Industrial furnaces are the primary energy-consuming systems in industrial facilities. In factories that rely on these furnaces, energy costs are the largest expense after raw materials. To enhance fuel efficiency and reduce waste gas emissions, high-temperature annealing furnaces must be operated with maximum effectiveness. The increasing cost of energy has made waste heat recovery a crucial factor in industrial energy management. Waste heat recovery can be achieved through systems such as economizers, recuperators, and power cycles, including the organic Rankine cycle (ORC), Brayton cycle (BC), and Rankine cycle (RC). These technologies provide significant energy savings while supporting environmental sustainability. Effective selection and operation of these systems require identifying waste heat sources and conducting comprehensive energy and economic analyses. This study evaluates the energy performance of Brayton, combined Brayton–Rankine, and ORC cycles for power generation by utilizing waste flue gas from an industrial annealing furnace in a flat-rolled structural steel manufacturing facility. The thermal efficiency, net power output, and the reduction of CO2 (carbon dioxide) emissions into the atmosphere for each system were analysed. All calculations were conducted using the Engineering Equation Solver (EES) software. The findings indicated that the combined Brayton–Rankine power cycle, applied after the annealing furnace, demonstrated the highest efficiency and power output, achieving a thermal efficiency of 46.64%, a net power of 3524 kW, and a CO2 emission reduction of 3051 kg/h. When n-pentane, cyclohexane, and toluene were evaluated as working fluids in the ORC following the recuperator, cyclohexane was determined to be the most suitable option. Using cyclohexane as the working fluid in the after-recuperator ORC resulted in a thermal efficiency of 21.68%, a net power of 518.2 kW, and a CO2 emission reduction of 448.6 kg/h. The simple payback period for the ORCs after the annealing furnace’s recuperator was calculated to be 2.5 years. The findings of this study highlight that heat recovery can significantly reduce fossil fuel consumption in the energy-intensive iron and steel sector, leading to lower greenhouse gas emissions and helping to mitigate environmental pollution.