Comprehensive Analysis Of The Oxide-Scale Exfoliation In Large Capacity Boiler Of Power Plant

With the fast development of power construction of our country, newly-built units gradually orient to large capacity and high parameters. Super-critical and super-super-critical units will become leading power units in our country. However, parameters of units become higher, oxide-scale issue will bring about more outstanding effects on operation of boiler and turbine.This article presents a comprehensive analysis on issue of oxide-scale on boiler metal heating surface, and mainly covers formation mechanism of oxide-scale, effecting factors of exfoliation of oxide-scale, effects on operation of boiler and turbine arising from exfoliation of oxide-scale and how to prevent the SPE (solid particle erosion) problem of turbine throughout part from exfoliation of oxide-scale, etc.This article, based on exfoliation of oxide-scale of the boiler of Yangzhou NO.2 power plant, conducts a comprehensive analysis on reasons of over-temperature of superheater and reheater, and provides an improved plan on resolving over-temperature problem. But, based on the analysis of the the oxide-scale thickness, it found that the thickness of the oxide-scale is not the conclusive factor that causes oxide-scale produces exfoliation. In addition, based on analysis conducted on variation of main steam temperature in the process of units'startup, it is found that main steam temperature and superheater tube temperature vary too fast when attemperating water is put into operation at low load during startup, this is the conclusive factor that causes oxide-scale produces exfoliation during startup. To solve this issue, startup procedures of units are optimized, which include oil burners are put into service and pulverizing system is postponed to be put into service and units start up with bypass system. After the above measures are taken, main steam temperature obviously varies slowly during units'startup.Based on combustion adjustment, over-temperature of heating surface relieved through technology improvement and optimization of startup procedures, boiler tube failure due to exfoliation of oxide-scale is eliminated and safe and stable operation of units are assured.