Art:

Masterarbeit, Studienarbeit

Themenbereich

Simulativ

Thema

Level: 

Master Thesis

Topic Area: 

Simulation and Modelling

Topic:

Disperse multiphase flows frequently occur in process engineering. They exhibit highly complex fluid dynamics that are still difficult to predict today. An Euler-Euler approach with interphase penetrating (pseudo-continuous) approach is commonly used to describe industry-scaled processes. By considering the dispersed phase as a continuum, almost all properties of the dispersed phase are lost (size, shape, etc.). This makes it difficult to predict the complex fluid dynamic behavior. In order to better represent the properties of the dispersed phase, the kinetic theory of fluid particle flow (KTFPF) was recently developed. The solution of the KTFPF together with the equations for the liquid phase is very complex and requires a numerical solution method that is both accurate and robust. One suitable method is discontinuous Galerkin spectral element method (DGSEM), which combines concepts from the finite element and volume methods. As a starting point, this work aims to solve a single-phase pipe flow using the DGSEM method.

Goals:

Requirements: 

• Advanced experience in coding is required

More Information

Contact:  

Ferdinand Breit

Disperse multiphase flows frequently occur in process engineering. They exhibit highly complex fluid dynamics that are still difficult to predict today.

That's why, in addition to the work advertised on this page, there are other exciting tasks and ideas that can be explored on request. There are many other exciting areas of work, both experimental and simulated. For example:

Art: 

Studienarbeit, Forschungsarbeit, Projektarbeit, Bacherlorarbeit

Themenbereiche: 

Experimentell

Thema:

Die Phosphatentfernung aus dem Abwasser in Kläranlagen ist essentiell, um eine Eutrophierung von Gewässern zu verhindern. Üblicherweise erfolgt dies durch Fällung, könnte jedoch auch durch eine Adsorption von Phosphat, bspw. in einem Festbettreaktor, realisiert werden. Dieser Adsorptionsprozess wird in seiner Effizienz maßgeblich von verschiedenen Betriebs- und Konstruktionsparametern (z. B. Geometrie der Säule, Volumenströme, Partikeldurchmesser etc.) beeinflusst. Auch die Eigenschaften des verwendeten Adsorbens spielen hinsichtlich der Kapazität sowie der Adsorptions- und Diffusionseigenschaften im Partikelinneren eine große Rolle. Der Einfluss dieser Parameter kann durch die Messung von Durchbruchskurven bestimmt werden.

Aus diesem Grund soll in dieser Arbeit das Adsorptionsverhalten von Phosphat für unterschiedliche geometrische und hydraulische Parameter untersucht werden. Es sollen unterschiedliche Säulengeometrien durch eine Variation des Verhältnisses von Länge zu Durchmesser getestet werden. Außerdem sollen die Leerrohrgeschwindigkeit und die Partikelgröße des Adsorbens variiert werden. Um den Einfluss der Porosität auf die Adsorption zu untersuchen, sollen unterschiedliche Packungstechniken für das Festbett angewandt werden. Des Weiteren soll die Strömungsführung variiert werden, um fluiddynamische Einflüsse zu untersuchen. Mit den gewonnenen Daten sollen anschließend Betriebspunkte für verschiedene Geometrien verglichen und bewertet werden.

Ziele: Ziel dieser Arbeit ist die experimentelle Untersuchung des Einflusses geometrischer und hydraulischer Parameter auf das Adsorptionsverhalten von Phosphat in Festbettreaktoren zur Identifikation optimaler Betriebsbedingungen.

Anforderungen: Laborerfahrung vorteilhaft.

Ansprechpartner:  Christina Zipp

Level: 

Master Thesis

Topic Area: 

Modelling and simulation

Topic:

Mehrphasenprozesse treten in der Verfahrenstechnik häufig auf (z. B. Gas-Flüssig-Reaktoren, Blasensäulen oder Rührkessel). Ihre modellgestützte Auslegung ist von zentraler Bedeutung. Üblicherweise erfolgt sie über idealisierte Reaktorkonzepte wie den idealen Rührkessel oder das Strömungsrohr. Ein wesentliches Problem dieser vereinfachten Apparatemodelle besteht jedoch darin, dass bei der Anwendung auf mehrphasige Prozesse viele Informationen über die disperse Phase verloren gehen. Dadurch können auslegungsrelevante Fragen wie etwa der Einfluss des Gasdispergierers auf den Umsatz nicht beantwortet werden. Um diese Lücke zu schließen, wurde am LRF das Multifluid-Populationsbilanzmodell (MPB) entwickelt. Es erweitert die herkömmlichen idealisierten Reaktormodelle um eine Populationsbilanz, sodass die Eigenschaften der dispersen Phase berücksichtigt und realitätsnäher abgebildet werden können. In einer Reihe von Veröffentlichungen konnte eindrucksvoll gezeigt werden, dass das Modell bereits mit wenigen Daten trainiert werden muss, um zuverlässig zu inter- und extrapolieren. Mit dem Aufkommen datengetriebener Methoden des maschinellen Lernens stellt sich nun die Frage, inwiefern ML-Modelle im Vergleich zum physikalisch fundierten MPB eine ähnliche oder sogar bessere Leistungsfähigkeit zeigen. Die vorliegende Arbeit widmet sich genau diesem Vergleich sowie der möglichen Kombination beider Ansätze.

More Information

Contact:  

Ferdinand Breit

Level: 

Study project, Bachelor Thesis, Master Thesis

Topic Area: 

Experimental

Topic:

Citric acid is a major chemical commodity produced and consumed globally. Industrially, it is produced via fermentation using Aspergillus niger. To remove byproducts and other contaminants from the fermentation broth, the medium is first filtered to eliminate solids. Following this, a precipitation reaction is carried out in which citric acid reacts with calcium hydroxide to form insoluble tricalcium citrate, which can then be filtered out, separating it from dissolved impurities in the liquid phase.

As part of the Smart Batch Processes project, the flexible operation of this chemical reaction will be investigated. To simulate the process on an industrial scale, a reaction kinetic model is required. Therefore, a kinetic study of the system will be conducted in a 30 L batch stirred tank reactor, aiming to quantify the temperature and concentration dependence of the reaction rate.

The resulting kinetic data will be used to model the reaction as a system of ordinary differential equations (ODEs) using the Julia programming language. This will allow the flexible operation of the process to be explored through both experiments and simulations.

Goals: Measuring Kinetic Data of a Precipitation Reaction and Fitting a Kinetic Model to it.

Requirements: Experience in laboratory work is an advantage.

Contact:  

Thomas Grießer

Level:

• Master

Type:

• Modelling and Simulation

Topc:

Disperse multiphase flows often occur in process engineering. Knowledge of the size of the fluid particles is important for model-based design. The size influences the mass and heat exchange as well as the residence time of the dispersed phase in the apparatus. A thorough understanding of this is therefore necessary for the design of the apparatus in terms of yield, selectivity, separation efficiency, etc. To describe the change in size, the population balance equation is usually used, which can describe phenomena such as fluid particle breakage, coalescence, growth, and nucleation in a statistical manner. In PBE, the number is usually balanced, i.e., how many bubbles per size class and volume. However, millions of particles can occur in process engineering apparatus, making the numerical solution susceptible to rounding errors. Other balance variables such as mass or volume are also possible, but lead to a more complex formula for the PBE, which in turn has numerical disadvantages. For this reason, this thesis will examine the different balance quantities, e.g., number, mass, volume, with regard to different size types (length, volume, mass) in terms of different properties (efficiency, stability, conservation properties).

Goals

• Transformation of the PBE in mass, number and volume base with internal coordinates mass, volume and length.

Requirements:

• Experience in coding

Start:

• Now

Duration

• Six months

Ansprechpartner:

• ferdinand.breit(at)rptu.de

Level:

• Master

Type:

• Modelling and Simulation

Topc:

Disperse multiphase flows often occur in process engineering. Knowledge of the size of the fluid particles is important for model-based design. The size influences the mass and heat exchange as well as the residence time of the dispersed phase in the apparatus. A thorough understanding of this is therefore necessary for the design of the apparatus in terms of yield, selectivity, separation efficiency, etc. To describe the change in size, the population balance equation is usually used, which can describe phenomena such as fluid particle breakage, coalescence, growth, and nucleation in a statistical manner. In some processes, it is desirable that the dispersed phase is completely absorbed, meaning that the particles first shrink and then disappear due to mass transfer. In this work, a new model for describing the change in size due to mass transfer will be derived and implemented. Subsequently, the model predictions will be investigated with regard to sensitivity of the model parameters and compared with experimental data from the literature.

Goals:

• Modelling:
  • Derivation of a bubble shrinkage model based on a Lagrangian approach with curved interface and time-varying film model.
• Simulation:

  • Verification of model predictions using individual bubble experiments from the literature.

  • Implementation of the model in an existing PBE model.

Requirements:

• Experience in coding

Start:

• Now

Duration

• Six months

Ansprechpartner:

• ferdinand.breit(at)rptu.de

Art:

• Master thesis

Topic Area:

Mass transfer with chemical reaction in two-phase systems

Topic:

Gas-liquid reactors are widely used in industrial applications. Several processes, such as hydrogenation, halogenation, sulfonation, nitration, oxidation of organic and inorganic compounds, are performed in gas-liquid reactors where reactions between liquid and gaseous reactants take place [1]. These reactors have a crucial role in transforming raw materials into valuable products in industries such as pharmaceuticals, petrochemicals, and environmental engineering.

To optimize mass transfer in gas-liquid reactors, it is essential to have a comprehensive understanding of the reaction kinetics and carefully consider factors such as mixing, interfacial area, mass transfer coefficient, temperature, pressure, and more. By investigating these factors, we can enhance our understanding of the underlying mass transfer mechanisms and develop strategies to optimize reactor design and operation.

Aims:

In this work, sulphite oxidation is used to measure mass transfer coefficient in a gas-liquid mixing reactor, and the influence of different mixing intensities on mass transfer and hydrodynamic parameters such as bubble diameter, gas hold-up, and interfacial area is investigated. By studying these factors, useful insights can be gained into the dominant mass transfer mechanisms within the reactor.

Requirements:

• Basic knowledge of mass transfer and fluid mechanics.
• Ability to work independently.
• Independent problem solving.
• Experience with experimental equipment and/or laboratory experience is desirable.

Reference: [1] M. Pisu, A. Cincotti, G. Cao, F. Pepe, Studies in Surface Science and Catalysis, Volume 133, 2001, Pages 471-476.

Contact:Seyedeh-Saba Ashrafmansouri

Level: 

Master thesis

Topic Area: 

Experimental work

Topic:

Many syntheses are often accompanied by side reactions in which unwanted side-products are formed. The formation of these side-products results in inefficient use of raw materials and reduces the yield of the target product. Furthermore, in many cases, it necessitates downstream separation processes to obtain the target product with high purity. Achieving higher selectivities toward the target products in such syntheses is an economically and environmentally important goal. This goal can be achieved not only by chemical means, such as catalysis, but also by physical means, such as manipulating mixing intensity, reactor type, and the rate and location of reactant feed.

The present study focuses on the process of reactant mixing and its influence on reaction rate and product distribution. When the reaction's time constant is on the same order of magnitude as or less than the mixing time constant, the reaction is considered mixing-sensitive. In this thesis, the product distribution of a mixing-sensitive reaction system (Villermaux-Dushman reaction) will be experimentally investigated in a jet loop reactor. The Villermaux-Dushman reaction involves three competitive parallel reactions (one desired and two undesired). Under ideal mixing conditions, only the desired reaction occurs, but poor mixing can lead to the occurrence of the undesired second and third reactions. Therefore, the selectivity of the desired products can serve as an evaluation criterion to assess mixing conditions and mixing scales (micro-, meso-, macro-mixing).

Goals: 

• Theory:
  • Literature survey on jet loop reactors, different mixing scales, and the Villermaux-Dushman reaction.
• Experimental Work:
  • Investigation of the transition between meso-, micro-, and backmixing for different feed tube diameters.
  • Investigation of backmixing at low feed rates.

Requirements: 

• Basic knowledge of mass transfer, reaction engineering, and fluid mechanics.
• Ability to work independently.
• Independent problem solving.
• Experience with experimental equipment and/or laboratory experience is desirable.

Start:

October 2025

Duration:

Six months

Contact:

Arvid Kraus

Seyedeh-Saba Ashrafmansouri

Art: 

Art:

Teamarbeit, Studienarbeit, Forschungsarbeit, Projektarbeit

Themenbereich

Konstruktiv, Experimentell

Thema

Art:

• Masterarbeit

Themenbereiche:

• Experimentell

Thema:

Wenn die Geschwindigkeit einer Reaktion extrem hoch ist, kann die Vermischung der Edukte eine große Rolle für die Selektivität spielen. Im Gegensatz zu kinetisch limitierten Reaktionen gibt es für diese mischungssensitiven Reaktionen keine einfachen Modellansätze, die den Einfluss verschiedener Prozessvariablen, wie z.B. der Feedeintrittsgeschwindigkeit oder der Lage der Feedpunkte, auf die Selektivität der Reaktion zuverlässig beschreiben können. Aus diesem Grund wird am Fraunhofer ITWM in Zusammenarbeit mit dem LRF eine CFD-basierte Methode entwickelt, die diese Zusammenhänge zuverlässig beschreiben soll. Um die Qualität der Modellvorhersage zu überprüfen, werden im Rahmen dieser Arbeit experimentelle Untersuchungen durchgeführt.

Dazu sollen zwei verschiedene Untersuchungen an einem einfachen einphasigen Reaktor durchgeführt werden. Zum einen sollen mittels Particle Image Velocimetry (PIV) Messungen die Strömungsverhältnisse im Einlaufbereich erfasst werden. Zum anderen sollen in diesem Reaktor umfangreiche Parameterstudien mit mischungssensitiven Testreaktionen durchgeführt werden.

Ziele:

• Aufbau einer Messapparatur und Durchführung von fluiddynamischen und reaktiven Studien von mischungssensitiven Reaktionen.

Anforderungen:

• Erfahrung im Labor vorteilhaft

Ansprechpartner:

• Erik von Harbou
• Seyedeh-Saba Ashrafmansouri