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Combining Power-to-X (PtX) processes with high temperature heat pumps (HTHP) can significantly increase their energy efficiency. Evaluating the example of oxymethylene ethers (OME) production from H2 via H2O electrolysis and captured CO2 from air shows that by upgrading waste heat streams using HTHP, a process overall energy efficiency of higher than 61 % can be achieved compared to 30 % in conventional integrated processes. Thereby, the waste heat stream from H2O electrolysis already covers the low temperature heat demand for CO2 capture via direct air capture, not only for OME but also for various PtX products. Importantly, a significant lever for the energy efficiency enhancement is the consideration of other low temperature heat-demanding sectors. High overall process energy efficiencies and the electrification of the industry are key aspects towards a sustainable mobility sector.

This study aims at developing an experimental method to characterise the fluid dynamic stress acting on particles in a lab-scale stirred tank reactor. The method is based on a photo-optical inline particle size measurement technique, which is able to capture the complex morphology of a stress-sensitive clay-floc system. The novel image-based analysis uses a Convolutional Neural Network (CNN), which was trained for particle detection. Its output provides a high-quality particle recognition for subsequent size and shape analysis throughout the flocculation process under various experimental conditions. The flocculation system is used to characterise the stress induced by four impeller geometries in the reactor. The obtained changes of floc size and shape allow to evaluate the particle stress in more detail compared to previous studies. The agreement of main findings of the floc breakage process with known literature assesses the developed method to be applied successfully in further studies.

The incorporation of soft hydrophilic particles at the interface of water in non-polar oil emulsion droplets is crucial for several applications. However, the stabilization of water in non-polar oil emulsions with hydrophilic soft material alone is, besides certain exceptions, not possible. In our previous works, we showed that stabilizing the emulsions with well-characterized spherical hydrophobic silica nanospheres (SNs) and soft equally charged microgel particles (MGs) is a robust strategy to stabilize w/o emulsions while still incorporating a large amount of MGs at the interface. In the present study, we address the question of what the maximum amount of MGs at the interface in these kinds of emulsion droplets can be. By using well-characterized mono-disperse SNs, we are able to calculate the fraction of interface covered by the SNs and complementary that of the present MG. We found that it is not possible to decrease the SN coverage below 56% irrespective of MG softness and SN size. The findings elucidate new perspectives to the broader topic of soft/solid stabilized emulsions.

Drop size distributions in liquid/liquid systems within a turbulent flow, being an integral part of many technical applications, can be simulated solving population balance equations. Experimental investigations in stirred toluene/water systems at constant ionic strength of 0.1 mol/L showed that with pH values higher than 11, coalescence is hindered considerably due to electrostatic effects. Within this work, two designated models are used to simulate the transient drop size distributions in a stirred tank, showing that the influence of droplet charge due to a change in pH value or ion concentration cannot be predicted satisfactorily by existing models. This finding motivates a new modelling approach implementing the DLVO theory into the population balance framework.

Oxymethylene dimethyl ethers (OME) are attracting interest as potential diesel substitutes and “green” solvents. They are synthesized based on methanol, which can be source from fossil or renewable feedstocks. In this thesis a potentially scalable and feasible OME synthesis process is described based on the endothermic catalytic dehydrogenation of methanol. The process flow sheet was implemented via a hybrid simulation and showed to be superior to other literature described processes. Oxymethylendimethylether (OME) sind ein interessanter Dieselersatz und Lösungsmittel. Sie werden auf Basis von Methanol hergestellt, so dass ein auf fossilen oder erneuerbaren Energiequellen basierender Rohstoff verwendet werden kann. In dieser Arbeit wird ein potenziell skalierbarer und wirtschaftlich umsetzbarer OME-Syntheseprozess beschrieben, welcher durch Prozesssimulation in einer hybriden Simulationsplattform implementiert wurde und sich gegenüber anderen Prozessen als vorteilhaft erwies.

In dieser Doktorarbeit wurden die Zusammenhänge zwischen Prozessstörungen und der mikrobiellen Biozönose in großtechnischen Biogasanlagen aus der Abfallwirtschaft und in Laborversuchen mikrobiologisch und chemisch analysiert und verschiedene Gegenmaßnahmen untersucht. Unter Einsatz von Calciumoxid als Additiv wurde die Raumbelastung in einem Laborreaktor stufenweise bis auf 9,5 kg oTS m-3 d-1 erhöht und ein Frühwarnindikator gegen Übersäuerung zur Steuerung der Zugabe eingesetzt. Die Zusammensetzung der methanogenen Gemeinschaft blieb unter dem Einfluss höherer Raumbelastungen konstant und gewährleistete eine stabile Biogasproduktion. Genetische Fingerprintanalysen zeigten, dass syntrophe Mikroorganismen aus Wasserstoff-produzierenden Bakterien und Wasserstoff-oxidierenden Archaeen die Gemeinschaft dominierten. Infolge der Calciumoxid-Zugabe bildeten sich Aggregate, die zur Stabilität des Prozesses beitrugen und wahrscheinlich als Mikrohabitat für die Mikroorganismen fungierten. Ein Ausfall der Rührwerke und die daraus resultierende ungünstige Durchmischung verursachten eine Schwimmschichtbildung sowie eine drohende Übersäuerung in einer großtechnischen Biogasanlage. Infolge des Rührwerksausfalls und der ungleichmäßigen Verteilung des organischen Materials, verstärkten sich lokale Heterogenitäten, Säuren reicherten sich an und die Gasproduktion fiel ab. Die mikrobielle Biozönose veränderte sich durch die ungünstige Durchmischung und passte sich nach der Wiederherstellung der Durchmischung wieder an. In Verbindung mit der Zugabe von hydrophoben Substanzen wurde das filamentöse Bakterium Microthrix parvicella als Verursacher einer Schaumbildung in einer Mischschlamm und Fett Co-vergärenden großtechnischen Biogasanlage identifiziert. Die Schaumbildung ereignete sich, wenn Fett zugeführt und ein Schwellenwert von 2x108 M. parvicella Genkopien überschritten wurde. Die Erhöhung der Genkopienzahlen im nachgeschalteten Reaktor der Kaskade wies auf anaerobes Wachstum ohne Nitrat hin. Der Einfluss einer Temperaturerhöhung von 37 °C auf 56 °C auf die Abundanz von Microthrix parvicella und die damit verbundene Bildung einer Schwimmschicht wurde in zwei parallel betriebenen Laborreaktoren untersucht. Die mikrobielle Biozönose passte sich an die Temperaturerhöhung von 1 °C pro Woche an, so dass der Biogasproduktionsprozess stabil ablief. Die Abundanz von M. parvicella verringerte sich bei einer Erhöhung von 37 °C auf 39-41 °C um den Faktor 10. Die Schwimmschicht löste sich bei der Erhöhung von 37 °C auf 56 °C auf., In this PhD thesis, the interaction of the microbial biocenosis and process disturbances in full-scale biogas plants and laboratory-scale reactors were analysed microbiologically and chemically and several countermeasures were investigated. In a sewage sludge and raps oil fed laboratory-scale reactor, addition of calcium oxide was used to increase the organic loading rate stepwise up to 9.5 kg VS m-3 d-1. The process was controlled by applying an early warning indicator regarding overacidification. Genetic fingerprint analysis showed that the methanogenic community composition stayed constant during the increase in organic loading rate warranting a stable biogas production process. Syntrophic microorganisms of hydrogen producing bacteria and hydrogen consuming archaea dominated the biocenosis. Due to the addition of calcium oxide, granules were formed, which contributed to the stabilization of the process and probably served as microhabitat for the microorganisms. A formation of floating sludge as well as a threatening overacidification in a full-scale biogas plant were caused by a disturbance of the agitators. Due to the mixing failure and the uneven distribution of the organic material, local heterogeneities appeared, organic acids accumulated and the gas production decreased. The microbial biocenosis changed due to the agitator breakdown and adapted again after the mixing was re-established. The introduction of hydrophobic substances and the filamentous bacterium Microthrix parvicella were identified as the cause of a foam formation in a full-scale biogas plant fed with sewage sludge and fat, oil and grease (FOG). Foaming was caused if FOG was fed and a threshold amount of 2x108 M. parvicella gene copies was exceeded. As the biogas plant is operated as a cascade, increased gene copy numbers of M. parvicella in the downstream reactor indicated anaerobic growth without reduction of nitrate as the energy source. The influence of a temperature increase from 37 °C to 56 °C on the presence of Microthrix parvicella and the associated formation of floating sludge was investigated in two parallel operated laboratory-scale reactors. The microbial biocenosis was shown to adapt to the increase in temperature by 1 °C per week, so that the biogas production process worked properly. The occurrence of M. parvicella already decreased with an increase from 37 °C to 39-41 °C by a factor of 10. The floating sludge dissolved completely after increasing the temperature from 37 °C to 56 °C.

Förderrate, Kopftemperatur und Druck einer Geothermiebohrung sind die entscheidenden Größen für die technische Machbarkeit und die Wirtschaftlichkeit eines Geothermieprojektes. Ihre Vorhersage erfordert die Kenntnis der Eigenschaften von Thermalwasser und Reservoir sowie ein detailliertes Modell des Bohrlochs und des umgebenden Gesteins. In dieser Arbeit wird ein umfassendes thermo-hydraulisches Computermodell des Thermalwasserkreislaufs einer Geothermie-Anlage vorgestellt. Es wurde parametrisiert und validiert anhand von Werten des Forschungsstandorts Groß Schönebeck. Die Berechnung der Fluideigenschaften erfolgt unter Berücksichtigung der Zusammensetzung und des ermittelten Flüssig-Dampf-Gleichgewichts. Verschiedene Anwendungen des in DYMOLA / MODELICA umgesetzten Modells werden vorgestellt. Production rate, wellhead temperature and pressure are critical parameters of a geothermal well, which determine the technical and economic viability. Their prediction requires knowledge of brine properties and reservoir characteristics as well as a detailed thermal model of the well and surrounding formation. High salinity and gas content complicate the task. This work presents a comprehensive numerical thermo-hydraulic model of the brine circuit of a geothermal plant. Implemented in DYMOLA/MODELICA, it has been parameterized and validated with data from the research site in Gross Schoenebeck, Germany. The properties of the complex brine are calculated with a compositional two-phase brine model that considers the specific gas and salt contents and determines the gas fraction with a flash calculation based on the individual gas solubilities. Different applications are demonstrated.