Blast furnace 9 at thyssenkrupp in Duisburg-Hamborn has routinely been fitted with a new bell-less blast furnace top to ensure its continued alignment with strict environmental protection and occupational safety requirements. It weighs 27.8 tons, looks like an Apollo space capsule and distributes material evenly in the blast furnace. The replacement took place just in time for the technology's 50th birthday. The rotating gear unit, which is part of most modern blast furnaces, was developed by the Paul Wurth company in 1972. Blast furnace 4, which has since been shut down, was the first blast furnace to be equipped with this technology. At that time, the blast furnace set new standards for environmental friendliness and efficiency. The increase in output enabled by the new technology was coupled with a reduction in carbon emissions and blast furnace gas emissions.
50 Years of Reliability
The purpose of the bell-less blast furnace top, sitting on top of the blast furnace, is to distribute the charge materials needed for the blast furnace process, such as coke, iron ore and aggregates, using its rotary gear. In this process, the charge materials fall from material bins through a downpipe onto a rotating distribution chute with a length of three meters. The chute distributes the material onto the burden surface at a speed of 7.5 seconds per rotation. The bell-less blast furnace top works much like a sluice, in that it closes one "door" before opening another. These "doors" close very tightly, so that much higher pressures than in the old double-bell type gasket closures, which were used until 1972, can be achieved.
Although the technology is 50 years old, it meets the requirements of modern blast furnaces due to constant updates with automation and electrical sensor technology. The blast furnace top that has now been replaced ran almost incident-free at blast furnace 9 despite extreme loads. Every day, the rotary gear distributes 10,000 tons of material and every hour, around 3,000 cubic meters of nitrogen pass through the casing for cooling.
Investments in Environmental Protection and Occupational Safety
The blast furnace top on blast furnace 9 had to be replaced to prevent a possible break in the rotary gearbox which could have caused a shutdown of the unit. In addition, all blast furnaces must meet strict environmental protection and occupational safety requirements.
Regular maintenance and modernization are necessary at the "old" units to uphold their pig iron production and maximum performance. "We are continuing investments to keep our blast furnaces running efficiently. This is because we have to use the existing technology to finance the switch to climate-neutral steel production," says Hamborn blast furnace plant manager Volker van Outvorst. The new generation of gear units, which will be installed in blast furnace 8 this year, is cooled with water instead of nitrogen. This reduces noise emissions and is both more environmentally friendly and cost-effective.
Further Maintenance Scheduled
This year, the rotary gearbox on blast furnace 8 will also be replaced. Changing the bell-less blast furnace top, which has to be placed on the blast furnace by crane, is always a race against time. The blast furnace can be shut down for exactly eight days, or 192 hours, before it must be put back into operation. "In this process, mistakes are fatal. It's comparable to an airplane: once it's taking off, there's no turning back," van Outvorst explains. The blast furnace operations team has already successfully mastered this challenge at blast furnace 9.