ThyssenKrupp Nirosta completely modernized its converter facilities in Krefeld, Germany. The project was completed with the goal of lowering pollution in the area around the plant. The modernization featured the installation of two new AOD (argon oxygen decarburization) converters with change vessel and ancillary equipment. The converters allow dust arising during the production process to be retained in the filter system. The air is then extensively filtered before it is released back into the atmosphere. ThyssenKrupp Nirosta modernized the equipment in collaboration with plant engineering contractor Siemens VAI.

In the stainless steel industry, carbon-rich primary heats produced in an electric-arc furnace (EAF) are further processed in special converters such as the AOD. The molten metal from the EAF is poured into the converter, and oxygen or a mixture of oxygen and other gases such as nitrogen or argon are added. The undesirable carbon in the steel burns off in the converter and passes into the flue gas, while chromium remains in the molten metal. The carbon-rich flue gas is extracted and filtered.