Siemens VAI Metals Technologies replaced two existing stationary AOD vessels and started up two new exchange-type AOD converters at the German stainless steel producer ThyssenKrupp Nirosta in Krefeld, including auxiliary equipment. All installation work up until the converter start-ups in the Spring of 2009 was carried out within only three weeks' time, minimizing production downtime. Following the fulfillment of the guarantee performance figures, the Final Acceptance Certificate was issued by the customer.
In the course of a modernization project at ThyssenKrupp Nirosta, the two existing stationary AOD converters were replaced by Siemens VAI with new exchangeable AOD converters. The produced steel grades comprise mostly high-quality austenitic chromium-nickel grades used for a wide range of flat-steel applications. The project scope comprised the complete dismantling of the existing vessels down to their foundations, installation of two new horse-shoe-type trunnion rings with tilting drives for the exchange-vessel system as well as the engineering, supply and installation of the new converters and related equipment. Siemens VAI also provided civil works, steel structure, charging bins, modifications to the existing alloy- and flux-feeding system, new process-gas regulation stations, new waste-gas hoods, a converter exchange car, the converter relining and wrecking stand with tilting device, two converter transfer cars, two converter-preheaters and one jib crane. Some of the existing equipment and interfaces with the new equipment had to be adapted.
The main control desk and the Level 1 automation system were modified to meet the new converter requirements. The electrical equipment was renewed or upgraded as required. The project scope was rounded off by personnel training for plant operation, refractory lining and maintenance of new plant equipment.
A particular challenge of this project was that the converters had be replaced with minimum interference to ongoing production operations and under extremely restricted space conditions. This necessitated parallel installation and start-up work with the highest priority placed on personnel safety. The challenge was met through the combined efforts of the start-up teams from ThyssenKrupp Nirosta and Siemens VAI. All onsite work activities for the two converter replacements were completed within only three weeks during an operational standstill. Full production capacity of the Converter Nos. 1 and 2 were attained within only six and three days after the respective converter start-ups. After completion of the required guarantee figures, Siemens VAI received the Final Acceptance Certificate from ThyssenKrupp Nirosta in May 2009.