Title: Improving energy efficiency in secondary aluminum melting furnaces through waste heat recovery
Event Subject: Approximately 80% of aluminum production in the United States uses the secondary process, which recycles scrap metal, instead of the primary ore refining process. The melting step is most energy-intensive, requiring temperatures of over 700°C and accounting for nearly 50% of total energy (natural gas) usage. Waste heat recovery technologies present an opportunity to enhance process efficiency by capturing energy from flue gas instead of rejecting it to the ambient. Two stages of waste heat recovery can be implemented for aluminum melting furnaces: (i) a high-temperature heat exchanger (400–900°C) located directly downstream of the melting furnace, and (ii) a medium-temperature recovery system (100–300°C) located further downstream. The first part of this study investigates the performance of two different high-temperature heat exchangers (recuperator and regenerator) for preheating combustion air. For this, an effectiveness – NTU method was used to analyze performance and to monitor the degradation of a recuperator over one year of operation. A one-dimensional, two-phase numerical model was developed to represent heat transfer and air flow through a packed-bed regenerative burner subject to clogging of the media particles (degradation). A parametric study was performed to examine the effect of key inputs (bed porosity, air flow rate, particle size, etc.) on the heat recovery performance over time. Both models were compared and validated with facility-specific data from secondary aluminum melting furnaces.
The second part of this study explores the use of medium-temperature recovery technologies, including for on-site power generation, load-preheating, and thermal energy storage. Specifically, Organic Rankine Cycles, Kalina Cycles, and waste heat boilers were evaluated for power generation. In addition, the use of sensible thermal storage (1D packed bed) was analyzed for offsetting load-preheating demands. Overall, this work provides recommendations for improving existing heat recovery technologies and adopting new practices for enhancing energy efficiency in secondary aluminum melting furnaces.

When: Monday, November 24, 2025 at 1:00 PM
Where: MARC Building, Room GTMI 114