Time- and temperature-dependence of the anticorrosion effect of sodium sulfide on Q235 steel for post-combustion CO2 capture system
By Emori, Wilfred; Jiang, Shengli; Okonkwo, Paul C.; Duan, Song; Zheng, Yugui
Published in Results in Chemistry
2022
Abstract
As a heat stable salt, sodium sulfide remains thermally-unregenerable during the regeneration process for post-combustion capture. Therefore, it became important to undertake a full assessment of its potential presence in the system. The paper investigates the mechanism and influence of sodium sulfide on the corrosion behavior of Q235 steel in amine-based post-combustion CO2 capture technology with respect to exposure time and temperature. The inhibitive influence of sulfide in the system was first confirmed by electrochemical techniques, while gravimetry was used to evaluate the effect of time and temperature on the inhibitive actions. SEM/EDX and XPS were used to characterize the corrosion product films on the steel surface. The behavior of sulfide was largely dependent on its concentration as its inhibition ability decreased with increasing concentration, and this is credited to the presence of FeS corrosion film layer. Time-dependent corrosion studies of steel conducted at 50 °C for the solution with 0.05 M and 0.1 M sulfide showed that the inhibition efficiency decreased from 89.1% and 75.0% to 82.4% and 68.6%, respectively, after 7 and 14 days immersion. At 80 °C, the inhibition efficiency of 0.05 M sulfide decreased from 89.1% to 48.9% after 7 days immersion and 82.4% to 46.1% after 14 days immersion. Together with FeS layer, FeCO3, Fe2O3 were also confirmed on the steel surface by XPS measurement. The research provides practical information on the influence of sulfide in the absorber and rich-lean heat exchanger sections of a CO2 capture unit.