Problem
New Zealand Steel operates two KOBM vessels in their steel production process. These vessels are loaded with molten metal and metal scraps, then heated to over 1,600°C. Inside, they contain refractory material designed to maintain manageable shell temperatures, supporting their contents and weight loads. However, over each operating campaign, this refractory slowly deteriorates until it reaches the safety liner. This deterioration leads to observed permanent deformation of the vessel, raising concerns about reliability and safety, including:

1. Inability to lift the vessel due to jamming

2. Shell bulging and cracking

3. Flange integrity

4. Creep rupture during operation

Solution
Finite element analysis (FEA) was conducted to assess creep damage during each campaign, factoring in refractory erosion. Due to the complexity of KOBM operating conditions, computational fluid dynamics (CFD) models were employed to analyse them, incorporating radiation and convection heat transfer. This comprehensive approach allowed accurate modeling of thermal loads on the vessel and provided deeper insight into the root cause of observed deformations.

Result
Advanced FEA and CFD modeling yielded understanding into the root cause of permanent deformations and shed light on how vessel operation, material selection, and refractory replacement impact the life of KOBM vessels. Furthermore, the comparison between deformation scans and finite element models revealed excellent agreement, enhancing the confidence in the accuracy of the analysis.