Fireside corrosion of superheater materials in chlorine containing flue gas

Corrosion resistance of three types of candidate materials for superheater sections under simulated waste incineration conditions was evaluated. A 9Cr1Mo steel, an AISI MOSS, and the Ni-based alloy Sanicro 28 were tested on a laboratory and on a pilot scale with different flue gas compositions (up to 2500 mg/Nm(3) of HCl and 1500 mg/Nm(3) of fly ash). Laboratory tests were carried out in a furnace up to 200 h. Metal and gas temperature were kept constant at 500 degreesC. Pilot scale tests were carried out by using a 0.3 X 0.3 m cross-sectional combustor, with flue gas velocity of 5 m/s. Air-cooled probes, designed to operate at a metal temperature of 500 degreesC and facing gas temperatures as high as 600 degreesC, were used for 200 h as maximum test time. Qualitative correspondence was found between results obtained by the two sets of experimental tests, but quantitative values were not comparable. Metallographic evaluations, metal loss measurements, and weight loss analysis evidenced as the most suitable alloy Sanicro28. Maximum metal loss observed was 240, 182, and 107 mum, respectively, for 9Cr1Mo, AISI310SS, and Sanicro 28 under the most aggressive conditions. Intergranular corrosion attack was evidenced for AlSI310SS, limiting the choice of materials to 9Cr1Mo and Sanicro 28, depending upon the lifetime expected at the design stage.