Conference article

The main part of the steel manufactures producing alloyed steel use scrap as an essential raw material. To increase the corrosion resistance of steel a coating is often applied. The share of steel being coated and galvanized is today globally increasing; which is resulting that the amount of scrap with different types of coatings are increasing. This result in that more of the scrap used in steel making is contaminated with for example Zinc and organics. Scrap preheating is a known method for reduction of energy use in steelmaking. However due to environmental restrictions a widespread implementation of scrap preheating have not been achieved in the steel industry. Combined surface cleaning and scrap preheating is a way to handle the problem that coatings give rise to in the melting cycle and is a new concept suggested and developed at Swerea MEFOS. The pre-treated scrap (cleaned and preheated) is charged hot into the oxygen converters with direct savings of energy; as the demand of hot metal from the blast furnace decreases. The method opens for the possibility to widen the scrap base and to melt complicated scrap. Since the preheating process is a standalone solution; a large number of unwanted chemical components are removed prior melting resulting in that the dust generated from the melting process is easier to recover. In this paper the system effect of introducing a preheating and surface cleaning process for scrap in a Blast Furnace (BF) and oxygen converter (BOF) steelmaking route is analyzed according to energy and CO2 emissions. The system analysis shows that surface cleaning of scrap makes it possible to use shredded scrap and ASR (automotive shredder residue) or other combustible waste to replace fossil fuels. The results from the analysis demonstrates that implementing surface cleaning leads to increased possibilities for recycling of otherwise non-recyclable material. The system model shows the interaction between different processes; which gives an overview picture including the whole steel making route. The model is used to investigate changes in process conditions from making use of shredded scrap and ASR as input material in the steel making process. The implementation of surface cleaning and preheating lead to both increased possibilities for recycling of scrap; and more efficient energy use in the steelmaking routes.

BOF; Scrap preheating; Surface cleaning; optimization; ASR