How AM can reduce NOx emissions by optimizing standard gas burners

Kueppers Solutions is a German company that specializes in redesigning energy-efficient products and optimizing current thermal process plants by replacing fossil fuels where possible or reducing their emissions with more efficient technologies. As anyone can imagine, AM plays a major role in redesigning components. Kueppers works with GKN as a partner for its AM activities, which have recently focused on reducing NOx emissions from thermal power plants.

In a project involving the Institute for Technical Combustion at RWTH Aachen University, the Gas and Heat Institute in Essen, the Chair for Energy Systems and Energy Process Technology at the Ruhr University in Bochum and the Chair for “Digital Additive Production DAP” at RWTH Aachen University, Kueppers and partners worked to develop a new mixing unit for gas burners that can significantly reduce nitrogen oxide emissions. The innovative geometry of the mixing unit was of course manufactured using 3D printing to create a precisely dosed gas-air mixture that burns better.

Nitrogen oxides (NOx) are a family of poisonous, highly reactive gases. These gases form when fuel is burned at high temperatures. NOx pollution is emitted by automobiles, trucks and various non-road vehicles (e.g., construction equipment, boats, etc.) as well as industrial sources such as power plants, industrial boilers, cement kilns, and turbines. NOx is a strong oxidizing agent and plays a major role in the atmospheric reactions with volatile organic compounds (VOC) that produce ozone (smog) on hot summer days.

In tests with the Gas and Heating Institute in Essen, Kueppers has proven that it is possible to build burners with this mixing unit that, at 30 mg/Nm3, which is below the currently applicable limit value by a factor of 10 and more.

This effect has a particularly positive effect on termoprocessing systems with high exhaust gas temperatures: here, the combustion air is preheated by heat exchangers with the energy of the exhaust gas. This allows the energy consumption of such systems to be reduced significantly. However, the nitrogen oxides rise sharply due to the preheating of the combustion air. Therefore, the energy of the exhaust gas is often not used or only insufficiently used, although this measure could significantly improve the efficiency of the system.

Kueppers commissioned the first reference systems at the beginning of 2019. However,  in order to reach the giant global gas market, Kueppers partnered with Gelsenwasser AG and Stadtwerke Bochum, both regional gas suppliers. The common goal is to also deliver the newly developed mixing unit as a component to other burner manufacturers.

This means that the technology can be used more quickly and across the board. Kueppers vision is to become a supplier, comparable to a manufacturer of injection systems in the automotive industry. In order to significantly reduce nitrogen oxide emissions, thousands of industrial burners have to be retrofitted.

In the area of ​​industrial burners, certain dimensions and sizes have become established across manufacturers. Comparable to replacing a light bulb with an energy-saving lamp, many burners on existing systems could therefore be replaced without the entire system having to be renewed. Since thermal processing systems are used for 30 to 50 years, this option is particularly important.