Influence of surface condition on the high-temperature corrosion of 12Cr1MoVG, T91, and TP347H steels in waste-to-energy boilers

High-temperature corrosion of superheater and reheater is a major obstacle for improving steam parameter of waste-fired boiler. In the present study, three commercial alloys (12Cr1MoVG, T91 and TP347H) were investigated under a simulated atmosphere. The anti-corrosion performance of Inconel 625 overlay weld coating on 12Cr1MoVG was also investigated in a real waste-to-energy (WtE) plant. The experiments were carried out by a two-zone lab-scale tube furnace where the gas temperature was 600℃ and the sample temperature was 380℃. Different sample surface conditions of the corrosion test specimens were set up includes clean surface, NaCl/KCl deposition, and ash deposition. Corrosion kinetics were plotted on the basis of specimens weight gain. The results showed that chloride salts are the main corrosive species in ash deposit. The corrosion rate of different deposits and clean surface was in the following order: KCl/NaCl > ash deposit > clean surface. The corrosion products were Fe2O3, Cr2O3, Fe3O4, NiO, (Fe, Ni)Cr2O4, FeCl2, and FeCl3. The presence of chromium was beneficial for high-temperature corrosion resistance. The anti-corrosion performance of the three alloys in descending order was TP347H > T91 > 12Cr1MoVG. This is consistent with the chromium and nickel content in the alloys. The engineering investigation showed that Inconel 625 overlay weld coating can effectively protect base material from the attack of corrosion species includes ash deposit and MSW incineration atmosphere, for long-term in real WtE plant.