Integrated Energy, Time, and Cost Savings Assessment of Steel Billet Thermal Management: A Numerical Approach for Enhanced Industrial Sustainability

Steel production involves energy-intensive thermal processes, where improvements in heat management can contribute to enhanced efficiency and reduced environmental impact. This study analyses the cooling and heating processes of steel billets in small-to-medium-sized steelworks, with the aim of identifying potential energy, time, and cost savings. Currently, billets leaving the casting process cool down freely in an open-air storage area from approximately their casting temperature to ambient conditions, and they are subsequently reheated to 1265 °C before rolling. A numerical model based on the finite difference alternating-direction implicit (ADI) method has been developed in MATLAB R 2025a to simulate these processes. The numerical implementation was verified against the analytical lumped-capacitance solution under the assumption of uniform billet temperature during slow cooling. For loading times of 15–30 min, the billets retained temperatures of 1112–806 °C after 15 days of insulated storage. Compared with reheating from 25 °C, the predicted heat savings were 672–936 MJ per billet, corresponding to fuel savings of 600–836 kWhLHV, gross fuel-cost savings of EUR 18–25 per billet, and reheating-time reductions of 17.7–33.3 min. An improvement scenario was then analysed, consisting of placing 36 billets from each casting batch into an insulated container to reduce heat losses after casting. The results show that with reasonably well-insulated containers, billet temperatures can be maintained above 800 °C for up to 15 days. This increase in the inlet temperature to the reheating furnace reduces both the required energy and processing time. These results suggest that relatively simple thermal management strategies can improve energy efficiency and reduce operational demand in steel production, supporting more sustainable industrial processes.