A packed bed reactor setup at Umicore Denmark, used for activity measurements by Steen. Photo: Umicore Denmark ApS

PhD interview: Removing hazardous NOx-gasses from marine industry

Monday 10 Dec 18
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Steen Riis Christensen is one of the many PhD students who graduate from DTU Chemical Engineering every year. We interviewed him about his project “Selective Catalytic Reduction of NOx on ships”.

At DTU Chemical Engineering, we are proud of our PhD students. We talked to recently graduated PhD student Steen Riis Christensen about his PhD project.

What is the essence of your PhD project?
I did my research in exhaust gas cleaning of large diesel engines onboard ships, more specifically removal of hazardous gasses such as nitrogen oxide and nitrogen dioxide otherwise known as NOx. These can be removed by a technology called Selective Catalytic Reduction (SCR) using a vanadium-based catalyst. SCR is a well-known technology which has been used for many years to remove NOx from incinerators and large chemical plants, such as oil refineries and cement plants. The novelty of using SCR onboard ships is that the catalytic reactor must be placed upstream of the turbo charger of the large two-stroke engines in order to reach sufficient temperatures, due to the high concentrations of SOx present in marine exhaust gas. This placement of the reactor also leads to an increased pressure, up to five bar, which had an unknown effect on the chemistry behind SCR.

What did you discover during your research?
Using commercial available catalysts at a pressure of up to five bar, we were able to measure that the reactions removing NOx weren’t affected by the increased pressure when the residence time was kept constant. This means that previous determined kinetics, measured at atmospheric pressure, are applicable up to five bar. At a ship, where the residence time is not constant, increased pressure will result in increasing residence time in the catalyst, which in turn leads to an increased NOx removal at increased pressure.

What are the possible wider implications of your research for society?
All ships build after 1 January, 2016, must comply with new regulations and emit 80% less NOx compared to earlier legislation (2000). This requires a safe and stable solution, and the SCR technology is one of such, so hopefully our research can lead the way for a greener marine industry and thus a greener environment.

What made you choose applying for a PhD position at DTU Chemical Engineering?
I’ve obtained both my Bachelor’s and Master’s Degree at DTU, and the latter was in collaboration with Anker Degn Jensen and Brian Brun Hansen here at DTU Chemical Engineering with focus on SCR in cars. I was happy about the process, working environment and guidance throughout my Master’s, so when I found out that Anker and Brian were looking for a PhD-student to study SCR for ships it was only natural for me to apply.

What does the future hold for you?
After finishing my PhD, I wanted to try life ”on the other side” and therefore I have started working in the private sector. I work as a research engineer at Umicore Denmark, in their department for stationary DeNOx, where I will continue to do research in SCR-catalysts. Umicore Denmark were also partnering in my PhD and it’s their catalysts that I have been doing researching on the last few years, so it’s nice to continue and improve the knowledge I obtained during my PhD.