低加事故疏水调门LCV002异常开启分析

Analysis of the Abnormal Opening of the Emergency Drainage Control Valve LCV002 of Lower-Pressure Heater

火力发电厂的热力循环系统中,采用给水回热循环,从中间级引出部分做过功的蒸汽加热凝结水、给水,提高了热力系统的循环效率,减少循环产生的“冷源损失”。本文研究了某厂2#机组高负荷时,3#低加的水位开始上涨,3#低加事故疏水调门会开启,3#低加水位过高,其加热面会被淹没,与蒸汽的传热面积减小,传热效果下降,蒸汽不能及时凝结,同时事故疏水排入事故疏水灌,最终进入凝结器,增大了“冷源损失”,影响机组运行效率。3#低加水位高,可能会造成使3#及4#低加水位高跳闸,甚至使汽轮机进水,造成水冲击,威及设备安全稳定运行。

In the thermal cycle system of the thermal power plant,the feed water regenerative cycle is adopted.The steam which has done some work is drawn out from the intermediate stage to heat the condensate and feed water.The cycle efficiency of the thermal system is improved and the“cold source loss”caused by the cycle is reduced.When the No.2 unit of a power plant is under high load after the replacement of the electric pump with the steam pump,the water level of the No.3 low-pressure heater starts to rise,and the emergency drainage valve of the No.3 low pressure heater will open.If the water level of the No.3 low-pressure is too high,the heating surface will be submerged,the heat transfer area with steam will be reduced,the heat transfer effect will be reduced and the steam can not be condensed in time.At the same time,the accident drainage is discharged into the emergency drainage tank and finally enters the condenser,which increases the“cold source loss”and affects the operating efficiency of the unit.The high water level of No.3 low-pressure heater may cause trips of No.3 and No.4low-pressure heaters even water inflow into the steam turbine,causing water impact.Based on the consultation of the historical curves and the qualitative analysis of the operating conditions before and after the replacement of the electric pump with the steam pump,this paper analyzes possible causes of the abnormal opening of the emergency drainage valve of the No.3low-pressure heater.The overhauling and operating measures are optimized to ensure the safe and stable operation of the unit.