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Products and solutions, 2012-05-25, 11:00 AM

Dortmund continuous annealing line: ThyssenKrupp Steel Europe invests in environmental protection

ThyssenKrupp Steel Europe AG has modernized the continuous annealing line at its Dortmund site. Thanks to investment of around 30 million euros, nitrogen oxide emissions from the line will be reduced by half, further improving the environmental situation around the site.

When steel is rolled into thin strip at high pressure it hardens and without further treatment cannot be formed into car parts, computer cases, construction elements and the like. In the continuous annealing line the steel is heated to up to 835 degrees to reverse the hardening effect. The steel strip passes through the roughly 300 meter long line at a speed of up to 300 meters a minute.

The Dortmund continuous annealing line processes steel from the coupled pickling-tandem cold rolling mill at the site and supplies it to the two electrolytic galvanizing lines on the site of the former Westfalenhütte mill. Built between 1984 and 1986 the line has a capacity of 60,000 tons per month. Among other grades, it processes so-called bake-hardening and advanced high-strength steels for the auto industry. They reduce the weight of car parts and so cut fuel consumption and carbon dioxide emissions (CO2).

The steel is annealed in eight heating zones, each fitted with 40 to 60 burners supplying the required temperatures. The burners work in a similar way to heating pipes: An air-gas mix burns inside them, heating the ambient air in the heating zones. Udo Zocher, responsible for the modernization project at ThyssenKrupp Steel Europe: “We have replaced the heating equipment with new state-of-the-art burners.” Thanks to the new technology the air-gas mix burns with practically no residues. In addition the burners can be switched on and off individually as required, so the continuous annealing line always receives the optimum amount of energy. A likewise completely new control and automation system ensures extreme precision in the annealing process.

A further environmental benefit is that the burners also work with the coke oven gas that ThyssenKrupp Steel recycles as an energy source for the continuous annealing line. The gas comes part-cleaned from the Prosper coke plant in Bottrop, where it is generated during the production of coke from coal. If there were no user for it, the coke oven gas would have to be flared off. Udo Zocher: “Instead, use of the gas in the continuous annealing line conserves natural resources such as natural gas.” The new burner technology was developed specifically for use in the Dortmund continuous annealing line and the additional benefit for the environment.

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