Heat balance study in a walking hearth reheat furnace

The aim of this study was to develop and validate a comprehensive heat balance model for reheat furnaces to quantify energy distribution and identify opportunities for minimising heat loss in secondary steelmaking operations. While reheat furnaces account for approximately 70% of energy consumption in secondary steelmaking, limited quantitative analysis exists on the distribution of heat losses across different operational parameters. A heat balance model was developed based on an assigned control volume approach, incorporating radiation and convection equations to quantify heat distribution. The model was validated using operational data from Infrabuild' Laverton steel mill at discharge rates of 86 tph and 92 tph, with temperature measurements used to calibrate the heat transfer calculations. Results showed that flue gas losses represented the highest contribution to total heat loss at 25%, while surface losses accounted for 17% of total energy output. Heat loss beneath the hearth emerged as the dominant component of surface losses, with temperatures reaching up to 500°C. The validated model demonstrates that surface heat losses are more significant than previously quantified, suggesting that improvements in thermal insulation beneath the hearth could yield substantial energy savings. This study provides steel manufacturers with quantitative data to prioritise energy efficiency improvements in reheat furnace operations.