Küttner GmbH & Co. KG

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BOF Steelmaking

Around the Basic Oxygen Furnace (BOF), Küttner provides a variety of products and technologies:

BOF bottom stirring (TBM – ThyssenKrupp Blowing Metallurgy)
Inert gases like nitrogen and argon are blown through tuyeres in the bottom of the converter to improve the mixing between metal and slag. This stirring shifts the oxygen blowing process closer towards the metallurgical equilibrium conditions which opens a variety of benefits like reduced dissolved oxygen in steel, reduced oxidation of steel, increased yield, reduced blowing time, etc.

Sublance systems
Sublance systems are mechanical lance systems which are used to provide two different measurements during and after the blowing process. The first measurement (TSC) per heat is typically the in-blow measurement which provides the actual bath temperature and carbon content as well as a sample at approximately 2 min before the expected end of the blow. The second measurement (TSO) is executed immediately after end of blow and provides the final temperature, the final carbon content, the dissolved oxygen content as well as a sample and the bath level.

Drop/bomb sensor systems
Compared to sublance systems, drop or bomb sensor systems are a low-cost alternative whoch are basically providing the same measurements. Probes are released to fall into the converter by gravity. Due to the fact that these probes cannot be retracted, it is not possible to receive a sample or to perform a bath level measurement.

Off-gas analysis systems
The off-gas generated in the converter contains relevant information about the actual carbon content of the bath during the final blowing phase as well as some other valuable information. Off-gas is extracted from the main duct of the primary dedusting system, cleaned, cooled and analysed by means of a mass spectrometer or conventional gas analysers. The so measured composition of the off-gas is used in a metallurgical process model to calculate several key figures describing the final blowing phase. This information is then used for BOF endpoint control.

BOF Level-1 automation
A high degree of level-1 automation with PLCs and related smart controls and instruments is essential for a successful usage of level-2 process models as well as a highly reliable, reproducible and automatic blowing process.

BOF Level-2 process models
Küttner’s BOF Level-2 process models family is named OTCBM (Optimized ThyssenKrupp Converter Blowing Models). Starting with a basic package, OTCBM can be scaled up to a complete high-end “automatic BOF steelmaking” package. Static charge calculations, material and heat balances, automatic lance pattern, etc. are only some of the features.

BOF Endpoint control systems
The dynamic BOF endpoint control system provides a temperature and a carbon prediction based on available measurement results from a sublance system, a drop/bomb sensor system, or an off-gas analyzer. The predicted figures for blow end are used to adjust the carbon-temperature trajectory in order to achieve aimed at end of blow without reblow or any other correctional measures and thus allow direct tapping.