The Research Of Calculating Method About Life Consumption Of Power Plant Boiler Superheater Tubes With The Deposition Of Oxide Scale

Because supercritical boilers have more fuel efficiency of than conventional boilers, various countries.consider the supercritical technology is the solution of energy shortage. At present, the main steam temperature of supercritical boilers is developing from600℃to700℃. Austenitic stainless steel has fine high temperature performance, as for it is the most common material of superheater whose environmental condition is poor. But austenitic steel tube will occur high temperature oxidation corrosion and the inner wall will generate oxide scales if it has worked for long time with superheated steam. The heat expansion coefficient between oxide scales and matrix is different, therefore the oxide scales exfoliate easily to deposit in the tube. In this situation, normal heat transfer is affected that probably lead to tube explosion.Through the corresponding means to detect oxide scales are developed, there is no health assessment abou the tube with oxide scales,the field staff only choose to replace with new tube.In this paper, the following research is completed. (1) According to revelant design standards, operation maintenance rules and accident cases, the superheater’s failure tree whose top event is fracture failure is constructed by FTA. The main factors which cause superheater’s accident are reflected directly and precautionary measures are proposed.(2)By FEM, the effect of the oxide scales to tube heat transfer is calculated with actual parameter. The rapid calculation procedure of wall temprature under the deposition of oxide scales is programmed by APDL and VB language. The result indicate that the oxide scales can cause wall temperature rise seriously.(3)Through different TTP, life curves of several kinds of laustenitic steel under a confidence level are deduced. By the contrast of two theories, the minor of calculated result is considered as the material life. On the basis of the life consumption rule, the dangerous status of superheater tubes is defined for three levels, the program of the life consumption fraction is completed.The conclusion of this paper would provide foundation for detecting oxide scales and choosing treatment scheme.