100 days downtime drastically reduced

Blast furnace A back in operation after just 89 days

The relining was expected to take one hundred days, with a further ten days scheduled for blowing-in and starting up the blast furnace. However, thanks to the outstanding commitment and diligence of all those involved - and flawless coordination - the new blast furnace A was re-commissioned three weeks ahead of schedule.

Anyone passing along Werkstrasse at Salzgitter Flachstahl between blast furnace A and the power plant in May of this year would have been able to witness a new, lower furnace in the making. Staff from Pirson Montage were working directly in front of the old blast furnace and welding together the up to 70-millimeter thick annular metal rings from Ilsenburger Grobblech; Danieli Corus was selected as the main contractor for the relining project.

Technology and logistics challenges

The old furnace hearth was dismantled before the actual relining work.
The furnace was tapped via a low borehole and the residual “furnace sow” – some 160 tons of pig iron – was flushed out.

Due to the scale of the project and the huge masses it involved, assembling the hearth posed a particular technical challenge. The furnace shaft, weighing in at 860 tons, was suspended from steel scaffolding and secured in order to separate it from the lower furnace.
It was replaced with the new furnace hearth that weighed 1,080 tons when ready to assemble, namely without the refractory material inside. A special device was used to position the new hearth on the foundation of the furnace, which had also been renewed and lowered. To improve the airflow, the hearth is now positioned higher than before. Working a good 18 meters above ground, the engineers welded the new hearth to the existing furnace shaft.

Relining and modernization in one step

When relining the furnace shell with refractory carbon bricks, Salzgitter Flachstahl took the opportunity to update the entire blast furnace so that it meets the current state of the art. This guarantees that the furnace will operate as efficiently as possible in the future.

Some examples: virtually maintenance-free, closed cassettes have now replaced the open-hearth irrigation system. Various components were replaced either in full or in part, including the gas cleanup and hot blast system, heat recovery, supply lines and the electrical equipment. The entire blast furnace, including the control technology with process visualization, now meets the current state of the art. A blast furnace campaign of fifteen years now appears realistic.

Changes have also been made to the area around the blast furnace: the new slag channels have already been laid for the granulation plant that is currently under construction; in future, the blast furnace sand for the cement industry will be produced here. The foundry was also modernized during the course of the relining work.