In the blast furnace of ArcelorMittal Gent (Belgium), 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, it is burnt with pure oxygen.
During the combustion process, a large amount of energy rich flue gases are produced. Previously these gases were burnt off at the top of a chimney. However, since July 2011, ArcelorMittal Gent has diverted the fl ue gases to a 90,000 m3 reservoir.
Around half of the saved gas is utilised 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 decrease CO2-eq emissions by 170,000 tonnes/year. Reusing the flue gases within the mill has resulted in a drop in energy consumption of 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 recovered within two years.