Performance evaluation of a new conceptual combustion air preheating system in a 1000 MW coal-fueled power plant

Abstract

An innovative design of combustion air preheating for large-scale coal-fueled power plants was proposed. Differing from the conventional air preheating system using a rotary regenerative air preheater, a cascade heating concept is adopted in the new configuration, where the air obtains heat from the feedwater, circulating water and flue gas in several tubular heat exchangers, which significantly diminishes the air leakages and the exergy destruction. The results of a detailed thermodynamic analysis show that, for a typical 1000 MW coal-fueled power plant, the net thermal efficiency increment can reach 0.49% points with a net heat rate reduction of 86.77 kJ/kWh, if the novel air preheating design is adopted instead of the conventional one. This is because the exergy efficiency of the air preheating process is promoted from 77.88% to 91.77% owing to the proposal, and the total exergy efficiency of the power plant rises by 0.48% points. The economic performance of the new design was examined as well, indicating that the dynamic payback period is only 5.30 years when the proposed air preheating system is employed to replace the conventional one. This work may be beneficial for enhancing the air preheating system and advancing coal-fired power production.