Technical Focus on DC-arc Furnace Application to Waste Stream Smelting

The application of DC-arc furnaces to the production of commodities such as ferrochrome, ilmenite and smelting of stainless-steel plant waste streams has progressed substantially over the last 30 years. The DC-arc furnace remains a suitable smelting unit for both consumer- & other steel plant waste products and will play a potentially significant role in the development of a circular economy. With increasing environmental legislation requirements and the associated treatment and disposal cost of consumer-, steel plant and smelter waste products, processing of these waste products is increasingly becoming more economically viable, yielding a strong business case and an overall positive environmental impact. The waste products such as spent catalysts, mill scales, steel fines and bag filter dusts often contain valuable elements and various processing routes exist to treat these waste products. The DC-arc furnace is a well-suited furnace application due to its ability to process fine materials and yield products with a higher economical value, without the need of feed-material agglomeration or high-end reductants. Inherently, the process behaviour of these furnaces is dynamic where strict metallurgical process control principles must be applied by the process team to keep the metallurgical condition of the furnace within its operational boundaries. In addition, a number of furnace design aspects further influence the control measures available to the team. This paper will focus on the application of DC-arc furnaces for fine waste stream processing, focussing on a stainless-steel waste sludge case study, with a technical focus on the inherent characteristics and design requirements of these furnaces, required to achieve a stable furnace operation.