THE THERMAL STATE NUMERICAL SIMULATION AND THE SECURITY ANALYSIS TO THE SUPERHEATERS OF THE ULTRA-SUPERCRITICAL BOILER IN FCB

摘要

A successful FCB(Fast Cut Back)can increase the security of the power plant and electric grid. On the other hand, in ultra-supercritical boilers, the superheaters suffer higher temperature, higher stress and severer oxidation on steam side .In this article, a numerical simulation on the temperature and stress of the superheaters,considering the double oxide scale on steam side, respectively in the process of 100%,50% FCB (Fast Cut Back )and 100% ,75%, 50% load shedding, is conducted. The change law of the operation state is discussed. The results show that the higher the load before the operation condition change is, the greater range temperature and stress of the scale changes in, and the stress of the scale is affected by the steam temperature and steam pressure at the same time. The highest equivalent strain appears on the interface of the double scale, and its value is close to the spalling value. The oxide scale on the steam side of superheaters has high potential risk of spalling, great attention should be paid to them.