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Technical Paper
Figure 3: Hearth walls – thermocouples instrumentation (ArcelorMittal) respectively for a) Dunkerque BF n°4 and b) Fos-sur-Mer BF n°1 and n°2
the very first barrier against corrosive agents, the wear evolution of this layer will be investigated in detail in this paper.
• A specific concrete refractory used between the ceramic and the carbon layer.
• The carbon lining generally composed of large blocks. It is normally characterized by a high thermal conductivity and low pore size diameter. Its role is to keep the inner wall at a low temperature and to prevent any liquid iron from reaching the shell. As the carbon saturation of pig iron cannot always be guaranteed, it is important to lower the contact between the carbon and the liquid metal to avoid rapid carbon loss by promotion of a stable protection layer which is difficult.
• The ramming mix installed between the steel shell and the carbon walls used for both to reduce the global thermo-mechanical stress after blow-in stage and to ensure a good thermal contact between the steel shell and the carbon.
- The external steel shell of the blast furnace. Monitoring of temperature and data analysis
Today, the best way to monitor the wear inside the BF is via well placed thermocouples using a modern software programme. It is important that the programme is “on-line” and calibrated before BF blow-in prior to any wear taking place thereby giving high confidence in the results. Each hearth lining is equipped with thermocouples to monitor the temperature profile inside the hearth layers during the entire BF campaign. The permanently installed thermocouples are directly set-up inside the refractory lining in precise locations to record constantly the local temperature.
These probes are located all around the circumferential lining and their position (x = radial position, y = BF elevation), and number are specific to each blast furnace (Figure 3).
The software program (Mothus) has been developed by ArcelorMittal in recent years to model the wear profile with now a very good accuracy between real/theoretical data [7]. For Thyssen, similar software named “Thybas” is used to monitor hearth wear. Based on this data over the years, we have access to the wear evolution profile of the hearth lining.
For example, thanks to this methodology, ArcelorMittal regularly report internally the actual “age” of the full BF taking into account the calculated
July 2017 Issue
ENGINEER THE REFRACTORIES
21
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