600MW直接空冷机组锅炉后屏过热器爆管原因分析

Cause Analysis on Back Screen Superheater Pipe-broken of 600 MW Direct Air-cooling Unit

某电厂2×600 MW直接空冷机组在2次启动后均发生锅炉后屏过热器泄漏爆管事故。对爆管特征及管道内部进行检查分析,认为爆管与运行操作、参数控制等有关。过热器U形管内形成水塞,过热器管束内介质停滞,从而导致过热器短期超温爆管。提出在锅炉启动初期利用高、低旁路进行吹扫,利用压差带出受热面积水,适当延长低负荷向高负荷的过渡时间,机组启动过程中加强壁温监视,完善热工逻辑等措施,同时对锅炉启、停操作进行细化,以防止同类爆管事故的发生。

This article researched on two screen superheater leakage incidents, which happened when the 600 MW subcritical coal-fired boiler restarted. Based on analysis of the tube characteristics, test results and the inside inspection of the pipes, the pipe-broken was related with improper operation and parameter control, which resulted in the u-shape tubes of the superheater accumulated in water, caused medium stagnation in the superheater tubes, and the superheater tubes leaked originated from short-term overtemperature. Put forward at the beginning of the boiler start-up, to purge with high and low bypass, and to take out of the heating surface water with differential pressure; appropriately extend the transition time from low load to high load; strengthen the wall temperature monitoring and improve the thermal logic measures to prevent similar pipe explosion accidents.