超临界机组发生FAC的因素及相互关系分析

Analysis of the Factors of FAC and their Interactions in Supercritical Units

为了减轻因流动加速腐蚀(FAC)引起的锅炉结垢加速、汽水系统管道厚度减小甚至爆裂现象,对超临界机组发生流动加速腐蚀的机理及其主要影响因素进行了研究,并讨论了管壁内表面粗糙度、蒸汽含汽率、pH值、溶氧量对FAC的影响,以及温度与pH值、温度与流速、pH值与溶解氧量、溶解氧量与氢电导率等影响因素之间的相互作用关系,最后结合实际电厂的运行数据验证了分析结果。研究表明:减小工质流速、管壁粗糙度和氢电导率,增大给水的pH值和溶解氧含量可以使FAC的腐蚀速率减小,超临界加氧处理时pH值应在8.9~9.2之间,溶解氧量范围为45~100μg/L,氢电导率的期望值在0.1μS/cm以下。由于各影响因素之间的作用十分复杂,本文只给出了大致范围和趋势,并未给出准确数据。

Flow accelerated corrosion(FAC)can cause faster boiler scale formation,less pipe thickness of steam water system and even higher burst frequency.In order to reduce these phenomena,the mechanism of FAC in supercritical units and its main factors are studied,including the effects of pipe innersurface roughness,steam content,pH value and dissolved oxygen on FAC,as well as the interactions between temperature and pH value,temperature and flow rate,pH value and dissolved oxygen,and dissolved oxygen and hydrogen conductivity.The operation data of supercritical power plant is used to verify the results.The results show that the corrosion rate of FAC can be reduced by reducing the flow rate of working medium,the roughness of pipe wall and the conductivity of hydrogen,increasing the pH value and the content of dissolved oxygen of feed water.The optimum pH range in supercritical oxygenation treatment is 8.9 to 9.2,the dissolved oxygen is 45 to 100μg/L and the expected value of hydrogen conductivity is less than 0.1μS/cm.Due to the complexity of the interactions,only general range and trend with no accurate data is provided.