Scientific Investigation of Corrosion—Perforation in Desulfurized Flue Gas Heat Exchanger Tubes: Numerical and Experimental Studies

To clarify the causes of corrosion perforation in the tube bundle of the flue gas desulfurization (FGD) heat exchanger, research was performed on the failed tube bundle. Through material analysis, the possibility of failure caused by defects in the heat-exchange tubes themselves was excluded. By means of scanning electron microscopy, energy dispersive spectroscope, and x-ray diffraction surface analysis, it was found that the corrosion was related to acidic media and insufficient molybdenum content in the material. Through numerical simulation, it was discovered that the low-temperature zone near the upper tube sheet was prone to the condensation of acidic media, and the low-velocity zone in the upper part of the tube bundle would retain corrosive media. The two, together with flue gas scouring and vibration, triggered corrosion perforation. Accordingly, optimization schemes for materials, operation, and protection were proposed.