@phdthesis{Luebbert2011, author = {L{\"u}bbert, Christian}, title = {Zur Charakterisierung des gequenchten Zustandes im Elektroabscheider}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-23726}, school = {BTU Cottbus - Senftenberg}, year = {2011}, abstract = {Unter Korona-Quenching versteht man die Verringerung der Stromaufnahme eines Elektroabscheiders unter dem Einfluss teilchengebundener Raumladung. Die theoretische Untersuchung dieses Betriebszustandes im Rohr-Draht-Elektroabscheider und die experimentelle Validierung der Vorhersagen sind Inhalt der Arbeit. Theoretisch wird das Korona-Quenching anhand unterschiedlich komplexer Modelle untersucht, die auf der Bilanzierung der teilchengetragenen Raumladung beruhen. Es zeigt sich dabei, dass der Elektroabscheider eine geometrieabh{\"a}ngige maximale Abscheiderate besitzt, die im gequenchten Zustand erreicht wird. Wegen der geringen Stromaufnahme erfolgt die Abscheidung hier besonders energieeffizient. Die vorgestellten Berechnungsmethoden erlauben eine Optimierung von Elektroabscheidern f{\"u}r hohe Teilchenkonzentrationen. Der Vergleich mit experimentellen Ergebnissen zeigt eine sehr gute {\"U}bereinstimmung mit den theoretischen Vorhersagen im jeweils beanspruchten G{\"u}ltigkeitsbereich.}, subject = {Abscheider; Quenching; Elektroabscheider; Korona-Quenching; Raumladung; Ionenausbeute; Aerosol; Electrostatic precipitator; Corona-Quenching; Space charge; Ion yield; Aerosol}, language = {de} } @inproceedings{RiebelAleksinVora2016, author = {Riebel, Ulrich and Aleksin, Yury and Vora, Alpesh Laxman}, title = {Non-ohmic properties of highly resistive dust layers - experimental studies and numerical modelling under OpenFOAM®}, editor = {Riebel, Ulrich}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-41823}, year = {2016}, abstract = {Vortrag "ICESP XIV. International Conference on Electrostatic Precipitation 2016", Wroclaw, Polen, 19.-23.09.2016 Back corona and dust resistivity are well known topics in electrostatic precipitation. Back corona results from high dust resistivity and occurs when the field strength in the dust layer surpasses a critical value E crit, which is typically found to be in the order of 15 to 30 kV/cm. Besides the resistivity ρ, the current density is the main parameter: E = i ρ < E crit. Hence, possible actions against back corona include a reduction of ρ by dust conditioning, or a reduction of i, for example by pulsed corona operation. Much work has been devoted to study the dependence of ρ on dust composition, temperature, humidity, adsorption layers and dust layer porosity, and a variety of different set-ups for dust resistivity measurements has been proposed. Even though some authors report a dependence of ρ on current density or field strength resp., dust resistivity is mostly seen as a material property. However, in measurements on product dusts in the upper resistivity range, we found that dusts show extremely non-ohmic properties: Most strikingly, resistivity may vary by several orders of magnitude with time. Also, the experimental arrangement can change the resistivity results by orders of magnitude: When resistivity is measured with the dust layer exposed to a corona discharge (imitating the situation in a real ESP), ρ depends strongly on the layer thickness. Meanwhile the same dust does not show the strong layer thickness dependence when electrodes are placed on both sides of the dust layer, and also time effects are much less prominent. Additional findings include that dusts that have been exposed to resistivity measurements show a high level of electrostatic charging afterwards. An interpretation of these results may be found from the theory of semiconductors and electret materials. Accordingly, highly resistive dust layers do not contain mobile electrons. Current transport occurs only after charge carriers (free electrons or holes) have been injected from the electrodes or from a gas discharge adjacent to the surface. When the injection process is non-symmetric (e.g. with corona discharge), the current transport through the dust layer can be dominated by charge carriers of one polarity, depending on the polarity of the corona. Some of the effects observed in experiment, namely the layer thickness effect and the current density influence, can indeed be ascribed to unipolar injection and space charge limited conduction. The time effects can mainly be ascribed to the "deep trapping" of the charge carriers, leading to a high level of immobile space charge. As overall space charge is limited, this reduces the level of mobile space charge available for current transport. The space charge also leads to a deformation of the electric field inside the dust layer, and hence influences injection via the Schottky (thermionic field emission) mechanism. By integrating the mechanisms of charge transport in dielectrics (injection, drift, immobilization, recombination) into the OpenFOAM® simulation package, rather realistic simulations of time-dependent resistivity are possible. The simulations also are helpful to identify the mechanisms responsible for certain types of resistivity behavior.}, subject = {ESP; Elektroentstaubung; Back Corona; Dust Resistivity; Dust Resistivity Measurement}, language = {en} } @phdthesis{Perwin2015, author = {Perwin, J{\"o}rg}, title = {Entwicklung einer optischen Messtechnik zur Erfassung der Kinetik schneller Partikelbildungsprozesse}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-36008}, school = {BTU Cottbus - Senftenberg}, year = {2015}, abstract = {Bei einer Reihe von Anwendungsf{\"a}llen ist es w{\"u}nschenswert Partikelbildungs­prozesse im Nanometerbereich in-situ z. B. in str{\"o}menden Medien oder mit sehr hoher zeitlicher Aufl{\"o}sung zu beobachten. Mit etablierten Verfahren, z. B. der dynamischen Lichtstreuung ist dies in der Regel nicht m{\"o}glich. Das hier dargestellte neue Verfahren basiert auf einer Kombination von optischen Extinktions- und Streulichtmessungen. Im Rayleigh-Bereich kann damit aus jeder Einzelmessung ein mittlerer Partikeldurchmesser und die Anzahlkonzentration bestimmt werden. F{\"u}r die Extinktionsmessungen ergeben sich zwei Arbeitsbereiche, einer mit hoher Transmission und einer mit hoher Extinktion. Diese beiden Bereiche stellen deutlich unterschiedliche Anforderungen an die Messtechnik. Das entwickelte Messger{\"a}t verf{\"u}gt deshalb {\"u}ber zwei unterschiedliche Messverfahren. Der Bereich hoher Extinktion wird mit einem heterodyn interferometrischen Verfahren abgedeckt, der Bereich hoher Transmission mit einem nicht interferometrischen Differentialverfahren. Die Arbeit stellt das grundlegende Modell vor. Außerdem werden notwendige Korrekturen, unter anderem f{\"u}r einsetzende Mehrfachstreuung, beschrieben. Die technische Umsetzung wird dargestellt. Abschließend werden Kalibriermethoden diskutiert und die Evaluation des Verfahrens beschrieben.}, subject = {Partikelmesstechnik; Extinktion; Streulicht; Heterodyne Interferometrie; Nanopartikel; Particle size analysis; Extinction; Scattered light; Heterodyn interferometry; Nanoparticles; Nanopartikel; Interferenz ; Interferometrie; Extinktion; Streulicht; Teilchenmesstechnik}, language = {de} } @phdthesis{Bacher2022, author = {Bacher, Christian}, title = {On the influence of electrohydrodynamically induced turbulence on momentum, heat and mass transport in electrostatic precipitators}, doi = {10.26127/BTUOpen-5994}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-59948}, school = {BTU Cottbus - Senftenberg}, year = {2022}, abstract = {Electrostatic precipitators (ESPs) belong to the most efficient devices for control of particle emissions in the process industry and environmental technologies in general. The operating principle of ESPs, relying on particle precipitation by electrical charging, leads to an enhanced turbulent motion by electrohydrodynamic (EHD) effects within the gaseous working fluid passing through the ESP. This enhanced turbulence is generally considered detrimental to the separation efficiency, because the additional shear forces acting on the collection electrodes promote re-entrainment of already precipitated particles. Further, the enhanced turbulent cross mixing diminishes the transport of charged particles by electric forces directed towards the collection electrodes. In other industrial applications however, many process units that are based on heat or mass transport would benefit from enhanced turbulent mixing. These include heat exchangers for energy recuperation or evaporation and absorption units such as flue gas scrubbers. A combination of these with an ESP possibly allows for versatile new applications in the process industry. The motivation of this thesis is to study the effects of electrohydrodynamically generated motions onto the turbulent cross mixing within gaseous flows over a wide parameter space including variations in geometry and operating conditions. In order to do so, the influence of EHD effects on the three major transport properties, i.e. thermal energy, mass and momentum, were experimentally investigated. Based on analogies caused by similar transport mechanisms, the experimental results were compared despite different methods being used. In order to help with the comparison a simplified eddy viscosity model is applied. The study for each transport property was conducted with a different setup of a tube type ESP. These setups include axial and radial pressure drop measurements to quantify the momentum transport, a self-built local heat transfer sensor to determine heat transfer coefficients and a wetted wall-column to study the enhancement of mass transport phenomena. Experiments on momentum and heat transport include a large variation of different geometries and operating variables such as discharge electrode design, tube diameter, flow velocity, as well as magnitude and polarity of operating voltage. In addition, selected measurements with aerosol particles were conducted, to gain additional insights on the effects of EHD induced turbulence generation by particle bound space charge compared to ion bound space charge in clean gas flows. The results do not only provide transport coefficients for the hands-on application by plant designers, but also feature numerous experimental data that can be used as reference values for ongoing research in the numerical simulation of electrohydrodynamically enhanced flow and therefore significantly increase the available amount of data provided by current literature.}, subject = {Electrohydrodynamics; Electrostatic precipitation; Heat and mass transfer intensification; Elektrohydrodynamik; Elektroabscheider; Verbesserung des W{\"a}rme- und Stofftransports; Elektrofilter; Elektrohydrodynamik; Numerische Str{\"o}mungssimulation}, language = {en} } @phdthesis{MoralesHenriquez2009, author = {Morales Henr{\´i}quez, Carlos Javier}, title = {W/O Emulsions : formulation, characterization and destabilization}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-6068}, school = {BTU Cottbus - Senftenberg}, year = {2009}, abstract = {This work refers to water in oil emulsion formulation, characterization and destabilization. These topics were studied in order to generate knowledge that could be used as a base for the treatment of highly stable W/O emulsions. Two types of emulsions were studied: synthetics and naturals; the last ones come from the crude oil production process of different Venezuelan regions. In this book, chapters 1 and 2 give an introduction to the research area and the theoretical background related with it, respectively. In chapter 3, the effect of surfactant content, water content, HLB value, alcohol content, salinity, emulsion volume, and mixing properties on water in paraffin emulsion stability was studied. Emulsion stability was determined by the amount of water and oil separated after 30 days. After finishing the variables scans, the most appropriate formulation conditions were established, and a formulation protocol was defined. Emulsion density and apparent viscosity were measured, and viscosity was modeled by the Power Law considering both shear rate and water content. Chapter 4 deals with emulsion characterization. Although some particle sizing devices have gained a lot of popularity, none of them is able to distinguish between drops and solids, and few are able to handle viscous oily samples. In this chapter the use of optical microscopy, enhanced by the use of digital video capabilities and image analysis software, to characterize oil production wastes is discussed. Several thousands of particles were counted and their projected areas were measured. A discussion is given about the different corrections required in order to extract the most reliable information from the image, overcoming some of the drawbacks of this kind of measurements. A new technique the so-called cross-linked method was developed to offer unique features like the determination of the fraction of droplets that exist in the form of non-coalesced agglomerates. When cross-linked with the results obtained by standard ASTM procedures, it is calculated the amount of disperse phase that exists in the form of submicron droplets or large free water drops that are usually not sampled for microscope slides. Chapters 5 and 6 deal with emulsion destabilization. In chapter 5, a variety of materials were used to investigate their applicability as so-called collector materials, to improve the destabilization and separation of water in oil emulsions stabilized by a non-ionic surfactant. The emulsion destabilization degree was determined by the amount of water and oil separated after centrifugation. The recovery of both phases was strongly dependent on the nature of the material, material/emulsion ratio, particle size, and contact time. By varying conditions, it was possible to increase the water separation from 0 (without material) up to 95\%. In chapter 6, the effect of a DC electric field on W/O emulsions was evaluated. Electric field magnitude, water content, cell size, electrode design, and electrode coating were considered. Emulsion destabilization was improved by combining electric field, collector material and centrifugation. A comparison is given about the emulsion characteristics in terms of microscopy between both, synthetic and crude oil emulsions.}, subject = {Wasser-in-{\"O}l-Emulsion; W/O Emulsionen; Emulsionsformulierung; Emulsionscharakterisierung; Emulsionsdestabilisierung; Kollektormaterial; W/O Emulsions; Emulsion formulation; Emulsion characterization; Emulsion destabilization; Collector material}, language = {en} } @phdthesis{Wang2009, author = {Wang, Shaoliang}, title = {Partikelgr{\"o}ßenbestimmung mittels eines Laser-Optischen Partikelz{\"a}hlers mit zwei Empfangswinkelbereichen}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-14472}, school = {BTU Cottbus - Senftenberg}, year = {2009}, abstract = {Zur Bestimmung deren Gr{\"o}ße und Konzentration der Aerosolpartikeln z{\"a}hlt der optische Partikelz{\"a}hler (OPZ). Einzelne Teilchen passieren ein intensiv beleuchtetes Messvolumen. Das von den Teilchen gestreute Licht wird mittels eines aus Linsen und Blenden bestehenden Systems auf einen photoelektrischen Sensor fokussiert und dabei als Streulicht-Impuls empfangen, wobei die Impuls-H{\"o}he in die Teilchengr{\"o}ße (durch Mie-Theorie) umgerechnet wird. Je nach der Lichtquelle teilen sich die OPZ in zwei Gruppen ein: OPZ mit Weißlicht und mit Laserlicht. Als Lichtquelle bietet der Laser eine Reihe Vorteile. Aber der Laser als Lichtquelle hat auch Nachteil: der konventionelle Laserlicht-Partikelz{\"a}hler liefert, anders als Weißlicht, normalerweise keinen eindeutigen Zusammenhang zwischen Streulichtintensit{\"a}t und Partikelgr{\"o}ße, insbesondere beim Partikelgr{\"o}ßenbereich um 1 um. Auf Basis von dem Stand der OPZ-Technik wird im Rahmen der vorliegenden Arbeit eine neue Messeinrichtung: Laserlicht-Partikelz{\"a}hler mit zwei unterschiedenen Empfangswinkelbereichen zur Ermittlung der Partikelgr{\"o}ßen gebaut und systematisch untersucht (z.B. Koinzidenzfehler, Randzonenfehler und Totzeit). Eine Laserdiode ist als Lichtquelle eingesetzt. Innerhalb des Laserstrahls ist ein Messvolumen durch die zwei Empfangssysteme rein optisch abgegrenzt. Aus dieser Messeinrichtung ergeben sich zwei Kalibrierkurven, die den Zusammenhang von Partikelgr{\"o}ße und Impulsh{\"o}he beschreiben k{\"o}nnen. Das heißt, f{\"u}r jede Partikel, die durch das Messvolumen passiert, werden zwei Signale gemessen. Zur Bestimmung von deren Gr{\"o}ße kann jede Kombinationsm{\"o}glichkeit der beiden Impulsh{\"o}hen bzw. Kalibrierkurven (speziell durch Matrix-Methode) theoretisch genutzt werden. Die Versuchsergebnisse zeigten, dass dieses neue Verfahren f{\"u}r die Ermittelung der Partikelgr{\"o}ßen aus mehrdeutigen Kurven, besonders beim Einsatz f{\"u}r unterschiedliche Stoffsysteme bzw. einem breiten Brechungsindexbereich geeignet ist. Die Problematik der Mehrdeutigkeit beim Laserlicht wird dadurch vielfach erleichtert oder auch gel{\"o}st. F{\"u}r kritische Anwendungsf{\"a}lle bleibt die Messung on line und in situ noch realisierbar.}, subject = {Korngr{\"o}ßenanalyse; Optische Messung; Streulicht; Optischer Partikelz{\"a}hler; Mie-Theorie; Partikelgr{\"o}ßenbestimmung; Matrix-Methode; Scattered light; Optical particle counter; Mie theory; Particle sizing; Matrix method}, language = {de} } @phdthesis{Lebedynskyy2013, author = {Lebedynskyy, Sergiy}, title = {Energieeffiziente Abscheidung von hochkonzentrierten fl{\"u}ssigen Aerosolen mit einem Autogenen Raumladungsgetriebenen Abscheider (ARA)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-30007}, school = {BTU Cottbus - Senftenberg}, year = {2013}, abstract = {Autogene Raumladungsgetriebene Abscheidung (ARA) ist ein neuartiges mehrstufiges Elektrofilter-Prinzip, das bei hohen Aerosolkonzentrationen eingesetzt werden kann und eine sehr energieeffiziente Abscheidung mit geringer Ozonproduktion gew{\"a}hrleisten kann. Die vorliegende Arbeit besch{\"a}ftigt sich mit Auslegung, Erprobung und Optimierung von ARA-Laboranlagen sowie eines ARA-Prototyps. Abscheidegrade von {\"u}ber 99,5\% werden bei einem Energieverbrauch von 20 J/m³ erzielt, was um eine Gr{\"o}ßenordnung niedriger als bei konventionellen Elektroabscheidern ist. Die Selbstentladung der Aerosole wird untersucht. Die Selbstentladung kommt in mehrstufigen Elektroabscheider-Konstruktionen, die bei hohen Aerosolkonzentrationen eingesetzt werden vor, f{\"u}hrt zu einer deutlichen Verschlechterung der Abscheideleistung und bleibt oft von den Anlagenbetreibern unbemerkt.}, subject = {Aerosol; Raumladung; Abscheider; Quenching; Selbstentladung; Elektroabscheider; Korona-Quenching; Raumladungsabscheidung; Selbstentladung; Aerosol; Electrostatic precipitator; Corona Quenching; Space charge based precipitation; Self-discharge; Aerosol}, language = {de} }