Fireside corrosion in kraft recovery boilers is a continuing problem in the pulp and paper industry, especially in the boilers using carbon steel tubes in lower furnace areas. Certain areas in the lower furnace of kraft recovery boilers consistently have higher corrosion rates than the nearby areas. As the tube material in these areas is the same, differences in the corrosion rate suggest that the local environmental conditions in the two areas are different. Corrosive environments were characterized in a
kraft recovery boiler, which had well-defined areas with high corrosion rates and low corrosion rates. Three important variables, tube surface temperature, gas composition at the waterwall surface, and smelt composition were monitored in the selected areas. Recovery boiler gases were analyzed using an on-line gas chromatograph. Waterwall temperature and smelt did not have any effect on differences in the corrosion rate in the two areas. Gas compositions were found to play a
predominant role in corrosion behavior differences in the lower furnace of kraft recovery boilers. Results from this work have shown that the local environments can be very different at the waterwall surfaces in a given general area leading to differences in the local corrosion rates.