Trenncharakteristik eines Abweiseradsichters

Abweiseradsichter dienen zur Trennung von Partikelkollektiven in ein Grobgut und ein Feingut mit Trenngrenzen im niedrigen Mikrometerbereich. Im verwendeten Sichtertyp strömt die Sichtluft in einem Wirbel aufwärts zum Sichtrad, das aus mehreren Schaufeln besteht. Das Aufgabegut wird unterhalb des Sichtrades zugegeben und durch den Luftwirbel zum Sichtrad getragen. Dort werden die Partikel in einem Kräftegleichgewicht aus einwärts gerichteter Schleppkraft der Luft und auswärts gerichteter Zentrifugalkraft nach ihrem aerodynanischen Eigenschaften getrennt. Das Feingut passiert den Zwischenraum zwischen den Schaufeln des Sichtrades und gelangt in die Feingutleitung, wo es schließlich in einem Zyklon aus dem Luftstrom abgetrennt wird. Das Grobgut, das aufgrund der dominierenden Zentrifugalkraft am Sichtrad abgewiesen wird, gelangt zurück in den Sichtraum und baut einen hochturbulenten Pulverspeicher auf, den so genannten Hold-up. Das Abfließen aus dem Hold-up kann nur über den Transport in den Grobgutbehälter erfolgen, wozu die aufwärts gerichtete Sichtluftstrom durchquert werden muss. Dies gelingt erst bei hinreichend hoher Massenbeladung im Hold-up durch die Bildung von Partikelsträhnen. Das Ziel dieser Arbeit ist es, ein besseres Verständnis für die Vorgänge in Abweiseradsichtern zu gewinnen bzw. das Trennverhalten zu erklären. In einer Sensitivitätsanalyse wurde zunächst der Einfluss verschiedener Materialparameter sowie konstruktiver Änderungen am Sichter durchgeführt. Auf dieser Basis konnte der Sichtprozess in vier Unteraspekte aufgeteilt werden: (1.) die Dispergierung des Aufgabegutes, (2.) der Transport des Aufgabegutes zum Sichtrad, (3.) die eigentliche Trennung im Sichtradschaufelzwischenraum und (4.) der Abtransport des Grobgutes. Die langen Zeiträume, die der modifizierte ATP 50 Abweiseradsichter benötigt, um den stationären Zustand zu erreichen, konnte auf den sich bildenden Hold-up zurückgeführt werden. Ein entwickeltes Modell zur Partikelverweilzeit und der zeitabhängigen Hold-up Masse spiegelt die experimentell bestimmten Verweilzeiten gut wider. Anschließend folgten Experimente mit geringer Massenbeladung, so dass PIV (Particle Image Velocimetry), LDA (Laser Doppler Anemometrie) und Hochgeschwindigkeitskameraaufnahmen durchgeführt werden konnten. Diese zeigten die signifikanten Abweichungen zu üblicherweise angenommenen Fluidströmungsgeschwindigkeiten. Andererseits erfasste diese Messtechnik die Initialgeschwindigkeitsverteilungen des Sichtgutes beim Eintritt in den Sichtradschaufelzwischenraum. DEM (Discrete Element Method) Simulationen erfassten die Anzahl an Partikel-Partikel Kollisionen und ein theoretisches Modell wurde abgeleitet. Dieses hat das Ziel, die Partikel-Partikel Kollisionen im Sichtradschaufelzwischenraum so stark zu vereinfachen, dass sie nicht mittels eines Supercomputers und spezieller Software berechnet werden müssen, sondern mit einem normalen Computer und Matlab zu erfassen sind. Hier finden die Stoßeigenschaften, wie die Verteilung der Restitutionskoeffizienten oder die Verteilung von Rücksprung- und Impaktionswinkel, Anwendung. Mittels der Partikelinitialgeschwindigkeitsverteilung, der Partikel-Partikel-Kollisionshäufigkeit sowie der theoretischen Unterteilung in drei Unterfälle und den Stoßparameterverteilungen lässt sich eine Partikeltangentialgeschwindigkeits- und Radiusverteilung berechnen. Zusammen mit der realen Luftströmung, der Berücksichtigung der Partikelform und des spezifischen Widerstandsbeiwertes lässt sich eine kumulative Abweisewahrscheinlichkeit berechnen. Diese spiegelt die experimentell gemessenen Trennkurven für Kalksteinpartikel, gemahlenes Glas, Glaskugeln sowie zwei Leichtfüllstoffe gut wider.Deflector wheel classifiers are used to separate particle collectives in the low micrometer range according to size. The feed material is separated into two fractions, the coarse material and the fine material. The classifying air used for this purpose is drawn in through an eccentrically mounted inlet below the classifier wheel, forms an upward-flowing vortex and is drawn into the fines tube through the rapidly rotating classifier wheel. The feed material is added below the classifier wheel and carried by the air vortex to the classifier wheel, where the particles experience a force equilibrium of inward drag force of the air and outward centrifugal force. In the case of fines, the drag force of the air is greater than the centrifugal force, allowing the particles to enter the interior of the classifier wheel. A cyclone then separates the fine material from the air stream. In the case of coarse material on the other hand, the centrifugal force dominates and the particles are rejected back into the classifying compartment. The coarse material outlet is located below the air inlet and the coarse material must overcome a force equilibrium of gravity and drag force of the air. Only when a hold-up is formed and the mass loading is consequently sufficient, the rejected coarse material can overcome this force equilibrium by forming loose particle clusters and wake effects. The aim of this work is to gain a better understanding of the processes in deflector wheel classifiers, or rather to explain the separation behavior. In a sensitivity analysis, the influence of various material parameters as well as design changes to the classifier were carried out. On this basis, the classifying process could be divided into four sub-aspects: (1.) the dispersion of the feed material, (2.) the transport of the feed material to the classifier wheel, (3.) the true separation in the space between the classifier wheels, and (4.) the removal of the coarse material. The long times required for the modified ATP 50 deflector wheel classifier to reach steady state could be attributed to the forming hold-up. The accumulating particulate mass is proportional to the cut particle size at the coarse material outlet. A developed model for particle residence V time and time-dependent hold-up mass reflects the experimentally determined residence times very well. Subsequently, the focus is on experiments with low mass loading, so that optics-based measurement devices such as PIV (Particle Image Velocimetry), LDA (Laser Doppler Anemometry) and high-speed camera recordings were usable. These showed the significant deviation from commonly assumed fluid flow velocities and, for example, up to four times higher radial velocities near the trailing classifier blade than expected. On the other hand, this measurement technique captured the initial velocity distributions of the material to classify as it entered the classifier wheel interspace. DEM (Discrete Element Method) simulations captured the number of particle-particle collisions and a theoretical model was derived. This model aims to simplify the particle-particle collisions in the gap between the classifying wheels to such an extent that they must not be calculated by means of a supercomputer and special software, but by means of a normal computer and Matlab. Here, the impact characteristics, such as the distribution of the restitution coefficients or the rebound minus impaction angle distribution, are applied. The characteristic impact parameters had been measured in the classifier with moving wall for limestone and in a model setup with standing wall for the various materials. Using the particle initial velocity distribution, the particle-particle collision probability, and the theoretical subdivision into the three subcases as well as the impact parameter distributions, a particle tangential velocity and radius distribution can be calculated. Together with the actual airflow, the consideration of the particle shape and the shape and Reynolds number dependent drag coefficient, a cumulative rejection probability can be calculated. This reflects the experimentally measured separation curves for limestone particles, ground glass, glass spheres, and the lightweight fillers Aeropor and Sil-cell very well. For the purpose of scalability, the input parameters for the model are chosen so that they can either be measured quite well or be estimated

Forced triboelectrification of fine powders in particle wall collisions

Triboelectric separation as an inexpensive and environmentally friendly technique could contribute to material-specific sorting. However, the application as a widespread method is limited due to the complexity of the process. In particle wall collisions, various parameters like collision energy and angle, work function of the contact partners, humidity, surface roughness, etc. influence the particle charging in a hardly predictable way. This study investigates the possibilities of forced triboelectric particle charging by applying an electrical potential to the metal contact partner (copper/steel pipe). The variations included different pipe lengths (0.5 m–3 m), particle materials, and particle sizes for limestone. A distinction is made between the net charge of the particles and the positive, negative, and neutral mass fractions. The work functions of the investigated materials vary from about 3.2 eV to >8.5 eV for glass, limestone, artificial slag, and lithium aluminate particles. With the applied high-voltage potential, the particle net charge can be shifted linearly. For limestone, it is shown that the neutral fraction is highest at the Point of Zero Net Charge (PZNC). This observation may identify an approach for the material selective separation of one target component from a multi-material mixture

Development of a model for the separation characteristics of a deflector wheel classifier including particle collision and rebound behavior

Deflector wheel classifiers are widespread in industry for the separation of powders into fine and coarse powders. Even though this separation process has been known for quite some time, it is not yet fully understood, and existing models fail to precisely predict the separation characteristics. Due to the high throughput of deflector wheel classifiers, it is greatly beneficial to estimate the separation characteristics before the experiment. Here, the developed model critically examines the usual assumptions, such as ideal airflow, neglection of particle–wall and particle–particle interactions, or spherically-shaped particles. First, the investigation of the air flow using a Particle Image Velocimetry (PIV) system showed significant differences to the assumed ideal flow field, then particle sphericity and its influence on the interaction between the particles and the paddles of the deflector wheel was investigated and compared with particle rebound behavior on a static wall. Surprisingly, comminuted glass behaves similarly to comminuted limestone in multiple aspects and not like glass beads. To determine the number of particle–particle collisions, Discrete Element Method (DEM) simulations were performed. The aforementioned aspects found application in the model and the separation behavior was well-estimated

Development of a Model for the Separation Characteristics of a Deflector Wheel Classifier Including Particle Collision and Rebound Behavior

Deflector wheel classifiers are widespread in industry for the separation of powders into fine and coarse powders. Even though this separation process has been known for quite some time, it is not yet fully understood, and existing models fail to precisely predict the separation characteristics. Due to the high throughput of deflector wheel classifiers, it is greatly beneficial to estimate the separation characteristics before the experiment. Here, the developed model critically examines the usual assumptions, such as ideal airflow, neglection of particle–wall and particle–particle interactions, or spherically-shaped particles. First, the investigation of the air flow using a Particle Image Velocimetry (PIV) system showed significant differences to the assumed ideal flow field, then particle sphericity and its influence on the interaction between the particles and the paddles of the deflector wheel was investigated and compared with particle rebound behavior on a static wall. Surprisingly, comminuted glass behaves similarly to comminuted limestone in multiple aspects and not like glass beads. To determine the number of particle–particle collisions, Discrete Element Method (DEM) simulations were performed. The aforementioned aspects found application in the model and the separation behavior was well-estimated.DFG, 313858373, SPP 2045: Hochspezifische mehrdimensionale Fraktionierung von technischen Feinstpartikelsysteme

Quantitative first principles calculations of protein circular dichroism in the near-ultraviolet

Vibrational structure in the near-UV circular dichroism (CD) spectra of proteins is an important source of information on protein conformation and can be exploited to study structure and folding. A fully quantitative theory of the relationship between protein conformation and optical spectroscopy would facilitate deeper interpretation and insights into biophysical and simulation studies of protein dynamics and folding. We have developed new models of the aromatic side chain chromophores toluene, p-cresol and 3-methylindole, which incorporate ab initio calculations of the Franck-Condon effect into first principles calculations of CD using an exciton approach. The near-UV CD spectra of 40 proteins are calculated with the new parameter set and the correlation between the computed and the experimental intensity from 270 to 290 nm is much improved. The contribution of individual chromophores to the CD spectra has been calculated for several mutants and in many cases helps rationalize changes in their experimental spectra. Considering conformational flexibility by using families of NMR structures leads to further improvements for some proteins and illustrates an informative level of sensitivity to side chain conformation. In several cases, the near-UV CD calculations can distinguish the native protein structure from a set of computer-generated misfolded decoy structures

The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory. Athena is a versatile observatory designed to address the Hot and Energetic Universe science theme, as selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), X-IFU aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over a hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR (i.e. in the course of its preliminary definition phase, so-called B1), browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters, such as the instrument efficiency, spectral resolution, energy scale knowledge, count rate capability, non X-ray background and target of opportunity efficiency. Finally, we briefly discuss the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, touch on communication and outreach activities, the consortium organisation and the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. The X-IFU will be provided by an international consortium led by France, The Netherlands and Italy, with ESA member state contributions from Belgium, Czech Republic, Finland, Germany, Poland, Spain, Switzerland, with additional contributions from the United States and Japan.The French contribution to X-IFU is funded by CNES, CNRS and CEA. This work has been also supported by ASI (Italian Space Agency) through the Contract 2019-27-HH.0, and by the ESA (European Space Agency) Core Technology Program (CTP) Contract No. 4000114932/15/NL/BW and the AREMBES - ESA CTP No.4000116655/16/NL/BW. This publication is part of grant RTI2018-096686-B-C21 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. This publication is part of grant RTI2018-096686-B-C21 and PID2020-115325GB-C31 funded by MCIN/AEI/10.13039/501100011033

The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer, studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory, a versatile observatory designed to address the Hot and Energetic Universe science theme, selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), it aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over an hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR, browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters. Finally we briefly discuss on the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, and touch on communication and outreach activities, the consortium organisation, and finally on the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. (abridged).Comment: 48 pages, 29 figures, Accepted for publication in Experimental Astronomy with minor editin

Formulation, stabilisation and encapsulation of bacteriophage for phage therapy

Against a backdrop of global antibiotic resistance and increasing awareness of the importance of the human microbiota, there has been resurgent interest in the potential use of bacteriophages for therapeutic purposes, known as phage therapy. A number of phage therapy phase I and II clinical trials have concluded, and shown phages don’t present significant adverse safety concerns. These clinical trials used simple phage suspensions without any formulation and phage stability was of secondary concern. Phages have a limited stability in solution, and undergo a significant drop in phage titre during processing and storage which is unacceptable if phages are to become regulated pharmaceuticals, where stable dosage and well defined pharmacokinetics and pharmacodynamics are de rigueur. Animal studies have shown that the efficacy of phage therapy outcomes depend on the phage concentration (i.e. the dose) delivered at the site of infection, and their ability to target and kill bacteria, arresting bacterial growth and clearing the infection. In addition, in vitro and animal studies have shown the importance of using phage cocktails rather than single phage preparations to achieve better therapy outcomes. The in vivo reduction of phage concentration due to interactions with host antibodies or other clearance mechanisms may necessitate repeated dosing of phages, or sustained release approaches. Modelling of phage-bacterium population dynamics reinforces these points. Surprisingly little attention has been devoted to the effect of formulation on phage therapy outcomes, given the need for phage cocktails, where each phage within a cocktail may require significantly different formulation to retain a high enough infective dose. This review firstly looks at the clinical needs and challenges (informed through a review of key animal studies evaluating phage therapy) associated with treatment of acute and chronic infections and the drivers for phage encapsulation. An important driver for formulation and encapsulation is shelf life and storage of phage to ensure reproducible dosages. Other drivers include formulation of phage for encapsulation in micro- and nanoparticles for effective delivery, encapsulation in stimuli responsive systems for triggered controlled or sustained release at the targeted site of infection. Encapsulation of phage (e.g. in liposomes) may also be used to increase the circulation time of phage for treating systemic infections, for prophylactic treatment or to treat intracellular infections. We then proceed to document approaches used in the published literature on the formulation and stabilisation of phage for storage and encapsulation of bacteriophage in micro- and nanostructured materials using freeze drying (lyophilization), spray drying, in emulsions e.g. ointments, polymeric microparticles, nanoparticles and liposomes. As phage therapy moves forward towards Phase III clinical trials, the review concludes by looking at promising new approaches for micro- and nanoencapsulation of phages and how these may address gaps in the field

The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

Instrumentatio