SCR脱硝副产物硫酸氢铵对锅炉尾部金属材料的腐蚀特性研究

Corrosion Characteristics of Downstream Metal Material of Boiler System in Solution of By-product Ammonium Bisulfate from SCR Denitrification

通过失重法研究了锅炉尾部材料碳钢和不锈钢在ABS(硫酸氢铵)和H_2SO_4两种溶液中的腐蚀行为,利用动电位极化曲线分析腐蚀特性。采用SEM/EDS和XPS表征手段分析了腐蚀产物表层的形貌和元素组成以及化合态。结果表明:不锈钢对ABS有更好的耐蚀性,且随着ABS溶液浓度的增大,腐蚀变剧烈。腐蚀产物的种类有Fe_2O_3,FeOOH,Fe_3O_4和铁的硫酸盐。碳钢和不锈钢在等浓度的ABS和硫酸溶液中腐蚀过程相似,说明ABS具有很强的腐蚀性。腐蚀机理为碳钢表面首先发生酸性腐蚀,H+作为去极化剂,有H_2析出。随着酸度的消耗,金属表面会发生氧腐蚀,溶解氧作为去极化剂。Fe^(2+)接着被进一步氧化为Fe^(3+),再发生一系列的次生反应,生成Fe的氧化物以及硫酸盐等。

The corrosion behavior of the boiler tail material which is made of carbon steel and stain- less steel in solutions of ammonium bisulfate （ABS） and H2SO4 respectively was studied by means of mass loss measurement and potentiodynamic polarization curve as well as SEM/EDS and XPS. The results showed that： stainless steel has better corrosion resistance to ABS, and with the in- crease of ABS solution concentration, corrosion becomes more intensive. The corrosion products consist of Fe2O3, FeOOH, Fe3O4, iron sulfate and a small amount of iron carbon oxide. The corro- sion process of carbon steel and stainless steel is similar in the solutions with the same concentration of ABS and sulfuric acid. It can be concluded that ABS has stronger corrosivity. The corrosion mechanism is that hydrogen depolarization first may occur during the corrosion of carbon steel, and then generate hydrogen. As the acid consumption, as well as the effect of dissolved oxygen in the solution, the oxygen depolarization corrosion will happen on metal surface, Fe2＋ is then further oxidized to Fe3＋, produces a series of secondary reaction, to generate iron oxide and sulfate, etc.