Corrosion of Bed Nozzle Alloys in a Wood-Waste Fluidized Bed Power Boiler

A field test was conducted to identify a more corrosion-resistant material than Type 310H (UNS S31009) stainless steel, from which to fabricate bed nozzles for a fluidized bed power boiler that burns salt-laden wood-waste (hogged) fuel. Test nozzles fabricated from Type 310H stainless steel, Alloys 556 (UNS R30556), 59 (UNS N06059), HR160 (UNS N12160), and 625 (UNS N06625) were installed, subsequently removed, and examined as a function of time. Of the various alloys tested, Alloys 625 and HR160 had the best performance in terms of the amount of thickness loss, and the extent of internal damage exhibited. However, those alloys were still susceptible to corrosion by the fireside (fluidized bed) environment and, therefore, will require replacement over time. Despite the observed corrosion, those two alloys significantly extended the nozzle life beyond that of Type 310H stainless steel. Nozzle design was found to have a strong influence on the apparent corrosion resistance of Alloy 625 and, therefore, represents a promising preventive solution possibility. The reason for the marked improvement remains unresolved at this time.