电站低温给水系统腐蚀产物生成过程研究

燃煤电站汽水系统中低温给水部件由于流动加速腐蚀产生大量腐蚀产物，这些腐蚀产物随工质在整个汽水系统中迁徙，严重影响了机组的运行安全及寿命。基于质量平衡方程，建立了腐蚀产物的生成模型，从3种不同角度分析了金属氧化层孔隙率、铁在工质中的扩散系数和工质pH值等对腐蚀速率的影响。结果显示：腐蚀速率分别与前两者成正比关系，而与工质的pH值成反比关系。给水加氧处理可使金属氧化膜的孔隙率明显降低，而管道布置越复杂、管道表面越粗糙，铁在工质中的扩散系数越大。因此，燃煤电站在实际运行中，可通过管道结构优化，选择最佳给水处理方式，在最佳pH值和溶氧量条件下抑制流动加速腐蚀，减少腐蚀产物的产生。

Formulation of Corrosion Products in Low Temperature Feedwater Drain of Power Plant

Originated from carbon steels in feedwater drain due to flow accelerated corrosion, the corrosion products may be transported everywhere throughout the entire steam-water system, which can seriously impact the operation security and lifespan of thermal unit. The generation model of corrosion product in feedwater drain is built based on the mass balance. Then the effect of three main factors on generation process is analyzed, i.e., porosity of oxide layer, diffusivity of iron in the fluid and fluid pH value. The result data shows the corrosion rate is proportional to the former two items, but inversely proportional to the fluid pH. The porosity of oxide layer can be reduced significantly by virtue of oxygenated treatment. However, the more complicated of pipeline arrangement and the rougher of the pipeline surface, the greater of diffusivity will be reached in the fluid. In actual operation of power plant, the formulation of corrosion products can be effectively reduced by restraining the flow accelerated corrosion in combination with the optimization of pipeline structure and water treatment under the condition of optimum pH and dissolved oxygen.