【Objective】The effective identification of irreversibility losses in the thermal systems of coal-fired power plants is important for improving energy efficiency and enhancing waste heat utilization. However, in practical operation, the distribution of irreversibility losses is difficult to determine accurately, and the utilization efficiency of waste heat is still relatively low. To address these problems, a waste heat potential evaluation method based on entropy generation and exergy loss analysis is proposed. The method aims to identify the weak links in the thermal system and provide a thermodynamic basis for waste heat utilization scheme selection. 

【Methods】A 660 MW coal-fired power unit and a 300 MW coal-fired power unit are selected as the research objects. Based on the Ebsilon Professional platform, thermal system models of the two units are established according to their heat balance diagrams and operating parameters. The models are verified by comparing the calculated extraction steam flow rates with the design values. Then, entropy generation analysis and exergy loss analysis are conducted for the main heat exchange equipment in the regenerative heating system. Combined with off-design condition analysis, the distribution of irreversibility losses and the potential for waste heat utilization are quantitatively evaluated. 

【Results】The results show that the irreversibility losses of the two units are mainly concentrated in the regenerative heating system. For the 660 MW unit, the main loss sources are the #2 and #3 high-pressure heaters and the #7 low-pressure heater. For the 300 MW unit, the main loss sources are the #2 high-pressure heater and the #7 low-pressure heater. The main reason is the large heat transfer temperature difference between steam and water, which increases heat transfer irreversibility and exergy loss. Based on these results, an energy cascade utilization scheme combining extraction steam preheating and flue gas waste heat utilization is proposed. The scheme improves the temperature matching relationship in the regenerative heating system and reduces irreversibility losses under different operating conditions. For the 660 MW unit, the maximum thermal efficiency improvement is 1.88%, and the maximum reduction in coal consumption rate is 2.50 g/(kW·h). For the 300 MW unit, the maximum thermal efficiency improvement is 0.47%, and the maximum reduction in coal consumption rate is 1.31 g/(kW·h). 

【Conclusion】The proposed method can effectively identify the main irreversibility loss sources in coal-fired power units and provide a thermodynamic basis for waste heat utilization scheme selection. The proposed scheme has good off-design adaptability and can provide guidance for waste heat potential exploration and system optimization in coal-fired power plants.