Steelwork: Tapping of a blast furnace

On the recording one can hear the work process of a blast furnace (year of construction 1963, modernized in 2013) at Thyssen-Krupp Steelworks being tapped.
In the blast furnace, liquid pig iron is produced from processed iron ores in a continual smelting process. The blast furnace generates heat of over 2000 degrees Celsius in order to melt iron from the iron ore.
To reach this temperature, coke is used as fuel and the fire inside the furnace is fanned with hot air at 1400 degrees Celsius. Also, limestone is added for the purpose of bonding impurities. The blast furnace is filled from above in order to build alternating layers of coke and iron ore. The part deeper in the furnace has the highest temperature. The molten iron flows to the bottom with the slag floating on top.
Every two hours the blast furnace is tapped: a tap hole is bored by means of a large drill. Out of it flow both the slag and the glowing yellow molten pig iron at approximately 1500 °C. When the outflow changes to slag only, the hole is closed up again by use of a mudgun. The blast furnace produces a total of 13,000 tons of pig iron a day.
The venting of the blast furnace can be heard continually throughout the tapping process: the gas streaming in and the venting by means of large exhaust systems dominate the sound environment of the tapping stand. When the tapping takes place the drill can be heard clearly. Furthermore, diverse acoustical signals coordinate the tapping process - the starting of every machine is announced by a different signal. The signals are managed by a computer-operated control system and sounded by signal devices.
After tapping, the pig iron is transported to the hot rolling mill where it is processed into steel which is resistant to rust, acid and heat. In the cold rolling mill it is then shaped into further forms.

Sound recordist: Konrad Gutkowski / Marie-Claire Fink
Video recordist: Konrad Gutkowski / Marie-Claire Fink
Photographer: Konrad Gutkowski / Marie-Claire Fink