超临界机组加氧处理对氧化皮生成和剥离的影响

INFLUENCE OF OXYGEN TREATMENT FOR SUPERCRITICAL UNITS UPON FORMATION AND PEEL-OFF OF OXIDE SKIN

国华盘山发电有限责任公司1号、2号机组给水采用加氧处理,累计运行时间长达10年未发生过因氧化皮脱落引起的堵管、爆管事故。对这2台机组锅炉过热器和再热器的氧化膜及氧化皮生成情况进行检查,发现差别较大。通过分析,找出了氧化皮产生及剥离的原因:(1)氧化皮是金属在高温水汽中发生氧化的结果,氧化所消耗的氧来源于水汽本身,而非溶解在水汽中的分子氧,也即给水加氧对氧化皮的生成影响不大;(2)再热器管的氧化皮有一定程度的剥离,主要与锅炉燃烧工况、机组起停时温度升降速率以及所用材质等因素有关。同时,给出了防止氧化皮产生的措施。

The feed water of unit no.1 and unit no.2 in Guohua Panshan Power Generation Co Ltd has adopted oxygen treatment,the accumulated operation time has reached ten years,the failures of tube-blockage and tube-burst have never occurred due to oxide skin peel-off.It has discovered during inspection of xoxide film and oxdie skin formed on superheater and reheater of boilers for said units that there is greater difference between them.For this,the causes leading to formation of oxide skin have been studied,results show that：（1）the oxide skin was the oxidation result of metal in high-temperature water and steam,and it wasn＇t originated from dissolution of molecular oxygen in the water and steam,that is to say the oxygen treatment of feed water had little influence upon formation of oxide skin;（2）certain oxide skin on reheater tube had peeled off,this was mainly related to factors,such as combustion conditions in the boiler,temperature rising and dropping speed during start-up and shutdown of the units,as well as quality of materials used etc.,and measures for preventing formation of oxide skin have been given.