An inter-company approach to improve resource and energy efficiency and reduce greenhouse gas emissions in metal industries by linking flow sheet models

Regarding sustainability, one of the greatest advantages of metals is their possibility to be recycled generally without a loss of quality. At the same time, Germany depends on the import of most primary resources, has comparable high energy prices and is facing global competition. Also, the use of energy is often connected to emissions of greenhouse gases which are becoming another important cost driver. Thus, the German metal industry aims on enhancing resource and energy efficiency. As internal improvement potentials which are related to a single company or process plant are to a large extent exploited, future potentials can be found by an integrated consideration of internal and external recycling possibilities. This paper presents an approach in which companies are not considered isolated but as a network. Zinc is used to an increasing degree as coating of steel products. After utilisation these products are recycled. The production of steel in Electric Arc Furnaces (EAF) mostly bases on scrap as raw material. In the oxygen steel production approximately 20 % of the raw materials in the converter is scrap. Most of the zinc in the feed can be found in residues like EAF-dust. These dusts can be recycled to a certain degree internally and afterwards treated by specialised recycling companies.Thereby, we investigate which recycling rate is optimal considering the steelmaking and recycling process as well as transportation and further influencing parameters. Our approach comprises a combination of flow sheet simulation to achieve detailed models of the processes and the development of methods to investigate internal and external recycling options. We consider an integrated steel works, an EAF, two recycling companies as well as a hydrometallurgical zinc smelter.