Universität Stuttgart

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Open Access
Life cycle assessment for early-stage process optimization of microbial biosurfactant production using kinetic models : a case study on mannosylerythritol lipids (MEL)
(2024) Bippus, Lars; Briem, Ann-Kathrin; Beck, Alexander; Zibek, Susanne; Albrecht, Stefan
Introduction: This study assesses the environmental impacts of mannosylerythritol lipids (MELs) production for process optimization using life cycle assessment (LCA). MELs are glycolipid-type microbial biosurfactants with many possible applications based on their surface-active properties. They are generally produced by fungi from the family of Ustilaginaceae via fermentation in aerated bioreactors. The aim of our work is to accompany the development of biotechnological products at an early stage to enable environmentally sustainable process optimization. Methods: This is done by identifying hotspots and potentials for improvement based on a reliable quantification of the environmental impacts. The production processes of MELs are evaluated in a cradle-to-gate approach using the Environmental Footprint (EF) 3.1 impact assessment method. The LCA model is based on upscaled experimental data for the fermentation and purification, assuming the production at a 10 m³ scale. In the case analyzed, MELs are produced from rapeseed oil and glucose, and purified by separation, solvent extraction, and chromatography. Results: The results of the LCA show that the provision of substrates is a major source of environmental impacts and accounts for 20% of the impacts on Climate Change and more than 70% in the categories Acidification and Eutrophication. Moreover, 33% of the impacts on Climate Change is caused by the energy requirements for aeration of the bioreactor, while purification accounts for 42% of the impacts respectively. For the purification, solvents are identified as the main contributors in most impact categories. Discussion: The results illustrate the potentials for process optimization to reduce the environmental impacts of substrate requirements, enhanced bioreactor aeration, and efficient solvent use in downstream processing. By a scenario analysis, considering both experimental adaptations and prospective variations of the process, the laboratory development can be supported with further findings and hence efficiently optimized towards environmental sustainability. Moreover, the presentation of kinetic LCA results over the fermentation duration shows a novel way of calculating and visualizing results that corresponds to the way of thinking of process engineers using established environmental indicators and a detailed system analysis. Altogether, this LCA study supports and demonstrates the potential for further improvements towards more environmentally friendly produced surfactants.
Open Access
Modellierung und Diagnostik einer Remote-Mikrowellen-Plasmaquelle zum Hochrateätzen
(2024) Pauly, Steffen; Tovar, Günter E. M. (Prof. Dr.)
Bei der Herstellung von Mikrosystem-Strukturen werden Fotolacke eingesetzt, um über lithografische Verfahren Oberflächenstrukturen im Sub-Mikrometerbereich herzustellen. Der Fotolack wird als dünne Schicht auf ein Substrat aufgebracht und durch eine Maske, welche die zu erhaltende Struktur enthält, über UV-Licht ausgehärtet. Dabei dient der strukturierte und ausgehärtete Lack als Schutz für die darunterliegenden Schichten oder als formgebende Struktur der unbedeckten Bereiche. Diese Bereiche können über Ätzprozesse abgetragen oder durch galvanische Abscheidung mit einer Metallschicht überzogen werden. Im Anschluss muss der ausgehärtete Fotolack wieder entfernt werden. Das Problem dabei ist, dass dieser ein hochstabiles vernetztes Material darstellt, was nur äußerst schwer wieder entfernt werden kann, ohne dass dabei die aufgebrachten Metallstrukturen oder die geschützten darunterliegenden Schichten beschädigt werden. Die Entfernung des ausgehärteten Lacks geschieht heutzutage über Trockenätzverfahren. Diese Arbeit befasst sich deshalb mit der simulativen und experimentellen Untersuchung einer im Niederdruck arbeitende Remote Mikrowellen Plasmaquelle (RMPS) der Firma Muegge GmbH, die beim trockenchemischen Hochrateätzen von Fotolacken Anwendung findet. Dazu werden Mikrowellensimulationen durchgeführt, die die Feldverteilung in der Plasmakammer bei Zündbedingungen zeigen, welche über Mikrowellenfeldversuche verifiziert werden konnten. Mit dem Drude-Modell werden vereinfachte Plasmasimulationen durchgeführt, die den Einfluss der Elektronendichte auf das Mikrowellenfeld veranschaulichen. Der visuelle Vergleich der Drude-Modell-Simulationen mit Fotografien des Plasmas verdeutlicht auch hier eine gute Übereinstimmung. Die Erweiterung der Simulation mit dem Fluid-Modell berücksichtigt Teilchenbewegungen und Reaktionen im Plasma. Die Ergebnisse zeigen den zeitlichen Verlauf der Elektronendichte in der RMPS, welche über dreidimensionale Langmuir-Sondenmessungen quantitativ validiert werden konnten.
Open Access
UV-advanced oxidation process without additives in liquid phase : process characterization and validation
(2020) Toro Santamaria, Jorge Mario; Hirth, Thomas (Prof. Dr.)
Human activities are gradually generating a strong impact on the environment and the quality of natural water resources. Traces of hazardous substances are detected not only in wastewater but also already in natural water bodies (surface and ground water) around the globe. The source of these trace substances is broad, starting with chemicals from industrial production like polycyclic aromatic hydrocarbons, pesticides, food ingredients, pharmaceuticals, to components of personal care, just to mention examples. Because of their constantly growing presence in water resources, and the fact that some of those are seriously affecting natural biological processes, there is an increasing need for finding ways to impede those substances to reach water bodies. The European community has adopted the water pollution problematic as one of their main concerns. As a result, on the 23 October 2000, the Directive 2000/60/EC of the European Commission was adopted. The main purpose of the directive is the protection of European natural water resources by enhancing the status of the water bodies as well as preventing further contamination. In particular, the requirement of complying with European environmental quality standards (EQS) for priority substances (PD) became compulsory. In order to meet these requirements and directives, industry and the scientific community working in the fields of water treatment, do approach new treatment processes with the purpose of upgrading current treatment plants to destruct or reduce trace substances. One alternative are the so called Advanced Oxidation Processes (AOPs), which are able to treat persistent and hardly biodegradable pollutants by oxidation processes. Between the varieties of potential AOPs the photo-induced advanced oxidation, centred on photolysis of water by radiation below 200 nm has received special attention. The key feature of the photo induced AOP is the facts of the efficient production of hydroxyl radicals as the highest possible oxidant and the singularity of no need for aux-iliary oxidants like hydrogen peroxide, ozone, peroxydisulfate or peroxymonosulfate, needed in other AOPs. One of the most important steps to bring the photo induced AOP to be used in the real field, is to prove that the process can be operated under efficient conditions, controlling the generation of hydroxyl radicals and utilizing them efficiently for the goal of treatment. An important action to push the technology to the path of product development is therefore, the integration of efficient UV sources to a photo reactor, taking into account the peculiarities of the process. Overall, the research presented in this thesis focuses on the characterization of the photoreaction zone, the light penetration and absorption process as well as the hydroxyl radical generation and provides the understanding and database to enable different approaches for the engineering of photo induced AOP. Concretely, this thesis is structured in five parts. Part I includes the literature search and its analysis; different calculations and simulations were performed with the aim of describing the heterogeneity of the reaction zone, the theoretical penetration of radiation in water and understanding the theoretical spatial generation of hydroxyl radicals. Part II includes the reactor characterization. The photo induced AOP was first tested following the degradation of Methylene Blue (MB). Subsequently it was studied the impact of the channel dimen-sions in the oxidation process under different operational parameters and the characterization of the photo reactor in terms of radiation intensity using three different methods. Part III includes the process characterization where the investigations were focused on the penetration of radiation into water and the generation of hydroxyl radicals by means of two methodologies: the transmission measurements in thin water films and the degradation of methanol as reference substance. Part IV includes the tailor made reactor validation. In this part, the focus was directed to verify the numeric models and gain data enabling the design, construction and validation of a reactor system using flat lamps. Validation of the photo induced AOP was performed by means of degradation of the pharmaceuticals Sulfaquinoxaline (SQX) and Carbamazepin (CBZ), as well as the degradation of an organic substance coming from the chemical industry Bisphenol A (BPA) and a food ingredient Caffeine (CAF). During the validation phase the concentration of the substances, the Total Organic Carbon (TOC) and the cytotoxicity using VERO and COS cell lines for each experiments were followed. Part V summarizes the results. In general, it was found that the process shows attractive potential and advantages in comparison with other oxidation technologies. For example: the steady and local production of hydroxyl radical without the addition of supplementary oxidation agents; the not strong selectivity and the capacity of mineralization of the process; the pH independency of the oxidation process; the fact that cytotoxicity of the byproducts does not overpass the initial toxicity of the tested substances and the Dose requirements for oxidation is comparable with existing process without using any additive.
Open Access
CHEMampere : technologies for sustainable chemical production with renewable electricity and CO2, N2, O2, and H2O
(2022) Klemm, Elias; Lobo, Carlos M. S.; Löwe, Armin; Schallhart, Verena; Renninger, Stephan; Waltersmann, Lara; Costa, Rémi; Schulz, Andreas; Dietrich, Ralph‐Uwe; Möltner, Lukas; Meynen, Vera; Sauer, Alexander; Friedrich, K. Andreas
The chemical industry must become carbon neutral by 2050, meaning that process‐, energy‐, and product‐related CO2 emissions from fossil sources are completely suppressed. This goal can only be reached by using renewable energy, secondary raw materials, or CO2 as a carbon source. The latter can be done indirectly through the bioeconomy or directly by utilizing CO2 from air or biogenic sources (integrated biorefinery). Until 2030, CO2 waste from fossil‐based processes can be utilized to curb fossil CO2 emissions and reach the turning point of global fossil CO2 emissions. A technology mix consisting of recycling technologies, white biotechnology, and carbon capture and utilization (CCU) technologies is needed to achieve the goal of carbon neutrality. In this context, CHEMampere contributes to the goal of carbon neutrality with electricity‐based CCU technologies producing green chemicals from CO2, N2, O2, and H2O in a decentralized manner. This is an alternative to the e‐Refinery concept, which needs huge capacities of water electrolysis for a centralized CO2 conversion with green hydrogen, whose demand is expected to rise dramatically due to the decarbonization of the energy sector, which would cause a conflict of use between chemistry and energy. Here, CHEMampere's core reactor technologies, that is, electrolyzers, plasma reactors, and ohmic resistance heating of catalysts, are described, and their technical maturity is evaluated for the CHEMampere platform chemicals NH3, NOx, O3, H2O2, H2, CO, and CxHyOz products such as formic acid or methanol. Downstream processing of these chemicals is also addressed by CHEMampere, but it is not discussed here.
Open Access
Hydrogen-tolerant La0.6Ca0.4Co0.2Fe0.8O3-d oxygen transport membranes from ultrasonic spray synthesis for plasma-assisted CO2 conversion
(2023) Rashid, Aasir; Lim, Hyunjung; Plaz, Daniel; Escobar Cano, Giamper; Bresser, Marc; Wiegers, Katharina-Sophia; Confalonieri, Giorgia; Baek, Sungho; Chen, Guoxing; Feldhoff, Armin; Schulz, Andreas; Weidenkaff, Anke; Widenmeyer, Marc
La0.6Ca0.4Co1-xFexO3-d in its various compositions has proven to be an excellent CO2-resistant oxygen transport membrane that can be used in plasma-assisted CO2 conversion. With the goal of incorporating green hydrogen into the CO2 conversion process, this work takes a step further by investigating the compatibility of La0.6Ca0.4Co1-xFexO3-d membranes with hydrogen fed into the plasma. This will enable plasma-assisted conversion of the carbon monoxide produced in the CO2 reduction process into green fuels, like methanol. This requires the La0.6Ca0.4Co1-xFexO3-d membranes to be tolerant towards reducing conditions of hydrogen. The hydrogen tolerance of La0.6Ca0.4Co1-xFexO3-d (x = 0.8) was studied in detail. A faster and resource-efficient route based on ultrasonic spray synthesis was developed to synthesise the La0.6Ca0.4Co0.2Fe0.8O3-d membranes. The La0.6Ca0.4Co0.2Fe0.8O3-d membrane developed using ultrasonic spray synthesis showed similar performance in terms of its oxygen permeation when compared with the ones synthesised with conventional techniques, such as co-precipitation, sol-gel, etc., despite using 30% less cobalt.
Open Access
Growth behavior of selected Ustilaginaceae fungi used for mannosylerythritol lipid (MEL) biosurfactant production - evaluation of a defined culture medium
(2020) Beck, Alexander; Zibek, Susanne
Fungi of the Ustilaginaceae family are a promising source for many biotechnologically relevant products. Among these, mannosylerythritol lipid (MEL) biosurfactants have drawn a special interested over the last decades due to their manifold application possibilities. Nevertheless, there is still a knowledge gap regarding process engineering of MEL production. As an example, no reports on the use of a chemically defined culture medium have been published yet, although such a defined medium might be beneficial for scaling-up the production process toward industrial scale. Our aim therefore was to find a mineral medium that allows fast biomass growth and does not negatively affect the successive MEL production from plant oils. The results showed comparable growth performance between the newly evaluated mineral medium and the established yeast extract medium for all seven investigated Ustilaginaceae species. Final biomass concentrations and specific growth rates of 0.16-0.25 h-1 were similar for the two media. Oxygen demand was generally higher in the mineral medium than in the yeast extract medium. It was shown that high concentrations of vitamins and trace elements were necessary to support the growth. Increasing starting concentrations of the media by a factor of 10 resulted in proportionally increasing final biomass concentrations and up to 2.3-times higher maximum growth rates for all species. However, it could also lead to oxygen limitation and stagnant growth rates when too high medium concentrations were used, which was observed for Ustilago siamensis and Moesziomyces aphidis. Successive MEL production from rapeseed oil was effectively shown for 4 out of 7 organisms when the mineral medium was used for cell growth, and it was even enhanced for two organisms, M. aphidis and Pseudozyma hubeiensis pro tem., as compared to the established yeast extract medium. Conversion of rapeseed oil into MEL was generally improved when higher biomass concentrations were achieved during the initial growth phase, indicating a positive relationship between biomass concentration and MEL production. Overall, this is the first report on the use of a chemically defined mineral medium for the cell growth of Ustilaginaceae fungi and successive MEL production from rapeseed oil, as an alternative to the commonly employed yeast extract medium.
Open Access
Improving determination of pigment contents in microalgae suspension with absorption spectroscopy : light scattering effect and Bouguer-Lambert-Beer law
(2023) Yeh, Yen-Cheng; Ebbing, Tobias; Frick, Konstantin; Schmid-Staiger, Ulrike; Haasdonk, Bernard; Tovar, Günter E. M.
The Bouguer-Lambert-Beer (BLB) law serves as the fundamental basis for the spectrophotometric determination of pigment content in microalgae. Although it has been observed that the applicability of the BLB law is compromised by the light scattering effect in microalgae suspensions, in-depth research concerning the relationship between the light scattering effect and the accuracy of spectrophotometric pigment determination remains scarce. We hypothesized that (1) the precision of spectrophotometric pigment content determination using the BLB law would diminish with increasing nonlinearity of absorbance, and (2) employing the modified version of the BLB (mBLB) law would yield superior performance. To assess our hypotheses, we cultivated Phaeodactylum tricornutum under varying illumination conditions and nitrogen supplies in controlled indoor experiments, resulting in suspensions with diverse pigment contents. Subsequently, P. tricornutum samples were diluted into subsamples, and spectral measurements were conducted using different combinations of biomass concentrations and path lengths. This was carried out to assess the applicability of the BLB law and the nonlinearity of absorbance. The chlorophyll a and fucoxanthin contents in the samples were analyzed via high-performance liquid chromatography (HPLC) and subsequently used in our modeling. Our findings confirm our hypotheses, showing that the modified BLB law outperforms the original BLB law in terms of the normalized root mean square error (NRMSE): 6.3% for chlorophyll a and 5.8% for fucoxanthin, compared to 8.5% and 7.9%, respectively.
Open Access
Investigations and technical development of adsorption thermal energy storage systems with simulation and different control strategies
(2021) Abou Elfadil, Mazen; Hirth, Thomas (Prof. Dr.)
Thermal energy storage (TES) has been receiving an increasing worldwide attention, especially with the growing concerns about environmental problems caused by an inefficient utilization of energy. A major part of the energy consumption is considered as low temperature thermal energy. Thus, a better management of this energy by using thermal energy storage could provide a significant contribution to improve the overall efficiency of energy utilization in industrial processes and economies. The thermal energy can be stored in different forms e.g. sensible heat, latent heat or thermo-chemical, allowing variety of choices depending on the application. While the sensible and latent heat storage technologies are standard products, the thermo-chemical energy storage is still under development. Based on the method used, thermo-chemical energy storage can be divided into absorptive and adsorptive thermal energy storage systems. The adsorptive thermal energy storage systems have a great potential in both daily (short term) and seasonal (long term) applications. However, their implementation is still limited due to their low degree of applicability caused by lack of scientific knowledge on the thermal analysis level, as well as the absence of knowledge on the level of system integration, which has prevented the heat storage systems from reaching their maximum potential and from being fully commercialized. Consequently, there is still a big necessity for research and development in this field [Salvatore Vasta, 2018]. The principle of the adsorption storage system is based on a gaseous working fluid (e.g. water resp. vapor) which gets adsorbed by a highly porous material (e.g. zeolite). This adsorption process is an exothermal one, thus heat is being released and can be transferred and used. In order to recharge the heat storage system, desorption of the working fluid is done by heating the porous material. The heat storage system consists mainly of a reactor (where the porous material is located), a condenser/evaporator and other auxiliary components (e.g. water tank, pumps, sensors…). Efforts of development of the adsorptive TES were concentrated mainly on developing the adsorptive material, as the performance of the storage material has been the priority so far [Salvatore Vasta, 2018]. Little focus was put on heat power analysis and temperature behavior in the different system components, which have an impact on the overall system efficiency. Thus, system approach is still needed in order to combine and integrate this technology into industrial applications and products [Hauer, Andreas 2020] [Michelangelo Di Palo 2020]. With the aim of improving the heat storage efficiency (recovered heat to stored heat ratio), both numerical (simulations) and experimental (technical modifications) approaches were applied, which have enabled the system to achieve an optimal operational status in terms of energy utilization and efficiency. These approaches were later on used to define a fully automated control system assisting the adsorption TES to instantly react with the continuously varying parameters in such a way to assure an optimal performance. Hence, in the first stage of this investigation, process-modeling and simulation of the whole heat storage system were carried out, so that the total performance of the heat storage system can be predicted and evaluated for any future applications, including the possibility of combining different reactors or heat storage units. In the second stage, different experiments and technical modifications of the system were conducted. This includes testing various possibilities of TES setups (e.g. storage cascades), where the different pressure and temperature behavior in the reactor were evaluated. With the help of experiments, a detailed numerical 3D-model of the packed bed was created, giving an insight into the heat and mass transfer in the reactor during both adsorption and desorption. As a result, a new heat exchanger design was developed, which has improved the temperature distribution and the heating/cooling power. Additionally, the simulation’s results suggested the separation between the evaporator and the condenser to achieve an enhanced water vapor transfer between the reactor and condenser. On a parallel stage of this investigation, comprehensive heat power analysis during both adsorption and desorption processes was carried out, which has showed that the sensible heat left in the reactor, contributes to ca. 50% of the total stored heat. Consequently, multiple reactor concept was introduced, in order to enable the sensible heat recovery. As a conclusion, process simulation enabled tests with different parameters to be performed within much shorter time than the real experimental time. Thus, it was possible to cover numerous application-scenarios and help improving the system overall efficiency. The experimental results have shown that the developed heat exchanger design has increased the maximum power of the heat exchanger about 74%. Moreover, by improving the fluid dynamics between the reactor and condenser, the efficiency of desorption ηd and overall efficiency ηo were increased by 32% and 9% respectively. Furthermore, about 36% of the sensible heat left in the reactor after desorption was recovered by using multiple reactors with sequential configuration, which has led to a reduction in the total invested heat by ca. 9%. For future work it’s recommended to investigate the possibility of controlling the amount of discharged heat from the system by regulating the water uptake during adsorption. In addition, trying a different approach to the reactor’s design (e.g. moving bed reactor) could bring significant improvements to the system.
Open Access
Experimental progress in the development of a metal foil pump for DEMO
(2023) Kathage, Yannick; Vazquez Cortes, Alejandro; Merli, Stefan; Day, Christian; Giegerich, Thomas; Hanke, Stefan; Igitkhanov, Juri; Schulz, Andreas; Walker, Matthias
Experimental findings to contribute to the preliminary design of a metal foil pump for fuel separation in the Direct Internal Recycling loop of the DEMO fusion device are presented. In parametric studies on a small-scale superpermeation experiment with a microwave plasma source and two different metal foil materials, niobium Nb and vanadium V, a substantial increase in permeation with plasma power and with a decrease in pressure was observed. To ease operation in the typical fusion environment, in-situ heating procedures were developed to recover from impurity contamination. The temperature independence of plasma-driven permeation from 600 to 900 °C metal foil temperature was demonstrated. No proof of an isotopic effect for plasma-driven permeation of protium and deuterium could be found. The highest repeatable permeation flux achieved was 6.7 Pa∙m3/(m2∙s) or ~5.5 × 10-3 mol H/(m2∙s). The found compression ratios do safely allow the operation of the metal foil pump using ejector pumps as backing stages for the permeate. In a dedicated experimental setup, the operation of the plasma source in a strong magnetic field was tested. Parametric studies of pressure, power input, magnetic flux density, field gradient and field angle are presented.
Open Access
Strömungsdynamik und Stofftransport in einem Strahl-Kolonnenflotationsapparat zur Abtrennung oberflächenaktiver Substanzen aus wässrigen Stoffströmen
(2020) Ziegler, Eike Eric; Hirth, Thomas (Prof. Dr. rer. nat.)
Die Arbeit befasst sich mit der Untersuchung eines Strahl-Kolonnenflotationsapparates, der zur Reinigung und Konditionierung von Prozesswasser eingesetzt wird. Um den Einfluss der Strömungsdynamik auf den Stofftransport von oberflächenaktiven Substanzen (OAS) an die Phasengrenzfläche besser zu verstehen, wurden einzelne Bereiche des Apparates bezüglich der funktionalen Zusammenhänge zwischen den einzelnen Betriebsparametern näher untersucht. In einem ersten Schritt wurde die Strömungsdynamik in einem exemplarischen FSA mit Finite-Pointset-Method (FPM), einem punktbasierten Strömungssimulations-CFD-Programm, simuliert, um die Ausbreitung des Treibstrahles in der Mischkammer und dort auftretende lokale Strömungszonen zu visualisieren. Basierend auf den Simulationsergebnisse wurden fünf Treibdüsengeometrien gefertigt und für die Untersuchung der Blasenströmung im Flotationsbehälter hinzugezogen. Diese Treibdüsen wurden in ein handelsübliches Strahlapparatgehäuse eingesetzt, um zusätzlich zur Treibdüsengeometrie den Einfluss des Treibdruckes und von koaleszenzverändernden Substanzen auf die erzeugte Blasenströmung zu untersuchen. Durch Variation der Konzentration von sieben unterschiedlichen Salzen mit charakteristischen Ionenkombinationen und Fokus auf Natriumchlorid, wurde das Koaleszenzverhalten der Blasenströmung in einem Konzentrationsbereich zwischen 0 und 30 g/l unter Messung von Blasengröße und Gasanteil erfasst. Durch Definition einer Blasenaufstiegsfunktion, die den funktionalen Zusammenhang zwischen mittlerer Blasenaufstiegsgeschwindigkeit und Sauterdurchmesser in der Blasenströmung beschreibt, kann für die einzelnen Betriebszustände die Flussdichte der Phasengrenzfläche Sb approximiert werden, die als Schlüsselparameter zur Bestimmung der Flotationsrate gilt.Aufgrund der Inhibierung von Koaleszenz in der Blasenströmung fällt für kosmotrophe Salze die Blasengröße mit steigender Salzkonzentration entlang einer Exponential-Funktion. Hierdurch steigt der Gasanteil in dem Flotationsbehälter entlang einer Sigmoid-Funktion an und die Flussdichte der Phasengrenzfläche nimmt zu. Mit Sodium-Dodecyl-Sulfat (SDS) als oberflächenaktiver Modellsubstanz wurde dessen Abreicherung anhand von Batch-Versuchen unter Variation der Gasleerrohrgeschwindigkeit, der SDS-Konzentration und der NaCl-Konzentration mit einem hierfür entwickelten Gasanteilsensor messtechnisch erfasst. Aus den Messdaten wurde die Konzentrationsabnahme in Abhängigkeit der Flotationszeit berechnet und in Bezug zur Flussdichte der Phasengrenzfläche gesetzt. Die Ergebnisse wurden zur Erstellung eines Berechnungsprogramms genutzt, welches den Stofftransport an die Phasengrenzfläche durch eine flächenbezogene Anlagerungsfunktion berechnet. Diese ist entweder in ein Differentialgleichungssystem eingebettet oder wird in einer Berechnungsschleife mit thermodynamisch begründeter Adsorptionsisotherme genutzt. Damit kann der Einfluss von Gasleerrohrgeschwindigkeit und Flussdichte der Phasengrenzfläche auf die Flotation gezeigt und der Bezug zu der Abreicherung von OAS und den hierbei auftretenden Stofftransport hergestellt werden.

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