Why did you decide to write your doctoral thesis at Fraunhofer UMSICHT?

Christian Geitner: After studying mechanical engineering in Bochum, I thought about how I could further deepen my passion for independent work and scientific challenges. I considered doctoral studies to be the ideal way to take responsibility for my own project and present the results myself. Fraunhofer UMSICHT is also close to where I studied – I got to know the institute during a lecture excursion and was immediately impressed by the practical research and modern laboratories. Later, I discovered a job advertisement that perfectly matched my area of interest in modeling and simulation. The opportunity to work on current issues in an interdisciplinary team convinced me – and that's how I ended up at UMSICHT.

 

Can you explain what modeling and simulation actually involve?

Christian Geitner: Modeling and simulation is very versatile. There are data-driven models (for example, with artificial intelligence and machine learning) and physics-based models that are based on known laws of nature. I find the so-called continuum models particularly exciting: These simulate processes such as flows or concentration distributions without considering individual atoms – you work with a "uniform mass." These models are described using differential equations and are widely used in mechanical engineering. I used tools such as Aspen and COMSOL to model chemical-technical processes – this was the topic of my master's thesis and was further explored in my doctoral studies.

 

What exactly were your doctoral studies about?

Christian Geitner: I did my doctorate as part of the Carbon2Chem^® joint research project. The aim was to reuse metallurgical gases from steel production and develop sustainability-oriented processes. My focus was on gas purification, specifically adsorption in electrically heated fixed beds – ideally using green electricity. I modeled and simulated the process to show how efficient and sustainable it is. My colleague Martin Peters took care of the experimental implementation, while I concentrated on the theoretical side.

 

What was the collaboration between theory and experiment like?

Christian Geitner: The integration of model and experiment was planned from the outset: One person develops the model, the other provides the experimental data for comparison. Unfortunately, there were a few challenges during the development of the plant, so that not all the desired data was always available. That's why I validated my model primarily with literature data – this is quite common in research projects when new plants are built and the experimental data is not yet complete.

 

How long did you work on your doctoral thesis?

Christian Geitner: I completed my doctoral studies in less than three years – it was actually one of the fastest doctoral theses at Fraunhofer UMSICHT.

 

How did the UMSICHT Research School support you?

Christian Geitner: I was one of the first to benefit from the Research School. It was a great help to me, especially in structuring my work and sharpening my scientific questions. The external coach repeatedly provided important input, for example: "What is new about your work?" or "Have you identified a research gap?" The exchange with other doctoral students and the mutual feedback on texts helped me to find the central theme and strengthen my argumentation.

 

What made the Research School special for you?

Christian Geitner: The regular meetings and the opportunity to submit my own texts and receive constructive feedback were very valuable. You learn to accept criticism and grow from it. Especially in the beginning, this helps enormously in sharpening your own research questions and presenting complex issues in an understandable way.

 

Are there any anecdotes from your doctoral studies that you would like to share?

Christian Geitner: One nice anecdote is the Research School's checklist, with questions such as: "How much of your work is research, how much is routine?" or "Have you already given a presentation at a specialist conference?" Once, a colleague came back from a conference and was asked how it was. His answer: "It was also professionally quite good." That sometimes sums it up – conferences are important, but social interaction is also part of it.

 

What did you do after completing your doctoral studies?

Christian Geitner: I stayed at Fraunhofer UMSICHT and continue to work on the Carbon2Chem^® project, which is now in its third phase. My focus remains on modeling and simulation, now increasingly with data-driven approaches. It was a conscious decision for me to stay in research, even though some of my colleagues from the Research School later moved into industry.

 

How would you explain your work to someone outside the field?

Christian Geitner: I am a "computational engineer," so to speak. Similar to calculating whether a bridge will hold, complex chemical processes can also be simulated on a computer. This is often complicated, but calculations are an important piece of the puzzle for any technical plant. Roughly speaking, I simulate processes on the computer to find out how they would have to work in practice – without having to build the plant first.

 

Do you have any tips for future doctoral students?

Christian Geitner: Absolutely! There's a saying I once heard that I like to pass on: There are perfect papers and there are finished papers – set yourself a clear framework and bring your work to a conclusion instead of always adding yet another detail. Explain your results clearly and comprehensibly, even if they seem obvious. This will make your work understandable to others and increase its quality.