Recovery boiler superheater corrosion field study

With the trend towards increasing the energy efficiency of black liquor recovery boilers in North America, there is a need to utilize superheater tubes with increased corrosion resistance that will permit operation at higher temperatures and pressures. In an effort to identify alloys with improved corrosion resistance under more harsh operating conditions, a field exposure was conducted that involved the insertion of an air-cooled probe, containing six candidate alloys, into the superheater section of an operating recovery boiler. A metallographic examination, complete with corrosion scale characterization using electron microprobe spectroscopy, was conducted after a 1,000 hour exposure period. Based on the results, a ranking of alloys based on corrosion performance was obtained.