二次再热1000 MW燃煤机组(极)热态启动过程切缸与并缸故障分析及处理

Analysis and treatment of cylinder cutting and cylinder merging during(extremely)hot start-up in double-reheat 1000 MW coal-fired unit

对二次再热1000 MW燃煤机组在(极)热态启动时出现切缸及并缸时的典型故障进行了研究。详细分析了3次甩100%负荷及1次甩50%负荷后的4次(极)热态启动过程的主要参数变化,探讨了(极)热态启动过程切缸、2次并缸失败导致长甩负荷、并缸后再热器保护动作及切缸后成功并缸的4个故障实例。结果表明:3缸联合启动方式在(极)热态启动阶段容易造成超高压缸切缸;在并缸阶段,采用数字式电液调节系统中默认的Fastly速率释放超高压调节阀阀限,极易引起负荷超调、轴向位移突增,进而造成机组参数剧烈扰动、并缸失败,甚至长甩负荷;并缸成功后,应及时调整目标负荷,抑制总流量指令的突变;及时增加锅炉燃料、自动调整旁路调节阀开度和稳定机前压力是并缸后安全运行的关键。上述研究结果为机组(极)热态下安全、稳定及快速地启动提供了重要的参考。

The typical failures of cylinder cutting and cylinder merging in double-reheat 1000 MW coal-fired unit during(extremely)hot start-up are studied.The changes of main parameters during four(extremely)hot start-up processes are analyzed in detail,including 100%load rejection three times and 50%load rejection once.Four failure examples are discussed,namely the(extremely)hot start-up phase of the cylinder cutting,two failures of load rejection caused by cylinder merging,reheater protection trip after cylinder merging and the successful cylinder merging.The results show that,the three-cylinder combined start-up method is likely to cause the ultra-high pressure cylinder cutting during the(extremely)hot start-up.The use of Fastly rate in digital electrohydraulic control system to release the valve limit of ultra-high pressure regulating valve can easily cause load overshoot and sudden increase of the turbine axial displacement,which will cause severe disturbance of the unit parameters,failure of cylinder merging,and even load rejection.After successful cylinder merging,the target load should be adjusted in time to suppress the sudden change of the total flow command.Increasing boiler fuel in time and automatically adjusting the bypass opening to stabilize the main steam pressure is the key to safe operation after cylinders merging.The research results provide an important reference for the safe,stable and fast start-up of the unit in(extremely)hot state.