosarcoma cells after 7 days of culture. In addition, the elastic compressive modulus, which was found to be between 177-316 MPa, thus in the range of that of trabecular bone, was found to increase of about ∼50% with the addition of the bio-derived nanopowders. Finally, in Chapter 6, the cuttlebone-derived powder was used to fabricate porous bioceramic scaffolds by binder jetting 3D printing. Due to serious technical issues related to the printing of a nanosized powder, 10 wt% of bio-derived powder was mixed with a glass-ceramic powder with bigger particle size. Moreover, the organic part of the cuttlebone had to be previously eliminated by a heat treatment at 800°C. Thanks to the great freedom of design that is allowed by the binder jetting process, scaffolds with two different pore geometries were fabricated: with pores of uniform size and with a size-gradient. Indeed, natural bone possesses a gradient in porosity from the core to the surface, from porous trabecular bone to dense cortical bone. The sintered scaffolds showed a total porosity of ∼60% for the pure glass-ceramic and ∼70% for the glass-ceramic with 10 wt% of cuttlebone-derived nanoparticles, which most probably slowed down the densification by limiting the contact between the glassy particles. All the bioceramic scaffolds promoted good adhesion and proliferation of human bone marrow-derived mesenchymal stem cells in vitro, without any significant difference between the different samples. However, the scaffolds with the cuttlebone-derived powder and with gradient porosity showed the greatest decrease of metabolic activity after 10 days of culture, which could be accounted as a sign of differentiation of stem cells.

Additive manufacturing (AM) has experienced significant growth and development in recent years, owing to the ability to produce complex parts using a wide range of materials with relative ease. Powder bed-based metal AM has been at the forefront of this growth, even reaching the point where parts can be manufactured for end-use applications. Binder jetting (BJ) is one such technique where a liquid binder is selectively deposited on powder layers to create a green body which is then densified using sintering. The aim of this work was to use binder jetting to produce parts using Vanadis 4 Extra, a highly alloyed cold-work tool steel produced by Uddeholm AB for applications involving high demand on abrasive wear. Optimization of the densification parameters, which included debinding atmosphere, debinding temperature, sintering atmosphere, sintering temperature, and sintering time, to achieve full density parts was carried out as the first phase. It was found that the sintering atmosphere and time had the most significant impact on the density of the samples while the debinding atmosphere heavily impacted the C residue from the binder. In the second phase, samples were produced using the optimized parameters for mechanical analysis, which included analyses of the surface roughness and the wear resistance of the binder jetted samples against the conventionally produced samples. The surface roughness was in line with the data presented in literature for binder jetted samples. The binder jetted samples produced during this work exhibited better wear resistance than the conventionally produced samples, with the samples post-processed using hot isostatic pressing showing even better wear resistance. One possible explanation is the diffusion of N from the sintering atmosphere into the samples, leading to the conversion of carbides to carbonitrides and even nitrides. However, further investigation is needed in order to confirm this theory.

This study aims to introduce a new qualification approach designed to enhance the overall integrity of complex cooling structures in gas turbine blades produced through 3D printing, with a focus on achieving maximum density. The primary objective is to present a comprehensive qualification and validation methodology tailored for components manufactured via binder jetting printing and non-selective laser melting (SLM) powder-based atomic diffusion additive manufacturing. This innovative qualification approach undergoes validation through stages encompassing design, printing, comprehension of thermal debinding and sintering processes, post-processing, optimization, and characterization, all aimed at achieving complex cooling structures with optimal density using stainless steel material and In718 as a case study. Subsequently, the material properties obtained are compared with those of IN718 produced via laser-based manufacturing. Thorough characterization is conducted before and after sintering to assess the impact of sintering on density enhancement. Experimental optimization employing the Taguchi matrix with an L9 orthogonal array involves the selection of three key parameters: sintering time, sintering temperature, and heat treatment. The procedural framework established in this research applies to high-temperature applications wherein components are fabricated using atomic diffusion additive manufacturing or binder jetting printing techniques. Testing and inspection procedures involve neutron scattering, radiography, and CT scanning methods, with a specific emphasis on neutron scattering measurements conducted under externally heated and internally cooled conditions to evaluate residual strains within the gas turbine environment. Understanding the interplay between residual stresses originating from manufacturing processes and thermal stresses provides valuable insights into the impact of additive manufacturing on component performance in thermal environments, thus contributing to the advancement of the proposed study.

Biogenic structures can impart important information regarding animal behaviors and depositional conditions at the time of colonization including: sedimentation rate, current velocities, distribution of food resources, oxygenation, salinity, and temperature. This thesis utilizes various ichnological subdisciplines to build upon these underlying ichnological principles. Neoichnology is a newly emerging field that can provide invaluable information about modern and ancient organisms. Burrowing activities of a population of deposit-feeding, freshwater Limnodrilus and Tubifex is found to produce biogenic graded bedding. Similarly, the burrowing activities of Euzonus mucronata are studied in relation to the trace fossil Macaronichnus segregatis, which displays mineralogical segregation between the burrow infill and mantle. The process of grain partitioning was assessed using videographic analyses of ingested and excreted grains by these deposit-feeding polychaetes, which selectively ingest felsic grains through en-masse feeding in felsic-rich locales. Macaronichnus is an important trace in ancient deposits of nearshore settings; however, since its inception, the genus had not been formally diagnosed. Accordingly, a unique approach to classification of these traces was undertaken, using grain sorting and collective morphology as ichnotaxobases, in addition to the diagnosis of a new, related genusHarenaparietis. In the Permian Snapper Point Formation of SE Australia, a new ichnospecies of Piscichnus was diagnosed and interpreted to reflect fish or cephalopod feeding via hydraulic jetting into the substrate in search of infaunal food sources. The delineation of trace fossils through ichnotaxonomy provides a basis for identifying trace fossil suites, which can be interpreted through ichnofacies analysis. Subtle ichnological and sedimentological attributes of deltaic strata in the Viking Formation permits the identification of wave-influenced and mixed river- and wave-influenced deposits in the Hamilton Lake and Wayne-Rosedale-Chain areas of Alberta, Canada, respectively. Facies analysis combined with the identification of palimpsest stratigraphic surfaces led to the identification of transgressively incised shoreface deposits at Hamilton Lake. Examples of palimpsest ichnofossils from the Hamilton Lake area and from other strata are used in an assessment of soft-, stiff- and firmground suites. This study revealed the importance of substrate properties, environment, stratigraphy and processes leading to the formation and expression of allocyclic and autocyclic surfaces.

No description available.

This dissertation presents the novel creation of a hybrid D-fiber electro-optic polymer electric field sensor. The sensor is made by removing a portion of the cladding from a D-shaped optical fiber, thus exposing the core to interaction with external stimulus. Then, an electro-optic polymer is deposited, partially replacing the core of the fiber. Next, the polymer is poled to endow it with electro-optic properties. This sensor is packaged in order to restore its mechanical strength. Because D-fiber is not intrinsically compatible with standard optical equipment it is fusion spliced to standard polarization maintaining fiber. Finally the sensor is tested for electro-optic sensitivity. The hybrid D-fiber electric field sensors designed and fabricated in this work meet the requirements of mechanical strength, temporal stability, minimal perturbation of the electric field by the sensor, and a small and flexible cross-sectional area so that it can be embedded into the device under test. A fully packaged hybrid electro-optic polymer D-fiber electric field sensor which is capable of detecting electric fields of 50 V/m at a frequency of 6 GHz is produced. The sensor's electro-optic response is shown to be temporally stable. Additionally, the sensor is physically robust, and physically and electrically non-intrusive. This work also adds a thorough understanding of the design and fabrication of D-fiber waveguides with a polymer material deposited in the core. Several new fabrication techniques are developed and presented. A path to greater electric field sensitivity is outlined for future research.

<p>The development of reliable, robust and low-cost sensor devices is growing in importance and an ongoing challenge. From environmental monitoring and household safety to food and biopharmaceutical industries, the necessity for specific analyte detection is crucial. Over the years researchers have come up with myriad materials that can be used for efficient sensing devices. The materials employed are governed by application and performance criteria as well as the sensing mechanism, which might be based on physical or chemical principles. In this thesis, two different types of electrochemical sensor technologies were examined with special attention paid to the application of the devices, the materials used, and their feasibility for scalable manufacturing.</p> <p>In the first study, binary mixtures of conducting and semiconducting nanomaterials were explored as promising candidates for the manufacturing of low-cost ethylene sensor on flexible substrates. Ethylene (C2H4) is a small plant hormone which has been shown to affect the growth and senescence of flowers, leaves and fruits. Currently available devices have demonstrated high ethylene sensitivities with great potential for technology size reduction; however, some are not practical for use outside of the laboratory, lack portability, or require more research to demonstrate their reproducibility and stability in different environments, as well as selectivity to C2H4 in large-scale applications. Conductometric gas sensors based on a combination of carbon nanotubes (CNTs) and exfoliated molybdenum disulfide (MoS2) coated with molecular receptors is demonstrated for the selective detection of ethylene, including details on materials preparation, manufacturing, and characterization. Mixtures of CNTs and exfoliated MoS2 were deposited onto screen-printed interdigitated electrodes on plastic substrates, with optimization for scalable and continuous manufacturing by roll-to-roll methods. C2H4 detection levels of 0.1 ppm were readily achieved with responses on the second timescale.</p> <p>The second sensor technology shows how thin-film potentiometric electrodes based on ion-selective membranes can be designed to tolerate sterilizing radiation while providing excellent performance and signal stability. This sensor's development was motivated by the expanding need for single-use bioreactor systems in the biopharmaceutical industry, which require strict control over cell culture conditions for several weeks or more. Until recently, critical analysis has been conducted mostly by offline or “at-line” sampling of aliquots withdrawn from the sterile bioreactor. The latter is inefficient and can increase the risk of contamination. Inspired by the challenges related to cost, integration and performance following irradiation a potentiometric pH electrode was developed, intended for single-use applications. It was shown to be radiation-tolerant while providing reliable data comparable to a commercial pH meter over a period of three months. The electrodes exhibited quasi-linear signal drifts of +0.28 mV/day or 0.005 pH units/day. Thin-film γ-irradiated electrodes could provide accurate pH readings in sterilized culture media using a single-point calibration, within 0.07 pH units of a commercial meter with glass electrode and daily calibration. Furthermore, to advance the development of market-ready sensors past the conceptual stage, a few automated processes for scalable membrane deposition were investigated.</p>