PROJECT 3: Steel: materials transformation and the pressures of globalising markets
Producing steel via the BOS route (the technology typically used for large-scale production) initially requires smelting iron ore with limestone on a bed of coke in a blast furnace, tapping off the required liquid iron and separating it from the slag, the waste being produced at this stage. The liquid pig iron is then transferred to a BOS vessel, a charge of scrap steel (typically 30%) is added and an oxygen lance injected into the mixture to convert the iron to steel. This is then either cast in moulds, or more generally today, continuously cast into the required form of ‘semis’ prior to further rolling and processing into finished products. At each stage of the production process, waste materials are unavoidably produced, from slag in the blast furnace to off-cuts from continuous casting (which in turn can become part of the next scrap charge). At this stage, technological differences in the sophistication of rolling and finishing processes become important.
Steel production has largely remained organised within the framework of national (or European Union) markets. Indeed, it is only recently that Mittal has emerged as the first global steel producer, via an extensive series of acquisitions in Africa, the Americas, Asia and Europe. The technologies of iron and steel production are well known and can be considered to be ‘mature’, although there continue to be important innovations. However, there are intense – and intensifying – pressures to rescue waste and increase materials efficiencies in production. One example of this is slag splashing. First introduced at one of Mittal’s Chicago plants, slag splashing is diffusing through other production facilities in the group, via its global knowledge transfer programme. We propose focusing upon two integrated production plants within the Mittal group, one in Chicago, the other at Kalmeshwar near Mumbai.
© The Waste of the World 2009
