| Abstract: | It is important to examine characteristics of ash in order to understand the high temperature corrosion behavior of steels in the black liquor recovery boiler (BLRB) environment. The ash collected from the corroded superheater tubes was mainly composed of alkali-sulfates, alkali-chlorides and alkali-carbonates. The mole ratio of Na/K in the ash from BLRB ranged from 3 to 17. The concentration of sulfates varied over a range from 50 to 90 wt%, and chlorides from 0.1 to 10 wt%. On the base of these results, the corrosion behavior of various steels and the effect of alloying elements on the corrosion behavior of stainless steels in the BLRB environment were studied. From the results, Cr, Mn and Mo were significantly beneficial elements. N and Ni were also beneficial above 600 °C while C was an extremely harmful element. Subsequently, a new corrosion resistant stainless steel was selected as the material for the superheater in the BLRB. |
