HIGH-TEMPERATURE CORROSION OF WATER WALL TUBE IN COALFIRED COMBUSTION GASES

The effect of stoichiometry ratio and ash deposits on the corrosion of mild steel and 0.5Cr-0.5Mo steel has been investigated at 450-degrees-C in the simulated combustion gases burning three kinds of coals. Under the assumption that the gas reacts with the metal at the same temperature as the surface and gas has not changed in composition, the corrosion behavior could be estimated from the Fe-S-O phase stability diagram at 450-degrees-C and pseudo equilibrium P(s2) and P(O2) based on H2O : H-2 at 1200-degrees-C for simulated combustion gases. Ash deposits accelerated the corrosion rates of steels. It is considered that ash deposits act as catalyst and shift the gas composition to the low temperature equilibrium state.