火电厂再生水中的微生物对管道的腐蚀行为研究

Effect of Microbes in Regenerated Water of Thermal Power Plant on the Corrosion Behavior of Pipelines

为探究火电厂以再生水为水源时供水管道的微生物腐蚀行为,采用环状生物膜挂片反应器,动态模拟了再生水管道运行状况,通过测定溶液pH值、电导率,试片失重,电化学参数(如氧化还原电位、极化曲线、交流阻抗)、细菌数量并结合SEM、EDS、XRD等手段研究了铁细菌(IOB)、硫酸盐还原菌(SRB)及这2种混合菌对Q235钢腐蚀的影响过程和机理。结果表明,2种细菌数量随时间的延长而增长,再生水的pH值先降后升、电导率则稳步增长,环境中的细菌数与此时管材的腐蚀速率呈正相关性,SRB是影响微生物腐蚀的主要菌种;通过EDS和XRD分析发现不同环境下的腐蚀产物主要成分:IOB时腐蚀产物以FeOOH为主,存在少量Fe_(2)O_(3)、Fe_(3)O_(4);SRB时腐蚀产物主要为氧化铁和硫化铁;而SRB+IOB共存时主要腐蚀产物为Fe_(2)O_(3)、Fe_(3)O_(4)和FeS;同时管道前期表面产生的微生物膜和腐蚀产物会抑制Q235的腐蚀,后期微生物膜失活、覆盖的腐蚀产物脱落,又会使腐蚀加速。

For investigating the microbial corrosion behavior of water supply pipelines in thermal power plants using regenerated water as the water source,a circular biofilm hanging plate reactor was used to dynamically simulate the operation status of the regenerated water pipeline.The influence process and mechanism of iron bacteria(IOB),sulfate reducing bacteria(SRB)and their mixture on the corrosion of Q235 steel were studied by measuring the pH value and conductivity of the solution,weight loss of the specimen,electrochemical parameters(such as redox potential,polarization curve,AC impedance),bacterial count,and combining SEM,EDS,XRD and other methods.Results showed that the number of two types of bacteria increased over time,and the pH value of the regenerated water first decreased and then increased,while the conductivity steadily increased.Furthermore,the number of bacteria in the environment was positively correlated with the corrosion rate of pipes at this time,and SRB were the main bacterial species that affected microbial corrosion.Through EDS and XRD analysis,it was found that the main components of corrosion products varied in different environments:the corrosion products during IOB process were mainly FeOOH,with a small amount of Fe_(2)O_(3) and Fe_(3)O_(4);the main corrosion products during SRB process were iron oxide and iron sulfide;When SRB+IOB coexisted,the main corrosion products were Fe_(2)O_(3),Fe_(3)O_(4) and FeS.Besides,the microbial film and corrosion products generated on the surface of the pipeline in the early stage would inhibit the corrosion of Q235.In the later stage,the deactivation of the microbial film and the detachment of the covered corrosion products would accelerate the corrosion.