Corrosion Investigation and Materials Selection for Cost-effective Construction of Flue Gas Systems in Advanced Pressurized Oxy-fuel Combustion Power Plant

摘要

Oxy-fired Pressurized Fluidized Bed Combustion (Oxy-PFBC) is a very promising power generation technology as it can use coal as fuel for electricity generation while capturing CO_2 and other greenhouse gases at a significantly low cost compared to the current state of existing post-combustion capture technologies. In pilot scale Oxy-PFBC power plants, a flue gas tube system is designed to operate in an environment with specific gas chemistry different from those in traditional coal-fired power plants. Little work has been conducted to study the materials performing under such unique conditions, making cost-effective selection of construction materials difficult. Two types of corrosion can occur on flue gas tube surfaces, including gas phase corrosion and condensed phase corrosion at temperatures lower than the flue gas dew point. In this article, both hog gas corrosion and condensed phase corrosion of the candidate alloys, such as typical duplex steels, stainless steels and Ni-based alloys, were systemically investigated by carrying our ASTM standard immersion tests, electrochemical measurements (linear polarization, impedance, and noise, etc.), static autoclave tests and post-mortem microscopy characterization of corrosion products. The results show that pitting corrosion took place on all the candidate alloys in the simulated condensed phase of the flue gas. Inclusions acted as the initiation sites for the pitting, but the depth of pit holes did not increase with prolonged immersion time. In hot gas corrosion tests, weight gain measurement and analysis on the surface oxide layer helped to identify the corrosion kinetics of the candidate alloys. The corrosion resistances of all the candidate alloys were evaluated and several alloys were recommended for the construction of the flue gas system.