An improved waste heat recovery system integrated with the bypass flue and heat pump air preheater for coal-fired power plants

Abstract Flue gas waste heat recovery technology achieves substantial reductions in coal consumption, decreases carbon emissions, and offers favorable economic returns. However, typical systems using low-temperature economizers to heat air, with flue gas at around 100 °C and air at approximately 20 °C, still suffer from significant irreversible losses. To tackle this challenge, this work developed an improved waste heat recovery solution combining a bypass flue with a heat pump air preheater for a coal-based power plant. We evaluated the comprehensive technical and economic behavior of the improved system, optimizing the key parameters to achieve peak profitability. Thermal analysis reveals the system achieves an impressive 91.3% exergy efficiency while cutting coal usage by 5.3 g/(kWh) when the optimal design parameter is implemented. Economic analysis indicates that the power plant’s net present value achieves 15.3 million dollars over a decade, with a discounted payback period of a mere 0.92 years. This advanced recovery system demonstrates significant potential to boost both energy efficiency and financial returns for conventional power plants.