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

Abstract

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 Fe2O3 and Fe3O4; the main corrosion products during SRB process were iron oxide and iron sulfide; When SRB+IOB coexisted, the main corrosion products were Fe2O3, Fe3O4 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.

Keywords

• regenerated water from thermal power plants; sulfate reducing bacteria; iron bacteria; electrochemistry; microbial; corrosion