Volume 50

A Multifactorial Lifetime Estimation Method for Boiler Components of Coal-Fired Power Plant During Flexible Operations JunZheng Zhang, Lei Pan, Xiao Wu, JunLi Zhang

Abstract

Coal-fired power units may have safety risks during deep peak shaving and rapid load changing. Therefore, a comprehensive estimating method based on Finite Element Analysis (FEA) and boiler design rules is proposed in this study. Measured data is taken as the boundary conditions for FEA, and the time related restrictions from boiler design rules are used to calculate the primary stress, inelastic strain and creep-fatigue lifetime indicators. The header at the outlet of the final-stage superheater of a 350MW supercritical boiler is analyzed, and the results show that under operating conditions of cold start-up, up to 55% depth of peak shaving and up to 1.4%/min of load change, there is no risk of plastic collapse. Inelastic strain mainly accumulates during start-up process, rather than during peak shaving. Creep-fatigue damage mainly occurs around the fillets of the branch tubes. The fatigue damage is only 0.2% after 30 years operation, with no significant thermal fatigue. But the creep damage is excessive, exceeding the limit after operation of 300 days.

Keywords Coal-fired power plant, Flexible operation, Lifetime estimation, Finite element, Viscoplastic