In an effort to reduce their environmental footprint, ArcelorMittal sites across the globe are implementing environmental projects and initiatives, from recycling scrap to planting eucalyptus trees.
ArcelorMittal Flat Carbon Europe sites in Gent and Bremen are recovering and re-using their waste gases to reduce their emissions and energy costs. Their projects have been identified as best practices for the rest of the group to replicate.
Recovering energy rich flue gases in Gent, Belgium
ArcelorMittal Gent in Belgium produces steel using the blast furnace process. In that process, iron ore and coal (in the form of coke) are transformed into liquid pig iron. The pig iron contains 4.6% carbon, way above the 0.4% required for quality liquid steel. To remove the excess carbon, the pig iron is burnt with pure oxygen.
During the combustion process, a large amount of energy-rich flue gases are produced. Previously, Gent used to burn these gases off through a chimney. However, since July 2011, the site has been diverting the flue gases to a 90,000m3 reservoir.
Around half of the saved gas is used within the mill, while the remainder is sent to a local electricity generator. ArcelorMittal Gent estimates that this will reduce the mill’s overall energy consumption by 3% and cut CO2-equivalent emissions by 170,000 tonnes per year. Reusing the flue gases within the mill has helped reduce energy consumption by 0.7 gigajoules (GJ) per tonne of steel. While the cost of building the system was just over €38 million, ArcelorMittal calculates that this investment will be balanced out within two years.
Recycling converter gas in Bremen, Germany
ArcelorMittal Bremen in Germany has implemented a €41m project to recover energy, lower dust emissions and reduce nitrogen-oxide (NOx) emissions. The project is based on a newly built basic oxygen furnace (BOF) gas recovery facility and a convertor dedusting system.
The gas recovery facility will allow Bremen to reduce CO2-equivalent emissions by up to 270,000 tonnes per year. Around 80% of the recovered gas will be burnt in the walking beam furnaces of the hot strip mill, replacing the use of natural gas. The remaining recovered gas will be used in the mill’s power plant to generate electricity.
During renovations to implement the new systems, the burners of the walking beam furnaces were adapted to reduce nitrogen oxide (NOx) emissions by more than 25%. Along with lower dust emissions and the recovery of energy rich gases, this is the third green effect of this project.
http://www.arcelormittal.com/corp/news-and-media/news/2012/jun/20-06-2012