Study On Key Technology Of Pipe Blowing Of 1000MW Ultra-supercritical Double Reheat Boiler

This paper summarizes the research and analysis of the conventional pipe blowing methods used in conventional 1000MW units.In this paper,No.6 and No.7 reheat super-supercritical units of Laiwu power plant was taken as object of study.To ensure the cleanliness of the heating surface and pipe system and to ensure the long-term stable operation of unit,acceptance criteria of steam blowing was established on the basis of the traditional method of "one-stage blowing,two-stage blowing",which can provide reference for other double reheat unit.This project proposed and validated the "three phase step-down method" steam blowing process,which is well adapted to the changes of new technologies.The quality control of the pipe blowing is strictly implemented in accordance with the relevant requirements of "Guidelines for Steam Blowing of Thermal Power Generation and Construction Engineering Units"(DL/T 1269-2013).The material of target plate used in this project is aluminum.The target plate dimensions are as follows:the width of the target plate is 8%of the inner diameter of the pipe and not less than 25 mm,the length of the plate is the inner diameter of the pipe,and the diameter of the purge pipe temporarily installed is larger than the formal pipe diameter.In the progress,the blowing coefficient is greater than 1,the maximurm particle size of the impact marks on the two consecutive blowpipe targets is no more than 0.8mm,and the number of the impact spots whose particle size ranging from 0.2 to 0.8mm is no more than 8.The relevant superheater,reheater and secondary reheater were respectively inspected for two times continuous,and the number and size of the target particles need to met the requirements of the "Compulsory Provisions of the Project Construction".The final test results show that the maximum number of spots after target shooting were 5 and 3,and all particle size is less than 0.8mm,which proves the excellent quality of pipe blowing.This study is an important issue for the commissioning of 1000MW ultra-supercritical secondary reheating units,which is set up in combination with the construction and commissioning of the first ultra-supercritical once-through 1000MW unit in China.It is of great significance to ensure the smooth operation of the first 1000MW ultra-supercritical once-through reheating unit,and to explore the pattern ofsteam blowing of the double reheat unit for ensuring normal operation.