The Analysis And Reconstruction Of Drum Metal Temperature In The Process Of Boiler Start-up

In the process of start-stop and rapid load changes of the thermal power unit, boiler drum, separators, mix heaters headers and other high temperature and high pressure thick wall components will have great thermal stresses. The existence of thermal stress directly affects the safety and shortens the service life of thermal equipment. Effective monitoring the thick wall metal temperature field of high temperature pressure components has very important significance for improving the safety and economics of thermal power units.In this paper, a 600 MW pulverized coal-fired subcritical natural circulation drum boiler is taken as the object. The research on the transient temperature distribution of the drum and the reconstruction of drum metal temperature field during startup are done. The main works include:①The two-dimensional unsteady heat transfer model of the drum is established. The transient temperature field of drum metal is simulated numerically by the finite element method(FEM).② Combined with the unit reference starting curve, the transient temperature fields of drum metal during the cool start-up, warm start-up,hot start-up and extreme hot start-up are calculated. The impacts of different start-up conditions on the transient temperature field of drum metal are analyzed.③A temperature reconstruction method of drum metal is established based on inverse heat transfer problem(IHTP). According to temperature measurement information of drum metal wall, using sequential function specification method achieves the inversion solution of drum internal heat load and the reconstruction of the transient temperature field of drum metal.④The transient temperature fields of four kinds of typical start-up conditions of drum metal are reconstructed, and the effects of the future time steps and temperature measuring errors on the reconstruction results of the transient temperature field of drum metal are discussed. The feasibility of using the inverse heat transfer problem method to realize transient temperature field of drum on-line monitoring is verified preliminarily.⑤This article discusses how to choose future time steps at process of using SFSM to realize the inversion solution of drum internal heat load. Based on principle of residual, an optimization method for the future time steps is established. The numerical results shows that if the future time step is chosen properly based on the measurement errors, this method can improve the reconstruction results of transient temperature field of the drum metal effectively.