Potential waste heat recovery analysis from molten steel slag: The case study of sidenor steelworks in Basauri (Spain)

Every day huge amount of energy is released to the atmosphere in form of waste heat. The search of a cleaner and more efficient society, not only at industrial level but also at domestic level, should avoid this type of emissions. Steelmaking is an example of an industrial sector with high optimization potential in energy management. In this line, this work presents the main outcomes of the investigation carried out in the search of a technical solution for heat capture and reutilization from one of the main waste heat streams in the steelworks, the molten slag. For this purpose, a piping system embedded in the slag pit soil is proposed as satisfactory solution for the heat capture operation. Besides, the internal applicability of this recovered heat is also addressed. Overall, the analysis carried out allows the identification of the main process parameters that limit the heat recovery potential from the molten slag. At the same time, the investigation provides accurate results of the maximum energy that can be recovered from the slag if the proposed technology is implemented (around 306 kWht per casting, what represents the 6.3% of the total available energy). The work is completed with a preliminary techno-economic analysis to conclude with the viability assessment. This analysis shows a depreciated payback period of the proposed technology below 7 years.