660MW超超临界锅炉再热抽汽安全性分析

Safety Analysis on Reheated Steam Extraction Steam at 660MW Ultra-Supercritical Boiler

某电厂660 MW超超临界锅炉为单炉膛П型布置,尾部烟气挡板调节再热汽温。机组运行后拟抽取再热蒸汽满足外部供热。锅炉受热面布置按照不抽汽设计,假如抽汽运行,随着再热流量降低,再热器受热面冷却能力不足易超温影响机组安全运行。通过对660MW额定工况、75%负荷和50%负荷工况下不同抽汽量的计算对比,分析了机组负荷和抽汽量变化关系、比较了再热器受热面最高管壁温度和管子材料许用温度,对不同工况下锅炉的最大可能抽汽量进行预估。通过计算对比结果表明对机组再热系统的抽汽改造方案选择具有一定指导意义。

A power plant is designed with 660 MW ultra-supercritical typeΠboiler,single furnace,and flue gas damper control reheat steam temperature at rear pass.After the operation the unit is proposed to extract reheated steam to meet the requirements on the external heating parameters.The heating surface is designed without extraction,and when the unit operates with extraction,the cooling flow of RH heating surface is reduced,RH will be overheated which affects the safe operation of the unit.Based on calculation comparison under the conditions of different extraction quantities for 660 MW rated condition,75% and 50%load conditions,the trend of the load to the extraction quantity is analyzed,the conclusion that the maximum extraction quantity is determined by the tube wall temperature at the outlet of low temperature reheater is gotten,and the possibly maximum extraction steam quantities under different cases are forecasted.These calculations and results have a guidance on selection of the retrofit plan for the extraction system.