Fatigue lifetime assessment on a high-pressure heater in supercritical coalfired power plants during transient processes of operational flexibility regulation

The operational flexibility of coal-fired power plants has become a priority objective; however, the lifetime main devices is reduced due to thermomechanical fatigue during transient processes. This study focuses on t safety of high-pressure heaters at operational flexibility measures. The dynamic characteristics of therrr parameters in the 1# HP heater were obtained and analyzed based on transient models of a coal-fired pow plant. The change trends of pressure/temperature on the steam/feedwater side of the 1# HP heater at thr throttling the extraction steam measures were different with that at the feedwatcr bypass measut Subsequently, finite element analysis method was used, and the thermomechanical stresses under the fo measures were calculated and analyzed. The time to reach the maximum mechanical stresses was shorter th, that of thermal stresses. Finally, the fatigue lifetimes of the heater were estimated. The maximum fatigue dama ratio at the per load cycle was 0.0069%, and the minimal allowable number of cycle was 14413 in the upp region of the tube sheet when the extraction steams of #1, #2, and 3# HP heaters are regulated simultaneous) The study could offer data guidance to the safety and maintenance of coal-fired power plants during operatior flexibility regulations.